Author name code: lamy ADS astronomy entries on 2022-09-14 author:Lamy, P.L. ------------------------------------------------------------------------ Title: Linking Small-scale Solar Wind Properties with Large-scale Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar Orbiter Observations Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca; D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto; Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru; Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen, Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone, Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale, Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit, Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.; Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli, Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco, Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati, Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli, Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio; Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli, Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère, Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella, Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco; Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki, Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial, Jean-Claude; Woch, Joachim; Zimbardo, Gaetano Bibcode: 2022ApJ...935..112T Altcode: The solar wind measured in situ by Parker Solar Probe in the very inner heliosphere is studied in combination with the remote-sensing observation of the coronal source region provided by the METIS coronagraph aboard Solar Orbiter. The coronal outflows observed near the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and 6.3 R ⊙ above the eastern solar limb, can be associated with the streams sampled by PSP at 0.11 and 0.26 au from the Sun, in two time intervals almost 5 days apart. The two plasma flows come from two distinct source regions, characterized by different magnetic field polarity and intensity at the coronal base. It follows that both the global and local properties of the two streams are different. Specifically, the solar wind emanating from the stronger magnetic field region has a lower bulk flux density, as expected, and is in a state of well-developed Alfvénic turbulence, with low intermittency. This is interpreted in terms of slab turbulence in the context of nearly incompressible magnetohydrodynamics. Conversely, the highly intermittent and poorly developed turbulent behavior of the solar wind from the weaker magnetic field region is presumably due to large magnetic deflections most likely attributed to the presence of switchbacks of interchange reconnection origin. Title: Science with the ASPIICS coronagraph onboard PROBA-3 Authors: Gunár, Stanislav; Fineschi, Silvano; Inhester, Bernd; Zhukov, Andrei; Mierla, Marilena; Tsinganos, Kanaris; Lamy, Philippe; Rudawy, Pawel Bibcode: 2022cosp...44.1326G Altcode: The giant distributed coronagraph ASPIICS onboard the formation-flying mission PROBA-3 of ESA will investigate hitherto practically unexplored inner depths of the solar corona. This region lies above the reach of disk imagers such as SDO and below the inner limit of other coronagraphs. Although difficult to observe, the inner corona is a place of great interest. This is where the fast solar wind gets accelerated to supersonic velocities and where CMEs also reach their maximum accelerations. It is also the place where the transition between the regions of the closed and open magnetic field often happens and the slow solar wind originates. Thanks to its field of view (2048 x 2048 pixels) reaching from 1.098 to 3 Rsun, good spatial resolution (2.8 arcsec per pixel) and minimized straylight, ASPIICS will be able to follow the connectivity of magnetic structures in corona down to the solar surface. When coupled with regular (every week) long duration (up to 6 hours) observations, it will allow us to comprehensively compare and validate the MHD models of the large-scale coronal magnetic field configuration and its evolution. The inner field-of-view limit reaching very close to the solar surface will also enable us to study the onset and early evolution of CMEs or to follow erupting prominences beyond the reaches of the disk imagers. Thanks to the high cadence (up to 2 seconds) we can start to investigate the manifestation of small-scale solar dynamic processes within the inner corona. Moreover, together with the DARA instrument measuring the total solar irradiance onboard the occulting spacecraft of PROBA-3, ASPIICS will help us to understand the partition of the magnetic free energy into the radiative energy and the kinetic energy during solar eruptions. The pursuit of these science goals will happen in coordination with Solar Orbiter, Parker Solar Probe, Aditya-L1, and ASO-S. The synergies stemming from these collaborations are promising to lead us into a golden age of space coronagraphy. Title: Polarimetric Studies of a Fast Coronal Mass Ejection Authors: Mierla, Marilena; Inhester, Bernd; Zhukov, Andrei N.; Shestov, Sergei V.; Bemporad, Alessandro; Lamy, Philippe; Koutchmy, Serge Bibcode: 2022SoPh..297...78M Altcode: 2022arXiv220604411M In this work we performed a polarimetric study of a fast and wide coronal mass ejection (CME) observed on 12 July 2012 by the COR1 and COR2 instruments onboard the Solar TErrestrial RElations Observatory (STEREO) mission. The CME source region was an X1.4 flare located at approximately S15W01 on the solar disk, as observed from the Earth's perspective. The position of the CME as derived from the 3D Graduated Cylindrical Shell (GCS) reconstruction method was at around S18W00 at 2.5 solar radii and S07W00 at 5.7 solar radii, meaning that the CME was deflected towards the Equator while propagating outward in the corona. The projected speed of the leading edge of the CME also evolved from around 200 km s−1 in the lower corona to around 1000 km s−1 in the COR2 field of view. The degree of polarisation of the CME is around 65% but it can go as high as 80% in some CME regions. The CME showed deviation of the polarisation angle from the tangential in the range of 10 - 15∘ (or more). Our analysis showed that this is mostly due to the fact that the sequence of three polarised images from where the polarised parameters are derived is not taken simultaneously, but at a difference of a few seconds in time. In this interval of time, the CME moves by at least two pixels in the FOV of the instruments and this displacement results in uncertainties in the polarisation parameters (degree of polarisation, polarisation angle, etc.). We propose some steps forward to improve the derivation of the polarisation. This study is important for analysing the future data from instruments with polarisation capabilities. Title: Three-Dimensional Structure of the Corona During WHPI Campaign Rotations CR-2219 and CR-2223 Authors: Lloveras, D. G.; Vásquez, A. M.; Nuevo, F. A.; Frazin, R. A.; Manchester, W.; Sachdeva, N.; Van der Holst, B.; Lamy, P.; Gilardy, H. Bibcode: 2022JGRA..12730406L Altcode: Differential emission measure tomography (DEMT) and white light (WL) tomography were applied to study the three-dimensional (3D) structure of the global solar corona for two Whole Heliosphere and Planetary Interactions campaign periods, Carrington rotations 2219 and 2223. With DEMT, Solar Dynamics Observatory/Atmospheric Imaging Assembly images were used to reconstruct the 3D coronal electron density and temperature in the range of heliocentric distance 1.02-1.25 R⊙. With WL tomography, Solar and Heliospheric Observatory/Large Angle and Spectrometric COronagraph-C2 images were used to reconstruct the 3D electron density in the range of heliocentric distance 2.5-6.0 R⊙. The two periods were also simulated with the 3D-magneto-hydrodynamic Alfvén Wave Solar Model (AWSoM), and its results compared in detail with the reconstructions. The DEMT analysis reveals a 20% less dense and 20% hotter corona than for rotations corresponding to the solar cycle 23/24 deep minimum. The electron density and temperature of the AWSoM model agree with DEMT results within 10% and 20%, respectively, while its electron density overestimates results of WL tomography up to 75%. The slow (fast) component of the terminal wind speed of the model is found to be associated with field lines characterized by larger (smaller) values of the tomographic density and temperature at the coronal base. DEMT reconstructions reveal the coronal plasma to be ubiquitously characterized by temperature variability of up to ≈45% over spatial scales of order ∼104 km. Taking into account this level of fine-structure by global models may be consequential for their predictions on wave propagation in the corona. Title: M-type (22) Kalliope: A tiny Mercury Authors: Ferrais, M.; Jorda, L.; Vernazza, P.; Carry, B.; Brož, M.; Rambaux, N.; Hanuš, J.; Dudziński, G.; Bartczak, P.; Vachier, F.; Aristidi, E.; Beck, P.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.; Burbine, T. H.; Dyar, M. D.; Bendjoya, P.; Benkhaldoun, Z.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Ďurech, J.; Fauvaud, S.; Grice, J.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Prieur, J. -L.; Reddy, V.; Rivet, J. -P.; Santana-Ros, T.; Scardia, M.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2022A&A...662A..71F Altcode: Context. Asteroid (22) Kalliope is the second largest M-type asteroid in the main belt and is orbited by a satellite, Linus. Whereas the mass of Kalliope is already well constrained thanks to the presence of a moon, its volume is still poorly known, leading to uncertainties on its bulk density and internal structure.
Aims: We aim to refine the shape of (22) Kalliope and thus its diameter and bulk density, as well as the orbit of its moon to better constrain its mass, hence density and internal structure.
Methods: We acquired disk-resolved observations of (22) Kalliope using the VLT/SPHERE/ZIMPOL instrument to reconstruct its three-dimensional (3D) shape using three different modeling techniques. These images were also used together with new speckle observations at the C2PU/PISCO instrument as well as archival images from other large ground-based telescopes to refine the orbit of Linus.
Results: The volume of (22) Kalliope given by the shape models, corresponding to D = 150 ± 5 km, and the mass constrained by its satellite's orbit yield a density of ρ = 4.40 ± 0.46 g cm−3. This high density potentially makes (22) Kalliope the densest known small body in the Solar System. A macroporosity in the 10-25% range (as expected for this mass and size), implies a grain density in the 4.8-5.9 g cm−3 range. Kalliope's high bulk density, along with its silicate-rich surface implied by its low radar albedo, implies a differentiated interior with metal contributing to most of the mass of the body.
Conclusions: Kalliope's high metal content (40-60%) along with its metal-poor mantle makes it the smallest known Mercury-like body. A large impact at the origin of the formation of the moon Linus is likely the cause of its high metal content and density.

Reduced images are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/662/A71

Based on observations made with ESO Telescopes at the Paranal Observatory under program ID 199.C-0074 (PI: P. Vernazza). Title: The State of the White-Light Corona over the Minimum and Ascending Phases of Solar Cycle 25 -- Comparison with Past Cycles Authors: Lamy, Philippe; Gilardy, Hugo Bibcode: 2022arXiv220506462L Altcode: We report on the state of the corona over the minimum and ascending phases of Solar Cycle (SC) 25 on the basis of the temporal evolutions of its radiance and of the properties of coronal mass ejections (CMEs) as determined from white-light observations performed by the SOHO/LASCO-C2 coronagraph. These evolutions are further compared with those determined during the past two SC. The integrated radiance of the K-corona and the occurrence rate of CMEs closely track the indices/proxies of solar activity, prominently the total magnetic field for the radiance and the radio flux for the CMEs, all undergoing a steep increase during the ascending phase of SC 25. This increase is much steeper than anticipated on the basis of the predicted quasi similarity between SC 25 and 24, and is confirmed by the recent evolution of the sunspot number. The radiance reached the same base level during the minima of SC 24 and 25, but the latitudinal extent of the streamer belt differed, being flatter during the latter minimum and in fact more similar to that of the minimum of SC 23. Phasing the descending branches of SC 23 and 24 led to a duration of SC 24 of 11.0 years, similar to that given by the sunspot number. In contrast, the base level of the occurrence rate of CMEs during the minimum of SC 25 was significantly larger than during the two previous minima. The southern hemisphere is conspicuously more active than the northern one in agreement with several predictions and the current evolution of the hemispheric sunspot numbers. The mean apparent width of CMEs and the number of halo CMEs remains at relatively large, constant levels throughout the early phase of SC 25 implying the persistence of weak total pressure in the heliosphere. These results and the perspective of a corona more active than anticipated are extremely promising for the forthcoming observations by Solar Orbiter and Parker Solar Probe. Title: VizieR Online Data Catalog: (22) Kalliope SPHERE images and shape models (Ferrais+, 2022) Authors: Ferrais, M.; Jorda, L.; Vernazza, P.; Carry, B.; Broz, M.; Rambaux, N.; Hanus, J.; Dudzinski, G.; Bartczak, P.; Vachier, F.; Aristidi, E.; Beck, P.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.; Burbine, T. H.; Dyar, M. D.; Bendjoya, P.; Benkhaldoun, Z.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Durech, J.; Fauvaud, S.; Grice, J.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Prieur, J. -L.; Reddy, V.; Rivet, J. -P.; Santana-Ros, T.; Scardia, M.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2022yCat..36620071F Altcode: We obtained 35 images of Kalliope at 7 epochs in 2018 and 2019 using VLT/SPHERE/ZIMPOL. All images were reduced following the procedure described in Vernazza et al. (2018A&A...618A.154V).

objects: ------------------------------------------------------------------- Planet Name H Diam i e a mag km deg AU ------------------------------------------------------------------- 22 Kalliope 6.53 150 13.700494 0.09838130 2.91020240 -------------------------------------------------------------------

(10 data files). Title: Observation of the Solar F-corona from Space Authors: Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine Bibcode: 2022arXiv220211533L Altcode: We present a review of the observations of the solar F-corona from space with a special emphasis of the 25 years of continuous monitoring achieved by the LASCO-C2 and C3 coronagraphs. Our work includes images obtained by the navigation cameras of the Clementine spacecraft, the SECCHI/HI-1A heliospheric imager onboard STEREO-A, and the Wide Field Imager for Solar Probe onboard the Parker Solar Probe. The connection to the zodiacal light is considered based on ground- and space-based observations, prominently from the past Helios, IRAS, COBE, and IRAKI missions. The characteristic radiance profiles along the equatorial and polar directions follow power laws in the 5°-50° range of elongation, with constant power exponents of -2.33 and -2.55. Both profiles connect extremely well to the corresponding standard profiles of the zodiacal light. The LASCO equatorial profile exhibits a shoulder implying a 17% decrease of the radiance within 10Rsun that may be explained by the disappearance of organic materials within 0.3 AU. LASCO detected for the first time a secular variation of the F-corona, an increase at a rate of 0.46% per year of the integrated radiance in the LASCO-C3 FoV. This is likely the first observational evidence of the role of collisions in the inner zodiacal cloud. A composite of C2 and C3 images produced the LASCO reference map of the radiance of the F-corona from 2 to 30Rsun and, by combining with ground-based measurements, the LASCO extended map from 1 to 6 Rsun. The plane of symmetry of the inner zodiacal cloud is strongly warped, its inclination increasing towards the planes of the inner planets and ultimately the solar equator. In contrast, its longitude of ascending node is found to be constant and equal to 87.6°. LASCO did not detect any small scale structures such as putative rings occasionally reported during solar eclipses. Title: The first coronal mass ejection observed in both visible-light and UV H I Ly-α channels of the Metis coronagraph on board Solar Orbiter Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini, F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.; Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.; Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki, A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto, P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus, Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G. Bibcode: 2021A&A...656L..14A Altcode: Context. The Metis coronagraph on board Solar Orbiter offers a new view of coronal mass ejections (CMEs), observing them for the first time with simultaneous images acquired with a broad-band filter in the visible-light interval and with a narrow-band filter around the H I Ly-α line at 121.567 nm, the so-called Metis UV channel.
Aims: We show the first Metis observations of a CME, obtained on 16 and 17 January 2021. The event was also observed by the EUI/FSI imager on board Solar Orbiter, as well as by other space-based coronagraphs, such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here with Metis data.
Methods: Different images are analysed here to reconstruct the 3D orientation of the expanding CME flux rope using the graduated cylindrical shell model. This also allows us to identify the possible location of the source region. Measurements of the CME kinematics allow us to quantify the expected Doppler dimming in the Ly-α channel.
Results: Observations show that most CME features seen in the visible-light images are also seen in the Ly-α images, although some features in the latter channel appear more structured than their visible-light counterparts. We estimated the expansion velocity of this event to be below 140 km s−1. Hence, these observations can be understood by assuming that Doppler dimming effects do not strongly reduce the Ly-α emission from the CME. These velocities are comparable with or smaller than the radial velocities inferred from the same data in a similar coronal structure on the east side of the Sun.
Conclusions: The first observations by Metis of a CME demonstrate the capability of the instrument to provide valuable and novel information on the structure and dynamics of these coronal events. Considering also its diagnostics capabilities regarding the conditions of the ambient corona, Metis promises to significantly advance our knowledge of such phenomena.

Movies are available at https://www.aanda.org Title: First light observations of the solar wind in the outer corona with the Metis coronagraph Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini, F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso, C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi, M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.; Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.; Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.; Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère, F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G. Bibcode: 2021A&A...656A..32R Altcode: 2021arXiv210613344R In this work, we present an investigation of the wind in the solar corona that has been initiated by observations of the resonantly scattered ultraviolet emission of the coronal plasma obtained with UVCS-SOHO, designed to measure the wind outflow speed by applying Doppler dimming diagnostics. Metis on Solar Orbiter complements the UVCS spectroscopic observations that were performed during solar activity cycle 23 by simultaneously imaging the polarized visible light and the H I Lyman-α corona in order to obtain high spatial and temporal resolution maps of the outward velocity of the continuously expanding solar atmosphere. The Metis observations, taken on May 15, 2020, provide the first H I Lyman-α images of the extended corona and the first instantaneous map of the speed of the coronal plasma outflows during the minimum of solar activity and allow us to identify the layer where the slow wind flow is observed. The polarized visible light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal emissions, obtained with the two Metis channels, were combined in order to measure the dimming of the UV emission relative to a static corona. This effect is caused by the outward motion of the coronal plasma along the direction of incidence of the chromospheric photons on the coronal neutral hydrogen. The plasma outflow velocity was then derived as a function of the measured Doppler dimming. The static corona UV emission was simulated on the basis of the plasma electron density inferred from the polarized visible light. This study leads to the identification, in the velocity maps of the solar corona, of the high-density layer about ±10° wide, centered on the extension of a quiet equatorial streamer present at the east limb - the coronal origin of the heliospheric current sheet - where the slowest wind flows at about 160 ± 18 km s−1 from 4 R⊙ to 6 R⊙. Beyond the boundaries of the high-density layer, the wind velocity rapidly increases, marking the transition between slow and fast wind in the corona. Title: Sample return of primitive matter from the outer Solar System Authors: Vernazza, P.; Beck, P.; Ruesch, O.; Bischoff, A.; Bonal, L.; Brennecka, G.; Brunetto, R.; Busemann, H.; Carter, J.; Carli, C.; Cartier, C.; Ciarniello, M.; Debaille, V.; Delsanti, A.; D'Hendecourt, L.; Füri, E.; Groussin, O.; Guilbert-Lepoutre, A.; Helbert, J.; Hoppe, P.; Jehin, E.; Jorda, L.; King, A.; Kleine, T.; Lamy, P.; Lasue, J.; Le Guillou, C.; Leroux, H.; Leya, I.; Magna, T.; Marrocchi, Y.; Morlok, A.; Mousis, O.; Palomba, E.; Piani, L.; Quirico, E.; Remusat, L.; Roskosz, M.; Rubin, M.; Russell, S.; Schönbächler, M.; Thomas, N.; Villeneuve, J.; Vinogradoff, V.; Wurz, P.; Zanda, B. Bibcode: 2021ExA...tmp..128V Altcode: The last thirty years of cosmochemistry and planetary science have shown that one major Solar System reservoir is vastly undersampled in the available suite of extra-terrestrial materials, namely small bodies that formed in the outer Solar System (>10 AU). Because various dynamical evolutionary processes have modified their initial orbits (e.g., giant planet migration, resonances), these objects can be found today across the entire Solar System as P/D near-Earth and main-belt asteroids, Jupiter and Neptune Trojans, comets, Centaurs, and small (diameter < 200 km) trans-Neptunian objects. This reservoir is of tremendous interest, as it is recognized as the least processed since the dawn of the Solar System and thus the closest to the starting materials from which the Solar System formed. Some of the next major breakthroughs in planetary science will come from studying outer Solar System samples (volatiles and refractory constituents) in the laboratory. Yet, this can only be achieved by an L-class mission that directly collects and returns to Earth materials from this reservoir. It is thus not surprising that two White Papers advocating a sample return mission of a primitive Solar System small body (ideally a comet) were submitted to ESA in response to its Voyage 2050 call for ideas for future L-class missions in the 2035-2050 time frame. One of these two White Papers is presented in this article. Title: VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis Authors: Vernazza, P.; Ferrais, M.; Jorda, L.; Hanuš, J.; Carry, B.; Marsset, M.; Brož, M.; Fetick, R.; Viikinkoski, M.; Marchis, F.; Vachier, F.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.; Rambaux, N.; Neveu, M.; Bartczak, P.; Dudziński, G.; Jehin, E.; Beck, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Ďurech, J.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.; Antonini, P.; Audejean, M.; Aurard, P.; Behrend, R.; Benkhaldoun, Z.; Bosch, J. M.; Chapman, A.; Dalmon, L.; Fauvaud, S.; Hamanowa, Hiroko; Hamanowa, Hiromi; His, J.; Jones, A.; Kim, D. -H.; Kim, M. -J.; Krajewski, J.; Labrevoir, O.; Leroy, A.; Livet, F.; Molina, D.; Montaigut, R.; Oey, J.; Payre, N.; Reddy, V.; Sabin, P.; Sanchez, A. G.; Socha, L. Bibcode: 2021A&A...654A..56V Altcode: Context. Until recently, the 3D shape, and therefore density (when combining the volume estimate with available mass estimates), and surface topography of the vast majority of the largest (D ≥ 100 km) main-belt asteroids have remained poorly constrained. The improved capabilities of the SPHERE/ZIMPOL instrument have opened new doors into ground-based asteroid exploration.
Aims: To constrain the formation and evolution of a representative sample of large asteroids, we conducted a high-angular-resolution imaging survey of 42 large main-belt asteroids with VLT/SPHERE/ZIMPOL. Our asteroid sample comprises 39 bodies with D ≥ 100 km and in particular most D ≥ 200 km main-belt asteroids (20/23). Furthermore, it nicely reflects the compositional diversity present in the main belt as the sampled bodies belong to the following taxonomic classes: A, B, C, Ch/Cgh, E/M/X, K, P/T, S, and V.
Methods: The SPHERE/ZIMPOL images were first used to reconstruct the 3D shape of all targets with both the ADAM and MPCD reconstruction methods. We subsequently performed a detailed shape analysis and constrained the density of each target using available mass estimates including our own mass estimates in the case of multiple systems.
Results: The analysis of the reconstructed shapes allowed us to identify two families of objects as a function of their diameters, namely "spherical" and "elongated" bodies. A difference in rotation period appears to be the main origin of this bimodality. In addition, all but one object (216 Kleopatra) are located along the Maclaurin sequence with large volatile-rich bodies being the closest to the latter. Our results further reveal that the primaries of most multiple systems possess a rotation period of shorter than 6 h and an elongated shape (c∕a ≤ 0.65). Densities in our sample range from ~1.3 g cm−3 (87 Sylvia) to ~4.3 g cm−3 (22 Kalliope). Furthermore, the density distribution appears to be strongly bimodal with volatile-poor (ρ ≥ 2.7 g cm−3) and volatile-rich (ρ ≤ 2.2 g cm−3) bodies. Finally, our survey along with previous observations provides evidence in support of the possibility that some C-complex bodies could be intrinsically related to IDP-like P- and D-type asteroids, representing different layers of a same body (C: core; P/D: outer shell). We therefore propose that P/ D-types and some C-types may have the same origin in the primordial trans-Neptunian disk.

Tables A.2 and A.3 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/654/A56

Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 199.C-0074 (PI: P. Vernazza).

The reduced and deconvolved images as well as the 3D shape models are available at https://observations.lam.fr/astero/ Title: (216) Kleopatra, a low density critically rotating M-type asteroid Authors: Marchis, F.; Jorda, L.; Vernazza, P.; Brož, M.; Hanuš, J.; Ferrais, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Viikinkoski, M.; Jehin, E.; Benseguane, S.; Podlewska-Gaca, E.; Carry, B.; Drouard, A.; Fauvaud, S.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Fetick, R.; Fusco, T.; Grice, J.; Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2021A&A...653A..57M Altcode: 2021arXiv210807207M Context. The recent estimates of the 3D shape of the M/Xe-type triple asteroid system (216) Kleopatra indicated a density of ~5 g cm−3, which is by far the highest for a small Solar System body. Such a high density implies a high metal content as well as a low porosity which is not easy to reconcile with its peculiar "dumbbell" shape.
Aims: Given the unprecedented angular resolution of the VLT/SPHERE/ZIMPOL camera, here, we aim to constrain the mass (via the characterization of the orbits of the moons) and the shape of (216) Kleopatra with high accuracy, hence its density.
Methods: We combined our new VLT/SPHERE observations of (216) Kleopatra recorded during two apparitions in 2017 and 2018 with archival data from the W. M. Keck Observatory, as well as lightcurve, occultation, and delay-Doppler images, to derive a model of its 3D shape using two different algorithms (ADAM, MPCD). Furthermore, an N-body dynamical model allowed us to retrieve the orbital elements of the two moons as explained in the accompanying paper.
Results: The shape of (216) Kleopatra is very close to an equilibrium dumbbell figure with two lobes and a thick neck. Its volume equivalent diameter (118.75 ± 1.40) km and mass (2.97 ± 0.32) × 1018 kg (i.e., 56% lower than previously reported) imply a bulk density of (3.38 ± 0.50) g cm−3. Such a low density for a supposedly metal-rich body indicates a substantial porosity within the primary. This porous structure along with its near equilibrium shape is compatible with a formation scenario including a giant impact followed by reaccumulation. (216) Kleopatra's current rotation period and dumbbell shape imply that it is in a critically rotating state. The low effective gravity along the equator of the body, together with the equatorial orbits of the moons and possibly rubble-pile structure, opens the possibility that the moons formed via mass shedding.
Conclusions: (216) Kleopatra is a puzzling multiple system due to the unique characteristics of the primary. This system certainly deserves particular attention in the future, with the Extremely Large Telescopes and possibly a dedicated space mission, to decipher its entire formation history.

Reduced images are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/653/A57

Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program 199.C-0074 (PI: Vernazza). Title: VizieR Online Data Catalog: Largest main belt asteroids data (Vernazza+, 2021) Authors: Vernazza, P.; Ferrais, M.; Jorda, L.; Hanua, J.; Carry, B.; Marsset, M.; Broz, M.; Fetick, R.; Viikinkoski, M.; Marchis, F.; Vachier, F.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.; Rambaux, N.; Neveu, M.; Bartczak, P.; Dudzinski, G.; Jehin, E.; Beck, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Durech, J.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B.; Antonini, P.; Audejean, M.; Aurard, P.; Behrend, R.; Benkhaldoun, Z.; Bosch, J. M.; Chapman, A.; Dalmon, L.; Fauvaud, S.; Hamanowa, Hiroko; Hamanowa, Hiromi; His, J.; Jones, A.; Kim, D. -H.; Kim, M. -J.; Krajewski, J.; Labrevoir, O.; Leroy, A.; Livet, F.; Molina, D.; Montaigut, R.; Oey, J.; Payre, N.; Reddy, V.; Sabin, P.; Sanchez, A. G.; Socha, L. Bibcode: 2021yCat..36540056V Altcode: The baseline observational strategy adopted for our large programme has been to image each target with SPHERE/ZIMPOL (i) around opposition to ensure an optimal spatial resolution (we restricted the observing period so that its angular diameter remained greater than at least 85% of that at opposition), (ii) every ~60° in rotation phase in order to obtain a satisfactory surface coverage, and (iii) with seeing conditions of better than 0.8" and an airmass of below 1.6 in order to ensure great observing conditions and thus high-quality data. To fulfil these criteria and given that large programmes have the highest priority at ESO, we performed our large programme entirely in service mode. We would like to stress that this strategy has been key to the success of our programme.

(3 data files). Title: An advanced multipole model for (216) Kleopatra triple system Authors: Brož, M.; Marchis, F.; Jorda, L.; Hanuš, J.; Vernazza, P.; Ferrais, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Viikinkoski, M.; Jehin, E.; Benseguane, S.; Podlewska-Gaca, E.; Carry, B.; Drouard, A.; Fauvaud, S.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Fetick, R.; Fusco, T.; Grice, J.; Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Vokrouhlický, D.; Witasse, O.; Yang, B. Bibcode: 2021A&A...653A..56B Altcode: 2021arXiv210509134B
Aims: To interpret adaptive-optics observations of (216) Kleopatra, we need to describe an evolution of multiple moons orbiting an extremely irregular body and include their mutual interactions. Such orbits are generally non-Keplerian and orbital elements are not constants.
Methods: Consequently, we used a modified N-body integrator, which was significantly extended to include the multipole expansion of the gravitational field up to the order ℓ = 10. Its convergence was verified against the `brute-force' algorithm. We computed the coefficients Cℓm, Sℓm for Kleopatra's shape, assuming a constant bulk density. For Solar System applications, it was also necessary to implement a variable distance and geometry of observations. Our χ2 metric then accounts for the absolute astrometry, the relative astrometry (second moon with respect to the first), angular velocities, and silhouettes, constraining the pole orientation. This allowed us to derive the orbital elements of Kleopatra's two moons.
Results: Using both archival astrometric data and new VLT/SPHERE observations (ESO LP 199.C-0074), we were able to identify the true periods of the moons, P1 = (1.822359 ± 0.004156) d, P2 = (2.745820 ± 0.004820) d. They orbit very close to the 3:2 mean-motion resonance, but their osculating eccentricities are too small compared to other perturbations (multipole, mutual), meaning that regular librations of the critical argument are not present. The resulting mass of Kleopatra, m1 = (1.49 ± 0.16) × 10−12 M⊙ or 2.97 × 1018 kg, is significantly lower than previously thought. An implication explained in the accompanying paper is that (216) Kleopatra is a critically rotating body.

Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program 199.C-0074 (PI Vernazza). Title: VizieR Online Data Catalog: (216) Kleopatra images (Marchis+, 2021) Authors: Marchis, F.; Jorda, L.; Vernazza, P.; Broz, M.; Hanus, J.; Ferrais, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Viikinkoski, M.; Jehin, E.; Benseguane, S.; Podlewska-Gaca, E.; Carry, B.; Drouard, A.; Fauvaud, S.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudzinski, G.; Durech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Fetick, R.; Fusco, T.; Grice, J.; Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2021yCat..36530057M Altcode: Deconvolved direct imaging observations of Kleopatra using the MISTRAL algorithm and a generated PSF.

Those fits files are direct images of (216) Kleopatra system. The reduced images were further deconvolved with the Mistral algorithm (Fusco et al., 2003, in Proc. SPIE, Vol. 4839, Adaptive Optical System Technologies II, ed. P. L. Wizinowich & D. Bonaccini, 1065-1075), using a parametric point-spread function (Fetick et al., 2019A&A...623A...6F, Cat. J/A+A/623/A6).

object.dat : ---------------------------------------------------------------------- Planet Name H Diam e i a mag km deg AU ---------------------------------------------------------------------- 216 Kleopatra 7.15 135.1 0.25126552 13.116286 2.79243307

(2 data files). Title: Evidence for differentiation of the most primitive small bodies Authors: Carry, B.; Vernazza, P.; Vachier, F.; Neveu, M.; Berthier, J.; Hanuš, J.; Ferrais, M.; Jorda, L.; Marsset, M.; Viikinkoski, M.; Bartczak, P.; Behrend, R.; Benkhaldoun, Z.; Birlan, M.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Drouard, A.; Dudziński, G. P.; Desmars, J.; Dumas, C.; Ďurech, J.; Fetick, R.; Fusco, T.; Grice, J.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marchis, F.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Podlewska-Gaca, E.; Rambaux, N.; Santana-Ros, T.; Storrs, A.; Tanga, P.; Vigan, A.; Warner, B.; Wieczorek, M.; Witasse, O.; Yang, B. Bibcode: 2021A&A...650A.129C Altcode: 2021arXiv210306349C Context. Dynamical models of Solar System evolution have suggested that the so-called P- and D-type volatile-rich asteroids formed in the outer Solar System beyond Neptune's orbit and may be genetically related to the Jupiter Trojans, comets, and small Kuiper belt objects (KBOs). Indeed, the spectral properties of P- and D-type asteroids resemble that of anhydrous cometary dust.
Aims: We aim to gain insights into the above classes of bodies by characterizing the internal structure of a large P- and D-type asteroid.
Methods: We report high-angular-resolution imaging observations of the P-type asteroid (87) Sylvia with the Very Large Telescope Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. These images were used to reconstruct the 3D shape of Sylvia. Our images together with those obtained in the past with large ground-based telescopes were used to study the dynamics of its two satellites. We also modeled Sylvia's thermal evolution.
Results: The shape of Sylvia appears flattened and elongated (a/b ~1.45; a/c ~1.84). We derive a volume-equivalent diameter of 271 ± 5 km and a low density of 1378 ± 45 kg m−3. The two satellites orbit Sylvia on circular, equatorial orbits. The oblateness of Sylvia should imply a detectable nodal precession which contrasts with the fully-Keplerian dynamics of its two satellites. This reveals an inhomogeneous internal structure, suggesting that Sylvia is differentiated.
Conclusions: Sylvia's low density and differentiated interior can be explained by partial melting and mass redistribution through water percolation. The outer shell should be composed of material similar to interplanetary dust particles (IDPs) and the core should be similar to aqueously altered IDPs or carbonaceous chondrite meteorites such as the Tagish Lake meteorite. Numerical simulations of the thermal evolution of Sylvia show that for a body of such a size, partial melting was unavoidable due to the decay of long-lived radionuclides. In addition, we show that bodies as small as 130-150 km in diameter should have followed a similar thermal evolution, while smaller objects, such as comets and the KBO Arrokoth, must have remained pristine, which is in agreement with in situ observations of these bodies. NASA Lucy mission target (617) Patroclus (diameter ≈140 km) may, however, be differentiated.

Tables A.1, B.1, C.1 and C.2 and the reduced and deconvolved SPHERE images are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/650/A129

Based on observations made with ESO telescopes at the La Silla Paranal Observatory under program 073.C-0851 (PI Merline), 073.C-0062 (PI Marchis), 085.C-0480 (PI Nitschelm), 088.C-0528 (PI Rojo), 199.C-0074 (PI Vernazza). Title: Response of the interplanetary hydrogen population to global changes of solar activity: a quantitative analysis based on SOHO/SWAN and SOHO/LASCO-C2 data comparison. Authors: Koutroumpa, Dimitra; Quémerais, Eric; Conan, Lucile; Lamy, Philippe; Ferron, Stéphane; Gilardy, Hugo Bibcode: 2021EGUGA..23.9506K Altcode: For more than two decades the SOHO/SWAN instrument has been monitoring the full-sky hydrogen backscattered Lyman-α emission, and the derived three-dimensional solar wind proton flux. We present a comparison of the time series of the latitude-integrated hydrogen ionization rates (β) derived from the inversion of the SWAN full-sky maps with the integrated coronal electron density derived from the inversion of SOHO/LASCO-C2 white light images. The analysis shows a variable time lag of the SWAN β of a few Carrington rotations, correlated with the solar cycle phase (larger delay during solar maxima compared to minima). This is a direct consequence of the variation of the size of the hydrogen ionization cavity and the time it takes for hydrogen atoms to propagate in the inner heliosphere. This effect should be taken into account in studies of the interstellar neutral populations in interplanetary space. Title: LASCO-C3 Observations of the K- and F-Coronae over 24 Years (1996 - 2019): Photopolarimetry and Electron Density Distribution Authors: Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine; Quémerais, Eric; Ernandez, Fabrice Bibcode: 2021SoPh..296...76L Altcode: We present the polarimetric analysis of the white-light images of the corona obtained with the Large-Angle Spectrometric COronagraph LASCO-C3 onboard the Solar and Heliospheric Observatory (SOHO) from 1996 to 2019, leading to the separation of the K- and F-components and the derivation of the electron-density distribution. The analysis makes use of polarized sequences composed of three images obtained through three polarizers oriented at +60∘, 0∘, and −60∘, complemented by a neighboring unpolarized image. However, the degradation of the 0∘ polarizer noticed in 1999 compelled us to reconstruct the corresponding images from those obtained with the two other polarizers and the unpolarized ones thereafter. The analysis closely follows the method developed for LASCO-C2 (Lamy et al. in Solar Phys.295, 89, 2020) and implements the formalism of Mueller, albeit with additional difficulties notably the presence of a non-axially symmetric component of stray light. Critical corrections were derived from a SOHO roll sequence and from consistency criteria (e.g. the "tangential" direction of polarization). The quasi-uninterrupted photopolarimetric analysis of the outer corona over two complete Solar Cycles 23 and 24 was successfully achieved and our final results encompass the characterization of its polarization, of its polarized radiance, of the two-dimensional electron density, and of the K-corona. Comparison between the C3 and C2 results in the region where their fields of view overlap shows an overall agreement. The C3 results are further in agreement with those of eclipses and radio-ranging measurements to an elongation of ≈10 R⊙ but tend to diverge further out. Although the coronal polarization out to 20 R⊙ is still highly correlated with the temporal variation of the total magnetic field, this divergence probably results from the increasing polarization of the F-corona with increasing solar elongation. Title: Restoration of the K and F Components of the Solar Corona from LASCO-C2 Images over 24 Years [1996 - 2019] Authors: Llebaria, Antoine; Lamy, Philippe; Gilardy, Hugo; Boclet, Brice; Loirat, Jean Bibcode: 2021SoPh..296...53L Altcode: 2020arXiv201112920L We present a photometrically accurate restoration of the K- and F-coronae from white-light images obtained over 24 years [1996 - 2019] by the Large-Angle Spectrometric COronagraph (LASCO-C2) onboard the Solar and Heliospheric Observatory (SOHO). The procedure starts with the data set of unpolarized images of 512 × 512 pixels produced by the polarimetric analysis of the routine C2 polarization sequences (Lamy et al., Solar Phys.295, 89, 2020) in which the F-corona, the instrumental stray light, and possible remnants of the K-corona due to the imperfect polarimetric separation are entangled. Disentangling these components requires a complex procedure organized in three stages, each composed of several steps. Stage 1 establishes the distinct variations of the radiance of these components with the Sun-SOHO distance, and generate a new data set of median images calculated for each Carrington rotation. Stage 2 achieves the restoration of a set of 36 stray-light images that account for the temporal variation of the stray-light pattern, in particular those associated with the periodic roll maneuvers of SOHO, which started in 2003. Stage 3 achieves the restoration of the F-corona, and a time series of daily images is generated. Combining these images with the set of stray-light images allowed us to process the whole set of routine LASCO-C2 images of 1024 × 1024 pixels (approximately 626,000 images) and to produce calibrated, high-resolution images of the K-corona. The two sets of images of the K-corona, that produced by polarimetric separation of 512 × 512 pixels images and that presently produced by subtraction, are in excellent photometric agreement. We extend our past conclusions that the temporal variation of the integrated radiance of the K-corona tracks the solar activity over Solar Cycles 23 and 24, and that it is highly correlated with the temporal variation of the total magnetic field. The behaviors of the integrated radiance during the last few years of the declining phases of Solar Cycles 23 and 24 are remarkably similar, reaching the same base level and leading to a duration of 11.0 years for the latter cycle, in agreement with that derived from sunspots. Title: VizieR Online Data Catalog: SPHERE (87) Sylvia images (Carry+, 2021) Authors: Carry, B.; Vernazza, P.; Vachier, F.; Neveu, M.; Berthier, J.; Hanus, J.; Ferrais, M.; Jorda, L.; Marsset, M.; Viikinkoski, M.; Bartczak, P.; Behrend, R.; Benkhaldoun, Z.; Birlan, M.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Drouard, A.; Dudzinski, G. P.; Desmars, J.; Dumas, J.; Durech, C.; Fetick, R.; Fusco, T.; Grice, J.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marchis, F.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Podlewska-Gaca, E.; Rambaux, N.; Santana-Ros, T.; Storrs, A.; Tanga, P.; Vigan, A.; Warner, B.; Wieczorek, M.; Witasse, O.; Yang, B. Bibcode: 2021yCat..36500129C Altcode: Sylvia was observed with the SPHERE instrument (ESO/VLT) around its opposition at eleven different epochs. We used IRDIS in broad band (Y filter; filter central wavelength 1041.4nm, width = 135.2nm) and ZIMPOL in narrowband imaging mode (N_R filter; filter central wavelength = 645.9nm, width = 56.7nm).

Each observational sequence consisted of a series of images, where each image corresponded to a series of detector integration times (DITs) of 10s, during which Sylvia was used as a natural guide star for adaptive optics (AO) corrections. Observations were performed under good seeing conditions (<=0.8") with an airmass usually below 1.6. Standard calibrations, which include detector flat-fields and darks, were acquired in the morning as part of the instrument calibration plan.

objects: ------------------------------------------------------------------- Planet Name H Diam i e a mag km deg AU ------------------------------------------------------------------- 87 Sylvia 6.86 261.0 10.87567 0.09351718 3.48178042 -------------------------------------------------------------------

(6 data files). Title: Three-Dimensional Tomographic Reconstruction and MHD Modeling of the Solar Corona and Wind: WHPI Campaign Rotations CR-2219 and CR-2223 Authors: Lloveras, D.; Vásquez, A. M.; Nuevo, F.; Sachdeva, N.; Manchester, W.; van der Holst, B.; Frazin, R. A.; Lamy, P.; Wojak, J. Bibcode: 2020AGUFMSH021..07L Altcode: Accurate prediction of space weather conditions requires state-of-the-art three-dimensional (3D) magnetohydrodynamic (MHD) models, which need to be validated with observational data. The recent deep minimum of solar activity, between solar cycles 24 and 25, renews the opportunity to study the Sun-Earth connection under the simplest solar and space environmental conditions. The international Whole Heliosphere and Planetary Interactions (WHPI) initiative aims at this specific purpose. In this work, we study two WHPI campaign periods, the July 2019 total solar eclipse Carrington rotation (CR)-2019, and the Parker Solar Probe and STEREO-A closest approach CR-2223. Based on narrowband EUV data provided by the SDO/AIA instrument we carry out tomographic reconstruction of the coronal electron density and temperature in the range of heliocentric heights r ≤ 1.25 Rsun. Based on visible light coronagraph data provided by the SoHO/LASCO-C2 instrument we carry out tomographic reconstruction of the coronal electron density and in the range of heliocentric heights ≈ 2.5-6.0 Rsun. Applying ADAPT-GONG synoptic magnetograms as boundary conditions, we use the Alfven Wave Solar Model (AWSoM) to simulate the corona and solar wind for these time periods. We study the capability of the 3D-MHD model to reproduce the tomographic reconstructions in both closed and open coronal magnetic structures. In coronal holes in particular, we investigate the correlation between the reconstructed 3D distribution of the thermodynamical properties in the low corona and the 3D distribution of the physical parameters of the terminal solar wind of the model, discriminating its fast and slow components Title: Volume uncertainty of (7) Iris shape models from disc-resolved images Authors: Dudziński, G.; Podlewska-Gaca, E.; Bartczak, P.; Benseguane, S.; Ferrais, M.; Jorda, L.; Hanuš, J.; Vernazza, P.; Rambaux, N.; Carry, B.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Brož, M.; Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Jehin, E.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2020MNRAS.499.4545D Altcode: 2020MNRAS.tmp.2956D High angular resolution disc-resolved images of (7) Iris collected by VLT/SPHERE instrument are allowed for the detailed shape modelling of this large asteroid revealing its surface features. If (7) Iris did not suffer any events catastrophic enough to disrupt the body (which is very likely) by studying its topography, we might get insights into the early Solar system's collisional history. When it comes to internal structure and composition, thoroughly assessing the volume and density uncertainties is necessary. In this work, we propose a method of uncertainty calculation of asteroid shape models based on light curve and adaptive optics (AO) images. We apply this method on four models of (7) Iris produced from independent Shaping Asteroids using Genetic Evolution and All-Data Asteroid Modelling inversion techniques and multiresolution photoclinometry by deformation. Obtained diameter uncertainties stem from both the observations from which the models were scaled and the models themselves. We show that despite the availability of high-resolution AO images, the volume and density of (7) Iris have substantial error bars that were underestimated in the previous studies. Title: The Solar Orbiter Heliospheric Imager (SoloHI) Authors: Howard, R. A.; Vourlidas, A.; Colaninno, R. C.; Korendyke, C. M.; Plunkett, S. P.; Carter, M. T.; Wang, D.; Rich, N.; Lynch, S.; Thurn, A.; Socker, D. G.; Thernisien, A. F.; Chua, D.; Linton, M. G.; Koss, S.; Tun-Beltran, S.; Dennison, H.; Stenborg, G.; McMullin, D. R.; Hunt, T.; Baugh, R.; Clifford, G.; Keller, D.; Janesick, J. R.; Tower, J.; Grygon, M.; Farkas, R.; Hagood, R.; Eisenhauer, K.; Uhl, A.; Yerushalmi, S.; Smith, L.; Liewer, P. C.; Velli, M. C.; Linker, J.; Bothmer, V.; Rochus, P.; Halain, J. -P.; Lamy, P. L.; Auchère, F.; Harrison, R. A.; Rouillard, A.; Patsourakos, S.; St. Cyr, O. C.; Gilbert, H.; Maldonado, H.; Mariano, C.; Cerullo, J. Bibcode: 2020A&A...642A..13H Altcode:
Aims: We present the design and pre-launch performance of the Solar Orbiter Heliospheric Imager (SoloHI) which is an instrument prepared for inclusion in the ESA/NASA Solar Orbiter mission, currently scheduled for launch in 2020.
Methods: The goal of this paper is to provide details of the SoloHI instrument concept, design, and pre-flight performance to give the potential user of the data a better understanding of how the observations are collected and the sources that contribute to the signal.
Results: The paper discusses the science objectives, including the SoloHI-specific aspects, before presenting the design concepts, which include the optics, mechanical, thermal, electrical, and ground processing. Finally, a list of planned data products is also presented.
Conclusions: The performance measurements of the various instrument parameters meet or exceed the requirements derived from the mission science objectives. SoloHI is poised to take its place as a vital contributor to the science success of the Solar Orbiter mission. Title: Metis: the Solar Orbiter visible light and ultraviolet coronal imager Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi, Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz; Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi, Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli, Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek; Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo, Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki, Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe; Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro; Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro; Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola; Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso, Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis, Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy, Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki, Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael; Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi, Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio; Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco; Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci, Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo; Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo; Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro; Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo, Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone, Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero, María; Amoruso, Mauro; Centonze, Vito Bibcode: 2020A&A...642A..10A Altcode: 2019arXiv191108462A
Aims: Metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (FoV) of ±2.9° in width, with an inner circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7 R⊙ to about 9 R⊙, owing to the eccentricity of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close (0.28 AU, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation.
Methods: Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light channel also includes a broadband polarimeter able to observe the linearly polarised component of the K corona. The coronal images in both the UV H I Lyman-α and polarised visible light are obtained at high spatial resolution with a spatial scale down to about 2000 km and 15 000 km at perihelion, in the cases of the visible and UV light, respectively. A temporal resolution down to 1 s can be achieved when observing coronal fluctuations in visible light.
Results: The Metis measurements, obtained from different latitudes, will allow for complete characterisation of the main physical parameters and dynamics of the electron and neutral hydrogen/proton plasma components of the corona in the region where the solar wind undergoes the acceleration process and where the onset and initial propagation of coronal mass ejections (CMEs) take place. The near-Sun multi-wavelength coronal imaging performed with Metis, combined with the unique opportunities offered by the Solar Orbiter mission, can effectively address crucial issues of solar physics such as: the origin and heating/acceleration of the fast and slow solar wind streams; the origin, acceleration, and transport of the solar energetic particles; and the transient ejection of coronal mass and its evolution in the inner heliosphere, thus significantly improving our understanding of the region connecting the Sun to the heliosphere and of the processes generating and driving the solar wind and coronal mass ejections.
Conclusions: This paper presents the scientific objectives and requirements, the overall optical design of the Metis instrument, the thermo-mechanical design, and the processing and power unit; reports on the results of the campaigns dedicated to integration, alignment, and tests, and to the characterisation of the instrument performance; describes the operation concept, data handling, and software tools; and, finally, the diagnostic techniques to be applied to the data, as well as a brief description of the expected scientific products. The performance of the instrument measured during calibrations ensures that the scientific objectives of Metis can be pursued with success.

Metis website: http://metis.oato.inaf.it Title: Coronal Photopolarimetry with the LASCO-C3 Coronagraph over 24 Years [1996-2019] -- Application to the K/F Separation and to the Determination of the Electron Density Authors: Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine; Quemerais, Eric; Ernandes, Fabrice Bibcode: 2020arXiv200904820L Altcode: We present an in-depth characterization of the polarimetric channel of the Large-Angle Spectrometric COronagraph/LASCO-C3 onboard SOHO. The polarimetric analysis of the white-light images makes use of polarized sequences composed of three images obtained through three polarizers oriented at +60$^\circ$, 0$^\circ$, and -60$^\circ$, complemented by a neighboring unpolarized image. However, the degradation of the 0$^\circ$ polarizer noticed in 1999 compelled us to reconstruct the corresponding images from the other ones thereafter. The analysis closely follows the method developed for LASCO-C2 (Lamy, et al. Solar Physics 295, 89, 2020 and arXiv:2001.05925) and implements the formalism of Mueller, albeit with additional difficulties notably the presence of a non-axially symmetric component of stray light. Critical corrections were derived from a SOHO roll sequence and from consistency criteria (e.g., the tangential direction of polarization). The quasi-uninterrupted photopolarimetric analysis of the outer corona over two complete Solar Cycles 23 and 24 was successfully achieved and our final results encompass the characterization of its polarization, of its polarized radiance, of the two-dimensional electron density, and of the K-corona. Comparison between the C3 and C2 results where their field of view overlaps shows an overall agreement. The C3 results are further in agreement with those of eclipses and radio ranging measurements to an elongation of about 10 solar radii but tend to diverge further out. Whereas the coronal polarization out to 20 solar radii is still highly correlated with the temporal variation of the total magnetic field, this divergence probably results from the increasing polarization of the F-corona. Title: Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical Authors: Yang, B.; Hanuš, J.; Carry, B.; Vernazza, P.; Brož, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Chrenko, O.; Ševeček, P.; Viikinkoski, M.; Jehin, E.; Ferrais, M.; Podlewska-Gaca, E.; Drouard, A.; Marchis, F.; Birlan, M.; Benkhaldoun, Z.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Fetick, R.; Fusco, T.; Grice, J.; Jorda, L.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O. Bibcode: 2020A&A...641A..80Y Altcode: 2020arXiv200708059Y
Aims: Asteroid (31) Euphrosyne is one of the biggest objects in the asteroid main belt and it is also the largest member of its namesake family. The Euphrosyne family occupies a highly inclined region in the outer main belt and contains a remarkably large number of members, which is interpreted as an outcome of a disruptive cratering event.
Methods: The goals of this adaptive-optics imaging study are threefold: to characterize the shape of Euphrosyne, to constrain its density, and to search for the large craters that may be associated with the family formation event.
Results: We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m VLT as part of our large program (ID: 199.C-0074, PI: Vernazza). We reconstructed its 3D shape via the ADAM shape modeling algorithm based on the SPHERE images and the available light curves of this asteroid. We analyzed the dynamics of the satellite with the Genoid meta-heuristic algorithm. Finally, we studied the shape of Euphrosyne using hydrostatic equilibrium models.
Conclusions: Our SPHERE observations show that Euphrosyne has a nearly spherical shape with the sphericity index of 0.9888 and its surface lacks large impact craters. Euphrosyne's diameter is 268 ± 6 km, making it one of the top ten largest main belt asteroids. We detected a satellite of Euphrosyne - S/2019 (31) 1 - that is about 4 km across, on a circular orbit. The mass determined from the orbit of the satellite together with the volume computed from the shape model imply a density of 1665 ± 242 kg m-3, suggesting that Euphrosyne probably contains a large fraction of water ice in its interior. We find that the spherical shape of Euphrosyne is a result of the reaccumulation process following the impact, as in the case of (10) Hygiea. However, our shape analysis reveals that, contrary to Hygiea, the axis ratios of Euphrosyne significantly differ from those suggested by fluid hydrostatic equilibrium following reaccumulation.

The reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/641/A80

Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program 199.C-0074 (PI Vernazza). Title: VizieR Online Data Catalog: Asteroid (31) Euphrosyne R-band images (Yang+, 2020) Authors: Yang, B.; Hanus, J.; Carry, B.; Vernazza, P.; Broz, M.; Vachier, F.; Rambaux, N.; Marsset, M.; Chrenko, O.; Sevecek, P.; Viikinkoski, M.; Jehin, E.; Ferrais, M.; Podlewska-Gaca, E.; Drouard, A.; Marchis, F.; Birlan, M.; Benkhaldoun, Z.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudzinski, G.; Durech, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Fetick, R.; Fusco, T.; Grice, J.; Jorda, L.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Santana-Ros, T.; Tanga, P.; Vigan, A.; Witasse, O. Bibcode: 2020yCat..36410080Y Altcode: Euphrosyne was observed, between March and April 2019 (2019-03-15, 2019-03-20, 2019-03-25, 2019-03-27, 2019-04-10), using the Zurich Imaging Polarimeter (ZIMPOL) of SPHERE in the direct imaging mode with the narrow band filter (N_R filter; filter central wavelength=645.9nm, width=56.7nm).

(2 data files). Title: Coronal Photopolarimetry with the LASCO-C2 Coronagraph over 24 Years [1996 - 2019] Authors: Lamy, Philippe; Llebaria, Antoine; Boclet, Brice; Gilardy, Hugo; Burtin, Michael; Floyd, Olivier Bibcode: 2020SoPh..295...89L Altcode: 2020arXiv200105925L We present an in-depth characterization of the polarimetric channel of the Large-Angle Spectrometric COronagraph/LASCO-C2 onboard the Solar and Heliospheric Observatory (SOHO). The polarimetric analysis of the white-light images makes use of polarized sequences composed of three images obtained though three polarizers oriented at +60∘, 0∘, and −60∘, complemented by a neighboring unpolarized image, and relies on the formalism of Mueller. The Mueller matrix characterizing the C2 instrument was obtained through extensive ground-based calibrations of the optical components and global laboratory tests. Additional critical corrections were derived from in-flight tests relying prominently on roll sequences of SOHO, on the basis of consistency criteria (e.g. the "tangential" direction of polarization), and from several applications, notably the time-dependent tomographic reconstruction of the coronal electron density. This took several years of effort, but resulted in the quasi-uninterrupted photopolarimetric analysis of the corona over two complete Solar Cycles 23 and 24, and the comparison with a variety of eclipse data obtained at different phases of these cycles. Our final results encompass the characterization of the polarization of the white-light corona, of its polarized radiance, of the two-dimensional electron density, and of the K-corona. The agreement with the eclipse data is excellent except for slight discrepancies affecting the innermost part of the C2 field of view. The present work leaves the two unpolarized components, F-corona and stray light, entangled and their complex separation will be dealt with in a follow-on article. Title: VizieR Online Data Catalog: (16) Psyche. VLT/SPHERE images and shape models (Ferrais+, 2020) Authors: Ferrais, M.; Vernazza, P.; Jorda, L.; Rambaux, N.; Hanu, J.; Carry, B.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Broz, M.; Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.; Jehin, E.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dudzinski, G.; Dumas, C.; Durech, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2020yCat..36389015F Altcode: We obtained 35 images of Psyche at 7 epochs in July and August 2019 using VLT/SPHERE/ZIMPOL. This data set complements the first 25 images taken within our ESO large program that was already presented in Viikinkoski et al. (2018A&A...619L...3V), for a total of 60 images taken at 12 epochs. All images were reduced following the procedure described in Vernazza et al. (2018A&A...618A.154V).

object: ------------------------------------------------------------------- Planet Name H Diam i e a mag km deg AU ------------------------------------------------------------------- 16 Psyche 5.90 222.0 3.096560 0.13353119 2.92277557 ------------------------------------------------------------------

(8 data files). Title: Asteroid (16) Psyche's primordial shape: A possible Jacobi ellipsoid Authors: Ferrais, M.; Vernazza, P.; Jorda, L.; Rambaux, N.; Hanuš, J.; Carry, B.; Marchis, F.; Marsset, M.; Viikinkoski, M.; Brož, M.; Fetick, R.; Drouard, A.; Fusco, T.; Birlan, M.; Podlewska-Gaca, E.; Jehin, E.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dudziński, G.; Dumas, C.; Ďurech, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2020A&A...638L..15F Altcode: Context. Asteroid (16) Psyche is the largest M-type asteroid in the main belt and the target of the NASA Psyche mission. It is also the only asteroid of this size (D > 200 km) known to be metal rich. Although various hypotheses have been proposed to explain the rather unique physical properties of this asteroid, a perfect understanding of its formation and bulk composition is still missing.
Aims: We aim to refine the shape and bulk density of (16) Psyche and to perform a thorough analysis of its shape to better constrain possible formation scenarios and the structure of its interior.
Methods: We obtained disk-resolved VLT/SPHERE/ZIMPOL images acquired within our ESO large program (ID 199.C-0074), which complement similar data obtained in 2018. Both data sets offer a complete coverage of Psyche's surface. These images were used to reconstruct the three-dimensional (3D) shape of Psyche with two independent shape modeling algorithms (MPCD and ADAM). A shape analysis was subsequently performed, including a comparison with equilibrium figures and the identification of mass deficit regions.
Results: Our 3D shape along with existing mass estimates imply a density of 4.20 ± 0.60 g cm-3, which is so far the highest for a solar system object following the four telluric planets. Furthermore, the shape of Psyche presents small deviations from an ellipsoid, that is, prominently three large depressions along its equator. The flatness and density of Psyche are compatible with a formation at hydrostatic equilibrium as a Jacobi ellipsoid with a shorter rotation period of ∼3h. Later impacts may have slowed down Psyche's rotation, which is currently ∼4.2 h, while also creating the imaged depressions.
Conclusions: Our results open the possibility that Psyche acquired its primordial shape either after a giant impact while its interior was already frozen or while its interior was still molten owing to the decay of the short-lived radionuclide 26Al.

The reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/L15

Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 199.C-0074 (PI: P. Vernazza). Title: The violent collisional history of aqueously evolved (2) Pallas Authors: Marsset, Michaël; Brož, Miroslav; Vernazza, Pierre; Drouard, Alexis; Castillo-Rogez, Julie; Hanuš, Josef; Viikinkoski, Matti; Rambaux, Nicolas; Carry, Benoît; Jorda, Laurent; Ševeček, Pavel; Birlan, Mirel; Marchis, Franck; Podlewska-Gaca, Edyta; Asphaug, Erik; Bartczak, Przemyslaw; Berthier, Jérôme; Cipriani, Fabrice; Colas, François; Dudziński, Grzegorz; Dumas, Christophe; Durech, Josef; Ferrais, Marin; Fétick, Romain; Fusco, Thierry; Jehin, Emmanuel; Kaasalainen, Mikko; Kryszczynska, Agnieszka; Lamy, Philippe; Le Coroller, Hervé; Marciniak, Anna; Michalowski, Tadeusz; Michel, Patrick; Richardson, Derek C.; Santana-Ros, Toni; Tanga, Paolo; Vachier, Frédéric; Vigan, Arthur; Witasse, Olivier; Yang, Bin Bibcode: 2020NatAs...4..569M Altcode: 2020NatAs.tmp...24M Asteroid (2) Pallas is the largest main-belt object not yet visited by a spacecraft, making its surface geology largely unknown and limiting our understanding of its origin and collisional evolution. Previous ground-based observational campaigns returned different estimates of its bulk density that are inconsistent with one another, one measurement1 being compatible within error bars with the icy Ceres (2.16 ± 0.01 g cm-3)2 and the other3 compatible within error bars with the rocky Vesta (3.46 ± 0.03 g cm-3)4. Here we report high-angular-resolution observations of Pallas performed with the extreme adaptive optics-fed SPHERE imager5 on the Very Large Telescope. Pallas records a violent collisional history, with numerous craters larger than 30 km in diameter populating its surface and two large impact basins that could be related to a family-forming impact. Monte Carlo simulations of the collisional evolution of the main belt correlate this cratering record to the high average impact velocity of ~11.5 km s-1 on Pallas—compared with an average of ~5.8 km s-1 for the asteroid belt—induced by Pallas's high orbital inclination (i = 34.8°) and orbital eccentricity (e = 0.23). Compositionally, Pallas's derived bulk density of 2.89 ± 0.08 g cm-3 (1σ uncertainty) is fully compatible with a CM chondrite-like body, as suggested by its spectral reflectance in the 3 μm wavelength region6. A bright spot observed on its surface may indicate an enrichment in salts during an early phase of aqueous alteration, compatible with Pallas's relatively high albedo of 12-17% (refs. 7,8), although alternative origins are conceivable. Title: A basin-free spherical shape as an outcome of a giant impact on asteroid Hygiea Authors: Vernazza, P.; Jorda, L.; Ševeček, P.; Brož, M.; Viikinkoski, M.; Hanuš, J.; Carry, B.; Drouard, A.; Ferrais, M.; Marsset, M.; Marchis, F.; Birlan, M.; Podlewska-Gaca, E.; Jehin, E.; Bartczak, P.; Dudzinski, G.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; DeMeo, F.; Dumas, C.; Durech, J.; Fetick, R.; Fusco, T.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Rambaux, N.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B.; Gillon, M.; Benkhaldoun, Z.; Szakats, R.; Hirsch, R.; Duffard, R.; Chapman, A.; Maestre, J. L. Bibcode: 2020NatAs...4..136V Altcode: 2019NatAs.tmp..477V (10) Hygiea is the fourth largest main belt asteroid and the only known asteroid whose surface composition appears similar to that of the dwarf planet (1) Ceres1,2, suggesting a similar origin for these two objects. Hygiea suffered a giant impact more than 2 Gyr ago3 that is at the origin of one of the largest asteroid families. However, Hygeia has never been observed with sufficiently high resolution to resolve the details of its surface or to constrain its size and shape. Here, we report high-angular-resolution imaging observations of Hygiea with the VLT/SPHERE instrument (~20 mas at 600 nm) that reveal a basin-free nearly spherical shape with a volume-equivalent radius of 217 ± 7 km, implying a density of 1,944 ± 250 kg m-3 to 1σ. In addition, we have determined a new rotation period for Hygiea of ~13.8 h, which is half the currently accepted value. Numerical simulations of the family-forming event show that Hygiea's spherical shape and family can be explained by a collision with a large projectile (diameter ~75-150 km). By comparing Hygiea's sphericity with that of other Solar System objects, it appears that Hygiea is nearly as spherical as Ceres, opening up the possibility for this object to be reclassified as a dwarf planet. Title: (704) Interamnia: a transitional object between a dwarf planet and a typical irregular-shaped minor body Authors: Hanuš, J.; Vernazza, P.; Viikinkoski, M.; Ferrais, M.; Rambaux, N.; Podlewska-Gaca, E.; Drouard, A.; Jorda, L.; Jehin, E.; Carry, B.; Marsset, M.; Marchis, F.; Warner, B.; Behrend, R.; Asenjo, V.; Berger, N.; Bronikowska, M.; Brothers, T.; Charbonnel, S.; Colazo, C.; Coliac, J. -F.; Duffard, R.; Jones, A.; Leroy, A.; Marciniak, A.; Melia, R.; Molina, D.; Nadolny, J.; Person, M.; Pejcha, O.; Riemis, H.; Shappee, B.; Sobkowiak, K.; Soldán, F.; Suys, D.; Szakats, R.; Vantomme, J.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudziński, G.; Ďurech, J.; Castillo-Rogez, J.; Cipriani, F.; Fetick, R.; Fusco, T.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2020A&A...633A..65H Altcode: 2019arXiv191113049H Context. With an estimated diameter in the 320-350 km range, (704) Interamnia is the fifth largest main belt asteroid and one of the few bodies that fills the gap in size between the four largest bodies with D > 400 km (Ceres, Vesta, Pallas and Hygiea) and the numerous smaller bodies with diameter ≤200 km. However, despite its large size, little is known about the shape and spin state of Interamnia and, therefore, about its bulk composition and past collisional evolution.
Aims: We aimed to test at what size and mass the shape of a small body departs from a nearly ellipsoidal equilibrium shape (as observed in the case of the four largest asteroids) to an irregular shape as routinely observed in the case of smaller (D ≤ 200 km) bodies.
Methods: We observed Interamnia as part of our ESO VLT/SPHERE large program (ID: 199.C-0074) at thirteen different epochs. In addition, several new optical lightcurves were recorded. These data, along with stellar occultation data from the literature, were fed to the All-Data Asteroid Modeling algorithm to reconstruct the 3D-shape model of Interamnia and to determine its spin state.
Results: Interamnia's volume-equivalent diameter of 332 ± 6 km implies a bulk density of ρ = 1.98 ± 0.68 g cm-3, which suggests that Interamnia - like Ceres and Hygiea - contains a high fraction of water ice, consistent with the paucity of apparent craters. Our observations reveal a shape that can be well approximated by an ellipsoid, and that is compatible with a fluid hydrostatic equilibrium at the 2σ level.
Conclusions: The rather regular shape of Interamnia implies that the size and mass limit, under which the shapes of minor bodies with a high amount of water ice in the subsurface become irregular, has to be searched among smaller (D ≤ 300 km) less massive (m ≤ 3 × 1019 kg) bodies.

The reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/633/A65

Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program 199.C-0074 (PI: Vernazza). Title: Imaging the Solar Corona From Within Authors: Hess, P.; Howard, R.; Vourlidas, A.; Bothmer, V.; Colaninno, R.; DeForest, C.; Gallagher, B.; Hall, J. R.; Higginson, A.; Korendyke, C.; Kouloumvakos, A.; Lamy, P.; Liewer, P.; Linker, J.; Linton, M.; Penteado, P.; Plunkett, S.; Poirer, N.; Raouafi, N.; Rich, N.; Rochus, P.; Rouillard, A.; Socker, D.; Stenborg, G.; Thernisien, A.; Viall, N. Bibcode: 2020AAS...23514907H Altcode: Parker Solar Probe (PSP), launched, in August 2018 is humanity's first probe of a stellar atmosphere. It will make measurements of the near-Sun plasma from 'within' the outer corona with gradually reduced perihelia from its first perihelia of 35 Rs in 2018-19 to 9.8 Rs in 2025. Here we report the results from the imaging observations of the electron and dust corona, whe PSP was 35-54 Rs from the solar surface, taken by the Wide-field Imager for Solar Probe (WISPR). The spacecraft was near-corotating with the solar corona throughout the observing window, which is an unprecedented situation for any type of coronal imaging. Our initial analysis uncovers a long-hypothesized depletion of the primordial dust orbiting near the Sun, reveals the plasma structure of small-scale ejections, and provides a strict test for validating model predictions of the large-scale configuration of the coronal plasma. Thus, WISPR imaging allows the study of near-Sun dust dynamics as the mission progresses. The high-resolution images of small transients, largely unresolved from 1 AU orbits, unravel the sub-structures of small magnetic flux ropes and show that the Sun continually releases helical magnetic fields in the background wind. Finally, WISPR's observations of the coronal streamer evolution confirm the large-scale topology of the solar corona but they also reveal that, as recently predicted, streamers are composed of yet smaller sub-streamers channeling continual density fluctuations at all visible scales. Title: Imaging the Solar Corona from Within: First Results from the Parker Solar Probe Telescope Authors: Howard, R. A.; Vourlidas, A.; Bothmer, V.; Colaninno, R. C.; DeForest, C.; Gallagher, B.; Hall, J. R.; Hess, P.; Higginson, A. K.; Korendyke, C.; Kouloumvakos, A.; Lamy, P.; Liewer, P. C.; Linker, J.; Linton, M.; Penteado, P. F.; Plunkett, S. P.; Poirier, N.; Raouafi, N.; Rich, N.; Rochus, P. L.; Rouillard, A. P.; Socker, D. G.; Stenborg, G.; Thernisien, A.; Viall, N. M. Bibcode: 2019AGUFMSH11A..04H Altcode: Parker Solar Probe (PSP) launched in August 2018 is humanity's first probe of a stellar atmosphere. It will make measurements of the near-Sun plasma from 'within' the outer corona with gradually reduced perihelia from its first perihelia of 35 Rs in 2018-19 to 9.8 Rs in 2025. Here we report the results from the imaging observations of the electron and dust corona, whe PSP was 35-54 Rs from the solar surface, taken by the Wide-field Imager for Solar Probe (WISPR). The spacecraft was near-corotating with the solar corona throughout the observing window, which is an unprecedented situation for any type of coronal imaging. Our initial analysis uncovers a long-hypothesized depletion of the primordial dust orbiting near the Sun, reveals the plasma structure of small-scale ejections, and provides a strict test for validating model predictions of the large-scale configuration of the coronal plasma. Thus, WISPR imaging allows the study of near-Sun dust dynamics as the mission progresses. The high-resolution images of small transients, largely unresolved from 1 AU orbits, unravel the sub-structures of small magnetic flux ropes and show that the Sun continually releases helical magnetic fields in the background wind. Finally, WISPR's observations of the coronal streamer evolution confirm the large-scale topology of the solar corona but they also reveal that, as recently predicted, streamers are composed of yet smaller sub-streamers channeling continual density fluctuations at all visible scales. Title: Polarimetric Reconstruction of Coronal Mass Ejections from LASCO-C2 Observations Authors: Floyd, Olivier; Lamy, Philippe Bibcode: 2019SoPh..294..168F Altcode: The three-dimensional morphology and direction of propagation of coronal mass ejections (CMEs) are essential information for identifying their source on the solar disk, for understanding the processes of their ejection and propagation in the corona, and for forecasting their possible impact with the Earth or any other objects in the solar system. The polarization of the Thomson scattering by an electron is known to provide information on its position with respect to the plane of the sky. This polarimetric technique is applied to reconstruct 15 CMEs on the basis of white-light polarized images obtained with the Large Angle Spectrometric Coronagraph (LASCO) C2, which have been extensively corrected for instrumental effects. It does provide valuable results in spite of the time delays between the three observations required to build the polarization maps. Most of these CMEs exhibit complex structures making a classification in terms of simple shapes such as arcade of loops or flux rope difficult or even questionable. Three of these CMEs benefited from multiple observations allowing us to follow their three-dimensional development as they propagated outward. All CMEs are tracked back to the solar surface and in several instances, active regions are identified as the probable sources. Finally, the projected speeds and masses derived from white-light unpolarized observations have been corrected for the projection angle to produce unbiased values. Title: The Solar Orbiter Heliospheric Imager (SoloHI) for the Solar Orbiter Mission: Science and Instrument Status Authors: Vourlidas, A.; Howard, R. A.; Colaninno, R. C.; Korendyke, C.; Thernisien, A.; Linton, M.; Tun Beltran, S.; Liewer, P. C.; Velli, M.; Linker, J.; Bothmer, V.; Rochus, P. L.; Lamy, P. L. Bibcode: 2019AGUFMSH24A..08V Altcode: The SoloHI instrument has completed its development effort and has been integrated onto the Solar Orbiter spacecraft. The mission, scheduled for launch in February 2020, will undergo gravity assist maneuvers around Venus to change both the perihelion distance as well as the plane of the orbit to ultimately achieve a minimum perihelion of 0.28 AU and an orbital inclination of about 35° relative to the ecliptic plane. The remote sensing instruments will operate for three 10-day periods out of the nominal 6-month orbit. SoloHI detects sunlight scattered by free electrons in the corona and solar wind from 5° to 45° elongation in visible wavelengths, providing linkage between solar and solar wind observations. The science investigation focuses mainly on the solar wind, including streamers, small-scale intensity and density fluctuations, jets, and Coronal Mass Ejections (CMEs). SoloHI is very similar to the HI-1 instrument on STEREO/SECCHI but with double the FOV of HI-1. In this paper, we present our preparations for the mission including the instrument status, our science planning strategy, our observing plans for cruise phase, calibrations, early science and our low-latency and science data products

This work has been supported by NASA. Title: Near-Sun observations of an F-corona decrease and K-corona fine structure Authors: Howard, R. A.; Vourlidas, A.; Bothmer, V.; Colaninno, R. C.; DeForest, C. E.; Gallagher, B.; Hall, J. R.; Hess, P.; Higginson, A. K.; Korendyke, C. M.; Kouloumvakos, A.; Lamy, P. L.; Liewer, P. C.; Linker, J.; Linton, M.; Penteado, P.; Plunkett, S. P.; Poirier, N.; Raouafi, N. E.; Rich, N.; Rochus, P.; Rouillard, A. P.; Socker, D. G.; Stenborg, G.; Thernisien, A. F.; Viall, N. M. Bibcode: 2019Natur.576..232H Altcode: Remote observations of the solar photospheric light scattered by electrons (the K-corona) and dust (the F-corona or zodiacal light) have been made from the ground during eclipses1 and from space at distances as small as 0.3 astronomical units2-5 to the Sun. Previous observations6-8 of dust scattering have not confirmed the existence of the theoretically predicted dust-free zone near the Sun9-11. The transient nature of the corona has been well characterized for large events, but questions still remain (for example, about the initiation of the corona12 and the production of solar energetic particles13) and for small events even its structure is uncertain14. Here we report imaging of the solar corona15 during the first two perihelion passes (0.16-0.25 astronomical units) of the Parker Solar Probe spacecraft13, each lasting ten days. The view from these distances is qualitatively similar to the historical views from ground and space, but there are some notable differences. At short elongations, we observe a decrease in the intensity of the F-coronal intensity, which is suggestive of the long-sought dust free zone9-11. We also resolve the fine-scale plasma structure of very small eruptions, which are frequently ejected from the Sun. These take two forms: the frequently observed magnetic flux ropes12,16 and the predicted, but not yet observed, magnetic islands17,18 arising from the tearing-mode instability in the current sheet. Our observations of the coronal streamer evolution confirm the large-scale topology of the solar corona, but also reveal that, as recently predicted19, streamers are composed of yet smaller substreamers channelling continual density fluctuations at all visible scales. Title: Spitzer Space Telescope observations of bilobate comet 8P/Tuttle Authors: Groussin, O.; Lamy, P. L.; Kelley, M. S. P.; Toth, I.; Jorda, L.; Fernández, Y. R.; Weaver, H. A. Bibcode: 2019A&A...632A.104G Altcode: 2019arXiv191104897G Context. Comet 8P/Tuttle is a nearly isotropic comet whose physical properties are poorly known and might be different from those of ecliptic comets owing to their different origin. Two independent observations have shown that 8P/Tuttle has a bilobate nucleus.
Aims: Our goal is to determine the physical properties of the nucleus (size, shape, thermal inertia, and albedo) and coma (water and dust) of 8P/Tuttle.
Methods: We observed the inner coma of 8P/Tuttle with the infrared spectrograph and the infrared camera of the Spitzer Space Telescope. We obtained one spectrum (5-40 μm) on 2 November 2007 and a set of 19 images at 24 μm on 22-23 June 2008 sampling the rotational period of the nucleus. The data were interpreted using thermal models for the nucleus and the dust coma, and we considered two possible shape models of the nucleus derived from Hubble Space Telescope visible and Arecibo radar observations.
Results: We favor a model for the nucleus shape that is composed of two contact spheres with respective radii of 2.7 ± 0.1 km and 1.1 ± 0.1 km and a pole orientation with RA = 285 ± 12° and Dec = +20 ± 5°. The thermal inertia of the nucleus lies in the range 0-100 J K-1 m-2 s-1/2 and the R-band geometric albedo is 0.042 ± 0.008. The water production rate amounts to 1.1 ± 0.2 × 1028 molecules s-1 at 1.6 AU from the Sun pre-perihelion, which corresponds to an active fraction of ≈9%. At the same distance, the ɛfρ quantity amounts to 310 ± 34 cm, and it reaches 325 ± 36 cm at 2.2 AU post-perihelion. The dust grain temperature is estimated to be 258 ± 10 K, which is 37 K higher than the thermal equilibrium temperature at 1.6 AU. This indicates that the dust grains that contribute to the thermal infrared flux have a typical size of ≈10 μm. The dust spectrum exhibits broad emission around 10 μm (1.5σ confidence level) and 18 μm (5σ confidence level) that we attribute to amorphous pyroxene. Title: Validation of the Alfvén Wave Solar Atmosphere Model (AWSoM) with Observations from the Low Corona to 1 au Authors: Sachdeva, Nishtha; van der Holst, Bart; Manchester, Ward B.; Tóth, Gabor; Chen, Yuxi; Lloveras, Diego G.; Vásquez, Alberto M.; Lamy, Philippe; Wojak, Julien; Jackson, Bernard V.; Yu, Hsiu-Shan; Henney, Carl J. Bibcode: 2019ApJ...887...83S Altcode: 2019arXiv191008110S We perform a validation study of the latest version of the Alfvén Wave Solar atmosphere Model (AWSoM) within the Space Weather Modeling Framework. To do so, we compare the simulation results of the model with a comprehensive suite of observations for Carrington rotations representative of the solar minimum conditions extending from the solar corona to the heliosphere up to the Earth. In the low corona (r < 1.25 {\text{}}{R}⊙ ), we compare with EUV images from both Solar-Terrestrial Relations Observatory-A/EUVI and Solar Dynamics Observatory/Atmospheric Imaging Assembly and to three-dimensional (3D) tomographic reconstructions of the electron temperature and density based on these same data. We also compare the model to tomographic reconstructions of the electron density from Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph observations (2.55 < r < 6.0{\text{}}{R}⊙ ). In the heliosphere, we compare model predictions of solar wind speed with velocity reconstructions from InterPlanetary Scintillation observations. For comparison with observations near the Earth, we use OMNI data. Our results show that the improved AWSoM model performs well in quantitative agreement with the observations between the inner corona and 1 au. The model now reproduces the fast solar wind speed in the polar regions. Near the Earth, our model shows good agreement with observations of solar wind velocity, proton temperature, and density. AWSoM offers an extensive application to study the solar corona and larger heliosphere in concert with current and future solar missions as well as being well suited for space weather predictions. Title: The Rocky-Like Behavior of Cometary Landslides on 67P/Churyumov-Gerasimenko Authors: Lucchetti, Alice; Penasa, Luca; Pajola, Maurizio; Massironi, Matteo; Brunetti, Maria Teresa; Cremonese, Gabriele; Oklay, Nilda; Vincent, Jean-Baptiste; Mottola, Stefano; Fornasier, Sonia; Sierks, Holger; Naletto, Giampiero; Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Davidsson, Bjorn; Barbieri, Cesare; Barucci, Maria Antonietta; Bertaux, Jean-Loup; Bertini, Ivano; Bodewits, Dennis; Cambianica, Pamela; Da Deppo, Vania; Debei, Stefano; De Cecco, Mariolino; Deller, Jacob; Ferrari, Sabrina; Ferri, Francesca; Franceschi, Marco; Fulle, Marco; Gutiérrez, Pedro; Güttler, Carsten; Ip, Wing-H.; Keller, Uwe; Lara, Luisa; Lazzarin, Monica; Moreno, Jose Lopez; Marzari, Francesco; Tubiana, Cecilia Bibcode: 2019GeoRL..4614336L Altcode: Landslides have been identified on several solar system bodies, and different mechanisms have been proposed to explain their runout length. We analyze images from the Rosetta mission and report the global characterization of such features on comet 67P/Churyumov-Gerasimenko's surface. By assuming the height to runout length as an approximation for the friction coefficient of landslide material, we find that on comet 67P, this ratio falls between 0.50 and 0.97. Such unexpected high values reveal a rocky-type mechanical behavior that is much more akin to Earth dry landslides than to icy satellites' mass movements. This behavior indicates that 67P and likely comets in general are characterized by consolidated materials possibly rejecting the idea that they are fluffy aggregates. The variability of the runout length among 67P landslides can be attributed to the different volatile content located in the top few meters of the cometary crust, which can drive the mass movement. Title: Validating the Alfven Wave Solar Atmosphere (AWSoM) Model from the Low Corona to 1 AU Authors: Sachdeva, N.; van der Holst, B.; Manchester, W.; Toth, G.; Lloveras, D. G.; Vásquez, A. M.; Lamy, P.; Jackson, B. V.; Henney, C. J. Bibcode: 2019AGUFMSH51A..04S Altcode: The coronal/solar wind model, the Alfven Wave Solar atmosphere Model (AWSoM) a component within the Space Weather Modeling Framework (SWMF) follows a self-consistent physics-based global description of coronal heating and solar wind acceleration. AWSoM includes a description of low-frequency forward and counter-propagating Alfven waves that non-linearly interact resulting in a turbulent cascade and dissipative heating. In addition, there are separate temperatures for electrons and protons with collisional and collisionless heat conduction applied only to electrons and radiative losses based on the Chianti model. AWSoM extends from the base of the transition region where the strong density gradient necessitates self-consistent treatment of Alfven wave reflection and balanced turbulence. It includes a stochastic heating model as well as a description of proton parallel and perpendicular temperatures and kinetic instabilities based on temperature anisotropy and plasma beta.To validate AWSoM, we model Carrington rotations representative of solar minimum conditions and compare the simulation results with a comprehensive suite of observations. In the low corona (r < 1.25 Rs), we compare with EUV images from both STEREOA/EUVI and SDO/AIA and to three-dimensional tomographic reconstructions of the electron temperature and density based on these same data. We also compare the model to tomographic reconstructions of the electron density from SOHO/LASCO observations (2.55 < r < 6 Rs). In the heliosphere, we compare model predictions of solar wind speed with velocity reconstructions from Interplanetary Scintillation observations. For comparison with observations near the Earth, we use OMNI data. Our results show that the AWSoM model performs well in quantitative agreement with the observations between the inner corona and 1 AU. In the lower corona, the model and the tomographic reconstructions agree within 20%-30% on average. The model also reproduces the fast solar wind speed in the polar regions. Near the Earth, our model shows good agreement with observations of solar wind velocity, electron temperature and density. The AWSoM model provides a comprehensive tool to study the solar corona and larger heliosphere with current and future solar missions as well as being well suited for space weather predictions. Title: VizieR Online Data Catalog: (704) Interamnia images (Hanus+, 2020) Authors: Hanus, J.; Vernazza, P.; Viikinkoski, M.; Ferrais, M.; Rambaux, N.; Podlewska-Gaca, E.; Drouard, A.; Jorda, L.; Jehin, E.; Carry, B.; Marsset, M.; Marchis, F.; Warner, B.; Behrend, R.; Asenjo, V.; Berger, N.; Bronikowska, M.; Brothers, T.; Charbonnel, S.; Colazo, C.; Coliac, J. -F.; Duard, R.; Jones, A.; Leroy, A.; Marciniak, A.; Melia, R.; Molina, D.; Nadolny, J.; Person, M.; Pejcha, O.; Riemis, H.; Shappee, B.; Sobkowiak, K.; Sold'An, F.; Suys, D.; Szakats, R.; Vantomme, J.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudzin'ski, G.; Durech, J.; Castillo-Rogez, J.; Cipriani, F.; Fetick, R.; Fusco, T.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2019yCat..36330065H Altcode: Deconvolved disk-resolved images of asteroid (704) Interamnia from VLT/SPHERE/Zimpol instrument listed in Table A1.

(2 data files). Title: Validation of MHD Model Predictions of the Corona with LASCO-C2 Polarized Brightness Images Authors: Lamy, Philippe; Floyd, Olivier; Mikić, Zoran; Riley, Pete Bibcode: 2019SoPh..294..162L Altcode: Progress in our understanding of the solar corona requires that the results of advanced magnetohydrodynamic models driven by measured magnetic fields, and particularly the underlying heating models, be thoroughly compared with coronal observations. The comparison has so far mainly concerned the global morphology of the corona, synthetic images calculated from the models being compared with observed images. We go one step further by performing detailed quantitative comparisons between the calculated polarized radiance p B using the three-dimensional electron density produced by MHD models and well calibrated polarized images obtained by the Large Angle Spectrometric Coronagraph LASCO-C2 coronagraph complemented by ground-based images when available from the Mauna Loa Solar Observatory Mark IV and K-Cor instruments to extend the comparison to the inner coronal region 1.0 - 2.5 R⊙, which is inaccessible to C2. We take advantage of the high-resolution and high-quality MHD predictions performed for several solar eclipses (1 August 2008, 11 July 2010, 13 November 2012, and 21 August 2017) and for the first perihelion passage of the Parker Solar Probe (5 November 2018) using two different three-dimensional MHD models relying on either a thermodynamic or a wave-turbulence-driven methodologies to heat the corona. Both models are generally able to match the observed structure and photometry of the corona albeit with various degrees of fidelity for which there is no obvious explanation. However, two limitations emerge, the complexity of coronae of the maximum type and the time lapse between the completion of the magnetograph measurements and the prediction. Title: Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta Authors: Tubiana, C.; Rinaldi, G.; Güttler, C.; Snodgrass, C.; Shi, X.; Hu, X.; Marschall, R.; Fulle, M.; Bockelée-Morvan, D.; Naletto, G.; Capaccioni, F.; Sierks, H.; Arnold, G.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Capria, M. T.; Ciarniello, M.; Cremonese, G.; Crovisier, J.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; De Sanctis, M. C.; Davidsson, B.; Doose, L.; Erard, S.; Filacchione, G.; Fink, U.; Formisano, M.; Fornasier, S.; Gutiérrez, P. J.; Ip, W. -H.; Ivanovski, S.; Kappel, D.; Keller, H. U.; Kolokolova, L.; Koschny, D.; Krueger, H.; La Forgia, F.; Lamy, P. L.; Lara, L. M.; Lazzarin, M.; Levasseur-Regourd, A. C.; Lin, Z. -Y.; Longobardo, A.; López-Moreno, J. J.; Marzari, F.; Migliorini, A.; Mottola, S.; Rodrigo, R.; Taylor, F.; Toth, I.; Zakharov, V. Bibcode: 2019A&A...630A..23T Altcode: 2019arXiv190503022T Context. On 27 April 2015, when comet 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving toward perihelion, the OSIRIS and VIRTIS-M instruments on board the Rosetta spacecraft simultaneously observed the evolving dust and gas coma during a complete rotation of the comet.
Aims: We aim to characterize the spatial distribution of dust, H2O, and CO2 gas in the inner coma. To do this, we performed a quantitative analysis of the release of dust and gas and compared the observed H2O production rate with the rate we calculated using a thermophysical model.
Methods: For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H2O emission band), and 4200 nm (CO2 emission band). We measured the average signal in a circular annulus to study the spatial variation around the comet, and in a sector of the annulus to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the comet center.
Results: The spatial correlation between dust and water, both coming from the sunlit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0° subsolar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO2 production. An excess of measured water production with respect to the value calculated using a simple thermophysical model is observed when the head lobe and regions of the southern hemisphere with strong seasonal variations are illuminated (subsolar longitude 270°-50°). A drastic decrease in dust production when the water production (both measured and from the model) displays a maximum occurs when typical northern consolidated regions are illuminated and the southern hemisphere regions with strong seasonal variations are instead in shadow (subsolar longitude 50°-90°). Possible explanations of these observations are presented and discussed. Title: Rosetta/OSIRIS observations of the 67P nucleus during the April 2016 flyby: high-resolution spectrophotometry Authors: Feller, C.; Fornasier, S.; Ferrari, S.; Hasselmann, P. H.; Barucci, A.; Massironi, M.; Deshapriya, J. D. P.; Sierks, H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B. J. R.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Shi, X.; Tubiana, C.; Gaskell, B.; La Forgia, F.; Lucchetti, A.; Mottola, S.; Pajola, M.; Preusker, F.; Scholten, F. Bibcode: 2019A&A...630A...9F Altcode: 2018arXiv181209415F Context. From August 2014 to September 2016, the Rosetta spacecraft followed comet 67P/Churyumov-Gerasimenko along its orbit. After the comet passed perihelion, Rosetta performed a flyby manoeuvre over the Imhotep-Khepry transition in April 2016. The OSIRIS/Narrow-Angle-Camera (NAC) acquired 112 observations with mainly three broadband filters (centered at 480, 649, and 743 nm) at a resolution of up to 0.53 m/px and for phase angles between 0.095° and 62°.
Aims: We have investigated the morphological and spectrophotometrical properties of this area using the OSIRIS/NAC high-resolution observations.
Methods: We assembled the observations into coregistered color cubes. Using a 3D shape model, we produced the illumination conditions and georeference for each observation. We mapped the observations of the transition to investigate its geomorphology. Observations were photometrically corrected using the Lommel-Seeliger disk law. Spectrophotometric analyses were performed on the coregistered color cubes. These data were used to estimate the local phase reddening.
Results: The Imhotep-Khepry transition hosts numerous and varied types of terrains and features. We observe an association between a feature's nature, its reflectance, and its spectral slopes. Fine material deposits exhibit an average reflectance and spectral slope, while terrains with diamictons, consolidated material, degraded outcrops, or features such as somber boulders present a lower-than-average reflectance and higher-than-average spectral slope. Bright surfaces present here a spectral behavior consistent with terrains enriched in water-ice. We find a phase-reddening slope of 0.064 ± 0.001%/100 nm/° at 2.7 au outbound, similar to the one obtained at 2.3 au inbound during the February 2015 flyby.
Conclusions: Identified as the source region of multiple jets and a host of water-ice material, the Imhotep-Khepry transition appeared in April 2016, close to the frost line, to further harbor several potential locations with exposed water-ice material among its numerous different morphological terrain units. Title: Surface evolution of the Anhur region on comet 67P/Churyumov-Gerasimenko from high-resolution OSIRIS images Authors: Fornasier, S.; Feller, C.; Hasselmann, P. H.; Barucci, M. A.; Sunshine, J.; Vincent, J. -B.; Shi, X.; Sierks, H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Ferrari, S.; Fulle, M.; Gutierrez, P. J.; Güttler, C.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Lara, M. L.; Lazzarin, M.; Lopez Moreno, J. J.; Lucchetti, A.; Marzari, F.; Mottola, S.; Pajola, M.; Toth, I.; Tubiana, C. Bibcode: 2019A&A...630A..13F Altcode: 2019arXiv190309017F Context. The southern hemisphere of comet 67P/Churyumov-Gerasimenko (67P) became observable by the Rosetta mission in March 2015, a few months before cometary southern vernal equinox. The Anhur region in the southern part of the comet's larger lobe was found to be highly eroded, enriched in volatiles, and highly active.
Aims: We analyze high-resolution images of the Anhur region pre- and post-perihelion acquired by the OSIRIS imaging system on board the Rosetta mission. The Narrow Angle Camera is particularly useful for studying the evolution in Anhur in terms of morphological changes and color variations.
Methods: Radiance factor images processed by the OSIRIS pipeline were coregistered, reprojected onto the 3D shape model of the comet, and corrected for the illumination conditions.
Results: We find a number of morphological changes in the Anhur region that are related to formation of new scarps; removal of dust coatings; localized resurfacing in some areas, including boulders displacements; and vanishing structures, which implies localized mass loss that we estimate to be higher than 50 million kg. The strongest changes took place in and nearby the Anhur canyon-like structure, where significant dust cover was removed, an entire structure vanished, and many boulders were rearranged. All such changes are potentially associated with one of the most intense outbursts registered by Rosetta during its observations, which occurred one day before perihelion passage. Moreover, in the niche at the foot of a new observed scarp, we also see evidence of water ice exposure that persisted for at least six months. The abundance of water ice, evaluated from a linear mixing model, is relatively high (>20%). Our results confirm that the Anhur region is volatile-rich and probably is the area on 67P with the most pristine exposures near perihelion.

The movies associated to Figs. 2, 7, 8, and 10 are available at https://www.aanda.org Title: Linking surface morphology, composition, and activity on the nucleus of 67P/Churyumov-Gerasimenko Authors: Fornasier, S.; Hoang, V. H.; Hasselmann, P. H.; Feller, C.; Barucci, M. A.; Deshapriya, J. D. P.; Sierks, H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Agarwal, J.; Barbieri, C.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Ferrari, S.; Fulle, M.; Gutierrez, P. J.; Güttler, C.; Ip, W. -H.; Keller, H. U.; Küppers, M.; La Forgia, F.; Lara, M. L.; Lazzarin, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Pajola, M.; Shi, X.; Toth, I.; Tubiana, C. Bibcode: 2019A&A...630A...7F Altcode: 2018arXiv180903997F
Aims: The Rosetta space probe accompanied comet 67P/Churyumov-Gerasimenko for more than two years, obtaining an unprecedented amount of unique data of the comet nucleus and inner coma. This has enabled us to study its activity almost continuously from 4 au inbound to 3.6 au outbound, including the perihelion passage at 1.24 au. This work focuses identifying the source regions of faint jets and outbursts and on studying the spectrophotometric properties of some outbursts. We use observations acquired with the OSIRIS/NAC camera during July-October 2015, that is, close to perihelion.
Methods: We analyzed more than 2000 images from NAC color sequences acquired with 7-11 filters covering the 250-1000 nm wavelength range. The OSIRIS images were processed with the OSIRIS standard pipeline up to level 3, that is, converted in radiance factor, then corrected for the illumination conditions. For each color sequence, color cubes were produced by stacking registered and illumination-corrected images.
Results: More than 200 jets of different intensities were identified directly on the nucleus. Some of the more intense outbursts appear spectrally bluer than the comet dark terrain in the visible-to-near-infrared region. We attribute this spectral behavior to icy grains mixed with the ejected dust. Some of the jets have an extremely short lifetime. They appear on the cometary surface during the color sequence observations, and vanish in less than some few minutes after reaching their peak. We also report a resolved dust plume observed in May 2016 at a resolution of 55 cm pixel-1, which allowed us to estimate an optical depth of ~0.65 and an ejected mass of ~2200 kg, assuming a grain bulk density of ~800 kg m-3. We present the results on the location, duration, and colors of active sources on the nucleus of 67P from the medium-resolution (i.e., 6-10 m pixel-1) images acquired close to perihelion passage. The observed jets are mainly located close to boundaries between different morphological regions. Some of these active areas were observed and investigated at higher resolution (up to a few decimeter per pixel) during the last months of operations of the Rosetta mission.
Conclusions: These observations allow us to investigate the link between morphology, composition, and activity of cometary nuclei. Jets depart not only from cliffs, but also from smooth and dust-covered areas, from fractures, pits, or cavities that cast shadows and favor the recondensation of volatiles. This study shows that faint jets or outbursts continuously contribute to the cometary activity close to perihelion passage, and that these events are triggered byillumination conditions. Faint jets or outbursts are not associated with a particular terrain type or morphology. Title: Seasonal variations in source regions of the dust jets on comet 67P/Churyumov-Gerasimenko Authors: Lai, I. -L.; Ip, W. -H.; Lee, J. -C.; Lin, Z. -Y.; Vincent, J. -B.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Shi, X.; Tubiana, C.; Thomas, N. Bibcode: 2019A&A...630A..17L Altcode:
Aims: We investigate the surface distribution of the source regions of dust jets on comet 67P/Churyumov-Gerasimenko as a function of time.
Methods: The dust jet source regions were traced by the comprehensive imaging data set provided by the OSIRIS scientific camera.
Results: We show in detail how the projected footpoints of the dust jets and hence the outgassing zone would move in consonance with the sunlit belt. Furthermore, a number of source regions characterized by repeated jet activity might be the result of local topographical variations or compositional heterogeneities.
Conclusions: The spatial and temporal variations in source regions of the dust jets are influenced significantly by the seasonal effect. The strong dependence on the solar zenith angle and local time could be related to the gas sublimation process driven by solar insolation on a surface layer of low thermal inertia. Title: Pronounced morphological changes in a southern active zone on comet 67P/Churyumov-Gerasimenko Authors: Hasselmann, P. H.; Barucci, M. A.; Fornasier, S.; Bockelée-Morvan, D.; Deshapriya, J. D. P.; Feller, C.; Sunshine, J.; Hoang, V.; Sierks, H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; Fulle, M.; Gutierrez, P. J.; Güttler, C.; Deller, J.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; De Cecco, M.; Lazzarin, M.; López-Moreno, J. J. L.; Marzari, F.; Shi, X.; Tubiana, C. Bibcode: 2019A&A...630A...8H Altcode: A smooth deposit in the southern Khonsu region has been seen in ESA/Rosetta observations as active during the second half of 2015, when the southern summer coincided with the perihelion passage of 67P/Churyumov-Gerasimenko (67P). Image color sequences acquired by the OSIRIS instrument in the period of January 2015 to July 2016, pre- and post-perihelion, show the occurrence of several small transient events as well as three massive outbursts ( 10 to 1500 tons). High spatial resolution images taken one year and a half apart allowed us to track a variety of sources: the formation of cavities that are 1.3-14 m deep, ice-enriched patches, scarp retraction, and a second 50 m-wide boulder. We then estimated their masses and the dust mass of their corresponding plumes and outbursts. In particular, the deformation left by that boulder and its lack of talus may provide evidence for the lifting and subsequent falling back to the surface of large blocks. We calculate that a minimum vapor production rate of 1.4 × 1024 m-2 s-1 is required to lift such an object. The comparison of the masses that are lost in the new cavities to the dust mass of outbursts gives indirect evidence of highly volatile ice pockets underneath. The spectrophotometric analysis and boulder counting also provides evidence for cavities that formed only 30 m apart with different spectral slopes, two long-standing ice patches, and local variations in the boulder-size frequency distribution. All this points to sub-surface ice pockets with different degrees of depth. Finally, the total mass of the morphological changes compared to most recent calculations of the total released mass by activity on 67P is estimated to be between 1.5 and 4.2%. This means that as many as about 25 similar active zones across the nucleus would be enough to sustain the entire cometary activity. Title: Quantitative analysis of isolated boulder fields on comet 67P/Churyumov-Gerasimenko Authors: Cambianica, P.; Cremonese, G.; Naletto, G.; Lucchetti, A.; Pajola, M.; Penasa, L.; Simioni, E.; Massironi, M.; Ferrari, S.; Bodewits, D.; La Forgia, F.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; López-Moreno, J. J.; Marzari, F.; Mottola, S.; Shi, X.; Scholten, F.; Toth, I.; Tubiana, C.; Vincent, J. -B. Bibcode: 2019A&A...630A..15C Altcode:
Aims: We provide a detailed quantitative analysis of isolated boulder fields situated in three different regions of comet 67P/Churyumov-Gerasimenko: Imhotep, Hapi, and Hatmehit. This is done to supply a useful method for analyzing the morphology of the boulders and to characterize the regions themselves.
Methods: We used OSIRIS Narrow Angle Camera images with a spatial scale smaller than 2 m px-1 and analyzed the size-frequency distribution and the cumulative fractional area per boulder population. In addition, we correlated shape parameters, such as circularity and solidity, with both the spatial and the size-frequency distribution of the three populations.
Results: We identified 11 811 boulders in the Imhotep, Hapi, and Hatmehit regions. We found that the Hatmehit and Imhotep areas show power indices in the range of -2.3/-2.7. These values could represent a transition between gravitational events caused by thermal weathering and sublimation, and material formed during collapses that has undergone sublimation. The Hapi area is characterized by a lower power index (-1.2/-1.7), suggesting that those boulders have a different origin. They can be the result of material formed during gravitational events and collapses that has undergone continuous fragmentation. We calculated the cumulative fractional area (CFA) in order to investigate how the area is covered by boulders as a function of their sizes. The Hatmehit and Imhotep regions show a CFA that is well fit by a power law. In contrast, the Hapi area does not show the same trend. We analyzed the fractal distributions, finding that the populations seem to be fractal at all dimensions, except for the Hapi distribution, which shows a possible fractal behavior for small dimensions only. Finally, the average values of the shape parameters reveal solid and roundish boulders in all populations we studied. Title: Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles Authors: Masoumzadeh, N.; Kolokolova, L.; Tubiana, C.; El-Maarry, M. R.; Mottola, S.; Güttler, C.; Snodgrass, C.; Sierks, H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Hasselmann, P. H.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Shi, X.; Toth, I. Bibcode: 2019A&A...630A..11M Altcode:
Aims: The Rosetta-OSIRIS images acquired at small phase angles in three wavelengths during the fly-by of the spacecraft on 9-10 April 2016 provided a unique opportunity to study the opposition effect on the surface of comet 67P/Churyumov-Gerasimenko (67P). Our goal is to study phase curves of the nucleus at small phase angles for a variety of surface structures to show the differences in their opposition effect and to determine which surface properties cause the differences.
Methods: We used OSIRIS NAC images that cover the Ash-Khepry-Imhotep region to extract the phase curve, that is, the reflectance of the surface as a function of phase angle. We selected six regions of interest (ROIs) and derived the phase curves for each ROI. We fit a linear-exponential function to the phase curves. The resulting model parameters were then interpreted by spectrophotometric, geomorphological, and phase-ratio analyses, and by investigating the influence of structural and textural properties of the surface.
Results: We find evidence for the opposition effect (deviation of the phase curve from linear behavior) in phase curves for all areas. We found an anticorrelation between the phase ratio and reflectance in a small phase angle range. This provides evidence for the shadow-hiding effect. We conclude that the decrease in the slope of the phase ratio versus reflectance indicates a decrease in the proportion of shadowed regions and reduces the contribution of the shadow-hiding effect. Large uncertainties in the determination of the opposition effect parameters with respect to wavelength do not allow us to conclusively claim coherent backscattering in the opposition effect phenomenon. Based on the two analyses, we conclude that the opposition effect of comet 67P in the Ash-Khepry-Imhotep region is mainly affected by shadow-hiding. Title: Spectrophotometric variegation of the layering in comet 67P/Churyumov-Gerasimenko as seen by OSIRIS Authors: Tognon, G.; Ferrari, S.; Penasa, L.; La Forgia, F.; Massironi, M.; Naletto, G.; Lazzarin, M.; Cambianica, P.; Lucchetti, A.; Pajola, M.; Ferri, F.; Güttler, C.; Davidsson, B.; Deshapriya, P.; Fornasier, S.; Mottola, S.; Tóth, I.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Franceschi, M.; Frattin, E.; Fulle, M.; Gutiérrez, P. J.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; López-Moreno, J. J.; Marzari, F.; Petropoulou, V.; Shi, X.; Tubiana, C. Bibcode: 2019A&A...630A..16T Altcode: Context. Between August 2014 and September 2016, the ESA space mission Rosetta escorted comet 67P/Churyumov-Gerasimenko (67P) during its perihelion passage. The onboard OSIRIS Narrow Angle Camera (NAC) acquired high-resolution multispectral images of the cometary surface. These datasets allowed a characterization of the spectrophotometric variegation of the layering of the large lobe, correlated with the layer structural elevation.
Aims: We perform a spectrophotometric characterization of the outcropping stratification of the small lobe of 67P as a function of its structural elevation, and consequently, a spectrophotometric comparison of the layered outcrops of the two lobes.
Methods: We selected two sequences of post-perihelion OSIRIS NAC images ( 2.4 au outbound tothe Sun), from which we built up two multispectral images, framing an extended geological section of the onion-like stratification of the small lobe. Then we classified the consolidated areas of the outcropping and the relative coarse deposits that were identified in the multispectral data with a two-class maximum likelihood method. For this, we defined the classes as a function of the structural elevation of the surface.
Results: As a result, we identified a brightness variegation of the surface reflectance that is correlated with the structural elevation. The outer class, which is located at higher elevations, appears darker than the inner class. This fits previously obtained results for the large lobe. The reflectance values of the nucleus of 67P tend to decrease with increasing structural elevation.
Conclusions: The observed spectrophotometric variegation can be due to a different texture as well as to a different content of volatiles and refractories. We suggest that the outer outcrops appear darker because they have been exposed longer, and the inner outcrops appear brighter because the surface has been more effectively rejuvenated. We interpret this variegation as the result of an evolutionary process. Title: A catalog of stereo anaglyphs of comet 67P/Churyumov-Gerasimenko - Application to the detection of deep ice pits Authors: Lamy, Philippe; Faury, Guillaume; Romeuf, David; Groussin, Olivier; Durand, Joelle Bibcode: 2019EPSC...13..719L Altcode: The OSIRIS/NAC camera aboard the Rosetta spacecraft has acquired approximately 27000 images of comet 67P/Churyumov-Gerasimenko at spatial scales down to a few centimeters. We exploit the numerous sequences of images separated by a few minutes suitable for stereo reconstructions to produce anaglyphs offering three-dimensional views of the comet, complementary to other technics, as a tool to understand the topography of the nucleus. Each anaglyph is documented by a set of 17 parameters which provide the contextual information. Over 1400 anaglyphs have been produced and cataloged so far; they are available on a dedicated website and can be searched using the associated parameters. As a first application, we present direct evidences of sub-surface ice at the bottom of deep pits, so-called "ice pits" identified on high-resolution anaglyphs. Their geometry and size are obtained from stereographic reconstruction. Both their high reflectivity and their blue color substantiate the presence of ice. Title: Coronal Mass Ejections over Solar Cycles 23 and 24 Authors: Lamy, P. L.; Floyd, O.; Boclet, B.; Wojak, J.; Gilardy, H.; Barlyaeva, T. Bibcode: 2019SSRv..215...39L Altcode: We present a statistical analysis of solar coronal mass ejections (CMEs) based on 23 years of quasi-continuous observations with the LASCO coronagraph, thus covering two complete Solar Cycles (23 and 24). We make use of five catalogs, one manual (CDAW) and four automated (ARTEMIS, CACTus, SEEDS, and CORIMP), to characterize the temporal evolutions and distributions of their properties: occurrence and mass rates, waiting times, periodicities, angular width, latitude, speed, acceleration and kinetic energy. Our analysis points to inevitable discrepancies between catalogs due to the complex nature of CMEs and to the different techniques implemented to detect them, but also to large areas of convergence that are critically important to ascertain the reliability of the results. The temporal variations of these properties are compared to four indices/proxies of solar activity: the radio flux at 10.7 cm (F10.7), the international sunspot number (SSN), the sunspot area (SSA), and the total magnetic field (TMF), either globally or separately in the northern and southern hemispheres in the case of the last three. We investigate the association of CMEs with flares, erupting prominences, active regions and streamers. We find that the CME occurrence and mass rates globally track the indices/proxies of solar activity with no time lag, prominently the radio flux F10.7, but the linear relationships were different during the two solar cycles, implying that the CME rates were relatively larger during SC 24 than during SC 23. However, there exists a pronounced divergence of the CME rates in the northern hemisphere during SC 24 as these rates were substantially larger than predicted by the temporal variation of the sunspot number. The distribution of kinetic energy follows a log-normal law and that of angular width follows an exponential law implying that they are random and independent. The distribution of waiting time (WTD) has a long power-law tail extending from 3 to 100 hr with a power-law index which varies with the solar cycle, thus reflecting the temporal variability of the process of CME formation. There is very limited evidence for periodicities in the occurrence and mass rates of CMEs, a striking feature being the dichotomy between the two hemispheres. Rather weak correlations are present among the various CME parameters and particularly none between speed and acceleration. The association of CMEs with flares and erupting prominences involves only a few percents of the overall population of CMEs but the associated CMEs have distinctly larger mass, speed, kinetic energy and angular width. A more pronounced association is found with active regions but the overwhelming one is with streamers further confirmed by the similarity between the heliolatitudinal distribution of CMEs and that of the electron density reconstructed from time-dependent tomographic inversion. We find no evidence of bimodality in the distributions of physical parameters that would support the existence of two classes, particularly that based on speed and acceleration, the distributions thus favoring a continuum of properties. There exists an excess of narrows CMEs which however does not define a special class. These narrow CMEs are likely associated with the ubiquitous mini-filaments eruptions and with mini flux ropes originating from small magnetic bipoles, the disruption mechanisms being similar to those launching larger CMEs. This supports the concept that CMEs at large arise from closed-field coronal regions at both large and small scales. Title: Tomography of the Solar Corona with the Wide-Field Imager for the Parker Solar Probe Authors: Vásquez, Alberto M.; Frazin, Richard A.; Vourlidas, Angelos; Manchester, Ward B.; van der Holst, Bart; Howard, Russell A.; Lamy, Philippe Bibcode: 2019SoPh..294...81V Altcode: The Wide-field Imager for the Parker Solar Probe (PSP/WISPR) comprises two telescopes that record white-light total brightness [B ] images of the solar corona. Their fields of view cover a widely changing range of heliocentric heights over the 24 highly eccentric orbits planned for the mission. In this work, the capability of PSP/WISPR data to carry out tomographic reconstructions of the three-dimensional (3D) distribution of the coronal electron density is investigated. Based on the precise orbital information of the mission, B -images for Orbits 1, 12, and 24 are synthesized from a 3D magnetohydrodynamic model of the corona. For each orbit, the time series of synthetic images is used to carry out a tomographic reconstruction of the coronal electron density and results are compared with the model. As the PSP perihelion decreases, the range of heights that can be tomographically reconstructed progressively shifts to lower values, and the period required to gather the data decreases. For Orbit 1 tomographic reconstruction is not possible. For Orbit 12, tomographic reconstruction is possible in the heliocentric height range ≈5 -15 R⊙, over a region spanning up to ≈160∘ in Carrington longitude, with data gathered over a ≈3.4 day-long period. For Orbit 24, tomographic reconstruction is possible in the heliocentric height range ≈3 -10 R⊙, over a region spanning up to ≈170∘ in Carrington longitude, with data gathered over a ≈2.8 day-long period. Title: Multidisciplinary analysis of the Hapi region located on Comet 67P/Churyumov-Gerasimenko Authors: Pajola, M.; Lee, J. -C.; Oklay, N.; Hviid, S. F.; Penasa, L.; Mottola, S.; Shi, X.; Fornasier, S.; Davidsson, B.; Giacomini, L.; Lucchetti, A.; Massironi, M.; Vincent, J. B.; Bertini, I.; Naletto, G.; Ip, W. H.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. L.; Bodewits, D.; Cambianica, P.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; El Maarry, M. R.; Feller, C.; Ferrari, S.; Fulle, M.; Gutierrez, P. J.; Güttler, C.; Lara, L. M.; La Forgia, F.; Lazzarin, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Marzari, F.; Preusker, F.; Scholten, F.; Toth, I.; Tubiana, C. Bibcode: 2019MNRAS.485.2139P Altcode: By using the Rosetta/OSIRIS-NAC data set taken in 2014 August, we focus on the neck region, called Hapi, located on 67P Churyumov-Gerasimenko's Northern hemisphere. The gravitational potential and slopes of Hapi, coupled with the geological unit identification and the boulder size-frequency distributions, support the interpretation that both taluses and gravitational accumulation deposits observable on Hapi are the result of multiple cliff collapses that occurred at different times. By contrast, the fine-particle deposits observable in the central part of the study area are made of aggregates coming from the Southern hemisphere and deposited during each perihelion passage. Both the consolidated terrains on the western part of Hapi, as well as the centrally aligned ridge made of boulder-like features, suggest that Hapi is in structural continuity with the onion-like structure of the main lobe of 67P. Despite the dusty blanket observable on Hapi, its terrains are characterized by water-ice-rich components that, once repeatedly and rapidly illuminated, sublimate, hence resulting in the strong jet activity observed in 2014 August. Title: The shape of (7) Iris as evidence of an ancient large impact? Authors: Hanuš, J.; Marsset, M.; Vernazza, P.; Viikinkoski, M.; Drouard, A.; Brož, M.; Carry, B.; Fetick, R.; Marchis, F.; Jorda, L.; Fusco, T.; Birlan, M.; Santana-Ros, T.; Podlewska-Gaca, E.; Jehin, E.; Ferrais, M.; Grice, J.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dudziński, G.; Dumas, C.; Ďurech, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2019A&A...624A.121H Altcode: 2019arXiv190209242H Context. Asteroid (7) Iris is an ideal target for disk-resolved imaging owing to its brightness (V 7-8) and large angular size of 0.33'' during its apparitions. Iris is believed to belong to the category of large unfragmented asteroids that avoided internal differentiation, implying that its current shape and topography may record the first few 100 Myr of the solar system's collisional evolution.
Aims: We recovered information about the shape and surface topography of Iris from disk-resolved VLT/SPHERE/ZIMPOL images acquired in the frame of our ESO large program.
Methods: We used the All-Data Asteroid Modeling (ADAM) shape reconstruction algorithm to model the 3D shape of Iris, using optical disk-integrated data and disk-resolved images from SPHERE and earlier AO systems as inputs. We analyzed the SPHERE images and our model to infer the asteroid's global shape and the morphology of its main craters.
Results: We present the 3D shape, volume-equivalent diameter Deq = 214 ± 5 km, and bulk density ρ = 2.7 ± 0.3 g cm-3 of Iris. Its shape appears to be consistent with that of an oblate spheroid with a large equatorial excavation. We identified eight putative surface features 20-40 km in diameter detected at several epochs, which we interpret as impact craters, and several additional crater candidates. Craters on Iris have depth-to-diameter ratios that are similar to those of analogous 10 km craters on Vesta.
Conclusions: The bulk density of Iris is consistent with that of its meteoritic analog based on spectroscopic observations, namely LL ordinary chondrites. Considering the absence of a collisional family related to Iris and the number of large craters on its surface, we suggest that its equatorial depression may be the remnant of an ancient (at least 3 Gyr) impact. Iris's shape further opens the possibility that large planetesimals formed as almost perfect oblate spheroids. Finally, we attribute the difference in crater morphology between Iris and Vesta to their different surface gravities, and the absence of a substantial impact-induced regolith on Iris.

The reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A121Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 199.C-0074 (PI: P. Vernazza) and 086.C-0785 (PI: B. Carry). Title: VizieR Online Data Catalog: Asteroid (7) Iris Deconvolved disk-resolved images (Hanus+, 2019) Authors: Hanus, J.; Marsset, M.; Vernazza, P.; Viikinkoski, M.; Drouard, A.; Broz, M.; Carry, B.; Fetick, R.; Marchis, F.; Jorda, L.; Fusco, T.; Birlan, M.; Santana-Ros, T.; Podlewska-Gaca, E.; Jehin, E.; Ferrais, M.; Grice, J.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dudzinski, G.; Dumas, C.; Durech, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2019yCat..36240121H Altcode: Deconvolved disk-resolved images of asteroid (7) Iris from Keck/Nirc2, VLT/NaCo and VLT/SPHERE/Zimpol instruments listed in Table C.2. The final shape model is based on the VLT/SPHERE/Zimpol data and a subset of the Keck/Nirc2 and VLT.NaCo data. The remaining data of a poor quality, often affected by deconvolution artifact, were used for consistency check only. The ordering of the data corresponds to the ordering in Table C2.

(2 data files). Title: VizieR Online Data Catalog: SPHERE/ZIMPOL (41) Daphne images (Carry+, 2019) Authors: Carry, B.; Vachier, F.; Berthier, J.; Marsset, M.; Vernazza, P.; Grice, J.; Merline, W. J.; Lagadec, E.; Fienga, A.; Conrad, A.; Podlewska-Gaca, E.; Santana-Ros, T.; Viikinkoski, M.; Hanus, J.; Dumas, C.; Drummond, J. D.; Tamblyn, P. M.; Chapman, C. R.; Behrend, R.; Bernasconi, L.; Bartczak, P.; Benkhaldoun, Z.; Birlan, M.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Drouard, A.; Durech, J.; Enke, B. L.; Fauvaud, S.; Ferrais, M.; Fetick, R.; Fusco, T.; Gillon, M.; Jehin, E.; Jorda, L.; Kaasalainen, M.; Keppler, M.; Kryszczynska, A.; Lamy, P.; Marchis, F.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B.; Zurlo, A. Bibcode: 2019yCat..36230132C Altcode: Daphne was observed with the SPHERE instrument (ESO/VLT) around its opposition at eight different epochs. We used ZIMPOL in narrowband imaging mode (N_R filter; filter central wavelength = 645.9nm, width = 56.7nm). Each observational sequence consisted of a series of five images, where each image corresponded to a series of detector integration times (DITs) of 10s, during which Julia was used as a natural guide star for adaptive optics (AO) corrections. Observations were performed under good seeing conditions (<=0.8") with an airmass usually below 1.6. After every asteroid observation, we observed a nearby star for deconvolution purposes to estimate the instrument point spread function (PSF). Finally, standard calibrations, which include detector flat-fields and darks, were acquired in the morning as part of the instrument calibration plan.

For a full description of the parameters, see: https://astro.troja.mff.cuni.cz/projects/asteroids3D/\ web.php?page=db_description and Durech et al. (2010A&A...513A..46D)

object: ------------------------------------------------------------------- Planet Name H Diam i e a mag km deg AU ------------------------------------------------------------------- 41 Daphne 7.12 187.0 15.792100 0.27541753 2.76043870 -------------------------------------------------------------------

(5 data files). Title: Closing the gap between Earth-based and interplanetary mission observations: Vesta seen by VLT/SPHERE Authors: Fétick, R. JL.; Jorda, L.; Vernazza, P.; Marsset, M.; Drouard, A.; Fusco, T.; Carry, B.; Marchis, F.; Hanuš, J.; Viikinkoski, M.; Birlan, M.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dudziński, G.; Dumas, C.; Ferrais, M.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Mugnier, L. M.; Neichel, B.; Pajuelo, M.; Podlewska-Gaca, E.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2019A&A...623A...6F Altcode: 2019arXiv190201287F Context. Over the past decades, several interplanetary missions have studied small bodies in situ, leading to major advances in our understanding of their geological and geophysical properties. These missions, however, have had a limited number of targets. Among them, the NASA Dawn mission has characterised in detail the topography and albedo variegation across the surface of asteroid (4) Vesta down to a spatial resolution of ~20 m pixel-1 scale.
Aims: Here our aim was to determine how much topographic and albedo information can be retrieved from the ground with VLT/SPHERE in the case of Vesta, having a former space mission (Dawn) providing us with the ground truth that can be used as a benchmark.
Methods: We observed Vesta with VLT/SPHERE/ZIMPOL as part of our ESO large programme (ID 199.C-0074) at six different epochs, and deconvolved the collected images with a parametric point spread function (PSF). We then compared our images with synthetic views of Vesta generated from the 3D shape model of the Dawn mission, on which we projected Vesta's albedo information.
Results: We show that the deconvolution of the VLT/SPHERE images with a parametric PSF allows the retrieval of the main topographic and albedo features present across the surface of Vesta down to a spatial resolution of ~20-30 km. Contour extraction shows an accuracy of ~1 pixel (3.6 mas). The present study provides the very first quantitative estimate of the accuracy of ground-based adaptive-optics imaging observations of asteroid surfaces.
Conclusions: In the case of Vesta, the upcoming generation of 30-40 m telescopes (ELT, TMT, GMT) should in principle be able to resolve all of the main features present across its surface, including the troughs and the north-south crater dichotomy, provided that they operate at the diffraction limit.

Reduced images of Table A.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A6

Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 199.C-0074 (PI: P. Vernazza). Title: Homogeneous internal structure of CM-like asteroid (41) Daphne Authors: Carry, B.; Vachier, F.; Berthier, J.; Marsset, M.; Vernazza, P.; Grice, J.; Merline, W. J.; Lagadec, E.; Fienga, A.; Conrad, A.; Podlewska-Gaca, E.; Santana-Ros, T.; Viikinkoski, M.; Hanuš, J.; Dumas, C.; Drummond, J. D.; Tamblyn, P. M.; Chapman, C. R.; Behrend, R.; Bernasconi, L.; Bartczak, P.; Benkhaldoun, Z.; Birlan, M.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Drouard, A.; Ďurech, J.; Enke, B. L.; Fauvaud, S.; Ferrais, M.; Fetick, R.; Fusco, T.; Gillon, M.; Jehin, E.; Jorda, L.; Kaasalainen, M.; Keppler, M.; Kryszczynska, A.; Lamy, P.; Marchis, F.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B.; Zurlo, A. Bibcode: 2019A&A...623A.132C Altcode: 2019arXiv190101890C Context. CM-like asteroids (Ch and Cgh classes) are a major population within the broader C-complex, encompassing about 10% of the mass of the main asteroid belt. Their internal structure has been predicted to be homogeneous, based on their compositional similarity as inferred from spectroscopy and numerical modeling of their early thermal evolution.
Aims: Here we aim to test this hypothesis by deriving the density of the CM-like asteroid (41) Daphne from detailed modeling of its shape and the orbit of its small satellite.
Methods: We observed Daphne and its satellite within our imaging survey with the Very Large Telescope extreme adaptive-optics SPHERE/ZIMPOL camera and complemented this data set with earlier Keck/NIRC2 and VLT/NACO observations. We analyzed the dynamics of the satellite with our Genoid meta-heuristic algorithm. Combining our high-angular resolution images with optical lightcurves and stellar occultations, we determine the spin period, orientation, and 3D shape, using our ADAM shape modeling algorithm.
Results: The satellite orbits Daphne on an equatorial, quasi-circular, prograde orbit, like the satellites of many other large main-belt asteroids. The shape model of Daphne reveals several large flat areas that could be large impact craters. The mass determined from this orbit combined with the volume computed from the shape model implies a density for Daphne of 1.77 ± 0.26 g cm-3 (3 σ). This densityis consistent with a primordial CM-like homogeneous internal structure with some level of macroporosity (≈ 17%).
Conclusions: Based on our analysis of the density of Daphne and 75 other Ch/Cgh-type asteroids gathered from the literature, we conclude that the primordial internal structure of the CM parent bodies was homogeneous.

Based on observations made with (1) ESO Telescopes at the La Silla Paranal Observatory under programs http://281.C-5011 (PI Dumas), http://099.D-0098 (SPHERE GTO), and http://199.C-0074(A) (PI Vernazza); and (2) the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.The reduced and deconvolved AO images and the 3D shape model are publicly available at http://observations.lam.fr/astero/ and at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A132 Title: A catalog of stereo anaglyphs of the nucleus of comet 67P/Churyumov-Gerasimenko Authors: Lamy, Philippe; Faury, Guillaume; Romeuf, David; Groussin, Olivier; Durand, Joelle; Beigbeder, Laurent; Khum, Kea Bibcode: 2019arXiv190302324L Altcode: The OSIRIS/NAC camera onboard the Rosetta spacecraft acquired approximately 27000 images of comet 67PChuryumov-Gerasimenko at spatial scales down to a few centimeters. Numerous sequences of images separated by a few minutes suitable to stereo reconstruction allowed producing anaglyphs. They offer three-dimensional views complementary to other technics as a tool to understand the topography of the nucleus. Each one is documented by a set of 17 parameters. Over 1820 anaglyphs are available on a dedicated website at https://rosetta-3dcomet.cnes.fr Title: VizieR Online Data Catalog: VLT/SPHERE/ZIMPOL images of Vesta (Fetick+, 2019) Authors: Fetick, R. J.; Jorda, L.; Vernazza, P.; Marsset, M.; Drouard, A.; Fusco, T.; Carry, B.; Marchis, F.; Hanus, J.; Viikinkoski, M.; Birlan, M.; Bartczak, P.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dudzinski, G.; Dumas, C.; Ferrais, M.; Jehin, E.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Mugnier, L. M.; Neichel, B.; Pajuelo, M.; Podlewska-Gaca, E.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B. Bibcode: 2019yCat..36230006F Altcode: Vesta observations with VLT/SPHERE/ZIMPOL as part of the ESO large programme (ID 199.C-0074, PI: P.Vernazza) at six different epochs. The provided data is a set of images in FITS format, whose names correspond to the SPHERE observation times. Each image is of size 1024x1024 pixels. ESO header for each FITS provides information about the observation. Note that many observations are available for each of the six epochs.

object.dat : -------------------------------------------------------------------- Planet Name H Diam i e a mag km deg AU -------------------------------------------------------------------- 4 Vesta 3.20 468.3 7.141840 0.08874248 2.36126876

(2 data files). Title: The backscattering ratio of comet 67P/Churyumov-Gerasimenko dust coma as seen by OSIRIS onboard Rosetta Authors: Bertini, I.; La Forgia, F.; Fulle, M.; Tubiana, C.; Güttler, C.; Moreno, F.; Agarwal, J.; Munoz, O.; Mottola, S.; Ivanovsky, S.; Pajola, M.; Lucchetti, A.; Petropoulou, V.; Lazzarin, M.; Rotundi, A.; Bodewits, D.; Frattin, E.; Toth, I.; Masoumzadeh, N.; Kovacs, G.; Rinaldi, G.; Guirado, D.; Sierks, H.; Naletto, G.; Lamy, P.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Cambianica, P.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Ferrari, S.; Ferri, F.; Fornasier, S.; Gutierrez, P. J.; Hasselmann, P. H.; Ip, W. -H.; Keller, H. U.; Lara, L. M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Penasa, L.; Shi, X. Bibcode: 2019MNRAS.482.2924B Altcode: 2018MNRAS.tmp.2714B Remote sensing observations of dust particles ejected from comets provide important hints on the intimate nature of the materials composing these primitive objects. The measurement of dust coma backscattering ratio, BSR, defined as the ratio of the reflectance at phase angle 0° and 30°, helps tuning theoretical models aimed at solving the inverse scattering problem deriving information on the nature of the ejected particles. The Rosetta/OSIRIS camera sampled the coma phase function of comet 67P, with four series acquired at low phase angles from 2015 January to 2016 May. We also added previously published data to our analysis to increase the temporal resolution of our findings. We measured a BSR in the range ∼ [1.7-3.6], broader than the range found in literature from ground-based observations of other comets. We found that during the post-perihelion phase, the BSR is systematically larger than the classical cometary dust values only for nucleocentric distances smaller than ∼100 km. We explain this trend in terms of a cloud of chunks orbiting the nucleus at distances <100 km ejected during perihelion and slowly collapsing on the nucleus over a few months because of the coma gas drag. This also implies that the threshold particle size for the dust phase function to become similar to the nucleus phase function is between 2.5 mm and 0.1 m, taking into account previous Rosetta findings. Title: Three-Dimensional Views of the Nucleus of Comet 67P/Churyumov-Gerasimenko - Application to the Characterization of Active Pits Authors: Lamy, P.; Faury, G.; Romeuf, D.; Groussin, O.; Nebouy, D. Bibcode: 2018AGUFM.P23G3522L Altcode: The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's Rosetta spacecraft has acquired approximately 25000 images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at various spatial scales down to centimeters per pixel. The bulk of these images have been obtained in sequences and the combined displacement of the Rosetta orbiter along its trajectory and the rotation of the nucleus allow associating many pairs of images appropriate to stereoscopic viewing. This is achieved by constructing anaglyphs after rotating the images so that the relative shift appears horizontal. The shift is set to limit the parallax to approximately 2° (with a maximum value of 4°) for the foreground so as to avoid image deformation. A time of writing, approximately 1100 anaglyphs have been produced. In addition to offering spectacular stereoscopic views of the nucleus, these anaglyphs allow studying the topography of the nucleus at spatial scales unachievable by DTMs. Further coupling with spectral images, we have been able to locate ice patches at the bottom of several narrow pits which indicate the presence of sub-surface ice at depths of a few meters. These narrow pits are most likely the sources of collimated jets widely seen in the coma of 67PC-G. Title: Regional unit definition for the nucleus of comet 67P/Churyumov-Gerasimenko on the SHAP7 model Authors: Thomas, N.; El Maarry, M. R.; Theologou, P.; Preusker, F.; Scholten, F.; Jorda, L.; Hviid, S. F.; Marschall, R.; Kührt, E.; Naletto, G.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutièrrez, P. J.; Güttler, C.; Ip, W. H.; Keller, H. U.; Knollenberg, J.; Lara, L. M.; Lazzarin, M.; Lòpez-Moreno, J. J.; Marzari, F.; Tubiana, C.; Vincent, J. B. Bibcode: 2018P&SS..164...19T Altcode: The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified. Title: (16) Psyche: A mesosiderite-like asteroid? Authors: Viikinkoski, M.; Vernazza, P.; Hanuš, J.; Le Coroller, H.; Tazhenova, K.; Carry, B.; Marsset, M.; Drouard, A.; Marchis, F.; Fetick, R.; Fusco, T.; Ďurech, J.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Ferrais, M.; Grice, J.; Jehin, E.; Jorda, L.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Podlewska-Gaca, E.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B. Bibcode: 2018A&A...619L...3V Altcode: 2018arXiv181002771V Context. Asteroid (16) Psyche is the target of the NASA Psyche mission. It is considered one of the few main-belt bodies that could be an exposed proto-planetary metallic core and that would thus be related to iron meteorites. Such an association is however challenged by both its near- and mid-infrared spectral properties and the reported estimates of its density.
Aims: Here, we aim to refine the density of (16) Psyche to set further constraints on its bulk composition and determine its potential meteoritic analog.
Methods: We observed (16) Psyche with ESO VLT/SPHERE/ZIMPOL as part of our large program (ID 199.C-0074). We used the high angular resolution of these observations to refine Psyche's three-dimensional (3D) shape model and subsequently its density when combined with the most recent mass estimates. In addition, we searched for potential companions around the asteroid.
Results: We derived a bulk density of 3.99 ± 0.26 g cm-3 for Psyche. While such density is incompatible at the 3-sigma level with any iron meteorites (∼7.8 g cm-3), it appears fully consistent with that of stony-iron meteorites such as mesosiderites (density ∼4.25 g cm-3). In addition, we found no satellite in our images and set an upper limit on the diameter of any non-detected satellite of 1460 ± 200 m at 150 km from Psyche (0.2% × RHill, the Hill radius) and 800 ± 200 m at 2000 km (3% × RHill).
Conclusions: Considering that the visible and near-infrared spectral properties of mesosiderites are similar to those of Psyche, there is merit to a long-published initial hypothesis that Psyche could be a plausible candidate parent body for mesosiderites.

Based on observations made with 1) ESO Telescopes at the La Silla Paranal Observatory under programs 086.C-0785 (PI Carry) and 199.C-0074 (PI Vernazza); and 2) the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.Tables A1 and A2 and reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/L3 Title: Models of Rosetta/OSIRIS 67P Dust Coma Phase Function Authors: Moreno, F.; Guirado, D.; Muñoz, O.; Bertini, I.; Tubiana, C.; Güttler, C.; Fulle, M.; Rotundi, A.; Della Corte, V.; Ivanovski, S. L.; Rinaldi, G.; Bockelée-Morvan, D.; Zakharov, V. V.; Agarwal, J.; Mottola, S.; Toth, I.; Frattin, E.; Lara, L. M.; Gutiérrez, P. J.; Lin, Z. Y.; Kolokolova, L.; Sierks, H.; Naletto, G.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barucci, M. A.; Bertaux, J. -L.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Ip, W. -H.; Keller, H. U.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Shi, X. Bibcode: 2018AJ....156..237M Altcode: 2018arXiv180910424M The phase function of the dust coma of comet 67P has been determined from Rosetta/OSIRIS images. This function shows a deep minimum at phase angles near 100°, and a strong backscattering enhancement. These two properties cannot be reproduced by regular models of cometary dust, most of them based on wavelength-sized and randomly oriented aggregate particles. We show, however, that an ensemble of oriented elongated particles of a wide variety of aspect ratios, with radii r ≳ 10 μm, and whose long axes are perpendicular to the direction of the solar radiation, are capable of reproducing the observed phase function. These particles must be absorbing, with an imaginary part of the refractive index of about 0.1 to match the expected geometric albedo, and with porosity in the 60%-70% range. Title: VizieR Online Data Catalog: (16) Psyche images (Viikinkoski+, 2018) Authors: Viikinkoski, M.; Vernazza, P.; Hanus, J.; Le Coroller, H.; Tazhenova, K.; Carry, B.; Marsset, M.; Drouard, A.; Marchis, F.; Fetick, R.; Fusco, T.; Durech, J.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Ferrais, M.; Grice, J.; Jehin, E.; Jorda, L.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Podlewska-Gaca, E.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B. Bibcode: 2018yCat..36199003V Altcode: We observed Psyche with VLT/SPHERE/ZIMPOL at five different epochs, close to its opposition. The data reduction was performed as described in Vernazza et al. (2018, A&A, in press.).

(4 data files). Title: Periodic behaviour of coronal mass ejections, eruptive events, and solar activity proxies during solar cycles 23 and 24 Authors: Barlyaeva, Tatiana; Wojak, Julien; Lamy, Philippe; Boclet, Brice; Toth, Imre Bibcode: 2018JASTP.177...12B Altcode: 2017arXiv170402336B We report on the parallel analysis of the periodic behaviour of coronal mass ejections (CMEs) based on 21 years [1996-2016] of observations with the SOHO/LASCO-C2 coronagraph, solar flares, prominences, and several proxies of solar activity. We consider values of the rates globally and whenever possible, distinguish solar hemispheres and solar cycles 23 and 24. Periodicities are investigated using both frequency (periodogram) and time-frequency (wavelet) analysis. We find that these different processes, in addition to following the ≈11-year Solar Cycle, exhibit diverse statistically significant oscillations with properties common to all solar, coronal, and heliospheric processes: variable periodicity, intermittence, asymmetric development in the northern and southern solar hemispheres, and largest amplitudes during the maximum phase of solar cycles, being more pronounced during solar cycle 23 than the weaker cycle 24. However, our analysis reveals an extremely complex and diverse situation. For instance, there exists very limited commonality for periods of less than one year. The few exceptions are the periods of 3.1-3.2 months found in the global occurrence rates of CMEs and in the sunspot area (SSA) and those of 5.9-6.1 months found in the northern hemisphere. Mid-range periods of ≈1 and ≈2 years are more wide spread among the studied processes, but exhibit a very distinct behaviour with the first one being present only in the northern hemisphere and the second one only in the southern hemisphere. These periodic behaviours likely results from the complexity of the underlying physical processes, prominently the emergence of magnetic flux. Title: The impact crater at the origin of the Julia family detected with VLT/SPHERE? Authors: Vernazza, P.; Brož, M.; Drouard, A.; Hanuš, J.; Viikinkoski, M.; Marsset, M.; Jorda, L.; Fetick, R.; Carry, B.; Marchis, F.; Birlan, M.; Fusco, T.; Santana-Ros, T.; Podlewska-Gaca, E.; Jehin, E.; Ferrais, M.; Bartczak, P.; Dudziński, G.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Ďurech, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.; Vachier, F.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B.; Asphaug, E.; Richardson, D. C.; Ševeček, P.; Gillon, M.; Benkhaldoun, Z. Bibcode: 2018A&A...618A.154V Altcode: Context. The vast majority of the geophysical and geological constraints (e.g., internal structure, cratering history) for main-belt asteroids have so far been obtained via dedicated interplanetary missions (e.g., ESA Rosetta, NASA Dawn). The high angular resolution of SPHERE/ZIMPOL, the new-generation visible adaptive-optics camera at ESO VLT, implies that these science objectives can now be investigated from the ground for a large fraction of D ≥ 100 km main-belt asteroids. The sharp images acquired by this instrument can be used to accurately constrain the shape and thus volume of these bodies (hence density when combined with mass estimates) and to characterize the distribution and topography of D ≥ 30 km craters across their surfaces.
Aims: Here, via several complementary approaches, we evaluated the recently proposed hypothesis that the S-type asteroid (89) Julia is the parent body of a small compact asteroid family that formed via a cratering collisional event.
Methods: We observed (89) Julia with VLT/SPHERE/ZIMPOL throughout its rotation, derived its 3D shape, and performed a reconnaissance and characterization of the largest craters. We also performed numerical simulations to first confirm the existence of the Julia family and to determine its age and the size of the impact crater at its origin. Finally, we utilized the images/3D shape in an attempt to identify the origin location of the small collisional family.
Results: On the one hand, our VLT/SPHERE observations reveal the presence of a large crater (D ~ 75 km) in Julia's southern hemisphere. On the other hand, our numerical simulations suggest that (89) Julia was impacted 30-120 Myrs ago by a D ~ 8 km asteroid, thereby creating a D ≥ 60 km impact crater at the surface of Julia. Given the small size of the impactor, the obliquity of Julia and the particular orientation of the family in the (a,i) space, the imaged impact crater is likely to be the origin of the family.
Conclusions: New doors into ground-based asteroid exploration, namely, geophysics and geology, are being opened thanks to the unique capabilities of VLT/SPHERE. Also, the present work may represent the beginning of a new era of asteroid-family studies. In the fields of geophysics, geology, and asteroid family studies, the future will only get brighter with the forthcoming arrival of 30-40 m class telescopes like ELT, TMT, and GMT.

Based on observations made with ESO Telescopes at the Paranal Observatory under program ID 199.C-0074 (PI: P. Vernazza).

The reduced images are only available available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A154 Title: On deviations from free-radial outflow in the inner coma of comet 67P/Churyumov-Gerasimenko Authors: Gerig, S. -B.; Marschall, R.; Thomas, N.; Bertini, I.; Bodewits, D.; Davidsson, B.; Fulle, M.; Ip, W. -H.; Keller, H. U.; Küppers, M.; Preusker, F.; Scholten, F.; Su, C. C.; Toth, I.; Tubiana, C.; Wu, J. -S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Vincent, J. -B. Bibcode: 2018Icar..311....1G Altcode: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard the European Space Agency's Rosetta spacecraft acquired images of comet 67P/Churyumov-Gerasimenko (67P) and its surrounding dust coma starting from May 2014 until September 2016. In this paper we present methods and results from analysis of OSIRIS images regarding the dust outflow in the innermost coma of 67P. The aim is to determine the global dust outflow behaviour and place constraints on physical processes affecting particles in the inner coma. We study the coma region right above the nucleus surface, spanning from the nucleus centre out to a distance of about 50 km comet centric distance (approximately 25 average comet radii). We primarily adopt an approach used by Thomas and Keller (1990) to study the dust outflow. We present the effects on azimuthally-averaged values of the dust reflectance of non-radial flow and non-point-source geometry, acceleration of dust particles, sublimation of icy dust particles after ejection from the surface, dust particle fragmentation, optical depth effects and the influence of gravitationally bound particles. All of these physical processes could modify the observed distribution of light scattered by the dust coma.

In the image analysis, profiles of azimuthally averaged dust brightness as a function of impact parameter b (azimuthal average, "Ā-curve") were fitted with a simple function that best fits the shape of our profile curves (f(b ; u , v , w , z) = u /bv + wb + z). The analytical fit parameters (u, v, w, z), which hold the key information about the dust outflow behaviour, were saved in a comprehensive database.

Through statistical analysis of these information, we show that the spatial distribution of dust follows free-radial outflow behaviour (i.e. force-free radial outflow with constant velocity) beyond distances larger than ∼11.9 km from the comet centre, which corresponds to a relative distance of about 6 average comet radii from the comet centre. Hence, we conclude that beyond this distance, and on average, fragmentation and gravitationally bound particles are negligible processes in determining the optically scattered light distribution in the innermost coma. Closer to the nucleus we observe dust outflow behaviour that deviates from free-radial outflow.

A comparison of our result profiles with numerical models using a Direct Simulation Monte Carlo (DSMC) approach with dust particle distributions calculated using a test particle approach has been used to demonstrate the influence of a complex shape and particle acceleration on the azimuthal average profiles. We demonstrate that, while other effects such as fragmentation or sublimation of dust particles cannot be ruled out, acceleration of the dust particles and effects arising from the shape of the irregular nucleus (non-point source geometry) are sufficient to explain the observed dust outflow behaviour from image data analysis.

As a by-product of this work, we have calculated "Afρ" values for the 1/r regime. We found a peak in the coma activity in terms of Afρ (normalised to a phase angle of 90°) of ∼210 cm 20 days after perihelion. Furthermore, based on simplified models of particle motion within bound orbits, it is shown that limits on the total cross-sectional area of bound particles might be derived through further analysis. An example is given. Title: The big lobe of 67P/Churyumov-Gerasimenko comet: morphological and spectrophotometric evidences of layering as from OSIRIS data Authors: Ferrari, Sabrina; Penasa, L.; La Forgia, F.; Massironi, M.; Naletto, G.; Lazzarin, M.; Fornasier, S.; Hasselmann, P. H.; Lucchetti, A.; Pajola, M.; Ferri, F.; Cambianica, P.; Oklay, N.; Tubiana, C.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Davidsson, B.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Franceschi, M.; Frattin, E.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Küppers, M.; Lara, L. M.; López-Moreno, J. J.; Marzari, F.; Shi, X.; Simioni, E.; Thomas, N.; Vincent, J. -B. Bibcode: 2018MNRAS.479.1555F Altcode: 2018MNRAS.tmp.1575F Between 2014 and 2016, ESA's Rosetta OSIRIS cameras acquired multiple-filters images of the layered nucleus of comet 67P/Churyumov-Gerasimenko, ranging from ultraviolet to near-infrared wavelengths. No correlation between layers disposition and surface spectral variegation has been observed so far. This paper investigates possible spectral differences among decametre-thickness outcropping layers of the biggest lobe of the comet by means of OSIRIS image dataset. A two-classes maximum likelihood classification was applied on consolidated outcrops and relative deposits identified on post-perihelion multispectral images of the big lobe. We distinguished multispectral data on the basis of the structural elevation of the onion-shell Ellipsoidal Model of 67P. The spatial distribution of the two classes displays a clear dependence on the structural elevation, with the innermost class resulting over 50 per cent brighter than the outermost one. Consolidated cometary materials located at different structural levels are characterized by different brightness and revealed due to the selective removal of large volumes. This variegation can be attributed to a different texture of the outcrop surface and/or to a different content of refractory materials. Title: Evidence of cool prominence material embedded in CMEs from polarization measurements Authors: Lamy, Philippe; Floyd, Olivier; Koutchmy, Serge Bibcode: 2018cosp...42E1930L Altcode: In white-light coronagraph images, cool prominence material is sometimes observed as bright substructures or plasmoids in coronal mass ejections (CMEs). Based on observations of a CME with the SECCHI/STEREO coronagraphs on 31 August 2007, Mierla et al. (2011) have shown that the emission from such bright patches is characterized by very low polarization and was due to H-alpha radiation from cool prominence material. We have examined several polarization images of CMEs obtained with the LASCO-C2 coronagraph with its orange filter. This filter is approximately centered on the HeI D3 line. This low excitation line emission is superior to the H-alpha emission of HI because its FIP is much higher. In several cases, we observe very low-polarization components embedded in CMEs characterized by a much larger polarization resulting from the Thomson scattering. They most likely present evidence of cool prominence material carried by the CMEs. Title: VizieR Online Data Catalog: SPHERE/ZIMPOL (89) Julia images (Vernazza+, 2018) Authors: Vernazza, P.; Brozv, M.; Drouard, A.; Hanusv, J.; Viikinkoski, M.; Marsset, M.; Jorda, L.; Fetick, R.; Carry, B.; Marchis, F.; Birlan, M.; Fusco, T.; Santana-Ros, T.; Podlewska-Gaca, E.; Jehin, E.; Ferrais, M.; Bartczak, P.; Dudzinski, G.; Berthier, J.; Castillo-Rogez, J.; Cipriani, F.; Colas, F.; Dumas, C.; Durech, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Le Coroller, H.; Marciniak, A.; Michalowski, T.; Michel, P.; Pajuelo, M.; Tanga, P.; Vachier, F.; Vigan, A.; Warner, B.; Witasse, O.; Yang, B.; Asphaug, E.; Richardson, D. C.; Svevevek, P.; Gillon, M.; Benkhaldoun, Z. Bibcode: 2018yCat..36180154V Altcode: Julia was observed with the SPHERE instrument (ESO/VLT) around its opposition at eight different epochs. We used ZIMPOL in narrowband imaging mode (N_R filter; filter central wavelength = 645.9nm, width = 56.7nm). Each observational sequence consisted of a series of five images, where each image corresponded to a series of detector integration times (DITs) of 10s, during which Julia was used as a natural guide star for adaptive optics (AO) corrections. Observations were performed under good seeing conditions (<=0.8") with an airmass usually below 1.6. After every asteroid observation, we observed a nearby star for deconvolution purposes to estimate the instrument point spread function (PSF). Finally, standard calibrations, which include detector flat-fields and darks, were acquired in the morning as part of the instrument calibration plan.

objects: ------------------------------------------------------------------- Planet Name H Diam i e a mag km deg AU ------------------------------------------------------------------- 89 Julia 6.60 151.5 16.127006 0.18459430 2.55051892 -------------------------------------------------------------------

(2 data files). Title: Three-Dimensional Views of the Nucleus of Comet 67P/Churyumov-Gerasimenko - Application to the Characterization of Active Pits Authors: Lamy, Philippe; Groussin, Olivier; Faury, Guillaume; Romeuf, David; Nebouy, David Bibcode: 2018cosp...42E1928L Altcode: The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's Rosetta spacecraft has acquired approximately 25000 images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at various spatial scales down to centimeters per pixel. The bulk of these images have been obtained in sequences and the combined displacement of the Rosetta orbiter along its trajectory and the rotation of the nucleus allow associating many pairs of images appropriate to stereoscopic viewing. This is achieved by constructing anaglyphs after rotating the images so that the relative shift appears horizontal. The shift is set to limit the parallax to approximately 2° (with a maximum value of 4°) for the foreground so as to avoid image deformation. A time of writing, approximately 1000 anaglyphs have been produced. In addition to offering spectacular stereoscopic views of the nucleus, these anaglyphs allow studying the topography of the nucleus at spatial scales unachievable by DTMs. Further coupling with spectral images, we have been able to locate ice patches at the bottom of several narrow pits which indicate the presence of sub-surface ice at depths of a few meters. These narrow pits are most likely the sources of collimated jets widely seen in the coma of 67PC-G. Title: Three-Dimensional Shape Reconstruction and Propagation of the CME of 22 October 2003 from LASCO Images Authors: Lamy, Philippe Bibcode: 2018cosp...42E1929L Altcode: The determination of the three-dimensional morphology and propagation of coronal mass ejections (CMEs) in coronagraphic white-light images has been a major question of coronal physics, and a challenge to the observers. The STEREO mission has so far provided the required two view points for stereoscopic reconstruction but that capability has ended with the loss of one of the S/C. Two-dimensional images as provided by the LASCO-C2 and C3 coronagraphs are generally insufficientto provide anything more than an idea of the global and internal structures of a CME. There are however favorable cases where the relatively simple morphology of a CME and the geometry of the observations allow perceiving its global shape. In those cases, forward modeling based on an a-priori shape model can be attempted, and the resulting synthetic images are compared and fitted to the observations. We present the case of the CME detected and tracked by LASCO on 22 October 2003 which is amenable to such an approach. The global shape of this CME on the images however requires the introduction of an elaborated shape model, an asymmetric plasma cloud. The images are first processed in order to remove most of the background or foreground coronal structures (essentially streamers) which are superimposed on the CME. Using the cloud model, we generate synthetic images that are fitted to the observed images. The resulting parameters allow a detailed characterization of the 3D shape and propagation of the CME. Title: Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs (Corrigendum) Authors: Attree, N.; Groussin, O.; Jorda, L.; Nébouy, D.; Thomas, N.; Brouet, Y.; Kührt, E.; Preusker, F.; Scholten, F.; Knollenberg, J.; Hartogh, P.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.; Kovacs, G.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Lowry, S.; Marchi, S.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Toth, I.; Tubiana, C.; Vincent, J. -B.; Shi, X. Bibcode: 2018A&A...614C...2A Altcode: No abstract at ADS Title: Coma morphology of comet 67P controlled by insolation over irregular nucleus Authors: Shi, X.; Hu, X.; Mottola, S.; Sierks, H.; Keller, H. U.; Rose, M.; Güttler, C.; Fulle, M.; Fornasier, S.; Agarwal, J.; Pajola, M.; Tubiana, C.; Bodewits, D.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Toth, I.; Vincent, J. -B. Bibcode: 2018NatAs...2..562S Altcode: 2018NatAs.tmp...59S While the structural complexity of cometary comae is already recognizable from telescopic observations1, the innermost region, within a few radii of the nucleus, was not resolved until spacecraft exploration became a reality2,3. The dust coma displays jet-like features of enhanced brightness superposed on a diffuse background1,4,5. Some features can be traced to specific areas on the nucleus, and result conceivably from locally enhanced outgassing and/or dust emission6-8. However, diffuse or even uniform activity over topographic concavity can converge to produce jet-like features9,10. Therefore, linking observed coma morphology to the distribution of activity on the nucleus is difficult11,12. Here, we study the emergence of dust activity at sunrise on comet 67P/Churyumov-Gerasimenko using high-resolution, stereo images from the OSIRIS camera onboard the Rosetta spacecraft, where the sources and formation of the jet-like features are resolved. We perform numerical simulations to show that the ambient dust coma is driven by pervasive but non-uniform water outgassing from the homogeneous surface layer. Physical collimations of gas and dust flows occur at local maxima of insolation and also via topographic focusing. Coma structures are projected to exhibit jet-like features that vary with the perspective of the observer. For an irregular comet such as 67P/Churyumov-Gerasimenko, near-nucleus coma structures can be concealed in the shadow of the nucleus, which further complicates the picture. Title: The phase function and density of the dust observed at comet 67P/Churyumov-Gerasimenko Authors: Fulle, Marco; Bertini, I.; Della Corte, V.; Güttler, C.; Ivanovski, S.; La Forgia, F.; Lasue, J.; Levasseur-Regourd, A. C.; Marzari, F.; Moreno, F.; Mottola, S.; Naletto, G.; Palumbo, P.; Rinaldi, G.; Rotundi, A.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.; Bertaux, J. -L.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Groussin, O.; Gutiérrez, P. J.; Hviid, H. S.; Ip, W. H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, M. L.; Lazzarin, M.; López-Moreno, J. J.; Shi, X.; Thomas, N.; Tubiana, C. Bibcode: 2018MNRAS.476.2835F Altcode: 2018MNRAS.tmp..454F The OSIRIS camera onboard Rosetta measured the phase function of both the coma dust and the nucleus. The two functions have a very different slope versus the phase angle. Here, we show that the nucleus phase function should be adopted to convert the brightness to the size of dust particles larger than 2.5 mm only. This makes the dust bursts observed close to Rosetta by OSIRIS, occurring about every hour, consistent with the fragmentation on impact with Rosetta of parent particles, whose flux agrees with the dust flux observed by GIADA. OSIRIS also measured the antisunward acceleration of the fragments, thus providing the first direct measurement of the solar radiation force acting on the dust fragments and thus of their bulk density, excluding any measurable rocket effect by the ice sublimation from the dust. The obtained particle density distribution has a peak matching the bulk density of most COSIMA particles, and represents a subset of the density distribution measured by GIADA. This implies a bias in the elemental abundances measured by COSIMA, which thus are consistent with the 67P dust mass fractions inferred by GIADA, i.e. (38 ± 8) {per cent} of hydrocarbons versus the (62 ± 8) {per cent} of sulphides and silicates. Title: Exposed bright features on the comet 67P/Churyumov-Gerasimenko: distribution and evolution Authors: Deshapriya, J. D. P.; Barucci, M. A.; Fornasier, S.; Hasselmann, P. H.; Feller, C.; Sierks, H.; Lucchetti, A.; Pajola, M.; Oklay, N.; Mottola, S.; Masoumzadeh, N.; Tubiana, C.; Güttler, C.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hoang, H. V.; Hviid, S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Preusker, F.; Shi, X.; Thomas, N.; Vincent, J. -B. Bibcode: 2018A&A...613A..36D Altcode: Context. Since its arrival at the comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft followed the comet as it went past the perihelion and beyond until September 2016. During this time there were many scientific instruments operating on board Rosetta to study the comet and its evolution in unprecedented detail. In this context, our study focusses on the distribution and evolution of exposed bright features that have been observed by OSIRIS, which is the scientific imaging instrument aboard Rosetta.
Aims: We envisage investigating various morphologies of exposed bright features and the mechanisms that triggered their appearance.
Methods: We co-registered multi-filter observations of OSIRIS images that are available in reflectance. The Lommel-Seeliger disk function was used to correct for the illumination conditions and the resulting colour cubes were used to perform spectrophotometric analyses on regions of interest.
Results: We present a catalogue of 57 exposed bright features observed on the nucleus of the comet, all of which are attributed to the presence of H2O ice on the comet. Furthermore, we categorise these patches under four different morphologies and present geometric albedos for each category.
Conclusions: Although the nucleus of 67P/Churyumov-Gerasimenko appears to be dark in general, there are localised H2O ice sources on the comet. Cometary activity escalates towards the perihelion passage and reveals such volatile ices. We propose that isolated H2O ice patches found in smooth terrains in regions, such as Imhotep, Bes, and Hapi, result from frost as an aftermath of the cessation of the diurnal water cycle on the comet as it recedes from perihelion. Upon the comet's return to perihelion, such patches are revealed when sublimation-driven erosion removes the thin dust layers that got deposited earlier. More powerful activity sources such as cometary outbursts are capable of revealing much fresher, less contaminated H2O ice that is preserved with consolidated cometary material, as observed on exposed patches resting on boulders. This is corroborated by our albedo calculations that attribute higher albedos for bright features with formations related to outbursts. Title: Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs Authors: Attree, N.; Groussin, O.; Jorda, L.; Nébouy, D.; Thomas, N.; Brouet, Y.; Kührt, E.; Preusker, F.; Scholten, F.; Knollenberg, J.; Hartogh, P.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.; Kovacs, G.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Lowry, S.; Marchi, S.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Toth, I.; Tubiana, C.; Vincent, J. -B.; Shi, X. Bibcode: 2018A&A...611A..33A Altcode: 2017arXiv171207508A We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features andthe implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the 10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km). Title: Meter-scale thermal contraction crack polygons on the nucleus of comet 67P/Churyumov-Gerasimenko Authors: Auger, A. -T.; Groussin, O.; Jorda, L.; El-Maarry, M. R.; Bouley, S.; Séjourné, A.; Gaskell, R.; Capanna, C.; Davidsson, B.; Marchi, S.; Höfner, S.; Lamy, P. L.; Sierks, H.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol, A.; Sabau, L.; Thomas, N.; Tubiana, C.; Vincent, J. -B.; Wenzel, K. -P. Bibcode: 2018Icar..301..173A Altcode: We report on the detection and characterization of more than 6300 polygons on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, using images acquired by the OSIRIS camera onboard Rosetta between August 2014 and March 2015. They are found in consolidated terrains and grouped in localized networks. They are present at all latitudes (from North to South) and longitudes (head, neck, and body), sometimes on pit walls or following lineaments. About 1.5% of the observed surface is covered by polygons. Polygons have an homogeneous size across the nucleus, with 90% of them in the size range 1 - 5 m and a mean size of 3.0 ± 1.4 m. They show different morphologies, depending on the width and depth of their trough. They are found in networks with 3- or 4-crack intersection nodes. The polygons observed on 67P are consistent with thermal contraction crack polygons formed by the diurnal or seasonal temperature variations in a hard (MPa) and consolidated sintered layer of water ice, located a few centimeters below the surface. Our thermal analysis shows an evolution of thermal contraction crack polygons according to the local thermal environment, with more evolved polygons (i.e. deeper and larger troughs) where the temperature and the diurnal and seasonal temperature range are the highest. Thermal contraction crack polygons are young surface morphologies that probably formed after the injection of 67P in the inner solar system, typically 100,000 years ago, and could be as young as a few orbital periods, following the decreasing of its perihelion distance in 1959 from 2.7 to 1.3 a.u. Meter scale thermal contraction crack polygons should be common features on the nucleus of Jupiter family comets. Title: Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko Authors: Höfner, S.; Vincent, J. -B.; Blum, J.; Davidsson, B. J. R.; Sierks, H.; El-Maarry, M. R.; Deller, J.; Hofmann, M.; Hu, X.; Pajola, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marqués, P.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Michalik, H.; Moissl-Fraund, R.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.; Zitzmann, S. Bibcode: 2017A&A...608A.121H Altcode: Context. The camera OSIRIS on board Rosetta obtained high-resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great parts of the nucleus surface are composed of fractured terrain.
Aims: Fracture formation, evolution, and their potential relationship to physical processes that drive activity are not yet fully understood. Observed temperatures and gas production rates can be explained or interpreted with the presence of fractures by applying appropriate modelling methods.
Methods: We followed a transient thermophysical model approach that includes radiative, conductive, and water-ice sublimation fluxes by considering a variety of heliocentric distances, illumination conditions, and thermophysical properties for a set of characteristic fracture geometries on the nucleus of 67P. We computed diurnal temperatures, heat fluxes, and outgassing behaviour in order to derive and distinguish the influence of the mentioned parameters on fractured terrain.
Results: Our analysis confirms that fractures, as already indicated by former studies about concavities, deviate from flat-terrain topographies with equivalent properties, mostly through the effect of self-heating. Compared to flat terrain, illuminated cometary fractures are generally warmer, with smaller diurnal temperature fluctuations. Maximum sublimation rates reach higher peaks, and dust mantle quenching effects on sublimation rates are weaker. Consequently, the rough structure of the fractured terrain leads to significantly higher inferred surface thermal inertia values than for flat areas with identical physical properties, which might explain the range of measured thermal inertia on 67P.
Conclusions: At 3.5 AU heliocentric distance, sublimation heat sinks in fractures converge to maximum values >50 W / m2 and trigger dust activity that can be related mainly to H2O. Fractures are likely to grow through the erosive interplay of alternating sublimation and thermal fatigue. Title: Anomalous Surge of the White-Light Corona at the Onset of the Declining Phase of Solar Cycle 24 Authors: Lamy, P. Bibcode: 2017AGUFMSH13A2465L Altcode: In late 2014, when the current solar cycle 24 was initiating its declining phase, the white-light corona as observed by the LASCO-C2 coronagraph underwent an unexpected surge that increased its global radiance by 60%, reaching a peak value comparable to those of the more active solar cycle 23. The daily variations point to a localized enhancement or bulge in the electron density that persisted during several months. Carrington maps of the radiance and of the HMI photospheric field allow connecting this bulge to the emergence of the large sunspot complex AR 12192 in October 2014, the largest since AR 6368 observed in November 1990. The resulting unusually large increase of the magnetic field and the distortion of the neutral sheet in a characteristic inverse S-shape caused the coronal plasma to be trapped along a similar pattern. Three-dimensional reconstruction of the electron density based on time-dependent solar rotational tomography supplemented by 2D inversion of the coronal radiance confirms the morphology of the bulge and reveals that its level was well above the standard models of a corona of the maximum type, by typically a factor of 3. A rather satisfactory agreement is found with the results of the thermodynamic MHD model produced by Predictive Sciences although discrepancies are noted. The specific configuration of the magnetic field that led to the coronal surge resulted from the interplay of various factors prevailing at the onset of the declining phase of the solar cycles which was particularly efficient in the case of solar cycle 24. Title: ASPIICS: a giant, white light and emission line coronagraph for the ESA proba-3 formation flight mission Authors: Lamy, P. L.; Vivès, S.; Curdt, W.; Damé, L.; Davila, J.; Defise, J. -M.; Fineschi, S.; Heinzel, P.; Howard, Russel; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Zhukov, A. Bibcode: 2017SPIE10565E..0TL Altcode: Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent useful observations of the white light corona inside typically 2-2.5 solar radii (Rsun). Formation flying offers and elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at a distance of hundred meters [1, 2]. Such an instrument ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) has been selected by the European Space Agency (ESA) to fly on its PROBA-3 mission of formation flying demonstration which is presently in phase B (Fig. 1). The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.04 solar radii from the solar limb. By tuning the position of the occulter spacecraft, it may even be possible to reach the chromosphere and the upper part of the spicules [3]. ASPIICS will perform (i) high spatial resolution imaging of the continuum K+F corona in photometric and polarimetric modes, (ii) high spatial resolution imaging of the E-corona in two coronal emission lines (CEL): Fe XIV and He I D3, and (iii) two-dimensional spectrophotometry of the Fe XIV emission line. ASPIICS will address the question of the coronal heating and the role of waves by characterizing propagating fluctuations (waves and turbulence) in the solar wind acceleration region and by looking for oscillations in the intensity and Doppler shift of spectral lines. The combined imaging and spectral diagnostics capabilities available with ASPIICS will allow mapping the velocity field of the corona both in the sky plane (directly on the images) and along the line-of-sight by measuring the Doppler shifts of emission lines in an effort to determine how the different components of the solar wind, slow and fast are accelerated. With a possible launch in 2014, ASPIICS will observe the corona during the maximum of solar activity, insuring the detection of many Coronal Mass Ejections (CMEs). By rapidly alternating high-resolution imaging and spectroscopy, CMEs will be thoroughly characterized. Title: ASPIICS/PROBA-3 formation flying solar coronagraph: Stray light analysis and optimization of the occulter Authors: Landini, F.; Mazzoli, A.; Venet, M.; Vivès, S.; Romoli, M.; Lamy, P.; Massone, G. Bibcode: 2017SPIE10565E..1RL Altcode: The "Association de Satellites Pour l'Imagerie et l'Interferometrie de la Couronne Solaire", ASPIICS, selected by ESA for the PROBA-3 mission, heralds the next generation of coronagraph for solar research, exploiting formation flying to gain access to the inner corona under eclipse-like conditions for long periods of time. A detailed description of the ASPIICS instrument and of its scientific objectives can be found in [1]. ASPIICS is distributed on the two PROBA 3 spacecrafts (S/C) separated by 150 m. The coronagraph optical assembly is hosted by the "coronagraph S/C" protected from direct solar disk light by the occulting disk on the "occulter S/C". The most critical issue in the design of a solar coronagraph is the reduction of the stray light due to the diffraction and scattering of the solar disk light by the occulter, the aperture and the optics. In the present article, we deal with two of these issues: - The analysis of the stray light inside the telescope. - The optimization of the external occulter edge, in order to eliminate the Poisson spot behind the occulter and to lower the stray light level going through the entrance pupil of the telescope. This work was performed in the framework of the ESA STARTIGER program which took place at the Laboratoire d'Astrophysique de Marseille (LAM) during a 6-month period from September 2009 to March 2010. In general, it is a very complicated task to combine the above two stray light issues together in the simulation and design phase as it requires to consider the propagation inside the telescope of the light diffracted by the external occulter. Actually, the present literature only reports diffraction calculations performed for simple occulting systems (i.e., two disks and serrated disk). A more pragmatic approach, also driven by the tight schedule of the STARTIGER program, is to separate the two contributions, and perform two different stray light analyses. This paper is dedicated to the description of both analyses: in particular, the first part is dedicated to the evaluation of the stray light inside the telescope, assuming a simple disk as occulter, and a preliminary baffle design is presented; the second part describes the investigation on the geometry of the external occulter, with a detailed description of the laboratory setup that has been designed and implemented to compare together several types of occulting systems. Title: METIS, the Multi Element Telescope for Imaging and Spectroscopy: an instrument proposed for the solar orbiter mission Authors: Antonucci, E.; Andretta, V.; Cesare, S.; Ciaravella, A.; Doschek, G.; Fineschi, S.; Giordano, S.; Lamy, P.; Moses, D.; Naletto, G.; Newmark, J.; Poletto, L.; Romoli, M.; Solanki, S.; Spadaro, D.; Teriaca, L.; Zangrilli, L. Bibcode: 2017SPIE10566E..0LA Altcode: METIS, the Multi Element Telescope for Imaging and Spectroscopy, is an instrument proposed to the European Space Agency to be part of the payload of the Solar Orbiter mission. The instrument design has been conceived for performing extreme ultraviolet (EUV) spectroscopy both on the solar disk and off-limb, and near-Sun coronagraphy and spectroscopy. The proposed instrument suite consists of three different interconnected elements, COR, EUS and SOCS, sharing the same optical bench, electronics, and S/C heat shield aperture. COR is a visible-EUV multiband coronagraph based on a classical externally occulted design. EUS is the component of the METIS EUV disk spectrometer which includes the telescope and all the related mechanisms. Finally, SOCS is the METIS spectroscopic component including the dispersive system and the detectors. The capability of inserting a small telescope collecting coronal light has been added to perform also EUV coronal spectroscopy. METIS can simultaneously image the visible and ultraviolet emission of the solar corona and diagnose, with unprecedented temporal coverage and space resolution the structure and dynamics of the full corona in the range from 1.2 to 3.0 (1.6 to 4.1) solar radii (R⊙, measured from Sun centre) at minimum (maximum) perihelion during the nominal mission. It can also perform spectroscopic observations of the solar disk and out to 1.4 R⊙ within the 50-150 nm spectral region, and of the geo-effective coronal region 1.7-2.7 R⊙ within the 30-125 nm spectral band. Title: Preliminary calibration results of the wide angle camera of the imaging instrument OSIRIS for the Rosetta mission Authors: Da Deppo, V.; Naletto, G.; Nicolosi, P.; Zambolin, P.; De Cecco, M.; Debei, S.; Parzianello, G.; Ramous, P.; Zaccariotto, M.; Fornasier, S.; Verani, S.; Thomas, N.; Barthol, P.; Hviid, S. F.; Sebastian, I.; Meller, R.; Sierks, H.; Keller, H. U.; Barbieri, C.; Angrilli, F.; Lamy, P.; Rodrigo, R.; Rickman, H.; Wenzel, K. P. Bibcode: 2017SPIE10568E..0ND Altcode: Rosetta is one of the cornerstone missions of the European Space Agency for having a rendezvous with the comet 67P/Churyumov-Gerasimenko in 2014. The imaging instrument on board the satellite is OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System), a cooperation among several European institutes, which consists of two cameras: a Narrow (NAC) and a Wide Angle Camera (WAC). The WAC optical design is an innovative one: it adopts an all reflecting, unvignetted and unobstructed two mirror configuration which allows to cover a 12° × 12° field of view with an F/5.6 aperture and gives a nominal contrast ratio of about 10-4. The flight model of this camera has been successfully integrated and tested in our laboratories, and finally has been integrated on the satellite which is now waiting to be launched in February 2004. In this paper we are going to describe the optical characteristics of the camera, and to summarize the results so far obtained with the preliminary calibration data. The analysis of the optical performance of this model shows a good agreement between theoretical performance and experimental results. Title: Preliminary optical design of the coronagraph for the ASPIICS formation flying mission Authors: Vivès, S.; Lamy, P.; Saisse, M.; Boit, J. -L.; Koutchmy, S. Bibcode: 2017SPIE10567E..1WV Altcode: Formation flyers open new perspectives and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at approximately 100-150 m from the first one. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interfromtrie de la Couronne Solaire) is a mission proposed to ESA in the framework of the PROBA-3 program of formation flying which is presently in phase A to exploit this technique for coronal observations. ASPIICS is composed of a single coronagraph which performs high spatial resolution imaging of the corona as well as 2-dimensional spectroscopy of several emission lines from the coronal base out to 3 R. The selected lines allow to address different coronal regions: the forbidden line of Fe XIV at 530.285 nm (coronal matter), Fe IX/X at 637.4 nm (coronal holes), HeI at 587.6 nm (cold matter). An additional broad spectral channel will image the white light corona so as to derive electron densities. The classical design of an externally occulted coronagraph is adapted to the detection of the very inner corona as close as 1.01 R and the addition of a Fabry-Perot interferometer using a so-called "etalon". This paper is dedicated to the description of the optical design and its critical components: the entrance optics and the FabryPerot interferometer. Title: Stray light rejection in giant externally-occulted solar coronagraphs: experimental developments Authors: Venet, M.; Bazin, C.; Koutchmy, S.; Lamy, P. Bibcode: 2017SPIE10565E..1WV Altcode: The advent of giant, formation-flight, externally-occulted solar coronagraphs such as ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire [1,2,3,4]) selected by the European Space Agency (ESA) for its third PROBA (Project for On-Board Autonomy) mission of formation flying demonstration (presently in phase B) and Hi-RISE proposed in the framework of ESA Cosmic Vision program, presents formidable challenges for the study and calibration of instrumental stray light. With distances between the external occulter (EO) and the optical pupil (OP) exceeding hundred meters and occulter sizes larger than a meter, it becomes impossible to perform tests at the real scale. The requirement to limit the over-occultation to less than 1.05 Rsun, orders of magnitude to what has been achieved so far in past coronagraphs, further adds to the challenge. We are approaching the problem experimentally using reduced scale simulators and present below a progress report of our work. Title: The global meter-level shape model of comet 67P/Churyumov-Gerasimenko Authors: Preusker, F.; Scholten, F.; Matz, K. -D.; Roatsch, T.; Hviid, S. F.; Mottola, S.; Knollenberg, J.; Kührt, E.; Pajola, M.; Oklay, N.; Vincent, J. -B.; Davidsson, B.; A'Hearn, M. F.; Agarwal, J.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Koschny, D.; Kramm, J. R.; Küppers, M.; Lamy, P.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sierks, H.; Thomas, N.; Tubiana, C. Bibcode: 2017A&A...607L...1P Altcode: We performed a stereo-photogrammetric (SPG) analysis of more than 1500 Rosetta/OSIRIS NAC images of comet 67P/Churyumov-Gerasimenko (67P). The images with pixel scales in the range 0.2-3.0 m/pixel were acquired between August 2014 and February 2016. We finally derived a global high-resolution 3D description of 67P's surface, the SPG SHAP7 shape model. It consists of about 44 million facets (1-1.5 m horizontal sampling) and a typical vertical accuracy at the decimeter scale. Although some images were taken after perihelion, the SPG SHAP7 shape model can be considered a pre-periheliondescription and replaces the previous SPG SHAP4S shape model. From the new shape model, some measures for 67P with very low 3σ uncertainties can be retrieved: 18.56 km3 ± 0.02 km3 for the volume and 537.8 kg/m3 ± 0.7 kg/m3 for the mean density assuming a mass value of 9.982 × 1012 kg. Title: Three-dimensional views of the nucleus of Comet 67P/Churyumov-Gerasimenko: an atlas of stereo anaglyphs from OSIRIS-NAC images Authors: Lamy, Philippe L.; Romeuf, David; Faury, Guillaume; Durand, Joelle; Beigbeder, Laurent; Groussin, Olivier Bibcode: 2017DPS....4941504L Altcode: The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA’s Rosetta spacecraft has acquired approximately 25000 images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at various spatial scales down to centimeters per pixel. The bulk of these images have been obtained in sequences and the combined displacement of the Rosetta orbiter along its trajectory and the rotation of the nucleus allow associating many pairs of images appropriate to stereoscopic viewing. This is achieved by constructing anaglyphs after rotating the images so that the relative shift appears horizontal. The shift is set to limit the parallax to approximately 2° (with a maximum value of 4°) for the foreground (to avoid image deformation) and the scene is placed behind the screen for optimal visual comfort. The rotation of the nucleus may have the adverse effect of introducing temporal incoherence, prominently from the variation of the cast shadows. Various solutions are implemented to circumvent this problem, usually by cropping the maximum extent of the shadows. A time of writing, approximately 900 anaglyphs have been produced and we expect to reach several thousand once the systematic search of suitable pairs will be completed. We will present examples of anaglyphs. They will be searchable thanks to a dedicated data base that will document each one including its location on a 3D numerical model of the nucleus. Many possibilities of querying the parameters will be offered. It is anticipated that this atlas available online in the near future will be a valuable tool for fostering our understanding of the complex morphology of the cometary surface and of the processes at work , as well as offering spectacular stereoscopic views of the nucleus enjoyable by a general public. Title: Large scale morphological changes in the Hapi region on comet 67P/Churyumov-Gerasimenko Authors: Davidsson, Bjorn; Lee, Seungwon; von Allmen, Paul; Schloerb, Peter; Hofstadter, Mark; Sierks, Holger; Barbieri, Cesare; Gulkis, Samuel; Keller, Horst Uwe; Koschny, Detlef; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafa; MIRO Team; OSIRIS Team Bibcode: 2017DPS....4941502D Altcode: The Hapi region is located on the northern hemisphere of comet 67P/C-G at the neck that joins the two lobes of the nucleus. It primarily consists of granular material that is unresolved at 0.35 m/pixel resolution and that forms a smooth surface with small slopes with respect to local gravity. The OSIRIS cameras on the ESA spacecraft Rosetta observed Hapi regularly since its rendezvous with the comet in August 2014. No changes were seen during the first five months in orbit but on December 30, 2014, two spots appeared in Hapi. Over the course of two months they grew gradually into a 110 by 70 meter shallow depression with a depth of about 0.5 meters. We use OSIRIS observations to characterize the morphology and spectrophotometry of the region. We use measurements of the thermal emission of the comet by the MIRO millimeter and submillimeter radiometer in combination with thermophysical modeling to characterize the surface temperature, near surface temperature gradient, and thermal inertia of the region. The formation mechanism of the depression is discussed in view of these empirical data. Title: Evidences of Shear Deformations on Comet 67P/Churyumov-Gerasimenko: probing the internal structure of the nucleus Authors: Matonti, C.; Attree, N.; Groussin, O.; Jorda, L.; Viseur, S.; Nebouy, D.; Auger, A. T.; Lamy, P. Bibcode: 2017EPSC...11..777M Altcode: In this work we emphasize the occurrence of structures that can be explained by shear deformation on the nucleus of comet 67P. We first show that the majority of the lineaments in the neck regions correspond to fractures arranged in a network characteristic of shear deformation. These deformations are preferentially located in or near the neck regions. They have likely participated in the mechanical breakdown and the erosion of the nucleus. These results may have implication for deciphering the nucleus internal structural down to hundreds of meters and for inferring the nucleus material mechanical properties. Title: Characterization of the Abydos landing site of Philae on comet 67P/Churyumov-Gerasimenko Authors: Lamy, P.; Faury, G.; Jorda, L.; Romeuf, D.; Capanna, C.; El-Maarry, M. R.; Gaskell, R.; Groussin, O.; Nebouy, D. Bibcode: 2017EPSC...11..560L Altcode: Characterization of the final Abydos landing site of Philae on the nucleus of comet 67P/Churyumov-Gerasimenko based on twelve campaigns of imaging with the OSIRIS-NAC camera. The characterization is based on anaglyphs, a digital terrain model at a spatial scale of 40 cm and color maps. We present the regional setting of Abydos and define geological units. Abydos is essentially an alcove at the foot of a scarp composed of heavily fractured consolidated materials. Title: Seasonal erosion and restoration of the dust cover on comet 67P/Churyumov-Gerasimenko as observed by OSIRIS onboard Rosetta Authors: Hu, X.; Shi, X.; Sierks, H.; Fulle, M.; Blum, J.; Keller, H. U.; Kührt, E.; Davidsson, B.; Güttler, C.; Gundlach, B.; Pajola, M.; Bodewits, D.; Vincent, J. -B.; Oklay, N.; Massironi, M.; Fornasier, S.; Tubiana, C.; Groussin, O.; Boudreault, S.; Höfner, S.; Mottola, S.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; El-Maarry, M. R.; Gicquel, A.; Gutierrez-Marques, P.; Gutiérrez, P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Thomas, N. Bibcode: 2017A&A...604A.114H Altcode: Context. Dust deposits or dust cover are a prevalent morphology in the northern hemi-nucleus of comet 67P/Churyumov-Gerasimenko (67P). The evolution of the dust deposits was captured by the OSIRIS camera system onboard the Rosetta spacecraft having escorted the comet for over two years. The observations shed light on the fundamental role of cometary activity in shaping and transforming the surface morphology.
Aims: We aim to present OSIRIS observations of surface changes over the dust deposits before and after perihelion. The distribution of changes and a timeline of their occurrence are provided. We perform a data analysis to quantify the surface changes and investigate their correlation to water activity from the dust deposits. We further discuss how the results of our investigation are related to other findings from the Rosetta mission.
Methods: Surface changes were detected via systematic comparison of images, and quantified using shape-from-shading technique. Thermal models were applied to estimate the erosion of water ice in response to the increasing insolation over the areas where surface changes occurred. Modeling results were used for the interpretation of the observed surface changes.
Results: Surface changes discussed here were concentrated at mid-latitudes, between about 20°N and 40°N, marking a global transition from the dust-covered to rugged terrains. The changes were distributed in open areas exposed to ample solar illumination and likely subject to enhanced surface erosion before perihelion. The occurrence of changes followed the southward migration of the sub-solar point across the latitudes of their distribution. The erosion at locations of most changes was at least about 0.5 m, but most likely did not exceed several meters. The erosive features before perihelion had given way to a fresh, smooth cover of dust deposits after perihelion, suggesting that the dust deposits had been globally restored by at least about 1 m with ejecta from the intensely illuminated southern hemi-nucleus around perihelion, when the north was inactive during polar night.
Conclusions: The erosion and restoration of the northern dust deposits are morphological expressions of seasonality on 67P. Based on observations and thermal modeling results, it is inferred that the dust deposits contained a few percent of water ice in mass on average. Local inhomogeneity in water abundance at spatial scales below tens of meters is likely. We suspect that dust ejected from the deposits may not have escaped the comet in bulk. That is, at least half of the ejected mass was afloat in the inner-coma or/and redeposited over other areas of the nucleus. Title: Long-term monitoring of comet 67P/Churyumov-Gerasimenko's jets with OSIRIS onboard Rosetta Authors: Schmitt, M. I.; Tubiana, C.; Güttler, C.; Sierks, H.; Vincent, J. -B.; El-Maarry, M. R.; Bodewits, D.; Mottola, S.; Fornasier, S.; Hofmann, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Pajola, M.; Prasanna, D.; Shi, X.; Scholten, F.; Toth, I.; Thomas, N. Bibcode: 2017MNRAS.469S.380S Altcode: We used the OSIRIS camera system onboard the Rosetta spacecraft to monitor jet activity of comet 67P/Churyumov-Gerasimenko. With a monthly cadence, we covered an epoch from 2014 December to 2015 October, thereby including the first equinox and the perihelion passage. Jet features were measured in individual images, which were used to perform a statistical inversion. The study provides maps for the locations of likeliest sources of jet activity on the comet's surface as a function of time. The sources follow the subsolar latitude, show clustering and a broadening of the activity band with time in the Northern hemisphere. In the Southern hemisphere, they are not clustered but show a broader spread over all longitudes which is either related to the north-south dichotomy of the comet's topography or due to a higher insolation during southern summer. Title: Post-perihelion photometry of dust grains in the coma of 67P Churyumov-Gerasimenko Authors: Frattin, E.; Cremonese, G.; Simioni, E.; Bertini, I.; Lazzarin, M.; Ott, T.; Drolshagen, E.; La Forgia, F.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Ferrari, S.; Ferri, F.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lopez Moreno, J. J.; Lucchetti, A.; Marzari, F.; Massironi, M.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Penasa, L.; Shi, X.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2017MNRAS.469S.195F Altcode: We present a photometric analysis of individual dust grains in the coma of comet 67P/Churyumov-Gerasimenko using OSIRIS images taken from 2015 July to 2016 January. We analysed a sample of 555 taken during 18 d at heliocentric distances ranging between 1.25 and 2.04 au and at nucleocentric distances between 80 and 437 km. An automated method to detect the tracks was specifically developed. The images were taken by OSIRIS NAC in four different filters: Near-IR (882 nm), Orange (649 nm), FarOrange (649 nm) and Blue (480 nm). It was not always possible to recognize all the grains in the four filters, hence we measured the spectral slope in two wavelengths ranges: in the interval [480-649] nm, for 1179 grains, and in the interval [649-882] nm, for 746 grains. We studied the evolution of the two populations' average spectral slopes. The data result scattered around the average value in the range [480-649] nm, while in the [649-882] nm we observe a slight decreasing moving away from the Sun as well as a slight increasing with the nucleocentric distance. A spectrophotometric analysis was performed on a subsample of 339 grains. Three major groups were defined, based on the spectral slope between [535-882] nm: (I) the steep spectra that may be related with organic material, (II) the spectra with an intermediate slope, likely a mixture of silicates and organics and (III) flat spectra that may be associated with a high abundance of water ice. Title: Characterization of dust aggregates in the vicinity of the Rosetta spacecraft Authors: Güttler, C.; Hasselmann, P. H.; Li, Y.; Fulle, M.; Tubiana, C.; Kovacs, G.; Agarwal, J.; Sierks, H.; Fornasier, S.; Hofmann, M.; Gutiérrez Marqués, P.; Ott, T.; Drolshagen, E.; Bertini, I.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bodewits, D.; Bertaux, J. -L.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Geiger, B.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Shi, X.; Thomas, N.; Vincent, J. -B. Bibcode: 2017MNRAS.469S.312G Altcode: In a Rosetta/OSIRIS imaging activity in 2015 June, we have observed the dynamic motion of particles close to the spacecraft. Due to the focal setting of the OSIRIS wide angle camera, these particles were blurred, which can be used to measure their distances to the spacecraft. We detected 109 dust aggregates over a 130 min long sequence, and find that their sizes are around a millimetre and their distances cluster between 2 and 40 m from the spacecraft. Their number densities are about a factor 10 higher than expected for the overall coma and highly fluctuating. Their velocities are small compared to the spacecraft orbital motion and directed away from the spacecraft, towards the comet. From this we conclude that they have interacted with the spacecraft and assess three possible scenarios. In the likeliest of the three scenarios, centimetre-sized aggregates collide with the spacecraft and we would observe the fragments. Ablation of a dust layer on the spacecraft's z panel (remote instrument viewing direction) when rotated towards the Sun is a reasonable alternative. We could also measure an acceleration for a subset of 18 aggregates, which is directed away from the Sun and can be explain by a rocket effect, which requires a minimum ice fraction of the order of 0.1 per cent. Title: Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 03 Authors: Agarwal, J.; Della Corte, V.; Feldman, P. D.; Geiger, B.; Merouane, S.; Bertini, I.; Bodewits, D.; Fornasier, S.; Grün, E.; Hasselmann, P.; Hilchenbach, M.; Höfner, S.; Ivanovski, S.; Kolokolova, L.; Pajola, M.; Rotundi, A.; Sierks, H.; Steffl, A. J.; Thomas, N.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J. F.; Feaga, L. M.; Fischer, H.; Fulle, M.; Gicquel, A.; Groussin, O.; Güttler, C.; Gutiérrez, P. J.; Hofmann, M.; Hornung, K.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Kissel, J.; Knollenberg, J.; Koch, A.; Koschny, D.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lamy, P. L.; Langevin, Y.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Lowry, S. C.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Parker, J. Wm.; Rodrigo, R.; Rynö, J.; Shi, X.; Stenzel, O.; Tubiana, C.; Vincent, J. -B.; Weaver, H. A.; Zaprudin, B. Bibcode: 2017MNRAS.469S.606A Altcode: 2017arXiv171010235A On 2016 July 03, several instruments onboard ESA's Rosetta spacecraft detected signs of an outburst event on comet 67P, at a heliocentric distance of 3.32 au from the Sun, outbound from perihelion. We here report on the inferred properties of the ejected dust and the surface change at the site of the outburst. The activity coincided with the local sunrise and continued over a time interval of 14-68 min. It left a 10-m-sized icy patch on the surface. The ejected material comprised refractory grains of several hundred microns in size, and sub-micron-sized water ice grains. The high dust mass production rate is incompatible with the free sublimation of crystalline water ice under solar illumination as the only acceleration process. Additional energy stored near the surface must have increased the gas density. We suggest a pressurized sub-surface gas reservoir, or the crystallization of amorphous water ice as possible causes. Title: Seasonal mass transfer on the nucleus of comet 67P/Chuyumov-Gerasimenko Authors: Keller, H. U.; Mottola, S.; Hviid, S. F.; Agarwal, J.; Kührt, E.; Skorov, Y.; Otto, K.; Vincent, J. -B.; Oklay, N.; Schröder, S. E.; Davidsson, B.; Pajola, M.; Shi, X.; Bodewits, D.; Toth, I.; Preusker, F.; Scholten, F.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hofmann, M.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Küppers, M.; Lara, L. -M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Tubiana, C.; Thomas, N. Bibcode: 2017MNRAS.469S.357K Altcode: 2017arXiv170706812K We collect observational evidence that supports the scheme of mass transfer on the nucleus of comet 67P/Churyumov-Gerasimenko. The obliquity of the rotation axis of 67P causes strong seasonal variations. During perihelion the southern hemisphere is four times more active than the north. Northern territories are widely covered by granular material that indicates back fall originating from the active south. Decimetre sized chunks contain water ice and their trajectories are influenced by an antisolar force instigated by sublimation. OSIRIS observations suggest that up to 20 per cent of the particles directly return to the nucleus surface taking several hours of traveltime. The back fall covered northern areas are active if illuminated but produce mainly water vapour. The decimetre chunks from the nucleus surface are too small to contain more volatile compounds such as CO2 or CO. This causes a north-south dichotomy of the composition measurements in the coma. Active particles are trapped in the gravitational minimum of Hapi during northern winter. They are `shock frozen' and only re-activated when the comet approaches the sun after its aphelion passage. The insolation of the big cavity is enhanced by self-heating, I.e. reflection and IR radiation from the walls. This, together with the pristinity of the active back fall, explains the early observed activity of the Hapi region. Sobek may be a role model for the consolidated bottom of Hapi. Mass transfer in the case of 67P strongly influences the evolution of the nucleus and the interpretation of coma measurements. Title: Investigating the physical properties of outbursts on comet 67P/Churyumov-Gerasimenko Authors: Lin, Zhong-Yi; Knollenberg, J.; Vincent, J. -B.; A'Hearn, M. F.; Ip, W. -H.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Mottola, S.; Bodewits, D.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Deller, J.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Jorda, L.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lai, I. -L.; Lara, L. M.; Lazzarin, M.; Lee, J. -C.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Ott, T.; Drolshagen, E.; Shi, X.; Thomas, N.; Tubiana, C. Bibcode: 2017MNRAS.469S.731L Altcode: Cometary outbursts on several comets have been observed both by ground-based telescopes and by in situ instruments on spacecraft. However, the mechanism behind these phenomena and their physical properties are still unclear. The optical, spectrocopic and infrared remote imaging system (OSIRIS) onboard the Rosetta spacecraft provided first-hand information on the outbursts from comet 67P/Churyumov-Gerasimenko during its perihelion passage in 2015. The physical properties of the outbursts can be investigated by examining the time series of these high-resolution images. An analysis is made of the wide- and narrow-angle images obtained during the monitoring of the outburst sequences, which occurred between July and September in 2015. A ring-masking technique is used to calculate the excess brightness of the outbursts. The ejected mass and expansion velocity of the outbursts is estimated from differences in images made with the same filter (orange filter). The calculated excess brightness from these outburst plumes ranges from a few per cent to 28 per cent. In some major outbursts, the brightness contribution from the outburst plume can be one or two times higher than that of the typical coma jet activities. The strongest event was the perihelion outburst detected just a few hours before perihelion. The mass ejection rate during a generic outburst could reach a few per cent of the steady-state value of the dust coma. Transient events are detected by studying the brightness slope of the outburst plume with continuous streams of outflowing gas and dust triggered by driving mechanisms, as yet not understood, which remain active for several minutes to less than a few hours. Title: Modelling of the outburst on 2015 July 29 observed with OSIRIS cameras in the Southern hemisphere of comet 67P/Churyumov-Gerasimenko Authors: Gicquel, A.; Rose, M.; Vincent, J. -B.; Davidsson, B.; Bodewits, D.; A'Hearn, M. F.; Agarwal, J.; Fougere, N.; Sierks, H.; Bertini, I.; Lin, Z. -Y.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux, J. -L.; Besse, S.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Debei, S.; Deller, J.; De Cecco, M.; Frattin, E.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hu, X.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Lowry, S.; Marzari, F.; Masoumzadeh, N.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C. Bibcode: 2017MNRAS.469S.178G Altcode: 2017arXiv170602729G Images of the nucleus and the coma (gas and dust) of comet 67P/Churyumov- Gerasimenko have been acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) cameras since 2014 March using both the wide-angle camera and the narrow-angle camera (NAC). We use images from the NAC camera to study a bright outburst observed in the Southern hemisphere on 2015 July 29. The high spatial resolution of the NAC is needed to localize the source point of the outburst on the surface of the nucleus. The heliocentric distance is 1.25 au and the spacecraft-comet distance is 186 km. Aiming to better understand the physics that led to the outgassing, we used the Direct Simulation Monte Carlo method to study the gas flow close to the nucleus and the dust trajectories. The goal is to understand the mechanisms producing the outburst. We reproduce the opening angle of the outburst in the model and constrain the outgassing ratio between the outburst source and the local region. The outburst is in fact a combination of both gas and dust, in which the active surface is approximately 10 times more active than the average rate found in the surrounding areas. We need a number of dust particles 7.83 × 1011 to 6.90 × 1015 (radius 1.97-185 μm), which correspond to a mass of dust (220-21) × 103 kg. Title: The scattering phase function of comet 67P/Churyumov-Gerasimenko coma as seen from the Rosetta/OSIRIS instrument Authors: Bertini, I.; La Forgia, F.; Tubiana, C.; Güttler, C.; Fulle, M.; Moreno, F.; Frattin, E.; Kovacs, G.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Drolshagen, E.; Ferrari, S.; Ferri, F.; Fornasier, S.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Hasselmann, P. H.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; Moreno, J. J. Lopez; Lucchetti, A.; Marzari, F.; Massironi, M.; Mottola, S.; Naletto, G.; Oklay, N.; Ott, T.; Penasa, L.; Thomas, N.; Vincent, J. -B. Bibcode: 2017MNRAS.469S.404B Altcode: The study of dust, the most abundant material in cometary nuclei, is pivotal in understanding the original materials forming the Solar system. Measuring the coma phase function provides a tool to investigate the nature of cometary dust. Rosetta/OSIRIS sampled the coma phase function of comet 67P/Churyumov-Gerasimenko, covering a large phase angle range in a small amount of time. Twelve series were acquired in the period from 2015 March to 2016 February for this scientific purpose. These data allowed, after stray light removal, measuring the phase function shape, its reddening, and phase reddening while varying heliocentric and nucleocentric distances. Despite small dissimilarities within different series, we found a constant overall shape. The reflectance has a u-shape with minimum at intermediate phase angles, reaching similar values at the smallest and largest phase angle sampled. The comparison with cometary phase functions in literature indicates OSIRIS curves being consistent with the ones found in many other single comets. The dust has a negligible phase reddening at α < 90°, indicating a coma dominated by single scattering. We measured a reddening of [11-14] %/100 nm between 376 and 744 nm. No trend with heliocentric or nucleocentric distance was found, indicating the coma doesn't change its spectrum with time. These results are consistent with single coma grains and close-nucleus coma photometric results. Comparison with nucleus photometry indicates a different backscattering phase function shape and similar reddening values only at α < 30°. At larger phase angles, the nucleus becomes significantly redder than the coma. Title: Constraints on cometary surface evolution derived from a statistical analysis of 67P's topography Authors: Vincent, J. -B.; Hviid, S. F.; Mottola, S.; Kuehrt, E.; Preusker, F.; Scholten, F.; Keller, H. U.; Oklay, N.; de Niem, D.; Davidsson, B.; Fulle, M.; Pajola, M.; Hofmann, M.; Hu, X.; Rickman, H.; Lin, Z. -Y.; Feller, C.; Gicquel, A.; Boudreault, S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Penasa, L.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C. Bibcode: 2017MNRAS.469S.329V Altcode: 2017arXiv170700734V We present a statistical analysis of the distribution of large-scale topographic features on comet 67P/Churyumov-Gerasimenko. We observe that the cumulative cliff height distribution across the surface follows a power law with a slope equal to -1.69 ± 0.02. When this distribution is studied independently for each region, we find a good correlation between the slope of the power law and the orbital erosion rate of the surface. For instance, the Northern hemisphere topography is dominated by structures on the 100 m scale, while the Southern hemisphere topography, illuminated at perihelion, is dominated by 10 m scale terrain features. Our study suggests that the current size of a cliff is controlled not only by material cohesion but also by the dominant erosional process in each region. This observation can be generalized to other comets, where we argue that primitive nuclei are characterized by the presence of large cliffs with a cumulative height-power index equal to or above -1.5, while older, eroded cometary surfaces have a power index equal to or below -2.3. In effect, our model shows that a measure of the topography provides a quantitative assessment of a comet's erosional history, that is, its evolutionary age. Title: The pebbles/boulders size distributions on Sais: Rosetta's final landing site on comet 67P/Churyumov-Gerasimenko Authors: Pajola, M.; Lucchetti, A.; Fulle, M.; Mottola, S.; Hamm, M.; Da Deppo, V.; Penasa, L.; Kovacs, G.; Massironi, M.; Shi, X.; Tubiana, C.; Güttler, C.; Oklay, N.; Vincent, J. B.; Toth, I.; Davidsson, B.; Naletto, G.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Debei, S.; De Cecco, M.; Deller, J.; El Maarry, M. R.; Fornasier, S.; Frattin, E.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Höfner, S.; Hofmann, M.; Hviid, S. F.; Ip, W. H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Marzari, F.; Michalik, H.; Preusker, F.; Scholten, F.; Thomas, N. Bibcode: 2017MNRAS.469S.636P Altcode: 2017MNRAS.471..680P By using the imagery acquired by the Optical, Spectroscopic, and Infrared Remote Imaging System Wide-Angle Camera (OSIRIS WAC), we prepare a high-resolution morphological map of the Rosetta Sais final landing site, characterized by an outcropping consolidated terrain unit, a coarse boulder deposit and a fine particle deposit. Thanks to the 0.014 m resolution images, we derive the pebbles/boulders size-frequency distribution (SFD) of the area in the size range of 0.07-0.70 m. Sais' SFD is best fitted with a two-segment differential power law: the first segment is in the range 0.07-0.26 m, with an index of -1.7 ± 0.1, while the second is in the range 0.26-0.50 m, with an index of -4.2 +0.4/-0.8. The `knee' of the SFD, located at 0.26 m, is evident both in the coarse and fine deposits. When compared to the Agilkia Rosetta Lander Imaging System images, Sais surface is almost entirely free of the ubiquitous, cm-sized debris blanket observed by Philae. None the less, a similar SFD behaviour of Agilkia, with a steeper distribution above ∼0.3 m, and a flatter trend below that, is observed. The activity evolution of 67P along its orbit provides a coherent scenario of how these deposits were formed. Indeed, different lift pressure values occurring on the two locations and at different heliocentric distances explain the presence of the cm-sized debris blanket on Agilkia observed at 3.0 au inbound. Contrarily, Sais activity after 2.1 au outbound has almost completely eroded the fine deposits fallen during perihelion, resulting in an almost dust-free surface observed at 3.8 au. Title: The opposition effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images Authors: Hasselmann, P. H.; Barucci, M. A.; Fornasier, S.; Feller, C.; Deshapriya, J. D. P.; Fulchignoni, M.; Jost, B.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Gaskell, R. W.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kovacs, G.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, M. L.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pommerol, A.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2017MNRAS.469S.550H Altcode: High-resolution OSIRIS/Rosetta images of 67P/Churyumov-Gerasimenko acquired on the night run of 2016 April 9-10 show, at large scale, an opposition effect (OE) spot sweeping across Imhotep as the phase angle ranges from 0° to 17°. In this work, we fitted the phase curve of the whole surface imaged as well as three particular features using both the linear-exponential and Hapke models. These features encompass different types of spectral behaviour: a circular mesa, one venous structure and an assemblage of bright spots, going from red to blue colours. Both the Hapke and linear-exponential parameters indicate a stepwise sharpening of the OE from bright spots to circular mesa. Yet a very broad nonlinear phase curve is verified and no sign of sharp OE associated with a coherent-backscattering mechanism is observed. We estimate that the 67P surface is dominated by opaque, desiccated and larger-than-wavelength irregular grains. Veins and bright spots display photometric properties consistent with surfaces becoming slightly brighter as they are enriched by high-albedo ice grains. We also report the estimation of normal albedo for all cometary regions observed throughout the image sequence. Comparison to pre-perihelion results indicates that far better insolation of northern brighter regions, I.e. Hapi, Hathor and Seth, is sufficient to explain mismatches on the photometric parameters. However, metre-scale photometric analysis of the Imhotep-Ash boundary area advocates for mild darkening (<7 per cent) of the surface at local scale. Title: The highly active Anhur-Bes regions in the 67P/Churyumov-Gerasimenko comet: results from OSIRIS/ROSETTA observations Authors: Fornasier, S.; Feller, C.; Lee, J. -C.; Ferrari, S.; Massironi, M.; Hasselmann, P. H.; Deshapriya, J. D. P.; Barucci, M. A.; El-Maarry, M. R.; Giacomini, L.; Mottola, S.; Keller, H. U.; Ip, W. -H.; Lin, Z. -Y.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, M. L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Pajola, M.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. -B. Bibcode: 2017MNRAS.469S..93F Altcode: 2017arXiv170702945F The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has become visible from Rosetta only since 2015 March. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rates, thus exposing the sub-surface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur-Bes boundary during/after the perihelion passage, close to the area where exposed CO2 and H2O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers. Title: Long-term survival of surface water ice on comet 67P Authors: Oklay, N.; Mottola, S.; Vincent, J. -B.; Pajola, M.; Fornasier, S.; Hviid, S. F.; Kappel, D.; Kührt, E.; Keller, H. U.; Barucci, M. A.; Feller, C.; Preusker, F.; Scholten, F.; Hall, I.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Deller, J.; Deshapriya, J. D. P.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hasselmann, P. H.; Hofmann, M.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; Moreno, J. J. Lopez; Lucchetti, A.; Marzari, F.; Masoumzadeh, N.; Naletto, G.; Pommerol, A.; Shi, X.; Thomas, N.; Tubiana, C. Bibcode: 2017MNRAS.469S.582O Altcode: Numerous water-ice-rich deposits surviving more than several months on comet 67P/Churyumov-Gerasimenko were observed during the Rosetta mission. We announce the first-time detection of water-ice features surviving up to 2 yr since their first observation via OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) NAC (narrow angle camera). Their existence on the nucleus of comet 67P at the arrival of the Rosetta spacecraft suggests that they were exposed to the surface during the comet's previous orbit. We investigated the temporal variation of large water-ice patches to understand the long-term sustainability of water ice on cometary nuclei on time-scales of months and years. Large clusters are stable over typical periods of 0.5 yr and reduce their size significantly around the comet's perihelion passage, while small exposures disappear. We characterized the temporal variation of their multispectral signatures. In large clusters, dust jets were detected, whereas in large isolated ones no associated activity was detected. Our thermal analysis shows that the long-term sustainability of water-ice-rich features can be explained by the scarce energy input available at their locations over the first half year. However, the situation reverses for the period lasting several months around perihelion passage. Our two end-member mixing analysis estimates a pure water-ice equivalent thickness up to 15 cm within one isolated patch, and up to 2 m for the one still observable through the end of the mission. Our spectral modelling estimates up to 48 per cent water-ice content for one of the large isolated feature, and up to 25 per cent water ice on the large boulders located within clusters. Title: A three-dimensional modelling of the layered structure of comet 67P/Churyumov-Gerasimenko Authors: Penasa, L.; Massironi, M.; Naletto, G.; Simioni, E.; Ferrari, S.; Pajola, M.; Lucchetti, A.; Preusker, F.; Scholten, F.; Jorda, L.; Gaskell, R.; Ferri, F.; Marzari, F.; Davidsson, B.; Mottola, S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Feller, C.; Fornasier, S.; Frattin, E.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W. H.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lee, J. -C.; Lopez Moreno, J. J.; Oklay, N.; Shi, X.; Thomas, N.; Tubiana, C.; Vincent, J. B. Bibcode: 2017MNRAS.469S.741P Altcode: We provide a three-dimensional model of the inner layered structure of comet 67P based on the hypothesis of an extended layering independently wrapping each lobe. A large set of terrace orientations was collected on the latest shape model and then used as a proxy for the local orientation of the surfaces of discontinuity which defines the layers. We modelled the terraces as a family of concentric ellipsoidal shells with fixed axis ratios, producing a model that is completely defined by just eight free parameters. Each lobe of 67P has been modelled independently, and the two sets of parameters have been estimated by means of non-linear optimization of the measured terrace orientations. The proposed model is able to predict the orientation of terraces, the elongation of cliffs, the linear traces observed in the Wosret and Hathor regions and the peculiar alignment of boulder-like features which has been observed in the Hapi region, which appears to be related to the inner layering of the big lobe. Our analysis allowed us to identify a plane of junction between the two lobes, further confirming the independent nature of the lobes. Our layering models differ from the best-fitting topographic ellipsoids of the surface, demonstrating that the terraces are aligned to an internal structure of discontinuities, which is unevenly exposed on the surface, suggesting a complex history of localized material removal from the nucleus. Title: Geomorphological and spectrophotometric analysis of Seth's circular niches on comet 67P/Churyumov-Gerasimenko using OSIRIS images Authors: Lucchetti, A.; Pajola, M.; Fornasier, S.; Mottola, S.; Penasa, L.; Jorda, L.; Cremonese, G.; Feller, C.; Hasselmann, P. H.; Massironi, M.; Ferrari, S.; Naletto, G.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Boudreault, S.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hoffman, M.; Hviid, S. F.; Ip, W. H.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; La Forgia, F.; Lin, L. Z.; Lopez Moreno, J. J.; Marzari, F.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Tubiana, C.; Vincent, J. B. Bibcode: 2017MNRAS.469S.238L Altcode: We provide a detailed geomorphological and spectrophotometric analysis of the circular niches located on the Seth region of 67P using OSIRIS images. The features can be related to landslide events that occurred on 67P and shaped its surface, as the recent Aswan cliff collapse detected in the same region. We therefore provide an analysis of the area pre- and post-perihelion suggesting that no specific changes have been observed. To assess this, after performing a geomorphological map of the area that allows us to identify different terrain units, we computed the boulders cumulative size frequency distribution (SFD) of the niches, before and after the perihelion passage. The niches SFDs are characterized by a similar trend with two different power-law indices within the same deposit: lower power-law value (between -2.3 and -2.7) for boulders smaller than 5 m and steeper power-law value (between -4.7 and -5.0) for boulders larger than 5 m. These trends suggest that smaller boulders have evolved and progressively have been depleted (lower power-law index), while bigger boulders are more representative of the event that generated the deposit and are less degraded. Then, we perform the spectrophotometric analysis of this region comparing pre- and post-perihelion results. We found colour changes within the area, in particular brighter patches related to the presence of exposed water ice mixed to the refractory materials have been detected in the post-perihelion images. Title: Thermal modelling of water activity on comet 67P/Churyumov-Gerasimenko with global dust mantle and plural dust-to-ice ratio Authors: Hu, X.; Shi, X.; Sierks, H.; Blum, J.; Oberst, J.; Fulle, M.; Kührt, E.; Güttler, C.; Gundlach, B.; Keller, H. U.; Mottola, S.; Pajola, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Büttner, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marqués, P.; Hall, I.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Richards, M. L.; Ripken, J.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2017MNRAS.469S.295H Altcode: We perform a thermo-physical analysis on water activity of comet 67P/Churyumov-Gerasimenko (67P). The sublimation of water is assumed to occur from beneath a global, desiccated dust mantle over the irregular-shaped nucleus. The concept of two thermal models, the recipe of model formulation and the strategy of application to comet 67P are described. For an accurate and efficient evaluation of energy input by insolation and self-heating over the nucleus, a Landscape data base is devised based on polyhedral shape models of the nucleus. We apply the thermal models to investigate the impact of certain parameters of nucleus properties on water production. It is found that the measured water production of 67P can be overall attributed to sublimation of water ice with a mass abundance of a few to 10 per cent beneath a uniform dust mantle of several millimetres to one centimetre in thickness. Insofar as 67P is concerned, we argue against the necessity to invoke assumptions on localized water activity, or on the distinction of active/dormant surface areas. Title: Anomalous Surge of the White-Light Corona at the Onset of the Declining Phase of Solar Cycle 24 Authors: Lamy, P.; Boclet, B.; Wojak, J.; Vibert, D. Bibcode: 2017SoPh..292...60L Altcode: In late 2014, when the current Solar Cycle 24 entered its declining phase, the white-light corona as observed by the LASCO-C2 coronagraph underwent an unexpected surge that increased its global radiance by 60%, reaching a peak value comparable to the peak values of the more active Solar Cycle 23. A comparison of the temporal variation of the white-light corona with the variations of several indices and proxies of solar activity indicate that it best matches the variation of the total magnetic field. The daily variations point to a localized enhancement or bulge in the electron density that persisted for several months. Carrington maps of the radiance and of the HMI photospheric field allow connecting this bulge to the emergence of the large sunspot complex AR 12192 in October 2014, the largest since AR 6368 observed in November 1990. The resulting unusually high increase of the magnetic field and the distortion of the neutral sheet in a characteristic inverse S-shape caused the coronal plasma to be trapped along a similar pattern. A 3D reconstruction of the electron density based on time-dependent solar rotational tomography supplemented by 2D inversion of the coronal radiance confirms the morphology of the bulge and reveals that its level was well above the standard models of a corona of the maximum type, by typically a factor of 3. A rather satisfactory agreement is found with the results of the thermodynamic MHD model produced by Predictive Sciences, although discrepancies are noted. The specific configuration of the magnetic field that led to the coronal surge resulted from the interplay of various factors prevailing at the onset of the declining phase of the solar cycles, which was particularly efficient in the case of Solar Cycle 24. Title: Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko Authors: Perna, D.; Fulchignoni, M.; Barucci, M. A.; Fornasier, S.; Feller, C.; Deshapriya, J. D. P.; Hasselmann, P. H.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; El-Maarry, M. R.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2017A&A...600A.115P Altcode: Context. The ESA Rosetta mission explored comet 67P/Churyumov-Gerasimenko in 2014-2016, following its target before and after the perihelion passage on 13 August 2015. The NAC camera of the OSIRIS imaging system allowed to map the nucleus surface acquiring images with different filters in the visible wavelength range.
Aims: Here we study the spectrophotometric behaviour of the nucleus by a multivariate statistical analysis, aiming to distinguish homogeneous groups and to constrain the bulk composition.
Methods: We applied the G-mode clustering algorithm to 16 OSIRIS data cubes acquired on 5-6 August 2014 (mostly covering the northern hemisphere) and 2 May 2015 (mostly covering the southern hemisphere), selected to have complete coverage of the comet's surface with similar observing conditions.
Results: We found four similar homogeneous groups for each of the analysed cubes. The first group corresponds to the average spectrophotometric behaviour of the nucleus. The second (spectrally redder) and the third (spectrally bluer) groups are found in regions that were already found to deviate from the average terrain of the comet by previous studies. A fourth group (characterised by enhancements of the flux at 700-750 nm and 989 nm, possibly due to H2O+ and/or NH2 emissions) seems connected with the cometary activity rather than with the bulk composition.
Conclusions: While our aim in this work was to study the spectrophotometric behaviour of the nucleus of 67P/Churyumov-Gerasimenko as a whole, we found that a follow-up application of the G-mode to smaller regions of the surface could be useful in particular to identify and study the temporal evolution of ice patches, as well as to constrain the composition and physical processes behind the emission of dust jets. Title: Opposition effect on comet 67P/Churyumov-Gerasimenko using Rosetta-OSIRIS images Authors: Masoumzadeh, N.; Oklay, N.; Kolokolova, L.; Sierks, H.; Fornasier, S.; Barucci, M. A.; Vincent, J. -B.; Tubiana, C.; Güttler, C.; Preusker, F.; Scholten, F.; Mottola, S.; Hasselmann, P. H.; Feller, C.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Hall, I.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Shi, X.; Thomas, N. Bibcode: 2017A&A...599A..11M Altcode:
Aims: We aim to explore the behavior of the opposition effect as an important tool in optical remote sensing on the nucleus of comet 67P/ Churyumov-Gerasimenko (67P), using Rosetta-OSIRIS images acquired in different filters during the approach phase, July-August 2014 and the close flyby images on 14 of February 2015, which contain the spacecraft shadow.
Methods: We based our investigation on the global and local brightness from the surface of 67P with respect to the phase angle, also known as phase curve. The local phase curve corresponds to a region that is located at the Imhotep-Ash boundary of 67P. Assuming that the region at the Imhotep-Ash boundary and the entire nucleus have similar albedo, we combined the global and local phase curves to study the opposition-surge morphology and constrain the structure and properties of 67P. The model parameters were furthermore compared with other bodies in the solar system and existing laboratory study.
Results: We found that the morphological parameters of the opposition surge decrease monotonically with wavelength, whereas in the case of coherent backscattering this behavior should be the reverse. The results from comparative analysis place 67P in the same category as the two Mars satellites, Phobos and Deimos, which are notably different from all airless bodies in the solar system. The similarity between the surface phase function of 67P and a carbon soot sample at extremely small angles is identified, introducing regolith at the boundary of the Imhotep-Ash region of 67P as a very dark and fluffy layer. Title: Surface changes on comet 67P/Churyumov-Gerasimenko suggest a more active past Authors: El-Maarry, M. Ramy; Groussin, O.; Thomas, N.; Pajola, M.; Auger, A. -T.; Davidsson, B.; Hu, X.; Hviid, S. F.; Knollenberg, J.; Güttler, C.; Tubiana, C.; Fornasier, S.; Feller, C.; Hasselmann, P.; Vincent, J. -B.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Keller, H. U.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Deshapriya, J. D. P.; Fulle, M.; Gutierrez, P. J.; Hofmann, M.; Ip, W. -H.; Jorda, L.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Yi; Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X. Bibcode: 2017Sci...355.1392E Altcode: The Rosetta spacecraft spent ~2 years orbiting comet 67P/Churyumov-Gerasimenko, most of it at distances that allowed surface characterization and monitoring at submeter scales. From December 2014 to June 2016, numerous localized changes were observed, which we attribute to cometary-specific weathering, erosion, and transient events driven by exposure to sunlight and other processes. While the localized changes suggest compositional or physical heterogeneity, their scale has not resulted in substantial alterations to the comet’s landscape. This suggests that most of the major landforms were created early in the comet’s current orbital configuration. They may even date from earlier if the comet had a larger volatile inventory, particularly of CO or CO2 ices, or contained amorphous ice, which could have triggered activity at greater distances from the Sun. Title: The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse Authors: Pajola, M.; Höfner, S.; Vincent, J. B.; Oklay, N.; Scholten, F.; Preusker, F.; Mottola, S.; Naletto, G.; Fornasier, S.; Lowry, S.; Feller, C.; Hasselmann, P. H.; Güttler, C.; Tubiana, C.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Boudreault, S.; Cremonese, G.; da Deppo, V.; Davidsson, B.; Debei, S.; de Cecco, M.; Deller, J.; Deshapriya, J. D. P.; El-Maarry, M. R.; Ferrari, S.; Ferri, F.; Fulle, M.; Groussin, O.; Gutierrez, P.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lin, Z. -Y.; Lazzarin, M.; Lucchetti, A.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Michalik, H.; Penasa, L.; Pommerol, A.; Simioni, E.; Thomas, N.; Toth, I.; Baratti, E. Bibcode: 2017NatAs...1E..92P Altcode: Outbursts occur commonly on comets1 with different frequencies and scales2,3. Despite multiple observations suggesting various triggering processes4,5, the driving mechanism of such outbursts is still poorly understood. Landslides have been invoked6 to explain some outbursts on comet 103P/Hartley 2, although the process required a pre-existing dust layer on the verge of failure. The Rosetta mission observed several outbursts from its target comet 67P/Churyumov-Gerasimenko, which were attributed to dust generated by the crumbling of materials from collapsing cliffs7,8. However, none of the aforementioned works included definitive evidence that landslides occur on comets. Amongst the many features observed by Rosetta on the nucleus of the comet, one peculiar fracture, 70 m long and 1 m wide, was identified on images obtained in September 2014 at the edge of a cliff named Aswan9. On 10 July 2015, the Rosetta Navigation Camera captured a large plume of dust that could be traced back to an area encompassing the Aswan escarpment7. Five days later, the OSIRIS camera observed a fresh, sharp and bright edge on the Aswan cliff. Here we report the first unambiguous link between an outburst and a cliff collapse on a comet. We establish a new dust-plume formation mechanism that does not necessarily require the breakup of pressurized crust or the presence of supervolatile material, as suggested by previous studies7. Moreover, the collapse revealed the fresh icy interior of the comet, which is characterized by an albedo >0.4, and provided the opportunity to study how the crumbling wall settled down to form a new talus. Title: Different Origins or Different Evolutions? Decoding the Spectral Diversity Among C-type Asteroids Authors: Vernazza, P.; Castillo-Rogez, J.; Beck, P.; Emery, J.; Brunetto, R.; Delbo, M.; Marsset, M.; Marchis, F.; Groussin, O.; Zanda, B.; Lamy, P.; Jorda, L.; Mousis, O.; Delsanti, A.; Djouadi, Z.; Dionnet, Z.; Borondics, F.; Carry, B. Bibcode: 2017AJ....153...72V Altcode: 2017arXiv170106603V Anhydrous pyroxene-rich interplanetary dust particles (IDPs) have been proposed as surface analogs for about two-thirds of all C-complex asteroids. However, this suggestion appears to be inconsistent with the presence of hydrated silicates on the surfaces of some of these asteroids, including Ceres. Here, we report the presence of enstatite (pyroxene) on the surface of two C-type asteroids (Ceres and Eugenia) based on their spectral properties in the mid-infrared range. The presence of this component is particularly unexpected in the case of Ceres, because most thermal evolution models predict a surface consisting of hydrated compounds only. The most plausible scenario is that Ceres’ surface has been partially contaminated by exogenous enstatite-rich material, possibly coming from the Beagle asteroid family. This scenario questions a similar origin for Ceres and the remaining C-types, and it possibly supports recent results obtained by the Dawn mission (NASA) that Ceres may have formed in the very outer solar system. Concerning the smaller D ∼ 200 km C-types such as Eugenia, both their derived surface composition (enstatite and amorphous silicates) and low density (<1.5 g cm-3) suggest that these bodies accreted from the same building blocks, namely chondritic porous, pyroxene-rich IDPs and volatiles (mostly water ice), and that a significant volume fraction of these bodies has remained unaffected by hydrothermal activity likely implying a late accretion. In addition, their current heliocentric distance may best explain the presence or absence of water ice at their surfaces. Finally, we raise the possibility that CI chondrites, Tagish-Lake-like material, or hydrated IDPs may be representative samples of the cores of these bodies. Title: Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images: The southern hemisphere (Corrigendum) Authors: El-Maarry, M. R.; Thomas, N.; Gracia-Berná, A.; Pajola, M.; Lee, J. -C.; Massironi, M.; Davidsson, B.; Marchi, S.; Keller, H. U.; Hviid, S. F.; Besse, S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Koschny, D.; Rickman, H.; Rodrigo, R.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; De Cecco, M.; Debei, S.; Güttler, C.; Fornasier, S.; Fulle, M.; Giacomini, L.; Groussin, O.; Gutierrez, P. J.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marschall, R.; Marzari, F.; Naletto, G.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J. -B. Bibcode: 2017A&A...598C...2E Altcode: No abstract at ADS Title: Coronal mass ejections and solar wind mass fluxes over the heliosphere during solar cycles 23 and 24 (1996-2014) Authors: Lamy, P.; Floyd, O.; Quémerais, E.; Boclet, B.; Ferron, S. Bibcode: 2017JGRA..122...50L Altcode: Coronal mass ejections (CMEs) play a major role in the heliosphere, and their contribution to the solar wind mass flux, already considered in the Skylab and Solwind eras with conflicting results, is reexamined in the light of 19 years (1996-2014) of SOHO observations with the Large Angle and Spectroscopic Coronagraph (LASCO-C2) for the CMEs and extended for the first time to all latitudes thanks to the whole-heliosphere data from the Solar Wind ANisotropies (SWAN) instrument supplemented by in situ data aggregated in the OMNI database. First, several mass estimates reported in the ARTEMIS (Automated Recognition of Transient Events and Marseille Inventory from Synoptic maps) catalog of LASCO CMEs are compared with determinations based on the combined observations with the twin STEREO/Sun Earth Connection Coronal and Heliospheric Investigation coronagraphs in order to ascertain their validity. A simple geometric model of the CMEs is introduced to generate Carrington maps of their mass flux and then to produce annualized synoptic maps. The Lyman α SWAN data are inverted to similarly produce synoptic maps to be compared with those of the CME flux. The ratio of the annualized CME to solar wind mass flux is found to closely track the solar cycle over the heliosphere. In the near-ecliptic region and at latitudes up to ∼55°, this ratio was negligibly small during the solar minima of cycles 22/23 and 23/24 and rose to 6% and 5%, respectively, at the maximum of solar cycles 23 and 24. These maximum ratios increased at higher latitudes, but this result is likely biased by the inherent limitation of determining the true latitude of CMEs. Title: A mini outburst from the nightside of comet 67P/Churyumov-Gerasimenko observed by the OSIRIS camera on Rosetta Authors: Knollenberg, J.; Lin, Z. Y.; Hviid, S. F.; Oklay, N.; Vincent, J. -B.; Bodewits, D.; Mottola, S.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Davidsson, B.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Kührt, E.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Thomas, N.; Güttler, C.; Preusker, F.; Scholten, F.; Tubiana, C. Bibcode: 2016A&A...596A..89K Altcode: Context. On 12 March 2015 the OSIRIS WAC camera onboard the ESA Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko observed a small outburst originating from the Imhotep region at the foot of the big lobe of the comet. These measurements are unique since it was the first time that the initial phase of a transient outburst event could be directly observed.
Aims: We investigate the evolution of the dust jet in order to derive clues about the outburst source mechanism and the ejected dust particles, in particular the dust mass, dust-to-gas ratio and the particle size distribution.
Methods: Analysis of the images and of the observation geometry using comet shape models in combination with gasdynamic modeling of the transient dust jet were the main tools used in this study. Synthetic images were computed for comparison with the observations.
Results: Analysis of the geometry revealed that the source region was not illuminated until 1.5 h after the event implying true nightside activity was observed. The outburst lasted for less than one hour and the average dust production rate during the initial four minutes was of the order of 1 kg/s. During this time the outburst dust production rate was approximately constant, no sign for an initial explosion could be detected. For dust grains between 0.01-1 mm a power law size distribution characterized by an index of about 2.6 provides the best fit to the observed radiance profiles. The dust-to-gas ratio of the outburst jet is in the range 0.6-1.8. Title: Rosetta’s comet 67P/Churyumov-Gerasimenko sheds its dusty mantle to reveal its icy nature Authors: Fornasier, S.; Mottola, S.; Keller, H. U.; Barucci, M. A.; Davidsson, B.; Feller, C.; Deshapriya, J. D. P.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M.; Agarwal, J.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; El-Maarry, M. R.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, M. L.; Lazzarin, M.; Moreno, J. J. Lopez; Marzari, F.; Massironi, M.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. -B. Bibcode: 2016Sci...354.1566F Altcode: The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko from large heliocentric distances to its perihelion passage and beyond. We trace the seasonal and diurnal evolution of the colors of the 67P nucleus, finding changes driven by sublimation and recondensation of water ice. The whole nucleus became relatively bluer near perihelion, as increasing activity removed the surface dust, implying that water ice is widespread underneath the surface. We identified large (1500 square meters) ice-rich patches appearing and then vanishing in about 10 days, indicating small-scale heterogeneities on the nucleus. Thin frosts sublimating in a few minutes are observed close to receding shadows, and rapid variations in color are seen on extended areas close to the terminator. These cyclic processes are widespread and lead to continuously, slightly varying surface properties. Title: Mapping of the source regions of the dust jets on comet 67P/Churyumov-Gerasimenko Authors: Lai, I. L.; Ip, W. H.; Lee, J. C.; Lin, Z. Y.; Vincent, J. B.; Hartogh, P.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rickman, H.; Keller, H. U. Bibcode: 2016AGUFM.P43A2087L Altcode: Because of the inclination of the rotational axis to the orbital plane and the orbital motion around the Sun, the sunlit regions on the nucleus surface of comet 67P/Churyumov-Gerasimenko moved from the northern hemisphere to the sourthern hemisphere between August, 2014 and August, 2015. From the comparison of the dust jet features in images taken at successive time series, the footpoints of these jets can be identified by a projection method. The distributiosn of the corresponding source regions can be compared with the geomorphology of the nucleus surface from inbound to outbound. The correlation of the dust jet activity with the volatile outgassing phenomenon as monitored by different scientific instruments onboard Rosetta will provide important information on the sublimation process. Title: Gas outflow and dust transport of comet 67P/Churyumov-Gerasimenko Authors: Lai, Ian-Lin; Ip, Wing-Huen; Su, Cheng-Chin; Wu, Jong-Shinn; Lee, Jui-Chi; Lin, Zhong-Yi; Liao, Ying; Thomas, Nicolas; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F.; Barucci, Maria Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Boudreault, Steven; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Deller, Jakob; Fornasier, Sonia; Fulle, Marco; Groussin, Olivier; Gutiérrez, Pedro J.; Güttler, Carsten; Hofmann, Marc; Hviid, Stubbe F.; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor; Kramm, J. -Rainer; Kührt, Ekkehard; Küppers, Michael; Lara, Luisa M.; Lazzarin, Monica; Lopez Moreno, Josè J.; Marzari, Francesco; Naletto, Giampiero; Oklay, Nilda; Shi, Xian; Tubiana, Cecilia; Vincent, Jean-Baptiste Bibcode: 2016MNRAS.462S.533L Altcode: Because of the diurnal thermal cycle and the irregular shape of the nucleus, gas outflow of comet 67P/Churyumov-Gerasimenko could be highly anisotropic as indicated by the colliminated dust jet structures on the sunlit side. Based on the OSIRIS imaging observations of the outgassing effect, a simple model of surface sublimation can be constructed by taking into account the dependence on the solar insolation. With preliminary information on the time variability of the global gas production rate, a sequence of gas coma models can be generated at different epochs before and after perihelion. We also investigate different patterns of dust particle dynamics under the influences of nuclear rotation and gas drag. From these considerations, a consistent picture of the spatial distribution of dusty materials across the surface of comet 67P as it moves around the perihelion can be developed. It is found that because of the redeposition of the ejected dust from the Southern hemisphere to the Northern hemisphere during the southern summer season the Hapi region could gain up to 0.4 m while the Wosret region would lose up to 1.8 m of dust mantle per orbit. Title: Comparative study of water ice exposures on cometary nuclei using multispectral imaging data Authors: Oklay, N.; Sunshine, J. M.; Pajola, M.; Pommerol, A.; Vincent, J. -B.; Mottola, S.; Sierks, H.; Fornasier, S.; Barucci, M. A.; Preusker, F.; Scholten, F.; Lara, L. M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hall, I.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lazzarin, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Shi, X.; Thomas, N.; Tubiana, C. Bibcode: 2016MNRAS.462S.394O Altcode: Deep Impact, EPOXI and Rosetta missions visited comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko, respectively. Each of these three missions was equipped with both multispectral imagers and infrared spectrometers. Bright blue features containing water ice were detected in each of these comet nuclei. We analysed multispectral properties of enriched water ice features observed via Optical, Spectroscopic, and Infrared Remote Imaging System narrow angle camera on comet 67P in the wavelength range of 260-1000 nm and then compared with multispectral data of water ice deposits observed on comets 9P and 103P. We characterize the UV/VIS properties of water-ice-rich features observed on the nuclei of these three comets. When compared to the average surface of each comet, our analysis shows that the water ice deposits seen on comet 9P are similar to the clustered water-ice-rich features seen on comet 67P, while the water ice deposit seen on comet 103P is more akin to two large isolated water-ice-rich features seen on comet 67P. Our results indicate that the water ice deposit observed on comet 103P contains more water ice than the water-ice-rich features observed on comets 9P and 67P, proportionally to the average surface of each nucleus. Title: Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images Authors: Deshapriya, J. D. P.; Barucci, M. A.; Fornasier, S.; Feller, C.; Hasselmann, P. H.; Sierks, H.; El-Maarry, M. R.; Pajola, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; Deller, J.; De Cecco, M.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Perna, D.; Pommerol, A.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2016MNRAS.462S.274D Altcode: 2016MNRAS.tmp.1515D Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 +0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units. Title: Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko Authors: Agarwal, Jessica; A'Hearn, M. F.; Vincent, J. -B.; Güttler, C.; Höfner, S.; Sierks, H.; Tubiana, C.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Shi, X.; Thomas, N. Bibcode: 2016MNRAS.462S..78A Altcode: 2016MNRAS.tmp.1292A; 2016arXiv160807933A We present observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained with the narrow angle camera of the Optical, Spectroscopic, and Infrared Remote Imaging System on board the Rosetta spacecraft in 2016 January when the comet was at 2 au from the Sun outbound from perihelion. We measure the acceleration of individual aggregates through a 2 h image series. Approximately 50 per cent of the aggregates are accelerated away from the nucleus, and 50 per cent towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10 per cent of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the Northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2 km) of a comet, where gas drag is still significant. Title: Changes in the Physical Environment of the Inner Coma of 67P/Churyumov-Gerasimenko with Decreasing Heliocentric Distance Authors: Bodewits, D.; Lara, L. M.; A'Hearn, M. F.; La Forgia, F.; Gicquel, A.; Kovacs, G.; Knollenberg, J.; Lazzarin, M.; Lin, Z. -Y.; Shi, X.; Snodgrass, C.; Tubiana, C.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Kramm, J. -R.; Kührt, E.; Küppers, M.; López-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Thomas, N.; Toth, I.; Vincent, J. -B. Bibcode: 2016AJ....152..130B Altcode: 2016arXiv160705632B The Wide Angle Camera of the OSIRIS instrument on board the Rosetta spacecraft is equipped with several narrow-band filters that are centered on the emission lines and bands of various fragment species. These are used to determine the evolution of the production and spatial distribution of the gas in the inner coma of comet 67P with time and heliocentric distance, here between 2.6 and 1.3 au pre-perihelion. Our observations indicate that the emission observed in the OH, O I, CN, NH, and NH2 filters is mostly produced by dissociative electron impact excitation of different parent species. We conclude that CO2 rather than H2O is a significant source of the [O I] 630 nm emission. A strong plume-like feature observed in the CN and O I filters is present throughout our observations. This plume is not present in OH emission and indicates a local enhancement of the CO2/H2O ratio by as much as a factor of 3. We observed a sudden decrease in intensity levels after 2015 March, which we attribute to decreased electron temperatures in the first few kilometers above the surface of the nucleus. Title: Summer fireworks on comet 67P Authors: Vincent, J. -B.; A'Hearn, M. F.; Lin, Z. -Y.; El-Maarry, M. R.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Mottola, S.; Naletto, G.; Oklay, N.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C. Bibcode: 2016MNRAS.462S.184V Altcode: 2016arXiv160907743V During its 2 yr mission around comet 67P/Churyumov-Gerasimenko, ESA's Rosetta spacecraft had the unique opportunity to follow closely a comet in the most active part of its orbit. Many studies have presented the typical features associated with the activity of the nucleus, such as localized dust and gas jets. Here, we report on series of more energetic transient events observed during the 3 months surrounding the comet's perihelion passage in 2015 August. We detected and characterized 34 outbursts with the Rosetta cameras, one every 2.4 nucleus rotations. We identified three main dust plume morphologies associated with these events: a narrow jet, a broad fan, and more complex plumes featuring both previous types together. These plumes are comparable in scale and temporal variation to what has been observed on other comets. We present a map of the outbursts' source locations, and discuss the associated topography. We find that the spatial distribution sources on the nucleus correlate well with morphological region boundaries, especially in areas marked by steep scarps or cliffs. Outbursts occur either in the early morning or shortly after the local noon, indicating two potential processes: morning outbursts may be triggered by thermal stresses linked to the rapid change of temperature; afternoon events are most likely related to the diurnal or seasonal heat wave reaching volatiles buried under the first surface layer. In addition, we propose that some events can be the result of a completely different mechanism, in which most of the dust is released upon the collapse of a cliff. Title: The Agilkia boulders/pebbles size-frequency distributions: OSIRIS and ROLIS joint observations of 67P surface Authors: Pajola, M.; Mottola, S.; Hamm, M.; Fulle, M.; Davidsson, B.; Güttler, C.; Sierks, H.; Naletto, G.; Arnold, G.; Grothues, H. -G.; Jaumann, R.; Michaelis, H.; Bibring, J. P.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; El Maarry, M. R.; Feller, C.; Fornasier, S.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lin, Z. Y.; Lazzarin, M.; Lopez Moreno, J. J.; Lucchetti, A.; Marzari, F.; Massironi, M.; Michalik, H.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Thomas, N.; Tubiana, C.; Vincent, J. B. Bibcode: 2016MNRAS.462S.242P Altcode: By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size-frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05-30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders 'peek through' the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD. Title: Decimetre-scaled spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations Authors: Feller, C.; Fornasier, S.; Hasselmann, P. H.; Barucci, A.; Preusker, F.; Scholten, F.; Jorda, L.; Pommerol, A.; Jost, B.; Poch, O.; ElMaary, M. R.; Thomas, N.; Belskaya, I.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Koschny, D.; Rickman, H.; Rodrigo, R.; Agarwal, J.; A'Hearn, M.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Deller, J.; Fulle, M.; Giquel, A.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Keller, H.; Ip, W. -H.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, M. L.; Lazzarin, M.; Leyrat, C.; Lopez Moreno, J. J.; Marzari, F.; Masoumzadeh, N.; Mottola, S.; Naletto, G.; Perna, D.; Oklay, N.; Shi, X.; Tubiana, C.; Vincent, J. -B. Bibcode: 2016MNRAS.462S.287F Altcode: 2016arXiv161100012F We present the results of the photometric and spectrophotometric properties of the 67P/Churyumov-Gerasimenko nucleus derived with the Optical, Spectroscopic and Infrared Remote Imaging System instrument during the closest fly-by over the comet, which took place on 2015 February 14 at a distance of ∼6 km from the surface. Several images covering the 0°-33° phase angle range were acquired, and the spatial resolution achieved was 11 cm pixel-1. The flown-by region is located on the big lobe of the comet, near the borders of the Ash, Apis and Imhotep regions. Our analysis shows that this region features local heterogeneities at the decimetre scale. We observed difference of reflectance up to 40 per cent between bright spots and sombre regions, and spectral slope variations up to 50 per cent. The spectral reddening effect observed globally on the comet surface by Fornasier et al. (2015) is also observed locally on this region, but with a less steep behaviour. We note that numerous metre-sized boulders, which exhibit a smaller opposition effect, also appear spectrally redder than their surroundings. In this region, we found no evidence linking observed bright spots to exposed water-ice-rich material. We fitted our data set using the Hapke 2008 photometric model. The region overflown is globally as dark as the whole nucleus (geometric albedo of 6.8 per cent) and it has a high porosity value in the uppermost layers (86 per cent). These results of the photometric analysis at a decimetre scale indicate that the photometric properties of the flown-by region are similar to those previously found for the whole nucleus. Title: Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's Northern hemisphere Authors: Giacomini, L.; Massironi, M.; El-Maarry, M. R.; Penasa, L.; Pajola, M.; Thomas, N.; Lowry, S. C.; Barbieri, C.; Cremonese, G.; Ferri, F.; Naletto, G.; Bertini, I.; La Forgia, F.; Lazzarin, M.; Marzari, F.; Sierks, H.; Lamy, P. L.; Rodrigo, R.; Rickman, H.; Koschny, D.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Besse, S.; Bodewits, D.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Moreno, J. J. Lopez; Magrin, S.; Michalik, H.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J. -B. Bibcode: 2016MNRAS.462S.352G Altcode: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), the scientific imaging system onboard the Rosetta mission, has been acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko since 2014 August with a resolution which allows a detailed analysis of its surface. Indeed, data reveal a complex surface morphology which is likely the expression of different processes which occurred at different times on the cometary nucleus. In order to characterize these different morphologies and better understand their distribution, we performed a geologic mapping of comet's 67P Northern hemisphere in which features have been distinguished based on their morphological, textural and stratigraphic characteristics. For this purpose, we used narrow-angle camera images acquired in 2014 August and September with a spatial scale ranging from 1.2 to 2.4 m pixel-1. Several different geologic units have been identified on the basis of their different surface textures, granulometry and morphology. Some of these units are distinctive and localized, whereas others are more common and distributed all over the Northern hemisphere. Moreover, different types of linear features have been distinguished on the basis of their morphology. Some of these lineaments have never been observed before on a comet and can offer important clues on the internal structures of the nucleus itself. The geologic mapping results presented here will allow us to better understand the processes which affected the nucleus' surface and thus the origin and evolutionary history of comet 67P/Churyumov-Gerasimenko. Title: The 2016 Feb 19 outburst of comet 67P/CG: an ESA Rosetta multi-instrument study Authors: Grün, E.; Agarwal, J.; Altobelli, N.; Altwegg, K.; Bentley, M. S.; Biver, N.; Della Corte, V.; Edberg, N.; Feldman, P. D.; Galand, M.; Geiger, B.; Götz, C.; Grieger, B.; Güttler, C.; Henri, P.; Hofstadter, M.; Horanyi, M.; Jehin, E.; Krüger, H.; Lee, S.; Mannel, T.; Morales, E.; Mousis, O.; Müller, M.; Opitom, C.; Rotundi, A.; Schmied, R.; Schmidt, F.; Sierks, H.; Snodgrass, C.; Soja, R. H.; Sommer, M.; Srama, R.; Tzou, C. -Y.; Vincent, J. -B.; Yanamandra-Fisher, P.; A'Hearn, M. F.; Erikson, A. I.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Burch, J.; Colangeli, L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Feaga, L. M.; Ferrari, M.; Fornasier, S.; Fulle, M.; Gicquel, A.; Gillon, M.; Green, S. F.; Groussin, O.; Gutiérrez, P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Ivanovski, S.; Jorda, L.; Keller, H. U.; Knight, M. M.; Knollenberg, J.; Koschny, D.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lamy, P. L.; Lara, L. M.; Lazzarin, M.; Lòpez-Moreno, J. J.; Manfroid, J.; Epifani, E. Mazzotta; Marzari, F.; Naletto, G.; Oklay, N.; Palumbo, P.; Parker, J. Wm.; Rickman, H.; Rodrigo, R.; Rodrìguez, J.; Schindhelm, R.; Shi, X.; Sordini, R.; Steffl, A. J.; Stern, S. A.; Thomas, N.; Tubiana, C.; Weaver, H. A.; Weissman, P.; Zakharov, V. V.; Taylor, M. G. G. T. Bibcode: 2016MNRAS.462S.220G Altcode: 2016MNRAS.tmp.1212G On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09:40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors >100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors >10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from ∼-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta (34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (∼25 m s-1) while 100 μm radius particles were detected by the GIADA dust instrument ∼1 h later at a speed of 6 m s-1. The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined. Title: Detection of exposed H2O ice on the nucleus of comet 67P/Churyumov-Gerasimenko. as observed by Rosetta OSIRIS and VIRTIS instruments Authors: Barucci, M. A.; Filacchione, G.; Fornasier, S.; Raponi, A.; Deshapriya, J. D. P.; Tosi, F.; Feller, C.; Ciarniello, M.; Sierks, H.; Capaccioni, F.; Pommerol, A.; Massironi, M.; Oklay, N.; Merlin, F.; Vincent, J. -B.; Fulchignoni, M.; Guilbert-Lepoutre, A.; Perna, D.; Capria, M. T.; Hasselmann, P. H.; Rousseau, B.; Barbieri, C.; Bockelée-Morvan, D.; Lamy, P. L.; De Sanctis, C.; Rodrigo, R.; Erard, S.; Koschny, D.; Leyrat, C.; Rickman, H.; Drossart, P.; Keller, H. U.; A'Hearn, M. F.; Arnold, G.; Bertaux, J. -L.; Bertini, I.; Cerroni, P.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; El-Maarry, M. R.; Fonti, S.; Fulle, M.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip, W.; Jorda, L.; Kappel, D.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Mancarella, F.; Marzari, F.; Mottola, S.; Naletto, G.; Pajola, M.; Palomba, E.; Quirico, E.; Schmitt, B.; Thomas, N.; Tubiana, C. Bibcode: 2016A&A...595A.102B Altcode: 2016arXiv160900551B Context. Since the orbital insertion of the Rosetta spacecraft, comet 67P/Churyumov-Gerasimenko (67P) has been mapped by OSIRIS camera and VIRTIS spectro-imager, producing a huge quantity of images and spectra of the comet's nucleus.
Aims: The aim of this work is to search for the presence of H2O on the nucleus which, in general, appears very dark and rich in dehydrated organic material. After selecting images of the bright spots which could be good candidates to search for H2O ice, taken at high resolution by OSIRIS, we check for spectral cubes of the selected coordinates to identify these spots observed by VIRTIS.
Methods: The selected OSIRIS images were processed with the OSIRIS standard pipeline and corrected for the illumination conditions for each pixel using the Lommel-Seeliger disk law. The spots with higher I/F were selected and then analysed spectrophotometrically and compared with the surrounding area. We selected 13 spots as good targets to be analysed by VIRTIS to search for the 2 μm absorption band of water ice in the VIRTIS spectral cubes.
Results: Out of the 13 selected bright spots, eight of them present positive H2O ice detection on the VIRTIS data. A spectral analysis was performed and the approximate temperature of each spot was computed. The H2O ice content was confirmed by modeling the spectra with mixing (areal and intimate) of H2O ice and dark terrain, using Hapke's radiative transfer modeling. We also present a detailed analysis of the detected spots. Title: Geomorphological mapping of comet 67P/Churyumov-Gerasimenko's Southern hemisphere Authors: Lee, Jui-Chi; Massironi, Matteo; Ip, Wing-Huen; Giacomini, Lorenza; Ferrari, Sabrina; Penasa, Luca; El-Maarry, Mohamed Ramy; Pajola, Maurizio; Lai, Ian-Lin; Lin, Zhong-Yi; Ferri, Francesca; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F.; Barucci, Maria Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Deller, Jakob; Fornasier, Sonia; Fulle, Marco; Groussin, Olivier; Gutiérrez, Pedro J.; Güttler, Carsten; Hofmann, Marc; Hviid, Stubbe F.; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor; Kramm, J. -Rainer; Kührt, Ekkehard; Küppers, Michael; Lara, Luisa M.; Lazzarin, Monica; Marzari, Francesco; Lopez Moreno, Josè J.; Naletto, Giampiero; Oklay, Nilda; Shi, Xian; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste Bibcode: 2016MNRAS.462S.573L Altcode: In 2015 May, the Southern hemisphere of comet 67P/Churyumov-Gerasimenko became visible by the OSIRIS cameras on-board the Rosetta spacecraft. The resolution was high enough to carry out a detailed analysis of the surface morphology, which is quite different from the Northern hemisphere. Previous works show that fine particle deposits are the most extensive geological unit in the Northern hemisphere. In contrast, the Southern hemisphere is dominated by outcropping consolidated terrain. In this work, we provide geomorphological maps of the Southern hemisphere with the distinction of both geological units and linear features. The geomorphological maps described in this study allow us to gain a better understanding of the processes shaping the comet nucleus and the distribution of primary structures such as fractures and strata. Title: Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta Authors: Gicquel, A.; Vincent, J. -B.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Bodewits, D.; Sierks, H.; Lin, Z. -Y.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux, J. -L.; Besse, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; Frattin, E.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hu, X.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Lowry, S.; Marzari, F.; Masoumzadeh, N.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C. Bibcode: 2016MNRAS.462S..57G Altcode: 2016arXiv160808774G; 2016MNRAS.tmp.1233G Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 μm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data, we needed to inject a number of aggregates between 8.5 × 1013 and 8.5 × 1010 for a = 5 and 50 μm, respectively, or an initial mass of H2O ice around 22 kg. Title: 67P/C-G inner coma dust properties from 2.2 au inbound to 2.0 au outbound to the Sun Authors: Della Corte, V.; Rotundi, A.; Fulle, M.; Ivanovski, S.; Green, S. F.; Rietmeijer, F. J. M.; Colangeli, L.; Palumbo, P.; Sordini, R.; Ferrari, M.; Accolla, M.; Zakharov, V.; Mazzotta Epifani, E.; Weissman, P.; Gruen, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Palomba, E.; Perrin, J. M.; Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Ortiz, J. L.; Jeronimo, J. M.; Leese, M. R.; Herranz, M.; Liuzzi, V.; Lopez-Jimenez, A. C. Bibcode: 2016MNRAS.462S.210D Altcode: 2016MNRAS.tmp.1514D GIADA (Grain Impact Analyzer and Dust Accumulator) on-board the Rosetta space probe is designed to measure the momentum, mass and speed of individual dust particles escaping the nucleus of comet 67P/Churyumov-Gerasimenko (hereafter 67P). From 2014 August to 2016 June, Rosetta escorted comet 67P during its journey around the Sun. Here, we focus on GIADA data taken between 2015 January and 2016 February which included 67P's perihelion passage. To better understand cometary activity and more specifically the presence of dust structures in cometary comae, we mapped the spatial distribution of dust density in 67P's coma. In this manner, we could track the evolution of high-density regions of coma dust and their connections with nucleus illumination conditions, namely tracking 67P's seasons. We also studied the link between dust particle speeds and their masses with respect to heliocentric distance, I.e. the level of cometary activity. This allowed us to derive a global and a local correlation of the dust particles' speed distribution with respect to the H2O production rate. Title: Modelling of the outburst on July 29th , 2015 observed with OSIRIS in the southern hemisphere of comet 67P/Churyumov-Gerasimenko Authors: Gicquel, Adeline; Vincent, Jean-Baptiste; Sierks, Holger; Rose, Martin; Agarwal, Jessica; Deller, Jakob; Guettler, Carsten; Hoefner, Sebastian; Hofmann, Marc; Hu, Xuanyu; Kovacs, Gabor; Oklay Vincent, Nilda; Shi, Xian; Tubiana, Cecilia; Barbieri, Cesare; Lamy, Phylippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; OSIRIS Team Bibcode: 2016DPS....4811614G Altcode: Images of the nucleus and the coma (gas and dust) of comet 67P/Churyumov- Gerasimenko have been acquired by the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras system since March 2014 using both the wide angle camera (WAC) and the narrow angle camera (NAC). We are using the NAC camera to study the bright outburst observed on July 29th, 2015 in the southern hemisphere. The NAC camera's wavelength ranges between 250-1000 nm with a combination of 12 filters. The high spatial resolution is needed to localize the source point of the outburst on the surface of the nucleus. At the time of the observations, the heliocentric distance was 1.25AU and the distance between the spacecraft and the comet was 126 km. We aim to understand the physics leading to such outgassing: Is the jet associated to the outbursts controlled by the micro-topography? Or by ice suddenly exposed? We are using the Direct Simulation Monte Carlo (DSMC) method to study the gas flow close to the nucleus. The goal of the DSMC code is to reproduce the opening angle of the jet, and constrain the outgassing ratio between outburst source and local region. The results of this model will be compared to the images obtained with the NAC camera. Title: Comet 67P as seen by Rosetta/OSIRIS Authors: Guettler, Carsten; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; OSIRIS Team Bibcode: 2016DPS....4820102G Altcode: In September 2016, the ESA Rosetta mission will come to its ending. Having escorted comet 67P for more than two years, the scientific camera system OSIRIS onboard Rosetta witnessed all important milestones of the mission: after the first characterization and the Philae landing we saw the comet's activity increasing while it was approaching the Sun. During the peak of activity around perihel in August 2015, the spacecraft had to retreat to a safe distance but we witnessed strong but predictable jet activity and, at the same time, short lived eruptions, some of these being big outbursts. When the activity declined post perihelion and allowed the spacecraft to go back closer, comparison with the early characterization revealed numerous morphologic changes on the surface, which can be attributed to the strong activity during perihelion passage.The paper will give an overview of latest OSIRIS science and discoveries including the morphology, activity, and surface changes mentioned above. Implications on the nature of the comet and its mechanisms will be drawn from these. The current plan for the mission is to go to very close distances in August and September 2016 and finally land the spacecraft on 67P.Acknowledgements: OSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany.We thank the Rosetta Science Ground Segment at ESAC, the Rosetta Mission Operations Centre at ESOC and the Rosetta Project at ESTEC for their outstanding work enabling the science return of the Rosetta Mission. Title: The global shape, density and rotation of Comet 67P/Churyumov-Gerasimenko from preperihelion Rosetta/OSIRIS observations Authors: Jorda, L.; Gaskell, R.; Capanna, C.; Hviid, S.; Lamy, P.; Ďurech, J.; Faury, G.; Groussin, O.; Gutiérrez, P.; Jackman, C.; Keihm, S. J.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Marchi, S.; Mottola, S.; Palmer, E.; Schloerb, F. P.; Sierks, H.; Vincent, J. -B.; A'Hearn, M. F.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Güttler, C.; Ip, W. -H.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Thomas, N.; Tubiana, C.; Wenzel, K. -P. Bibcode: 2016Icar..277..257J Altcode: The Rosetta spacecraft reached Comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) in August 2014 at an heliocentric distance of 3.6 a.u. and was then put in orbit around its nucleus to perform detailed observations. Among the collected data are the images acquired by the OSIRIS instrument up to the perihelion passage of the comet in August 2015, which allowed us to map the entire nucleus surface at high-resolution in the visible. Stereophotoclinometry methods have been used to reconstruct a global high-resolution shape model and to monitor its rotational parameters using data collected up to perihelion.

The nucleus has a conspicuous bilobate shape with overall dimensions along its principal axes of (4.34 ± 0.02) × (2.60 ± 0.02) × (2.12 ± 0.06) km. The best-fit ellipsoid dimensions of the individual lobes along their principal axes of inertia are found to be 4.10 × 3.52 × 1.63 km and 2.50 × 2.14 × 1.64 km. Their volume amounts to 66% and 27% of the total volume of the nucleus. The two lobes are connected by a "neck" whose volume has been estimated to represent ∼7% of the total volume of the comet. Combining the derived volume of 18.8 ± 0.3 km3 with the mass of 9.982 ± 0.003 × 1012 kg determined by the Rosetta/RSI experiment, we obtained a bulk density of the nucleus of 532 ± 7 kg m-3 . Together with the companion value of 535 ± 35 kg m-3 deduced from the stereophotogrammetry shape model of the nucleus (Preusker et al. [2015] Astron. Astrophys. 583, A33), these constitute the first reliable and most accurate determination of the density of a cometary nucleus to date. The calculated porosity is quite large, ranging approximately from 70% to 75% depending upon the assumed density of the dust grains and the dust-to-ice mass ratio. The nature of the porosity, either micro or macro or both, remains unconstrained. The coordinates of the center of gravity are not compatible with a uniform nucleus density. The direction of the offset between the center of gravity and the center of figure suggests that the big lobe has a slightly higher bulk density compared to the small one. the center of mass position cannot be explained by different, but homogenous densities in the two lobes.

The initial rotational period of 12.4041 ± 0.0001 h of the nucleus persisted until October 2014. It then slightly increased to a maximum of 12.4304 h reached on 19 May 2015 and finally dropped to 12.305 h just before perihelion on August 10, 2015. A periodogram analysis of the (RA, Dec) direction of the Z-axis of the comet obtained in parallel with the shape reconstruction exhibits a highly significant minima at 11.5 ± 0.5 day clearly indicating an excited rotational state with an amplitude of 0.15 ± 0.03°. Title: Reconstruction of the Abydos ROSETTA/Philae landing site at very high spatial resolution Authors: Capanna, Claire; Jorda, Laurent; Lamy, Philippe L.; Gaskell, Robert W.; FAURY, Guillaume; DELMAS, Cédric; DURAND, Joelle; GAUDON, Philippe; GARMIER, Romain; JURADO, Eric; OSIRIS Team Bibcode: 2016DPS....4811006C Altcode: The Rosetta/Philae module landed in a very uneven area called Abydos. The landing site has beenidentified on images of this region acquired by the OSIRIS imaging system aboard the orbiterbefore (Oct. 2014) and after (Dec. 2014) the landing (Lamy et al., in prep.).Abydos exhibits a complex topography including numerous cliffs, several overhangs and lots ofboulders (Lucchetti et al. A&A 585, L1, 2016). This makes its reconstruction a challenging taskfor 3D reconstruction techniques.We use a very carefully selected set of high-resolution OSIRIS images acquired betweenMarch 2016 and August 2016 to reconstruct the detailed topography of the Abydos neighborhoodusing a method called ``multiresolution photoclinometry by deformation'' (MPCD, Capanna et al.,The Visual Computer, 29(6-8): 825-835, 2013). We also check the compatibility of the local DTMcomparing the panoramic images obtained by the CIVA-P instrument aboard PHILAE with syntheticimages created with the DTM, and we compute the distances, incidence and emission angles duringthe acquisition of these images. Title: Time-dependent tomographic reconstruction of the solar corona Authors: Vibert, D.; Peillon, C.; Lamy, P.; Frazin, R. A.; Wojak, J. Bibcode: 2016A&C....17..144V Altcode: 2016arXiv160706308V Solar rotational tomography (SRT) applied to white-light coronal images observed at multiple aspect angles has been the preferred approach for determining the three-dimensional (3D) electron density structure of the solar corona. However, it is seriously hampered by the restrictive assumption that the corona is time-invariant which introduces significant errors in the reconstruction. We first explore several methods to mitigate the temporal variation of the corona by decoupling the "fast-varying" inner corona from the "slow-moving" outer corona using multiple masking (either by juxtaposition or recursive combination) and radial weighting. Weighting with a radial exponential profile provides some improvement over a classical reconstruction but only beyond ≈ 3R⊙. We next consider a full time-dependent tomographic reconstruction involving spatio-temporal regularization and further introduce a co-rotating regularization aimed at preventing concentration of reconstructed density in the plane of the sky. Crucial to testing our procedure and properly tuning the regularization parameters is the introduction of a time-dependent MHD model of the corona based on observed magnetograms to build a time-series of synthetic images of the corona. Our procedure, which successfully reproduces the time-varying model corona, is finally applied to a set of 53 LASCO-C2 pB images roughly evenly spaced in time from 15 to 29 March 2009. Our procedure paves the way to a time-dependent tomographic reconstruction of the coronal electron density to the whole set of LASCO-C2 images presently spanning 20 years. Title: Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images: The southern hemisphere Authors: El-Maarry, M. R.; Thomas, N.; Gracia-Berná, A.; Pajola, M.; Lee, J. -C.; Massironi, M.; Davidsson, B.; Marchi, S.; Keller, H. U.; Hviid, S. F.; Besse, S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Koschny, D.; Rickman, H.; Rodrigo, R.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; De Cecco, M.; Debei, S.; Güttler, C.; Fornasier, S.; Fulle, M.; Giacomini, L.; Groussin, O.; Gutierrez, P. J.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marschall, R.; Marzari, F.; Naletto, G.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J. -B. Bibcode: 2016A&A...593A.110E Altcode:
Aims: The OSIRIS camera on board the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)'s nucleus since August 2014. Starting in May 2015, the southern hemisphere gradually became illuminated and was imaged for the first time. Here we present the regional morphology of the southern hemisphere, which serves as a companion to an earlier paper that presented the regional morphology of the northern hemisphere.
Methods: We used OSIRIS images that were acquired at orbits ~45-125 km from the center of the comet (corresponding to spatial resolutions of ~0.8 to 2.3 m/pixel) coupled with the use of digital terrain models to define the different regions on the surface, and identify structural boundaries accurately.
Results: Seven regions have been defined in the southern hemisphere bringing the total number of defined regions on the surface of the nucleus to 26. These classifications are mainly based on morphological and/or topographic boundaries. The southern hemisphere shows a remarkable dichotomy with its northern counterpart mainly because of the absence of wide-scale smooth terrains, dust coatings and large unambiguous depressions. As a result, the southern hemisphere closely resembles previously identified consolidated regions. An assessment of the overall morphology of comet 67P suggests that the comet's two lobes show surface heterogeneities manifested in different physical/mechanical characteristics, possibly extending to local (I.e., within a single region) scales. Title: A small mission concept to the Sun-Earth Lagrangian L5 point for innovative solar, heliospheric and space weather science Authors: Lavraud, B.; Liu, Y.; Segura, K.; He, J.; Qin, G.; Temmer, M.; Vial, J. -C.; Xiong, M.; Davies, J. A.; Rouillard, A. P.; Pinto, R.; Auchère, F.; Harrison, R. A.; Eyles, C.; Gan, W.; Lamy, P.; Xia, L.; Eastwood, J. P.; Kong, L.; Wang, J.; Wimmer-Schweingruber, R. F.; Zhang, S.; Zong, Q.; Soucek, J.; An, J.; Prech, L.; Zhang, A.; Rochus, P.; Bothmer, V.; Janvier, M.; Maksimovic, M.; Escoubet, C. P.; Kilpua, E. K. J.; Tappin, J.; Vainio, R.; Poedts, S.; Dunlop, M. W.; Savani, N.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard, T.; DeForest, C.; Webb, D.; Lugaz, N.; Fuselier, S. A.; Dalmasse, K.; Tallineau, J.; Vranken, D.; Fernández, J. G. Bibcode: 2016JASTP.146..171L Altcode: We present a concept for a small mission to the Sun-Earth Lagrangian L5 point for innovative solar, heliospheric and space weather science. The proposed INvestigation of Solar-Terrestrial Activity aNd Transients (INSTANT) mission is designed to identify how solar coronal magnetic fields drive eruptions, mass transport and particle acceleration that impact the Earth and the heliosphere. INSTANT is the first mission designed to (1) obtain measurements of coronal magnetic fields from space and (2) determine coronal mass ejection (CME) kinematics with unparalleled accuracy. Thanks to innovative instrumentation at a vantage point that provides the most suitable perspective view of the Sun-Earth system, INSTANT would uniquely track the whole chain of fundamental processes driving space weather at Earth. We present the science requirements, payload and mission profile that fulfill ambitious science objectives within small mission programmatic boundary conditions. Title: The primordial nucleus of comet 67P/Churyumov-Gerasimenko Authors: Davidsson, B. J. R.; Sierks, H.; Güttler, C.; Marzari, F.; Pajola, M.; Rickman, H.; A'Hearn, M. F.; Auger, A. -T.; El-Maarry, M. R.; Fornasier, S.; Gutiérrez, P. J.; Keller, H. U.; Massironi, M.; Snodgrass, C.; Vincent, J. -B.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Feller, C.; Fulle, M.; Groussin, O.; Hviid, S. F.; Höfner, S.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Moissl-Fraund, R.; Mottola, S.; Naletto, G.; Oklay, N.; Thomas, N.; Tubiana, C. Bibcode: 2016A&A...592A..63D Altcode: Context. We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model.
Aims: Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations.
Methods: We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics.
Results: We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO2; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these observed properties, and additionally explains the presence of extensive layering on 67P/Churyumov-Gerasimenko (and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape, the extremely slow growth of comet nuclei as evidenced by recent radiometric dating, and the low collision probability that allows primordial nuclei to survive the age of the solar system.
Conclusions: We conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles. We argue that TNOs formed as a result of streaming instabilities at sizes below ~400 km and that ~350 of these grew slowly in a low-mass primordial disk to the size of Triton, Pluto, and Eris, causing little viscous stirring during growth. We thus propose a dynamically cold primordial disk, which prevented medium-sized TNOs from breaking into collisional rubble piles and allowed the survival of primordial rubble-pile comets. We argue that comets formed by hierarchical agglomeration out of material that remained after TNO formation, and that this slow growth was a necessity to avoid thermal processing by short-lived radionuclides that would lead to loss of supervolatiles, and that allowed comet nuclei to incorporate ~3 Myr old material from the inner solar system. Title: The southern hemisphere of 67P/Churyumov-Gerasimenko: Analysis of the preperihelion size-frequency distribution of boulders ≥7 m Authors: Pajola, Maurizio; Lucchetti, Alice; Vincent, Jean-Baptiste; Oklay, Nilda; El-Maarry, Mohamed R.; Bertini, Ivano; Naletto, Giampiero; Lazzarin, Monica; Massironi, Matteo; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst U.; Agarwal, Jessica; A'Hearn, Michael F.; Barucci, Maria A.; Bertaux, Jean-Loup; Boudreault, Steve; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Deller, Jakob; Fornasier, Sonia; Fulle, Marco; Gicquel, Adeline; Groussin, Olivier; Gutierrez, Pedro J.; Güttler, Carsten; Hofmann, Marc; Höfner, Sebastian; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kramm, J. -Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lee, Jui-Chi; Lin, Zhong-Yi; Lopez Moreno, Jose J.; Marzari, Francesco; Michalik, Harald; Mottola, Stefano; Preusker, Frank; Scholten, Frank; Thomas, Nicholas; Toth, Imre; Tubiana, Cecilia Bibcode: 2016A&A...592L...2P Altcode:
Aims: We calculate the size-frequency distribution of the boulders on the southern hemisphere of comet 67P Churyumov-Gerasimenko (67P), which was in shadow before the end of April 2015. We compare the new results with those derived from the northern hemisphere and equatorial regions of 67P, highlighting the possible physical processes that lead to these boulder size distributions.
Methods: We used images acquired by the OSIRIS Narrow Angle Camera (NAC) on 2 May 2015 at a distance of 125 km from the nucleus. The scale of this dataset is 2.3 m/px; the high resolution of the images, coupled with the favorable observation phase angle of 62°, provided the possibility to unambiguously identify boulders ≥7 m on the surface of 67P and to manually extract them with the software ArcGIS. We derived the size-frequency distribution of the illuminated southern hemisphere.
Results: We found a power-law index of -3.6 ± 0.2 for the boulders on the southern hemisphere with a diameter range of 7-35 m. The power-law index is equal to the one previously found on northern and equatorial regions of 67P, suggesting that similar boulder formation processes occur in both hemispheres. The power-law index is related to gravitational events triggered by sublimation and/or thermal fracturing causing regressive erosion. In addition, the presence of a larger number of boulders per km2 in the southern hemisphere, which is a factor of 3 higher with respect to the northern hemisphere, suggests that the southernmost terrains of 67P are affected by a stronger thermal fracturing and sublimating activity, hence possibly causing larger regressive erosion and gravitational events. Title: Aswan site on comet 67P/Churyumov-Gerasimenko: Morphology, boulder evolution, and spectrophotometry Authors: Pajola, Maurizio; Oklay, Nilda; La Forgia, Fiorangela; Giacomini, Lorenza; Massironi, Matteo; Bertini, Ivano; El-Maarry, M. R.; Marzari, Francesco; Preusker, Frank; Scholten, Frank; Höfner, Sebastian; Lee, Jui-Chi; Vincent, Jean-Baptiste; Groussin, Olivier; Naletto, Giampiero; Lazzarin, Monica; Barbieri, Cesare; Sierks, Holger; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst U.; Agarwal, Jessica; A'Hearn, Michael F.; Barucci, Maria A.; Bertaux, Jean-Loup; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; De Cecco, Mariolino; Debei, Stefano; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Güttler, Carsten; Gutierrez, Pedro J.; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kramm, J. -Rainer; Küppers, Michael; Kürt, Ekkehard; Lara, Luisa M.; Lin, Zhong-Yi; Lopez Moreno, Jose J.; Magrin, Sara; Michalik, Harald; Mottola, Stefano; Thomas, Nicholas; Tubiana, Cecilia Bibcode: 2016A&A...592A..69P Altcode:
Aims: We provide a detailed morphological analysis of the Aswan site on comet 67P/Churyumov-Gerasimenko (67P). We derive the size-frequency distribution of boulders ≥2 m and correlate this distribution with the gravitational slopes for the first time on a comet. We perform the spectral analysis of this region to understand if possible surface variegation is related to thedifferent surface textures observable on the different units.
Methods: We used two OSIRIS Narrow Angle Camera (NAC) image data sets acquired on September 19 and 22, 2014, with a scale of 0.5 m/px. Gravitational slopes derived from the 3D shape model of 67P were used to identify and interpret the different units of the site. By means of the high-resolution NAC data sets, boulders ≥2.0 m can be unambiguously identified and extracted using the software ArcGIS. Coregistered and photometrically corrected color cubes were used to perform the spectral analyses, and we retrieved the spectral properties of the Aswan units.
Results: The high-resolution morphological map of the Aswan site (0.68 km2) shows that this site is characterized by four different units: fine-particle deposits located on layered terrains, gravitational accumulation deposits, taluses, and the outcropping layered terrain. Multiple lineaments are identified on the Aswan cliff, such as fractures, exposed layered outcrops, niches, and terraces. Close to the terrace margin, several arched features observed in plan view suggest that the margin progressively retreats as a result of erosion. The size-frequency of boulders ≥2 m in the entire study area has a power-law index of -3.9 +0.2/-0.3 (1499 boulders ≥2 m/km2), suggesting that the Aswan site is mainly dominated by gravitational events triggered by sublimation and/or thermal insolation weathering causing regressive erosion. The boulder size-frequency distribution versus gravitational slopes indicates that when higher gravitational slope terrains are considered, only boulders ≤10 m are identified, as well as steeper power-slope indices. In addition, no boulders ≥2 m are observed on slopes ≥50°. This may indicate that larger blocks detached from a sublimating cliff cannot rest at these slopes and consequently fall down. The spectral analysis performed on the site shows that despite different morphologic units, no spectral differences appear in the multiple textures. This may confirm a redistribution of particles across the nucleus as a consequence of airfall, whether coming from Hapi or from the southern hemisphere when it is active during perihelion. Title: Prominence material embedded in coronal mass ejections as observed with the LASCO-C2 coronagraph using polarization diagnostic Authors: Lamy, Philippe; Boclet, Brice; Koutchmy, Serge Bibcode: 2016cosp...41E1107L Altcode: Prominences are believed to be caused by the formation of a flux rope low in the magnetic structure that eventually erupts to form the CME. Indeed, many CME onset models (e.g., flux cancellation, mass loading) require the presence or formation of a prominence in order for the CME to erupt. The remnants of the cool prominence material is often seen as recognizable twisted structures inside the CME in the lines of He II at 304 Å, of D3 HeI at 587.5 nm, and of Hα at 656 nm, sometime up to a distance of several solar radii from the surface in the latter lines. The orange filter of the LASCO-C2 coronagraph includes the D3 HeI line and its presence in the core of CMEs can be unambiguously detected on polarized images as polarization allows disentangling the contributions from the hot coronal plasma (the polarized Thomson scattered light by electrons) and from the unpolarised emission of cool prominence material. This has been made possible by an in-depth calibration that removes adverse instrumental effects. We will show several examples of CME with embedded prominence material and we will attempt to estimate the mass of this material to be compared with that of the CME. We will also exploit the polarization measurements to reconstruct the 3D geometry of the observed CMEs. Title: Coronal mass ejections over solar cycle 23 and 24 from LASCO-C2 white-light images Authors: Lamy, Philippe; Barlyaeva, Tatiana; Boclet, Brice Bibcode: 2016cosp...41E1108L Altcode: It is now well established that coronal mass ejections (CMEs) play a major role in the heliosphere, starting from the corona to interplanetary space and interacting with planets. The almost uninterrupted observations by the LASCO coronagraph onboard SOHO since January 1996 have allowed an unprecedented view of CMEs over almost two solar cycles 23 and 24. The ARTEMIS-II catalog based on their automatic detection on high-quality calibrated synoptic maps of the corona offers a dataset free of selection effects. It is thus possible to perform an unbiased statistical analysis of their properties and investigate how they evolve with solar activity. We will present an extended comparison of their properties during the two solar cycles 23 and 24 emphasizing the differences. We will further compare them with those of the standard indices of solar activity such as the international sunspot number (SSN), the sunspot area (SSA) and the radio flux at 10.7 cm (F10.7) as well as those of their potential progenitors, flares and eruptive prominences, in order to ascertain their connection, and we will consider the two hemispheres separately whenever possible. Title: Detection of changes of the surface morphology of the nucleus of comet 67P/Churyumov-Gerasimenko - Implications for the erosion Authors: Lamy, Philippe; Groussin, Olivier; El-Maarry, M. R.; Faury, Guillaume; Auger, Anne-Thérèse Bibcode: 2016cosp...41E1109L Altcode: Search for morphological changes at the surface of the nucleus of comet 67P/Churyumov-Gerasimenko (67/P C-G) since its perihelion passage in August 2015 has been a major objective of the OSIRIS team in order to understand the erosion processes. At time of writing, the changes detected so far at a distance of 48 km (that is a pixel scale of 90 cm for the OSIRIS Narrow Angle Camera) are subtle even in regions which were the most exposed to solar illumination around perihelion time: Imhotep, Khonsu and Khepry. In this presentation, we will concentrate on the Khepry region where several changes of different kinds have been positively detected: disappearance of several bright spots, localized receding of a large part (roughly 40 x 130 m) of the surface by approximately 12 m (that could result from either erosion or localized collapse), and appearance of several new boulders. As the Rosetta-comet distance will keep decreasing, we hope to report further changes at the COSPAR conference. We will finally confront quantitative estimates of the putative eroded mass with independent evidences coming from in-situ as well as remote-sensing observations carried over several past apparitions. Title: Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko Authors: Ip, W. -H.; Lai, I. -L.; Lee, J. -C.; Cheng, Y. -C.; Li, Y.; Lin, Z. -Y.; Vincent, J. -B.; Besse, S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Lowry, S.; Marchi, S.; Marzari, F.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Thomas, N.; Toth, E.; Tubiana, C. Bibcode: 2016A&A...591A.132I Altcode:
Aims: We aim to characterize the circular depressions of comet 67P/Churyumov-Gerasimenko and investigate whether such surface morphology of a comet nucleus is related to the cumulative sublimation effect since becoming a Jupiter family comet (JFC).
Methods: The images from the Rosetta/OSIRIS science camera experiment are used to construct size frequency distributions of the circular depression structures on comet 67P and they are compared with those of the JFCs 81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2. The orbital evolutionary histories of these comets over the past 100 000 yr are analyzed statistically and compared with each other.
Results: The global distribution of the circular depressions over the surface of 67P is charted and classified. Descriptions are given to the characteristics and cumulative size frequency distribution of the identified features. Orbital statistics of the JFCs visited by spacecraft are derived.
Conclusions: The size frequency distribution of the circular depressions is found to have a similar power law distribution to those of 9P/Tempel 1 and 81P/Wild 2. This might imply that they could have been generated by the same process. Orbital integration calculation shows that the surface erosion histories of 81P/Wild 2, and 9P/Tempel 1 could be shorter than those of 67P, 103 P/Hartley 2 and 19P/Borrelly. From this point of view, the circular depressions could be dated back to the pre-JFC phase or the transneptunian phase of these comets. The north-south asymmetry in the distribution of the circular depressions could be associated with the heterogeneous structure of the nucleus of comet 67P and/or the solar insolation history. Title: Possible interpretation of the precession of comet 67P/Churyumov-Gerasimenko Authors: Gutiérrez, P. J.; Jorda, L.; Gaskell, R. W.; Davidsson, B. J. R.; Capanna, C.; Hviid, S. F.; Keller, H. U.; Maquet, L.; Mottola, S.; Preusker, F.; Scholten, F.; Lara, L. M.; Moreno, F.; Rodrigo, R.; Sierks, H.; Barbieri, C.; Lamy, P.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Auger, A. T.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez-Marques, P.; Güttler, C.; Ip, W. H.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.; López-Moreno, J. J.; Magrin, S.; Marchi, S.; Marzari, F.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Sabau, D.; Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. B. Bibcode: 2016A&A...590A..46G Altcode: Context. Data derived from the reconstruction of the nucleus shape of comet 67P/Churyumov-Gerasimenko (67P) from images of the OSIRIS camera onboard ROSETTA show evidence that the nucleus rotates in complex mode. First, the orientation of the spin axis is not fixed in an inertial reference frame, which suggests a precessing motion around the angular momentum vector with a periodicity of approximately 257 h ± 12 h.Second, periodograms of the right ascension and declination (RA/Dec) coordinates of the body-frame Z axis show a very significant (higher than 99.99%) periodicity at 276 h ± 12 h, different from the rotational period of 12.40 h as previously determined from light-curve analysis.
Aims: The main goal is to interpret the data and associated periodicities of the spin axis orientation in space.
Methods: We analyzed the spin axis orientation in space and associated periodicities and compared them with solutions of Euler equations under the assumption that the body rotates in torque-free conditions. Statistical tests comparing the observationally derived spin axis orientation with the outcome from simulations were applied to determine the most likely inertia moments, excitation level, and periods.
Results: Under the assumption that the body is solid-rigid and rotates in torque-free conditions, the most likely interpretation is that 67P is spinning around the principal axis with the highest inertia moment with a period of about 13 h. At the same time, the comet precesses around the angular momentum vector with a period of about 6.35 h. While the rotating period of such a body would be about 12.4 h, RA/Dec coordinates of the spin axis would have a periodicity of about 270 h as a result of the combination of the two aforementioned motions.
Conclusions: The most direct and simple interpretation of the complex rotation of 67P requires a ratio of inertia moments significantly higher than that of a homogeneous body. Title: Subsurface Characterization of 67P/Churyumov-Gerasimenko’s Abydos Site Authors: Brugger, B.; Mousis, O.; Morse, A.; Marboeuf, U.; Jorda, L.; Guilbert-Lepoutre, A.; Andrews, D.; Barber, S.; Lamy, P.; Luspay-Kuti, A.; Mandt, K.; Morgan, G.; Sheridan, S.; Vernazza, P.; Wright, I. P. Bibcode: 2016ApJ...822...98B Altcode: 2016arXiv160305893B On 2014 November 12, the ESA/Rosetta descent module Philae landed on the Abydos site of comet 67P/Churyumov-Gerasimenko. Aboard this module, the Ptolemy mass spectrometer measured a CO/CO2 ratio of 0.07 ± 0.04, which differs substantially from the value obtained in the coma by the Rosetta/ROSINA instrument, suggesting a heterogeneity in the comet nucleus. To understand this difference, we investigated the physicochemical properties of the Abydos subsurface, leading to CO/CO2 ratios close to that observed by Ptolemy at the surface of this region. We used a comet nucleus model that takes into account different water ice phase changes (amorphous ice, crystalline ice, and clathrates) as well as diffusion of molecules throughout the pores of the matrix. The input parameters of the model were optimized for the Abydos site, and the ROSINA CO/CO2 measured ratio is assumed to correspond to the bulk value in the nucleus. We find that all considered structures of water ice are able to reproduce the Ptolemy observation with a time difference not exceeding ∼50 days, I.e., lower than ∼2% on 67P/Churyumov-Gerasimenko’s orbital period. The suspected heterogeneity of 67P/Churyumov-Gerasimenko’s nucleus is also found possible only if it is constituted of crystalline ices. If the icy phase is made of amorphous ice or clathrates, the difference between Ptolemy and ROSINA’s measurements would rather originate from the spatial variations in illumination on the nucleus surface. An eventual new measurement of the CO/CO2 ratio at Abydos by Ptolemy could be decisive to distinguish between the three water ice structures. Title: Extreme 3D reconstruction of the final ROSETTA/PHILAE landing site Authors: Capanna, Claire; Jorda, Laurent; Lamy, Philippe; Gesquiere, Gilles; Delmas, Cédric; Durand, Joelle; Garmier, Romain; Gaudon, Philippe; Jurado, Eric Bibcode: 2016EGUGA..18.4522C Altcode: The Philae lander aboard the Rosetta spacecraft successfully landed at the surface of comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) after two rebounds on November 12, 2014. The final landing site, now known as « Abydos », has been identified on images acquired by the OSIRIS imaging system onboard the Rosetta orbiter[1]. The available images of Abydos are very limited in number and reveal a very extreme topography containing cliffs and overhangs. Furthermore, the surface is only observed under very high incidence angles of 60° on average, which implies that the images also exhibit lots of cast shadows. This makes it very difficult to reconstruct the 3D topography with standard methods such as photogrammetry or standard clinometry. We apply a new method called ''Multiresolution PhotoClinometry by Deformation'' (MPCD, [2]) to retrieve the 3D topography of the area around Abydos. The method works in two main steps: (i) a DTM of this region is extracted from a low resolution MPCD global shape model of comet 67P/C-G, and (ii) the resulting triangular mesh is progressively deformed at increasing spatial sampling down to 0.25 m in order to match a set of 14 images of Abydos with projected pixel scales between 1 and 8 m. The method used to perform the image matching is a quasi-Newton non-linear optimization method called L-BFGS-b[3] especially suited to large-scale problems. Finally, we also checked the compatibility of the final MPCD digital terrain model with a set of five panoramic images obtained by the CIVA-P instrument aboard Philae[4]. [1] Lamy et al., 2016, submitted. [2] Capanna et al., Three dimensional reconstruction using multiresoluton photoclinometry by deformation, The visual Computer, v. 29(6-8) pp. 825-835, 2013. [3] Morales et al., Remark on "Algorithm 778: L-BFGS-B: Fortran subroutines for large-scale bound constrained optimization", v.38(1) pp.1-4, ACM Trans. Math. Softw., 2011 [4] Bibring et al., 67P/Churyumov-Gerasimenko surface properties as derived from CIVA panoramic images, Science, v. 349(6247), 2015 Title: 20 months at 67P/Churyumov-Gerasimenko: The view from Rosetta/OSIRIS Authors: Sierks, Holger; Güttler, Carsten; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans Bibcode: 2016EGUGA..1815782S Altcode: After arrival in August 2014, the Rosetta spacecraft is now at comet 67P/Churyumov-Gerasimenko for one and a half years. A rather inactive body at that time was approaching the Sun, passing through its perihelion and peak of activity in August/September 2015 and is now moving out, away from the Sun. During the whole time, the comet was observed by the scientific imaging system OSIRIS onboard Rosetta, mapping the nucleus' surface and monitoring the comet's dust and gas coma. This presentation shall summarize the results obtained so far by the OSIRIS team and give a general picture on our current understanding of comets in general and 67P in particular. Title: The State of the Corona During the Weak Solar Cycle 24: the View from LASCO Images Authors: Barlyaeva, T.; Lamy, P.; Llebaria, A.; Boclet, B. Bibcode: 2016ASPC..504..287B Altcode: The LASCO-C2 coronagraph onboard SOHO continues its white-light imaging of the corona from 1.5 to 6.0 solar radii, thus allowing investigating the consequences of the weak Solar Cycle 24 on the corona and comparing it to the previous cycle (23). Temporal variations of the global radiance of the corona are presented. We pay particular attention to the mid-term variations which are distinctly different between the two cycles and highlight the similarities and differences. Finally, we rely on our ARTEMIS II catalog of coronal mass ejections (CMEs) to compare their global rates during these two cycles. Title: Observations and analysis of a curved jet in the coma of comet 67P/Churyumov-Gerasimenko Authors: Lin, Z. -Y.; Lai, I. -L.; Su, C. -C.; Ip, W. -H.; Lee, J. -C.; Wu, J. -S.; Vincent, J. -B.; La Forgia, F.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Lowry, S.; Marzari, F.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Rożek, A.; Thomas, N.; Tubiana, C. Bibcode: 2016A&A...588L...3L Altcode: 2016arXiv160502095L
Aims: We analyze the physical properties and dynamical origin of a curved jet of comet 67P/Churyumov-Gerasimenko that was observed repeatedly in several nucleus rotations starting on May 30 and persisting until early August, 2015.
Methods: We simulated the motion of dust grains ejected from the nucleus surface under the influence of the gravity and viscous drag effect of the expanding gas flow from the rotating nucleus.
Results: The formation of the curved jet is a combination of the size of the dust particles (~0.1-1 mm) and the location of the source region near the nucleus equator. This enhances the spiral feature of the collimated dust stream after the dust is accelerated to a terminal speed on the order of m s-1. Title: Evolution of the Dust Size Distribution of Comet 67P/Churyumov-Gerasimenko from 2.2 au to Perihelion Authors: Fulle, M.; Marzari, F.; Della Corte, V.; Fornasier, S.; Sierks, H.; Rotundi, A.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; López-Moreno, J. J.; Accolla, M.; Agarwal, J.; A'Hearn, M. F.; Altobelli, N.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Bussoletti, E.; Colangeli, L.; Cosi, M.; Cremonese, G.; Crifo, J. -F.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Esposito, F.; Ferrari, M.; Giovane, F.; Gustafson, B.; Green, S. F.; Groussin, O.; Grün, E.; Gutierrez, P.; Güttler, C.; Herranz, M. L.; Hviid, S. F.; Ip, W.; Ivanovski, S. L.; Jerónimo, J. M.; Jorda, L.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Leese, M. R.; López-Jiménez, A. C.; Lucarelli, F.; Mazzotta Epifani, E.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Ortiz, J. L.; Palomba, E.; Palumbo, P.; Perrin, J. -M.; Rietmeijer, F. J. M.; Rodríguez, J.; Sordini, R.; Thomas, N.; Tubiana, C.; Vincent, J. -B.; Weissman, P.; Wenzel, K. -P.; Zakharov, V.; Zarnecki, J. C. Bibcode: 2016ApJ...821...19F Altcode: The Rosetta probe, orbiting Jupiter-family comet 67P/Churyumov-Gerasimenko, has been detecting individual dust particles of mass larger than 10-10 kg by means of the GIADA dust collector and the OSIRIS Wide Angle Camera and Narrow Angle Camera since 2014 August and will continue until 2016 September. Detections of single dust particles allow us to estimate the anisotropic dust flux from 67P, infer the dust loss rate and size distribution at the surface of the sunlit nucleus, and see whether the dust size distribution of 67P evolves in time. The velocity of the Rosetta orbiter, relative to 67P, is much lower than the dust velocity measured by GIADA, thus dust counts when GIADA is nadir-pointing will directly provide the dust flux. In OSIRIS observations, the dust flux is derived from the measurement of the dust space density close to the spacecraft. Under the assumption of radial expansion of the dust, observations in the nadir direction provide the distance of the particles by measuring their trail length, with a parallax baseline determined by the motion of the spacecraft. The dust size distribution at sizes >1 mm observed by OSIRIS is consistent with a differential power index of -4, which was derived from models of 67P’s trail. At sizes <1 mm, the size distribution observed by GIADA shows a strong time evolution, with a differential power index drifting from -2 beyond 2 au to -3.7 at perihelion, in agreement with the evolution derived from coma and tail models based on ground-based data. The refractory-to-water mass ratio of the nucleus is close to six during the entire inbound orbit and at perihelion. Title: Mapping of the source regions of the dust jets on comet 67P Authors: Ip, Wing-Huen; Lai, Ian-Lin; Lee, Jui-Chi; Lin, Zhong-Yi; Chen, Yu; Chien, Ting-Wei; Chen, Yu-Min; Vincent, Jean-Baptiste; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe. L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Uwe; Osiris Team Bibcode: 2016EGUGA..18.5347I Altcode: Because of the inclination of the rotational axis to the orbital plane and the orbital motion around the Sun, the sunlit regions on the nucleus surface of comet 67P/Churyumov-Gerasimenko moved from the northern hemisphere to the sourthern hemisphere between August, 2014 and October, 2015. From the comparison of the dust jet features in images taken at successive time series, the footpoints of these jets can be identified by a projection method. The distributiosn of the corresponding source regions can be compared with the geomorphology of the nucleus surface from inbound to outbound. The correlation of the dust jet activity with the volatile outgassing phenomenon as monitored by different scientific instruments onboard Rosetta will provide important information on the sublimation process. Title: Photometry of dust grains of comet 67P and connection with nucleus regions Authors: Cremonese, G.; Simioni, E.; Ragazzoni, R.; Bertini, I.; La Forgia, F.; Pajola, M.; Oklay, N.; Fornasier, S.; Lazzarin, M.; Lucchetti, A.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fulle, M.; Groussin, O.; Güttler, C.; Gutierrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. -R.; Kueppers, M.; Kürt, E.; Lara, L. M.; Magrin, S.; Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Preusker, F.; Scholten, F.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2016A&A...588A..59C Altcode:
Aims: Multiple pairs of high-resolution images of the dust coma of comet 67P/Churyumov-Gerasimenko have been collected by OSIRIS onboard Rosetta allowing extraction and analysis of dust grain tracks.
Methods: We developed a quasi automatic method to recognize and to extract dust tracks in the Osiris images providing size, FWHM and photometric data. The dust tracks characterized by a low signal-to-noise ratio were checked manually. We performed the photometric analysis of 70 dust grain tracks observed on two different Narrow Angle Camera images in the two filters F24 and F28, centered at λ = 480.7 nm and at λ = 743.7 nm, respectively, deriving the color and the reddening of each one. We then extracted several images of the nucleus observed with the same filters and with the same phase angle to be compared with the dust grain reddening.
Results: Most of the dust grain reddening is very similar to the nucleus values, confirming they come from the surface or subsurface layer. The histogram of the dust grain reddening has a secondary peak at negative values and shows some grains with values higher than the nucleus, suggesting a different composition from the surface grains. One hypothesis comes from the negative values point at the presence of hydrated minerals in the comet. Title: The dust environment of comet 67P/Churyumov-Gerasimenko from Rosetta OSIRIS and VLT observations in the 4.5 to 2.9 AU heliocentric distance range inbound Authors: Moreno, F.; Snodgrass, C.; Hainaut, O.; Tubiana, C.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Ferri, F.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marques, P.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Thomas, N.; Vincent, J. B.; Della Corte, V.; Fitzsimmons, A.; Faggi, S.; Jehin, E.; Opitom, C.; Tozzi, G. -P. Bibcode: 2016A&A...587A.155M Altcode: 2016arXiv160201965M Context. The ESA Rosetta spacecraft, currently orbiting around comet 67P/Churyumov-Gerasimenko, has already provided in situ measurements of the dust grain properties from several instruments,particularly OSIRIS and GIADA. We propose adding value to those measurements by combining them with ground-based observations of the dust tail to monitor the overall, time-dependent dust-production rate and size distribution.
Aims: To constrain the dust grain properties, we take Rosetta OSIRIS and GIADA results into account, and combine OSIRIS data during the approach phase (from late April to early June 2014) with a large data set of ground-based images that were acquired with the ESO Very Large Telescope (VLT) from February to November 2014.
Methods: A Monte Carlo dust tail code, which has already been used to characterise the dust environments of several comets and active asteroids, has been applied to retrieve the dust parameters. Key properties of the grains (density, velocity, and size distribution) were obtained from Rosetta observations: these parameters were used as input of the code to considerably reduce the number of free parameters. In this way, the overall dust mass-loss rate and its dependence on the heliocentric distance could be obtained accurately.
Results: The dust parameters derived from the inner coma measurements by OSIRIS and GIADA and from distant imaging using VLT data are consistent, except for the power index of the size-distribution function, which is α = -3, instead of α = -2, for grains smaller than 1 mm. This is possibly linked to the presence of fluffy aggregates in the coma. The onset of cometary activity occurs at approximately 4.3 AU, with a dust production rate of 0.5 kg/s, increasing up to 15 kg/s at 2.9 AU. This implies a dust-to-gas mass ratio varying between 3.8 and 6.5 for the best-fit model when combined with water-production rates from the MIRO experiment. Title: Are fractured cliffs the source of cometary dust jets? Insights from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko Authors: Vincent, J. -B.; Oklay, N.; Pajola, M.; Höfner, S.; Sierks, H.; Hu, X.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Lowry, S.; Marzari, F.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C. Bibcode: 2016A&A...587A..14V Altcode: 2015arXiv151203193V Context. Dust jets (I.e., fuzzy collimated streams of cometary material arising from the nucleus) have been observed in situ on all comets since the Giotto mission flew by comet 1P/Halley in 1986, and yet their formation mechanism remains unknown. Several solutions have been proposed involving either specific properties of the active areas or the local topography to create and focus the gas and dust flows. While the nucleus morphology seems to be responsible for the larger features, high resolution imagery has shown that broad streams are composed of many smaller jets (a few meters wide) that connect directly to the nucleus surface.
Aims: We monitored these jets at high resolution and over several months to understand what the physical processes are that drive their formation and how this affects the surface.
Methods: Using many images of the same areas with different viewing angles, we performed a 3-dimensional reconstruction of collimated jets and linked them precisely to their sources on the nucleus.
Results: We show here observational evidence that the northern hemisphere jets of comet 67P/Churyumov-Gerasimenko arise from areas with sharp topographic changes and describe the physical processes involved. We propose a model in which active cliffs are the main source of jet-like features and therefore of the regions eroding the fastest on comets. We suggest that this is a common mechanism taking place on all comets. Title: The Comparison of Total Electron Content Between Radio and Thompson Scattering Authors: Jensen, E. A.; Frazin, R.; Heiles, C.; Lamy, P.; Llebaria, A.; Anderson, J. D.; Bisi, M. M.; Fallows, R. A. Bibcode: 2016SoPh..291..465J Altcode: 2016SoPh..tmp....2J The total electron content (TEC) of the solar corona in June 2002 is calculated by three observational techniques and the results are compared. The first technique is solar rotational tomography (SRT) applied to a 14-day time series of LASCO-C2 polarized brightness images, and the other two techniques use the Cassini spacecraft radio beacon for Doppler tracking (phase delay) and ranging (group delay). While the Doppler-tracking technique has an arbitrary zero-point, it is otherwise found that the three methods produce consistent estimates of the TEC to within established uncertainties, providing an independent check on the calibrations. The verification of the accuracy of the Doppler-tracking technique enables a significant improvement to the use of spacecraft data sets in studying the heliosphere: the density component to Faraday rotation can be separated from the magnetic-field component as variable structures cross, such as coronal mass ejections and magnetohydrodynamic waves. Furthermore, we show that the unique frequency-time variable characteristics of the hydrodynamic components of waves can be studied. Based on this work, future Faraday rotation studies of variable solar phenomena will isolate the electron density changes from the magnetic-field contribution. This capability will enable advanced research into variable heliospheric magnetic fields. Title: THERMAP: a mid-infrared spectro-imager for space missions to small bodies in the inner solar system Authors: Groussin, O.; Licandro, J.; Helbert, J.; Reynaud, J. L.; Levacher, P.; Reyes García-Talavera, M.; Alí-Lagoa, V.; Blanc, P. E.; Brageot, E.; Davidsson, B.; Delbó, M.; Deleuze, M.; Delsanti, A.; Diaz Garcia, J. J.; Dohlen, K.; Ferrand, D.; Green, S. F.; Jorda, L.; Joven Álvarez, E.; Knollenberg, J.; Kührt, E.; Lamy, P.; Lellouch, E.; Le Merrer, J.; Marty, B.; Mas, G.; Rossin, C.; Rozitis, B.; Sunshine, J.; Vernazza, P.; Vives, S. Bibcode: 2016ExA....41...95G Altcode: 2015arXiv150902725G; 2015ExA...tmp...56G We present THERMAP, a mid-infrared spectro-imager for space missions to small bodies in the inner solar system, developed in the framework of the MarcoPolo-R asteroid sample return mission. THERMAP is very well suited to characterize the surface thermal environment of a NEO and to map its surface composition. The instrument has two channels, one for imaging and one for spectroscopy: it is both a thermal camera with full 2D imaging capabilities and a slit spectrometer. THERMAP takes advantage of the recent technological developments of uncooled microbolometer arrays, sensitive in the mid-infrared spectral range. THERMAP can acquire thermal images (8-18 μm) of the surface and perform absolute temperature measurements with a precision better than 3.5 K above 200 K. THERMAP can acquire mid-infrared spectra (8-16 μm) of the surface with a spectral resolution Δλ of 0.3 μm. For surface temperatures above 350 K, spectra have a signal-to-noise ratio >60 in the spectral range 9-13 μm where most emission features occur. Title: Variegation of comet 67P/Churyumov-Gerasimenko in regions showing activity Authors: Oklay, N.; Vincent, J. -B.; Fornasier, S.; Pajola, M.; Besse, S.; Davidsson, B. J. R.; Lara, L. M.; Mottola, S.; Naletto, G.; Sierks, H.; Barucci, A. M.; Scholten, F.; Preusker, F.; Pommerol, A.; Masoumzadeh, N.; Lazzarin, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hall, I.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lin, Z. -Y.; Lopez Moreno, J. J.; Marzari, F.; Moreno, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C. Bibcode: 2016A&A...586A..80O Altcode: Aims.We carried out an investigation of the surface variegation of comet 67P/Churyumov-Gerasimenko, the detection of regions showing activity, the determination of active and inactive surface regions of the comet with spectral methods, and the detection of fallback material.
Methods: We analyzed multispectral data generated with Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) narrow angle camera (NAC) observations via spectral techniques, reflectance ratios, and spectral slopes in order to study active regions. We applied clustering analysis to the results of the reflectance ratios, and introduced the new technique of activity thresholds to detect areas potentially enriched in volatiles.
Results: Local color inhomogeneities are detected over the investigated surface regions. Active regions, such as Hapi, the active pits of Seth and Ma'at, the clustered and isolated bright features in Imhotep, the alcoves in Seth and Ma'at, and the large alcove in Anuket, have bluer spectra than the overall surface. The spectra generated with OSIRIS NAC observations are dominated by cometary emissions of around 700 nm to 750 nm as a result of the coma between the comet's surface and the camera. One of the two isolated bright features in the Imhotep region displays an absorption band of around 700 nm, which probably indicates the existence of hydrated silicates. An absorption band with a center between 800-900 nm is tentatively observed in some regions of the nucleus surface. This absorption band can be explained by the crystal field absorption of Fe2+, which is a common spectral feature seen in silicates. Title: First analysis of the size-frequency distribution of boulders ge 7m on comet 67P Authors: Pajola, M.; Vincent, J. B.; Güttler, C.; Lee, J. -C.; Massironi, M.; Bertini, I.; Simioni, E.; Marzari, F.; Giacomini, L.; Barbieri, C.; Cremonese, G.; Naletto, G.; Pommerol, A.; El Maarry, M. R.; Besse, S.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Thomas, N.; Auger, A. T.; Ip, W. -H.; Lin, Z. -Y.; Sierks, H.; OSIRIS Team; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Ferri, F.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hviid, S. F.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, J. -R.; Kürt, E.; Lamy, P.; Lara, L. M.; Lopez Moreno, J. J.; Magrin, S.; Michalik, H.; Moissl, R.; Mottola, S.; Oklay, N.; Preusker, F.; Rickman, H.; Rodrigo, R.; Scholten, F.; Tubiana, C. Bibcode: 2016MmSAI..87..156P Altcode: Images of the surface of comet 67P Churyumov-Gerasimenko taken by the OSIRIS camera on board the Rosetta spacecraft have been used to study the statistical distribution and morphological properties of both cluster and isolated roundish structures ('boulders') scattered all over the surface. We used NAC images taken on Aug 5-6, 2014, at a distance between 131.45 - 109.76 km, with a spatial resolution ranging from 2.44 - 2.03 m/px (Fig. 1). Such data cover a full rotation of 67P, providing the first ever full size frequency distribution coverage of boulders ≥ 7m visible on a cometary illuminated side. Boulders are ubiquitous on the head, neck, and body of 67P \citep{thomas15}. The initial count of 4,976 boulders was reduced to 3,546 for statistical purposes taking into consideration only those with a diameter larger than 7 m \citep{pajola15}. Title: Characterization of the Abydos region through OSIRIS high-resolution images in support of CIVA measurements Authors: Lucchetti, A.; Cremonese, G.; Jorda, L.; Poulet, F.; Bibring, J. -P.; Pajola, M.; La Forgia, F.; Massironi, M.; El-Maarry, M. R.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Preusker, F.; Scholten, F.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2016A&A...585L...1L Altcode: Context. On 12 November 2014, the European mission Rosetta delivered the Philae lander on the nucleus of comet 67P/Churyumov-Gerasimenko (67P). After the first touchdown, the lander bounced three times before finally landing at a site named Abydos.
Aims: We provide a morphologically detailed analysis of the Abydos landing site to support Philae's measurements and to give context for the interpretation of the images coming from the Comet Infrared and Visible Analyser (CIVA) camera system onboard the lander.
Methods: We used images acquired by the OSIRIS Narrow Angle Camera (NAC) on 6 December 2014 to perform the analysis of the Abydos landing site, which provided the geomorphological map, the gravitational slope map, the size-frequency distribution of the boulders. We also computed the albedo and spectral reddening maps.
Results: The morphological analysis of the region could suggest that Philae is located on a primordial terrain. The Abydos site is surrounded by two layered and fractured outcrops and presents a 0.02 km2 talus deposit rich in boulders. The boulder size frequency distribution gives a cumulative power-law index of -4.0 + 0.3/-0.4, which is correlated with gravitational events triggered by sublimation and/or thermal fracturing causing regressive erosion. The average value of the albedo is 5.8% at λ1 = 480.7 nm and 7.4% at λ2 = 649.2 nm, which is similar to the global albedos derived by OSIRIS and CIVA, respectively. Title: Sample of high-priority science objectives for future interplanetary missions towards asteroids Authors: Vernazza, Pierre; Beck, Pierre; Lamy, Philippe; Guilbert-Lepoutre, Aurelie Bibcode: 2016RoAJ...26...35V Altcode: In this paper, we present a sample of high-priority science objectives for future interplanetary missions towards asteroids that were submitted to ESA as a white paper in 2013 Title: Sunset jets observed on comet 67P/Churyumov-Gerasimenko sustained by subsurface thermal lag Authors: Shi, X.; Hu, X.; Sierks, H.; Güttler, C.; A'Hearn, M.; Blum, J.; El-Maarry, M. R.; Kührt, E.; Mottola, S.; Pajola, M.; Oklay, N.; Fornasier, S.; Tubiana, C.; Keller, H. U.; Vincent, J. -B.; Bodewits, D.; Höfner, S.; Lin, Z. -Y.; Gicquel, A.; Hofmann, M.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Thomas, N. Bibcode: 2016A&A...586A...7S Altcode: We present observations of sunset jets on comet 67P/Churyumov-Gerasimenko by Rosetta/OSIRIS camera. In late April 2015, when the comet was at a heliocentric distance of ~1.8 AU, clusters of dust jets that originated in the Ma'at region on the comet's small lobe were identified from multipleimages and were apparently sustained for about an hour beyond local sunset. Emanating from the shadowed nucleus, these jets became visible by solar illumination at their apparent sources up to only a few tens of meters above the nucleus surface. We investigate the plausibility of these jets as having been triggered by water ice sublimation and sustained by thermal lag in the subsurface beyond sunset. A general thermo-physical model was parameterized such that the thermal lag in the subsurface is consistent with the elapsed time of observation after sunset. It is found that the sublimation of water ice from a depth of 6 mm and with a low thermal inertia of 50 W m-2 K-1 s1/2 could explain the spatial pattern and evolution of the apparent sources, particularly their disappearance due to the eventual cooling of the subsurface. Our analysis suggests that these sunset jets were essentially day-side dust activities that continued after sunset. Specific observational conditions for the sunset jets constrain their possible sources to mostly within the less abrupt, dusty terrains. The uneven distribution of these jets is possibly related to subsurface inhomogeneities in the dusty area. Title: Coma dust environment observed by GIADA during the Perihelion of 67P/Churyumov-Gerasimenko. Authors: Rotundi, A.; Della Corte, V.; Fulle, M.; Ferrari, M.; Ivanovski, S. L.; Sordini, R.; Mazzotta Epifani, E.; Palumbo, P.; Colangeli, L.; Lopez-Moreno, J. J.; Rodriguez, J.; Zakharov, V.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S.; Gruen, E.; Lamy, P. L.; McDonnell, T.; Mennella, V.; Molina, A.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rodrigo, R.; Weissman, P. R.; Zarnecki, J.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M.; Jeronimo, J. M.; Leese, M.; Lopez-Jimenez, A.; Morales, R. Bibcode: 2015AGUFM.P33E..05R Altcode: GIADA (Grain Impact Analyzer and Dust Accumulator) is an in-situ instrument mounted onboard Rosetta monitoring the dust environment of comet 67P/Churyumov-Gerasimenko. GIADA is composed of 3 sub-systems: 1) the Grain Detection System, based on particle detection through light scattering; 2) the Impact Sensor, giving momentum measurement; 3) the Micro-Balances System, constituted of 5 quartz crystal microbalances, giving cumulative deposited dust. The combination of the measurements performed by these 3 subsystems provides: the number, the mass, the momentum and the speed distribution of dust particles emitted from the comet nucleus. We will present the coma dust environment as observed by GIADA during the perihelion phase of the Rosetta space mission. Despite the large distance from the nucleus, more than 200 km, GIADA was able to detect temporal and spatial variation of dust density distribution. Specific high dust spatial density sectors of the coma have been identified and their evolution during the perihelion phase was studied. Acknowledgements. GIADA was built by a consortium led by the Univ. Napoli "Parthenope" & INAF- Oss. Astr. Capodimonte, IT, in collaboration with the Inst. de Astrofisica de Andalucia, ES, Selex-ES s.p.a. and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with a support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developped from a PI proposal supported by the University of Kent; sci. & tech. contribution given by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their outstanding work. Science support provided by NASA through the US Rosetta Project managed by JPL/California Institute of Technology. GIADA calibrated data will be available through the ESA's PSA web site. Title: Morphology of the nucleus of Comet 67P/Churyumov--Gerasimenko from stereo and high spatial resolution OSIRIS-NAC images Authors: Lamy, P. L.; Groussin, O.; Romeuf, D.; Auger, A. T.; Jorda, L.; Capanna, C.; Faury, G. Bibcode: 2015AGUFM.P31E2113L Altcode: The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's Rosetta spacecraft has acquired images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at scales down to 0.2 m/pixel. We employ a variety of techniques to characterize its morphology. Digital terrain modeling (DTM), indispensable for quantitative morphological analysis is performed using stereophotoclinometry (SPC). Depending upon the observational coverage, the resolution of the DTMs exceeds 1 m in the most favorable cases. The ultimate stereographic analysis is performed by exploiting pairs of images able to produce anaglyphs whose spatial resolution surpasses that of the DTMs. Digital image filtering and contrast enhancement techniques are applied on the original images as appropriate. We first concentrate on the dust covered terrains possibly resulting from airfall deposits, on the quasi circular depressions or basins possibly connected to collapses of the underground terrain, and on large scarps that suggest extensive mass disruption. We pay special attention to lithologies that may give clues to the subsurface structure of the nucleus. Our ultimate goal is to understand the processes at work on the nucleus, directly or indirectly connected to its activity as there appears to a variety of processes far beyond what was classically considered in the past, for instance airfall deposits, surface dust transport, mass wasting, and insolation weathering. Title: The Subsurface Structure and Density of Cometary Nuclei Authors: Lamy, P. L.; Herique, A.; Toth, I. Bibcode: 2015SSRv..197...85L Altcode: 2015SSRv..tmp...33L Little is known about the internal structure and density of cometary nuclei. Indirect evidences available so far are not compelling and these questions essentially remain a matter of speculation. It is therefore important to fully exploit the potential sources of information and this is particularly the case of radar observations which have the capability to probe the first few meters of cometary nuclei when they come sufficiently close to Earth. We review the available results and find that proper data are available for eight nuclei yielding their geometric radar albedo and the dielectric permittivity of their subsurface assuming that the scattering of the radar beam is predominantly specular. The range of permittivity is quite broad, extending from 1.7 to 3.1 although a more realistic interval is probably 2 to 3.1 implying pronounced diversity in the subsurface properties of cometary nuclei. A novel interpretation of these results is performed based on the calculation of the dielectric permittivity of various samples of three-phase mixtures of ice, dust and vacuum using two mixing formulas and on the introduction of ternary diagrams where the three axes correspond to the volumetric fraction of the three phases. The derived values of the permittivity supplemented by a general constraint on the dust-to-ice mass ratio define restricted regions in the ternary diagrams broadly imposing that the ice fraction lies in the range 0.1 to 0.2, the dust fraction in the range 0.2 to 0.5, and the porosity in the range 35 % to 75 %. The density of the subsurface of the considered eight nuclei is only constrained to the broad range 500 to 2000 kg m-3 due to the poorly known density of the dust phase. However, the results unambiguously reveal considerable variation among cometary nuclei of the structure and properties of their subsurface layers. Title: The Activity of Comet 67P/Churyumov-Gerasimenko as Seen by Rosetta/OSIRIS Authors: Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Rickman, H.; Koschny, D. Bibcode: 2015AGUFM.P33E..02S Altcode: The Rosetta mission of the European Space Agency arrived on August 6, 2014, at the target comet 67P/Churyumov-Gerasimenko. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. OSIRIS consists of a Narrow Angle Camera (NAC) for the nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field gas and dust coma investigations. OSIRIS observed the coma and the nucleus of comet 67P/C-G during approach, arrival, and landing of PHILAE. OSIRIS continued comet monitoring and mapping of surface and activity in 2015 with close fly-bys with high resolution and remote, wide angle observations. The scientific results reveal a nucleus with two lobes and varied morphology. Active regions are located at steep cliffs and collapsed pits which form collimated gas jets. Dust is accelerated by the gas, forming bright jet filaments and the large scale, diffuse coma of the comet. We will present activity and surface changes observed in the Northern and Southern hemisphere and around perihelion passage. Title: Subsurface characterization of 67P/Churyumov-Gerasimenko's Abydos Site Authors: Brugger, B.; Mousis, O.; Morse, A.; Marboeuf, U.; Jorda, L.; Guilbert-Lepoutre, A.; Andrews, D.; Barber, S.; Lamy, P.; Luspay-Kuti, A.; Mandt, K.; Morgan, G.; Sheridan, S.; Vernazza, P.; Wright, I. P. Bibcode: 2015sf2a.conf...53B Altcode: We investigate the subsurface structure of comet 67P/Churyumov-Gerasimenko at the landing site of Rosetta's descent module Philae. We use a cometary nucleus model with an optimized parametrization and assume an initial composition derived from Rosetta/ROSINA measurements. We compare the CO and CO_2 outgassing rates derived from our model with those measured in situ by the Ptolemy experiment aboard the Philae module on November 12, 2014. We find results that allow us to place two main constraints on the subsurface structure of this region: a low CO/CO_2 molar ratio is needed in the nucleus, and the dust/ice mass ratio is higher at Abydos than in the rest of the nucleus. These specific constraints on Abydos support the statement of an important heterogeneity in 67P/Churyumov-Gerasimenko's nucleus. Title: The primordial nucleus of Comet 67P/Churyumov-Gerasimenko Authors: Davidsson, Bjorn; Sierks, Holger; Guettler, Carsten; Marzari, Francesco; Pajola, Maurizio; Rickman, Hans; A'Hearn, Michael; Auger, Anne-Therese; El-Maarry, Mohamed; Fornasier, Sonia; Gutierrez, Pedro; Keller, Horst Uwe; Massironi, Matteo; Snodgrass, Colin; Vincent, Jean-Baptiste; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Barucci, Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Cremonese, Gabriele; Da Deppo, Vania; Debei, Stefano; De Cecco, Mariolino; Feller, Clement; Fulle, Marco; Groussin, Olivier; Hviid, Stubbe; Hoefner, Sebastian; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Joerg; Kovacs, Gabor; Kramm, Joerg-Rainer; Kuehrt, Ekkehard; Kueppers, Michael; La Forgia, Fiorangela; Lara, Luisa; Lazzarin, Monica; Lopez Moreno, Jose; Moissl-Fraund, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Thomas, Nicolas; Tubiana, Cecilia Bibcode: 2015DPS....4741315D Altcode: Observations of Comet 67P/Churyumov-Gerasimenko by Rosetta show that the nucleus is bi-lobed, extensively layered, has a low bulk density, a high dust-to-ice mass ratio (implying high porosity), and weak strength except for a thin sintered surface layer. The comet is rich in supervolatiles (CO, CO2, N2), may contain amorphous water ice, and displays little to no signs of aqueous alteration. Lack of phyllosilicates in Stardust samples from Comet 81P/Wild 2 provides further support that comet nuclei did not contain liquid water.These properties differ from those expected for 50-200 km diameter bodies in the primordial disk. We find that thermal processing due to Al-26, combined with collisional compaction, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles, containing little to no amorphous water ice, and that have experienced extensive aqueous alteration. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. We therefore conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles.We propose a concurrent comet and TNO formation scenario that is consistent with these observations. We argue that TNOs form due to streaming instabilities at sizes of about 50-400 km and that about 350 of these grow slowly in a low-mass primordial disk to the size of Triton, causing little viscous stirring during growth. We propose a dynamically cold primordial disk, that prevents medium-sized TNOs from breaking into collisional rubble piles, and allows for the survival of primordial rubble-pile comets. We argue that comets form by hierarchical agglomeration out of material that remains after TNO formation. This slow growth is necessary to avoid thermal processing by Al-26, and to allow comet nuclei to incorporate 3 Myr old material from the inner Solar System, found in Stardust samples. Growth in the Solar Nebula creates porous single-lobe nuclei, while continued growth in a mildly viscously stirred primordial disk creates denser outer layers, and allow bi-lobe nucleus formation through mergers. Title: Temporal morphological changes at the surface of comet 67P/Churyumov-Gerasimenko Authors: Groussin, Olivier; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U. Bibcode: 2015DPS....4750005G Altcode: A key scientific question, to understand how comets work and whether they still contain pristine materials at or near their surface, is to understand how the nucleus is changing with time and to which extent activity modifies its surface. Rosetta, which has been orbiting comet 67P/Churyumov-Gerasimenko since August 2014, offers a unique opportunity to tackle this fundamental question. Here, we report on temporal morphological changes detected on the surface of the nucleus of comet 67P by the OSIRIS cameras. Changes have been detected in several regions and in particular in the Imhotep region, where they are visible in the form of roundish features that are growing in size from a given location in a preferential direction. Terrains bluer than the surroundings appear during changes, suggesting the presence of (water) ice exposed on the surface. Title: Pits Formation from Volatile Outgassing on 67P/Churyumov-Gerasimenko Authors: Mousis, O.; Guilbert-Lepoutre, A.; Brugger, B.; Jorda, L.; Kargel, J. S.; Bouquet, A.; Auger, A. -T.; Lamy, P.; Vernazza, P.; Thomas, N.; Sierks, H. Bibcode: 2015ApJ...814L...5M Altcode: 2015arXiv151007671M We investigate the thermal evolution of comet 67P/Churyumov-Gerasimenko’s subsurface in the Seth_01 region, where active pits have been observed by the ESA/Rosetta mission. Our simulations show that clathrate destabilization and amorphous ice crystallization can occur at depths corresponding to those of the observed pits in a timescale shorter than 67P/Churyumov-Gerasimenko’s lifetime in the comet’s activity zone in the inner solar system. Sublimation of crystalline ice down to such depths is possible only in the absence of a dust mantle, which requires the presence of dust grains in the matrix small enough to be dragged out by gas from the pores. Our results are consistent with both pits formation via sinkholes or subsequent to outbursts, the dominant process depending on the status of the subsurface porosity. A sealed dust mantle would favor episodic and disruptive outgassing as a result of increasing gas pressure in the pores, while high porosity should allow the formation of large voids in the subsurface due to the continuous escape of volatiles. We finally conclude that the subsurface of 67P/Churyumov-Gerasimenko is not uniform at a spatial scale of ∼100-200 m. Title: Size-frequency distribution of boulders ≥7 m on comet 67P/Churyumov-Gerasimenko Authors: Pajola, Maurizio; Vincent, Jean-Baptiste; Güttler, Carsten; Lee, Jui-Chi; Bertini, Ivano; Massironi, Matteo; Simioni, Emanuele; Marzari, Francesco; Giacomini, Lorenza; Lucchetti, Alice; Barbieri, Cesare; Cremonese, Gabriele; Naletto, Giampiero; Pommerol, Antoine; El-Maarry, Mohamed R.; Besse, Sébastien; Küppers, Michael; La Forgia, Fiorangela; Lazzarin, Monica; Thomas, Nicholas; Auger, Anne-Thérèse; Sierks, Holger; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst U.; Agarwal, Jessica; A'Hearn, Michael F.; Barucci, Maria A.; Bertaux, Jean-Loup; Da Deppo, Vania; Davidsson, Björn; De Cecco, Mariolino; Debei, Stefano; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Groussin, Olivier; Gutierrez, Pedro J.; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kramm, J. -Rainer; Kürt, Ekkehard; Lara, Luisa M.; Lin, Zhong-Yi; Lopez Moreno, Jose J.; Magrin, Sara; Marchi, Simone; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Oklay, Nilda; Preusker, Frank; Scholten, Frank; Tubiana, Cecilia Bibcode: 2015A&A...583A..37P Altcode:
Aims: We derive for the first time the size-frequency distribution of boulders on a comet, 67P/Churyumov-Gerasimenko (67P), computed from the images taken by the Rosetta/OSIRIS imaging system. We highlight the possible physical processes that lead to these boulder size distributions.
Methods: We used images acquired by the OSIRIS Narrow Angle Camera, NAC, on 5 and 6 August 2014. The scale of these images (2.44-2.03 m/px) is such that boulders ≥7 m can be identified and manually extracted from the datasets with the software ArcGIS. We derived both global and localized size-frequency distributions. The three-pixel sampling detection, coupled with the favorable shadowing of the surface (observation phase angle ranging from 48° to 53°), enables unequivocally detecting boulders scattered all over the illuminated side of 67P.
Results: We identify 3546 boulders larger than 7 m on the imaged surface (36.4 km2), with a global number density of nearly 100/km2 and a cumulative size-frequency distribution represented by a power-law with index of -3.6 +0.2/-0.3. The two lobes of 67P appear to have slightly different distributions, with an index of -3.5 +0.2/-0.3 for the main lobe (body) and -4.0 +0.3/-0.2 for the small lobe (head). The steeper distribution of the small lobe might be due to a more pervasive fracturing. The difference of the distribution for the connecting region (neck) is much more significant, with an index value of -2.2 +0.2/-0.2. We propose that the boulder field located in the neck area is the result of blocks falling from the contiguous Hathor cliff. The lower slope of the size-frequency distribution we see today in the neck area might be due to the concurrent processes acting on the smallest boulders, such as i) disintegration or fragmentation and vanishing through sublimation; ii) uplifting by gas drag and consequent redistribution; and iii) burial beneath a debris blanket. We also derived the cumulative size-frequency distribution per km2 of localized areas on 67P. By comparing the cumulative size-frequency distributions of similar geomorphological settings, we derived similar power-law index values. This suggests that despite the selected locations on different and often opposite sides of the comet, similar sublimation or activity processes, pit formation or collapses, as well as thermal stresses or fracturing events occurred on multiple areas of the comet, shaping its surface into the appearance we see today. Title: Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images Authors: El-Maarry, M. R.; Thomas, N.; Giacomini, L.; Massironi, M.; Pajola, M.; Marschall, R.; Gracia-Berná, A.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Rickman, H.; Koschny, D.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Güttler, C.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..26E Altcode:
Aims: The OSIRIS camera onboard the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)'s nucleus at spatial resolutions down to ~0.17 m/px ever since Aug. 2014. These images have yielded unprecedented insight into the morphological diversity of the comet's surface. This paper presents an overview of the regional morphology of comet 67P.
Methods: We used the images that were acquired at orbits ~20-30 km from the center of the comet to distinguish different regions on the surface and introduce the basic regional nomenclature adopted by all papers in this Rosetta special feature that address the comet's morphology and surface processes. We used anaglyphs to detect subtle regional and topographical boundaries and images from close orbit (~10 km from the comet's center) to investigate the fine texture of the surface.
Results: Nineteen regions have currently been defined on the nucleus based on morphological and/or structural boundaries, and they can be grouped into distinctive region types. Consolidated, fractured regions are the most common region type. Some of these regions enclose smooth units that appear to settle in gravitational sinks or topographically low areas. Both comet lobes have a significant portion of their surface covered by a dusty coating that appears to be recently placed and shows signs of mobilization by aeolian-like processes. The dusty coatings cover most of the regions on the surface but are notably absent from a couple of irregular large depressions that show sharp contacts with their surroundings and talus-like deposits in their interiors, which suggests that short-term explosive activity may play a significant role in shaping the comet's surface in addition to long-term sublimation loss. Finally, the presence of layered brittle units showing signs of mechanical failure predominantly in one of the comet's lobes can indicate a compositional heterogeneity between the two lobes.

Tables 2 and 3 and Appendix A are available in electronic form at http://www.aanda.org Title: Orbital elements of the material surrounding comet 67P/Churyumov-Gerasimenko Authors: Davidsson, B. J. R.; Gutiérrez, P. J.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Lowry, S.; Magrin, S.; Marzari, F.; Michalik, H.; Moissl-Fraund, R.; Naletto, G.; Oklay, N.; Pajola, M.; Snodgrass, C.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..16D Altcode: Context. We investigate the dust coma within the Hill sphere of comet 67P/Churyumov-Gerasimenko.
Aims: We aim to determine osculating orbital elements for individual distinguishable but unresolved slow-moving grains in the vicinity of the nucleus. In addition, we perform photometry and constrain grain sizes.
Methods: We performed astrometry and photometry using images acquired by the OSIRIS Wide Angle Camera on the European Space Agency spacecraft Rosetta. Based on these measurements, we employed standard orbit determination and orbit improvement techniques.
Results: Orbital elements and effective diameters of four grains were constrained, but we were unable to uniquely determine them. Two of the grains have light curves that indicate grain rotation.
Conclusions: The four grains have diameters nominally in the range 0.14-0.50 m. For three of the grains, we found elliptic orbits, which is consistent with a cloud of bound particles around the nucleus. However, hyperbolic escape trajectories cannot be excluded for any of the grains, and for one grain this is the only known option. One grain may have originated from the surface shortly before observation. These results have possible implications for the understanding of the dispersal of the cloud of bound debris around comet nuclei, as well as for understanding the ejection of large grains far from the Sun. Title: Geomorphology of the Imhotep region on comet 67P/Churyumov-Gerasimenko from OSIRIS observations Authors: Auger, A. -T.; Groussin, O.; Jorda, L.; Bouley, S.; Gaskell, R.; Lamy, P. L.; Capanna, C.; Thomas, N.; Pommerol, A.; Sierks, H.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Massironi, M.; Michalik, H.; Naletto, G.; Oklay, N.; Pajola, M.; Sabau, L.; Tubiana, C.; Vincent, J. -B.; Wenzel, K. -P. Bibcode: 2015A&A...583A..35A Altcode: Context. Since August 2014, the OSIRIS Narrow Angle Camera (NAC) onboard the Rosetta spacecraft has acquired high spatial resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko, down to the decimeter scale. This paper focuses on the Imhotep region, located on the largest lobe of the nucleus, near the equator.
Aims: We map, inventory, and describe the geomorphology of the Imhotep region. We propose and discuss some processes to explain the formation and ongoing evolution of this region.
Methods: We used OSIRIS NAC images, gravitational heights and slopes, and digital terrain models to map and measure the morphologies of Imhotep.
Results: The Imhotep region presents a wide variety of terrains and morphologies: smooth and rocky terrains, bright areas, linear features, roundish features, and boulders. Gravity processes such as mass wasting and collapse play a significant role in the geomorphological evolution of this region. Cometary processes initiate erosion and are responsible for the formation of degassing conduits that are revealed by elevated roundish features on the surface. We also propose a scenario for the formation and evolution of the Imhotep region; this implies the presence of large primordial voids inside the nucleus, resulting from its formation process. Title: Geomorphology and spectrophotometry of Philae's landing site on comet 67P/Churyumov-Gerasimenko Authors: La Forgia, F.; Giacomini, L.; Lazzarin, M.; Massironi, M.; Oklay, N.; Scholten, F.; Pajola, M.; Bertini, I.; Cremonese, G.; Barbieri, C.; Naletto, G.; Simioni, E.; Preusker, F.; Thomas, N.; Sierks, H.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Auger, A. -T.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Besse, S.; Bodewits, D.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Ferri, F.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hall, I.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. -M.; Lopez Moreno, J. J.; Magrin, S.; Marzari, F.; Michalik, H.; Mottola, S.; Pommerol, A.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..41L Altcode: Context. On 12 November 2014 the European mission Rosetta succeeded in delivering a lander, named Philae, on the surface of one of the smallest, low-gravity and most primitive bodies of the solar system, the comet 67P/Churyumov-Gerasimenko (67P).
Aims: The aim of this paper is to provide a comprehensive geomorphological and spectrophotometric analysis of Philae's landing site (Agilkia) to give an essential framework for the interpretation of its in situ measurements.
Methods: OSIRIS images, coupled with gravitational slopes derived from the 3D shape model based on stereo-photogrammetry were used to interpret the geomorphology of the site. We adopted the Hapke model, using previously derived parameters, to photometrically correct the images in orange filter (649.2 nm). The best approximation to the Hapke model, given by the Akimov parameter-less function, was used to correct the reflectance for the effects of viewing and illumination conditions in the other filters. Spectral analyses on coregistered color cubes were used to retrieve spectrophotometric properties.
Results: The landing site shows an average normal albedo of 6.7% in the orange filter with variations of ~15% and a global featureless spectrum with an average red spectral slope of 15.2%/100 nm between 480.7 nm (blue filter) and 882.1 nm (near-IR filter). The spatial analysis shows a well-established correlation between the geomorphological units and the photometric characteristics of the surface. In particular, smooth deposits have the highest reflectance a bluer spectrum than the outcropping material across the area.
Conclusions: The featureless spectrum and the redness of the material are compatible with the results by other instruments that have suggested an organic composition. The observed small spectral variegation could be due to grain size effects. However, the combination of photometric and spectral variegation suggests that a compositional differentiation is more likely. This might be tentatively interpreted as the effect of the efficient dust-transport processes acting on 67P. High-activity regions might be the original sources for smooth fine-grained materials that then covered Agilkia as a consequence of airfall of residual material. More observations performed by OSIRIS as the comet approaches the Sun would help interpreting the processes that work at shaping the landing site and the overall nucleus. Title: Shape model, reference system definition, and cartographic mapping standards for comet 67P/Churyumov-Gerasimenko - Stereo-photogrammetric analysis of Rosetta/OSIRIS image data Authors: Preusker, F.; Scholten, F.; Matz, K. -D.; Roatsch, T.; Willner, K.; Hviid, S. F.; Knollenberg, J.; Jorda, L.; Gutiérrez, P. J.; Kührt, E.; Mottola, S.; A'Hearn, M. F.; Thomas, N.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Güttler, C.; Ip, W. -H.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Oklay, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..33P Altcode: We analyzed more than 200 OSIRIS NAC images with a pixel scale of 0.9-2.4 m/pixel of comet 67P/Churyumov-Gerasimenko (67P) that have been acquired from onboard the Rosetta spacecraft in August and September 2014 using stereo-photogrammetric methods (SPG). We derived improved spacecraft position and pointing data for the OSIRIS images and a high-resolution shape model that consists of about 16 million facets (2 m horizontal sampling) and a typical vertical accuracy at the decimeter scale. From this model, we derive a volume for the northern hemisphere of 9.35 km3 ± 0.1 km3. With the assumption of a homogeneous density distribution and taking into account the current uncertainty of the position of the comet's center-of-mass, we extrapolated this value to an overall volume of18.7 km3± 1.2 km3, and, with a current best estimate of 1.0 × 1013 kg for the mass, we derive a bulk density of 535 kg/m3± 35 kg/m3. Furthermore, we used SPG methods to analyze the rotational elements of 67P. The rotational period for August and September 2014 was determined to be 12.4041 ± 0.0004 h. For the orientation of the rotational axis (z-axis of the body-fixed reference frame) we derived a precession model with a half-cone angle of 0.14°, a cone center position at 69.54°/64.11° (RA/Dec J2000 equatorial coordinates), and a precession period of 10.7 days. For the definition of zero longitude (x-axis orientation), we finally selected the boulder-like Cheops feature on the big lobe of 67P and fixed its spherical coordinates to 142.35° right-hand-rule eastern longitude and -0.28° latitude. This completes the definition of the new Cheops reference frame for 67P. Finally, we defined cartographic mapping standards for common use and combined analyses of scientific results that have been obtained not only within the OSIRIS team, but also within other groups of the Rosetta mission.

Appendices are available in electronic form at http://www.aanda.org Title: Insolation, erosion, and morphology of comet 67P/Churyumov-Gerasimenko Authors: Keller, H. U.; Mottola, S.; Davidsson, B.; Schröder, S. E.; Skorov, Y.; Kührt, E.; Groussin, O.; Pajola, M.; Hviid, S. F.; Preusker, F.; Scholten, F.; A'Hearn, M. F.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Sabau, L.; Thomas, N.; Vincent, J. -B.; Wenzel, K. -P.; Agarwal, J.; Güttler, C.; Oklay, N.; Tubiana, C. Bibcode: 2015A&A...583A..34K Altcode: Context. The complex shape of comet 67P and its oblique rotation axis cause pronounced seasonal effects. Irradiation and hence activity vary strongly.
Aims: We investigate the insolation of the cometary surface in order to predict the sublimation of water ice. The strongly varying erosion levels are correlated with the topography and morphology of the present cometary surface and its evolution.
Methods: The insolation as a function of heliocentric distance and diurnal (spin dependent) variation is calculated using >105 facets of a detailed digital terrain model. Shading, but also illumination and thermal radiation by facets in the field of view of a specific facet are iteratively taken into account. We use a two-layer model of a thin porous dust cover above an icy surface to calculate the water sublimation, presuming steady state and a uniform surface. Our second model, which includes the history of warming and cooling due to thermal inertia, is restricted to a much simpler shape model but allows us to test various distributions of active areas.
Results: Sublimation from a dirty ice surface yields maximum erosion. A thin dust cover of 50 μm yields similar rates at perihelion. Only about 6% of the surface needs to be active to match the observed water production rates at perihelion. A dust layer of 1 mm thickness suppresses the activity by a factor of 4 to 5. Erosion on the south side can reach more than 10 m per orbit at active spots. The energy input to the concave neck area (Hapi) during northern summer is enhanced by about 50% owing to self-illumination. Here surface temperatures reach maximum values along the foot of the Hathor wall. Integrated over the whole orbit this area receives the least energy input. Based on the detailed shape model, the simulations identify "hot spots" in depressions and larger pits in good correlation with observed dust activity. Three-quarters of the total sublimation is produced while the sub-solar latitude is south, resulting in a distinct dichotomy in activity and morphology.
Conclusions: The northern areas display a much rougher morphology than what is seen on Imhotep, an area at the equator that will be fully illuminated when 67P is closer to the Sun. Self-illumination in concave regions enhance the energy input and hence erosion. This explains the early activity observed at Hapi. Cliffs are more prone to erosion than horizontal, often dust covered, areas, which leads to surface planation. Local activity can only persist if the forming cliff walls are eroding. Comet 67P has two lobes and also two distinct sides. Transport of material from the south to the north is probable. The morphology of the Imhotep plain should be typical for the terrains of the yet unseen southern hemisphere. Title: Morphology and dynamics of the jets of comet 67P/Churyumov-Gerasimenko: Early-phase development Authors: Lin, Z. -Y.; Ip, W. -H.; Lai, I. -L.; Lee, J. -C.; Vincent, J. -B.; Lara, L. M.; Bodewits, D.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.; López-Moreno, J. J.; Lowry, S.; Marzari, F.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Rożek, A.; Thomas, N.; Liao, Y.; Tubiana, C. Bibcode: 2015A&A...583A..11L Altcode:
Aims: The OSIRIS camera onboard the Rosetta spacecraft obtained close-up views of the dust coma of comet 67P. The jet structures can be used to trace their source regions and to examine the possible effect of gas-surface interaction.
Methods: We analyzed the wide-angle images obtained in the special dust observation sequences between August and September 2014. The jet features detected in different images were compared to study their time variability. The locations of the potential source regions of some of the jets are identified by ray tracing. We used a ring-masking technique to calculate the brightness distribution of dust jets along the projected distance.
Results: The jets detected between August and September 2014 mostly originated in the Hapi region. Morphological changes appeared over a timescale of several days in September. The brightness slope of the dust jets is much steeper than the background coma. This might be related to the sublimation or fragmentation of the emitted dust grains. Interaction of the expanding gas flow with the cliff walls on both sides of Hapi could lead to erosion and material down-fall to the nucleus surface.

Appendix A is available in electronic form at http://www.aanda.org Title: Redistribution of particles across the nucleus of comet 67P/Churyumov-Gerasimenko Authors: Thomas, N.; Davidsson, B.; El-Maarry, M. R.; Fornasier, S.; Giacomini, L.; Gracia-Berná, A. G.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kührt, E.; La Forgia, F.; Lai, I. L.; Liao, Y.; Marschall, R.; Massironi, M.; Mottola, S.; Pajola, M.; Poch, O.; Pommerol, A.; Preusker, F.; Scholten, F.; Su, C. C.; Wu, J. S.; Vincent, J. -B.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; de Cecco, M.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Kramm, J. -R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Agarwal, J.; Güttler, C.; Oklay, N.; Tubiana, C. Bibcode: 2015A&A...583A..17T Altcode: Context. We present an investigation of the surface properties of areas on the nucleus of comet 67P/Churyumov-Gerasimenko.
Aims: We aim to show that transport of material from one part of the cometary nucleus to another is a significant mechanism that influences the appearance of the nucleus and the surface thermal properties.
Methods: We used data from the OSIRIS imaging system onboard the Rosetta spacecraft to identify surface features on the nucleus that can be produced by various transport mechanisms. We used simple calculations based on previous works to establish the plausibility of dust transport from one part of the nucleus to another.
Results: We show by observation and modeling that "airfall" as a consequence of non-escaping large particles emitted from the neck region of the nucleus is a plausible explanation for the smooth thin deposits in the northern hemisphere of the nucleus. The consequences are also discussed. We also present observations of aeolian ripples and ventifacts. We show by numerical modeling that a type of saltation is plausible even under the rarified gas densities seen at the surface of the nucleus. However, interparticle cohesive forces present difficulties for this model, and an alternative mechanism for the initiation of reptation and creep may result from the airfall mechanism. The requirements on gas density and other parameters of this alternative make it a more attractive explanation for the observations. The uncertainties and implications are discussed. Title: Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations Authors: Rickman, H.; Marchi, S.; A'Hearn, M. F.; Barbieri, C.; El-Maarry, M. R.; Güttler, C.; Ip, W. -H.; Keller, H. U.; Lamy, P.; Marzari, F.; Massironi, M.; Naletto, G.; Pajola, M.; Sierks, H.; Koschny, D.; Rodrigo, R.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Michalik, H.; Sabau, L.; Thomas, N.; Vincent, J. -B.; Wenzel, K. -P. Bibcode: 2015A&A...583A..44R Altcode: 2015arXiv150507021R Context. One of the main aims of the ESA Rosetta mission is to study the origin of the solar system by exploring comet 67P/Churyumov-Gerasimenko at close range.
Aims: In this paper we discuss the origin and evolution of comet 67P/Churyumov-Gerasimenko in relation to that of comets in general and in the framework of current solar system formation models.
Methods: We use data from the OSIRIS scientific cameras as basic constraints. In particular, we discuss the overall bi-lobate shape and the presence of key geological features, such as layers and fractures. We also treat the problem of collisional evolution of comet nuclei by a particle-in-a-box calculation for an estimate of the probability of survival for 67P/Churyumov-Gerasimenko during the early epochs of the solar system.
Results: We argue that the two lobes of the 67P/Churyumov-Gerasimenko nucleus are derived from two distinct objects that have formed a contact binary via a gentle merger. The lobes are separate bodies, though sufficiently similar to have formed in the same environment. An estimate of the collisional rate in the primordial, trans-planetary disk shows that most comets of similar size to 67P/Churyumov-Gerasimenko are likely collisional fragments, although survival of primordial planetesimals cannot be excluded.
Conclusions: A collisional origin of the contact binary is suggested, and the low bulk density of the aggregate and abundance of volatile species show that a very gentle merger must have occurred. We thus consider two main scenarios: the primordial accretion of planetesimals, and the re-accretion of fragments after an energetic impact onto a larger parent body. We point to the primordial signatures exhibited by 67P/Churyumov-Gerasimenko and other comet nuclei as critical tests of the collisional evolution. Title: Large-scale dust jets in the coma of 67P/Churyumov-Gerasimenko as seen by the OSIRIS instrument onboard Rosetta Authors: Lara, L. M.; Lowry, S.; Vincent, J. -B.; Gutiérrez, P. J.; Rożek, A.; La Forgia, F.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Auger, A. -T.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Davidsson, B.; Da Deppo, V.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Ferri, F.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez-Marques, P.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lazzarin, M.; Lin, Z. -Y.; López-Moreno, J. J.; Magrin, S.; Marzari, F.; Michalik, H.; Moissl-Fraund, R.; Moreno, F.; Mottola, S.; Naletto, G.; Pajola, M.; Pommerol, A.; Thomas, N.; Sabau, M. D.; Tubiana, C. Bibcode: 2015A&A...583A...9L Altcode: Context. During the most recent perihelion passage in 2009 of comet 67P/Churyumov-Gerasimenko (67P), ground-based observations showed an anisotropic dust coma where jet-like features were detected at ~ 1.3 AU from the Sun. The current perihelion passage is exceptional as the Rosetta spacecraft is monitoring the nucleus activity since March 2014, when a clear dust coma was already surrounding the nucleus at 4.3 AU from the Sun. Subsequently, the OSIRIS camera also witnessed an outburst in activity between April 27 and 30, and since mid-July, the dust coma at rh ~ 3.7-3.6 AU preperihelion is clearly non-isotropic, pointing to the existence of dust jet-like features.
Aims: We aim to ascertain on the nucleus surface the origin of the dust jet-like features detected as early as in mid-July 2014. This will help to establish how the localized comet nucleus activity compares with that seen in previous apparitions and will also help following its evolution as the comet approaches its perihelion, at which phase most of the jets were detected from ground-based observations. Determining these areas also allows locating them in regions on the nucleus with spectroscopic or geomorphological distinct characteristics.
Methods: Three series of dust images of comet 67P obtained with the Wide Angle Camera (WAC) of the OSIRIS instrument onboard the Rosetta spacecraft were processed with different enhancement techniques. This was made to clearly show the existence of jet-like features in the dust coma, whose appearance toward the observer changed as a result of the rotation of the comet nucleus and of the changing observing geometry from the spacecraft. The position angles of these features in the coma together with information on the observing geometry, nucleus shape, and rotation, allowed us to determine the most likely locations on the nucleus surface where the jets originate from.
Results: Geometrical tracing of jet sources indicates that the activity of the nucleus of 67P gave rise during July and August 2014 to large-scale jet-like features from the Hapi, Hathor, Anuket, and Aten regions, confirming that active regions may be present on the nucleus localized at 60° northern latitude as deduced from previous comet apparitions. There are also hints that large-scale jets observed from the ground are possibly composed, at their place of origin on the nucleus surface, of numerous small-scale features. Title: Search for satellites near comet 67P/Churyumov-Gerasimenko using Rosetta/OSIRIS images Authors: Bertini, I.; Gutiérrez, P. J.; Lara, L. M.; Marzari, F.; Moreno, F.; Pajola, M.; La Forgia, F.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Ferri, F.; Fornasier, S.; Fulle, M.; Giacomini, L.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lazzarin, M.; Lopez Moreno, J. J.; Magrin, S.; Massironi, M.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay, N.; Thomas, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..19B Altcode: Context. TheEuropean Space Agency Rosetta mission reached and started escorting its main target, the Jupiter-family comet 67P/Churyumov-Gerasimenko, at the beginning of August 2014. Within the context of solar system small bodies, satellite searches from approaching spacecraft were extensively used in the past to study the nature of the visited bodies and their collisional environment.
Aims: During the approaching phase to the comet in July 2014, the OSIRIS instrument onboard Rosetta performed a campaign aimed at detecting objects in the vicinity of the comet nucleus and at measuring these objects' possible bound orbits. In addition to the scientific purpose, the search also focused on spacecraft security to avoid hazardous material in the comet's environment.
Methods: Images in the red spectral domain were acquired with the OSIRIS Narrow Angle Camera, when the spacecraft was at a distance between 5785 km and 5463 km to the comet, following an observational strategy tailored to maximize the scientific outcome. From the acquired images, sources were extracted and displayed to search for plausible displacements of all sources from image to image. After stars were identified, the remaining sources were thoroughly analyzed. To place constraints on the expected displacements of a potential satellite, we performed Monte Carlo simulations on the apparent motion of potential satellites within the Hill sphere.
Results: We found no unambiguous detections of objects larger than ~6 m within ~20 km and larger than ~1 m between ~20 km and ~110 km from the nucleus, using images with an exposure time of 0.14 s and 1.36 s, respectively. Our conclusions are consistent with independent works on dust grains in the comet coma and on boulders counting on the nucleus surface. Moreover, our analysis shows that the comet outburst detected at the end of April 2014 was not strong enough to eject large objects and to place them into a stable orbit around the nucleus. Our findings underline that it is highly unlikely that large objects survive for a long time around cometary nuclei. Title: Rotating dust particles in the coma of comet 67P/Churyumov-Gerasimenko Authors: Fulle, M.; Ivanovski, S. L.; Bertini, I.; Gutierrez, P.; Lara, L.; Sierks, H.; Zakharov, V.; Della Corte, V.; Rotundi, A.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip, W.; Jorda, L.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Oklay, N.; Sabau, L.; Thomas, N.; Tubiana, C.; Vincent, J. -B.; Wenzel, K. -P. Bibcode: 2015A&A...583A..14F Altcode: Context. During September and October 2014, the OSIRIS cameras onboard the ESA Rosetta mission detected millions of single particles. Many of these dust particlesappear as long tracks (due to both the dust proper motion and the spacecraft motion during the exposure time) with a clear brightness periodicity.
Aims: We interpret the observed periodic features as a rotational and translational motion of aspherical dust grains.
Methods: By counting the peaks of each track, we obtained statistics of a rotation frequency. We compared these results with the rotational frequency predicted by a model of aspherical dust grain dynamics in a model gas flow. By testing many possible sets of physical conditions and grain characteristics, we constrained the rotational properties of dust grains.
Results: We analyzed on the motion of rotating aspherical dust grains with different cross sections in flow conditions corresponding to the coma of 67P/Churyumov-Gerasimenko qualitatively and quantitatively. Based on the OSIRIS observations, we constrain the possible physical parameters of the grains. Title: Activity and jets of comet 67P, as observed by OSIRIS since August 2014 Authors: Vincent, Jean-Baptiste; Oklay, Nilda; Pajola, Maurizio; Höfner, Sebastian; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Rickman, Hans; Koschny, Detlef Bibcode: 2015DPS....4741307V Altcode: Dust jets, i.e. fuzzy collimated streams of cometary material arising from the nucleus, have been observed in-situ on all comets since the Giotto mission flew by comet 1P/Halley in 1986. Yet their formation mechanism remains unknown. Several solutions have been proposed, from localized physical mechanisms on the surface/sub-surface to purely dynamical processes involving the focusing of gas flows by the local topography. While the latter seems to be responsible forthe larger features, high resolution imagery has shown that broad streams are composed of many smaller features (a few meters wide) that connect directly to the nucleus surface.The OSIRIS cameras on board Rosetta are monitoring these jets in high resolution images since August 2014. We followed this type of activity from 3.6 AU to perihelion (1.23 AU). We have traced the jets back to their sources on the surface and noticed a good correlation with sub-solar latitude, surface morphologies, and color variations. As the comet receives more insolation, we observed different type of jets, some of them sustained beyond the local sunset, and an increasing number of transient events with sudden release of gas and dust.We will present here how activity changes with local seasons and how it contributes to the erosion of the surface.Acknowledgements: OSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de Marseille, France, the Instituto de Astrofi­sica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Tecnica Aeroespacial, Madrid, Spain, the Universidad Politechnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany. We thank the Rosetta Science Ground Segment at ESAC, the Rosetta Mission Operations Centre at ESOC and the Rosetta Project at ESTEC for their outstanding work enabling the science return of the Rosetta Mission. Title: Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko Authors: Groussin, O.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Auger, A. -T.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Hviid, S.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Lowry, S.; Marchi, S.; Marzari, F.; Massironi, M.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..36G Altcode: 2015arXiv150902794G
Aims: We report on the first major temporal morphological changes observed on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko in the smooth terrains of the Imhotep region.
Methods: We used images of the OSIRIS cameras onboard Rosetta to follow the temporal changes from 24 May 2015 to 11 July 2015.
Results: The morphological changes observed on the surface are visible in the form of roundish features that are growing in size from a given location in a preferential direction at a rate of 5.6-8.1 × 10-5 m s-1 during the observational period. The location where the changes started and the contours of the expanding features are bluer than the surroundings, which suggests that ices (H2O and/or CO2) are exposed on the surface. However, sublimation of ices alone is not sufficient to explain the observed expanding features. No significant variations in the dust activity pattern are observed during the period of changes. Title: GIADA: shining a light on the monitoring of the comet dust production from the nucleus of 67P/Churyumov-Gerasimenko Authors: Della Corte, V.; Rotundi, A.; Fulle, M.; Gruen, E.; Weissman, P.; Sordini, R.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Accolla, M.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S. F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rietmeijer, F. J. M.; Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A. C.; Altobelli, N. Bibcode: 2015A&A...583A..13D Altcode: Context. During the period between 15 September 2014 and 4 February 2015, the Rosetta spacecraft accomplished the circular orbit phase around the nucleus of comet 67P/Churyumov-Gerasimenko (67P). The Grain Impact Analyzer and Dust Accumulator (GIADA) onboard Rosetta monitored the 67P coma dust environment for the entire period.
Aims: We aim to describe the dust spatial distribution in the coma of comet 67P by means of in situ measurements. We determine dynamical and physical properties of cometary dust particles to support the study of the production process and dust environment modification.
Methods: We analyzed GIADA data with respect to the observation geometry and heliocentric distance to describe the coma dust spatial distribution of 67P, to monitor its activity, and to retrieve information on active areas present on its nucleus. We combined GIADA detection information with calibration activity to distinguish different types of particles that populate the coma of 67P: compact particles and fluffy porous aggregates. By means of particle dynamical parameters measured by GIADA, we studied the dust acceleration region.
Results: GIADA was able to distinguish different types of particles populating the coma of 67P: compact particles and fluffy porous aggregates. Most of the compact particle detections occurred at latitudes and longitudes where the spacecraft was in view of the comet's neck region of the nucleus, the so-called Hapi region. This resulted in an oscillation of the compact particle abundance with respect to the spacecraft position and a global increase as the comet moved from 3.36 to 2.43 AU heliocentric distance. The speed of these particles, having masses from 10-10 to 10-7 kg, ranged from 0.3 to 12.2 m s-1. The variation of particle mass and speed distribution with respect to the distance from the nucleus gave indications of the dust acceleration region. The influence of solar radiation pressure on micron and submicron particles was studied. The integrated dust mass flux collected from the Sun direction, that is, particles reflected by solar radiation pressure, was three times higher than the flux coming directly from the comet nucleus. The awakening 67P comet shows a strong dust flux anisotropy, confirming what was suggested by on-ground dust coma observations performed in 2008. Title: Scientific assessment of the quality of OSIRIS images Authors: Tubiana, C.; Güttler, C.; Kovacs, G.; Bertini, I.; Bodewits, D.; Fornasier, S.; Lara, L.; La Forgia, F.; Magrin, S.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. -L.; Besse, S.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fulle, M.; Groussin, O.; Gutiérrez-Marques, P.; Gutiérrez, P. J.; Hoekzema, N.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Michalik, H.; Moissl, R.; Naletto, G.; Oklay, N.; Scholten, F.; Shi, X.; Thomas, N.; Vincent, J. -B. Bibcode: 2015A&A...583A..46T Altcode: Context. OSIRIS, the scientific imaging system onboard the ESA Rosetta spacecraft, has been imaging the nucleus of comet 67P/Churyumov-Gerasimenko and its dust and gas environment since March 2014. The images serve different scientific goals, from morphology and composition studies of the nucleus surface, to the motion and trajectories of dust grains, the general structure of the dust coma, the morphology and intensity of jets, gas distribution, mass loss, and dust and gas production rates.
Aims: We present the calibration of the raw images taken by OSIRIS and address the accuracy that we can expect in our scientific results based on the accuracy of the calibration steps that we have performed.
Methods: We describe the pipeline that has been developed to automatically calibrate the OSIRIS images. Through a series of steps, radiometrically calibrated and distortion corrected images are produced and can be used for scientific studies. Calibration campaigns were run on the ground before launch and throughout the years in flight to determine the parameters that are used to calibrate the images and to verify their evolution with time. We describe how these parameters were determined and we address their accuracy.
Results: We provide a guideline to the level of trust that can be put into the various studies performed with OSIRIS images, based on the accuracy of the image calibration. Title: Photometric properties of the nucleus of 67P/Churyumov-Gerasimenko from OSIRIS/Rosetta, space telescope, and ground-based observations Authors: Lamy, Philippe L.; Faury, Guillaume; Toth, Imre; Jorda, Laurent; Gaskell, Robert; Groussin, Olivier; Capanna, Claire Bibcode: 2015DPS....4741303L Altcode: In-situ imaging of the nucleus of comet 67P/Churyumov-Gerasimenko by the OSIRIS Narrow Angle Camera (NAC) allows an in depth characterization of its photometric properties that can be compared with remote observations thus helping in the interpretation of other nuclei. We performed a photometric analysis of both unresolved and resolved NAC images of the nucleus obtained during twenty five observational campaigns spreading from 23 March to 6 August 2014 with up to twelve filters whose spectral coverage extended from 271 to 986 nm. An accurate photometric calibration was obtained from the observations of a solar analog star, 16 Cyg B. We further combined this analysis with previous observations obtained with the Hubble and Spitzer space telescopes and ground-based telescopes. The analysis further incorporates the shape model and the rotational state the nucleus of \67P independently determined from the NAC images. We will present results on the geometric albedo, phase function, color and thermal properties and put them in the broader context of properties of cometary nuclei. Title: Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations Authors: Groussin, O.; Jorda, L.; Auger, A. -T.; Kührt, E.; Gaskell, R.; Capanna, C.; Scholten, F.; Preusker, F.; Lamy, P.; Hviid, S.; Knollenberg, J.; Keller, U.; Huettig, C.; Sierks, H.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Agarwal, J.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Ip, W. -H.; Kramm, J. -R.; Küppers, M.; Lazzarin, M.; Lara, L. M.; Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Massironi, M.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol, A.; Pajola, M.; Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..32G Altcode: 2015arXiv150902707G
Aims: We study the link between gravitational slopes and the surface morphology on the nucleus of comet 67P/Churyumov-Gerasimenko and provide constraints on the mechanical properties of the cometary material (tensile, shear, and compressive strengths).
Methods: We computed the gravitational slopes for five regions on the nucleus that are representative of the different morphologies observed on the surface (Imhotep, Ash, Seth, Hathor, and Agilkia), using two shape models computed from OSIRIS images by the stereo-photoclinometry (SPC) and stereo-photogrammetry (SPG) techniques. We estimated the tensile, shear, and compressive strengths using different surface morphologies (overhangs, collapsed structures, boulders, cliffs, and Philae's footprint) and mechanical considerations.
Results: The different regions show a similar general pattern in terms of the relation between gravitational slopes and terrain morphology: i) low-slope terrains (0-20°) are covered by a fine material and contain a few large (>10 m) and isolated boulders; ii) intermediate-slope terrains (20-45°) are mainly fallen consolidated materials and debris fields, with numerous intermediate-size boulders from <1 m to 10 m for the majority of them; and iii) high-slope terrains (45-90°) are cliffs that expose a consolidated material and do not show boulders or fine materials. The best range for the tensile strength of overhangs is 3-15 Pa (upper limit of 150 Pa), 4-30 Pa for the shear strength of fine surface materials and boulders, and 30-150 Pa for the compressive strength of overhangs (upper limit of 1500 Pa). The strength-to-gravity ratio is similar for 67P and weak rocks on Earth. As a result of the low compressive strength, the interior of the nucleus may have been compressed sufficiently to initiate diagenesis, which could have contributed to the formation of layers. Our value for the tensile strength is comparable to that of dust aggregates formed by gravitational instability and tends to favor a formation of comets by the accrection of pebbles at low velocities. Title: OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments Authors: Pommerol, A.; Thomas, N.; El-Maarry, M. R.; Pajola, M.; Groussin, O.; Auger, A. -T.; Oklay, N.; Fornasier, S.; Feller, C.; Davidsson, B.; Gracia-Berná, A.; Jost, B.; Marschall, R.; Poch, O.; Barucci, M. A.; Bertaux, J. -L.; La Forgia, F.; Keller, H. U.; Kührt, E.; Lowry, S. C.; Mottola, S.; Naletto, G.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; De Cecco, M.; Debei, S.; Güttler, C.; Fulle, M.; Gutierrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J. -R.; Küppers, E.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. L.; Marzari, F.; Michalik, H.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015A&A...583A..25P Altcode: Since OSIRIS started acquiring high-resolution observations of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, over one hundred meter-sized bright spots have been identified in numerous types of geomorphologic regions, but mostly located in areas receiving low insolation. The bright spots are either clustered, in debris fields close to decameter-high cliffs, or isolated without structural relation to the surrounding terrain. They can be up to ten times brighter than the average surface of the comet at visible wavelengths and display a significantly bluer spectrum. They do not exhibit significant changes over a period of a few weeks. All these observations are consistent with exposure of water ice at the surface of boulders produced by dislocation of the weakly consolidated layers that cover large areas of the nucleus. Laboratory experiments show that under simulated comet surface conditions, analog samples acquire a vertical stratification with an uppermost porous mantle of refractory dust overlaying a layer of hard ice formed by recondensation or sintering under the insulating dust mantle. The evolution of the visible spectrophotometric properties of samples during sublimation is consistent with the contrasts of brightness and color seen at the surface of the nucleus. Clustered bright spots are formed by the collapse of overhangs that is triggered by mass wasting of deeper layers. Isolated spots might be the result of the emission of boulders at low velocity that are redepositioned in other regions. Title: Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft Authors: Fornasier, S.; Hasselmann, P. H.; Barucci, M. A.; Feller, C.; Besse, S.; Leyrat, C.; Lara, L.; Gutierrez, P. J.; Oklay, N.; Tubiana, C.; Scholten, F.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip, W.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Matz, K. -D.; Michalik, H.; Moreno, F.; Mottola, S.; Naletto, G.; Pajola, M.; Pommerol, A.; Preusker, F.; Shi, X.; Snodgrass, C.; Thomas, N.; Vincent, J. -B. Bibcode: 2015A&A...583A..30F Altcode: 2015arXiv150506888F Context. The Rosetta mission of the European Space Agency has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014 and is now in its escort phase. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are onboard Rosetta.
Aims: We present results for the photometric and spectrophotometric properties of the nucleus of 67P derived from the OSIRIS imaging system, which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). The observations presented here were performed during July and the beginning of August 2014, during the approach phase, when OSIRIS was mapping the surface of the comet with several filters at different phase angles (1.3°-54°). The resolution reached up to 2.1 m/px.
Methods: The OSIRIS images were processed with the OSIRIS standard pipeline, then converted into I/F radiance factors and corrected for the illumination conditions at each pixel using the Lommel-Seeliger disk law. Color cubes of the surface were produced by stacking registered and illumination-corrected images. Furthermore, photometric analysis was performed both on disk-averaged photometry in several filters and on disk-resolved images acquired with the NAC orange filter, centered at 649 nm, using Hapke modeling.
Results: The disk-averaged phase function of the nucleus of 67P shows a strong opposition surge with a G parameter value of -0.13 ± 0.01 in the HG system formalism and an absolute magnitude Hv(1,1,0) = 15.74 ± 0.02 mag. The integrated spectrophotometry in 20 filters covering the 250-1000 nm wavelength range shows a red spectral behavior, without clear absorption bands except for a potential absorption centered at ~290 nm that is possibly due to SO2 ice. The nucleus shows strong phase reddening, with disk-averaged spectral slopes increasing from 11%/(100 nm) to 16%/(100 nm) in the 1.3°-54° phase angle range. The geometric albedo of the comet is 6.5 ± 0.2% at 649 nm, with local variations of up to ~16% in the Hapi region. From the disk-resolved images we computed the spectral slope together with local spectrophotometry and identified three distinct groups of regions (blue, moderately red, and red). The Hapi region is the brightest, the bluest in term of spectral slope, and the most active surface on the comet. Local spectrophotometry shows an enhancement of the flux in the 700-750 nm that is associated with coma emissions.

Table 1 is available in electronic form at http://www.aanda.org Title: 3D reconstruction of the final PHILAE landing site: Abydos Authors: Capanna, Claire; Jorda, Laurent; Lamy, Philippe; Gesquière, Gilles; Delmas, Cédric; Durand, Joëlle; Gaudon, Philippe; Jurado, Eric Bibcode: 2015DPS....4741311C Altcode: The Abydos region is the region of the final landing site of the PHILAE lander. The landing site has been potentially identified on images of this region acquired by the OSIRIS imaging system aboard the orbiter before (Oct 22, 2014) and after (Dec 6-13, 2014) the landing of PHILAE (Lamy et al., in prep.). Assuming that this identification is correct, we reconstructed the topography of Abydos in 3D using a method called ``multiresolution photoclinometry by deformation'' (MPCD, Capanna et al., The Visual Computer, 29(6-8): 825-835, 2013). The method works in two steps: (a) a DTM of this region is extracted from the global MPCD shape model, (b) the resulting triangular mesh is progressively deformed at increasing spatial resolution in order to match a set of 14 images of Abydos at pixel resolutions between 1 and 8 m. The method used to perform the image matching is the L-BFGS-b non-linear optimization (Morales et al., ACM Trans. Math. Softw., 38(1): 1-4, 2011).In spite of the very unfavourable illumination conditions, we achieve a vertical accuracy of about 3 m, while the horizontal sampling is 0.5 m. The accuracy is limited by high incidence angles on the images (about 60 deg on average) combined with a complex topography including numerous cliffs and a few overhangs. We also check the compatibility of the local DTM with the images obtained by the CIVA-P instrument aboard PHILAE. If the Lamy et al. identification is correct, our DTM shows that PHILAE landed in a cavity at the bottom of a small cliff of 8 m height. Title: The nucleus of comet 67P through the eyes of the OSIRIS cameras Authors: Guettler, Carsten; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; OSIRIS Team; Capaccioni, Fabrizio; Filacchione, Gianrico; Ciarniello, Mauro; Erard, Stephane; Rinaldi, Giovanna; Tosi, Federico Bibcode: 2015DPS....4741301G Altcode: The Rosetta spacecraft is studying comet 67P/Churyumov-Gerasimenko from a close distance since August 2014. Onboard the spacecraft, the two scientific cameras, the OSIRIS narrow- and the wide-angle camera, are observing the cometary nucleus, its activity, as well as the dust and gas environment.This overview paper will cover OSIRIS science from the early arrival and mapping phase, the PHILAE landing, and the escort phase including the two close fly-bys. With a first characterization of global physical parameters of the nucleus, the OSIRIS cameras also provided the data to reconstruct a 3D shape model of the comet and a division into morphologic sub-units. From observations of near-surface activity, jet-like features can be projected onto the surface and active sources can be correlated with surface features like cliffs, pits, or flat planes. The increase of activity during and after perihelion in August 2015 showed several outbursts, which were seen as strong, collimated jets originating from the southern hemisphere.A comparison of results between different Rosetta instruments will give further inside into the physics of the comet's nucleus and its coma. The OSIRIS and VIRTIS instruments are particularly well suited to support and complement each other. With an overlap in spectral range, one instrument can provide the best spatial resolution while the other is strong in the spectral resolution. A summary on collaborative efforts will be given. Title: Characterization of OSIRIS NAC filters for the interpretation of multispectral data of comet 67P/Churyumov-Gerasimenko Authors: Oklay, N.; Vincent, J. -B.; Sierks, H.; Besse, S.; Pajola, M.; Bertini, I.; Rickman, H.; La Forgia, F.; Barucci, A. M.; Fornasier, S.; Barbieri, C.; Koschny, D.; Lamy, P. L.; Rodrigo, R.; Agarwal, J.; A'Hearn, M. F.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, J. -R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Thomas, N.; Tubiana, C. Bibcode: 2015A&A...583A..45O Altcode: Context. We interpret multicolor data from OSIRISNAC for the remote-sensing exploration of comet 67P/Churyumov-Gerasimenko.
Aims: We determine the most meaningful definition of color maps for the characterization of surface variegation with filters available on OSIRIS NAC.
Methods: We analyzed laboratory spectra of selected minerals and olivine-pyroxene mixtures seen through OSIRIS NAC filters, with spectral methods existing in the literature: reflectance ratios, minimum band wavelength, spectral slopes, band tilt, band curvature, and visible tilt.
Results: We emphasize the importance of reflectance ratios and particularly the relation of visible tilt vs. band tilt. This technique provides a reliable diagnostic of the presence of silicates. Color maps constructed by red-green-blue colors defined with the green, orange, red, IR, and Fe2O3 filters let us define regions that may significantly differ in composition.

Appendices are available in electronic form at http://www.aanda.org Title: The use of 3D shape models of Rosetta targets for morphological studies Authors: Capanna, C.; Jorda, L.; Auger, A. -T.; Groussin, O.; Gaskell, R.; Hviid, S.; Lamy, P. Bibcode: 2015EPSC...10..180C Altcode: New 3D reconstruction techniques have been developed during the last decade to retrieve the global and/or local topography of small solar system bodies from visible images. These techniques can be separated into two categories: the so-called "photoclinometric" and the so-called "photogrammetric" techniques. Two implementations of the photoclinometric technique are available: the SPC technique (StereoPhotoClinometry) which combines sparse stereo with a classical clinometry algorithm[1] and a more recent method called MSPCD (Multi- Resolution Stereo-PhotoClinometry by Deformation) which proceeds by iterative deformation of a triangular mesh in a multi-resolution scheme[2], using stereo points as a guide during the deformation[3]. Our study is based on the 3D shape models of the asteroid Lutetia and of the comet 67P/Churyumov- Gerasimenko retrieved by the SPC and MSPCD methods. More specifically, we describe how the models produced by these two techniques can contribute to detailed and quantitative studies of the morphological properties of small bodies through three test cases shortly described below.• Measurement of crater depth and depth-to-diameter distribution. We show that the reconstruction techniques can lead to systematic differences in the measurement of crater depth. This will be illustrated by a set of craters[4] identified in the Achaia region at the surface of the asteroid 21 Lutetia. • Calculation of the volume of large boulders at the surface of comet 67P/C-G. We show how the reconstruction technique affects significantly the volume determination of a large boulder named Cheops in the Imhotep region. • Measurement of gravitational slopes. We discuss the differences between the gravitational slope distributions in Seth obtained with the SPC and MSPCD models[5]. Since no ground control points are available on small bodies, we use the comparison of high-resolution images with the corresponding synthetic images generated with the models[6] to assess their ability to retrieve detailed topographic features at the surface of 67P/C-G and Lutetia. Title: Two independent and primitive envelopes of the bilobate nucleus of comet 67P Authors: Massironi, Matteo; Simioni, Emanuele; Marzari, Francesco; Cremonese, Gabriele; Giacomini, Lorenza; Pajola, Maurizio; Jorda, Laurent; Naletto, Giampiero; Lowry, Stephen; El-Maarry, Mohamed Ramy; Preusker, Frank; Scholten, Frank; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; A'Hearn, Michael F.; Agarwal, Jessica; Auger, Anne-Thérèse; Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; da Deppo, Vania; Davidsson, Björn; Debei, Stefano; de Cecco, Mariolino; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Groussin, Olivier; Gutiérrez, Pedro J.; Güttler, Carsten; Hviid, Stubbe F.; Ip, Wing-Huen; Knollenberg, Jörg; Kovacs, Gabor; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Lin, Zhong-Yi; Lopez Moreno, Josè J.; Magrin, Sara; Michalik, Harald; Mottola, Stefano; Oklay, Nilda; Pommerol, Antoine; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste Bibcode: 2015Natur.526..402M Altcode: The factors shaping cometary nuclei are still largely unknown, but could be the result of concurrent effects of evolutionary and primordial processes. The peculiar bilobed shape of comet 67P/Churyumov-Gerasimenko may be the result of the fusion of two objects that were once separate or the result of a localized excavation by outgassing at the interface between the two lobes. Here we report that the comet's major lobe is enveloped by a nearly continuous set of strata, up to 650 metres thick, which are independent of an analogous stratified envelope on the minor lobe. Gravity vectors computed for the two lobes separately are closer to perpendicular to the strata than those calculated for the entire nucleus and adjacent to the neck separating the two lobes. Therefore comet 67P/Churyumov-Gerasimenko is an accreted body of two distinct objects with `onion-like' stratification, which formed before they merged. We conclude that gentle, low-velocity collisions occurred between two fully formed kilometre-sized cometesimals in the early stages of the Solar System. The notable structural similarities between the two lobes of comet 67P/Churyumov-Gerasimenko indicate that the early-forming cometesimals experienced similar primordial stratified accretion, even though they formed independently. Title: Identification and Characterization of the landing site of Philae from OSIRIS-NAC Images Authors: Lamy, P.; Faury, G.; Jorda, L.; Romeuf, D.; Gaskell, R.; Jurado, E.; Garmier, R.; Llebaria, A.; Auger, A. -T.; Capanna, C. Bibcode: 2015EPSC...10..783L Altcode: On 12 November 2014, Philae rebounded from its first touchdown at the selected Agilka "J" site on the nucleus of Comet 67P/Churyumov-Gerasimenko, an event captured by the Rosetta's OSIRIS narrowangle camera (NAC [1]). Following two additional bounces, Philae finally landed at the "K" site later named Abydos. Finding its exact location has been a major challenge and could only be indirectly constrained. Thanks to CONSERT measurements, it was finally possible to bound it by an ellipse of approximately 16 x 160 meters. Complementary analyses were performed at CNES-SONC allowing narrowing down the location of Philae to an area of approximately 10 m radius based on illumination conditions and times of contact between Orbiter and Lander during operations. A more precise localization is however hampered by the uncertainties affecting the present 3-dimensional reconstruction (DTM) of the area, presently at the limit of the illuminated part of the nucleus (Figure 1). Spotting Philae on the images of the nucleus has been even more challenging. The highest resolution images of the region of interest after Philae's landing were obtained by the OSIRIS-NAC in mid-December 2014 at a distance of approximately 20 km, the image scale implying that Philae would at best appear as a few bright pixels. Bright "spots" are however ubiquitous on the surface of the nucleus, from glittering rocks or from local icy patches [2]. After meticulously scanning the region of interest, several candidates were spotted but the ambiguity could only be removed when a pre-landing image of the OSIRIS- NAC collection was identified whose geometric conditions (illumination and viewing) were very similar to one of the post-landing images of 12 December 2014. Although taken at different spatial resolutions, all topographic details match, except for one bright spot present on the post-landing image as shown in Figure 2. A false detection or an artefact have been ruled out as this candidate was successfully identified on other images taken in mid-December (Figure 2). A local change in the surface is highly unlikely as no activity has been detected on this presently poorly illuminated part of the nucleus. The determined location is remarkably close to that resulting from the indirect constraints, within approximately 10 m, a further validation of the probable detection of Philae. In fact, this solution satisfies all known constraints, taking into account the present uncertainties affecting the DTM. The Abydos area appears extremely rough with numerous rocks and boulders scattered around, possibly resulting from the local degradation of the rim of the Hatmehit depression. The roughness is confirmed by the large values of the local slopes determined on the present DTM although they are probably underestimated. It is further dramatically illustrated by several anaglyphs constructed from all suitable NAC images of the landing area, thus allowing a stereo view of the local relief. Title: The low strength of 67P: evidence for a primordial nucleus? Authors: Groussin, O.; Jorda, L.; Auger, A. -T.; Kührt, E.; Gaskell, R.; Capanna, C.; Scholten, F.; Preusker, F.; Lamy, P.; Hviid, S.; Knollenberg, J.; Keller, U.; Huettig, C.; Romeuf, D.; Sierks, H.; Osiris Team Bibcode: 2015EPSC...10...39G Altcode: Rosetta is orbiting comet 67P/Churyumov- Gerasimenko since August 2014. The OSIRIS camera [1] onboard this spacecraft has acquired hundreds of images of the nucleus surface, with a spatial resolution down to the decimeter scale [2]. The images reveal a complex nucleus surface made of smooth and hummocky terrains, covered partially or entirely by dust or exposing a consolidated material, pits, cliffs and fractures from the hundred meter scale to the decimeter scale [3]. The nature and origin of these terrains and geomorphological features are far from being understood but remain of paramount importance to better constrain the formation and evolution scenario of the nucleus of 67P and comets in general. This study focuses on the link between the nucleus gravitational slopes and surface morphology, to provide constraints on the nature of the cometary material and its mechanical properties in particular (tensile strength, shear strength and compressive strength). The derived strengths can also be used to constrain the origin of the nucleus of 67P. We derive a low tensile strength for the nucleus, typically from a few tens to a few hundreds Pa [4]. Our results tend to favour a formation of comets by pebble accretion in a region of higher concentration of particles like a vortice [5, 6, 7], which implies a gentle formation process by accretion at low velocity on the order of 1ms-1 or less. On the contrary, the hierarchical accretion model with velocities up to 50ms-1 for particles larger than 1m [8], or the collisional scenario between two large bodies of tens of km or more with an internal compression by gravity larger than 10 kPa [9], although not excluded, are less favored. This points towards a primordial nucleus, which might have not been strongly affected by collisions since its formation. Title: Meter-scale polygons on 67P/Churyumov-Gerasimenko as evidences of near subsurface water ice Authors: Auger, A. -T.; El-Maarry, M. R.; Groussin, O.; Capanna, C.; Jorda, L.; Bouley, S.; Davidsson, B.; Deller, J.; Güttler, C.; Hofmann, M.; Höfner, S.; Lamy, P. L.; Lazzarin, M.; Marchi, S.; Thomas, N.; Vincent, J. -B.; Sierks, H. Bibcode: 2015EPSC...10..516A Altcode: Since August 2014, high spatial resolution images of the nucleus of 67P/Churyumov-Gerasimenko have been acquired by the OSIRIS camera on board the Rosetta spacecraft, enabling to identify meter-scale features on the surface. Among them, we identify polygons with a size from 2 to 20 meters. We define the polygons on 67P as high-centered thermal contraction polygons, which further evolve through preferential sublimation along the cracks. This kind of polygons are known on Earth and Mars as evidences of permanent water ice table in the near subsurface [1,2,3]. Title: Characterization of the Subsurface of 67P/Churyumov-Gerasimenko's Abydos Site Authors: Brugger, B.; Mousis, O.; Morse, A.; Marboeuf, U.; Jorda, L.; Andrews, D.; Barber, S.; Guilbert-Lepoutre, A.; Lamy, P.; Luspay-Kuti, A.; Mandt, K.; Morgan, G.; Sheridan, S.; Vernazza, P.; Wright, I. P. Bibcode: 2015EPSC...10..206B Altcode: We investigate the structure of the subsurface of the Abydos site using a cometary nucleus model with parameters adapted to comet 67P/Churyumov- Gerasimenko and the Abydos landing site. We aim to compare the production rates derived from our model with those of the main molecules measured by Ptolemy. This will allow us to retrieve the depths at which the different molecules still exist in solid form. Title: A Novel Technique for Measuring the Solar Radius from Eclipse Light Curves - Results for 2010, 2012, 2013, and 2015 Authors: Lamy, Philippe; Prado, Jean-Yves; Floyd, Olivier; Rocher, Patrick; Faury, Guillaume; Koutchmy, Serge Bibcode: 2015SoPh..290.2617L Altcode: 2015SoPh..tmp..170L We report on a novel technique for measuring the solar radius during total solar eclipses that exploits light curves recorded just before and after second and third contacts. The measurements are performed by pre-programmed photometers that are deployed over the eclipse paths and are operated without supervision. The recorded light curves are compared to synthetic light curves calculated from high-accuracy ephemerides and lunar-limb profiles constructed from the topographic model of the Moon provided by the Kaguya lunar space mission. A minimization process between the two sets of curves yields the solar radius. Altogether, seventeen determinations have been obtained during the past four total eclipses with the following averages (at a wavelength of 540 nm and scaled to 1 AU): 959.94 ±0.02 arcsec on 11 July 2010, 960.02 ±0.04 arcsec on 13 November 2012, 959.99 ±0.09 arcsec on 3 November 2013, and 960.01 ±0.09 arcsec on 20 March 2015. Part of the differences between these four values may be attributed to weather conditions. Averaging the whole set of measurements yields a radius of 959.99 ±0.06 arcsec (696 ,246 ±45 km), which agrees excellently well with the most recent data and supports an upward revision of the standard IAU value, as previously suggested. Title: Design and modelisation of ASPIICS optics Authors: Galy, C.; Fineschi, S.; Galano, D.; Howard, R. A.; Kintziger, C.; Kirschner, V.; Koutchmy, S.; Lamy, P.; Mazzoli, A.; Melich, R.; Mestreau-Garreau, A.; Renotte, E.; Servaye, J. S.; Stockman, Y.; Thizy, C.; Zhukov, A. Bibcode: 2015SPIE.9604E..0BG Altcode: In the framework of development of ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), the Centre Spatial de Liege is responsible of the optical design of the coronagraph and the optics will be manufactured by TOPTEC. The particularity of this coronagraph is to have an external occulter located 150 m ahead of the first imaging lens. This external occulter is re-imaged on an internal occulter which function is - as in a classical externally occulted Lyot coronagraph - to block the sun light diffracted by the external occulter and to reduce the straylight on the detector. The selection of this configuration is driven by the requirement to observe the corona as close as possible to the solar limb (i.e. 1 RSun) without imaging the limb itself. A requirement of 1.08 RSun is specified at optical design level to grant 1.2 Rsun at instrument level. The coronograph instrument is designed to have a field of view of 1.6° x 1.6° with a resolution of less than 6 arcsec. Its performances are limited by diffraction in a 530 - 590 nm wavelength range. This paper presents the optical design and demonstrates that by design the requirements are fulfilled within the misalignment, manufacturing and thermo-elastic error contributions. Title: Design status of ASPIICS, an externally occulted coronagraph for PROBA-3 Authors: Renotte, Etienne; Alia, Andres; Bemporad, Alessandro; Bernier, Joseph; Bramanti, Cristina; Buckley, Steve; Capobianco, Gerardo; Cernica, Ileana; Dániel, Vladimir; Darakchiev, Radoslav; Darmetko, Marcin; Debaize, Arnaud; Denis, François; Desselle, Richard; de Vos, Lieve; Dinescu, Adrian; Fineschi, Silvano; Fleury-Frenette, Karl; Focardi, Mauro; Fumel, Aurélie; Galano, Damien; Galy, Camille; Gillis, Jean-Marie; Górski, Tomasz; Graas, Estelle; Graczyk, Rafał; Grochowski, Konrad; Halain, Jean-Philippe A.; Hermans, Aline; Howard, Russ; Jackson, Carl; Janssen, Emmanuel; Kasprzyk, Hubert; Kosiec, Jacek; Koutchmy, Serge; Kovačičinová, Jana; Kranitis, Nektarios; Kurowski, Michał; Ładno, Michał; Lamy, Philippe; Landini, Federico; Lapáček, Radek; Lédl, Vít.; Liebecq, Sylvie; Loreggia, Davide; McGarvey, Brian; Massone, Giuseppe; Melich, Radek; Mestreau-Garreau, Agnes; Mollet, Dominique; Mosdorf, Łukasz; Mosdorf, Michał; Mroczkowski, Mateusz; Muller, Raluca; Nicolini, Gianalfredo; Nicula, Bogdan; O'Neill, Kevin; Orleański, Piotr; Palau, Marie-Catherine; Pancrazzi, Maurizio; Paschalis, Antonios; Patočka, Karel; Peresty, Radek; Popescu, Irina; Psota, Pavel; Rataj, Miroslaw; Rautakoski, Jan; Romoli, Marco; Rybecký, Roman; Salvador, Lucas; Servaye, Jean-Sébastien; Solomon, Cornel; Stockman, Yvan; Swat, Arkadiusz; Thizy, Cédric; Thomé, Michel; Tsinganos, Kanaris; Van der Meulen, Jim; Van Vooren, Nico; Vit, Tomáš; Walczak, Tomasz; Zarzycka, Alicja; Zender, Joe; Zhukov, Andrei Bibcode: 2015SPIE.9604E..0AR Altcode: The "sonic region" of the Sun corona remains extremely difficult to observe with spatial resolution and sensitivity sufficient to understand the fine scale phenomena that govern the quiescent solar corona, as well as phenomena that lead to coronal mass ejections (CMEs), which influence space weather. Improvement on this front requires eclipse-like conditions over long observation times. The space-borne coronagraphs flown so far provided a continuous coverage of the external parts of the corona but their over-occulting system did not permit to analyse the part of the white-light corona where the main coronal mass is concentrated. The proposed PROBA-3 Coronagraph System, also known as ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), with its novel design, will be the first space coronagraph to cover the range of radial distances between ~1.08 and 3 solar radii where the magnetic field plays a crucial role in the coronal dynamics, thus providing continuous observational conditions very close to those during a total solar eclipse. PROBA-3 is first a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future European missions, which will fly ASPIICS as primary payload. The instrument is distributed over two satellites flying in formation (approx. 150m apart) to form a giant coronagraph capable of producing a nearly perfect eclipse allowing observing the sun corona closer to the rim than ever before. The coronagraph instrument is developed by a large European consortium including about 20 partners from 7 countries under the auspices of the European Space Agency. This paper is reviewing the recent improvements and design updates of the ASPIICS instrument as it is stepping into the detailed design phase. Title: Mid-Term Quasi-Periodicities and Solar Cycle Variation of the White-Light Corona from 18.5 Years (1996.0 - 2014.5) of LASCO Observations Authors: Barlyaeva, T.; Lamy, P.; Llebaria, A. Bibcode: 2015SoPh..290.2117B Altcode: 2015SoPh..tmp..106B We report on the analysis of the temporal evolution of the solar corona based on 18.5 years (1996.0 - 2014.5) of white-light observations with the SOHO/LASCO-C2 coronagraph. This evolution is quantified by generating spatially integrated values of the K-corona radiance, first globally, then in latitudinal sectors. The analysis considers time series of monthly values and 13-month running means of the radiance as well as several indices and proxies of solar activity. We study correlation, wavelet time-frequency spectra, and cross-coherence and phase spectra between these quantities. Our results give a detailed insight on how the corona responds to solar activity over timescales ranging from mid-term quasi-periodicities (also known as quasi-biennial oscillations or QBOs) to the long-term 11 year solar cycle. The amplitude of the variation between successive solar maxima and minima (modulation factor) very much depends upon the strength of the cycle and upon the heliographic latitude. An asymmetry is observed during the ascending phase of Solar Cycle 24, prominently in the royal and polar sectors, with north leading. Most prominent QBOs are a quasi-annual period during the maximum phase of Solar Cycle 23 and a shorter period, seven to eight months, in the ascending and maximum phases of Solar Cycle 24. They share the same properties as the solar QBOs: variable periodicity, intermittency, asymmetric development in the northern and southern solar hemispheres, and largest amplitudes during the maximum phase of solar cycles. The strongest correlation of the temporal variations of the coronal radiance - and consequently the coronal electron density - is found with the total magnetic flux. Considering that the morphology of the solar corona is also directly controlled by the topology of the magnetic field, this correlation reinforces the view that they are intimately connected, including their variability at all timescales. Title: Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse Authors: Vincent, Jean-Baptiste; Bodewits, Dennis; Besse, Sébastien; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F.; Auger, Anne-Thérèse; Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Capanna, Claire; Cremonese, Gabriele; da Deppo, Vania; Davidsson, Björn; Debei, Stefano; de Cecco, Mariolino; El-Maarry, Mohamed Ramy; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Giacomini, Lorenza; Groussin, Olivier; Guilbert-Lepoutre, Aurélie; Gutierrez-Marques, P.; Gutiérrez, Pedro J.; Güttler, Carsten; Hoekzema, Nick; Höfner, Sebastian; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Lee, Vicky; Leyrat, Cédric; Lin, Zhong-Yi; Lopez Moreno, Josè J.; Lowry, Stephen; Magrin, Sara; Maquet, Lucie; Marchi, Simone; Marzari, Francesco; Massironi, Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Preusker, Frank; Scholten, Frank; Thomas, Nicolas; Toth, Imre; Tubiana, Cecilia Bibcode: 2015Natur.523...63V Altcode: Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments and models cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts. Alternative mechanisms like explosive activity have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply that large heterogeneities exist in the physical, structural or compositional properties of the first few hundred metres below the current nucleus surface. Title: Fractures on comet 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS Authors: El-Maarry, M. R.; Thomas, N.; Gracia-Berná, A.; Marschall, R.; Auger, A. -T.; Groussin, O.; Mottola, S.; Pajola, M.; Massironi, M.; Marchi, S.; Höfner, S.; Preusker, F.; Scholten, F.; Jorda, L.; Kührt, E.; Keller, H. U.; Sierks, H.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Güttler, C.; Fornasier, S.; Fulle, M.; Gutierrez, P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. -H.; Knollenberg, J.; Koschny, D.; Kovacs, G.; Kramm, J. -R.; Küppers, M.; Lamy, P. L.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol, A.; Rickman, H.; Rodrigo, R.; Tubiana, C.; Vincent, J. -B. Bibcode: 2015GeoRL..42.5170E Altcode: The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard the Rosetta spacecraft currently orbiting comet 67P/Churyumov-Gerasimenko has yielded unprecedented views of a comet's nucleus. We present here the first ever observations of meter-scale fractures on the surface of a comet. Some of these fractures form polygonal networks. We present an initial assessment of their morphology, topology, and regional distribution. Fractures are ubiquitous on the surface of the comet's nucleus. Furthermore, they occur in various settings and show different topologies suggesting numerous formation mechanisms, which include thermal insulation weathering, orbital-induced stresses, and possibly seasonal thermal contraction. However, we conclude that thermal insolation weathering is responsible for creating most of the observed fractures based on their morphology and setting in addition to thermal models that indicate diurnal temperature ranges exceeding 200 K and thermal gradients of ~15 K/min at perihelion are possible. Finally, we suggest that fractures could be a facilitator in surface evolution and long-term erosion. Title: GIADA on-board Rosetta: comet 67P/C-G dust coma characterization Authors: Rotundi, Alessandra; Della Corte, Vincenzo; Fulle, Marco; Sordini, Roberto; Ivanovski, Stavro; Accolla, Mario; Ferrari, Marco; Lucarelli, Francesca; Zakharov, Vladimir; Mazzotta Epifani, Elena; López-Moreno, José J.; Rodríguez, Julio; Colangeli, Luigi; Palumbo, Pasquale; Bussoletti, Ezio; Crifo, Jean-Francois; Esposito, Francesca; Green, Simon F.; Grün, Eberhard; Lamy, Philippe L. Bibcode: 2015EGUGA..1713156R Altcode: 21ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spagna GIADA consists of three subsystems: 1) the Grain Detection System (GDS) to detect dust grains as they pass through a laser curtain, 2) the Impact Sensor (IS) to measure grain momentum derived from the impact on a plate connected to five piezoelectric sensors, and 3) the MicroBalances System (MBS); five quartz crystal microbalances in roughly orthogonal directions providing the cumulative dust flux of grains smaller than 10 microns. GDS provides data on grain speed and its optical cross section. The IS grain momentum measurement, when combined with the GDS detection time, provides a direct measurement of grain speed and mass. These combined measurements characterize single grain dust dynamics in the coma of 67P/CG. No prior in situ dust dynamical measurements at these close distances from the nucleus and starting from such high heliocentric distances are available up to date. We present here the results obtained by GIADA, which began operating in continuous mode on 18 July 2014 when the comet was at a heliocentric distance of 3.7 AU. The first grain detection occurred when the spacecraft was 814 km from the nucleus on 1 August 2014. From August the 1st up to December the 11th, GIADA detected more than 800 grains, for which the 3D spatial distribution was determined. About 700 out of 800 are GDS only detections: "dust clouds", i.e. slow dust grains (≈ 0.5 m/s) crossing the laser curtain very close in time (e.g. 129 grains in 11 s), probably fluffy grains. IS only detections are about 70, i.e. ≈ 1/10 of the GDS only. This ratio is quite different from what we got for the early detections (August - September) when the ration was ≈ 3, suggesting the presence of different types of particle (bigger, brighter, less dense).The combined GDS+IS detections, i.e. measured by both the GDS and IS detectors, are about 70 and allowed us to extract the complete set of dust grain parameters, i.e., mass, speed, and geometrical cross-section. These detections allowed us to constraint the grain density. The GIADA detections type was studied as a function of the observational geometrical configuration. Acknowledgments: GIADA was built by a consortium led by the Univ. Napoli "Parthenope" & INAF- Oss. Astr. Capodimonte, in collaboration with the Inst. de Astrofisica de Andalucia, Selex-ES, FI and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with the support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developed from a PI proposal from the University of Kent; sci. & tech. contribution were provided by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their outstanding work. Science support provided was by NASA through the US Rosetta Project managed by the Jet Propulsion Laboratory/California Institute of Technology. GIADA calibrated data will be available through ESA's PSA web site (www.rssd.esa.int/index.php?project=PSA&page=in dex). We would like to thank Angioletta Coradini for her contribution as a GIADA Co-I. Title: Rosetta/OSIRIS - Nucleus morphology and activity of comet 67P/Churyumov-Gerasimenko Authors: Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; Koschny, Detlef Bibcode: 2015EGUGA..1712760S Altcode: ESA's Rosetta mission arrived on August 6, 2014, at target comet 67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. It comprises a Narrow Angle Camera (NAC) for nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field coma investigations. OSIRIS imaged the nucleus and coma of the comet from the arrival throughout the mapping phase, PHILAE landing, early escort phase and close fly-by. The overview paper will discuss the surface morpholo-gy and activity of the nucleus as seen in gas, dust, and local jets as well as small scale structures in the local topography. Title: Morphology of the nucleus of Comet 67P/Churyumov-Gerasimenko from stereo and high spatial resolution OSIRIS-NAC images Authors: Lamy, Philippe; Groussin, Olivier; Romeuf, David; Thomas, Nicolas; Auger, Anne-Thérèse; Jorda, Laurent; Gaskell, Robert; Capanna, Claire; Llebaria, Antoine Bibcode: 2015EGUGA..17.8338L Altcode: The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's Rosetta spacecraft has acquired images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at scales down to 0.2 m/pixel. We employ a variety of techniques to characterize its morphology. Digital terrain modeling (DTM), indispensable for quantitative morphological analysis is performed using stereophotoclinometry (SPC). Depending upon the observational coverage, the resolution of the DTMs exceed 1 m in the most favorable cases. The ultimate stereographic analysis is performed by exploiting pairs of images able to produce anaglyphs whose spatial resolution surpasses that of the DTMs. Digital image filtering and contrast enhancement techniques are applied on the original images as appropriate. We first concentrate on the dust covered terrains possibly resulting from airfall deposits, on the quasi-circular depressions or basins possibly connected to collapses of the underground terrain, and on large scarps that suggest extensive mass disruption. We pay special attention to lithologies that may give clues to the subsurface structure of the nucleus. Our ultimate goal is to understand the processes at work on the nucleus, directly or indirectly connected to its activity as there appears to a variety of processes far beyond what was classicaly considered in the past, for instance airfall deposits, surface dust transport, mass wasting, and insolation weathering. Title: A New 3D Shape Reconstruction Method for celestial bodies: Multi-Resolution Stereophotoclinometry by Deformation Authors: Capanna, Claire; Jorda, Laurent; Gesquière, Gilles; Groussin, Olivier; Gutiérrez, Pedro; Hviid, Stubbe; Lamy, Philippe; Rodionov, Sergey; Vibert, Didier Bibcode: 2015EGUGA..17.5343C Altcode: In astrophysics, direct measures on celestial bodies are not always feasible. 3D shape models allow to overcome this kind of problem. We thus developed a new 3D shape reconstruction method which combines stereo, photoclinometry and the deformation of a triangular mesh describing the surface of the object. The method deforms the mesh - initially a sphere - until the set of synthetic images, created from the mesh (Jorda et al., SPIE 2010) match the observed one. Stereo control points can be used as a constraint in the deformation of the mesh, but it is not required at low resolutions. This new technique has been applied to images of the nucleus of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS instrument aboard the Rosetta spacecraft. It allowed to reconstruct the shape of the nucleus and to retrieve its rotational parameters from low-resolution images obtained with the narrow-angle camera of OSIRIS in mid-July 2014, when stereo-based techniques were still inapplicable. The technique has also been applied to higher-resolution images of the nucleus later on, using the stereo information as a constraint. Title: Monitoring Comet 67P/C-G Micrometer Dust Flux: GIADA onboard Rosetta. Authors: Della Corte, Vincenzo; Rotundi, Alessandra; Ivanovski, Stavro; Accolla, Mario; Ferrari, Marco; Sordini, Roberto; Lucarelli, Francesca; Zakharov, Vladimir; Fulle, Marco; Mazzotta Epifani, Elena; López-Moreno, José J.; Rodríguez, Julio; Colangeli, Luigi; Palumbo, Pasquale; Bussoletti, Ezio; Crifo, Jean-Francois; Esposito, Francesca; Green, Simon F.; Grün, Eberhard; Lamy, Philippe L. Bibcode: 2015EGUGA..17.6559D Altcode: (21)ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spagna The MicroBalance System (MBS) is one of the three measurement subsystems of GIADA, the Grain Impact Analyzer and Dust Accumulator on board the Rosetta/ESA spacecraft (S/C). It consists of five Quartz Crystal Microbalances (QCMs) in roughly orthogonal directions providing the cumulative dust flux of grains smaller than 10 microns. The MBS is continuously monitoring comet 67P/CG since the beginning of May 2014. During the first 4 months of measurements, before the insertion of the S/C in the bound orbit phase, there were no evidences of dust accumulation on the QCMs. Starting from the beginning of October, three out of five QCMs measured an increase of the deposited dust. The measured fluxes show, as expected, a strong anisotropy. In particular, the dust flux appears to be much higher from the Sun direction with respect to the comet direction. Acknowledgment: GIADA was built by a consortum led by the Univ. Napoli "Parthenope" & INAF- Oss. Astr. Capodimonte, in collaboration with the Inst. de Astrofisica de Andalucia, Selex-ES, FI and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with the support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developed from a PI proposal from the University of Kent; sci. & tech. contribution were provided by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their out-standing work. Science support provided was by NASA through the US Rosetta Project managed by the Jet Propulsion Laboratory/ California Institute of Technology. GIADA calibrated data will be available through ESA's PSA web site (www.rssd.esa.int/index.php? project=PSA&page=in dex). We would like to thank Angioletta Coradini for her contribution as a GIADA Co-I. Title: Dust Measurements in the Coma of Comet 67P/Churyumov-Gerasimenko Inbound to the Sun Between 3.7 and 3.4 AU Authors: Rotundi, Alessandra; Della Corte, Vincenzo; Fulle, Marco; Ferrari, Marco; Sordini, Roberto; Ivanovski, Stavro; Accolla, Mario; Lucarelli, Francesca; Zakharov, Vladimir; Mazzotta Epifani, Elena; López-Moreno, José J.; Rodríguez, Julio; Colangeli, Luigi; Palumbo, Pasquale; Bussoletti, Ezio; Crifo, Jean-Francois; Esposito, Francesca; Green, Simon F.; Grün, Eberhard; Lamy, Philippe L. Bibcode: 2015EGUGA..1712907R Altcode: (21) ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spagna, (22) Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany, (23) Center of Studies and Activities for Space (CISAS), University of Padova, I-35131 Padova, Italy, (24) Department of Physics and Astronomy, University of Padova, I-35131 Padova, Italy Comets are the most primitive bodies in the solar system. They retain a cosmo-chemical record of conditions in the solar nebula when the planets were forming, 4.5 billion years ago. While accurate measurements of the gas loss rate from comets are possible under favorable conditions even from Earth, estimates of the dust loss rate so far have been much more uncertain. Multi-parametric models are needed to extract global dust parameters from the dust features of comets (e.g. coma, tails and trails) observed from ground and Earth orbiting telescopes, and it is often difficult to establish the uniqueness of these model results. Critical measurements for understanding the process of accretion and the refractory to volatiles ratio in the solar nebula are being obtained by the Grain Impact Analyzer and Dust Accumulator (GIADA) experiment onboard ESA's Rosetta spacecraft, now orbiting comet 67P/Churyumov-Gerasimenko (67P/CG). GIADA measures the mass, momentum and velocity of individual grains, providing the dust loss rate over three orders of magnitude in mass for grains from tens to hundreds of microns in diameter. GIADA consists of three subsystems: 1) the Grain Detection System (GDS) to detect dust grains as they pass through a laser curtain, 2) the Impact Sensor (IS) to measure grain momentum derived from the impact on a plate connected to five piezoelectric sensors, and 3) the Mi-croBalances System (MBS); five quartz crystal microbalances in roughly orthogonal directions providing the cumu-lative dust flux of grains smaller than 10 microns. GDS provides data on grain speed and its optical cross section. The IS grain momentum measurement, when combined with the GDS detection time, provides a direct measurement of grain speed and mass. These combined measurements characterize single grain dust dynamics in the coma of 67P/CG. The first grain was detected on 1 August 2014 at 814 km from the comet nucleus. Between then and 13 Septem-ber 2014 GIADA detected 35 grains ranging in mass from ~ 5 x 10-10 to 8 x 10-8 kg. Including complementary data from the OSIRIS narrow angle camera, the dust mass loss was calculated over an additional three orders of magni-tude in mass, extending the ejected dust grain sizes up to 2 cm. Combined with data from the MIRO and the ROSINA instruments onboard Rosetta we find a dust/gas mass ratio of 4 +/- 2 averaged over the sunlit nucleus sur-face. The dust to gas ratio may change as the comet approaches closer to the Sun. Acknowledgments: GIADA was built by a consortium led by the Univ. Napoli "Parthenope" & INAF- Oss. Astr. Capodimonte, in collabo-ration with the Inst. de Astrofisica de Andalucia, Selex-ES, FI and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with the support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developed from a PI proposal from the University of Kent; sci. & tech. contribution were pro-vided by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their outstanding work. Science support provided was by NASA through the US Rosetta Project managed by the Jet Propulsion Laboratory/California Institute of Technology. GIADA calibrated data will be available through ESA's PSA web site(www.rssd.esa.int/index.php?project=PSA&page=in dex). We would like to thank Angioletta Coradini for her contribution as a GIADA Co-I. We thank the MIRO, OSIRIS and ROSINA teams for sharing their early results with us. Title: Low and High Albedo Jovian Trojans and Hildas: A Similar or Different Origin? Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan, M.; Lamy, P.; Binzel, R. P. Bibcode: 2015LPI....46.1860M Altcode: 2015LPICo1832.1860M We report the first spectroscopic characterization of a sample of high albedo Trojans and Hildas. Title: Dust Measurements in the Coma of Comet 67P/Churyumov-Gerasimenko Inbound to the Sun Between 3.7 and 3.4 AU Authors: Fulle, M.; Della Corte, V.; Rotundi, A.; Accolla, M.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Sordini, R.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Bussoletti, E.; Crifo, J.; Esposito, F.; Green, S. F.; Gruen, E.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J.; Rodrigo, R.; Weissman, P.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A. C.; Altobelli, N.; Sierks, H.; Agarwal, J.; Bertini, I.; Fornasier, S.; Gutierrez, P. J.; Lara, L.; Guettler, C.; Marzari, F.; Oaklay, N.; Snodgrass, C.; Tubiana, C.; Vincenzo, J. B. Bibcode: 2015LPI....46.2420F Altcode: 2015LPICo1832.2420F GIADA and OSIRIS dust data, combined with data from MIRO and ROSINA instruments onboard Rosetta, from 3.7 to 3.4 AU inbound provide a dust/gas ratio of 4 ± 2. Title: The Geomorphology of Comet 67P: Implications for the Past Collisional Evolution and Formation Authors: Marchi, S.; Rickman, H.; Massironi, M.; Marzari, F.; El-Maari, M. R.; Besse, S.; Thomas, N.; Barbieri, C.; Barucci, M. A.; Fornasier, S.; Giacomini, L.; Keller, H. U.; Kuehrt, E.; Lamy, P.; Lazzarin, M.; Mottola, S.; Naletto, G.; Pajola, M.; Sierks, H. Bibcode: 2015LPI....46.1532M Altcode: 2015LPICo1832.1532M OSIRIS camera onboard Rosetta showed Comet 67P complex surface, characterized by fractures and layering. We discuss their implications for 67P formation. Title: Density and Charge of Pristine Fluffy Particles from Comet 67P/Churyumov-Gerasimenko Authors: Fulle, M.; Della Corte, V.; Rotundi, A.; Weissman, P.; Juhasz, A.; Szego, K.; Sordini, R.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Accolla, M.; Merouane, S.; Zakharov, V.; Mazzotta Epifani, E.; López-Moreno, J. J.; Rodríguez, J.; Colangeli, L.; Palumbo, P.; Grün, E.; Hilchenbach, M.; Bussoletti, E.; Esposito, F.; Green, S. F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jerónimo, J. M.; Leese, M. R.; López-Jiménez, A. C.; Altobelli, N. Bibcode: 2015ApJ...802L..12F Altcode: The Grain Impact Analyzer and Dust Accumulator (GIADA) instrument on board ESA’s Rosetta mission is constraining the origin of the dust particles detected within the coma of comet 67 P/Churyumov-Gerasimenko (67P). The collected particles belong to two families: (i) compact particles (ranging in size from 0.03 to 1 mm), witnessing the presence of materials that underwent processing within the solar nebula and (ii) fluffy aggregates (ranging in size from 0.2 to 2.5 mm) of sub-micron grains that may be a record of a primitive component, probably linked to interstellar dust. The dynamics of the fluffy aggregates constrain their equivalent bulk density to \lt 1 kg m-3. These aggregates are charged, fragmented, and decelerated by the spacecraft negative potential and enter GIADA in showers of fragments at speeds \lt 1 m s-1. The density of such optically thick aggregates is consistent with the low bulk density of the nucleus. The mass contribution of the fluffy aggregates to the refractory component of the nucleus is negligible and their coma brightness contribution is less than 15%. Title: Properties of craters on the Achaia region of Asteroid (21) Lutetia Authors: Auger, A. -T.; Bouley, S.; Jorda, L.; Groussin, O.; Lamy, P. L.; Baratoux, D. Bibcode: 2015Icar..247..137A Altcode: We report on the physical properties of the craters of Achaia region of the main-belt Asteroid (21) Lutetia, based on images obtained with the OSIRIS instrument during the Rosetta flyby that took place on 10 July 2010. Images of the surface were acquired with its Narrow Angle Camera, from which Digital Terrain Models (DTM) of the surface were constructed. These DTMs give access to the geometrical properties of the craters of the asteroid. On a complex asteroid shape, slopes and depth-to-diameter ratios (d/D) of craters should be carefully measured taking into account the local topography to obtain a value that is physically related to the work of forces resisting to mass displacement (associated with gravity and/or material strength) occurring in either excavation or degradation processes. We present new measurements of d/D and internal slopes of impact craters of the Achaia region, which offers optimal conditions of observations and a large population of craters. We find that d/D values for Achaia craters differ from previous works on Lutetia and are consistent with the values found on other asteroids such as (243) Ida or (951) Gaspra. The Achaia region may be divided into three units based on geomorphological analysis. The mean d/D values of the three units are different, revealing differences in resurfacing history by impact-related ejecta blanketing and seismic shaking. Some of these geological events may be recent compared to the age of the region since several lineaments intersect most craters of one of the three units. Independent evidence for ejecta blanket have been given for the unit associated with low d/D values confirming the contribution of this process to crater modification. Moreover, we suggest that displacements along faults identified as surface lineaments may have been responsible for the erasure of small craters. Our results are finally integrated into a chronology sequence of events explaining the present characteristics of the Achaia region. Title: 67P/Churyumov-Gerasimenko: Activity between March and June 2014 as observed from Rosetta/OSIRIS Authors: Tubiana, C.; Snodgrass, C.; Bertini, I.; Mottola, S.; Vincent, J. -B.; Lara, L.; Fornasier, S.; Knollenberg, J.; Thomas, N.; Fulle, M.; Agarwal, J.; Bodewits, D.; Ferri, F.; Güttler, C.; Gutierrez, P. J.; La Forgia, F.; Lowry, S.; Magrin, S.; Oklay, N.; Pajola, M.; Rodrigo, R.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Groussin, O.; Hviid, S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Koschny, D.; Kramm, R.; Kührt, E.; Küppers, M.; Lazzarin, M.; Lamy, P. L.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Sabau, L.; Wenzel, K. -P. Bibcode: 2015A&A...573A..62T Altcode:
Aims: 67P/Churyumov-Gerasimenko is the target comet of the ESA's Rosetta mission. After commissioning at the end of March 2014, the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard Rosetta, started imaging the comet and its dust environment to investigate how they change and evolve while approaching the Sun.
Methods: We focused our work on Narrow Angle Camera (NAC) orange images and Wide Angle Camera (WAC) red and visible-610 images acquired between 2014 March 23 and June 24 when the nucleus of 67P was unresolved and moving from approximately 4.3 AU to 3.8 AU inbound. During this period the 67P - Rosetta distance decreased from 5 million to 120 thousand km.
Results: Through aperture photometry, we investigated how the comet brightness varies with heliocentric distance. 67P was likely already weakly active at the end of March 2014, with excess flux above that expected for the nucleus. The comet's brightness was mostly constant during the three months of approach observations, apart from one outburst that occurred around April 30 and a second increase in flux after June 20. Coma was resolved in the profiles from mid-April. Analysis of the coma morphology suggests that most of the activity comes from a source towards the celestial north pole of the comet, but the outburst that occurred on April 30 released material in a different direction. Title: The morphological diversity of comet 67P/Churyumov-Gerasimenko Authors: Thomas, Nicolas; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe L.; Rodrigo, Rafael; Rickman, Hans; Koschny, Detlef; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F.; Angrilli, Francesco; Auger, Anne-Therese; Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; De Cecco, Mariolino; Debei, Stefano; El-Maarry, Mohamed Ramy; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Giacomini, Lorenza; Groussin, Olivier; Gutierrez, Pedro J.; Güttler, Carsten; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kramm, J. -Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Moreno, Josè J. Lopez; Magrin, Sara; Marchi, Simone; Marzari, Francesco; Massironi, Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Pommerol, Antoine; Preusker, Frank; Sabau, Lola; Scholten, Frank; Snodgrass, Colin; Tubiana, Cecilia; Vincent, Jean-Baptiste; Wenzel, Klaus-Peter Bibcode: 2015Sci...347a0440T Altcode: 2015Sci...347.0440T Images of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) imaging system onboard the European Space Agency’s Rosetta spacecraft at scales of better than 0.8 meter per pixel show a wide variety of different structures and textures. The data show the importance of airfall, surface dust transport, mass wasting, and insolation weathering for cometary surface evolution, and they offer some support for subsurface fluidization models and mass loss through the ejection of large chunks of material. Title: Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun Authors: Rotundi, Alessandra; Sierks, Holger; Della Corte, Vincenzo; Fulle, Marco; Gutierrez, Pedro J.; Lara, Luisa; Barbieri, Cesare; Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; López-Moreno, José J.; Accolla, Mario; Agarwal, Jessica; A'Hearn, Michael F.; Altobelli, Nicolas; Angrilli, Francesco; Barucci, M. Antonietta; Bertaux, Jean-Loup; Bertini, Ivano; Bodewits, Dennis; Bussoletti, Ezio; Colangeli, Luigi; Cosi, Massimo; Cremonese, Gabriele; Crifo, Jean-Francois; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Esposito, Francesca; Ferrari, Marco; Fornasier, Sonia; Giovane, Frank; Gustafson, Bo; Green, Simon F.; Groussin, Olivier; Grün, Eberhard; Güttler, Carsten; Herranz, Miguel L.; Hviid, Stubbe F.; Ip, Wing; Ivanovski, Stavro; Jerónimo, José M.; Jorda, Laurent; Knollenberg, Joerg; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; Lazzarin, Monica; Leese, Mark R.; López-Jiménez, Antonio C.; Lucarelli, Francesca; Lowry, Stephen C.; Marzari, Francesco; Epifani, Elena Mazzotta; McDonnell, J. Anthony M.; Mennella, Vito; Michalik, Harald; Molina, Antonio; Morales, Rafael; Moreno, Fernando; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Ortiz, José L.; Palomba, Ernesto; Palumbo, Pasquale; Perrin, Jean-Marie; Rodríguez, Julio; Sabau, Lola; Snodgrass, Colin; Sordini, Roberto; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste; Weissman, Paul; Wenzel, Klaus-Peter; Zakharov, Vladimir; Zarnecki, John C. Bibcode: 2015Sci...347a3905R Altcode: 2015Sci...347.3905R Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency’s Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10-10 to 10-7 kilograms, and 48 grains of mass 10-5 to 10-2 kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 ± 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails. Title: Probing the Solar Wind Acceleration Region with the Sun-grazing Comet C/2002 S2 Authors: Giordano, S.; Raymond, J. C.; Lamy, P.; Uzzo, M.; Dobrzycka, D. Bibcode: 2015ApJ...798...47G Altcode: 2014arXiv1411.1300G Comet C/2002 S2, a member of the Kreutz family of sungrazing comets, was discovered in white-light images of the Large Angle and Spectromeric Coronagraph Experiment coronagraph on the Solar and Heliospheric Observatory (SOHO) on 2002 September 18 and observed in H I Lyα emission by the SOHO Ultraviolet Coronagraph Spectrometer (UVCS) instrument at four different heights as it approached the Sun. The H I Lyα line profiles detected by UVCS are analyzed to determine the spectral parameters: line intensity, width, and Doppler shift with respect to the coronal background. Two-dimensional comet images of these parameters are reconstructed at the different heights. A novel aspect of the observations of this sungrazing comet data is that, whereas the emission from most of the tail is blueshifted, that along one edge of the tail is redshifted. We attribute these shifts to a combination of solar wind speed and interaction with the magnetic field. In order to use the comet to probe the density, temperature, and speed of the corona and solar wind through which it passes, as well as to determine the outgassing rate of the comet, we develop a Monte Carlo simulation of the H I Lyα emission of a comet moving through a coronal plasma. From the outgassing rate, we estimate a nucleus diameter of about 9 m. This rate steadily increases as the comet approaches the Sun, while the optical brightness decreases by more than a factor of 10 and suddenly recovers. This indicates that the optical brightness is determined by the lifetimes of the grains, sodium atoms, and molecules produced by the comet. Title: On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko Authors: Sierks, Holger; Barbieri, Cesare; Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F.; Angrilli, Francesco; Auger, Anne-Therese; Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Giacomini, Lorenza; Groussin, Olivier; Gutierrez-Marques, Pablo; Gutiérrez, Pedro J.; Güttler, Carsten; Hoekzema, Nick; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor; Kramm, J. Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Leyrat, Cédric; Lopez Moreno, Josè J.; Magrin, Sara; Marchi, Simone; Marzari, Francesco; Massironi, Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Pertile, Marco; Preusker, Frank; Sabau, Lola; Scholten, Frank; Snodgrass, Colin; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste; Wenzel, Klaus-Peter; Zaccariotto, Mirco; Pätzold, Martin Bibcode: 2015Sci...347a1044S Altcode: 2015Sci...347.1044S Images from the OSIRIS scientific imaging system onboard Rosetta show that the nucleus of 67P/Churyumov-Gerasimenko consists of two lobes connected by a short neck. The nucleus has a bulk density less than half that of water. Activity at a distance from the Sun of >3 astronomical units is predominantly from the neck, where jets have been seen consistently. The nucleus rotates about the principal axis of momentum. The surface morphology suggests that the removal of larger volumes of material, possibly via explosive release of subsurface pressure or via creation of overhangs by sublimation, may be a major mass loss process. The shape raises the question of whether the two lobes represent a contact binary formed 4.5 billion years ago, or a single body where a gap has evolved via mass loss. Title: Instant: An Innovative L5 Small Mission Concept for Coordinated Science with Solar Orbiter and Solar Probe Plus Authors: Lavraud, B.; Liu, Y. D.; Harrison, R. A.; Liu, W.; Auchere, F.; Gan, W.; Lamy, P. L.; Xia, L.; Eastwood, J. P.; Wimmer-Schweingruber, R. F.; Zong, Q.; Rochus, P.; Maksimovic, M.; Temmer, M.; Escoubet, C. P.; Kilpua, E.; Rouillard, A. P.; Davies, J. A.; Vial, J. C.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard, T. A.; DeForest, C. E. Bibcode: 2014AGUFMSH21B4109L Altcode: We will present both the science objectives and related instrumentation of a small solar and heliospheric mission concept, INSTANT: INvestigation of Solar-Terrestrial Activity aNd Transients. It will be submitted as an opportunity to the upcoming ESA-China S-class mission call later this year. This concept was conceived to allow innovative measurements and unprecedented, early determination of key properties of Earthbound CMEs from the L5 vantage point. Innovative measurements will include magnetic field determination in the corona thanks to Hanle measurement in Lyman-α and polarized heliospheric imaging for accurate determination of CME trajectories. With complementary in situ measurements, it will uniquely permit solar storm science, solar storm surveillance, and synergy with Solar Orbiter and Solar Probe Plus (the ESA-China S2 mission launch is planned in 2021). Title: Multi-Resolution Stereophotoclinometry by Deformation, a New 3D Shape Reconstruction Method Applied to ROSETTA/OSIRIS Images Authors: Capanna, C.; Jorda, L.; Gesquière, G.; Gaskell, R. W.; Groussin, O.; Gutiérrez, P.; Hviid, S. F.; Lamy, P. L.; Preusker, F.; Rodionov, S.; Scholten, F.; Vibert, D. Bibcode: 2014AGUFM.P41C3941C Altcode: We developed a new 3D shape reconstruction method which combines stereo, photoclinometry and the deformation of a triangular mesh describing the surface of the object. The method deforms the mesh - initially a sphere - until the set of synthetic images, created from the mesh (Jorda et al., SPIE 2010) match the observed one. Stereo control points can be used as a constraint in the deformation of the mesh, but it is not required at low resolutions.This new technique has been applied to images of the nucleus of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS instrument aboard the Rosetta spacecraft. The technique allowed to reconstruct the shape of the nucleus and to retrieve its rotational parameters from low-resolution images obtained with the narrow-angle camera of OSIRIS in mid-July 2014, when stereo-based techniques were still inapplicable. This model called "SHAP1" has been delivered to ESA and to the lander team in July. The technique has also been applied to higher-resolution images of the nucleus later on, using the stereo information as a constraint. A comparison of the reconstructed global and local models with those retrieved with other techniques, such as stereophotoclinometry (Gaskell et al., MPS 2008) and stereophotogrammetry (Preusker et al., PSS 2012) will be presented. Title: GIADA On-Board Rosetta: Early Dust Grain Detections and Dust Coma Characterization of Comet 67P/C-G Authors: Rotundi, A.; Della Corte, V.; Accolla, M.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Mazzotta Epifani, E.; Sordini, R.; Palumbo, P.; Colangeli, L.; Lopez-Moreno, J. J.; Rodriguez, J.; Fulle, M.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S.; Grün, E.; Lamy, P. L.; McDonnell, T.; Mennella, V.; Molina, A.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rodrigo, R.; Weissman, P. R.; Zakharov, V.; Zarnecki, J. Bibcode: 2014AGUFM.P32B..05R Altcode: GIADA (Grain Impact Analyzer and Dust Accumulator) flying on-board Rosetta is devoted to study the cometary dust environment of 67P/Churiumov-Gerasimenko. GIADA is composed of 3 sub-systems: the GDS (Grain Detection System), based on grain detection through light scattering; an IS (Impact Sensor), giving momentum measurement detecting the impact on a sensed plate connected with 5 piezoelectric sensors; the MBS (MicroBalances System), constituted of 5 Quartz Crystal Microbalances (QCMs), giving cumulative deposited dust mass by measuring the variations of the sensors' frequency. The combination of the measurements performed by these 3 subsystems provides: the number, the mass, the momentum and the velocity distribution of dust grains emitted from the cometary nucleus.No prior in situ dust dynamical measurements at these close distances from the nucleus and starting from such large heliocentric distances are available up to date. We present here the first results obtained from the beginning of the Rosetta scientific phase. We will report dust grains early detection at about 800 km from the nucleus in August 2014 and the following measurements that allowed us characterizing the 67P/C-G dust environment at distances less than 100 km from the nucleus and single grains dynamical properties. Acknowledgements. GIADA was built by a consortium led by the Univ. Napoli "Parthenope" & INAF-Oss. Astr. Capodimonte, IT, in collaboration with the Inst. de Astrofisica de Andalucia, ES, Selex-ES s.p.a. and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with a support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developped from a PI proposal supported by the University of Kent; sci. & tech. contribution given by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their outstanding work. Science support provided by NASA through the US Rosetta Project managed by JPL/California Institute of Technology. GIADA calibrated data will be available through the ESA's PSA web site (www.rssd.esa.int/index.php?project=PSA&page=index). Thanks Angioletta. Title: The photosphere-corona Interface: enrichement of the corona in low FIP elements and helium shells Authors: Bazin, C.; Koutchmy, S.; Lamy, P.; Veselovski, I. Bibcode: 2014sf2a.conf..209B Altcode: Slitless consecutive spectra were obtained during the contacts of the last total solar eclipses (2008, 2009, 2010, 2012, et 2013). They allowed to show that the overabundance of low First Ionisation Potential (FIP) elements (Fe II, Ti II, Ba II) in the corona comes from the low layers of the solar atmosphere, just near and above the temperature minimum region of the high photosphere. All spectra are recorded with a fast CCD/CMOS camera, with an equivalent radial resolution of 60 milliarcseconds, or 45 km in the solar atmosphere, above a solar edge not affected by the parasitic light like it is outside of total eclipse conditions. Many emission lines of low FIP elements appear in regions situated between 200 to 600 km above the solar limb defined by the true continuum measured between the lines. This continuum appears at these altitudes where the beta of the plasma is near 1. The He I 4713 Å and He II 4686 Å (Paschen alpha line) shells appear at the height of 800 km above the solar edge and higher. The light curve I = f(h) of each ion is located at a particuliar altitude in the solar atmosphere. The scale height corresponds to a density variation, which allows to evaluate the temperature thanks to the hydrostatic equilibrium assumption. Moreover, with ionised Titanium lines taken as markers, we show a similarity between the photosphere-corona interface and the prominence-corona interface. We discuss the role of the magnetic field and the ambipolar diffusion for supplying the corona in mass, without taking into account the role of spicules. The photo-ionisation of the helium lines by the EUV coronal lines is illustrated thanks to an extract of SDO/AIA coronal stacked image simultaneously obtained. Title: Overview of the Geomorphology of the Nucleus of Comet 67P/Churyumov-Gerasimenko from OSIRIS Observations Authors: Groussin, O.; Thomas, N.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rickman, H.; Rodrigo, R.; Koschny, D. Bibcode: 2014AGUFM.P33F..01G Altcode: Because of the very peculiar conditions at the surface of cometary nuclei with very low gravity, outgassing, presence of ices and dust, their geomorphology is particularly complex. The presence of hummocky terrains (e.g., pits, hills, ridges, ...) and smooth terrains (e.g., mesas, …) and their spatial distribution over the surface contain very valuable information to understand how comets work and to which extend they may still contain pristine materials on or close to their surface. Since July 2014, the Rosetta spacecraft has taken numerous high spatial resolution images (meter scale) of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko with the OSIRIS cameras NAC (Narrow Angle Camera) and WAC (Wide Angle Camera). In this paper, we will present an overview of the geomorphologic features observed on this comet nucleus, including the cartography of the main features, and try to propose a scenario for the chronology of their formation and evolution. Title: Experimental study of an uncooled microbolometer array for thermal mapping and spectroscopy of asteroids Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. -L. Bibcode: 2014ExA....38..381B Altcode: We report on the experimental study of the imaging and spectroscopic capabilities of an uncooled microbolometer array for space missions to small bodies in the inner solar system. The selected Nano640E T M device manufactured by the ULIS company (Grenoble, France) has a format of 640x480 pixels and can measure temperatures down to at least 255 K, the lower limit reached in our tests. It has a Noise Equivalent Temperature Difference (NETD) of 40.9 ±4.5 mK (300 K, F/0.86) and the capability to produce excellent, radiometrically calibrated images with an error of the order of 1 to 5 K depending upon the number of calibration sources. Using a set of neutral density filters, we determined the signal-to-noise ratio (SNR) of a spectrum acquired by the detector, as a function of the scene temperature, wavelength and spectral resolution. Considering an asteroid at 1 AU from the Sun, an optical system at F/0.86, a spectral resolution of 0.3 μm and a scene temperature of >350 K, the resulting spectrum has sufficient SNR to properly identify the main mineralogical emission features. Our results show that uncooled microbolometer arrays are very promising to acquire calibrated thermal images and mid-infrared (8-14 μm) spectra of the surface of small bodies in the inner solar system. Title: The Geomorphology of Comet Churymov-Gerasimenko As Revealed By Rosetta/Osiris: Implicationsfor Past Collisional Evolution Authors: Marchi, S.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.; Besse, S.; Cremonese, G.; Ip, W. H.; Keller, H. U.; Koschny, D.; Kuhrt, E.; Lamy, P. L.; Marzari, F.; Massironi, M.; Pajola, M.; Rickman, H.; Rodrigo, R.; Sierks, H.; Snodgrass, C.; Thomas, N.; Vincent, J. B. Bibcode: 2014AGUFM.P41C3940M Altcode: In this paper we present the major geomorphological features of comet Churymov-Gerasimenko (C-G), with emphasis on those that may have formed through collisional processes. The C-G nucleus has been imaged with the Rosetta/OSIRIS camera system at varying spatial resolution. At the moment of this writing the maximum spatial resolution achieved is ~20 meter per pixel, and it will improve to reach the unprecedented centimeter-scale in November 2014. This resolution should allow us to identify and characterize pits, lineaments and blocks that could be the result of collisional evolution. Indeed, C-G has spent some 1000 years on orbits crossing the main asteroid belt, and a much longer time in the outer solar system. Collisions may have, therefore, shaped the morphology of the nucleus in various ways. Previously imaged Jupiter Family Comets (e.g., Tempel 1) show significant numbers of pits and lineaments, some of which could be due to collisions. Additional proposed formation mechanisms are related to cometary activity processes, such as volatile outgassing.In addition to small scale features, the overall shape of C-G could also provide insights into the role of collisional processes. A striking feature is that C-G's shape is that of a contact binary. Similar shapes have been observed on rocky asteroids (e.g., Itokawa) and are generally interpreted as an indication of their rubble pile nature. A possibility is that C-G underwent similar processes, and therefore it may be constituted by reaccumulated fragments ejected from a larger precursor. An alternative view is that the current shape is the result of inhomogeneous outgassing activity, which may have dug a ~1-km deep trench responsible for the apparent contact binary shape.The role of the various proposed formation mechanisms (collisional vs outgassing) for both small scale and global features will be investigated and their implications for the evolution of C-G will be discussed. Title: The Nucleus of Comet 67P/Churyumov-Gerasimenko : a New Case of Contact Binary ? Authors: Lamy, P. L.; A'Hearn, M. F.; Groussin, O.; Jorda, L.; Keller, H. U.; Rickman, H. Bibcode: 2014AGUFM.P41C3937L Altcode: The nucleus of comet 67P/Churyumov-Gerasimenko appears to be formed of two components as revealed by images obtained with the OSIRIS narrow angle camera and the derived 3-D shape model (Jorda et al. 2014). This shape raises questions far beyond the obvious differences with the nuclei visited so far. We will explore the possible scenarios that may explain it. Whereas contact- binaries have been advocated for elongated nuclei (e.g., 19P/Borrelly and 103P/Hartley 2), the only unquestionable case remains that of 8P/Tuttle based on radar imaging (Harmon at al. 2010) and indirectly confirmed by HST observations (Lamy et al. 2008). However 8P originates from the Oort cloud where the collisional activity is essentially non-existent. A contact-binary among the Jupiter family comets (JFC) such as 67P would have profound implications since it must be primordial and the comet must have survived a possible history of collisions in the Kuiper belt. The present cumulative distribution function of size of nuclei of JFC comets indeed suggests a collisionally-relaxed population. Asymmetric erosion of an initially larger more regular body or even of a pre-existing contact binary will be studied in the framework of the past dynamical evolution of 67P (e.g., Groussin et al. 2007). Although unlikely, the scenario of a re-accumulated body following a catastrophic collision will be considered. Forthcoming images at higher spatial resolution with OSIRIS on the orbiter and CIVA and the lander will hopefully help deciphering the origin of the nucleus of 67P and restricting the number of possible scenarios. Title: Geomorphology of Active Regions on Comet 67P/Churyumov-Gerasimenko from Osiris Observations Authors: Auger, A. T.; Groussin, O.; Jorda, L.; Bouley, S.; Lamy, P. L.; Cremonese, G.; Thomas, N.; Sierks, H. Bibcode: 2014AGUFM.P41C3936A Altcode: The geomorphological study of active regions on comets provides valuable insights to understand how comets work and to which extend they may still contain pristine materials on or close to their surface. The Rosetta spacecraft is orbiting comet 67P/Churyumov-Gerasimenko since summer 2014 and offers a unique opportunity to address this science topic. The Narrow and Wide Angle Cameras of the OSIRIS imaging experiment have acquired numerous images of the nucleus surface, with a spatial resolution down to the meter scale. Here, we focus on the geomorphology of some specific, active, regions of the nucleus, releasing materials from their surface or from their upper layers. With the help of digital terrains models and GIS tools, we map these regions and report their size, area, shape, slopes and surface roughness. This detailed analysis give us a reference point to emphasize their evolution as the comet approaches perihelion, but also provide information on the possibly pristine nature of these morphologies. Title: Comet 67P/Churyumov-Gerasimenko - First Science Results by Rosetta/OSIRIS Authors: Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Angrilli, F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Besse, S.; Bodewits, D.; Capanna, C.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Ferri, F.; Fornasier, S.; Fulle, M.; Gaskell, R. W.; Groussin, O.; Güttler, C.; Gutiérrez, P.; Hviid, S. F.; Ip, W. H.; Jorda, L.; Keller, H. U.; Joerg, K.; Kramm, R.; Kuhrt, E.; Küppers, M.; La Forgia, F.; Lara, L.; Lazzarin, M.; Leyrat, C.; Moreno, J. F.; Lowry, S.; Magrin, S.; Marchi, S.; Marzari, F.; Michalik, H.; Mottola, S.; Account, T.; Oklay, N.; Pajola, M. Bibcode: 2014AGUFM.P32B..02S Altcode: Abstract ESA's Rosetta mission arrived on August 6, 2014, at target comet 67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. It comprises a Narrow Angle Camera (NAC) for nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field coma investigations. We present the first science results achieved by OSIRIS from the arrival at the comet throughout the mapping phase. The overview will cover surface morphology and activity of the nucleus as seen in gas, dust, and local jets. Acknowledgements OSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged. We thank the Rosetta Science Ground Segment at ESAC, the Rosetta Mission Operations Centre at ESOC and the Rosetta Project at ESTEC for their outstanding work enabling the science return of the Rosetta Mission. Title: Albedo and color variegations on 67/P Churyumov-Gerasimenko as observed by OSIRIS/Rosetta Authors: Leyrat, Cedric; Barucci, Maria Antonietta; Fornasier, Sonia; Sierks, Holger; Hasselmann, Pedro; Besse, Sebastien; Oklay, Nilda; Jorda, Laurent; Barbieri, Cesare; Lamy, Philippe; Koschny, Detlef; Magrin, Sara; Bertini, Ivano; La Forgia, Fiorangela; A'Hearn, Michael; Bertaux, Jean Loup; Davidsson, Bjorn; Fulle, Marco; Groussin, Olivier; Gutierrez, Pablo; Hviid, Stubbe; Keller, Horst Uwe; Kueppers, Michael; Lazzarin, Monica; Kuehrt, Ekkehard; Lara, Luisa; Thomas, Nicolas; Vincent, Jean-Baptiste; Pajola, Maurizio Bibcode: 2014DPS....4610002L Altcode: The ESA Rosetta spacecraft is in orbit around its target 67/P Churyumov-Gerasimenko since August 6th 2014. The OSIRIS camera system composed of the NAC (Narrow angle camera) and the WAC (Wide angle Camera) has the capability to image both the nucleus and the coma at different wavelengths from 0.245 microns up to 1 micron using filters. First images acquired from 100km distance have already revealed a very complex shape and potential areas with photometric variations. From August 2014 to the Philae landing event in November 2014, the nucleus surface will be mapped at multiple resolutions (1m up to 20 cm), helping in the landing site selection process. Such images will be obtained at very different incidence, emission and phase angles, allowing us to correct from topographical features the photometric properties of the surface. This presentation will focus on the albedo and colors variations, and on the spectral slopes derived from the OSIRIS filters. Of particular interest will be the identification of ices on the surface, and the mineralogical differences between different areas characterized by different topographic features. Title: Comet 67P/Churyumov-Gerasimenko: First science results by Rosetta/OSIRIS Authors: Thomas, Nicolas; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Agarwal, Jessica; A'Hearn, Michael; Angrilli, Francesco; Barucci, Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Groussin, Olivier; Güttler, Carsten; Gutierrez, Pedroj; Hviid, Stubbe; Ip, Wing-Huen; Jorda, Laurent; Keller, Horst Uwe; Knollenberg, Jörg; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; LaForgia, Fiorangela; Lara, Luisa; Lazzarin, Monica; Leyrat, Cedric; Lopez Moreno, Jose Juan; Lowry, Stephen; Magrin, Sara; Marchi, Simone; Marzari, Francesco; Michalik, Harald; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Sabau, Lola; Snodgrass, Colin; Tubiana, Cecilia; Vincent, Jean-Baptiste; Wenzel, Peter Bibcode: 2014DPS....4610001T Altcode: ESA’s Rosetta mission arrived on August 6, 2014, at target comet 67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. It comprises a Narrow Angle Camera (NAC) for nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field coma investigations.We present the first science results achieved by OSIRIS from the arrival at the comet throughout the mapping phase. The overview will cover surface morphology and activity of the nucleus as seen in gas, dust, and local jets.AcknowledgementsOSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged. We thank the Rosetta Science Ground Segment at ESAC, the Rosetta Mission Operations Centre at ESOC and the Rosetta Project at ESTEC for their outstanding work enabling the science return of the Rosetta Mission. Title: Hubble Space Telescope Observations of the Nucleus of Comet C/2012 S1 (ISON) Authors: Lamy, Philippe L.; Toth, Imre; Weaver, Harold A. Bibcode: 2014ApJ...794L...9L Altcode: We report on the analysis of several sequences of broadband visible images of comet C/2012 S1 (ISON) taken with the Wide Field Camera 3 of the Hubble Space Telescope on 2013 April 10, May 8, October 9, and November 1 in an attempt to detect and characterize its nucleus. Whereas the overwhelming coma precluded the detection of the nucleus in the first two sequences, the contrast was sufficient in early October to unambiguously retrieve the signal from the nucleus. Two images taken within a few minutes led to similar V magnitudes for the nucleus of 21.97 and 22.0 with a 1σ uncertainty of 0.065. Assuming a standard value for the geometric albedo (0.04) and a linear phase function with a coefficient of 0.04 mag deg-1, these V values imply that the nucleus radius is 0.68 ± 0.02 km. Although this result does depend on these two assumptions, we argue that the radius most likely lies in the range 0.6-0.9 km. This result is consistent with the constraints derived from the water production rates reported by Combi et al. The last sequence of images in 2013 November revealed temporal variation of the innermost coma. If attributed to a single rotating jet, this coma brightness variation suggests the rotational period of the nucleus may be close to ~10.4 hr. Title: The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta Authors: Mottola, S.; Lowry, S.; Snodgrass, C.; Lamy, P. L.; Toth, I.; Rożek, A.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Barbieri, C.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P.; Hviid, S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P.; Agarwal, J.; Bertini, I.; Ferri, F.; Güttler, C.; Magrin, S.; Oklay, N.; Tubiana, C.; Vincent, J. -B. Bibcode: 2014A&A...569L...2M Altcode:
Aims: Approach observations with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard Rosetta are used to determine the rotation period, the direction of the spin axis, and the state of rotation of comet 67P's nucleus.
Methods: Photometric time series of 67P have been acquired by OSIRIS since the post wake-up commissioning of the payload in March 2014. Fourier analysis and convex shape inversion methods have been applied to the Rosetta data as well to the available ground-based observations.
Results: Evidence is found that the rotation rate of 67P has significantly changed near the time of its 2009 perihelion passage, probably due to sublimation-induced torque. We find that the sidereal rotation periods P1 = 12.76129 ± 0.00005 h and P2 = 12.4043 ± 0.0007 h for the apparitions before and after the 2009 perihelion, respectively, provide the best fit to the observations. No signs of multiple periodicity are found in the light curves down to the noise level, which implies that the comet is presently in a simple rotation state around its axis of largest moment of inertia. We derive a prograde rotation model with spin vector J2000 ecliptic coordinates λ = 65° ± 15°, β = + 59° ± 15°, corresponding to equatorial coordinates RA = 22°, Dec = + 76°. However, we find that the mirror solution, also prograde, at λ = 275° ± 15°, β = + 50° ± 15° (or RA = 274°, Dec = + 27°), is also possible at the same confidence level, due to the intrinsic ambiguity of the photometric problem for observations performed close to the ecliptic plane.

Table 1 is available in electronic form at http://www.aanda.org Title: Time dependent tomographic reconstruction of the solar corona Authors: Peillon, C.; Vibert, D.; Frazin, R.; de Patoul, J.; Lamy, P. Bibcode: 2014ssip.confP...1P Altcode: 2014ssip.confP...1C The distribution of the electron density in the corona is crucial to advance the knowledge in understanding the nature of solar coronal phenomena. Several methods for the reconstruction of 3D density of the solar corona from projection data have been proposed. One of the major difficulties is the problem of the restrictive assumption that the structure of the corona does not vary with time. The solar temporal evolution introduces a lot of errors in classic tomographic reconstruction. In this poster we present a new time dependent tomography method by adding a spatial, temporal and rotational regularization matrices. We perform the method on images from a 3D MHD model of the corona during a period of 14 days in November 2008. We compute the normalized error between the model and the reconstruction in order to estimate the quality of the reconstruction. We also perform the developed tomography methods on polarized brightness images of the SOHO/LASCO instrument. We show that the new time dependent method decrease the number of artefacts by comparing our results with classic static tomographic reconstruction. In particular, we show that the spatial and temporal regularization matrices improves significantly the reconstruction and that the rotational regularization is useful when using a large amount of images during the 14 days period. Title: Constraints on the subsurface structure and density of the nucleus of Comet 67P/Churyumov-Gerasimenko from Arecibo radar observations Authors: Kamoun, P.; Lamy, P. L.; Toth, I.; Herique, A. Bibcode: 2014A&A...568A..21K Altcode: Context. Little is known about the internal structure of cometary nuclei. In addition to understanding their accretion in the early solar nebula and their subsequent evolution in the solar system, we find this question to be of acute and timely interest in the case of 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) due to be visited by the Rosetta spacecraft in the second half of 2014. In particular, the successful landing of the Philae surface module depends critically upon the bulk density of the nucleus and the structure of its surface layer.
Aims: In addition to fostering our general knowledge of these properties, it is important to exploit all possible information to assist in preparing the delivery of Philae.
Methods: We performed an in-depth analysis of the observations done with the radar system of the Arecibo Observatory in November 1982 when comet 67P/C-G had a close encounter with Earth at a geocentric distance of 0.4AU taking our present knowledge of the properties of its nucleus (size, rotational state) into account.
Results: In the absence of a detectable radar echo, we determined a maximum radar cross section of 0.7 km2, leading to a maximum radar albedo of 0.05. This low albedo probably results from a combination of a low radar reflectivity material and a lightly packed upper layer of the nucleus with substantial roughness (rms slope of ≈55°), consistent with its low thermal inertia. Based on radar observations of other cometary nuclei and asteroids, it is unlikely that the albedo can be lower than 0.04 so that we were able to constrain the dielectric permittivity of the subsurface layer to a narrow range of 1.9 to 2.1. Laboratory measurements and our modeling of mixtures of ice and dust have led to a porosity in the range of approximately 55 to 65% and a density in the range of ≈600 to ≈1000 kg m-3 for the top ≈2.5 m layer of the nucleus. This would be the bulk density range for a homogeneous nucleus and would place the success of the landing at risk, but an inhomogeneous nucleus with an overall density below this range remains a possibility. Title: Similar origin for low- and high-albedo Jovian Trojans and Hilda asteroids? Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan, M.; Lamy, P.; Binzel, R. P. Bibcode: 2014A&A...568L...7M Altcode: 2014arXiv1407.7016M Hilda asteroids and Jupiter Trojans are two low-albedo (pv ~ 0.07) populations for which the Nice model predicts an origin in the primordial Kuiper Belt region. However, recent surveys by WISE and the Spitzer Space Telescope (SST) have revealed that ~2% of these objects possess high albedos (pv ≥ 0.15), which might indicate interlopers - that is, objects not formed in the Kuiper Belt - among these two populations. Here, we report spectroscopic observations in the visible and / or near-infrared spectral ranges of twelve high-albedo (pv > 0.15) Hilda asteroids and Jupiter Trojans. These twelve objects have spectral properties similar to those of the low-albedo population, which suggests a similar composition and hence a similar origin for low- and high-albedo Hilda asteroids and Jupiter Trojans. We therefore propose that most high albedos probably result from statistical bias or uncertainties that affect the WISE and SST measurements. However, some of the high albedos may be true and the outcome of some collision-induced resurfacing by a brighter material that could include water ice. Future work should attempt to investigate the nature of this supposedly bright material. The lack of interlopers in our sample allows us to set an upper limit of 0.4% at a confidence level of 99.7% on the abundance of interlopers with unexpected taxonomic classes (e.g., A-, S-, V-type asteroids) among these two populations.

Reflectance spectra presented in this paper are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/L7Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (ESO program ID: 091.C-0247). Title: Constraints on the nucleus of comet C/2012 S1 (ISON) from the Hubble Space Telescope observations Authors: Lamy, P.; Toth, I.; Li, J.; Weaver, H. Bibcode: 2014acm..conf..304L Altcode: Comet C/2012 S1 (ISON) was both a dynamically new comet, visiting the inner solar system for the first time since being scattered and deeply frozen in the Oort Cloud, and a sungrazing comet. This unique combination made it an attractive target for the Hubble Space Telescope. It was observed on 10 April 2013 when the comet was 4.15 au from the Sun, 4.24 au from the Earth, and at a phase angle of 13.7°, henceforth well before C/ISON crossed the ''snow line'' (2.5--3 au), avoiding strong activity driven by water-ice sublimation and, thus, potentially increasing the chance of detecting its nucleus. The observations were performed over three separate orbits spanning a time interval of 18 hours using the Wide Field Camera 3 (WFC3) UVIS detector to image C/ISON through two broadband filters, the ''wide-V'' F606W and ''blue'' F438W filters (Li at al. 2013). The twelve images obtained with the F606W filter were analyzed using our well-proven technique of fitting a parametric model of the expected surface brightness to the observed images (e.g., Lamy et al. 2006). The model consists of an unresolved point source and a coma specified by a power law, both convolved with the point spread function of the telescope. The nucleus is basically undetected, which imposes an upper limit of its radius of ∼0.3 km. However, the analysis is complicated by the so-called ''breathing'' of the WFC3 camera, an uncontrolled slight defocus which distorts the PSF. We investigated this question in detail and considered various cases of defocus. We will report on this effort and the resulting robust upper limit which we can put on the size of the nucleus of C/ISON. Title: VizieR Online Data Catalog: Reflectance spectra of 12 Trojans and Hildas (Marsset+, 2014) Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan, M.; Lamy, P.; Binzel, R. P. Bibcode: 2014yCat..35689007M Altcode: We present 17 reflectance spectra of 12 high albedo (pv>0.14) Trojans (8 objects) and Hildas (4 objects) obtained with the ESO/VLT Echelle spectrograph X-SHOOTER in the 0.3-2.2um spectral range (14 spectra) and with the NASA/IRTF spectrograph SpeX in the 0.8-2.5um spectral range (3 spectra). X-SHOOTER spectra were normalized to unity at 0.55um and SpeX spectra were normalized to unity at 2.2um . The spectra presented in this work were collected between April and December 2013.

(18 data files). Title: Early results on 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS Authors: Sierks, H.; Tubiana, C.; Snodgrass, C.; Agarwal, J.; Güttler, C.; Oklay, N.; Vincent, J.; Küppers, M.; Barbieri, C.; Lamy, P.; Rickman, H.; Rodrigo, R.; Koschny, D.; Hviid, S.; Mottola, S.; Osiris Team Bibcode: 2014acm..conf..495S Altcode: 67P/Churyumov-Gerasimenko (67P) is the target comet of the ESA Rosetta mission. Launched in 2004, the Rosetta spacecraft woke up on the 20th of January 2014. After 36 months of deep space hibernation, Rosetta is now traveling to rendezvous with the comet at 4.1 au from the Sun, and it will follow 67P along its orbit, investigating how the comet changes and evolves while approaching the Sun.

The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS (Keller et al., 2007) is the scientific imaging system onboard Rosetta. It comprises the Narrow Angle Camera (NAC) with wavelength range 250--1000 nm and the Wide Angle Camera (WAC) with wavelength range 240--720 nm. The NAC (FOV = 2.20×2.22 deg) is a system with high spatial resolution that allows an initial detection of the nucleus, studies its structure and rotation from relatively great distances, investigates the mineralogy of the surface, and studies the dust ejection processes. The WAC has much lower spatial resolution but, accordingly, a much wider field of view (about 11.35×12.11 deg). This allows observations of the 3-dimensional flow field of dust and gas near the nucleus and, in addition, provides a synoptic view of the whole nucleus. In summary, the WAC would provide long-term monitoring of the entire nucleus from close distances, while the NAC studies the details. The two camera units have been designed as a complementary pair, which, on one hand, addresses the study of the nucleus surface, and on the other hand, investigates the dynamics of the sublimation process.

After commissioning in March 2014, OSIRIS took first images of comet 67P and its dust environment. Ground-based observations performed in 2007/08 when 67P was in the same orbital arc as it will be in March/April 2014, show that the comet was already active at 4.3 au inbound and that its behavior was repetitive during the last three apparitions (Snodgrass et al. 2013). We therefore expect to detect early comet activity by OSIRIS in March/April 2014. At this time, Rosetta will be at about 4 million kilometers from the comet and 67P will still be unresolved.

We present results about the early cometary activity based on OSIRIS images. Orange-filter images (central wavelength 649.2 nm) will be used to determine the dust environment of 67P, since this wavelength range is quite free from gas emission lines.

Moreover, a series of lightcurves will be taken to compare with the existing ones and look for possible changes in the rotational period due to its last perihelion passage. Title: Investigation of the interior of primordial asteroids and the origin of the Earth's water: The INSIDER space mission Authors: Vernazza, P.; Lamy, P. Bibcode: 2014acm..conf..559V Altcode: Today's asteroid belt may not only be populated by objects that formed in situ, typically between 2.2 and 3.3 au, but also by bodies that formed over a very large range of heliocentric distances. It is currently proposed that both the early (<5 Myrs after Solar System formation) and late (>700 Myrs after Solar System formation) dynamical evolution of the Solar System was governed by giant planet migrations that led to the insertion of inner (1--3 au) as well as outer (4--13 au) small bodies in the asteroid belt. Taken altogether, the current dynamical models are able to explain many striking features of the asteroid belt including i) its incredible compositional diversity deduced mainly from spectroscopic observations and meteorites measurements, and ii) the evidence of radial mixing experienced by the various asteroid classes (e.g., S-, C-types) after their formation. In a broad stroke, the idea that the asteroid belt is a condensed version of the primordial Solar System is progressively emerging. The asteroid belt therefore presents the double advantage of being easily accessible and of offering crucial tests for the formation models of the Solar System by exploring the building blocks predicted by models of i) the telluric planets, ii) the giant planet cores, iii) the giant planets' satellites, and iv) outer small bodies such TNOs and comets. It also appears as an ideal place to search for the origin of Earth's water.

Up to now, only a few asteroid classes (e.g., several S-types) have been visited by spacecraft and the focus of these in situ measurements has been mainly to give a geological context to ground based observations as well as strengthen/validate their interpretation. Most of the tantalizing discoveries of asteroid missions have been realized via images of the objects surfaces. Time has come for asteroid space science to reach a new milestone by extending the reconnaissance of the Belt's diversity and addressing new science questions.

The scientific objectives of the INSIDER mission, to be proposed in response to the 2014 ESA call for an M-class mission, require the exploration of diverse primordial asteroids --- possibly the smallest surviving protoplanets of our Solar System --- in order to constrain the earliest stages of planetesimal formation thus avoiding the effect of destructive collisions, which produce extensively processed rubble piles. Our science objectives that justify in situ measurements in the context of an M-class mission and that are expected to lead to significant breakthroughs include:

- The exploration of the diversity of the asteroid belt

- The first investigation of the internal structure of asteroids

- The origin of water on Earth

The proposed mission scenario consists in i) successive rendez-vous followed by orbit insertion of two and possibly three large (D>100 km) objects, ii) one or two small landing modules (MASCOT type) to perform cosmochemical measurements (D/H ratio, O isotopes). The potential targets would include 24 Themis and 10 Hygiea.

Meeting our science objectives requires instruments (such as radar, seismometers to be dropped to the surface, magnetometer, high resolution laser-desorption-ionization mass spectrometer to analyse the surface samples) not flown so far during past asteroids missions along with the traditional powerhouses, such as cameras and spectrometers. Title: Preliminary solution for the shape and rotational state of the nucleus of comet 67P/Churyumov-Gerasimenko Authors: Lamy, P.; Jorda, L.; Kaasalainen, M.; Hviid, S.; Faury, G.; Toth, I.; Groussin, O. Bibcode: 2014acm..conf..303L Altcode: In preparation of ESA's ROSETTA mission to comet 67P/Churyumov-Gerasimenko, solutions for the shape and rotational state of its nucleus have been published based on observation with the Hubble and Spitzer space telescopes as well as ground-based observations (Lamy et al. 2006, 2007, 2008; Lowry et al. 2012). Following the wake-up of the Rosetta spacecraft in January 2014 and the successful commissioning of the OSIRIS camera system in March, a first lightcurve of the inactive nucleus has been obtained on 23 March 2014 with the OSIRIS Narrow Angle Camera (NAC). Further lightcurves will be acquired in the forthcoming months. We will present an updated solution for the shape and rotational state based on these data sets as of end of June 2014 combined with past Hubble and Spitzer space telescopes as well as ground-based observations using the technique of lightcurve inversion. Title: Constraints on the subsurface structure and density of the nucleus of Comet 67P/Churyumov-Gerasimenko from radar observations Authors: Lamy, Philippe; Kamoun, Paul; Toth, Imre; Herique, Alain Bibcode: 2014EGUGA..16.6993L Altcode: We performed an in-depth analysis of the observations carried with the radar system of the Arecibo Observatory in November 1982 when comet 67P/Churyumov-Gerasimenko had a close encounter with Earth at a geocentric distance of 0.4 AU taking into account our present knowledge of the properties of its nucleus (size, rotational state). In the absence of a detectable radar echo, we determined a maximum radar cross section of 0.7 km2 leading to a maximum radar albedo of 0.05. This low albedo probably results from a combination of a low radar reflectivity material and a lightly packed upper layer of the nucleus with substantial roughness (rms slope of ≡55°), consistent with its low thermal inertia. Based on radar observations of other cometary nuclei and asteroids, it is unlikely that the albedo can be lower than 0.04 so that we were able to constrain the dielectric permittivity of the subsurface layer to a narrow range of 1.9 to 2.1. Laboratory measurements and our modeling of mixtures of ice and dust led to a porosity in the range of approximately 55 to 65% and a density in the range of ≡600 to ≡1000 kg m-3 for the top ≡2.5 m layer of the nucleus. This would be the bulk density range for an homogeneous nucleus and would place the success of the landing at risk but an inhomogeneous nucleus with an overall density below this range remains a possibility. Title: Radiation forces on small particles in the Solar System: A re-consideration Authors: Burns, Joseph A.; Lamy, Philippe L.; Soter, Steven Bibcode: 2014Icar..232..263B Altcode: We respond to Klačka et al. (Klačka, J., Petržala, J., Pástor, P., Kómar, L. [2014]. Icarus, this issue, http://dx.doi.org/10.1016/j.icarus.2012.06.044.), who have criticized many previous derivations of the acceleration experienced by a spherical interplanetary particle owing to the Sun’s radiation. Much of their criticism arises from differences in semantics and notation as well as effects that are unimportant at Solar System speeds. Accordingly, in the appropriate limiting cases, most published expressions for the radiation forces, such as that found in Burns et al. (Burns, J.A., Lamy, P.L., Soter, S. [1979]. Icarus 40 1-48), are correct and duplicate the results of Klačka et al. (Klačka, J., Petržala, J., Pástor, P., Kómar, L. [2014]. Icarus, this issue, http://dx.doi.org/10.1016/j.icarus.2012.06.044). Title: Low and high albedo jovian Trojans and Hildas: a similar or different origin? Authors: Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan, M.; Lamy, P.; Binzel, R. P. Bibcode: 2014EPSC....9...54M Altcode: Jupiter Trojans and Hilda asteroids are small primitive bodies located near or beyond the snow line, around respectively the L4 and L5 Lagrange points of Jupiter at ~5.2AU from the sun (Trojans) and in the 2:3 mean-motion resonance with Jupiter near 3.9AU (Hildas). Our current understanding of the early dynamical evolution of the Solar System tells us that they probably originated from the primordial transneptunian region from which they were captured in their current location (Nice model; [6, 5]). In addition, this region not only comprised planetesimals formed beyond the snow line (D-, T- and X-type asteroids) but also a minor population of rocky interlopers (e.g., A-, S-, V-type asteroids) that migrated outward during the very early evolutionary phases of the Solar System 5 to 7My after its formation (Grand Tack model; [8]). The recent discovery by WISE [2, 3] and Spitzer [1] of high albedo (pv ≥0.15) asteroids within jovian Trojans and Hildas opened the possibility of an observational evidence for the presence of a small fraction (~2 %) of such interlopers among these two low albedo (pv ∼0.07) populations. Here, we report the very first spectroscopic characterization of a sample of high albedo tTrojans and Hildas obtained with X-SHOOTER and SpeX in the visible and / or nearinfrared ranges. This study allows us to investigate the origin of these high albedo objects and to provide an estimate of the contamination rate of jovian Trojans and Hilda asteroids by objects that do not belong to the C / T / D-type complex (e.g., A-, S-, V-type asteroids), thus constraining migration models [7, 4, 6, 5, 8]. The results of this study will be presented in details. Title: The Interaction Between Coronal Mass Ejections and Streamers: A Statistical View over 15 Years (1996 - 2010) Authors: Floyd, O.; Lamy, P.; Llebaria, A. Bibcode: 2014SoPh..289.1313F Altcode: We report on the statistical analysis of the interaction between coronal mass ejections (CMEs) and streamers based on 15 years (from 1996 to 2010 inclusive) of observation of the solar corona with the LASCO-C2 coronagraph. We used synoptic maps and improved the method of analysis of past investigations by implementing an automatic detection of both CMEs and streamers. We identified five categories of interaction based on photometric and geometric variations between the pre- and post-CME streamers: "brightening", "dimming", "emergence", "disappearance", and "deviation". A sixth category, "no change", included all cases where none of the above variations is observed. A "global set" of 21 242 CMEs was considered as well as a subset of the 10 % brightest CMEs (denoted "top-ten") and three typical periods of solar activity: minimum, intermediate, and maximum. We found that about half of the global population of CMEs are not associated with streamers, whereas 93 % of the 10 % brightest CMEs are associated. When there is a CME-streamer association, approximately 95 % of the streamers experience a change, either geometric or radiometric. The "no change" category therefore amounts to approximately 5 %, but this percentage varies from 1 - 2 % during minimum to 7 - 8 % during intermediate periods of activity; values of 3 - 5 % are recorded during maximum. Emergences and disappearances of streamers are not dominant processes; they constitute 16 - 17 % of the global set and 23 % (emergence) and 28 % (disappearance) of the "top-ten" set. Streamer deviations are observed for 57 % and 70 % of, respectively, the global set and "top-ten" CMEs. The cases of dimming and brightening are roughly equally present and each case constitutes approximately 30 - 35 % of either set, global or "top-ten". Title: Automated Processing of LASCO Coronal Images: Spurious Point-Source-Filtering and Missing-Blocks Correction Authors: Pagot, E.; Lamy, P.; Llebaria, A.; Boclet, B. Bibcode: 2014SoPh..289.1433P Altcode: We report on automated procedures for correcting the images of the LASCO coronagraph for i) spurious quasi-point-sources such as the impacts of cosmic rays, stars, and planets, and ii) the absence of signal due to transmission errors or dropouts, which results in blocks of missing information in the images. Correcting for these undesirable artifacts is mandatory for all quantitative works on the solar corona that require data inversion and/or long series of images, for instance. The nonlinear filtering of spike noise or point-like objects is based on mathematical morphology and implements the procedure opening by morphological reconstruction. However, a simple opening filter is applied whenever the fractional area of corrupted pixels exceeds 50 % of the original image. We describe different strategies for reconstructing the missing information blocks. In general, it is possible to implement the method of averaged neighbors using the two images obtained immediately before and after the corrupted image. For the other cases, and in particular when missing blocks overlapped in three images, we developed an original procedure of weighted interpolation along radial profiles from the center of the Sun that intercept the missing block(s). This procedure is also adequate for the saturated images of bright planets (such as Venus) that bleed along the neighboring pixels. Missing blocks in polarized images may generally be reconstructed using the associated unpolarized image of the same format. But in the case of overlapping missing blocks, we implemented our procedure of weighted interpolation. All tests performed on numerous LASCO-C2 images at various periods of solar activity (i.e. varying complexity of the structure of the corona) demonstrate the excellent performance of these new procedures, with results vastly superior to the methods implemented so far in the pipeline-processing of the LASCO images. Title: Global and Spatially Resolved Photometric Properties of the Nucleus of Comet 67P/C-G from OSIRIS Images Authors: Lamy, P. Bibcode: 2014EPSC....9..233L Altcode: Following the successful wake-up of the ROSETTA spacecraft on 20 January 2014, the OSIRIS imaging system was fully re-commissioned at the end of March 2014 confirming its initial excellent performances. The OSIRIS instrument includes two cameras: the Narrow Angle Camera (NAC) and the Wide Angle Camera (WAC) with respective fieldsofview of 2.2° and 12°, both equipped with 2K by 2K CCD detectors and dual filter wheels. The NAC filters allow a spectral coverage of 270 to 990 nm tailored to the investigation of the mineralogical composition of the nucleus of comet P/Churyumov- Gerasimenko whereas those of the WAC (245-632 nm) aim at characterizing its coma [1]. The NAC has already secured a set of four complete light curves of the nucleus of 67P/C-G between 3 March and 24 April 2014 with a primary purpose of characterizing its rotational state. A preliminary spin period of 12.4 hours has been obtained, similar to its very first determination from a light curve obtained in 2003 with the Hubble space telescope [2]. The NAC and WAC will be recalibrated in the forthcoming weeks using the same stellar calibrators VEGA and the solar analog 16 Cyg B as for past inflight calibration campaigns in support of the flybys of asteroids Steins and Lutetia. This will allow comparing the pre- and post-hibernation performances of the cameras and correct the quantum efficiency response of the two CCD and the throughput for all channels (i.e., filters) if required. The accurate photometric analysis of the images requires utmost care due to several instrumental problems, the most severe and complex to handle being the presence of optical ghosts which result from multiple reflections on the two filters inserted in the optical beam and on the thick window which protects the CCD detector from cosmic ray impacts. These ghosts prominently appear as either slightly defocused images offset from the primary images or large round or elliptical halos. We will first present results on the global photometric properties of the nucleus of comet 67P/C-G, albedo, phase function and spectral reflectivity and compare with previous results obtained with the Hubble and Spitzer space telescopes [2, 3, 4]. Then observations during the approach and first bound orbits in July-August 2014 will allow mapping the surface of the nucleus with OSIRIS at a scale of up to 1 meter per pixel. The images will be used to reconstruct the 3D surface of the nucleus at highresolution allowing separating true photometric variations from topographic effects. We will present results on the spatially resolved photometric properties of the nucleus based on a novel method developed in the space of the facets representing the three-dimensional shape of the body. This method successfully implemented in the cases of the nucleus of comet 9P/Tempel 2 and of asteroid (2867) Steins [5] has the advantage of automatically tracking the same local surface element on a series of images. The analysis will then proceed with the determination of the global Hapke and other standard photometric parameters as well as their two-dimensional variations across the surface. This allows defining, in the body-fixed reference frame, ``high residual regions'' (HRRs) which correspond to significant relative differences between the observed and modeled photometric parameters such as the singlescattering albedo (SSA), the mean roughness slope angle, and the reflectivity gradient. Of particular interest will be the search for ice patches and possible mineralogical differences resulting from the past activity of the comet. Title: First close view at comet 67P/ Churyumov-Gerasimenko by Rosetta/OSIRIS Authors: Sierks, H.; Barbieri, C.; Lamy, P.; Rickman, H.; Rodrigo, R.; Koschny, D.; Keller, H. U.; Jorda, L.; Fornasier, S.; Massironi, M.; Vincent, J. -B.; Snodgrass, C.; Tubiana, C.; Agarwal, J.; Güttler, C.; Oklay, N. Bibcode: 2014EPSC....9..518S Altcode: ESA's Rosetta mission arrived at target comet 67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. It comprises a Narrow Angle Camera (NAC) for nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field coma investigations. We present the first scientific results from comet detection, activity wake-up, to the high resolution images of surface and topographical features. Title: Global Shape and Topography of the Nucleus of Comet 67P/C-G from ROSETTA/OSIRIS Images Authors: Jorda, L.; Gaskell, R.; Hviid, S.; Capanna, C.; Groussin, O.; Gutierrez, P.; Lamy, P.; Scholten, F.; Preusker, F.; Kaasalainen, M.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Mottola, S.; Sierks, H.; Snodgrass, C.; Thomas, N.; Toth, I.; Vincent, J. -B. Bibcode: 2014EPSC....9..665J Altcode: The ROSETTA spacecraft will approach the nucleus of comet P/Churyumov-Gerasimenko in early August 2014 after a successful wake-up on January 20, 2014. The OSIRIS instrument is a set of two cameras aboard ROSETTA: the Narrow Angle Camera and the Wide Angle Camera which have fields-of-view of 2.2° and about 12° respectively. Both cameras are equipped with a 2K by 2K CCD detector. The two cameras have been successfully re-commissioned at the end of March 2014. Observations during the approach and first bound orbits in July-August 2014 will allow to map the surface of the nucleus with OSIRIS at a scale as small as 1 m/pixel. The images will be used to reconstruct the 3D global topography of the nucleus at high-resolution with a combination of two advanced reconstruction techniques: stereophotogrammetry and stereophotoclinometry. The reconstructed global shape will be used to determine the bulk density of the nucleus with an accuracy of a few percent and to localize and quantitatively characterize the main topographic features at its surface. It will also allow us to identify the different types of terrains present at the surface of the nucleus. We will describe and discuss the bulk properties of the nucleus (bulk shape, density and moments of inertia) against those of other comets observed from the ground or by previous space probes. We will also identify the main topographic features from a combined analysis of images and global digital terrain models and compare them with those identified at the surface of comets P/Borrelly, P/Wild 2 and P/Tempel 1 by previous space probes. Finally, we will propose a preliminary interpretation for the processes involved in their formation. Title: Early Grain Detections in the Coma of Comet 67P/Churyumov-Gerasimenko Authors: Rotundi, A.; Della Corte, V.; Fulle, M.; Accolla, M.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Sordini, R.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Crifo, J. C.; Bussoletti, E.; Esposito, F.; Green, S.; Grün, E.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. -M.; Rietmeijer, F. J. M.; Rodrigo, R.; Weissman, P. R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A.; Altobelli, N. Bibcode: 2014EPSC....9..868R Altcode: The GIADA (Grain Impact Analyser and Dust Accumulator) instrument aboard the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko (67P/C-G) measures dust grain number, mass, momentum and velocity [1,2]. GIADA is composed of three sub-systems: the Grain Detection System (GDS), detecting dust grains based on light scattering; an Impact Sensor (IS), providing momentum measurements from the impact on a plate connected to five piezoelectric sensors; and the MicroBalances System (MBS), made up of five Quartz Crystal Microbalances (QCMs), to yield cumulative deposited dust mass through the shift in resonance frequency. Title: Giada: its Status after the Rosetta Cruise Phase and On-Ground Activity in Support of the Encounter with Comet 67P/CHURYUMOV-GERASIMENKO Authors: Della Corte, V.; Rotundi, A.; Accolla, M.; Sordini, R.; Palumbo, P.; Colangeli, L.; Lopez–Moreno, J. J.; Rodriguez, J.; Rietmeijer, F. J. M.; Ferrari, M.; Lucarelli, F.; Mazzotta Epifani, E.; Ivanovski, S.; Aronica, A.; Cosi, M.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Fulle, M.; Green, S. F.; Gruen, E.; Herranz, M. L.; Jeronimo, J. M.; Lamy, P.; Lopez Jimenez, A.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Palomba, E.; Perrin, J. M.; Rodrigo, R.; Weissman, P.; Zakharov, V.; Zarnecki, J. C. Bibcode: 2014JAI.....350011D Altcode: GIADA (Grain Impact Analyser and Dust Accumulator) on-board the Rosetta mission to comet 67P/Churyumov-Gerasimenko was designed to study the physical and dynamical properties of dust particles ejected by the comet during the encounter. In this paper we report the results of the analysis of data collected by GIADA during the past seven years of the cruise phase. During this period the GIADA detection subsystems were switched on for periodic in-flight payload checkouts to monitor their state-of-health including potential changes in its performance that could affect its data collection. Only slight variations in sensitivity and dynamical range were identified that will not affect the GIADA measurement capability during the Rosetta comet encounter and rendezvous phase. The GIADA microbalance system detected the presence of low-volatility material over a period of about 169 days when the GIADA cover remained partially opened. It is highly probable that this material originated from the spacecraft itself, as a spacecraft's outgassing was observed by the ROSINA mass spectrometer (on-board Rosetta) during the cruise phase.

The identification of the low-volatility mass deposited on the microbalances as self-contamination will allow us to evaluate the mass rate background to be subtracted from the GIADA science data. These results obtained from GIADA cruise data analysis coupled with laboratory calibration data obtained from measurements using the GIADA spare model for selected cometary dust analogs will be the basis for the interpretation of the GIADA scientific data. Title: Possible measurements of the magnetic field in eruptive prominences using the PROBA-3 coronagraph Authors: Serge, Koutchmy; Zhukov, Andrei; Dolla, Laurent; Heinzel, Petr; Lamy, Philippe; Bazin, Cyrille; Bommier, Veronique; Faurobert, Marianne Bibcode: 2014cosp...40E2971S Altcode: The PROBA-3 mission will fly a spacecraft put in the shadow of a precisely occulting sister satellite orbiting “in formation” at a distance of 150 m in front of it to make artificial total eclipses. The region right above the solar limb will be studied for the first time over a coronal background not polluted by any spurious light. Although the priority will be the high-resolution fast imaging of the dynamic white-light corona, the use of a narrow filter centered on a low excitation D3 line of He I, is planned for imaging prominences. Adding the linear polarization analysis would permit the measurements of the magnetic field using the Hanle effect. We evaluate the possibility offered during the eruptive phase of a CME with prominence material inserted inside, for studying the associated magnetic field changes related to both the heating process and the ejection of material. The background highly polarized K-corona is taken into account. Sequences of quasi- simultaneous white-light processed images at high resolution are an additional feature of great interest for interpreting the overall magnetic structure. Title: Observation of the prominence cavity region using slitless eclipse flash spectra and space borne EUV filtergrams Authors: Bazin, Cyrille; Koutchmy, Serge; Lamy, Philippe; Tavabi, Ehsan Bibcode: 2014IAUS..300..151B Altcode: We used total solar eclipse free of parasitic light for studying the prominence to corona interface, and the corresponding cavity in the context of the coronal physics. We analysed the visible continuum between the prominences to directly look at the electron density. We demonstrate some enhanced heating in the cavity region. Some similarities with the interface regions are shown: the photosphere to the chromosphere and the prominence to the corona interface. The optically thin neutral Helium at 4713 Å and the singly ionized Helium 4686 Å Paschen α lines are considered. We summed 80 slitless visible eclipse flash spectra that we compare with simultaneously obtained EUV SWAP/Proba2 174 Å images of ESA and AIA/SDO 171Å 193 Å 304 Å and 131 Å filtergrams. Intensity profiles in a radial direction are studied. We deduce the variation of the intensity ratio I(He I 4713) / I(He II 4686). Discussion: the temperature rises at the edge of the prominences. We evaluate for the first time with spectrophotometric accuracy the continuum modulations in prominence spectra. W-L intensity deficits are observed near the prominence boundaries in both eclipse spectra and in EUV images, confirming that the prominence -cavity regions correspond to a relative depression of plasma density of the surrounding corona. Conclusion: we demonstrate some enhanced heating occurring in these regions assuming hydrostatic equilibrium. Title: Comparing the solar minima of cycles 22/23 and 23/24: The view from LASCO white light coronal images Authors: Lamy, P.; Barlyaeva, T.; Llebaria, A.; Floyd, O. Bibcode: 2014JGRA..119...47L Altcode: The Large Angle and Spectrometric Coronagraph LASCO-C2 aboard SOHO has now completed 17 years (1996-2012) of quasi-continuous white-light imaging of the corona from 2.2 to 6.5 solar radii, thus allowing an unprecedented view of its evolution over a solar cycle and a half including the minima of solar cycles 22/23 and 23/24. The corrected and calibrated polarization sequences produce images of the radiance (B), the polarized radiance (pB), and the electron density Ne of the K corona, and, in turn, of their synoptic maps. Their temporal variations are quantified by integration first globally, then in the north and south hemispheres, and finally, in sectors of 30° latitudinal extent centered along the equatorial and polar directions. The global radiance of the K corona follows well the solar activity as described by the sunspot number and the radio flux and was 24% fainter during the minimum of solar cycle 23/24 than during that of cycle 22/23. However, the two hemispheres experienced different reductions, 17% for the north one and 29% for the south one. The equatorial sector suffered a drastic reduction of 44%, in remarkable agreement with the in situ measurements of Wind and ACE at 1 AU, whereas the north and south polar sectors did not experience much variation. Cycle 23 is estimated to have lasted 12 years and 3 months. Maximum conditions have been reached in the northern region, whereas the southern region is still lagging. Finally, the rate of coronal mass ejections follows well the solar activity. Title: Coronal mass ejections (CMEs) during the ascending phase of cycle 24 Authors: Lamy, Philippe; Floyd, Olivier; Barlyaeva, Tatiana Bibcode: 2014cosp...40E1745L Altcode: The Artemis-II catalog of coronal mass ejections (Floyd et al., Solar Phys 2013) lists their properties (date and time of appearance, position angle, angular width, mass and kinetic energy) based on detection and measurements performed on synoptic maps constructed from the calibrated SOHO/LASCO-C2 images of the K-corona from January 1996 to December 2010. It has now been extended to 2013 allowing an analysis of their properties during the ascending phase of solar cycle 24 and a comparison with the previous cycle. In addition, these properties are compared to three indices of solar activity, the international sunspot number (SSN), the sunspot area (SSA) and the radio flux at 10.7~cm (F10.7), either globally or separately in the North and South hemispheres in the case of the first two proxies. The monthly averaged number and mass of CMEs exhibit a time shift of 12 years and 9 months between the ascending phases of cycles 23 and 24, in agreement with the anomanously long 23/24 minimum. Both are significantly less during the present cycle than the previous one in agreement with a weak cycle 24. There are strong linear correlations of the monthly averaged number and mass of CMEs with both SSA and F10.7 but less so with SSN. However two significantly different regimes are observed for the whole cycle 23 and for the ascending phase of cycle 24 implying a comparatively larger CME activity after 2009 with respect to both SSA and F10.7. The analysis in separate hemispheres reveals a contrasted situation with significantly different rates and different linear correlations with the proxies. Possible origins of these differences will be discussed. Title: The WATCHER Heliospheric and Spaceweather Mission Authors: Lamy, Philippe; Xia, Lidong Bibcode: 2014cosp...40E1746L Altcode: Coronal mass ejections (CMEs) and their interplanetary counterparts ICMEs and corotating interaction region (CIRs) are the main disturbances of solar origin that impact Earth’s magnetosphere resulting in geomagnetic storms. In addition, CMEs can drive shock starting very close to the Sun than can therefore hit the Earth contrary to CIRs shocks which form beyond 1 AU. We present the WATCHER mission with the dual purpose of providing key scientific data on the two primary sources of spaceweather and directly serving the very purposes of spaceweather forecast. This will be achieved by placing a three-axis stabilized satellite on the Earth-L5 (Lagrangian point) arc at an offset angle of 30-60° from Earth and an adequate payload combining remote and in situ capabilities. From this ideal position and overlooking the region extending from the Sun to 1 AU, it will act as a CME/ICME and CIR watcher and sample the local solar wind. WATCHER will be able to provide advanced warning of solar eruptions, CMEs, CIRs and shocks well before their detection by Earth-based or L1 space-based observatories. WATCHER mission will address the following science objectives. 1. Determine the magnetic conditions in the Sun interior and at its surface precursors of interplanetary disturbances terrestrial observations. 2. Detect and track interplanetary disturbances (CMEs/ICMEs and CIRs) from their sources to Earth and determine their magnetic structure. 3. Determine where shocks form and how they evolve. 4. Understand the role of interactions affecting the propagation of disturbances (especially CMEs) and how they affect their arrival time at Earth. 5. Study the Sun-Earth relations as a global, complex system. The WATCHER S/C will carry the following suite of instruments. A Magnetic and Doppler Imager will i) measure the photospheric magnetic field and acquire magnetograms allowing observing the source regions of CMEs before they rotate to Earth view, ii) measure velocity fields allowing performing stereo heliosismology in combination with other observatories probing the convection zone where the Sun acquires its magnetism. A combined disk imager and inner coronal imager in EUV. EUV images offer several diagnostics of eruptions, indicate the solar source location of CMEs, and map coronal holes. They will provide advanced warning of active regions that would be rotating on to the disk to face Earth and of HSS and CIRs. A white light coronagraph will then observe, characterize and track CMEs up to about 20 solar radii (Rs). A couple of heliospheric imagers will pursue the tracking to 1 AU. A Solar Wind Plasma Instrument and a magnetometer will make in-situ measurements of the solar wind providing information on CIRs that would arrive at Earth about 4 days after being detected in situ. Possible additional candidates, depending on S/C resources are a low-frequency radiotelescope with spectral coverage of 2-100 Rs to identify CMEs driving shocks and an energetic particle detector to address the unsolved issue of flare and CME-shock contributions to large SEP events. Title: The Characteristics and Evolution of the Dust Coma of Comet C/2012 S1 (ISON) Authors: Li, Jian-Yang; Kelley, M. S.; Knight, M. M.; Farnham, T.; Weaver, H. A.; A'Hearn, M. F.; Mutchler, M. J.; Kolokolova, L.; Lamy, P. L.; Toth, I.; Xia, K. Bibcode: 2014AAS...22321806L Altcode: C/2012 S1 (ISON) is a dynamically new comet with a sungrazing perihelion only 1.7 solar radii from the Sun's surface, which makes it unique among the known comets. The discovery of C/ISON in September 2012 at a heliocentric distance of ~6 AU is more than one year before its perihelion in November 2013, allowing a detailed characterization as the comet moves from the frigid conditions of the outer solar system to extreme heating during its close passage near the Sun. As part of an international observing campaign, the Hubble Space Telescope (HST) imaged the comet in multiple epochs from April to October 2013 pre-perihelion to characterize its dust coma at 4.15, 3.78, and 1.50 AU. We report on our analysis of these HST images, including the dust production rate, the dust coma colors and morphology, and the rotation pole of the nucleus. The first two epochs of observations showed that C/ISON displays a color variations in its dust coma within ~5000 km from the nucleus that is best explained by the existence and sublimation of water ice grains. The pole orientation, as measured from the sunward jet, suggests a high obliquity, and indicates that the nucleus of C/ISON always faces the Sun with one hemisphere until about a week before the perihelion. We will use the observations in October to search for any evolutionary changes in the coma, and to refine the determination of the rotation pole. Title: Physical properties of craters on the Achaia region of asteroid (21) Lutetia Authors: Auger, A.; Bouley, S.; Jorda, L.; Groussin, O.; Baratoux, D.; Capanna, C.; Lamy, P. L. Bibcode: 2013AGUFM.P23A1755A Altcode: The Rosetta spacecraft flew by the main-belt asteroid (21) Lutetia on 10 July 2010. Images of the surface were acquired with the Narrow Angle Camera, from which Digital Terrain Models (DTM) of the surface were produced. These DTMs give access to the topography to study the physical properties of the craters of the asteroid. In this study, we focus on their depth-to-diameter ratio (d/D) to study their degradation. The d/D ratios are are derived from the DTM of Jorda et al. (2012), based on the method of Gaskell et al. (2008), which offers the best compromise between spatial resolution and the accuracy of the topographic reconstruction. Our values differ notably from previous studies (Vincent et al., 2012; Thomas et al., 2012). The discrepancy has been found to result from the fact that the local slope of the terrains on which the craters formed is ignored in these studies, whereas we rigorously takes this into account in our calculations. As a consequence, we find that d/D values for the fresh craters of Lutetia are consistent with the values found on other asteroids of similar size (within on order of magnitude) like (243) Ida or (951) Gaspra (Carr et al., 1994; Sullivan et al., 1996). The Achaia region may be divided into three units based on geomorphological analysis. A comparison of the crater density on the three units suggests two different ages, the youngest part corresponding to the Nicaea crater unit. Interestingly, the mean d/D values of the three units are different. The craters of these units were therefore differently affected by geological events (e.g., essentially impact and associated phenomena such as seismic shaking or ejecta blanketing) that occurred in the past history of Lutetia. Some of these events must be recent since several lineaments intersect most craters of one of the unit. Ejecta deposits have been previously noted on one part of Achaia and provide a good explanation for the low d/D values on this unit. Moreover, we suggest that tectonic activity may have been responsible for the erasure of small craters. The link between these events and the impacts at the origin of the North Polar Crater Cluster of Lutetia will be discussed. Title: Pre-perihelion characterization of Comet C/2012 S1 (ISON) Authors: Li, J.; Kelley, M. S.; Farnham, T. L.; A'Hearn, M. F.; Knight, M. M.; Weaver, H. A.; Mutchler, M.; Lamy, P. L.; Toth, I. Bibcode: 2013AGUFM.P24A..02L Altcode: Comet C/2012 S1 (ISON) is a dynamically new comet on a sungrazing orbit. As such, C/ISON represents a unique opportunity to study both the cosmic-ray-irradiated surface, produced during the comet's long residence in the Oort cloud, and much deeper layers in the nucleus, exposed when the comet passes within 2 solar radii of the Sun at perihelion. During the first phase of our investigation, we collected broadband images of C/ISON on April 10, 2012 at a heliocentric distance of 4.15 AU, using the Hubble Space Telescope WFC3/UVIS. We used the F606W and F438W filters in three HST orbits covering a total span of ~19 hrs. The comet shows a well delineated coma in the sunward direction extending about 2" from the nucleus, and a dust tail at least 25" long. The coma has an average red color of 5%/0.1 micron within 1.6" from the nucleus, becoming redder towards the tail. Both the color and the size of the coma in the sunward direction are consistent with outflow of micron sized dust. Broadband photometry yielded Afρ of 1376 cm at 589 nm, and 1281 cm at 433 nm, measured with a 1.6" radius aperture. The total brightness of the comet within a 0.12" radius aperture remained unchanged within 0.03 mag for the entire duration of the observations. A well defined sunward jet is visible after removing the 1/ρ brightness distribution. The jet is centered at position angle 290 deg (E of Celestial N), with a cone angle of 45 deg, a projected length of 1.6", and a slight curvature towards the north near the end. No temporal change in the morphology is observed, suggesting the jet is circumpolar. Under this assumption, the jet's apparent position constrains the rotational pole to lie within 30 deg of (RA, Dec) = (330, 0), and an obliquity of 50-80 deg. Preliminary analysis using a coma-nucleus separation technique suggests a nuclear radius less than 2 km. The survival of such a small nucleus during its perihelion at 2.7 solar radii is certainly questionable. Title: Characterizing the Dust Coma of Comet C/2012 S1 (ISON) at 4.15 AU from the Sun Authors: Li, Jian-Yang; Kelley, Michael S. P.; Knight, Matthew M.; Farnham, Tony L.; Weaver, Harold A.; A'Hearn, Michael F.; Mutchler, Max J.; Kolokolova, Ludmilla; Lamy, Philippe; Toth, Imre Bibcode: 2013ApJ...779L...3L Altcode: 2013arXiv1311.0826L We report results from broadband visible images of comet C/2012 S1 (ISON) obtained with the Hubble Space Telescope Wide Field Camera 3 on 2013 April 10. C/ISON's coma brightness follows a 1/ρ (where ρ is the projected distance from the nucleus) profile out to 5000 km, consistent with a constant speed dust outflow model. The turnaround distance in the sunward direction suggests that the dust coma is composed of sub-micron-sized particles emitted at speeds of tens of m s-1. A(θ)fρ, which is commonly used to characterize the dust production rate, was 1340 and 1240 cm in the F606W and F438W filters, respectively, in apertures <1.''6 in radius. The dust colors are slightly redder than solar, with a slope of 5.0% ± 0.2% per 100 nm, increasing to >10% per 100 nm 10,000 km down the tail. The colors are similar to those of comet C/1995 O1 (Hale-Bopp) and other long-period comets, but somewhat bluer than typical values for short-period comets. The spatial color variations are also reminiscent of C/Hale-Bopp. A sunward jet is visible in enhanced images, curving to the north and then tailward in the outer coma. The 1.''6 long jet is centered at a position angle of 291°, with an opening angle of ~45°. The jet morphology remains unchanged over 19 hr of our observations, suggesting that it is near the rotational pole of the nucleus, and implying that the pole points to within 30° of (R.A., decl.) = (330°, 0°). This pole orientation indicates a high obliquity of 50°-80°. Title: ARTEMIS II: A Second-Generation Catalog of LASCO Coronal Mass Ejections Including Mass and Kinetic Energy Authors: Floyd, O.; Lamy, P.; Boursier, Y.; Llebaria, A. Bibcode: 2013SoPh..288..269F Altcode: The ARTEMIS-I catalog of coronal mass ejections (CMEs) was initially developed on a first generation of low-resolution synoptic maps constructed from the SOHO/LASCO-C2 images of the K-corona and resulted in an online database listing all events detected since January 1996 (Boursier et al., Solar Phys.257, 125, 2009). A new generation of synoptic maps with higher temporal (a factor of 1.5) and angular (a factor of 2.5) resolutions allowed us to reconsider the question of CME detection and resulted in the production of a new catalog: ARTEMIS-II. The parameters estimated for each detected CME are still the date and time of appearance, the position angle, the angular width, and (when detected at several solar distances) the global and median velocities. The new synoptic maps correct for the limited number of velocity determinations reported in the ARTEMIS-I catalog. We now determine the propagation velocity of 79 % of detected CMEs instead of 30 % in the previous version. A final major improvement is the estimation of the mass and kinetic energy of all CMEs for which we could determine the velocity, that is ≈ 13 000 CMEs until December 2010. Individual comparisons of velocity determination of 23 CMEs for which a full three-dimensional kinematical solution has been published indicate that ARTEMIS-II performs extremely well except at the highest velocities, an intrinsic limitation of our method. Finally, individual comparisons of mass determination of seven CMEs for which a robust solution has been obtained from stereographic observations demonstrate the quality of the ARTEMIS-II results. Title: Sunskirting comets discovered with the LASCO coronagraphs over the decade 1996-2008 Authors: Lamy, P.; Faury, G.; Llebaria, A.; Knight, M. M.; A'Hearn, M. F.; Battams, K. Bibcode: 2013Icar..226.1350L Altcode: In addition to an unprecedented number of Kreutz sungrazing comets, the LASCO coronagraphs have discovered some 238 unrelated “sunskirting” comets over the 12 years from 1996 to 2008. This new class is organized in several groups, and at least two comets have further been found periodic. This article presents the photometry and the heliocentric light curves of these 238 sunskirting comets. The bulk of them exhibit a continuous increase of the brightness as the comet approaches the Sun, reach a peak before perihelion and then progressively fade with a large variety of brightness gradients. However some of them have peak brightness either at or post-perihelion, whereas a quite large number are approximately flat. Likewise for the sungrazers, we find a color effect prominent between 8 and 40R⊙ (solar radii) which we interpret as resulting from the emission lines of the Na I doublet (D lines). We finally characterize the different groups of sunskirters on the basis of their cumulative distribution function of the peak brightness and of their fragmentation history. Title: Early pre-perihelion characterization of Comet C/2012 S1 (ISON) Authors: Li, Jian-Yang; Kelley, M. S.; Farnham, T. L.; A'Hearn, M. F.; Knight, M. M.; Weaver, H. A.; Mutchler, M. J.; Lamy, P.; Toth, I. Bibcode: 2013DPS....4540702L Altcode: Comet C/2012 S1 (ISON) is a dynamically new comet on a sungrazing orbit. As such, C/ISON represents a unique opportunity to study both the cosmic-ray-irradiated surface, produced during the comet's long residence in the Oort cloud, and much deeper layers in the nucleus, exposed when the comet passes 1.7 solar radii from the Sun's surface at perihelion. During the first phase of our investigation, we collected broadband images of C/ISON on April 10, 2012 at a heliocentric distance of 4.15 AU, using the Hubble Space Telescope WFC3/UVIS. We used the F606W and F438W filters in three HST orbits covering a total span of ~19 hrs. The comet shows a well delineated coma in the sunward direction extending about 2" from the nucleus, and a dust tail at least 25" long. The coma has an average red color of 5%/0.1 micron within 1.6" from the nucleus, becoming redder towards the tail. Both the color and the size of the coma in the sunward direction are consistent with outflow of micron sized dust. Broadband photometry yielded Afρ of 1376 cm at 589 nm, and 1281 cm at 433 nm, measured with a 1.6" radius aperture. The total brightness of the comet within a 0.12" radius aperture remained unchanged within 0.03 mag for the entire duration of the observations. A well defined sunward jet is visible after removing the 1/ρ brightness distribution. The jet is centered at position angle 290 deg (E of Celestial N), with a cone angle of 45 deg, a projected length of 1.6", and a slight curvature towards the north near the end. No temporal change in the morphology is observed, suggesting the jet is circumpolar. Under this assumption, the jet’s apparent position constrains the rotational pole to lie within 30 deg of (RA, Dec) = (330, 0), and an obliquity of 50-80 deg. Preliminary analysis using a coma-nucleus separation technique suggests a nuclear radius less than 2 km. The survival of such a small nucleus during its sungrazing perihelion is certainly questionable. Title: Hubble Imaging of the Nucleus of Comet ISON Authors: Lamy, Philippe Bibcode: 2013hst..prop13478L Altcode: Comet C/2012 S1 {ISON} is both a new "nearly isotropic" and a sungrazing comet with anoutstanding apparition in cycle 21, passing within 0.42 AU of the Earth.We propose a 12-orbit Hubble postperihelion investigation of this comet that will provide a detailed view of its nucleus originating from the Oort cloud and of the possible consequences of its very close approach to the Sun at a perihelion distance of 0.012471 AU such as fragmentation.We will determine the size, shape, rotational period, and color {UBVRI} ofthe nucleus of C/2012 S1 or of its fragment should disruption occurs. This passage of a new "nearly isotropic" comet very close tothe Earth offers a rare opportunity to investigate this population ofobjects, and we expect many other observatories to attempt detecting itsnucleus in the mid-infrared, millimetric and centimetric domains.Combining the Hubble results with those from other observatories shouldyield a comprehensive picture of this NIC that can be compared to thedetailed data collected on ecliptic comets {ECs} during the past 3decades. The differences and similarities between NICs and ECs shouldyield valuable insights into the origin and evolution of comets. Title: Millimetre continuum observations of comet C/2009 P1 (Garradd) Authors: Boissier, J.; Bockelée-Morvan, D.; Groussin, O.; Lamy, P.; Biver, N.; Crovisier, J.; Colom, P.; Moreno, R.; Jorda, L.; Piétu, V. Bibcode: 2013A&A...557A..88B Altcode: 2013arXiv1307.8253B Context. Little is known about the physical properties of the nuclei of Oort Cloud comets. Measuring the thermal emission of a nucleus is one of the few means for deriving its size and constraining some of its thermal properties.
Aims: We attempted to measure the nucleus size of the Oort Cloud comet C/2009 P1 (Garradd).
Methods: We used the Plateau de Bure Interferometer to measure the millimetric thermal emission of this comet at 157 GHz (1.9 mm) and 266 GHz (1.1 mm).
Results: Whereas the observations at 266 GHz were not usable due to bad atmospheric conditions, we derived a 3σ upper limit on the comet continuum emission of 0.41 mJy at 157 GHz. Using a thermal model for a spherical nucleus with standard thermal parameters, we found an upper limit of 5.6 km for the radius. The dust contribution to our signal is estimated to be negligible. Given the water production rates measured for this comet and our upper limit, we estimated that Garradd was very active, with an active fraction of its nucleus larger than 50%.

Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Title: THERMAP: the mid-infrared (8-16 µm) spectro-imager of the ESA Marco Polo R mission Authors: Groussin, O.; Licandro, J.; Helbert, J.; Alí Lagoa, V.; Brageot, E.; Davidsson, B.; Delbó, M.; Delsanti, A.; Garcia-Talavera, M. R.; Green, S.; Jorda, L.; Knollenberg, J.; Kührt, E.; Lamy, P.; Lellouch, E.; Levacher, P.; Reynaud, J. -L.; Rozitis, B.; Sunshine, J.; Vernazza, P. Bibcode: 2013EPSC....8..196G Altcode: THERMAP is a mid-infrared (8-16 μm) spectroimager, selected by the European Space Agency (ESA) in February 2013 for the scientific payload of the Marco Polo R M-class mission. We present in this paper the instrument and its scientific objectives. Title: Thermal properties, sizes, and size distribution of Jupiter-family cometary nuclei Authors: Fernández, Y. R.; Kelley, M. S.; Lamy, P. L.; Toth, I.; Groussin, O.; Lisse, C. M.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.; Fitzsimmons, A.; Licandro, J.; Lowry, S. C.; Meech, K. J.; Pittichová, J.; Reach, W. T.; Snodgrass, C.; Weaver, H. A. Bibcode: 2013Icar..226.1138F Altcode: 2013arXiv1307.6191F We present results from SEPPCoN, an on-going Survey of the Ensemble Physical Properties of Cometary Nuclei. In this report we discuss mid-infrared measurements of the thermal emission from 89 nuclei of Jupiter-family comets (JFCs). All data were obtained in 2006 and 2007 using imaging capabilities of the Spitzer Space Telescope. The comets were typically 4-5 AU from the Sun when observed and most showed only a point-source with little or no extended emission from dust. For those comets showing dust, we used image processing to photometrically extract the nuclei. For all 89 comets, we present new effective radii, and for 57 comets we present beaming parameters. Thus our survey provides the largest compilation of radiometrically-derived physical properties of nuclei to date. We have six main conclusions: (a) The average beaming parameter of the JFC population is 1.03 ± 0.11, consistent with unity; coupled with the large distance of the nuclei from the Sun, this indicates that most nuclei have Tempel 1-like thermal inertia. Only two of the 57 nuclei had outlying values (in a statistical sense) of infrared beaming. (b) The known JFC population is not complete even at 3 km radius, and even for comets that approach to ∼2 AU from the Sun and so ought to be more discoverable. Several recently-discovered comets in our survey have small perihelia and large (above ∼2 km) radii. (c) With our radii, we derive an independent estimate of the JFC nuclear cumulative size distribution (CSD), and we find that it has a power-law slope of around -1.9, with the exact value depending on the bounds in radius. (d) This power-law is close to that derived by others from visible-wavelength observations that assume a fixed geometric albedo, suggesting that there is no strong dependence of geometric albedo with radius. (e) The observed CSD shows a hint of structure with an excess of comets with radii 3-6 km. (f) Our CSD is consistent with the idea that the intrinsic size distribution of the JFC population is not a simple power-law and lacks many sub-kilometer objects. Title: The persistent activity of Jupiter-family comets at 3-7 AU Authors: Kelley, Michael S.; Fernández, Yanga R.; Licandro, Javier; Lisse, Carey M.; Reach, William T.; A'Hearn, Michael F.; Bauer, James; Campins, Humberto; Fitzsimmons, Alan; Groussin, Olivier; Lamy, Philippe L.; Lowry, Stephen C.; Meech, Karen J.; Pittichová, Jana; Snodgrass, Colin; Toth, Imre; Weaver, Harold A. Bibcode: 2013Icar..225..475K Altcode: 2013arXiv1304.3818K We present an analysis of comet activity based on the Spitzer Space Telescope component of the Survey of the Ensemble Physical Properties of Cometary Nuclei. We show that the survey is well suited to measuring the activity of Jupiter-family comets at 3-7 AU from the Sun. Dust was detected in 33 of 89 targets (37 ± 6%), and we conclude that 21 comets (24 ± 5%) have morphologies that suggest ongoing or recent cometary activity. Our dust detections are sensitivity limited, therefore our measured activity rate is necessarily a lower limit. All comets with small perihelion distances (q < 1.8 AU) are inactive in our survey, and the active comets in our sample are strongly biased to post-perihelion epochs. We introduce the quantity ɛfρ, intended to be a thermal emission counterpart to the often reported Afρ, and find that the comets with large perihelion distances likely have greater dust production rates than other comets in our survey at 3-7 AU from the Sun, indicating a bias in the discovered Jupiter-family comet population. By examining the orbital history of our survey sample, we suggest that comets perturbed to smaller perihelion distances in the past 150 yr are more likely to be active, but more study on this effect is needed. Title: Photometric Calibration of the LASCO-C2 Coronagraph over 14 Years (1996 - 2009) Authors: Gardès, B.; Lamy, P.; Llebaria, A. Bibcode: 2013SoPh..283..667G Altcode: We present a photometric calibration of the SOHO/LASCO-C2 coronagraph based on the analysis of all stars down to magnitude V=8 that transited its field of view during the past 14 years of operation (1996 - 2009), extending the previous work of Llebaria, Lamy, and Danjard (Icarus182, 281, 2006). The pre-processing of the images incorporates the most recent determination of the evolution of the LASCO-C2 performances. The automatic procedure then analyzes some 260 000 images to detect, locate, and measure those stars. Aperture photometry is performed using four different aperture sizes, and the zero points (ZPs) of the photometric transformations between the LASCO-C2 magnitudes for its orange filter and the standard V magnitudes are determined after introducing a correction for the color of the stars. A new statistical method ("bootstrap") is introduced to assess the confidence intervals of the mean yearly value of the ZPs. The correction for finite aperture required to derive the calibration coefficient for the surface photometry of extended sources is based on the reconstructed image of bright saturated stars and a robust model for the growth curve. The global temporal evolution of the sensitivity of LASCO-C2 is compatible with a continuous decrease at a rate of ≈ 0.56 % per year. However, it is better described by two separate linear variations with a discontinuity at the time of the loss of SOHO. After the resumption of normal operations in 1999, the linear decrease of the sensitivity amounts to ≈ 0.35 % per year. Title: Comet C/2012 S1 (Ison) Authors: Li, Jian-Yang; Weaver, H. A.; Kelley, M. S.; Farnham, T. L.; A'Hearn, M. F.; Knight, M. M.; Mutchler, M. J.; Lamy, P.; Toth, I.; Yoshimoto, K.; Gonzalez, J. J.; Shurpakov, S.; Pilz, U.; Scarmato, T. Bibcode: 2013CBET.3496....1L Altcode: 2013CBET.3496....1W Jian-Yang Li, Planetary Science Institute; H. A. Weaver, Applied Physics Laboratory, Johns Hopkins University; M. S. Kelley, T. L. Farnham, and M. F. A'Hearn, University of Maryland; M. M. Knight, Lowell Observatory; M. J. Mutchler, Space Telescope Science Institute; P. Lamy, Laboratoire d'Astrophysique de Marseille; and I. Toth, Hungarian Academy of Sciences, obtained broadband images of comet C/2012 S1 (cf. CBET 3238) on Apr. 10 (when at r = 4.15 AU and D = 4.24 AU) using the Hubble Space Telescope (HST) WFC3/UVIS cameras with the F606W and F438W filters. The observations were performed in three HST orbits, with the second orbit about 2.5 hr after the first, and the last about 13.5 hr from the second. Preliminary analysis using a coma-nucleus separation technique (cf. Lamy et al. 2009, A.Ap. 508, 1045) suggests a nuclear radius less than 2 km. The total brightness of the comet within a 0".24-diameter aperture remained unchanged within 0.03 mag over the 19-hr observing window. Broadband photometry yielded Af(rho) = 1376 cm at 589 nm, and 1281 cm at 433 nm, consistent with a red slope of 5 percent per 0.1 micron for the coma dust. A well-defined jet is visible after removing the 1/r brightness distribution. The jet is centered on position angle 290 deg, with a cone angle of 45 deg, a projected length of 1".6, and a slight curvature towards the north near the end. No temporal change in the morphology is observed over the three epochs, suggesting that the jet is circumpolar. Under this assumption, the jet's apparent position constrains the rotational pole to lie within 30 deg of R.A. = 330 deg, Decl. = 0 deg (equinox 2000.0). The images are posted at the following website URL: http://hubblesite.org/newscenter/archive/releases/2013/14/. Total-magnitude estimates (visual unless otherwise noted): 2012 Oct. 14.77 UT, 17.3 (K. Yoshimoto, Yamaguchi, Japan, 0.16-m reflector + CCD); Dec. 19.82, 16.5 (Yoshimoto); 2013 Jan. 13.90, 14.8 (J. J. Gonzalez, Leon, Spain, 0.20-m reflector; visual); 21.85, 15.8 (S. Shurpakov, Baran', Belarus, 20-cm reflector + CCD); Feb. 2.90, 15.0 (U. Pilz, Leipzig, Germany, 32-cm reflector; visual); 11.57, 15.8 (Yoshimoto); 23.74, 15.8 (Shurpakov); Mar. 6.72, 15.5 (Shurpakov); 10.76, 16.1 (T. Scarmato, Calabria, Italy, 25-cm reflector + CCD + R_c filter); 23.79, 15.8 (Scarmato); Apr. 6.82, 16.2 (Scarmato); 9.48, 15.8 (Yoshimoto); 19.81, 16.2 (Scarmato). Title: A new multiresolution method applied to the 3D reconstruction of small bodies Authors: Capanna, C.; Jorda, L.; Lamy, P. L.; Gesquiere, G. Bibcode: 2012AGUFM.P23B1937C Altcode: The knowledge of the three-dimensional (3D) shape of small solar system bodies, such as asteroids and comets, is essential in determining their global physical properties (volume, density, rotational parameters). It also allows performing geomorphological studies of their surface through the characterization of topographic features, such as craters, faults, landslides, grooves, hills, etc.. In the case of small bodies, the shape is often only constrained by images obtained by interplanetary spacecrafts. Several techniques are available to retrieve 3D global shapes from these images. Stereography which relies on control points has been extensively used in the past, most recently to reconstruct the nucleus of comet 9P/Tempel 1 [Thomas (2007)]. The most accurate methods are however photogrammetry and photoclinometry, often used in conjunction with stereography. Stereophotogrammetry (SPG) has been used to reconstruct the shapes of the nucleus of comet 19P/Borrelly [Oberst (2004)] and of the asteroid (21) Lutetia [Preusker (2012)]. Stereophotoclinometry (SPC) has allowed retrieving an accurate shape of the asteroids (25143) Itokawa [Gaskell (2008)] and (2867) Steins [Jorda (2012)]. We present a new photoclinometry method based on the deformation of a 3D triangular mesh [Capanna (2012)] using a multi-resolution scheme which starts from a sphere of 300 facets and yields a shape model with 100; 000 facets. Our strategy is inspired by the "Full Multigrid" method [Botsch (2007)] and consists in going alternatively between two resolutions in order to obtain an optimized shape model at a given resolution before going to the higher resolution. In order to improve the robustness of our method, we use a set of control points obtained by stereography. Our method has been tested on images acquired by the OSIRIS visible camera, aboard the Rosetta spacecraft of the European Space Agency, during the fly-by of asteroid (21) Lutetia in July 2010. We present the corresponding 3D shape model of its surface and compare it with models obtained with the SPG and SPC methods. We finally illustrate the practical interest of our approach in geomorphological studies through an analysis of depth to diameter ratio of several craters and topographic properties of other features. Botsch, M., et al., "Geometric modeling based on polygonal meshes," Proc. ACM SIGGRAPH Course Notes, 2007 Capanna, C., et al.: 3D Reconstruction of small solar system bodies using photoclinometry by deformation, IADIS International Journal on Computer Science and Information Systems, in press, 2012. Gaskell, R. W., et al.: Characterizing and navigating small bodies with imaging data, Meteoritics and Planetary Science, vol 43, p. 1049, 2008. Jorda, L., et al: Asteroid (2867) Steins: Shape, Topography and Global Physical Properties from OSIRIS observations, Icarus, in press, 2012. Oberst, J., et al.: The nucleus of Comet Borrelly: a study of morphology and surface brightness, Icarus, vol. 167, 2004. Preusker, F., et al.: The northern hemisphere of asteroid 21 Lutetia topography and orthoimages from Rosetta OSIRIS NAC image data, Planetary and Space Science, vol. 66, p. 54-63, 2012. Thomas, P. C., et al.: The shape, topography, and geology of Tempel 1 from Deep Impact observations, Icarus, vol. 187, Issue 1, p. 4-15, 2007 Title: Testing a Two-temperature Model of the Solar Corona with Empirically-derived Plasma parameters Authors: Strachan, L.; Panasyuk, A.; Lamy, P. L.; van der Holst, B.; Oran, R.; Frazin, R. A.; Manchester, W. B. Bibcode: 2012AGUFMSH31B..04S Altcode: We compare the plasma parameters predicted from the Michigan two-temperature chromosphere-corona model to those parameters obtained from the analyses of UVCS and LASCO data. The empirical data are organized as Carrington rotation maps for the electron densities, proton kinetic temperatures, and outflow velocities. This data format makes it convenient for understanding the differences between the modeled and observed latitudinal variations in the plasma parameters. In addition, we discuss the model performance for characterizing streamers and coronal holes at different phases in the solar activity cycle. These tests are useful for investigating how well coronal and solar wind models simulate the underlying physical processes that operate in the solar corona. Title: Disk-resolved photometry of Asteroid (2867) Steins Authors: Spjuth, S.; Jorda, L.; Lamy, P. L.; Keller, H. U.; Li, J. -Y. Bibcode: 2012Icar..221.1101S Altcode: We present a new method to perform disk-resolved photometry in order to investigate the intrinsic photometric properties of the surface of small Solar System bodies. We adopt the standard approach where a shape model is combined with a photometric formalism - in practise the Hapke formalism - to remove the effects of topography and recover the photometric (Hapke) parameters of either the global surface or, in its most elaborated form, the spatial variations of these parameters across the surface. Our method operates in the space of the facets representing the three-dimensional shape of the body, whereas all past analysis have always been performed in the space of the image pixels although they are not intrinsic to the surface of the body. This has the advantage of automatically tracking the same local surface element on a series of images. We first apply our method to images of the nucleus of Comet 9P/Tempel 1 obtained by the High-Resolution Imager (HRI) instrument on board the Deep Impact spacecraft and our derived Hapke parameters are in good agreement with those published by Li et al. (Li, J.-Y. et al. [2007]. Icarus 187, 41-55) within their respective uncertainties. We confirm the presence of an extended region of higher roughness in the southern hemisphere of the nucleus and the higher albedo of the ice-rich regions identified by Sunshine et al. (Sunshine, J.M. et al. [2006]. Science 311, 1453-1455) near the equator. The photometric properties of Asteroid (2867) Steins are then studied from multi-spectral images obtained with the OSIRIS Wide Angle Camera (WAC) on board the Rosetta spacecraft during its flyby on 5 September 2008. Our analysis indicates that the surface is highly porous (∼84%) and that it exhibits both a shadow-hiding opposition effect (SHOE) and probably, a coherent-backscatter opposition effect (CBOE). The single scattering albedo is the highest (SSA = 0.57) ever observed among small bodies visited by spacecrafts. Our modelled roughness parameter is indicative of a high microscale roughness. The surface of Steins may in fact exhibit a fractal surface with high roughness present on a large range of scales, from micrometers to centimeters. The geometric and Bond albedos are calculated with the Hapke parameters yielding Ap = 0.39 ± 0.02 and AB = 0.24 ± 0.01. This high albedo is consistent with an iron-poor surface composition similar to aubrite meteorites which are suspected to originate from the E-type asteroids. We find no photometric variations on the surface at the (limited) spatial resolution of the WAC images. Title: Asteroid (2867) Steins: Shape, topography and global physical properties from OSIRIS observations Authors: Jorda, L.; Lamy, P. L.; Gaskell, R. W.; Kaasalainen, M.; Groussin, O.; Besse, S.; Faury, G. Bibcode: 2012Icar..221.1089J Altcode: The Rosetta spacecraft flew by Asteroid (2867) Steins on 5 September 2008, allowing the onboard OSIRIS cameras to collect the first images of an E-type asteroid. We implemented several three-dimensional reconstruction techniques to retrieve its shape. Limb profiles, combined with stereo control points, were used to reconstruct an approximate shape model. This model was refined using a stereophotoclinometry technique to accurately retrieve the topography of the hemisphere observed by OSIRIS. The unseen part of the surface was constrained by the technique of light curves inversion.

The global shape resembles a top with dimensions along the principal axes of inertia of 6.83 × 5.70 × 4.42 km. It is conspicuously more regular than other small asteroids like (233) Eros and (25143) Itokawa. Its mean radius is Rm = 2.70 km and its equivalent radius (radius of a sphere of equivalent volume) is Rv = 2.63 km. The north pole is oriented at RA = 99 ± 5° and Dec = -59 ± 5°, which implies a very large obliquity of 172° and a retrograde rotation.

Maps of the gravitational field and slopes were calculated for the well-imaged part of the asteroid. Together with the shape, they helped characterizing the most prominent topographic features identified at the surface of (2867) Steins: an equatorial ridge restricted to the extremities of the long axis, a large crater having dimensions of 2100 × 1800 m in the southern hemisphere, and an elongated hill in the northern hemisphere. We conjecture that the equatorial ridge was formed by centrifugal acceleration as the asteroid was spun up by the Yarkovsky-O’Keefe-Radzievskii-Paddack effect. Title: High surface porosity as the origin of emissivity features in asteroid spectra Authors: Vernazza, P.; Delbo, M.; King, P. L.; Izawa, M. R. M.; Olofsson, J.; Lamy, P.; Cipriani, F.; Binzel, R. P.; Marchis, F.; Merín, B.; Tamanai, A. Bibcode: 2012Icar..221.1162V Altcode: Emission features in the mid-IR domain (7-25 μm) are quite ubiquitous among large asteroids and therefore offer the potential to uncover their surface composition. However, when comparing these spectra with the actual laboratory spectra of both minerals and meteorites, they do not necessarily match. Here, and in a companion paper by King et al. (in preparation, 2012), we show that by modifying the sample preparation - typically by suspending meteorite and/or mineral powder (<30 μm) in IR-transparent KBr (potassium bromide) powder - we are able to reproduce the spectral behavior of those main-belt asteroids with emissivity features. This resulting good match between KBr-diluted meteorite spectra and asteroid spectra suggests an important surface porosity (>90%) for the first millimeter for our asteroid sample. It therefore appears that mid-IR emission spectra of asteroids do not only carry information about their surface composition but they can also help us constraining their surface structure (under-dense versus compact surface structure), as suggested by Emery et al. (Emery, J.P., Cruikshank, D.P., van Cleve, J. [2006]. Icarus 182, 496-512) in the case of the Jupiter Trojans. The large surface porosity inferred from the mid-IR spectra of certain asteroids is also implied by two other independent measurements, namely their thermal inertia and their radar albedo. We further clarified how much compositional information can be retrieved from the mid-IR range by focusing our analysis on a single object, 624 Hektor. We showed that the mid-IR range provides critical constraints (i) on its origin and of that of the red Trojans that we locate in the formation regions of the comets, and (ii) on the primordial composition of the dust present in the outer region (>10 AU) of the Solar System’s protoplanetary disk. Future investigations should focus on finding the mechanism responsible for creating such high surface porosity. Title: Identification and physical properties of craters on Asteroid (2867) Steins Authors: Besse, S.; Lamy, P.; Jorda, L.; Marchi, S.; Barbieri, C. Bibcode: 2012Icar..221.1119B Altcode: We report on the physical properties of the craters of Asteroid (2867) Steins based on an analysis of images obtained with the OSIRIS instrument during the Rosetta flyby that took place on 5 September 2008. To compensate for the limited spatial resolution of the images and unfavorable illumination conditions, we applied three different filtering techniques designed to enhance the craters detection. The selected images covered 44% of the overall surface of the asteroid and 42 craters were detected. We calculated their diameter and depth using a forward modeling procedure that combines a global shape model with an idealized semi-hemispherical representation of the craters, further incorporating photometric properties to generate simulated images. The resulting images were then compared to the original images. Crater diameters range from 150 to 2100 m with depth-to-diameter ratios of 0.04-0.25, a wide range consistent with other small bodies. A striking dichotomy was observed between the two sides of the asteroid reflected by both a ratio of 3.6 between the spatial density and very different power exponents of the size distribution functions, -3.3 versus -1.5. Altogether these peculiar properties most likely reflect the particular history of Steins, in particular the impact that created the largest crater, Diamond, and extensively damaged the “original” Steins. A combination of various processes, including destruction, erasure, direct or indirect infill by seismic shaking, and even the YORP effect can explain the observed physical properties of the craters on Steins. A few craters may be drainage basins connected to a hypothetical fault, itself a product of the Diamond event. Title: Intercomparison of the LASCO-C2, SECCHI-COR1, SECCHI-COR2, and Mk4 Coronagraphs Authors: Frazin, Richard A.; Vásquez, Alberto M.; Thompson, William T.; Hewett, Russell J.; Lamy, Philippe; Llebaria, Antoine; Vourlidas, Angelos; Burkepile, Joan Bibcode: 2012SoPh..280..273F Altcode: 2012SoPh..tmp..140F In order to assess the reliability and consistency of white-light coronagraph measurements, we report on quantitative comparisons between polarized brightness [pB] and total brightness [B] images taken by the following white-light coronagraphs: LASCO-C2 on SOHO, SECCHI-COR1 and -COR2 on STEREO, and the ground-based MLSO-Mk4. The data for this comparison were taken on 16 April 2007, when both STEREO spacecraft were within 3.1∘ of Earth's heliographic longitude, affording essentially the same view of the Sun for all of the instruments. Due to the difficulties of estimating stray-light backgrounds in COR1 and COR2, only Mk4 and C2 produce reliable coronal-hole values (but not at overlapping heights), and these cannot be validated without rocket flights or ground-based eclipse measurements. Generally, the agreement between all of the instruments' pB values is within the uncertainties in bright streamer structures, implying that measurements of bright CMEs also should be trustworthy. Dominant sources of uncertainty and stray light are discussed, as is the design of future coronagraphs from the perspective of the experiences with these instruments. Title: Multi Element Telescope for Imaging and Spectroscopy (METIS) coronagraph for the Solar Orbiter mission Authors: Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero; Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Nicolosi, Piergiorgio; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro; Auchère, Frédéric; Berlicki, Arkadiusz; Bruno, Roberto; Capobianco, Gerardo; Ciaravella, Angela; Crescenzio, Giuseppe; Da Deppo, Vania; D'Amicis, Raffaella; Focardi, Mauro; Frassetto, Fabio; Heinzel, Peter; Lamy, Philippe L.; Landini, Federico; Massone, Giuseppe; Malvezzi, Marco A.; Moses, J. Dan; Pancrazzi, Maurizio; Pelizzo, Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.; Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela Bibcode: 2012SPIE.8443E..09A Altcode: METIS, the “Multi Element Telescope for Imaging and Spectroscopy”, is a coronagraph selected by the European Space Agency to be part of the payload of the Solar Orbiter mission to be launched in 2017. The unique profile of this mission will allow 1) a close approach to the Sun (up to 0.28 A.U.) thus leading to a significant improvement in spatial resolution; 2) quasi co-rotation with the Sun, resulting in observations that nearly freeze for several days the large-scale outer corona in the plane of the sky and 3) unprecedented out-of-ecliptic view of the solar corona. This paper describes the experiment concept and the observational tools required to achieve the science drivers of METIS. METIS will be capable of obtaining for the first time: • simultaneous imaging of the full corona in polarized visible-light (590-650 nm) and narrow-band ultraviolet HI Lyman α (121.6 nm); • monochromatic imaging of the full corona in the extreme ultraviolet He II Lyman α (30.4 nm); • spectrographic observations of the HI and He II Ly α in corona. These measurements will allow a complete characterization of the three most important plasma components of the corona and the solar wind, that is, electrons, hydrogen, and helium. This presentation gives an overview of the METIS imaging and spectroscopic observational capabilities to carry out such measurements. Title: In-orbit determination of the straylight in the SOHO/LASCO-C2 coronagraph and its temporal evolution Authors: Llebaria, A.; Loirat, J.; Lamy, P. Bibcode: 2012SPIE.8442E..26L Altcode: The LASCO-C2 coronagraph aboard SOHO (the SOlar and Heliospheric Observatory) is continuously observing the solar corona since early 1996. The instrument as well as the experimental context underwent during this period many changes and observational constraints. The consequences for the in-orbit calibration procedures are illustrated with the systematic measure of the coronagraph straylight. Disentangle the coronal signal and the straylight is the crucial point. The separation and monitoring of the straylight component rely on the daily sets of polarized observations of the corona and a minimal set of assumptions about the symmetry of the F-corona (the dust component of the solar corona). Four main changes have been detected since 1996. Specific recommendations for the in-orbit calibration of future spatial coronagraphs will be presented. Title: THERMAP : a mid-infrared spectro-imager for the Marco Polo R mission Authors: Groussin, O.; Brageot, E.; Reynaud, J. -L.; Lamy, P.; Jorda, L.; Licandro, J.; Helbert, J.; Knollenberg, J.; Kührt, E.; Delbó, M. Bibcode: 2012epsc.conf...48G Altcode: 2012espc.conf...48G We present THERMAP, a mid-infrared (8-16 μm) spectro-imager based on uncooled micro-bolometer detector arrays. Due to the recent technological development of these detectors, which have undergone significant improvements in the last decade, we wanted to test their performances for a space mission to small bodies in the inner Solar System. THERMAP was selected by ESA in January 2012 for a one year assessment study, in the framework of a call for declaration of interest in science instrumentation for the Marco Polo R Cosmic Vision mission. In this paper, we present some results of this study and in particular demonstrate that the new generation of uncooled micro-bolometer detectors has all the imaging and spectroscopic capabilities to fulfill the scientific objectives of the Marco Polo R mission. THERMAP scientific objectives - The midinfrared instrument of the Marco Polo R mission must be able i) to determine the surface temperature by mapping the entire surface with an absolute accuracy of at least 5 K (goal 1 K) above 200 K, ii) to determine the thermal inertia with an accuracy of 10% and iii) to determine the surface composition by mapping the entire surface with a spectral resolution of 70 between 8 and 16 μm. The above mappings should be performed with a spatial resolution of 10 m for the entire surface (global characterization) and 10 cm for the sampling sites (local characterization). THERMAP imaging capabilities - In order to test the imaging capabilities of the THERMAP uncooled microbolometer detector, we set up an experiment based on a 640x480 ULIS micro-bolometer array, a germanium objective and a black body. Using the results of this experiment, we show that calibrated radiometric images can be obtained down to at least 258 K (lower limit of our experiment), and that two calibration points are sufficient to determine the absolute scene temperature with an accuracy better than 1.5 K. An extrapolation to lower temperatures provides an accuracy of about 5 K at 180 K, the lowest temperature the detector can measure. THERMAP spectroscopic capabilites - In order to test the spectroscopic performances of the detector, we added flux attenuating neutral density mid-infrared filters (transmittance: 50%, 10%, 1%) to our experiment. Our results show that we can perform spectroscopic measurements with a spectral resolution R=40-80 in the wavelength range 8-16 μm for a scene temperature larger than 300 K, the typical surface temperature of a Near Earth Asteroid at 1 AU from the Sun. THERMAP preliminary design - From the above results, we defined a preliminary design for the instrument. THERMAP is a mid-infrared (8-16 μm) spectro-imager based on two uncooled microbolometer arrays. It is composed of two channels, one for imaging and one for spectroscopy. A flip mirror allows switching between the two channels. Calibration is performed using deep space and two black bodies at known temperature. The design of the THERMAP instrument has a strong heritage from the MERTIS instrument on board Bepi-Colombo [1], which guarantees its feasibility and reliability. Our design is very flexible in term of operations, which is fundamental for a mission to a binary asteroid system (1996 FG3). The THERMAP instrument will be proposed for Marco Polo R and any future space missions to small bodies in the inner solar system. Title: THERMAP: a mid-infrared spectro-imager based on an uncooled micro-bolometer for space missions to small bodies of the solar system Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. -L.; Fargant, G.; Licandro, J.; Helbert, J.; Knollenberg, J.; Kührt, E. Bibcode: 2012SPIE.8442E..4OB Altcode: We report on the feasibility study of a mid-infrared (8-18 µm) spectro-imager called THERMAP, based on an uncooled micro-bolometer detector array. Due to the recent technological development of these detectors, which have undergone significant improvements in the last decade, we wanted to test their performances for the Marco Polo R ESA Cosmic Vision mission. In this study, we demonstrate that the new generation of uncooled micro-bolometer detectors has all the imaging and spectroscopic capabilities to fulfill the scientific objectives of this mission. In order to test the imaging capabilities of the detector, we set up an experiment based on a 640x480 ULIS micro-bolometer array, a germanium objective and a black body. Using the results of this experiment, we show that calibrated radiometric images can be obtained down to at least 255 K (lower limit of our experiment), and that two calibration points are sufficient to determine the absolute scene temperature with an accuracy better than 1.5 K. Adding flux attenuating neutral density mid-infrared filters (transmittance: 50%, 10%, 1%) to our experiment, we were able to evaluate the spectroscopic performances of the detector. Our results show that we can perform spectroscopic measurements in the wavelength range 8-16 µm with a spectral resolution of R~40-80 for a scene temperature <300 K, the typical surface temperature of a Near Earth Asteroid at 1 AU from the Sun. The mid-infrared spectro-imager THERMAP, based on the above detector, is therefore well suited for the Marco Polo R mission. Title: Lutetia global shape and topography reconstructed with photoclinometry by deformation Authors: Capanna, C.; Jorda, L.; Gesquière, G.; Lamy, P.; Kaasalainen, M. Bibcode: 2012epsc.conf..616C Altcode: 2012espc.conf..616C 3D reconstruction of asteroids and cometary nuclei allows us to model their physical, geomorphological and geological properties. We applied a new reconstruction method by photoclinometry based on the minimization of the chi-square difference between observed and synthetic images by deformation of a 3D triangular mesh to a set of images of asteroid (21) Lutetia acquired by the OSIRIS cameras aboard ESA's ROSETTA spacecraft in July 2010. This allowed us to retrieve an improved global shape of the asteroid as well as the local topography of its main features: the large Massalia crater, the North pole crater complex and several other topographic features of interest. A comparison of this model with those obtained with other techniques will be presented. Title: Sunskirting comets discovered with the LASCO coronagraphs (1996-2008) Authors: Lamy, P.; Faury, G.; Llebaria, A.; Knight, M.; A'Hearn, M. Bibcode: 2012epsc.conf..308L Altcode: 2012espc.conf..308L In addition to an unprecedented number of Kreutz sungrazing comets, the LASCO coronagraphs aboard SOHO have discovered some 238 unrelated "sunskirting" comets from 1996 to 2008. This new family is organized in several groups, and two comets have further been found periodic. We present the photometry and the heliocentric light curves of these sunskirting comets. The bulk of them exhibit a continuous increase of the brightness as the comet approaches, reaching a peak before perihelion and then progressively fading with a large variety of brightness gradients. However, some of them have peak brightness either at or post-perihelion whereas a quite large number are approximately flat. We finally characterize the different groups of sunskirters on the basis of their distribution of peak magnitudes and of their fragmentation history. Title: A portrait of the asteroid (21) Lutetia after the Rosetta flyby Authors: Jorda, Laurent; Thomas, Nicolas; Scholten, Frank; Preusker, Frank; Gaskell, Robert; Lamy, Philippe; Marchi, Simone; Vernazza, Pierre; Carry, Benoit; Hviid, Stubbe; Sierks, Holger; Keller, Horst Uwe; Kaasalainen, Mikko Bibcode: 2012cosp...39..836J Altcode: 2012cosp.meet..836J The asteroid (21) Lutetia has been observed by several instruments aboard ESA's ROSETTA spacecraft on July 10, 2010. The OSIRIS imaging system allowed the reconstruction of the topography of its surface. A number of intriguing features appeared on the images and/or on the topographic models: boulders, landslides, craters with various profiles, among others. The combination of these data with light curves and adaptive optics profiles allowed to retrieve the global shape of the asteroid, which yielded an estimate of its volume. Combined with the accurate mass determination from the radio science RSI instrument, a very high density of 3.4 g/cm^{3} was obtained. Title: Plasmoid Ejection at a Solar Total Eclipse Authors: Koutchmy, S.; Bazin, C.; Berghmans, D.; De Groof, A.; Druckmüller, M.; Tavabi, E.; Engell, A.; Filippov, B.; Golub, L.; Lamy, Ph.; Linker, J.; Mikic, Z.; Mouette, J.; Nitschelm, Ch.; Seaton, D.; Slemzin, V. Bibcode: 2012EAS....55..223K Altcode: The existence of coronal plasmoids has been postulated for many years in order to supply material to streamers and possibly to the solar wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made under the 2.2 solar radii (R0) occulting disk to look at the ultimate sources of the SW; EUV imagers are preferably devoted to the analysis of the corona on and very near the solar disk. Here, in addition to eclipse white-light (W-L) snapshots, we used the new SWAP space-borne imager designed for the systematic survey of coronal activity in the EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using summed and co-aligned images, the corona can then be evaluated for the 1st time up to the limit of this FOV. At the time of the July 11, 2010, solar total eclipse a 20h continuous run of observations was collected, including images taken during eclipse totality from several ground observing locations where W-L data were collected. A plasmoid-like off-limb event was followed using the SWAP summed Title: Shape modeling technique KOALA validated by ESA Rosetta at (21) Lutetia Authors: Carry, B.; Kaasalainen, M.; Merline, W. J.; Müller, T. G.; Jorda, L.; Drummond, J. D.; Berthier, J.; O'Rourke, L.; Ďurech, J.; Küppers, M.; Conrad, A.; Tamblyn, P.; Dumas, C.; Sierks, H.; Osiris Team; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.; Bertaux, J. -L.; , Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P.; Ip, W. -H. Hviid, S.; Keller, H. U.; Koschny, D.; Knollenberg, J.; Kramm, J. R.; Kuehrt, E.; Lamy, P.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P. Bibcode: 2012P&SS...66..200C Altcode: 2011arXiv1112.5944C; 2012P&SS...66..200T We present here a comparison of our results from ground-based observations of asteroid (21) Lutetia with imaging data acquired during the flyby of the asteroid by the ESA Rosetta mission. This flyby provided a unique opportunity to evaluate and calibrate our method of determination of size, 3-D shape, and spin of an asteroid from ground-based observations. Knowledge of certain observable physical properties of small bodies (e.g., size, spin, 3-D shape, and density) have far-reaching implications in furthering our understanding of these objects, such as composition, internal structure, and the effects of non-gravitational forces. We review the different observing techniques used to determine the above physical properties of asteroids and present our 3-D shape-modeling technique KOALA - Knitted Occultation, Adaptive-optics, and Lightcurve Analysis - which is based on multi-dataset inversion. We compare the results we obtained with KOALA, prior to the flyby, on asteroid (21) Lutetia with the high-spatial resolution images of the asteroid taken with the OSIRIS camera on-board the ESA Rosetta spacecraft, during its encounter with Lutetia on 2010 July 10. The spin axis determined with KOALA was found to be accurate to within 2°, while the KOALA diameter determinations were within 2% of the Rosetta-derived values. The 3-D shape of the KOALA model is also confirmed by the spectacular visual agreement between both 3-D shape models (KOALA pre- and OSIRIS post-flyby). We found a typical deviation of only 2 km at local scales between the profiles from KOALA predictions and OSIRIS images, resulting in a volume uncertainty provided by KOALA better than 10%. Radiometric techniques for the interpretation of thermal infrared data also benefit greatly from the KOALA shape model: the absolute size and geometric albedo can be derived with high accuracy, and thermal properties, for example the thermal inertia, can be determined unambiguously. The corresponding Lutetia analysis leads to a geometric albedo of 0.19±0.01 and a thermal inertia below 40 J m-2 s-0.5 K-1, both in excellent agreement with the Rosetta findings. We consider this to be a validation of the KOALA method. Because space exploration will remain limited to only a few objects, KOALA stands as a powerful technique to study a much larger set of small bodies using Earth-based observations. Title: Geological map and stratigraphy of asteroid 21 Lutetia Authors: Massironi, Matteo; Marchi, Simone; Pajola, Maurizio; Snodgrass, Colin; Thomas, Nicolas; Tubiana, Cecilia; Baptiste Vincent, Jean; Cremonese, Gabriele; da Deppo, Vania; Ferri, Francesca; Magrin, Sara; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; Koschny, Detlef; Osiris Team Bibcode: 2012P&SS...66..125M Altcode: 2012P&SS...66..125T The OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) images acquired during the recent Rosetta fly-by of Lutetia (10th of July 2010), enabled us to unravel the long geological history of the asteroid. This is recorded on its highly varied surface which displays geological units of disparate ages. In particular, using images of the closest approach, five main regions (in turn subdivided into minor units) have been discriminated on the basis of crater density, overlapping and cross-cutting relationships, and presence of linear features (i.e., fractures, faults, grooves, troughs). Other regions, with still unclear stratigraphic position, were also recognized on images of lower resolution on the bases of geomorphological properties such as crater density, relationship with scarp and ridges, and sharp morphological boundaries. In this work the geological evolution of Lutetia surface is reconstructed through the description of its main units and related contacts. The oldest regions imaged during the closest approach (Achaia and Noricum) are pervasively affected by fractures and grooves and display surfaces so heavily cratered to be dated back to a period not far from the Late Heavy Bombardment (yielding Achaia a crater retention age of 3.6-3.7 Ga). A crater of 55 km diameter, named Massilia and corresponding to the Narbonensis region, cuts both Achaia and Noricum regions and probably represents the most prominent event of the Lutetia history. The considerable crater density on its floor and walls, the absence of discernable deposits related to the impact event, and the intense deformation of it floor - all attest to its relatively great age. The North Polar Cluster (Baetica region) is associated with smooth ejecta broadly mantling the surrounding units and displays few craters and no linear features, demonstrating its relatively young age (estimated at less than 300 Ma). The North Polar Crater Cluster is the product of superimposed impacts; the last one of 24 km of diameter excavated the pre-existing ejecta up to the bedrock which locally outcrops at the crater rim. The ejecta of this last impact were involved in several gravitational phenomena testified by the great variety of deposits made up of mega-boulders diamictons, fine materials, gravitational taluses and debris, and landslide accumulations. A part from the big cratering events generating Massilia and the North Polar Crater Cluster, the Lutetia geological history is also punctuated by minor events still recorded by its stratigraphic record well imaged by the closest approach data. Title: The geomorphology of (21) Lutetia: Results from the OSIRIS imaging system onboard ESA's Rosetta spacecraft Authors: Thomas, N.; Barbieri, C.; Keller, H. U.; Lamy, P.; Rickman, H.; Rodrigo, R.; Sierks, H.; Wenzel, K. P.; Cremonese, G.; Jorda, L.; Küppers, M.; Marchi, S.; Marzari, F.; Massironi, M.; Preusker, F.; Scholten, F.; Stephan, K.; Barucci, M. A.; Besse, S.; El-Maarry, M. R.; Fornasier, S.; Groussin, O.; Hviid, S. F.; Koschny, D.; Kührt, E.; Martellato, E.; Moissl, R.; Snodgrass, C.; Tubiana, C.; Vincent, J. -B. Bibcode: 2012P&SS...66...96T Altcode: The surface of (21) Lutetia is highly complex with significant interactions between ancient and more recent structures. This work attempts to summarize the surface geomorphology observed using the high resolution images from OSIRIS, the imaging system onboard the European Space Agency's Rosetta spacecraft. A wide range of surface morphologies are seen including heavily cratered terrain, extensive sets of lineaments, young impact craters, and a ridge, the height of which is more than 1/5th of the mean radius of the body. Very young and very old terrains (as inferred from crater densities) are seen in close proximity. The longest continuous lineament is over 80 km long. The lineaments show regional-dependent organization and structure. Several categories of lineament can be described. Lineaments radial to impact craters as seen on other asteroidal bodies are mostly absent. Although the lineaments may be of seismic origin (and possibly the result of several impact-induced events), impacts producing recent large craters place constraints on seismic phenomena. In particular, stronger attenuation of shocks than seen on other asteroidal bodies seems to be required. Inhomogeneous energy transport, possibly matching observed inhomogeneous ejecta deposition may offer explanations for some of the observed phenomena. Some impact craters show unusual forms, which are probably the result of impact into a surface with relief comparable to the resultant crater diameter and/or oblique impact. There is evidence that re-surfacing through landslides has occurred at several places on the object. Title: Boulders on Lutetia Authors: Küppers, Michael; Moissl, Richard; Vincent, Jean-Baptiste; Besse, Sébastien; Hviid, Stubbe F.; Carry, Benoît; Grieger, Björn; Sierks, Holger; Keller, Horst Uwe; Marchi, Simone; OSIRIS Team; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P.; Ip, W. -H., Jorda, L., Koschny, D.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Lamy, P.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Michalik, H. Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P. Bibcode: 2012P&SS...66...71K Altcode: 2012P&SS...66...71T More than 200 boulders are among the many prominent geological features seen on Lutetia by the OSIRIS cameras onboard Rosetta. Most are concentrated around the central crater in Baetica regio with a few more apparently associated with Patavium crater. The size range of boulders visible to OSIRIS is about 60-300 m. We model the trajectories of boulders ejected from the central crater and show that their distribution is consistent with most of them being created from that crater, similar to the situation on asteroid Eros where most of the boulders are believed to originate from Shoemaker crater. We evaluate various destruction mechanisms for ejecta blocks and conclude that, using current estimates of the number of small asteroids in the main belt, destruction by impacts of small (several meters diameter) projectiles limits the lifetime of the boulders (and the age of the central crater) to a maximum of 300 million years. Since several analyses of crater ages and size distributions also come up with surprisingly young ages, the size-frequency distribution of small main-belt asteroids (below the size currently reached by surveys) may warrant to be revisited. Title: (21) Lutetia spectrophotometry from Rosetta-OSIRIS images and comparison to ground-based observations Authors: Magrin, S.; La Forgia, F.; Pajola, M.; Lazzarin, M.; Massironi, M.; Ferri, F.; da Deppo, V.; Barbieri, C.; Sierks, H.; Osiris Team; A'Hearn, M.; Angrilli, F.; Barucci, A.; Bertaux, J. -L.; Cremonese, G.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P.; Hviid, S.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, J. R.; Kuehrt, E.; Küppers, M.; Lamy, P.; Lara, L. M.; López-Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Weissman, P. R.; Wenzel, K. -P. Bibcode: 2012P&SS...66...43M Altcode: 2012P&SS...66...43T Here we present some preliminary results on surface variegation found on (21) Lutetia from ROSETTA-OSIRIS images acquired on 2010-07-10. The spectrophotometry obtained by means of the two cameras NAC and WAC (Narrow and Wide Angle Cameras) is consistent with ground based observations, and does not show surface diversity above the data error bars. The blue and UV images (shortward 500 nm) may, however, indicate a variegation of the optical properties of the asteroid surface on the Baetica region (Sierks et al., 2011). We also speculate on the contribution due to different illumination and to different ground properties (composition or, more probably, grain size diversity). In particular a correlation with geologic units independently defined by Massironi et al. (2012) is evident, suggesting that the variegation of the ground optical properties is likely to be real. Title: Physical properties of craters on asteroid (21) Lutetia Authors: Vincent, Jean-Baptiste; Besse, Sébastien; Marchi, Simone; Sierks, Holger; Massironi, Matteo; OSIRIS Team; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Koschny, D.; Knollenberg, J.; Kramm, J. R.; Kuehrt, E.; Lamy, P.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P. Bibcode: 2012P&SS...66...79V Altcode: 2012P&SS...66...79T This paper presents an analysis of the physical properties of craters on asteroid (21) Lutetia, derived from images acquired by OSIRIS, the high-resolution cameras onboard ESA's spacecraft Rosetta. Crater morphology on (21) Lutetia fits very well with the general picture of what was known for previously visited small bodies, with a typical depth to diameter ratio of 0.12. We discuss here the distribution of this parameter all across the surface, but also region by region, and see how it can vary from one location to another and help to distinguish between different geological units. In a later section of the paper we study in more details Beatica region where a deep ejecta blanket filled most of the craters, and estimate the thickness profile of this ejecta based on our analysis of the d/D. We find a good agreement with existing scaling laws, and use this to constrain the scale of the original event that reshaped the surface around the North pole of the asteroid. Finally, we report on the observations of avalanches in several crater flanks, and the presence of many asymmetrical craters with flow-like features, and discuss the evidence for widespread fine material all over the surface. Title: Search for satellites near (21) Lutetia using OSIRIS/Rosetta images Authors: Bertini, Ivano; Sabolo, Walter; Gutierrez, Pedro J.; Marzari, Francesco; Snodgrass, Colin; Tubiana, Cecilia; Moissl, Richard; Pajola, Maurizio; Lowry, Stephen C.; Barbieri, Cesare; Ferri, Francesca; Davidsson, Björn; Sierks, Holger; OSIRIS Team; A'Hearn, M.; Angrilli, F.; Barucci, A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Hviid, S.; Ip, W. -H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, J. R.; Kuehrt, E.; Küppers, M.; Lamy, P.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P. Bibcode: 2012P&SS...66...64B Altcode: 2012P&SS...66...64T On 2010 July 10 the ESA Rosetta mission flew by the large asteroid (21) Lutetia. One of the scientific goals of the onboard OSIRIS instrument was the search for satellites of the asteroid, with more than 20 images specifically dedicated to this topic. An observational campaign was devised with a selection of filters and exposure times tailored to maximize the possibility of detecting small companions and determining their bound orbits. Data were analyzed with suitable methods to remove cosmic ray hits and known background objects, in order to search for persistent detections of potential interesting flux sources. We found no unambiguous detections of a satellite larger than ∼160m inside the entire sphere of gravitational influence. Our search confirmed the absence of bound companions larger than ∼30m inside 20 primary radii. These limits are a factor of ∼30 smaller than the values reported so far from large ground-based telescopes using adaptive optics and from the Hubble Space Telescope. Title: ESCAPE : a first step to high resolution solar coronagraphy in Antarctica Authors: Damé, L.; Abe, L.; Faurobert, M.; Fineschi, S.; Kuzin, S.; Lamy, P.; Meftah, M.; Vives, S. Bibcode: 2012EAS....55..359D Altcode: The Dome C high plateau is unique for coronagraphic observations: sky brightness is reduced, water vapour is low, seeing is excellent and continuity of observations on several weeks is possible. ESCAPE (the Extreme Solar Coronagraphy Antarctic Program Experiment) will perform 2-dimensional spectroscopy of the forbidden line of FeXIV at 530.285 nm: precise line profile analysis will allow the diagnostic of the nature of waves by simultaneous measurements of velocities and intensities in the corona. ESCAPE is proposed to Institut Paul-Emile Victor (IPEV) for a campaign in 2012-2013 at Dome C/Concordia since all subsystems are available in particular thanks to an ESA STARTIGER 2010 R&D "Toward a New Generation of Formation Flying Coronagraph". Using state-of-the-art technologies developed for Space missions (a Three Mirrors Anastigmat telescope, the TMA, a 4 stages Liquid Crystal Tunable-filter Polarimeter, the LCTP) allows us to propose an automated Coronal Green Line full-field Polarimeter for unique observations (waves nature and intensity to address coronal heating) with the best possible performances on Earth and for preparing and testing the technologies for the next steps in Space. No other site would allow such coronagraphic performances (the sky brightness is a factor 2 to 4 better than in Hawaï) and with high spatial resolution (better than an arcsec is possible). Title: High Surface Porosity as the Origin of Emissivity Features in Asteroid Spectra Authors: Vernazza, P.; Delbo, M.; King, P. L.; Izawa, M. R. M.; Olofsson, J.; Lamy, P.; Cipriani, F.; Binzel, R. P.; Marchis, F.; Merin, B.; Tamanai, A. Bibcode: 2012LPICo1667.6049V Altcode: Here we show that mid-IR emission spectra of asteroids do not only carry information about their surface composition but they can also help us constraining their surface structure (under-dense versus compact surface structure). Title: Visible-Wavelength Survey of Jupiter-Family Cometary Nuclei as Part of SEPPCoN Authors: Fernandez, Y. R.; Lowry, S. C.; Meech, K. J.; Laird, R.; Fitzsimmons, A.; Snodgrass, C.; Weissman, P. R.; Pittichova, J.; Bauer, J. M.; Weaver, H. A.; Lisse, C. M.; A'Hearn, M. F.; Campins, H.; Groussin, O.; Kelley, M. S.; Lamy, P. L.; Licandro, J.; Toth, I.; Reach, W. T. Bibcode: 2012LPICo1667.6488F Altcode: We present observations of a statistically-significant number of Jupiter-family cometary nuclei as part of SEPPCoN (Survey of the Ensemble Physical Properties of Cometary Nuclei). We present preliminary results on distributions of albedos and shapes. Title: The Trojans' Odyssey Space Mission Authors: Lamy, P.; Vernazza, P.; Groussin, O.; Poncy, J.; Martinot, V.; Hinglais, E.; Bell, J.; Cruikshank, D.; Helbert, J.; Marzari, F.; Morbidelli, A.; Rosenblatt, P. Bibcode: 2012LPICo1667.6443L Altcode: The proposed Trojans' Odyssey mission is envisioned as a reconnaissance, multiple flyby mission aimed at visiting several objects, typically five Trojans and one Hilda. Title: Asteroid (21) Lutetia: Global and Spatially Resolved Photometric Properties Authors: Lamy, P.; Jorda, L.; Vernazza, P.; Faury, G. Bibcode: 2012LPICo1667.6442L Altcode: We will present results on the global photometric properties of (21) Lutetia, as well as spatially resolved properties based on the Hapke formalism. Title: The Geomorphology of Asteroid 21 Lutetia from In-Situ Imaging Authors: Jorda, L.; Thomas, N.; Lamy, P. Bibcode: 2012LPICo1667.6406J Altcode: We present an overview of the surface geomorphology of asteroid 21 Lutetia observed using the high resolution images from OSIRIS, the imaging system onboard the European Space Agency’s Rosetta spacecraft. Title: Comet 8P/Tuttle: A portrait of a contact-binary nucleus from Hubble and Spitzer space telescopes observations Authors: Lamy, P.; Toth, I.; Jorda, L.; Groussin, O.; Faury, G.; Weaver, H. Bibcode: 2012EGUGA..1410506L Altcode: We detected the nucleus of comet 8P/Tuttle, a nearly-isotropic comet (NIC) in a 13.5~yr orbital period, during its 2007--2008 close (0.25~AU) Earth encounter with the Planetary Camera 2 of the Hubble Space Telescope(HST on 10-11 December 2007 and with the infrared camera (MIPS) of the Spitzer Space Telescope (SST) on 22-23 June 2008, sampling the rotational period of the nucleus. We determined a synodic rotational period of 11.40 +/-0.12 h and, by combining with the radar observations of Harmon et al. (2010), a sidereal rotation period of 11.444 +/-0.001h. The visible and thermal light curve exhibit a complex shape best modeled by a contact-binary as evidenced by the radar observations. By combining these light curves and adding a constraint on the thermal inertia coming from millimetric observations at the Plateau de Bure Observatory, we determined the shape and size of the binary system approximated by two spheres in contact with respective radius of 2.56 and 1.1 km, a common albedo in the range 0.04 to 0.054 and a linear phase coefficient in the range 0.033 to 0.04 mag/deg. These results suggest a strong similarity of the properties of the nuclei of ecliptic and nearly-isotropic comets. We found that the shape model resulting from the radar observations is incompatible with both the HST and SST observations. A partial agreement could be obtained by assuming very different albedos of the two components, in a ratio of at least 5. Title: Trojans' Odyssey: Unveiling the early history of the Solar System Authors: Lamy, Philippe; Vernazza, Pierre; Poncy, Joel; Martinot, Vincent; Hinglais, Emmanuel; Canalias, Elisabet; Bell, Jim; Cruikshank, Dale; Groussin, Olivier; Helbert, Joern; Marzari, Francesco; Morbidelli, Alessandro; Rosenblatt, Pascal; Sierks, Holger Bibcode: 2012ExA....33..685L Altcode: 2011ExA...tmp...71L; 2011ExA...tmp..114L; 2011ExA...tmp...92L In our present understanding of the Solar System, small bodies (asteroids, Jupiter Trojans, comets and TNOs) are the most direct remnants of the original building blocks that formed the planets. Jupiter Trojan and Hilda asteroids are small primitive bodies located beyond the `snow line', around respectively the L4 and L5 Lagrange points of Jupiter at ∼5.2 AU (Trojans) and in the 2:3 mean-motion resonance with Jupiter near 3.9 AU (Hildas). They are at the crux of several outstanding and still conflicting issues regarding the formation and evolution of the Solar System. They hold the potential to unlock the answers to fundamental questions about planetary migration, the late heavy bombardment, the formation of the Jovian system, the origin and evolution of trans-neptunian objects, and the delivery of water and organics to the inner planets. The proposed Trojans' Odyssey mission is envisioned as a reconnaissance, multiple flyby mission aimed at visiting several objects, typically five Trojans and one Hilda. It will attempt exploring both large and small objects and sampling those with any known differences in photometric properties. The orbital strategy consists in a direct trajectory to one of the Trojan swarms. By carefully choosing the aphelion of the orbit (typically 5.3 AU), the trajectory will offer a long arc in the swarm thus maximizing the number of flybys. Initial gravity assists from Venus and Earth will help reducing the cruise time as well as the ΔV needed for injection thus offering enough capacity to navigate among Trojans. This solution further opens the unique possibility to flyby a Hilda asteroid when leaving the Trojan swarm. During the cruise phase, a Main Belt Asteroid could be targeted if requiring a modest ΔV. The specific science objectives of the mission will be best achieved with a payload that will perform high-resolution panchromatic and multispectral imaging, thermal-infrared imaging/ radiometry, near- and mid-infrared spectroscopy, and radio science/mass determination. The total mass of the payload amounts to 50 kg (including margins). The spacecraft is in the class of Mars-Express or a down-scaled version of Jupiter Ganymede Orbiter. It will have a dry mass of 1200 kg, a total mass at launch of 3070 kg and a ΔV capability of 700 m/s (after having reached the first Trojan) and can be launched by a Soyuz rocket. The mission operations concept (ground segment) and science operations are typical of a planetary mission as successfully implemented by ESA during, for instance, the recent flybys of Main Belt asteroids Steins and Lutetia. Title: The interaction between coronal mass ejections and streamers as viewed by LASCO over 15 years Authors: Floyd, O.; Lamy, P.; Llebaria, A. Bibcode: 2012EGUGA..14.9899F Altcode: The question of the relationship of coronal mass ejections (CMEs) to streamers dates back to the early observations of CMEs with space coronagraphs and subsequent efforts to understand their origin. Whereas the mass and kinetic energy losses of CMEs are insignificant in the corona, they are considered a key player as a means to remove magnetic flux and helicity that would otherwise build up in the corona. How this may work essentially boils down to the nature of the CME-streamer interaction i.e., as to whether CMEs respond passively or contribute dynamically to the coronal field restructuring. We are reconsidering this question on the basis of high resolution synoptic maps at 3 Rsun constructed from the LASCO-C2 images of the corona over 15 years (1996-2010) thus encompassing cycle 23 and the rising phase of cycle 24. During that period, our ARTEMIS II catalog of LASCO CMEs reports 21394 events and studying their interaction with the streamer belt requires an automated procedure. For this purpose, we consider that streamers are prominently one dimensional objects, manifesting the boundary between regions of opposite magnetic polarities that can be represented by the line of maximum radiance along them. As such, streamers are defined as ridges on the synoptic maps and an efficient way to detect these ridges consist in applying a watershed filter. Then for each CME (which appears as a vertical streak on the synoptic maps), we detect the streamer ridges present before and after its occurence all along its latitudinal extent. The CME-streamer interaction is then quantified in terms of geometric changes (appearance/disappearance or displacement of the streamer) and photometric changes (brightening/dimming of the streamer). We will present statistical data on these interactions for the 1996-2010 time period. Title: A Global Two-temperature Corona and Inner Heliosphere Model: A Comprehensive Validation Study Authors: Jin, M.; Manchester, W. B.; van der Holst, B.; Gruesbeck, J. R.; Frazin, R. A.; Landi, E.; Vasquez, A. M.; Lamy, P. L.; Llebaria, A.; Fedorov, A.; Toth, G.; Gombosi, T. I. Bibcode: 2012ApJ...745....6J Altcode: The recent solar minimum with very low activity provides us a unique opportunity for validating solar wind models. During CR2077 (2008 November 20 through December 17), the number of sunspots was near the absolute minimum of solar cycle 23. For this solar rotation, we perform a multi-spacecraft validation study for the recently developed three-dimensional, two-temperature, Alfvén-wave-driven global solar wind model (a component within the Space Weather Modeling Framework). By using in situ observations from the Solar Terrestrial Relations Observatory (STEREO) A and B, Advanced Composition Explorer (ACE), and Venus Express, we compare the observed proton state (density, temperature, and velocity) and magnetic field of the heliosphere with that predicted by the model. Near the Sun, we validate the numerical model with the electron density obtained from the solar rotational tomography of Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph C2 data in the range of 2.4 to 6 solar radii. Electron temperature and density are determined from differential emission measure tomography (DEMT) of STEREO A and B Extreme Ultraviolet Imager data in the range of 1.035 to 1.225 solar radii. The electron density and temperature derived from the Hinode/Extreme Ultraviolet Imaging Spectrometer data are also used to compare with the DEMT as well as the model output. Moreover, for the first time, we compare ionic charge states of carbon, oxygen, silicon, and iron observed in situ with the ACE/Solar Wind Ion Composition Spectrometer with those predicted by our model. The validation results suggest that most of the model outputs for CR2077 can fit the observations very well. Based on this encouraging result, we therefore expect great improvement for the future modeling of coronal mass ejections (CMEs) and CME-driven shocks. Title: The Evolution of Plasma Parameters on a Coronal Source Surface at 2.3 R ⊙ during Solar Minimum Authors: Strachan, L.; Panasyuk, A. V.; Kohl, J. L.; Lamy, P. Bibcode: 2012ApJ...745...51S Altcode: 2011arXiv1111.1206S We analyze data from the Solar and Heliospheric Observatory to produce global maps of coronal outflow velocities and densities in the regions where the solar wind is undergoing acceleration. The maps use UV and white light coronal data obtained from the Ultraviolet Coronagraph Spectrometer and the Large Angle Spectroscopic Coronagraph, respectively, and a Doppler dimming analysis to determine the mean outflow velocities. The outflow velocities are defined on a sphere at 2.3 R ⊙ from Sun-center and are organized by Carrington Rotations during the solar minimum period at the start of solar cycle 23. We use the outflow velocity and density maps to show that while the solar minimum corona is relatively stable during its early stages, the shrinkage of the north polar hole in the later stages leads to changes in both the global areal expansion of the coronal hole and the derived internal flux tube expansion factors of the solar wind. The polar hole areal expansion factor and the flux tube expansion factors (between the coronal base and 2.3 R ⊙) start out as super-radial but then they become more nearly radial as the corona progresses away from solar minimum. The results also support the idea that the largest flux tube expansion factors are located near the coronal hole/streamer interface, at least during the deepest part of the solar minimum period. Title: Asteroid (21) Lutetia as a remnant of Earth’s precursor planetesimals Authors: Vernazza, P.; Lamy, P.; Groussin, O.; Hiroi, T.; Jorda, L.; King, P. L.; Izawa, M. R. M.; Marchis, F.; Birlan, M.; Brunetto, R. Bibcode: 2011Icar..216..650V Altcode: Isotopic and chemical compositions of meteorites, coupled with dynamical simulations, suggest that the main belt of asteroids between Mars and Jupiter contains objects formed in situ as well as a population of interlopers. These interlopers are predicted to include the building blocks of the terrestrial planets as well as objects that formed beyond Neptune (Bottke et al. 2006, Levison et al. 2009, Walsh et al. 2011). Here we report that the main belt asteroid (21) Lutetia - encountered by the Rosetta spacecraft in July 2010 - has spectral (from 0.3 to 25 μm) and physical (albedo, density) properties quantitatively similar to the class of meteorites known as enstatite chondrites. The chemical and isotopic compositions of these chondrites indicate that they were an important component of the formation of Earth and other terrestrial planets. This meteoritic association implies that Lutetia is a member of a small population of planetesimals that formed in the terrestrial planet region and that has been scattered in the main belt by emerging protoplanets (Bottke et al. 2006) and/or by the migration of Jupiter (Walsh et al. 2011) early in its history. Lutetia, along with a few other main-belt asteroids, may contains part of the long-sought precursor material (or closely related materials) from which the terrestrial planets accreted. Title: The cosmic dust analyser onboard cassini: ten years of discoveries Authors: Srama, R.; Kempf, S.; Moragas-Klostermeyer, G.; Altobelli, N.; Auer, S.; Beckmann, U.; Bugiel, S.; Burton, M.; Economomou, T.; Fechtig, H.; Fiege, K.; Green, S. F.; Grande, M.; Havnes, O.; Hillier, J. K.; Helfert, S.; Horanyi, M.; Hsu, S.; Igenbergs, E.; Jessberger, E. K.; Johnson, T. V.; Khalisi, E.; Krüger, H.; Matt, G.; Mocker, A.; Lamy, P.; Linkert, G.; Lura, F.; Möhlmann, D.; Morfill, G. E.; Otto, K.; Postberg, F.; Roy, M.; Schmidt, J.; Schwehm, G. H.; Spahn, F.; Sterken, V.; Svestka, J.; Tschernjawski, V.; Grün, E.; Röser, H. -P. Bibcode: 2011CEAS....2....3S Altcode: 2018arXiv180204772S The interplanetary space probe Cassini/Huygens reached Saturn in July 2004 after 7 years of cruise phase. The German cosmic dust analyser (CDA) was developed under the leadership of the Max Planck Institute for Nuclear Physics in Heidelberg under the support of the DLR e.V. This instrument measures the interplanetary, interstellar and planetary dust in our solar system since 1999 and provided unique discoveries. In 1999, CDA detected interstellar dust in the inner solar system followed by the detection of electrical charges of interplanetary dust grains during the cruise phase between Earth and Jupiter. The instrument determined the composition of interplanetary dust and the nanometre-sized dust streams originating from Jupiter's moon Io. During the approach to Saturn in 2004, similar streams of submicron grains with speeds in the order of 100 km/s were detected from Saturn's inner and outer ring system and are released to the interplanetary magnetic field. Since 2004 CDA measured more than one million dust impacts characterising the dust environment of Saturn. The instrument is one of the three experiments which discovered the active ice geysers located at the south pole of Saturn's moon Enceladus in 2005. Later, a detailed compositional analysis of the water ice grains in Saturn's E ring system led to the discovery of large reservoirs of liquid water (oceans) below the icy crust of Enceladus. Finally, the determination of the dust-magnetosphere interaction and the discovery of the extended E ring (at least twice as large as predicted) allowed the definition of a dynamical dust model of Saturn's E ring describing the observed properties. This paper summarizes the discoveries of a 10-year story of success based on reliable measurements with the most advanced dust detector flown in space until today. This paper focuses on cruise results and findings achieved at Saturn with a focus on flux and density measurements. CDA discoveries related to the detailed dust stream dynamics, E ring dynamics, its vertical profile and E ring compositional analysis are published elsewhere (see Hus et al. in AIP Conference Proccedings 1216:510-513, 2010; Hsu et al. in Icarus 206:653-661, 2010; Kempf et al. in Icarus 193:420, 2008; 206(2):446, 2010; Postberg et al. in Icarus 193(2):438, 2008; Nature 459:1098, 2009; Nature, 2011, doi: 10.1038/nature10175). Title: Comparison of Velocity, Density, Temperature, and Mass Flux Results with Solar Coronal Models Authors: Strachan, L.; Cranmer, S. R.; Panasyuk, A.; Kohl, J. L.; Lamy, P. L. Bibcode: 2011AGUFMSH53C..07S Altcode: We have recently computed a series of global maps of plasma parameters in the extended corona using data from the Solar and Heliospheric Observatory (SOHO). The synoptic maps of velocity, density, temperature, and mass flux were derived from UV and white light coronal data obtained from the Ultraviolet Coronagraph Spectrometer (UVCS) and the Large Angle Spectroscopic Coronagraph (LASCO). The parameters are defined on a sphere at 2.3~ R⊙ from Sun-center and are organized by Carrington Rotations during the 1996 -- 1998 solar minimum for Solar Cycle 23. The data imply that there are large flux tube expansion factors near the coronal hole/streamer boundaries, but these factors change significantly as the corona evolves from minimum to the rising phase. We compare these data to an independently developed theoretical model that includes damping and acceleration by Alfven waves in the corona (see Cranmer et al. 2007, ApJS, 171, 520). The data set will be extended in the future and it will be used for constraining other theoretical models of the corona and solar wind. Title: The helium shells of HeI and HeII at solar minimum: New results from eclipse flash spectra of 2008- 2010 Authors: Bazin, C.; Koutchmy, S.; Lamy, P. Bibcode: 2011sf2a.conf..203B Altcode: Flash spectra taken at high frame rate during the total solar eclipse of August 1st 2008 in Siberia and during the July 11th 2010 in French Polynesia are compared in the context of the quiet Sun near the minimum of activity. They both reveal the weak Paschen α 468.6 nm ionized helium line, seen as a helium shell in layers up to the 8 Mm heights. The preliminary evaluated effective height of the He I 4713 shell is 1.8 Mm and it is approximately 2.0 Mm for the He II 4686 emissions outside polar regions. These lines can be measured only in eclipse conditions, when the parasitic scattered light is negligible for very low solar fluxes corresponding to the coronal levels. Many faint lines are also seen in emission such as Ba +, Ti +, Fe +, but with a much lower radial extension. They were observed to be superposed to F-lines when defining the solar limb using the continuum background. A cartoon is proposed to describe the structuration of these low layers and to illustrate the contribution of the magnetic field. These observations are important new insights for understanding (i) the magnetic field inference in the very low layers of the solar transition region and (ii) the ionisation mechanisms producing the big jump of the temperature towards the corona, including the source of heating. Title: Observations of the White Light Corona from Solar Orbiter and Solar Probe Plus Authors: Howard, R. A.; Thernisien, A. F.; Vourlidas, A.; Plunkett, S. P.; Korendyke, C. M.; Sheeley, N. R.; Morrill, J. S.; Socker, D. G.; Linton, M. G.; Liewer, P. C.; De Jong, E. M.; Velli, M. M.; Mikic, Z.; Bothmer, V.; Lamy, P. L. Bibcode: 2011AGUFMSH43F..06H Altcode: The SoloHI instrument on Solar Orbiter and the WISPR instrument on Solar Probe+ will make white light coronagraphic images of the corona as the two spacecraft orbit the Sun. The minimum perihelia for Solar Orbiter is about 60 Rsun and for SP+ is 9.5 Rsun. The wide field of view of the WISPR instrument (about 105 degrees radially) corresponds to viewing the corona from 2.2 Rsun to 20 Rsun. Thus the entire Thomson hemisphere is contained within the telescope's field and we need to think of the instrument as being a traditional remote sensing instrument and then transitioning to a local in-situ instrument. The local behavior derives from the fact that the maximum Thomson scattering will favor the electron plasma close to the spacecraft - exactly what the in-situ instruments will be sampling. SoloHI and WISPR will also observe scattered light from dust in the inner heliosphere, which will be an entirely new spatial regime for dust observations from a coronagraph, which we assume to arise from dust in the general neighborhood of about half way between the observer and the Sun. As the dust grains approach the Sun, they evaporate and do not contribute to the scattering. A dust free zone has been postulated to exist somewhere inside of 5 Rsun where all dust is evaporated, but this has never been observed. The radial position where the evaporation occurs will depend on the precise molecular composition of the individual grains. The orbital plane of Solar Orbiter will gradually increase up to about 35 degrees, enabling a very different view through the zodiacal dust cloud to test the models generated from in-ecliptic observations. In this paper we will explore some of the issues associated with the observation of the dust and will present a simple model to explore the sensitivity of the instrument to observe such evaporations. Title: The Trojans' Odyssey space mission Authors: Lamy, P.; Vernazza, P.; Groussin, O.; Poncy, J.; Martinot, V.; Hinglais, E.; Bell, J.; Cruikshank, D.; Helbert, J.; Marzari, F.; Morbidelli, A.; Rosenblatt, P. Bibcode: 2011epsc.conf..703L Altcode: 2011DPS....43..703L In our present understanding of the Solar System, small bodies (asteroids, Jupiter Trojans, comets and TNOs) are the most direct remnants of the original building blocks that formed the planets. Jupiter Trojan and Hilda asteroids are small primitive bodies located beyond the "snow line", around respectively the L4 and L5 Lagrange points of Jupiter at 5.2 AU (Trojans) and in the 2:3 mean-motion resonance with Jupiter near 3.9 AU (Hildas). They are at the crux of several outstanding and still conflicting issues regarding the formation and evolution of the Solar System. They hold the potential to unlock the answers to fundamental questions about planetary migration, the late heavy bombardment, the formation of the Jovian system, the origin and evolution of trans-neptunian objects, and the delivery of water and organics to the inner planets. The proposed Trojans' Odyssey mission is envisioned as a reconnaissance, multiple flyby mission aimed at visiting several objects, typically five Trojans and one Hilda. It will attempt exploring both large and small objects and sampling those with any known differences in photometric properties. The orbital strategy consists in a direct trajectory to one of the Trojan swarms. By carefully choosing the aphelion of the orbit (typically 5.3 AU), the trajectory will offer a long arc in the swarm thus maximizing the number of flybys. Initial gravity assists from Venus and Earth will help reducing the cruise to 7 years as well as the ?V needed for injection thus offering enough capacity to navigate among Trojans. This solution further opens the unique possibility to flyby a Hilda asteroid when leaving the Trojan swarm. During the cruise phase, a Main Belt Asteroid could be targeted if requiring a modest ?V. The specific science objectives of the mission will be best achieved with a payload that will perform high-resolution panchromatic and multispectral imaging, thermal-infrared imaging/ radiometry, near- and mid-infrared spectroscopy, and radio science/mass determination. The total mass of the payload amounts to 50 kg (including margins). The spacecraft is in the class of Mars-Express or a down-scaled version of Jupiter Ganymede Orbiter. It will have a dry mass of 1200 kg, a total mass at launch of 3070 kg and a V capability of 700 m/sec (after having reached the first Trojan) and can be launched by a Soyuz rocket. The mission operations concept (ground segment) and science operations are typical of a planetary mission as successfully implemented by ESA during, for instance, the recent flybys of Main Belt asteroids Steins and Lutetia. Title: THERMAP: a mid-infrared spectro-imager based on an uncooled micro-bolometer for the Marco Polo R mission. Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. L.; Fargant, G. Bibcode: 2011epsc.conf..129B Altcode: 2011DPS....43..129B We report on an on-going feasibility study of a midinfrared (8-18 μm) spectro-imager for the Marco Polo R mission (THERMAP). Based on the recent development of uncooled micro-bolometer technology, we can now use these detectors for planetary missions. We present our results on using this detector to perform calibrated radiometric images, and a preliminary assessment of its performances for spectroscopic measurements of a Near Earth Asteroid (NEA). Title: Shape and Physical Properties of Asteroid (21) Lutetia from OSIRIS Images Authors: Jorda, L.; Gaskell, R.; Lamy, P.; Kaasalainen, M.; Groussin, O.; Faury, G.; Gutierrez, P.; Sabolo, W.; Hviid, S. Bibcode: 2011epsc.conf..776J Altcode: 2011DPS....43..776J The Rosetta spacecraft of the European Space Agency flew by asteroid (21) Lutetia on July, 10, 2010 on its way to its final target, comet 67P/Churyumov- Gerasimenko. A total of 460 images has been acquired during the flyby with the narrow (NAC) and wide (WAC) angle cameras of the OSIRIS instrument, the NAC pixel scale reaching a minimum value of 60 m at closest approach. Several filters have been used, covering a wavelength range from the far UV (0.25 μm) to the end of the visible spectrum (1.0 μm). The phase angle went through the range 11°-0°-160°, the spacecraft reaching opposition 18 min before closest approach. We will report on the calculation of the threedimensional high-resolution global shape model of (21) Lutetia using two techniques: stereophotoclinometry for the regions observed by OSIRIS, complemented by inversion of photometric light curves and adaptive optics profiles for the rest of the surface. This allows us to retrieve the physical properties of this object: volume, moments of inertia, gravity field, local gravitational slopes and rotational parameters. The density is calculated using the mass measured by the radio science experiment (RSI) on board Rosetta. We will further discuss quantitatively the properties of the main geo-morphological features observed at the surface. Title: Images of Asteroid 21 Lutetia: A Remnant Planetesimal from the Early Solar System Authors: Sierks, H.; Lamy, P.; Barbieri, C.; Koschny, D.; Rickman, H.; Rodrigo, R.; A'Hearn, M. F.; Angrilli, F.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Besse, S.; Carry, B.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; De Leon, J.; Ferri, F.; Fornasier, S.; Fulle, M.; Hviid, S. F.; Gaskell, R. W.; Groussin, O.; Gutierrez, P.; Ip, W.; Jorda, L.; Kaasalainen, M.; Keller, H. U.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Leyrat, C.; Moreno, J. J. Lopez; Magrin, S.; Marchi, S.; Marzari, F.; Massironi, M.; Michalik, H.; Moissl, R.; Naletto, G.; Preusker, F.; Sabau, L.; Sabolo, W.; Scholten, F.; Snodgrass, C.; Thomas, N.; Tubiana, C.; Vernazza, P.; Vincent, J. -B.; Wenzel, K. -P.; Andert, T.; Pätzold, M.; Weiss, B. P. Bibcode: 2011Sci...334..487S Altcode: Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 ± 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles. Title: Shape reconstruction of irregular bodies with multiple complementary data sources Authors: Kaasalainen, M.; Viikinkoski, M.; Carry, B.; Durech, J.; Lamy, P.; Jorda, L.; Marchis, F.; Hestroffer, D. Bibcode: 2011epsc.conf..416K Altcode: 2011DPS....43..416K Irregularly shaped bodies with at most partial in situ data are a particular challenge for shape reconstruction and mapping. We have created an inversion algorithm and software package for complementary data sources, with which it is possible to create shape and spin models with feature details even when only groundbased data are available. The procedure uses photometry, adaptive optics or other images, occultation timings, and interferometry as main data sources, and we are extending it to include range-Doppler radar and thermal infrared data as well. The data sources are described as generalized projections in various observable spaces [2], which allows their uniform handling with essentially the same techniques, making the addition of new data sources inexpensive in terms of computation time or software development. We present a generally applicable shape support that can be automatically used for all surface types, including strongly nonconvex or non-starlike shapes. New models of Kleopatra (from photometry, adaptive optics, and interferometry) and Hermione are examples of this approach. When using adaptive optics images, the main information from these is extracted from the limb and terminator contours that can be determined much more accurately than the image pixel brightnesses that inevitably contain large errors for most targets. We have shown that the contours yield a wealth of information independent of the scattering properties of the surface [3]. Their use also facilitates a very fast and robustly converging algorithm. An important concept in the inversion is the optimal weighting of the various data modes. We have developed a mathematicallly rigorous scheme for this purpose. The resulting maximum compatibility estimate [3], a multimodal generalization of the maximum likelihood estimate, ensures that the actual information content of each source is properly taken into account, and that the resolution scale of the ensuing model can be reliably estimated. We have applied our procedure to several asteroids, and the ground truth from the Rosetta/Lutetia flyby confirmed the ability of the approach to recover shape details [1] (see also Carry et al., this meeting). We have created a general flyby-version of the procedure to construct full models of planetary targets for which probe images are only available of a part of the surface (a typical setup for many planetary missions). We have successfully combined flyby images with photometry (Steins [4]) and adaptive optics images (Lutetia); the portion of the surface accurately determined by the flyby constrains the shape solution of the "dark side" efficiently. Title: Asteroids (21) Lutetia and (2867) Steins: same origin but different evolution ? Authors: Lamy, P.; Vernazza, P.; Groussin, O.; Jorda, L. Bibcode: 2011epsc.conf..699L Altcode: 2011DPS....43..699L Asteroids (21) Lutetia and (2867) Steins which have recently been visited by the Rosetta spacecraft of the European Space Agency are both members of very small populationss of bodies among the vast majority of asteroids. After having been the archetype of the M taxonomy class, Lutetia is now an Xc type (DeMeo et al. 2009). Steins is classified as an igneous E-type asteroids, more precisely in the new Xe subclass (De- Meo et al. 2009) which contains only 7 known members. The composition and henceforth origin of asteroids rely on their association to meteorites if proper analogs based on visible, NIR and MIR reflectances can be identified. Following the most recent spectroscopic works, the association of Lutetia to enstatite chondrites appears robust (Vernazza et al. 2011). The case of Steins is less clear but aubrite meteorites are favored although several features in its spectrum still poses problems and we actually may not have in our present meteorite collections the proper analog (Clark et al. 2004). The trend of these associations with meteorites which represent a reduced, volatile-poor, anhydrous end-member of early solar system materials (Rubin 1997, Scott 2007) thought to have formed in the inner region of the solar nebula, near the proto-Sun implies that neither Lutetia nor Steins formed at their present location in the asteroid belt and are probably part of the population of interlopers. The dynamical mechnanism that transported them from the inner solar system to the main belt is likely to be similar to the one explaining the origin of iron meteorites as remnants of differentiated planetesimals formed in the terrestrial planet region (Bottke et al. 2006). Extended dynamical simulations reveal that, at the time where terrestrial accretion was ongoing, a small fraction (<2%) of the planetesimals residing in the 0.5-1.5 AU region were scattered out by emerging protoplanets and achieved main-belt orbits, thus becoming dynamically indistinguishable from the rest of the main-belt population. However based on the physical properties derived from the recent flybys, Lutetia and Steins have followed very different evolutions. With a density of 3.4 g/cm3, Lutetia appears as a primordial planetesimal having suffered at most minimal shattering from the largest impacts. On the contrary, the shape of Steins suggests complete restructuring in a rubble-pile as a consequence of the catastrophic disruption of its parent body. Title: Asteroids (21) Lutetia: global and spatially resolved photometric properties Authors: Faury, G.; Lamy, P.; Vernazza, P.; Jorda, L.; Toth, I. Bibcode: 2011epsc.conf..759F Altcode: 2011DPS....43..759F Asteroids (21) Lutetia has recently been visited by the Rosetta spacecraft of the European Space Agency and imaged by its Rosetta narrow (NAC) and wide (WAC) angle cameras. The accurate photometric analysis of the images requires utmost care due to several instrumental problems, the most severe and complex to handle being the presence of optical ghosts which result from multiple reflections on the two filters inserted in the optical beam and on the thick window which protects the CCD detector from cosmic ray impacts. These ghosts prominently appears as either slighlty defocused images offset from the primary images or large round or elliptical halos. The appearance, the location and the radiance of each individual ghost depends upon the optical configuration (selected filters) and on the image itself so that no general model can be proposed. Consequently, a case-by-case approach must be adopted which requires a long and tedious work where each ghost is individually parametrized according to its specific geometry (defocused offset image or halo) and iteratively fitted to the original image. The procedure has been successfully applied to all NAC and WAC images and works extremely well with residuals and sometime artifacts at insignificant levels. Both NAC and WAC have further been recalibrated using the most recent observations of stellar calibrators VEGA and the solar analog 16 Cyg B allowing to correct the quantum efficiency response of the two CCD and the throughput for all channels (i.e., filters). We will present results on the global photometric properties of (21) Lutetia, albedo, phase function and spectral reflectivity as well as spatially resolved properties based on a novel method developed in the space of the facets representing the three-dimensional shape of the body. This method successfully implemented in the cases of the nucleus of comet 9P/Tempel 2 and of asteroid (2867) Steins (Spjuth et al. 2011) has the advantage of automatically tracking the same local surface element on a series of images. The analysis proceeds with the determination of the global Hapke and other standard photometric parameters as well as their two-dimensional variations across the surface. This allows defining, in the body-fixed reference frame, "high residual regions" (HRRs) which correspond to significant relative differences between the observed and modeled photometric parameters such as the singlescattering albedo (SSA), the mean roughness slope angle, and the reflectivity gradient. Title: Plateau de Bure observations of the methanol in 103P/Hartley Authors: Boissier, J.; Bockelée-Morvan, D.; Biver, N.; Crovisier, J.; Colom, P.; Lellouch, E.; Moreno, R.; Groussin, O.; Jorda, L.; Lamy, P. Bibcode: 2011epsc.conf..985B Altcode: 2011DPS....43..985B The comet 103P/Hartley 2 made a close approach to the Earth in October 2010, down to a distance of 0.12 AU. In early November, the Deep Impact spacecraft performed a flyby of the comet, in the framework of its extended mission Epoxi [1]. It has been the target of various observing campaigns at all wavelengths involving ground- and space-based observatories [2]. We present here the results of observations performed with the IRAM Plateau de Bure. We observed the emission of several methanol lines from which we built the methanol rotation diagram and measured the rotational temperature in the coma. The interferometric maps have a spatial resolution of few arcseconds, corresponding to few hundred kilometers. Combined to single dish observations these data allow the measurement of the temperature profile in the coma. In addition, other coma properties can be investigateded from our data set such as the origin of methanol in the coma, the coma structure and its time variability. Title: Asteroid 21 Lutetia: Low Mass, High Density Authors: Pätzold, M.; Andert, T. P.; Asmar, S. W.; Anderson, J. D.; Barriot, J. -P.; Bird, M. K.; Häusler, B.; Hahn, M.; Tellmann, S.; Sierks, H.; Lamy, P.; Weiss, B. P. Bibcode: 2011Sci...334..491P Altcode: Asteroid 21 Lutetia was approached by the Rosetta spacecraft on 10 July 2010. The additional Doppler shift of the spacecraft radio signals imposed by 21 Lutetia’s gravitational perturbation on the flyby trajectory were used to determine the mass of the asteroid. Calibrating and correcting for all Doppler contributions not associated with Lutetia, a least-squares fit to the residual frequency observations from 4 hours before to 6 hours after closest approach yields a mass of (1.700 ± 0.017) × 1018 kilograms. Using the volume model of Lutetia determined by the Rosetta Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) camera, the bulk density, an important parameter for clues to its composition and interior, is (3.4 ± 0.3) × 103 kilograms per cubic meter. Title: A new 3D reconstruction method of small solar system bodies Authors: Capanna, C.; Jorda, L.; Lamy, P.; Gesquiere, G. Bibcode: 2011epsc.conf..945C Altcode: 2011DPS....43..945C The 3D reconstruction of small solar system bodies consitutes an essential step toward understanding and interpreting their physical and geological properties. We propose a new reconstruction method by photoclinometry based on the minimization of the chisquare difference between observed and synthetic images by deformation of a 3D triangular mesh. This method has been tested on images of the two asteroids (2867) Steins and (21) Lutetia observed during ESA's ROSETTA mission, and it will be applied to elaborate digital terrain models from images of the asteroid (4) Vesta, the target of NASA's DAWN spacecraft. Title: A Global Two-Temperature Corona and Inner Heliosphere Model: A Validation Study Authors: Jin, Meng; Manchester, W. B.; van der Holst, B.; Gruesbeck, J.; Frazin, R. A.; Vasquez, A. M.; Lamy, P. L.; Llebaria, A.; Fedorov, A.; Toth, G.; Gombosi, T. I. Bibcode: 2011shin.confE..12J Altcode: The recent solar minimum with very low activity provides us a unique opportunity for validating solar wind models. During CR2077 (2008, November 20 through December 17), the sunspots number reaches the absolute minimum of solar cycle 23. For this solar rotation, we perform a multi-spacecraft validation study for the recently developed three-dimensional, two-temperature, Alfven-wave-driven global solar wind model (a component within the Space Weather Modeling Framework). By using in situ observations from STEREO A and B, ACE/WIND and Venus Express, we compare the observed proton state (density, temperature and velocity) and magnetic field of the heliosphere with that predicted by the model. Near the Sun, we validate the numerical model with the electron density obtained from the solar rotational tomography of SOHO/LASCO-C2 data in the range of 2.4 to 6 solar radii. Electron temperature and density are determined from differential emission measure tomography of STEREO A and B EUVI data in the range of 1.035 to 1.225 solar radii. Moreover, we compare ionic charge states of carbon, oxygen, silicon, and iron observed in situ with ACE/SWICS and that predicted by our model. The validation results suggest that most of the model outputs for CR2077 can fit the observations very well. Based on this encouraging result, we therefore expect great improvement for the modeling of CMEs and CME-driven shocks in the future. Title: The properties of asteroid (2867) Steins from Spitzer Space Telescope observations and OSIRIS shape reconstruction Authors: Groussin, O.; Lamy, P.; Fornasier, S.; Jorda, L. Bibcode: 2011A&A...529A..73G Altcode: 2011arXiv1104.5328G
Aims: We report on the thermal properties and composition of asteroid (2867) Steins derived from an analysis of new Spitzer Space Telescope (SST) observations performed in March 2008, in addition to previously published SST observations performed in November 2005.
Methods: We consider the three-dimensional shape model and photometric properties derived from OSIRIS images obtained during the flyby of the Rosetta spacecraft in September 2008, which we combine with a thermal model to properly interpret the observed SST thermal light curve and spectral energy distributions.
Results: We obtain a thermal inertia of 100 ± 50 J K-1 m-2 s-1/2 and a beaming factor (roughness) in the range 0.7-1.0. We confirm that the infrared emissivity of Steins is consistent with an enstatite composition. The November 2005 SST thermal light curve is most reliably interpreted by assuming inhomogeneities in the thermal properties of the surface, with two different regions of slightly different roughness, as observed on other small bodies, such as the nucleus of comet 9P/Tempel 1. Our results emphasize that the shape model is important to an accurate determination of the thermal inertia and roughness. Finally, we present temperature maps of Steins, as seen by Rosetta during its flyby, and discuss the interpretation of the observations performed by the VIRTIS and MIRO instruments. Title: Earth-based detection of the millimetric thermal emission from the nucleus of comet 8P/Tuttle Authors: Boissier, J.; Groussin, O.; Jorda, L.; Lamy, P.; Bockelée-Morvan, D.; Crovisier, J.; Biver, N.; Colom, P.; Lellouch, E.; Moreno, R. Bibcode: 2011A&A...528A..54B Altcode: 2011arXiv1101.3415B Context. Little is known about the physical properties of cometary nuclei. Measuring the thermal emission of a nucleus is one of the few means of deriving its size, independently of its albedo, and constraining some of its thermal properties. This emission is difficult to detect from Earth but space telescopes, such as th Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory, allow reliable measurements to be made in the infrared and the sub-millimetre domains.
Aims: We attempt to characterize more accurately the thermal properties of the nucleus of comet 8P/Tuttle using multiwavelength space- and ground-based observations, in the visible, infrared, and millimetre range.
Methods: We used the Plateau de Bure Interferometer to measure the millimetre thermal emission of comet 8P/Tuttle at 240 GHz (1.25 mm) and analysed the observations with the shape model derived from Hubble Space Telescope observations and the nucleus size derived from Spitzer Space Telescope observations.
Results: We report on the first detection of the millimetre thermal emission of a cometary nucleus since comet C/1995 O1 Hale-Bopp in 1997. Using the two contact-sphere shape model derived from Hubble Space Telescope observations, we constrain the thermal properties of the nucleus. Our millimetre observations are most accurately reproduced by assuming: i) a thermal inertia lower than ~10 J K-1 m-2 s-1/2, and ii) an emissivity lower than 0.8, which is indicative of a non-negligible contribution of the colder sub-surface layers to the outcoming millimetre flux.

Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). Title: Properties of the nuclei and comae of 10 ecliptic comets from Hubble Space Telescope multi-orbit observations Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; A'Hearn, M. F.; Jorda, L. Bibcode: 2011MNRAS.412.1573L Altcode: 2011MNRAS.tmp..381L We report on our on-going effort to detect and characterize cometary nuclei with the Hubble Space Telescope (HST). During cycle 9 (2000 July to 2001 June), we performed multi-orbit observations of 10 ecliptic comets with the Wide Field Planetary Camera 2. Nominally, eight contiguous orbits covering a time interval of ∼11 h were devoted to each comet but a few orbits were occasionally lost. In addition to the standard R band, we could additionally observe four of them in the V band and the two brightest ones in the B band. Time series photometry was used to constrain the size, shape and rotational period of the 10 nuclei. Assuming a geometric albedo of 0.04 for the R band, a linear phase law with a coefficient of 0.04 mag deg-1 and an opposition effect similar to that of comet 19P/Borrelly, we determined the following mean values of the effective radii 47P/Ashbrook-Jackson: 2.86±0.08 km, 61P/Shajn-Schaldach: 0.62±0.02 km, 70P/Kojima: 1.83±0.05 km, 74P/Smirnova-Chernykh: 2.23±0.04 km, 76P/West-Kohoutek-Ikemura: 0.30±0.02 km, 82P/Gehrels 3: 0.69±0.02 km, 86P/Wild 3: 0.41±0.03 km, 87P/Bus: 0.270.01 km, 110P/Hartley 3: 2.15±0.04 km and 147P/Kushida-Muramatsu: 0.21±0.01 km. Because of the limited time coverage (∼11 h), the rotational periods could not be accurately determined, multiple solutions were sometime found and three periods were not constrained at all. Our estimates range from ∼5 to ∼32 h. The lower limits for the ratio a/b of the semi-axis of the equivalent spheroids range from 1.10 (70P) to 2.20 (87P). The four nuclei for which we could measure (V-R) are all significantly redder than the Sun, with 86P/Wild 3 (V-R) = 0.86 ± 0.10 appearing as an ultrared object. We finally determined the dust activity parameter Afρ of their coma in the R band, the colour indices and the reflectivity spectra of four of them. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-26555. Title: Physical Properties of Craters on Asteroid (21) Lutetia Authors: Vincent, J. -B.; Marchi, S.; Besse, S.; Böhnhardt, H.; Sierks, H.; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.; Cremonese, G.; da Deppo, V.; Davidsson, B.; Debei, S.; de Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P.; Hviid, S. F.; Ip, W. -H.; Keller, H. U.; Kramm, J. R.; Knollenberg, J.; Koschny, D.; Kuehrt, E.; Kueppers, M.; Lamy, P.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Magrin, S.; Marzari, F.; Massironi, M.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K. -P. Bibcode: 2011LPI....42.2417V Altcode: This abstract presents the physical properties of craters derived from the measurement of depth/diameter ratios on asteroid (21) Lutetia. We show how the d/D ratio varies in different regions and how it can be used to better understand the processes that affected the surface. Title: Partition of Proton and Electron Heating in the Solar Wind (Invited) Authors: van der Holst, B.; Jin, M.; Manchester, W. B.; Frazin, R. A.; Vasquez, A. M.; Lamy, P. L.; Llebaria, A.; Gombosi, T. I. Bibcode: 2010AGUFMSH41E..01V Altcode: The electron and proton temperature profiles in the solar wind are very nonadiabatic so that additional heat deposition is needed for both species. A possible heating source is the Kolmogorov-like dissipation of the Alfvén waves. It is still an open issue how turbulence partitions the heat between the electrons and protons (see, e.g., Stawarz et al., 2009 and Breech et al., 2009). Comparison of empirical electron temperature, derived from differential emission measure tomography (DEMT) applied to STEREO A and B EUVI images, with numerical solar wind models allows us to constrain this heating partition. The DEMT results cover the height range 1.035 to 1.225 Rsun. The densities are compared to the solar rotational tomography on LASCO-C2 data of SOHO to further constrain the wind acceleration and heating models. We specifically analyze the periods of Carrington rotations 2077 and 2095. We use the recently developed three-dimensional two-temperature solar wind model within the Space Weather Modeling Framework (SWMF), which includes the anisotropic electron thermal heat conduction, and the collisional heat transfer between the electrons and protons. The solar wind is assumed to be accelerated by the Alfvén waves, and we use Kolmogorov dissipation of these waves to heat both the protons and electrons. Title: Testing Coronal and Solar Wind MHD Models with UV Spectroscopic and Visible Light Coronagraph Data Authors: Strachan, L.; Panasyuk, A.; Kohl, J. L.; Woolsey, L.; Lamy, P. L. Bibcode: 2010AGUFMSH42A..08S Altcode: We present synoptic maps of coronal outflow velocities obtained at 2.3 Rs in the solar wind acceleration region of the corona during Solar Cycle 23. The outflow velocities are obtained by using data from the SOHO coronagraphs: H I Lyman alpha and O VI line profiles (from UVCS) and white light polarized brightness data (from LASCO). The information contained in the maps provide constraints on the electron densities, bulk outflow speeds, and anisotropic kinetic temperatures (velocity distributions for protons and minor ions. We show some examples of how these data can be used to test MHD models of the solar corona and solar wind. The data set can be used to compare empirically derived plasma parameters directly with the MHD model parameters or alternatively it can be used to compare the observed profiles with synthetic profiles obtained by forward modeling of the MHD data. Title: Multispacecraft Validation of a Global Two-Temperature Corona and Inner Heliosphere Model (Invited) Authors: van der Holst, B.; Jin, M.; Manchester, W. B.; Frazin, R. A.; Vasquez, A. M.; Lamy, P. L.; Llebaria, A.; Gombosi, T. I. Bibcode: 2010AGUFMSH42A..05V Altcode: During the recent solar minimum, the two STEREO spacecrafts have imaged many Corotating Interaction Regions (CIRs) in the interplanetary medium. The multi-spacecraft view of the CIRs during this period of very low activity is a unique opportunity for validating solar wind models. According to the National Oceanic and Atmospheric Administration Space Weather Prediction Center the absolute minimum of Sunspots number for solar cycle 23 happened during CR2077 (2008, November 20 through December 17). We use this rotation to perform a multi-spacecraft validation study for a recently developed three-dimensional two-temperature and Alfvén wave driven global solar wind model within the Space Weather Modeling Framework (SWMF). We compare the CIRs of this model with in situ STEREO A and B, ACE/WIND as well as Venus Express. Near the Sun, we validate the numerical model with the density obtained from the solar rotational tomography on LASCO-C2 data of SOHO in the height range of 2.4 to 6 Rsun and electron temperature and density from differential emission measure tomography on STEREO A and B EUVI images in the height range of 1.035 to 1.225 Rsun. Title: Imaging Asteroid (21) Lutetia with OSIRIS onboard Rosetta (Invited) Authors: Keller, H.; Barbieri, C.; Koschny, D.; Lamy, P. L.; Rickman, H.; Rodrigo, R.; Sierks, H.; OSIRIS Team Bibcode: 2010AGUFM.P14B..02K Altcode: The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS observed the asteroid (21) Lutetia during the fly-by of ESA’s Rosetta spacecraft on 10. July 2010. Observations with the narrow angle (NAC) and wide angle (WAC) cameras covered a large phase angle range (from 10 deg during approach through near zero reaching almost 150 deg after closest approach (CA)). The large field of view (2048 x 2048 pixels) of the narrow angle camera (NAC) was almost filled by the 100 km sized body at CA from a distance of 3160 km providing a scale of 60 m per pixel. The rugged body of (21) Lutetia appears to be shaped by an extensive collision history resulting in crater diameters comparable to the mean radius of the asteroid. Most of the visible northern hemisphere is scarred by numerous craters and therefore geologically old. However, several recent large impacts have covered their surroundings with thick layers of regolith. In addition to a wide variety of crater shapes a large diversity of geological features can be discerned: ridges, grabens, pits, landslides, talus, and boulders (> 150 m) and boulder tracks. Grooves are pervasive, radially aligned or concentric around recent craters, often cutting older craters indicating strong seismic activity caused by frequent impacts. In contrast to the observations of asteroid (2867) Steins weak variations of the surface albedo and colour variegations can be discerned and correlated with surface features. The observed opposition effect will constrain the properties of the regolith such as its grain size. The spectrum of Lutetia over the wavelength range of 250 to 1000 nm covered by the filters of the WAC and NAC is flat and hence Lutetia does not appear as red as Steins. Detailed photometric modeling taking advantage of the wide range of phase angles and spectral coverage will be combined and iterated with digital terrain models to describe the surface topography down to the resolution limit of the images and the overall shape to Lutetia. Title: Multi-color, rotationally resolved photometry of asteroid 21 Lutetia from OSIRIS/Rosetta observations Authors: Lamy, P. L.; Faury, G.; Jorda, L.; Kaasalainen, M.; Hviid, S. F. Bibcode: 2010A&A...521A..19L Altcode: Context. Asteroid 21 Lutetia is the second target of the Rosetta space mission. Extensive pre-encounter, space-, and ground-based observations are being performed to prepare for the flyby in July 2010.
Aims: The aim of this article is to accurately characterize the photometric properties of this asteroid over a broad spectral range from the ultraviolet to the near-infrared and to search for evidence of surface inhomogeneities.
Methods: The asteroid was imaged on 2 and 3 January 2007 with the Narrow Angle Camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) during the cruise phase of the Rosetta spacecraft. The geometric conditions were such that the aspect angle was 44^circ (i.e., mid-northern latitudes) and the phase angle 22.4^circ. Lutetia was continuously monitored over 14.3 h, thus exceeding one rotational period and a half, with twelve filters whose spectral coverage extended from 271 to 986 nm. An accurate photometric calibration was obtained from the observations of a solar analog star, 16 Cyg B.
Results: High-quality light curves in the U, B, V, R and I photometric bands were obtained. Once they were merged with previous light curves from over some 45 years, the sidereal period is accurately determined: Prot = 8.168271 ± 0.000002 h. Color variations with rotational phase are marginally detected with the ultraviolet filter centered at 368 nm but are absent in the other visible and near-infrared filters. The albedo is directly determined from the observed maximum cross-section obtained from an elaborated shape model that results from a combination of adaptive-optics imaging and light curve inversion. Using current solutions for the phase function, we find geometric albedos pV = 0.130 ± 0.014 when using the linear phase function and pV(H-G) = 0.180 ± 0.018 when using the (H-G) phase function, which incorporates the opposition effect. The spectral variation of the reflectance indicates a steady decrease with decreasing wavelength rather than a sharp fall-off.

Photometric tables (Tables 4 to 8) are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/521/A19 Title: Visible-wavelength Observations of Jupiter-family Comet Nuclei as Part of Seppcon. Authors: Pittichova, Jana; Lowry, S. C.; Laird, R.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.; Fernández, Y.; Fitzsimmons, A.; Groussin, O.; Hsieh, H.; Kelley, M.; Lamy, P.; Licandro, J.; Lisse, C. M.; Meech, K. J.; Reach, W. T.; Snodgrass, C.; Toth, I.; Weaver, H. A.; Weaissman, P. Bibcode: 2010DPS....42.2826P Altcode: 2010BAAS...42..964P We present the latest analysis and results from SEPPCoN (Survey of Ensemble Physical Properties of Cometary Nuclei). This on-going survey involves studying 100 JFCs - about 25% of the known population - at both mid-infrared and visible wave-lengths to constrain the distributions of sizes, shapes, spins, and albedos of this population. Having earlier reported results from measuring thermal emissions of our sample nuclei [1,2,3,4], we report here progress on the visible-wavelength observations that we have obtained at many ground-based facilities in Chile, Spain, and the United States. To date we have attempted observations of 91% of our sample of 100 JFCs, and at least 64 of those were successfully detected. In most cases the comets were at heliocentric distances between 3.0 and 6.5 AU so as to decrease the odds of a comet having a coma. Of the 64 detected comets, 48 were apparently bare, having no extended emission. Our datasets are further augmented by archival data and photometry from the NEAT program [5]. An important goal of SEPPCoN is to accumulate a large comprehensive set of high quality physical data on cometary nuclei in order to make accurate statistical comparisons with other minor-body populations such as Trojans, Centaurs, and Kuiper-belt objects. Information on the size, shape, spin-rate, albedo and color distributions is critical for understanding their origins and evolutionary processes affecting them.

This work was supported in part by grants from NASA (NNX09AB44G) and NSF (AST-0808004).

[1] Fernandez, Y., et al. 2008, Asteroids Comets Mete-ors 2008, LPI Co. No. 1405, paper id. 8307.

[2] Kelley, M., et al. 2008, Asteroids Comets Meteors 2008, LPI Co. No. 1405, paper id. 8272.

[3] Groussin, O., et al. 2009, Icarus 199, 568.

[4] Licandro, J., et al. 2009, A&A 507, 1667.

[5] Bauer, J., et al. 2010, AAS Meeting 216, paper 409.01. Title: A collision in 2009 as the origin of the debris trail of asteroid P/2010A2 Authors: Snodgrass, Colin; Tubiana, Cecilia; Vincent, Jean-Baptiste; Sierks, Holger; Hviid, Stubbe; Moissi, Richard; Boehnhardt, Hermann; Barbieri, Cesare; Koschny, Detlef; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; Carry, Benoit; Lowry, Stephen C.; Laird, Ryan J. M.; Weissman, Paul R.; Fitzsimmons, Alan; Marchi, Simone; OSIRIS Team Bibcode: 2010Natur.467..814S Altcode: 2010arXiv1010.2883S The peculiar object P/2010A2 was discovered in January 2010 and given a cometary designation because of the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized class of main-belt comets. If confirmed, this new object would expand the range in heliocentric distance over which main-belt comets are found. Here we report observations of P/2010A2 by the Rosetta spacecraft. We conclude that the trail arose from a single event, rather than a period of cometary activity, in agreement with independent results. The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around 10 February 2009. Title: VizieR Online Data Catalog: 21 Lutetia UBVRI light curves (Lamy+, 2010) Authors: Lamy, P.; Faury, G.; Jorda, L.; Kaasalainen, M.; Hviid, S. F. Bibcode: 2010yCat..35210019L Altcode: 2010yCat..35219019L The asteroid was imaged on 2 and 3 January 2007 with the Narrow Angle Camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) during the cruise phase of the Rosetta spacecraft. The geometric conditions were such that the aspect angle was 44° (i.e., mid-northern latitudes) and the phase angle 22.4°. Lutetia was continuously monitored over 14.3h, thus exceeding one rotational period and a half, with twelve filters whose spectral coverage extended from 271 to 986nm. An accurate photometric calibration was obtained from the observations of a solar analog star, 16 Cyg B.

(5 data files). Title: The P/2010 A2 Asteroid Collision Confirmed by Rosetta/OSIRIS Observation Authors: Snodgrass, Colin; Tubiana, C.; Vincent, J.; Sierks, H.; Hviid, S.; Moissl, R.; Boehnhardt, H.; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman, H.; Rodrigo, R.; Carry, B.; Lowry, S. C.; Laird, R. J. M.; Weissman, P. R.; Fitzsimmons, A.; Marchi, S.; OSIRIS Team Bibcode: 2010DPS....42.3933S Altcode: The discovery of P/2010 A2 by the LINEAR survey in January 2010 revealed an object displaying a large trail of material similar in shape to a cometary tail although no central condensation or coma could be detected. The appearance of this object in an asteroidal orbit in the inner main belt attracted attention as a potential new member of the Main Belt Comets class (MBCs) but the discovery of a nucleus, with an estimated diameter of 120 m, around 1500 km away from the trail implied that the extended object we were seeing could be the debris trail from a recent collision rather than the tail of a comet. Due to the low inclination of its orbit, it is difficult to conclude about the nature of P/2010 A2 from Earth-based data only, as different scenarios lead to the same appearance in the orbital configuration at the times of observations. We present here another set of images, acquired from the unique viewing geometry provided by ESA's Rosetta spacecraft en route to comet 67P/Churyumov-Gerasimenko. Albeit faint (22 magnitude), the object could be observed by the high-resolution camera OSIRIS. We used a Finson-Probstein model to simulate the shape of the trail, and estimate the time of emission and β parameter (ratio between solar radiation pressure and gravity) for the dust grains. Simulations were compared to the OSIRIS images and ground based observations acquired at NTT and Palomar telescopes. Thanks to the different phase angle provided by Rosetta, we could reduce the number of solutions to a unique model, leading to the conclusive demonstration that the trail is due to a single event rather than a period of cometary activity. Title: Properties And Distribution Of The Craters Of Asteroid (21) Lutetia From The Rosetta\Osiris Fly-by Authors: Besse, Sebastien; Lamy, P.; Jorda, L.; Groussin, O.; Marchi, S.; Debei, S.; Da Deppo, V.; Ferri, F.; Keller, H. U.; Kueppers, M.; Massironi, M.; Moissl, R.; Sierks, H.; Thomas, N.; Tubiana, C.; Vincent, J.; OSIRIS Team Bibcode: 2010DPS....42.3903B Altcode: 2010BAAS...42R1032B The Rosetta spacecraft of the European Space Agency performed successfully its second flyby of an asteroid on July 10 2010 on its way to its final target comet 67p/Churyumov-Gerasimenko. Main belt asteroid (21) Lutetia has been observed by the OSIRIS experiment at a distance of 3160 km. The best resolution of the images is about 59 meters per pixel, numerous geological features can be distinguished at this scale. We report on here the physical characteristics and properties of the craters of the largest (100km in diameter) asteroid ever observed in-situ. The values of the diameter and the depth of the craters are essential to determine the age of the surface based on crater counting and the evolution of the surface. Preliminary observations already attest for a highly impacted surface with very large craters. Displacement of regolith is seen on the surface and especially in the walls of craters. The properties of the craters will help understand the history and evolution of this large scale and possible primordial body. Title: Hints on the Puzzling 21 Lutetia Nature from OSIRIS Rosetta Data Authors: Barucci, Maria Antonieta; Sierks, H.; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman, H.; Rodrigo, R.; Keller, U. H.; OSIRIS Team Bibcode: 2010DPS....42.4301B Altcode: 2010BAAS...42.1043B From the ground based observations, 21 Lutetia appeared to be a puzzling asteroid different from all the other asteroids. Its nature was uncertain because of contradictory observations, either favoring an M type or a C type asteroid. From polarimetry (Belskaya et al. 2010, AA, 515, 29), Lutetia appeared an atypical object with a surface covered by a fine-grained regolith.

From the amazing images received by OSIRIS imaging system (Keller et al. 2007 SSRev. 128, 433), on board of ESA Rosetta spacecraft, Lutetia reveals a complex and morphologically diverse surface.

Lutetia seems to be a very old object with an irregular shape which is the result of its collisional history. Some smooth younger areas have been also observed. The asteroid lifelong bombardment produced several big craters (tens of kilometers), and many different generations of smaller craters. An apparently thick regolith layer probably covers most of the surface of the asteroid and its presence is revealed by the unique land slide structures along the walls of some craters, most likely generated by impact-induced seismic activity. The presence inside some big craters of sparse boulders, apparently dark, indicates a complex impact mechanism. Moreover images display a great richness of different structures: pits, craters chains, ridges, scarps and wide younger terrains. More details will be available at the time of the presentation. An overview of the obtained results will be presented.

The first analysis of the data shows the extreme diversity of Lutetia which does not resemble any other space explored asteroid. The variety of shapes, morphologies, structures, histories provides us with an invaluable patrimony of information. Title: Shape and Physical Properties of Asteroid 21 Lutetia from OSIRIS Images Authors: Jorda, Laurent; Lamy, P.; Besse, S.; Capanna, C.; Carry, B.; Faury, G.; Gaskell, R.; Gesquière, G.; Groussin, O.; Gutiérrez, P.; Kaasalainen, M.; Sabolo, W.; Sierks, H.; Spjuth, S.; OSIRIS Team Bibcode: 2010DPS....42.4303J Altcode: 2010BAAS...42.1043J The Rosetta spacecraft of the European Space Agency flew by the asteroid 21 Lutetia on July, 10, 2010 on its way to its final target, comet 67P/Churyumov-Gerasimenko. A total of 460 images have been acquired by OSIRIS during the flyby, with a minimum pixel scale of 64 m at closest approach (hereafter "CA") with the narrow angle camera. Several filters have been used, covering a wavelength range from the far UV (0.25 microns) to the end of the visible spectrum (1.0 microns). The phase angle went through 11°-0°-160°, reaching opposition 18 min before CA. We report here on a preliminary interpretation of the images of the asteroid acquired by OSIRIS, the imaging system aboard Rosetta. These images are combined with pre-flyby light curves and adaptive optics measurements to retrieve the shape and the rotational parameters of the asteroid. The bulk physical properties: size, surface, volume, moments of inertia, gravity field, are then extracted from the shape. Title: Thermal properties of asteroids 21 Lutetia and 2867 Steins from Spitzer Space Telescope observations Authors: Groussin, O.; Lamy, P. L.; Fornasier, S.; Jorda, L.; Kaasalainen, M.; Carry, B. Bibcode: 2010epsc.conf...55G Altcode: No abstract at ADS Title: Hektor : a space mission towards Jupiter Trojans Authors: Lamy, P.; Poncy, J.; Martinot, V.; Jorda, L.; Delsanti, A.; Groussin, O. Bibcode: 2010epsc.conf..138L Altcode: No abstract at ADS Title: Asteroid collision confirmed by Rosetta/OSIRIS observations Authors: Vincent, J. -B.; Snodgrass, C.; Tubiana, C.; Sierks, H.; Hviid, S.; Moissl, R.; Böhnhardt, H.; Barbieri, C.; Koschny, D.; Lamy, P. Bibcode: 2010epsc.conf..634V Altcode: No abstract at ADS Title: 21 Lutetia: Overview of results from OSIRIS images Authors: Sierks, H.; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman, H.; Rodrigo, R.; OSIRIS Team Bibcode: 2010epsc.conf..664S Altcode: No abstract at ADS Title: The shape and physical properties of asteroid 2867 Steins from OSIRIS images Authors: Lamy, P.; Jorda, L.; Spjuth, S.; Besse, S.; Marchi, S.; Barbieri, C.; Gaskell, R.; Groussin, O.; Kaasalainen, M.; Keller, H. U. Bibcode: 2010epsc.conf..204L Altcode: No abstract at ADS Title: THERMAP: a thermal infrared spectro-imager for space missions to small bodies of the solar system Authors: Brageot, E.; Groussin, O.; Lamy, P.; Reynaud, J. -L.; Fargant, G. Bibcode: 2010epsc.conf...51B Altcode: No abstract at ADS Title: Restitution of multiple overlaid components on extremely long series of solar corona images Authors: Llebaria, A.; Loirat, J.; Lamy, P. Bibcode: 2010ada..confE..12L Altcode: No abstract at ADS Title: The shape and physical properties of asteroid 21 Lutetia from OSIRIS images Authors: Jorda, L.; Lamy, P.; Besse, S.; Capanna, C.; Carry, B.; Faury, G.; Gaskell, R.; Gesquiere, G.; Groussin, O.; Kaasalainen, M. Bibcode: 2010epsc.conf..200J Altcode: No abstract at ADS Title: Three-Dimensional Electron Density from Tomographic Analysis of LASCO-C2 Images of the K-Corona Total Brightness Authors: Frazin, Richard A.; Lamy, Philippe; Llebaria, Antoine; Vásquez, Alberto M. Bibcode: 2010SoPh..265...19F Altcode: 2010SoPh..tmp...79F We present the first quantitative three-dimensional (3D) tomographic reconstructions of electron density from coronagraph measurements of the K-corona's total brightness (B) made by LASCO-C2 on SOHO. This is possible because new calibrations of the LASCO-C2 images in both polarized brightness (pB) and B have now been made for the entire mission. The B and pB reconstructions are compared, and the differences are explained in terms of line of sight weighting functions in Thomson scattering. We conclude that the LASCO-C2 B archive, which is vastly larger than the pB archive, will be a very valuable resource for determining the 3D electron density throughout the SOHO mission which started taking data in 1996. Title: Analytic and experimental determination of ghosts in the Rosetta Narrow-Angle Camera and their impact on imaging performance Authors: Dohlen, Kjetil; Jorda, Laurent; Lamy, Philippe; Toth, Imre; Origne, Alain Bibcode: 2010SPIE.7731E..49D Altcode: 2010SPIE.7731E.138D The Rosetta cometary rendezvous mission, one of ESA's cornerstone missions, was launched in 2004 and will be inserted in orbit around comet 67P/Churyumov-Gerasimenko in 2014. One of its instruments, the Osiris Narrow Angle Camera (NAC), will take high-resolution images of the comet and map its nucleus as well as the jets of gas and dust emanating from localized areas. This is quite challenging as the contrast between the radiance of these jets and that of the nucleus is expected to be of the order of 1/1000. A major limitation comes from the presence of multiple ghosts which results from the presence of two filters and a protective window in front of the CCD detector. Rigorous knowledge of these instrumental ghost images is therefore required. We present analytical models of the structure and intensity of these ghosts, compare them with pre and post-launch observations, and describe image analysis tools developed to handle them. Title: The cratering history of asteroid (2867) Steins Authors: Marchi, S.; Barbieri, C.; Küppers, M.; Marzari, F.; Davidsson, B.; Keller, H. U.; Besse, S.; Lamy, P.; Mottola, S.; Massironi, M.; Cremonese, G. Bibcode: 2010P&SS...58.1116M Altcode: 2010arXiv1003.5655M The cratering history of main belt asteroid (2867) Steins has been investigated using OSIRIS imagery acquired during the Rosetta flyby that took place on the 5th of September 2008. For this purpose, we applied current models describing the formation and evolution of main belt asteroids, that provide the rate and velocity distributions of impactors. These models coupled with appropriate crater scaling laws, allow the cratering history to be estimated. Hence, we derive Steins' cratering retention age, namely the time lapsed since its formation or global surface reset. We also investigate the influence of various factors - like bulk structure and crater erasing - on the estimated age, which spans from a few hundred Myrs to more than 1 Gyr, depending on the adopted scaling law and asteroid physical parameters. Moreover, a marked lack of craters smaller than about 0.6 km has been found and interpreted as a result of a peculiar evolution of Steins cratering record, possibly related either to the formation of the 2.1 km wide impact crater near the south pole or to YORP reshaping. Title: Stray light analysis and optimization of the ASPIICS/PROBA-3 formation flying solar coronagraph Authors: Mazzoli, A.; Landini, F.; Vives, S.; Lamy, P.; Halain, J. P.; Rochus, P. Bibcode: 2010SPIE.7731E..46M Altcode: 2010SPIE.7731E.135M PROBA-3 is a technology mission devoted to the in-orbit demonstration of formation flying techniques and technologies. PROBA-3 will implement a giant coronagraph (called ASPIICS) that will both demonstrate and exploit the capabilities and performances of formation flying. ASPIICS is distributed on two spacecrafts separated by 150m, one hosting the external occulting disk and the other the optical part of the coronagraph. This part implements a three-mirror-anastigmat (TMA) telescope. Its pupil is placed about 800mm in front of the primary mirror, a solution allowing an efficient baffling and a high reduction of the stray light inside the instrument. A complete stray light analysis of the TMA has been carried out to design the baffles and to establish the required roughness of the mirrors. The analysis has been performed in two steps: first, by calculating the diffraction pattern behind the occulter due to an extended monochromatic source having the diameter of the Sun; second, by propagating this diffraction pattern, through all the telescope optical components, to the prime focal plane. The results obtained are described in this article. Title: Demonstrator of the formation flying solar coronagraph ASPIICS/PROBA-3 Authors: Vives, Sébastien; Damé, Luc; Lamy, Philippe; Antonopoulos, A.; Bon, W.; Capobianco, G.; Crescenzio, G.; da Deppo, V.; Ellouzi, M.; Garcia, J.; Guillon, C.; Mazzoli, A.; Soilly, T.; Stathopoulos, F.; Tsiganos, C. Bibcode: 2010SPIE.7731E..47V Altcode: 2010SPIE.7731E.136V Formation Flying opens the possibility to conceive and deploy giant solar coronagraphs in space permanently reproducing the optimum conditions of a total eclipse of the Sun ("artificial" eclipse) thus giving access to the inner corona with unprecedented spatial resolution and contrast (low stray light). The first opportunity to implement such a coronagraph "ASPIICS" will be offered by the European Space Agency (ESA) PROBA-3 technology mission devoted to the in-orbit demonstration of formation flying technologies. Two spacecrafts separated by about 150 m form a giant externally-occulted coronagraph: the optical part hosted by one spacecraft remains entirely protected from direct sunlight by remaining in the shadow of an external occulter hosted by the other spacecraft. We developed and tested a scale-model 'breadboard' (i.e., 30m) of the PROBA-3/ASPIICS Formation Flying coronagraph. The investigations focused on two metrology systems capable of measuring both the absolute pointing of the coronagraph (by sensing the projected shadow and penumbra produced by the external occulting disk) and the alignment of the formation (by re-imaging light sources located on the rear-side of the occulting disk with the optical part of the coronagraph). In this contribution, we will describe the demonstrator and report on our results on the crucial question of the alignment and pointing in space of long instruments (> 100 m) with an accuracy of a few arcsec. This study has been conducted in the framework of an ESA "STARTIGER" Initiative, a novel approach aimed at demonstrating the feasibility of a new and promising technology on a very short time scale (six months). Title: ASPIICS: a giant coronagraph for the ESA/PROBA-3 Formation Flying Mission Authors: Lamy, Philippe; Damé, Luc; Vivès, Sébastien; Zhukov, Andrei Bibcode: 2010SPIE.7731E..18L Altcode: 2010SPIE.7731E..31L Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent useful observations of the white light corona inside typically 2-2.5 solar radii. Formation flying offers an elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at a distance of hundred meters. Such an instrument, ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire), has just been selected by the European Space Agency (ESA) to fly (launch expected in 2014) on its third PROBA (Project for On-Board Autonomy) mission of formation flying demonstration which is presently in phase B. It will perform both high spatial resolution imaging of the solar corona as well as 2- dimensional spectroscopy of several emission lines (in particular the forbidden line of FeXIV at 530.285 nm) from the coronal base out to 3 solar radii. For this, it will use filters, polarisers and a solid Fabry-Perot interferometer ("étalon"). The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.04-0.05 solar radii (40-50 arcsec) from the solar limb. By tuning the position of the occulter spacecraft, it may even be possible to reach the chromosphere and the upper part of the spicules. Title: Measurements and optimization of the occulting disk for the ASPIICS/PROBA-3 formation flying solar coronagraph Authors: Landini, Federico; Mazzoli, Alexandra; Venet, Melanie; Vivès, Sébastien; Romoli, Marco; Lamy, Philippe; Rossi, Guglielmo Bibcode: 2010SPIE.7735E..4DL Altcode: 2010SPIE.7735E.146L Solar coronagraphs in formation ying require several mechanical and technological constraints to be met. One of the most critical issues is the external occulter design and its optimization. The occulter edge requires special attention in order to minimize the diraction while being compatible with the constraints of handling and integrating large delicate space components. Moreover, it is practically impossible to realize a full scale model for laboratory tests. This article describes the results of tests performed with a scaled-model breadboard of the ASPIICS coronagraph disk edge, using the Articial Sun facility at Laboratoire d'Astrophysique de Marseille. Title: Towards a New Formation Flying Solar Coronagraph Authors: Lamy, P.; Vives, S.; Curdt, W.; Dame, L.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chieze, S.; Zhukov, A. Bibcode: 2010ASPC..424...15L Altcode: We briefly describe an investigation aiming at the development of a giant solar coronagraph instrument onboard of two satellites, separated by about 150 m in formation flight for the detailed observation of the solar coronal plasma. The European Space Agency (ESA) has selected this instrument as the only payload onboard the Proba 3 satellites which will be launched in 2013. The Greek team is developing the command control board of the coronagraph. Title: The Solar Wind as Seen by SOHO/SWAN Since 1996: Comparison with SOHO/LASCO C2 Coronal Densities Authors: Lallement, R.; Quémerais, E.; Lamy, P.; Bertaux, J. -L.; Ferron, S.; Schmidt, W. Bibcode: 2010ASPC..428..253L Altcode: 2010arXiv1003.4243L We update the SOHO/SWAN H Lyman-α brightness analysis to cover the 1996-2008 time interval. A forward model applied to the intensity maps provides the latitude and time dependence of the interstellar hydrogen ionization rate over more than a full solar cycle. The hydrogen ionization, being almost entirely due to charge-exchange with solar wind ions, reflects closely the solar wind flux. Our results show that the solar wind latitudinal structure during the present solar minimum is strikingly different from the previous minimum, with a much wider slow solar wind equatorial belt which persists until at least the end of 2008. We compute absolute values of the in-ecliptic H ionization rates using OMNI solar wind data and use them to calibrate our ionization rates at all heliographic latitudes. We then compare the resulting fluxes with the synoptic LASCO/C2 electron densities at 6 solar radii. The two time-latitude patterns are strikingly similar over all the cycle. This comparison shows that 6 Rs densities can be used to infer the solar wind type close to its source, with high (low) densities tracing the slow (fast) solar wind, simply because the density reflects the altitude at which the acceleration occurs. The comparison between the two minima suggests that the fast polar wind acceleration occurs at a larger distance during the current minimum compared to the previous one. This difference, potentially linked to the magnetic field decrease and/or the coronal temperature decrease should be reproduced by solar wind expansion models. Title: Thermal properties of asteroid 21 Lutetia from Spitzer Space Telescope observations Authors: Lamy, P. L.; Groussin, O.; Fornasier, S.; Jorda, L.; Kaasalainen, M.; Barucci, M. A. Bibcode: 2010A&A...516A..74L Altcode: Context. Asteroid 21 Lutetia is the second target of the Rosetta space mission with a flyby scheduled in July 2010. To best prepare the observational campaign, Lutetia is being extensively characterized by ground- and space-based astronomical facilities.
Aims: We used the Spitzer Space Telescope (SST) to determine the thermal properties of Lutetia and more generally, to contrain its physical properties and nature.
Methods: The observations were performed with the infrared spectrograph (IRS) of the SST on 10 and 11 December 2005, when the asteroid was 2.81 AU from the Sun, 2.65 AU from the SST and at a phase angle of 21°. We obtained 14 spectra ranging from 5.2 to 38.0 μm, and sampling the rotational period of the asteroid. They were interpreted with a standard thermal model incorporating the thermal inertia.
Results: We obtained the first thermal light curve of Lutetia. Using the most recent solution for its three-dimensional shape and rotational state, as well as independently determined parameters such as the albedo, we satisfactorily reproduced the 14 spectral energy distributions and the complete thermal light curve of Lutetia. The best thermal model has a thermal inertia I ≤ 30 JK-1m-2s-1/2 and a beaming factor in the range ~0.70-0.83. This low thermal inertia is typical of main belt asteroids and implies that the surface of Lutetia is likely covered by a thick regolith layer. Since the beaming factor only reflects the effects of surface rugosity, the above range implies a high degree of roughness. In addition, our results show evidence of inhomogeneities in the surface roughness in the equatorial band of Lutetia. Title: A Hundred Comets: The Visual-Wavelength Observations of the Survey of Ensemble Physical Properties of Cometary Nuclei (SEPPCoN) Authors: Bauer, James M.; Fernandez, Y. R.; Lowry, S. C.; Meech, K. J.; Fitzsimmons, A.; Snodgrass, C.; Pittichova, J.; Weaver, H. A.; Lisse, C. M.; A'Hearn, M. F.; Campins, H.; Groussin, O.; Kelley, M. S.; Lamy, P. L.; Licandro, J.; Reach, W. T.; Toth, I. Bibcode: 2010AAS...21640901B Altcode: 2010BAAS...41..816B We present new results from SEPPCoN, a Survey of Ensemble Physical Properties of Cometary Nuclei. This project is currently surveying 100 Jupiter-family comets (JFCs) to measure the mid-infrared thermal emission and visible reflected sunlight of the nuclei. The scientific goal is to determine the distributions of radius, geometric albedo, thermal inertia, axial ratio, and color among the JFC nuclei. In the past we have presented results from the completed mid-IR observations of our sample [1]; here we present preliminary results from ongoing, broadband visible-wavelength observations of nuclei obtained from a variety of ground-based facilities (Mauna Kea, Cerro Pachon, La Silla, La Palma, Apache Point, Table Mtn., and Palomar Mtn.), including contributions from the Near Earth Asteroid Telescope project (NEAT) archive. The nuclei were observed at high heliocentric distance (usually over 4 AU) and so many comets show either no or little contamination from dust coma. While several nuclei have been observed as snapshots, we have multiepoch photometry for many of our targets. With our datasets we are building a large database of photometry, and such a database is essential to the derivation of albedo and shape of a large number of nuclei, and to the understanding of biases in the survey. Support for this work was provided by NSF and the NASA Planetary Astronomy program. Reference: [1] Fernandez, Y.R., et al. 2007, BAAS 39, 827. Title: The nucleus of comet C/1983 H1 IRAS-Araki-Alcock Authors: Groussin, O.; Lamy, P. L.; Jorda, L. Bibcode: 2010P&SS...58..904G Altcode: We present a synthetic analysis of all available infrared (2-20 μm) and radio (1.3-6.1 cm) observations of comet C/1983 H1 IRAS-Araki-Alcock performed during its close approach to Earth in May 1983. We implement a model based on a spherical nucleus with a macroscopic mosaic of small and numerous active and inactive regions, and take into account the strong phase effect in the calculations of the thermal flux (often neglected in past interpretations). The orientation of the spin axis is assumed to be that determined by Sekanina [1988. Astron. J. 95, 1876-1894]. Additional constraints coming from visible photometry, measurements of the water production rate and the temporal variations of the cometary activity are introduced. We derive an equivalent nucleus radius of 3.4±0.5 km, consistent with a geometric albedo of 0.04 ±0.01 and a phase coefficient β=0.04mag deg in the visible, and an active fraction of 2.9 ±1.9%. Although the nucleus is probably elongated as found in the past ( Sekanina, 1988), we show that the relevant measurements were likely contaminated by the contribution of a variable coma. Title: The solar wind flux and acceleration height as seen by SOHO/SWAN and LASCO/C2 Authors: Lallement, Rosine; Quemerais, Eric; Bertaux, Jean-Loup; Lamy, Philippe; Schmidt, Walter Bibcode: 2010EGUGA..12.8445L Altcode: We present an update of the SOHO/SWAN H Lyman-alpha data to cover the 1996-2009 time interval. A forward model applied to the intensity maps provides the latitude and time dependence of the interstellar H ionisation rate over more than a full solar cycle. This ionisation, being almost entirely due to charge-exchange with solar wind ions, reflects closely the solar wind flux. We show that the solar wind latitudinal structure during the present solar minimum is strikingly different from the previous minimum, with a much wider slow solar wind equatorial belt which persists until at least the end of 2008. After calibration of our 3D ionisation rates on OMNI in-ecliptic data, we compare the resulting solar wind fluxes with the synoptic LASCO/C2 electron densities at 6 Rs. The two time-latitude patterns are strikingly similar over all the cycle, high (resp. low) H ionisation and 6Rs coronal densities tracing the slow (resp. fast) solar wind. This is because the H ionisation reflects the solar wind flux and speed, while the coronal density reflects at which altitude occurs the acceleration. The comparison between the two minima of activity suggests that the high latitude fast wind accelerates at larger distance from the Sun surface during the current minimum compared to the previous one. This difference, potentially linked to the magnetic field decrease or(and) the coronal temperature decrease should be reproduced by solar wind expansion models. Title: The Interstellar H Flow: Updated Analysis of SOHO/SWAN Data Authors: Lallement, Rosine; Quémerais, Eric; Koutroumpa, Dimitra; Bertaux, Jean-Loup; Ferron, Stéphane; Schmidt, Walter; Lamy, Philippe Bibcode: 2010AIPC.1216..555L Altcode: 2014arXiv1405.3474L We update two kinds of results obtained with the SWAN instrument on board SOHO. First, we use H cell data recorded in 2001 and derive the H flow direction in the same way the study was done at solar minimum. We again compare with the Helium flow direction and doing so correct for the coordinate system change between the Ulysses and SOHO missions. The deflection plane we obtain is compatible with our previous result within error bars, confirming the potential predominant role of the interstellar magnetic field. In a second part, we extend the computation of the interstellar H ionization as a function of heliographic latitude and time, a quantity which reflects closely the SW flux latitudinal structure. The pattern for the present solar minimum is strikingly different from the previous minimum, with a much wider slow solar wind equatorial belt which persists until at least 2008. Comparing with synoptic LASCO/C2 electron densities we infer from a preliminary study that the acceleration of the high speed solar wind occurs at a higher altitude during this minimum compared to the previous one, a difference expansion models must be able to reproduce. Title: Photometric Study of the Kreutz Comets Observed by SOHO from 1996 to 2005 Authors: Knight, Matthew M.; A'Hearn, Michael F.; Biesecker, Douglas A.; Faury, Guillaume; Hamilton, Douglas P.; Lamy, Philippe; Llebaria, Antoine Bibcode: 2010AJ....139..926K Altcode: We present analysis of the photometry of more than 900 Kreutz comets observed by SOHO from 1996 to 2005. The Kreutz comets have "sungrazing" orbits with q≈ 1-2 R sun, high inclinations (i ≈ 143°), and periods of 500-1000 years. We find that they do not have a bimodal distance of peak brightness as previously reported, but instead peak from 10.5 R sun to 14 R sun (prior to perihelion), suggesting there is a continuum of compositions rather than two distinct subpopulations. The light curves have two rates of brightening, typically vprop r -7.3 ± 2.0 when first observed by SOHO (at distances of 30-35 R sun) then rapidly transitioning to vprop r -3.8 ± 0.7 between 20 R sun and 30 R sun. It is unclear at what distance the steeper slope begins, but it likely does not extend much beyond the SOHO field of view. We derive nuclear sizes up to ~50 m in radius for the SOHO-observed comets, with a cumulative size distribution of N(>R) vprop R -2.2 for comets larger than 5 m in radius. This size distribution cannot explain the largest members of the family seen from the ground, suggesting that either the size distribution does not extend to the largest sizes or that the distribution is not uniform around the orbit. The total mass of the distribution up to the largest expected size (~500 m) is ~4 × 1014 g, much less than the estimated masses of the largest ground-observed members. After correcting for the changing discovery circumstances, the flux of comets reaching perihelion has increased since 1996, and the increase is seen in comets of all sizes. Comparison of the SOHO comets with the Solwind and Solar Maximum Mission discoveries suggests there may have been an overabundance of bright comets arriving from 1979 to 1989, possibly indicative of a changing distribution around the Kreutz orbit. Title: Coronal Fine Linear Rays: Are They Fast Streams From Active Regions? Authors: Koutchmy, Serge; Lamy, Philippe; Viladrich, Christian; Filippov, Boris; Nikoghossian, Arthur; Golub, Leon Bibcode: 2010AIPC.1216..339K Altcode: Eclipse observations of the W-L corona show linear rays above active regions at times of solar maximum. We show that these linear rays are also observed in the field-of-view of the C2-LASCO coronagraph, in perfect correspondence with the eclipse results. A selected prominent case taken from the 2001 eclipse observation in Angola is analysed with several different methods, including the use of a synoptic map constructed using SoHO/LASCO C2 images. A clear signature of time variations near the eclipse observation is detected, suggesting that at least some parts of the beam are collimated. These observations strongly suggest high speed streams that apparently ignore the potential large scale coronal magnetic field rooted rather low in the corona. A possible origin is the neutral magnetic points located above the active region. Several mechanisms exist to explain how the plasma is accelerated in these regions to large quasi-relativistic velocities, possibly related to the occurrence of type III radio bursts. We point out a curious analogy with phenomena occurring inside coronal holes. Title: Properties of Comet Nuclei Authors: Lamy, P. L.; Toth, I.; Fernandez, Y. R.; Weaver, H. A. Bibcode: 2010PDSS.8122E....L Altcode: This data set presents tables 1, 2, 3, 4, 5 and 7 of 'Sizes, Shapes, Albedos, and Colors of Cometary Nuclei' (Lamy et al., 2004), and includes references for the sources cited. The authors culled this data from published or well-known unpublished sources, and have indicated what they judge to be the most reliable value available. Title: HiRISE Mission to Address the Dynamical Chromosphere-Corona Interface Authors: Damé, Luc; Lamy, Philippe; von Fay-Siebenburgen Erdélyi, Robert Bibcode: 2010cosp...38.2844D Altcode: 2010cosp.meet.2844D Several ground facilities and space missions are currently dedicated to the study of the Sun at high resolution and of the solar corona in particular. However, and despite significant progress with the advent of space missions and UV, EUV and XUV direct observations of the hot chro-mosphere and million degrees coronal plasma, much is yet to be achieved in the understanding of these high temperatures, fine dissipative structures and of the coronal heating in general. Recent missions have shown the definite role of waves and of the magnetic field deep in the inner corona, at the chromosphere-corona interface, where dramatic changes occur. The dynamics of the chromosphere and corona is controlled by the emerging magnetic field, guided by the coronal magnetic field. Accordingly, the direct measurement of the chromospheric and coronal magnetic fields is of prime importance. The solar corona consists of many thin loops or threads with the plasmas brightening and fading independently. The dynamics in each thread is believed to be related to the formation of filaments, each one being dynamic, in a non-equilibrium state. The mechanism sustaining that dynamics, oscillations or waves (Alfvén or MHD?), require both very high-cadence, multi-spectral observations, and high resolution. This is foreseen in the future Space Mission HiRISE, the ultimate new generation ultrahigh resolution, interferomet-ric and coronagraphic, Solar Physics Mission, proposed for ESA Cosmic Vision (pre-selected in 2007, and under preparation for 2012 second call). HiRISE (High Resolution Imaging and Spectroscopy Explorer), at the L1 Lagrangian point, provides meter class FUV imaging and spectro-imaging, EUV and XUV imaging and spectroscopy, and ultimate coronagraphy by a remote external occulter (satellites in formation flying 280 m apart) allowing to characterize temperature, densities and velocities in the solar upper chromosphere, transition zone and inner corona with, in particular, 2D very high resolution multi-spectral imaging-spectroscopy, direct coronal magnetic field measurement: a unique set of tools to understand the structuration and onset of coronal heating. We give a detail account of the proposed mission profile, major scien-tific objectives and model payload of HiRISE, a natural complement to the Solar Probe type missions lacking duty cycle, high resolution, spatial, spectral and temporal multi-temperature diagnostics and full coronal magnetometry. Title: ASPIICS / PROBA-3 formation flying externally-occulted giant coronagraph mission Authors: Lamy, Philippe; Damé, Luc Bibcode: 2010cosp...38.1882L Altcode: 2010cosp.meet.1882L During the time operation of the Helios mission, from 1974 to metricconverterProductID1986, a1986, a large number of magnetic clouds was identified by the magnetic field and solar wind sensors onboard the probes. Among these magnetic clouds, some of them were identified by at least two probes, provided that IMP-8 and ISEE-3 were monitoring the dayside magnetosphere. The magnetic cloud observed on from DOY 029 to DOY 030/1977 by Helios 1, Helios 2, and IMP-8 represents a potential multi-spacecraft observed magnetic cloud. Despite the interaction with the high-speed stream that compressed the magnetic cloud, the minimum variance analysis technique showed the same direction of rotation of the magnetic field inside the magnetic cloud. This helped to associate the observation of the magnetic cloud at multi-spacecraft. Title: ASPIICS / PROBA-3: a formation flying externally-occulted giant coronagraph mission Authors: Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A. Bibcode: 2010cosp...38.2858L Altcode: 2010cosp.meet.2858L Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent useful observa-tions of the white light corona inside typically 2-2.5 Rsun. Formation flying offers an elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs us-ing a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at distances of hundred meters. Such an instrument has just been selected by ESA to fly (by the end of 2013) on its PROBA-3 mission, presently in phase B, to demonstrate formation flying. It will perform both high spatial resolution imaging of the solar corona as well as 2-dimensional spectroscopy of several emission lines (in partic-ular the forbidden line of FeXIV at 530.285 nm) from the coronal base out to 3 Rsun using a Fabry-Perot interferometer. The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.05 Rsun from the solar limb. By tuning the position of the occulter spacecraft, it may even be possible to try reaching the chromosphere and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload and scientific objectives are detailed. Title: Physical properties of asteroid 2867 Steins Authors: Keller, Horst Uwe; Jorda, Laurent; Spjuth, Sofie; Lamy, Philippe; Groussin, Olivier; Schroder, Stefan; Marchi, Simone; Kueppers, Michael; Gaskell, Robert Bibcode: 2010cosp...38..632K Altcode: 2010cosp.meet..632K ESA's spacecraft Rosetta passed the E-type asteroid 2867 Steins on 5. Sept. 2009 on its way to a rendezvous with comet 67P/Churyumov-Gerasimenko. The scientific camera system OSIRIS took several hundred images. The best resolution of 160 m (2 pixel) was achieved at a closest approach of 803 km. The images show an oblate body with an effective spherical diameter of 5.3 km. A large crater of 2.1 km in diameter suggests that Steins is a rubble pile. Its conical shape could be the result of YORP spin-up. A lack of small craters indicates a rather recent resurfacing event. Disk resolved photometry based on a shape model constructed from trian-gular facets and using the formalism of Hapke (1993, 2002) constrains the surface properties. On its inbound leg the spacecraft passed near zero phase angle and the photometry of the op-position effect suggests that both shadow-hiding and coherent backscattering are present. The optically relevant regolith surface of Steins appears to be porous, consisting of fine transparent grains. The geometric albedo calculated from the Hapke parameters can be compared to the value derived directly from the images near zero phase angle. Title: Multi-spacecraft observation of a magnetic cloud Authors: de Lucas, Aline; Dal Lago, Alisson; Schwenn, Rainer; Clúa de Gonzalez, Alicia L.; Marsch, Eckart; Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A. Bibcode: 2010cosp...38.1921D Altcode: 2010cosp.meet.1921D Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent useful observa-tions of the white light corona inside typically 2-2.5 Rsun. Formation flying offers an elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs us-ing a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at distances of hundred meters. Such an instrument has just been selected by ESA to fly (by the end of 2013) on its PROBA-3 mission, presently in phase B, to demonstrate formation flying. It will perform both high spatial resolution imaging of the solar corona as well as 2-dimensional spectroscopy of several emission lines (in partic-ular the forbidden line of FeXIV at 530.285 nm) from the coronal base out to 3 Rsun using a Fabry-Perot interferometer. The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.05 Rsun from the solar limb. By tuning the position of the occulter spacecraft, it may even be possible to try reaching the chromosphere and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload and scientific objectives are presented. Title: Restitution of multiple overlaid components on extremely long series of solar corona images Authors: Llebaria, A.; Loirat, J.; Lamy, P. Bibcode: 2010SPIE.7533E..0YL Altcode: 2010SPIE.7533E..25L This contribution describes the methods used to accurately disentangle the components observed on a very large series of images of the solar corona. This series consists of 12 years of continuous observations provided by the LASCO/C2 coronagraph aboard SOHO (the SOlar and Heliospheric Observatory). Continuously centred on the Sun, which is masked, the observed images display a blend of many components. The more conspicuous are the K-corona from the coronal plasma, the F-corona from the coronal dust and the instrumental straylight. All of them are optically thin but in the LASCO/C2 field of view only the K-corona is polarized. The set of observations is composed of two huge series of images: the "polarization series" (at least one observation every day) and the "white light series" (more than 50 images every day). The goal is to determine quantitatively the evolution of each image component during the 12 years. Assuming 1) a small and slow temporal evolution for the F-corona and straylight, 2) the 2D regularity of the F-corona and 3) the ability to deduce the influence of the SOHO-Sun distance, the F-corona function is determined from the polarized series and afterwards subtracted of the white light series to obtain the K-corona white light series. Title: E-Type Asteroid (2867) Steins as Imaged by OSIRIS on Board Rosetta Authors: Keller, H. U.; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman, H.; Rodrigo, R.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Barucci, M. A.; Bertaux, J. -L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. -M.; Lazzarin, M.; Moreno, J. Lopez; Marzari, F.; Michalik, H.; Naletto, G.; Sabau, L.; Thomas, N.; Wenzel, K. -P.; Bertini, I.; Besse, S.; Ferri, F.; Kaasalainen, M.; Lowry, S.; Marchi, S.; Mottola, S.; Sabolo, W.; Schröder, S. E.; Spjuth, S.; Vernazza, P. Bibcode: 2010Sci...327..190K Altcode: The European Space Agency’s Rosetta mission encountered the main-belt asteroid (2867) Steins while on its way to rendezvous with comet 67P/Churyumov-Gerasimenko. Images taken with the OSIRIS (optical, spectroscopic, and infrared remote imaging system) cameras on board Rosetta show that Steins is an oblate body with an effective spherical diameter of 5.3 kilometers. Its surface does not show color variations. The morphology of Steins is dominated by linear faults and a large 2.1-kilometer-diameter crater near its south pole. Crater counts reveal a distinct lack of small craters. Steins is not solid rock but a rubble pile and has a conical appearance that is probably the result of reshaping due to Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) spin-up. The OSIRIS images constitute direct evidence for the YORP effect on a main-belt asteroid. Title: OASIS: a simulator to prepare and interpret remote imaging of solar system bodies Authors: Jorda, L.; Spjuth, S.; Keller, H. U.; Lamy, P.; Llebaria, A. Bibcode: 2010SPIE.7533E..11J Altcode: 2010SPIE.7533E..28J We present a new tool, called "OASIS" (Optimized Astrophysical Simulator for Imaging Systems), whose aim is to generate synthetic calibrated images of solar system bodies. OASIS has been developed to support the operations and the scientific interpretation of visible images acquired by the OSIRIS visible camera aboard the Rosetta spacecraft, but it can be used to create synthetic images taken by the visible imaging system of any spacecraft. OASIS allows takes as input the shape model of the object, in the form of triangular facets defining its surface, geometric parameters describing the position and orientation of the objects included in the scene and of the observer, and instrumental parameters describing the geometric and radiometric properties of the camera. The rendering of the object is performed in several steps which involve: (i) sorting the triangular facets in planes perpendicular to the direction of the light source and to the direction of the line-of-sight, (ii) tracing rays from a given facet to the light source and to the observer to check if it is illuminated and in view from the observer, (iii) calculating the intersection between the projected coordinates of the facets and the pixels of the image, and finally (iv) radiometrically calibrating the images. The pixels of the final image contain the expected signal from the object in digital numbers (DN). We show in the article examples of synthetic images of the asteroid (2867) Steins created with OASIS, both for the preparation of the flyby and for the scientific interpretation of the acquired images later on. Title: On the 3-D reconstruction of Coronal Mass Ejections using coronagraph data Authors: Mierla, M.; Inhester, B.; Antunes, A.; Boursier, Y.; Byrne, J. P.; Colaninno, R.; Davila, J.; de Koning, C. A.; Gallagher, P. T.; Gissot, S.; Howard, R. A.; Howard, T. A.; Kramar, M.; Lamy, P.; Liewer, P. C.; Maloney, S.; Marqué, C.; McAteer, R. T. J.; Moran, T.; Rodriguez, L.; Srivastava, N.; St. Cyr, O. C.; Stenborg, G.; Temmer, M.; Thernisien, A.; Vourlidas, A.; West, M. J.; Wood, B. E.; Zhukov, A. N. Bibcode: 2010AnGeo..28..203M Altcode: Coronal Mass ejections (CMEs) are enormous eruptions of magnetized plasma expelled from the Sun into the interplanetary space, over the course of hours to days. They can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they collide with the Earth's magnetosphere. It is important to know their real speed, propagation direction and 3-D configuration in order to accurately predict their arrival time at the Earth. Using data from the SECCHI coronagraphs onboard the STEREO mission, which was launched in October 2006, we can infer the propagation direction and the 3-D structure of such events. In this review, we first describe different techniques that were used to model the 3-D configuration of CMEs in the coronagraph field of view (up to 15 R⊙). Then, we apply these techniques to different CMEs observed by various coronagraphs. A comparison of results obtained from the application of different reconstruction algorithms is presented and discussed. Title: PHYSICAL PROPERTIES OF STEINS' CRATERS Authors: Besse, S.; Lamy, P. L.; Marchi, S.; Jorda, L. Bibcode: 2009AGUFM.P11C1235B Altcode: The ROSETTA spacecraft, on its way to rendez-vous comet 67P/Churyumov-Gerasimenko, has successfully flew by asteroid 2867 Steins in September 2008. The OSIRIS experiment (Keller et al, 2007) has imaged the asteroid both with the Wide Angle Camera (WAC) and the Narrow Angle Camera (NAC). The resolutions of the images are sufficient to distinguish features on the surface, especially craters which are detected all over the observed part of the asteroidal surface (44%). In this study, we focus on the physical properties of the craters and particularly theirs diameters and depths which we can compare with others small bodies previously observed. Starting from the first shape model of the asteroid (Besse et al, 2009), we add artificial craters that best match the observations and correlate the simulated images and the real images. The highest correlation yields the diameter and the depth of the craters. The average Depth/Diameter ratio for Steins is 0.12. However, these values are quite heterogeneous and ranged from 0.04 to 0.25. These results are in agreement with previous studies: 0.15 for Ida (Sullivan et al, 1996) and 0.14 for Gaspra (Carr et al,1994). The difference is likely due to the resurfacing of the surface by the large impact that occurs on the south pole of Steins with a diameter of 2100 meters. Craters with extreme values of the Depth/Diameter ratio are located in the vicinity of this large crater and may be related to the large impact. Shallower craters could have been filled by ejecta or regolith displacement, while steeper craters could result from fault basin related to the impact or simply be recent events. Title: Spitzer observations of the asteroid-comet transition object and potential spacecraft target 107P (4015) Wilson-Harrington Authors: Licandro, J.; Campins, H.; Kelley, M.; Fernández, Y.; Delbó, M.; Reach, W. T.; Groussin, O.; Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Bauer, J. M.; Lowry, S. C.; Fitzsimmons, A.; Lisse, C. M.; Meech, K. J.; Pittichová, J.; Snodgrass, C.; Weaver, H. A. Bibcode: 2009A&A...507.1667L Altcode: 2009arXiv0910.0116L Context: Near-Earth asteroid-comet transition object 107P/ (4015) Wilson-Harrington is a possible target of the joint European Space Agency (ESA) and Japanese Aerospace Exploration Agency (JAXA) Marco Polo sample return mission. Physical studies of this object are relevant to this mission, and also to understanding its asteroidal or cometary nature.
Aims: Our aim is to obtain significant new constraints on the surface thermal properties of this object.
Methods: We present mid-infrared photometry in two filters (16 and 22 μm) obtained with NASA's Spitzer Space Telescope on February 12, 2007, and results from the application of the Near Earth Asteroid Thermal Model (NEATM). We obtained high S/N in two mid-IR bands allowing accurate measurements of its thermal emission.
Results: We obtain a well constrained beaming parameter (η = 1.39±0.26) and obtain a diameter and geometric albedo of D = 3.46±0.32 km, and pV = 0.059±0.011. We also obtain similar results when we apply this best-fitting thermal model to single-band mid-IR photometry reported by Campins et al. (1995, P&SS, 43, 733), Kraemer et al. (2005, AJ, 130, 2363) and Reach et al. (2007, Icarus, 191, 298).
Conclusions: The albedo of 4015 Wilson-Harrington is low, consistent with those of comet nuclei and primitive C-, P-, D-type asteorids. We establish a rough lower limit for the thermal inertia of W-H of 60 Jm-2s-0.5 K-1 when it is at r = 1 AU, which is slightly over the limit of 30 Jm-2 s-0.5 K-1 derived by Groussin et al. (2009, Icarus, 199, 568) for the thermal inertia of the nucleus of comet 22P/Kopff. Title: Tomography with LASCO-C2 Total Brightness Images Authors: Frazin, R. A.; Llebaria, A.; Lamy, P. L. Bibcode: 2009AGUFMSH44A..08F Altcode: The recently completed calibration of the K-corona total brightness (B) images from the SOHO/LASCO archive offers the opportunity for 3D reconstruction of the corona's electron density from a vastly larger data set than is available from the polarized brightness (pB) images. Since the B has a different line-of-sight weighting than the pB, the two may be combined to provide more information than is available from either one (this fact has already been exploited to locate CME centers of mass), leading to better results. Here, we present the first tomography based on B images and compare the results to those based on pB images and the combination of pB and B images. Implications for time-dependent tomography and improved modeling the of F-corona are discussed. Title: Properties of the nuclei and comae of 13 ecliptic comets from Hubble Space Telescope snapshot observations Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; A'Hearn, M. F.; Jorda, L. Bibcode: 2009A&A...508.1045L Altcode: Context: Knowledge of the size distribution of cometary nuclei and, more generally, of their physical properties is important for constraining models of the formation and evolution of the Solar System.
Aims: We report on our on-going effort to determine the ensemble properties of comets based on our success in detecting the nuclei of active comets with the Hubble Space Telescope (HST).
Methods: During cycle 8 (July 1999 to June 2000), we observed 13 ecliptic comets with the planetary camera 2 through at least two filters (V and R) and up to four (B, V, R, I) for the brightest ones. The ~30 min of HST observational time devoted to each comet did not permit a proper determination of light curves, so our “snapshot” observations yield effective radii, not shapes.
Results: Assuming spherical nuclei with a geometric albedo of 0.04 for the R band (except 0.024 for 10P/Tempel 2, as independently measured) and a phase law of 0.04 mag/deg, we obtained the following effective radii: 4P/Faye: 1.77 km, 10P/Tempel 2: 5.98 km, 17P/Holmes: 1.71 km, 37P/Forbes: 0.81 km 44P/Reinmuth 2: 1.61 km, 50P/Arend: 0.95 km, 59P/Kearns-Kwee: 0.79 km, 63P/Wild 1: 1.46 km, 71P/Clark: 0.68 km, 84P/Giclas: 0.90 km, 106P/Schuster: 0.94 km, 112P/Urata-Niijima: 0.90 km, 114P/Wiseman-Skiff: 0.78 km. In our present sample, eight out of thirteen nuclei have sub-kilometer radii. The average color of the observed nuclei is (V-R) = 0.52±0.04, which is significantly redder than the Sun. We determined the dust activity parameter Afρ of their coma in the R band, and estimated the dust production rates. The average reflectivity gradient of the dust comae of six comets is S' [670,792 nm] = 15.2±2.3% per kÅ.

Based on observations made with the NASA/ESA Hubble space telescope, obtained at Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-26555. Title: The Thermal Emission of Comet 8P/tuttle Nucleus as Observed with the Plateau de Bure Interferometer Authors: Boissier, Jeremie; Bockelée-Morvan, D.; Groussin, O.; Biver, N.; Colom, P.; Crovisier, J.; Jorda, L.; Lamy, P.; Moreno, R. Bibcode: 2009DPS....41.2001B Altcode: Measuring the thermal emission of cometary nuclei allows the determination of albedo-independent sizes for comets that are not visited by space probes. In the IR, the atmosphere makes such observations difficult from the ground, so that space telescopes (ISO, Spitzer) are frequently used to observe cometary nuclei. In the millimeter range, single dish observations are mainly sensitive to the dust coma. Interferometric measurements are required but restricted up to now to two cometary nuclei from the Oort cloud (Hyakutake, Hale-Bopp).

The Halley type comet 8P/Tuttle made a close approach to the Earth in January 2008 (geocentric distance of 0.25 AU). Previous studies suggested that its nucleus was large (7.8 km radius) and faintly active. As a result this comet was a good target for interferometric observations of its nucleus thermal emission at millimeter wavelengths.

8P/Tuttle was observed at 240 GHz (1.25 mm) with the IRAM interferometer on the Plateau de Bure in January 2008. The thermal emission of the nucleus was detected and found to be lower than expected, corresponding to an apparent radius close to 2 km. Independant observations carried out with Hubble and Spitzer space telescopes indicate a slightly larger size (2.8 km radius) and were used to build a shape and thermal emission model of 8P nucleus (Groussin et al., A&A suubmitted). We used this model to interpret the Plateau de Bure data and we present here the results of this analysis.

Observations of cometary nuclei in millimeter interferometry will grow up in number in the forthcoming years with the upgrading of current instruments and the opening of ALMA. This will increase the sample of observed nuclei from all the comet dynamic classes and enable further studies of their physical properties. Title: Exploring Potential Surface Heterogeneity of the Asteroid Steins observed from the Rosetta OSIRIS Instrument Authors: Leyrat, Cedric; Jorda, L.; Fornasier, S.; Fulchignoni, M.; Barucci, A.; Belskaya, I.; Lamy, P.; Groussin, O.; Charnoz, S.; Keller, H.; Sierks, H.; Hviid, S.; OSIRIS Team Bibcode: 2009DPS....41.5003L Altcode: Asteroid 2867 Steins is the first E type asteroid visited by a spacecraft. During the Rosetta flyby in September 2008, the OSIRIS NAC and WAC cameras have obtained several disk-resolved images in visible wavelengths, at different phase angles. At closest approach, the spatial resolution of the WAC images was about 80m/pixel, allowing looking for potential surface heterogeneity.

We have applied the G-mode multivariate statistical method (Coradini et al, 1977) to both NAC and WAC images obtained around closest approach, at different wavelengths, from 295 to 986 nm. The geometric parameters have been retrieved with the SPICE routines. The shape of Steins is assumed to be represented by a polyhedron of almost 58000 facets. The OASIS simulator (developed at LAM and MPS) has been used to retrieve the I/F quantity of each visible 'facet' of the asteroid 3D shape model. Thereafter, photometric corrections have been performed using the Hapke (2002) model to eliminate the variable illuminations conditions at the surface. The G-mode classification method has been performed on a limited number of facets, in a region limited to [-50,+70] deg. in latitude and [-20,+90] deg. in longitude.

Moreover, a gravity map of the asteroid has been obtained on the basis of the shape model considering a homogeneous internal density.

Here we present our results on the potential presence of compositional heterogeneities at the surface of Steins and of gravitational anomalies, and we discuss their possible implications on the evolution of the asteroid. Title: The Physical Properties of Asteroid 2867 Steins Authors: Lamy, Philippe L.; Jorda, L.; Gaskell, R.; Besse, S.; Groussin, O.; Kaasalainen, M.; OSIRIS Team Bibcode: 2009DPS....41.5901L Altcode: We will present an overview of the physical properties of the E-type asteroid 2867 Steins from the OSIRIS campaign during the Rosetta flyby (September 2008), from ground-based observations, and from recent thermal spectroscopy obtained with the Spitzer space telescope. A complete shape solution has been obtained from the combination of resolved images and inversion of light curves. We will discuss the properties of the impact craters, the formation of the large crater and its consequences on topographic features and the possible influence of the YORP effect in shaping Steins. We will review and confront the various sources of information on the composition and surface photometric properties of Steins. Title: New perspective in solar coronal physics: Giant externally occulted coronagraphs using satellites in flight formation Authors: Lamy, P.; Vivès, S. Bibcode: 2009AcAau..65..273L Altcode: Formation flying opens new perspectives in solar physics, and allow to conceive giant, externally occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at a distance of 100 m. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) is a mission proposed to ESA in the framework of its PROBA-3 demonstration program of formation flying which is presently in phase A. ASPIICS is a single coronagraph which will perform both high spatial resolution imaging of the solar corona as well as two-dimensional spectroscopy of several emission lines from the coronal base out to 3R⊙ using an étalon Fabry-Pérot interferometer. The classical design of an externally occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.01R⊙ from the solar limb. By tuning the position of the occulter spacecraft, it will even be possible to reach the chromosphere and the upper part of the spicules. Title: The ARTEMIS Catalog of LASCO Coronal Mass Ejections. Automatic Recognition of Transient Events and Marseille Inventory from Synoptic maps Authors: Boursier, Y.; Lamy, P.; Llebaria, A.; Goudail, F.; Robelus, S. Bibcode: 2009SoPh..257..125B Altcode: The LASCO-C2 coronagraph aboard the SOHO solar observatory has been providing a continuous flow of coronal images since 1996. Synoptic maps for each Carrington rotation have been built from these images, and offer a global view of the temporal evolution of the solar corona, particularly the occurrence of transient events. Coronal Mass Ejections (CMEs) present distinct signatures thus offering a novel approach to the problem of their identification and characterization. We present in this article an automated method of detection based on their morphological appearance on synoptic maps. It is based on adaptive filtering and segmentation, followed by merging with high-level knowledge. The program builds a catalog which lists the CMEs detected for each Carrington Rotation, together with their main estimated parameters: time of appearance, position angle, angular extent, average velocity and intensity. Our final catalog LASCO-ARTEMIS (Automatic Recognition of Transient Events and Marseille Inventory from Synoptic maps) is compared with existing catalogs, CDAW, CACTUS and SEEDS. We find that, likewise the automated CACTUS and SEEDS catalogs, we detect many more events than the CDAW catalog which is based on visual detection. The total number of detected CMEs strongly depends upon the sensitivity to small, faint and numerous events. Title: The colors of cometary nuclei—Comparison with other primitive bodies of the Solar System and implications for their origin Authors: Lamy, P.; Toth, I. Bibcode: 2009Icar..201..674L Altcode: We present new color results of cometary nuclei obtained with the Hubble Space Telescope (HST) whose superior resolution enables us to accurately isolate the nucleus signals from the surrounding comae. By combining with scrutinized available data obtained with ground-based telescopes, we accumulated a sample of 51 cometary nuclei, 44 ecliptic comets (ECs) and 7 nearly-isotropic comets (NICs) using the nomenclature of Levison [Levison, H.F., 1996. In: Rettig, T.W., Hahn, J.M. (Eds.), Completing the Inventory of the Solar System. In: ASP Conf. Ser., vol. 107, pp. 173-192]. We analyze color distributions and color-color correlations as well as correlations with other physical parameters. We present our compilation of colors of 232 outer Solar System objects—separately considering the different dynamical populations, classical KBOs in low and high-inclination orbits (respectively CKBO-LI and CKBO-HI), resonant KBOs (practically Plutinos), scattered-disk objects (SDOs) and Centaurs—of 12 candidate dead comets, and of 85 Trojans. We perform a systematic analysis of all color distributions, and conclude by synthesizing the implications of the dynamical evolution and of the colors for the origin of the minor bodies of the Solar System. We find that the color distributions are remarkably consistent with the scenarios of the formation of TNOs by Gomes [Gomes, R.S., 2003. Icarus 161, 404-418] generalized by the "Nice" model [Levison, H.F., Morbidelli, A., VanLaerhoven, Ch., Gomes, R., Tsiganis, L., 2008. Icarus 196, 258-273], and of the Trojans by Morbidelli et al. [Morbidelli, A., Levison, H.F., Tsiganis, K., Gomes, R., 2005. Nature 435, 462-465]. The color distributions of the Centaurs are globally similar to those of the CKBO-HI, the Plutinos and the SDOs. However the potential bimodality of their distributions allows to possibly distinguish two groups based on their (B-R) index: Centaur I with (B-R)>1.7 and Centaurs II with (B-R)<1.4. Centaurs I could be composed of TNOs (prominently CKBO-LI) and ultra red objects from a yet unstudied family. Centaurs II could consist in a population of evolved objects which have already visited the inner Solar System, and which has been scattered back beyond Jupiter. The diversity of colors of the ECs, in particular the existence of very red objects, is consistent with an origin in the Kuiper belt. Candidate dead comets represent an ultimate state of evolution as they appear more evolved than the Trojans and Centaurs II. Title: Three-Dimensional Kinematics of Coronal Mass Ejections from STEREO/SECCHI-COR2 Observations in 2007 - 2008 Authors: Boursier, Y.; Lamy, P.; Llebaria, A. Bibcode: 2009SoPh..256..131B Altcode: We present a new method to perform the three dimensional characterization of coronal mass ejections (CMEs) using stereoscopic images obtained with the STEREO/SECCHI-COR2 coronagraphs. Two approaches are proposed, and each associated algorithm gives the trajectory of the CME and its kinematical properties (velocity and acceleration profiles) intended for space weather forecast. The first approach is based on forward modeling appropriate to the reconstruction of surfaces in an optically thin medium, and performs a local approximation of the observed CME by a hemispherical shell, thus tracking the leading edge of the event. The second approach is based on tracking the center of gravity of the radiance of the CME in the images. More than 16 000 blind tests have been performed to assess the performance of each algorithm. For that purpose, we used three distinct libraries of simulated images of CMEs that correspond to three CME models: hemispherical shell, flux rope, and cloud-like. The two methods are applied to a set of CMEs observed in 2007 and 2008 by the SECCHI-COR2 coronagraphs, and when possible, our results are compared to those already published. The determinations of the direction of propagation and of the velocity are generally found in good agreement. Title: Imaging Asteroid (2867) Steins with OSIRIS onboard Rosetta Authors: Keller, H.; A'Hearn, M.; Angrilli, F.; Barbieri, C.; Barucci, A.; Bertaux, J.; Cremonese, G.; Davidson, B.; de Cecco, M.; Debei, S.; Fulle, M.; Groussin, O.; Gutierrez, P.; Hviid, S.; Ip, W.; Jorda, L.; Knollenberg, J.; Koschniy, D.; Kramm, J.; Kührt, E.; Küppers, M.; Lamy, P.; Lara, L.; Lopez Moreno, J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickmann, H.; Rodrigo, R.; Sabau, L.; Sierks, H.; Thomas, N.; Wenzel, P.; Lazzarin, M. Bibcode: 2009AGUSM.P12A..02K Altcode: The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS observed the E-type asteroid (2867) Steins during the fly-by of ESA's Rosetta spacecraft. Observations over a large phase angle range (from near 0 to 140) by the scientific camera system OSIRIS revealed the illuminated hemisphere of the asteroid's diamond-like shaped body with a mean radius of 2.7 km and a projected surface at zero phase angle of 5.3 x 3.9 km2. A large crater (diameter 2 km) is evidence of an almost disastrous impact and implies that Steins is not a solid rock. More than 30 craters or crater-like features with diameters > 150 m are identified. 7 round concavities are arranged along a line pointing radially away from the big impact crater. The shape and volume of asteroid Steins is derived from models based on the images of both OSIRIS cameras and earlier observations of the photometric light curves. Its resemblance to a spinning top suggests that it was influenced by the YORP effect making it the first optical observation of such a body. Analysis of the images provide the disk integrated albedo, reveal a strong opposition effect, and photometric properties of the surface showing very little variegation. Its very uniform, bright surface suggests that this asteroid is homogeneously formed out of the igneous (magmatic) minerals found in enstatite achondrite meteorites that are produced in melts requiring temperatures of more than 1000 C. Consequently (2867) Steins is a fragment of the interior of a large parent body. Title: Three-dimensional kinematics of coronal mass ejections from STEREO/SECCHI-COR2 observations in 2007-2008 Authors: Boursier, Y.; Lamy, P.; Llebaria, A. Bibcode: 2009EGUGA..1112760B Altcode: We present a new method to perform the three dimensional characterization of coronal mass ejections (CMEs) using stereoscopic images obtained with the STEREO/SECCHI-COR2 coronagraphs. Two approaches are proposed, and each associated algorithms returns the trajectory of the CME and its kinematics properties (velocity and acceleration profiles) intended for space weather forecast. The first approach is based on forward modeling appropriate to the reconstruction of surfaces in an optically thin medium, and performs a local approximation of the observed CME by an hemispherical shell, thus tracking the leading edge of the event. The second approach is based on tracking the center of gravity of the radiance of the CME on the images. More than 16000 blind tests have been performed to assess the performances of each algorithm. For that purpose, we used three distinct libraries of simulated images of CMEs that correspond to three CME models: hemispherical shell, flux rope, and cloud-like. The two methods are applied to a set of CMEs observed in 2007 and 2008 by the SECCHI-COR2 coronagraphs, and when possible, our results are compared to those already published. The determinations of the direction of propagation and of the velocity are generally found in good agreement. Title: The DynaMICCS perspective. A mission for a complete and continuous view of the Sun dedicated to magnetism, space weather and space climate Authors: Turck-Chièze, S.; Lamy, P.; Carr, C.; Carton, P. H.; Chevalier, A.; Dandouras, I.; Defise, J. M.; Dewitte, S.; Dudok de Wit, T.; Halain, J. P.; Hasan, S.; Hochedez, J. F.; Horbury, T.; Levacher, P.; Meissonier, M.; Murphy, N.; Rochus, P.; Ruzmaikin, A.; Schmutz, W.; Thuillier, G.; Vivès, S. Bibcode: 2009ExA....23.1017T Altcode: 2008ExA...tmp...42T The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar variability, including the previously unexplored inner core, the radiative/convective zone interface layers, the photosphere/chromosphere layers and the low corona. The mission delivers data and knowledge that no other known mission provides for understanding space weather and space climate and for advancing stellar physics (internal dynamics) and fundamental physics (neutrino properties, atomic physics, gravitational moments...). The science objectives are achieved using Doppler and magnetic measurements of the solar surface, helioseismic and coronographic measurements, solar irradiance at different wavelengths and in-situ measurements of plasma/energetic particles/magnetic fields. The DynaMICCS payload uses an original concept studied by Thalès Alenia Space in the framework of the CNES call for formation flying missions: an external occultation of the solar light is obtained by putting an occulter spacecraft 150 m (or more) in front of a second spacecraft. The occulter spacecraft, a LEO platform of the mini sat class, e.g. PROTEUS, type carries the helioseismic and irradiance instruments and the formation flying technologies. The latter spacecraft of the same type carries a visible and infrared coronagraph for a unique observation of the solar corona and instrumentation for the study of the solar wind and imagers. This mission must guarantee long (one 11-year solar cycle) and continuous observations (duty cycle > 94%) of signals that can be very weak (the gravity mode detection supposes the measurement of velocity smaller than 1 mm/s). This assumes no interruption in observation and very stable thermal conditions. The preferred orbit therefore is the L1 orbit, which fits these requirements very well and is also an attractive environment for the spacecraft due to its low radiation and low perturbation (solar pressure) environment. This mission is secured by instrumental R and D activities during the present and coming years. Some prototypes of different instruments are already built (GOLFNG, SDM) and the performances will be checked before launch on the ground or in space through planned missions of CNES and PROBA ESA missions (PICARD, LYRA, maybe ASPIICS). Title: ASPIICS, a giant externally occulted coronagraph for the PROBA-3 formation flying mission Authors: Vivès, S.; Lamy, P.; Koutchmy, S.; Arnaud, J. Bibcode: 2009AdSpR..43.1007V Altcode: Formation flying opens new perspectives for coronal physics, and allow to conceive giant, externally occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) is a mission proposed to ESA in the framework of the PROBA-3 program of formation flying which is presently in phase A, to exploit this technique for coronal observations. ASPIICS is composed of a single coronagraph which performs high spatial resolution imaging of the corona as well as 2-dimensional spectroscopy of several emission lines from the coronal base out to 3 R⊙. The selected lines allow to address different coronal regions: the forbidden line of Fe XIV at 530.285 nm (coronal matter), Fe IX/X at 637.4 nm (coronal holes), HeI at 587.6 nm (cold matter). An additional broad spectral channel will image the white light corona so as to derive electron densities. The classical design of an externally occulted coronagraph is adapted to the detection of the very inner corona as close as 1.01 R⊙ and the addition of a Fabry-Perot interferometer using a so-called " étalon". This paper is dedicated to the description of the optical design and its critical components: the entrance optics and the Fabry-Pérot interferometer. ASPIICS will address the question of coronal heating and of the role of waves by characterizing propagating fluctuations (waves and turbulence) in the solar wind acceleration region and by looking for oscillations in the intensity and Doppler shift of spectral lines. The combined imaging and spectral diagnostics capabilities available with ASPIICS will allow to map the velocity field of the corona both in the sky plane (directly on the images) and along the line-of-sight by measuring the Doppler shifts of emission lines. We will attempt to determine how the different components of the solar wind, slow and fast are accelerated. ASPIICS will observe the corona during the maximum of solar activity, insuring the detection of many Coronal Mass Ejections (CMEs). By rapidly alternating high resolution imaging and spectroscopy, CMEs will be thoroughly characterized. In addition, ASPIICS will attempt to characterize the topology of the magnetic field in the corona. Title: 3-Dimensional Reconstruction of Asteroid 2867 Steins Authors: Besse, S.; Groussin, O.; Jorda, L.; Lamy, P.; Kaasalainen, M.; Gesquiere, G.; Remy, E.; OSIRIS Team Bibcode: 2009LPI....40.1545B Altcode: The OSIRIS imaging experiment has imaged asteroid Steins. We have combined three methods to retrieve the shape: limbs, Point of Interest and light curves. The mean radius of Steins is 2.7 ± 0.3km, for a volume of 78 ± 30km^3 and a surface of 98 ± 25km^2. Title: The size and thermal properties of the nucleus of Comet 22P/Kopff Authors: Groussin, O.; Lamy, P.; Toth, I.; Kelley, M.; Fernandez, Y.; A'Hearn, M.; Campins, H.; Licandro, J.; Lisse, C.; Lowry, S.; Meech, K.; Snodgrass, C. Bibcode: 2009Icar..199..568G Altcode: We detected the nucleus of Comet 22P/Kopff at 4.87 AU from the Sun with the two IRS peak-up cameras of the Spitzer Space Telescope on April 19, 2007. Using the thermal model of [Groussin, O., and 15 colleagues, 2007. Icarus 187, 16-25], we derive a nucleus size of 1.89±0.16 km, in agreement with [Lamy, P., Toth, I., Jorda, L., Groussin, O., A'Hearn, M.F., Weaver, H.A., 2002. Icarus 156, 442-455], and a thermal inertia I⩽30 JKms. Title: Separation of limb and terminator on apparent contours of solar system small bodies Authors: Llebaria, A.; Jorda, L.; Groussin, O.; Gesquiere, G.; Lamy, P. Bibcode: 2009SPIE.7246E..10L Altcode: 2009SPIE.7246E..29L Segmentation of contours and silhouettes is a recurrent topic in image recognition and understanding. In this paper we describe a new method used to divide in two parts (the limb and the terminator) the apparent silhouette of an irregular astronomical body illuminated by a unique source, the Sun. One of the main objectives of the asteroids and comets flyby is the detailed 3D reconstruction of such bodies. However the number of images obtained during a flyby is limited, as well as the number of viewing geometries. In the 3D reconstruction we must consider not only the camera motion but also the free rotation of the body. The local brightness variations in the image vary with the rotation of the body and with the changing body-camera distance. The topography at the surface of the body can vary from very smooth to highly chaotic. In the shape from silhouette 3D reconstruction methods, limb profiles are used to retrieve the visual hull of the body. It is therefore required to be able to separate the limb profiles from the terminator ones. In this communication, we present a new method to perform this task based on the local measurement of the contour smoothness, which we define here as "activity". Developed in the framework of the Rosetta mission our method has been tested on a large set of asteroid and comet images taken during interplanetary missions. It looks robust to magnification and enlightenment changes Title: Disk-Resolved Photometry of 9P/Tempel 1 and 2867 Steins Authors: Laurent, Jorda; Spjuth, S.; Keller, H.; Lamy, P.; OSIRIS Team Bibcode: 2009DPS....40.2837L Altcode: 2009BAAS...41..559L Disk-resolved photometric properties of asteroids have been obtained on a sample of objects observed by space missions since the 80's. We have developed a method to retrieve such properties from images acquired by imaging instruments aboard spacecrafts.

We applied the method to images of the nucleus of comet 9P/Tempel 1 acquired by the DEEP IMPACT HRI camera, and we derived both local and global Hapke parameters for the comet nucleus, as well as its geometric albedo. The results have been compared to those obtained by Li et al. (Icarus 191, 161, 2007). We will also present very preliminary results on asteroid 2867 Steins observed by OSIRIS, the imaging system aboard ROSETTA, after its flyby on Sept. 5, 2008. Title: Asteroid 21 Lutetia : UBVRI Light Curves from OSIRIS-NAC Authors: Faury, Guillaume; Jorda, L.; Lamy, P.; Kaasalainen, M.; Mottola, S.; OSIRIS Team Bibcode: 2009DPS....40.2838F Altcode: 2009BAAS...41..559F We report on new observations aimed at characterizing asteroid 21 Lutetia, one of the targets of the Rosetta space mission. The asteroid was imaged with the OSIRIS-NAC camera during the cruise phase of the Rosetta spacecraft, at a phase angle of 22.36º, and was continuously monitored over 14 hr (on 2 and 3 January 2007), thus covering one rotational period and a half. From accurate photometric calibrations with the solar analog star, 16 CygB, we have obtained high quality light curves of 21 Lutetia in the U, B, V, R and I photometric bands. We confirm a sidereal period of 8.17 hr. No spectral variations with the rotation have been found. The resulting reflectivity spectrum is in a very good agreement with that of Barucci et al. (2005). Combining with existing observations, we have obtained its phase function. Title: First Results from the Rosetta Asteroid Steins Fly-by Observed by OSIRIS and VIRTIS Authors: Keller, Horst Uwe; Coradini, A.; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman, H.; Rodrigo, R.; Capaccioni, F.; Drossart, P.; De Sanctis, M. C.; Arnold, G.; OSIRIS Science Team; VIRTIS Science Team Bibcode: 2009DPS....40.6010K Altcode: 2009BAAS...41..564K On Sep 5th 2008 the ESA Rosetta spacecraft made a close fly-by of the E-type asteroid (2867) Steins. During the fly-by the asteroid was observed with the OSIRIS camera system and the VIRTIS infrared imaging spectrometer. OSIRIS is composed of a wide-angle (100um resolution) imager and a narrow angle (18.7um resolution) imager. VIRTIS is an instrument that combines imaging and spectrometry in the Vis and IR (0.25-5um), through a slit spectrometer(VIRTIS-M) with a high resolution IR channel (VIRTIS-H).

Rosetta passed through zero phase angle shortly before CA provided the opportunity to determine the geometric albedo and the phase function of the asteroid. High spatial resolution hyperspectral images were obtained by VIRTIS. The high albedo of the E-type asteroid is confirmed. The spectrum of Steins was observed using a complement of 23 OSIRIS filters from 245 to 1000 nm and VIRTIS spectra. The spectrum is in good agreement with published telescopic spectra in the visible and shows a strong drop off in the UV below 400 nm.

Images around CA show the asteroid surface on a scale of 80 m per pixel. The dimensions of Steins are 4.0 km along its spin axis and 5.9 km in the perpendicular direction. A shape model will be presented. The appearance of the body is dominated by a large crater (diameter 2 km) at the northern pole. From there a chain of 7 craters (catenae) extends across the surface visible during the fly-by. More than 20 craters with diameters > 0.2 km can be counted. First results of a photometric model based on detailed topography are expected. Title: Rosetta Fly-by of Asteroid 2867 Steins: Phase Function from the OSIRIS Imaging System Authors: Hviid, Stubbe; Fornasier, S.; Vernazza, P.; Sierks, H.; Keller, U.; Sabolo, W.; Kueppers, M.; Ferri, F.; Da Deppo, V.; Barbieri, C.; Lamy, P.; Jorda, L.; Groussin, O.; Koschny, D.; OSIRIS Team Bibcode: 2009DPS....40.2834H Altcode: 2009BAAS...41..558H The ESA Rosetta mission performed a fly-by of the E-type asteroid Steins on September 5, 2008. The geometry of the fly-by was optimized to reach the zero phase angle aspect a couple of minutes before the closest approach. A fast monitoring sequence was implemented to investigate the phase function of the asteroid in the narrowband OI filter, centered at 630 nm, with the Wide Angle Camera of the OSIRIS imaging system. A set of 21 images of 30 ms exposure time were acquired for monitoring the opposition surge in the phase angle range from 0 to 11 degrees with a step of 0.5-1 degrees. In addition, several OI images were taken in the spectrophotometric sequences allowing us to reach a phase function coverage up to 140 degrees. In this work we present the Steins phase function and its interpretation. The derived values of the albedo, of the linear slope, and of the Hapke G parameter match those of E class asteroids. Title: Shape, Rotational Properties and Phase Function of Asteroid 2867 Steins Authors: Lamy, Philippe L.; Kaasalainen, M.; Jorda, L.; Gutierrez, P.; Faury, G.; Sabolo, W.; OSIRIS Team Bibcode: 2009DPS....40.2833L Altcode: 2009BAAS...41..558L The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS observed the E-type asteroid (2867) Steins during the fly-by of ESA's Rosetta spacecraft. Before the flyby, the OSIRIS camera obtained two light curves on 20 August and 4 September 2008. Combined with previously published OSIRIS and ground-based observations, we will present a refined global shape model of the asteroid, the rotational parameters and the phase function (at large phase angles). Title: Spitzer Space Telescope observations of the nucleus of comet 67P/Churyumov-Gerasimenko Authors: Lamy, P. L.; Toth, I.; Groussin, O.; Jorda, L.; Kelley, M. S.; Stansberry, J. A. Bibcode: 2008A&A...489..777L Altcode: Context: Comet 67P/Churyumov-Gerasimenko is the target of the Rosetta mission, and an early characterization of its nucleus is required to assist in preparing the orbital strategy of the spacecraft, the delivery of the Philae surface module and the science operations. We detected the nucleus using the Hubble Space Telescope in March 2003, but had to assume an albedo to derive its size from its observed magnitudes.
Aims: It is important to derive an additional constraint for independently determining both the comet size and albedo.
Methods: We implemented the well-known “radiometric method”, which combines visible and infrared photometry. Sixteen thermal images of 67P/C-G were obtained by the Multiband Imaging Photometer (MIPS) 24 μm channel of the Spitzer Space Telescope (SST) on 25 February 2004: the observations spanned a time interval of ~12.5 h, which sampled the rotational light curve of its nucleus. The comet was then outbound at a heliocentric distance of 4.48 AU, at a distance of 4.04 AU from SST, and at a solar phase angle of 12.1°. The nucleus conspicuously appeared as a bright point source superimposed on a dust trail; it was necessary to apply the point-spread function fitting technique using an adequate model of the trail to correctly determine the thermal flux from the nucleus. The data were analyzed using a standard thermal model that incorporated the thermal inertia.
Results: Our preferred solution with a low thermal inertia has overall dimensions measured along the principal axis of 4.40-5.20 km, 4.16-4.30 km, and 3.40-3.50 km, corresponding to an effective radius of a sphere with the same volume in the range of 1.93-2.03 km. Larger values of thermal inertia produce larger sizes but the effective radius cannot exceed ~2.3 km. The albedo is in the range 0.039-0.043, remarkably consistent with the canonical value of 0.04 for cometary nuclei. The success of the landing of the Philae surface module remains critically dependent upon the bulk density of the nucleus: it would be safe if close to 0.35 g cm-3, but a larger value, for instance 0.5 g cm-3, would present some risks.

Based on observations made with the NASA Spitzer Space Telescope. Title: The Rosetta Asteroid Steins Flyby Observed by OSIRIS Authors: Keller, Horst Uwe; Barbieri, C.; Koschny, D.; Lamy, P.; Rickman, H.; Rodrigo, R.; OSIRIS Team Bibcode: 2008DPS....40.2831K Altcode: 2008BAAS...40..442K The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS was already used to observe the light curve of the E-type asteroid (2867) Steins in preparation of the ESA Rosetta flyby (Küppers et al. A&A 2007). During the approach observations of the light curve will be repeated to improve the knowledge about the rotational status, coarse shape, and phase of Steins. The closest approach (CA) campaign will start 2 hours before CA when the spacecraft is still 60000 km away from the asteroid. Changes of the reflectivity while passing through zero phase angle shortly before CA will be recorded taking images as fast as possible. The wide angle camera (WAC) will be used to search for satellites. Boulders as small as 10 cm in diameter can be detected in the large field of view. The narrow angle camera (NAC) will concentrate to observe the properties of Steins determining its shape and surface morphology. Near CA at a distance of 800 km images of Steins will cover about 330 pixel in diameter out of the 2k by 2k pixel CCD. We will report on the topography and geomorphology based on a derived digital terrain model. Photometric properties and phase angle variations will be determined over taking advantage of the varying observation geometry. Both cameras will use a complement of 23 filters between 245 to 1000 nm. Title: Asteroid 2867 Steins. I. Photometric properties from OSIRIS/Rosetta and ground-based visible observations Authors: Jorda, L.; Lamy, P. L.; Faury, G.; Weissman, P.; Barucci, M. A.; Fornasier, S.; Lowry, S.; Toth, I.; Küppers, M. Bibcode: 2008A&A...487.1171J Altcode: Context: Asteroid 2867 Steins is the first target of the Rosetta space mission with a flyby scheduled in September 2008.
Aims: An early characterization is needed to optimize the flyby parameters and the science operations and to maximize the scientific return. The aim of this article is to characterize the photometric properties of this asteroid.
Methods: The asteroid was imaged with the Narrow Angle Camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) during the cruise phase of the Rosetta spacecraft, at a phase angle of 41.7° significantly larger than achievable from Earth. It was continuously monitored over ~24 h (on 11 March 2006), thus covering four rotational periods, at a temporal cadence of 6 min. An accurate photometric calibration was obtained from the observations of a solar analog star, 16 Cyg B.
Results: The light curve in the R photometric band of the Johnson-Kron-Cousins system has a mean value R(1,1,α = 41.7° = 14.13 ± 0.03 and an amplitude of 0.25 ± 0.04 mag. The periodicity was analyzed with different techniques yielding a mean value of the synodic rotational period of 6.054 ± 0.003 h. By combining with ground-based observations obtained at different phase angles, the phase function is constructed and characterized by a linear part having a phase coefficient β = 0.025 ± 0.001 mag/deg and a mean value R(1,1,0) = 13.10 ± 0.04. In terms of the H-G formalism, the best fit photometric values are G = 0.35 ± 0.05 and H = 12.84 ± 0.07, but the resulting opposition surge of 0.25 mag, although typical of E-type asteroids, is not really constrained because of the lack of data at phase angles below 7°. Altogether the photometric properties of asteroid 2867 Steins (phase function, color and albedo) indicate that it is a somewhat extreme E-type object, although it is known that this quite small population exhibits at least three different surface mineralogies.

Table [see full textsee full text] is only available in electronic form at http://www.aanda.org Title: Asteroid 2867 Steins. III. Spitzer Space Telescope observations, size determination, and thermal properties Authors: Lamy, P. L.; Jorda, L.; Fornasier, S.; Groussin, O.; Barucci, M. A.; Carvano, J.; Dotto, E.; Fulchignoni, M.; Toth, I. Bibcode: 2008A&A...487.1187L Altcode: Context: Asteroid 2867 Steins is the first target of the Rosetta space mission with a flyby scheduled in September 2008.
Aims: An early characterization is needed to optimize the flyby parameters and the science operations, and to maximize the scientific return.
Methods: We used the infrared spectrograph (IRS) of the Spitzer Space Telescope (SST) to obtain 14 spectra ranging from 5.2 to 38.0 μm, and to sample the rotational period of the asteroid. The observations were performed on 22 November 2005, when the asteroid was 2.13 AU from the Sun, 1.60 AU from the SST, and at a phase angle of 27.2°. They were interpreted using a standard thermal model incorporating the thermal inertia.
Results: The solution for a spherical shape leads to an effective radius rn = 2.46 ± 0.20 km and a thermal inertia I = 150 ± 60 J K-1 m-2 s-1/2, for a beaming factor between 0.8 and 1.0. The geometric albedo is then constrained by visible photometry to pR = 0.31 ± 0.05 and pV = 0.27 ± 0.04 when using a linear phase function. The H-G phase law, which includes an opposition effect, leads to larger values of the albedo, p_R(H-G) = 0.40 ± 0.07 and p_V(H-G) = 0.34 ± 0.06. The solution for our 3-dimensional shape model has overall dimensions of 5.73 ± 0.52 × 4.95 ± 0.45 × 4.58 ± 0.41 km. Title: Hubble Space Telescope Observations of Fragment C of the Split Comet 73p/schwassmann-wachmann 3 in 2001 and 2006 Authors: Toth, Imre; Lamy, P. L.; Weaver, H. A.; Noll, K. S.; Mutchler, M. J. Bibcode: 2008DPS....40.0508T Altcode: 2008BAAS...40..394T We unambiguously detected fragment C of the split comet 73P/Schwassmann-Wachmann 3 on 26 November 2001 with the PC2 and on 10 April 2006 with the HRC of the ACS of the HST. On 26 November 2001 it was at heliocentric and geocentric distances respectively 3.26 AU and 2.34 AU and despite of its large heliocentric distance it was highly active and from images obtained during two consecutive orbits we determined an effective radius of 0.68±0.04 km assuming a spherical shape and standard values for the geometric albedo (0.04) and the phase function (0.04 mag/deg) (Icarus 178, 235-247, 2005). We re-observed fragment C in 2006, taking advantage of the exceptional close encounter of the comet with Earth. The heliocentric and geocentric distances were respectively 1.24 AU and 0.29 AU. Six HST orbits spread over 21 hrs allowed us to obtain multi-color images (BVR) but only a poorly sampled light curve. We determined a possible synodic rotational period in the range 3.5-4 hr. The mean magnitude of the light curve leads to an effective radius of 0.53±0.02 km for the fragment C (assuming the same standard values for the albedo and phase function) and its amplitude, to a minimum axial ratio of 1.8±0.3. Our deep exposures did not reveal any subfragment in the vicinity of the main C fragment. We will discuss possible scenarios to explain the decrease of the size of the C fragment which apparently took place between 2001 and 2006. Moreover, we will discuss a scenario to explain the increase of the rotational period of the C fragment which apparently took place between our HST observations and the radar observations (BAAS 38, abstr. 12.06, p. 504, 2006) about one month later. H,A,W. acknowledges supports by NASA through grant GO/10625 from the STScI, I.T. acknowledges support from CNES, France. Title: Photometry of the Kreutz Comets 1996-2005 Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.; Hamilton, D. P.; Lamy, P.; Llebaria, A. Bibcode: 2008DPS....40.1601K Altcode: 2008BAAS...40Q.411K We present the results of our photometric study of the Kreutz group of sungrazing comets observed by SOHO-LASCO from 1996-2005. We extend the work of Biesecker et al. (2002), expanding the sample from 141 to more than 900 comets. The Kreutz comets seen by SOHO are produced by fragmentation from the more massive members of the family which include Ikeya-Seki (C/1965 S1 = 1965f) and C/1882 R1. None of the SOHO observed Kreutz comets have survived perihelion due to both their small size (we infer sizes less than 50 meters in radius) and perihelion distances below 2 solar radii.

Kreutz comets typically brighten at a rate near r-7.3 when first entering the SOHO field of view (at distances near 30 solar radii), then rapidly transition to brightening at a rate near r-3.8 from 16-24 solar radii. We find that they do not have a bimodal distance of peak brightness as previously reported by Biesecker et al. (2002), but instead peak between 10-14 solar radii, suggesting there is a continuum, perhaps due to compositional variations, rather than two distinct subpopulations. Inside of 10 solar radii but prior to perihelion, the comets fade rapidly and disappear by 6 solar radii.

We derive nuclear sizes of up to 50 meters in radius, with a cumulative size distribution of N(>R) R-2.2 for comets larger than 5 meters in radius. This size distribution cannot explain the six largest members of the family seen from the ground, suggesting that either the family is not collisionally evolved or that the distribution is not uniform around the orbit. The total mass of the distribution up to the largest expected size ( 500 meters) is 4x1014 g, much less than the estimated mass of the largest ground observed members.

This research was supported by NASA Planetary Atmospheres grants NAG513295 and NNG06GF29G. Title: Spitzer Space Telescope Observations of the Nucleus of Comet 8P/Tuttle Authors: Groussin, Olivier; Kelley, M.; Lamy, P.; Toth, I.; Fernandez, Y.; Jorda, L.; Weaver, H. Bibcode: 2008DPS....40.0503G Altcode: 2008BAAS...40..393G We observed comet 8P/Tuttle, a nearly isotropic comet (NIC), with the IRS and MIPS instruments of the Spitzer Space Telescope (SST). The IRS observations were performed on 2 November 2007 when the comet was at 1.32 AU from SST, 1.61 AU from the Sun, and nearly 3 months before perihelion on 27 January 2008 when its heliocentric distance was 1 AU. We used IRS in low-resolution mode to obtain the spectral energy distribution (SED) from 5 to 35 micron. The MIPS observations were performed on 22 June 2008 when the comet was at 1.58 AU from SST and 2.24 AU from the Sun. We sampled a period of 15 hours with 20 MIPS images at 24 µm, and also acquired 4 MIPS images at 70 µm to better constrain the SED. From these IRS and MIPS observations, we derived the size and thermal inertia of the nucleus of comet 8P/Tuttle. The (010-000) vibrational emission band of water at 6.3 microns was also detected, and we derived the water production rate and active surface fraction. Title: Asteroid 2867 Steins. II. Multi-telescope visible observations, shape reconstruction, and rotational state Authors: Lamy, P. L.; Kaasalainen, M.; Lowry, S.; Weissman, P.; Barucci, M. A.; Carvano, J.; Choi, Y. -J.; Colas, F.; Faury, G.; Fornasier, S.; Groussin, O.; Hicks, M. D.; Jorda, L.; Kryszczynska, A.; Larson, S.; Toth, I.; Warner, B. Bibcode: 2008A&A...487.1179L Altcode: Context: Asteroid 2867 Steins is the first target of the Rosetta space mission with a flyby scheduled in September 2008.
Aims: An early physical characterization is needed to optimize the flyby parameters and the science operations, and to maximize the scientific return. The aim of this article is to characterize the shape and rotational state of this asteroid.
Methods: We compile a set of 26 visible light curves whose phase angle coverage extends from 7.5° to 41.7°, and perform their simultaneous inversion relying on convex modeling.
Results: The full three-dimensional solution for asteroid 2867 Steins is rather spherical with axial ratios a/b=1.17 and a/c=1.25. The rotational state is characterized by a sidereal period of 6.04681 ± 0.00002 h, and the pole direction defined by its ecliptic coordinates λ ≈ 250° and β ≈ - 89° has an uncertainty of about 5°. It is therefore almost exactly perpendicular to the ecliptic plane, and the viewing geometries are thus restricted to only ±20° about Steins' equator. Consequently, the shape model is not strongly constrained, and the polar flattening has an uncertainty of about 10%. Inversion is basically scale-free, and absolute scaling comes from a measurement of its thermal emission with the Spitzer Space Telescope (Lamy et al. 2008, A&A, 487, 1187), yielding overall dimensions of 5.73 ± 0.52, 4.95±0.45, and 4.58 ± 0.41 km. Title: Hubble Space Telescope Observations of the Nucleus of Comet 8P/Tuttle Authors: Lamy, Philippe L.; Toth, I.; Jorda, L.; Weaver, H. A.; Groussin, O.; A'Hearn, M. F. Bibcode: 2008DPS....40.0502L Altcode: 2008BAAS...40..393L We unambiguously detected the nucleus of comet 8P/Tuttle, a nearly-isotropic comet (NIC) in a 13.5 yr orbital period, during its recent close (0.25 AU) Earth encounter with the Planetary Camera 2 of the Hubble Space Telescope (HST).

The observations were performed from December 10.0 to 11.2, 2007, and consisted in 12 visits extending over a 28-hour period. At the mid-point of the observing window, the comet was 1.25 AU from the Sun , 0.48 AU from the Earth and at a phase angle of 46.6 deg. During each visit corresponding to an HST orbit, typically twelve images were obtained through five broadband filters (UBVRI). The light curve exhibits a complex shape best modeled by a bilobate body as evidenced by the radar observations of Harmon et al. (2008). We determined a synodic rotational period of 11.4 hr. Assuming the same albedo of 0.04 for the two lobes, we found respective radii of 1.2 km and 2.8 km. During the HST observations, the nucleus was at an aspect angle (between spin axis and line of sight) of 65 deg. Title: 3-Dimensional Reconstruction of the ROSETTA Targets - Application to Asteroid 2867 Steins Authors: Besse, Sebastien; Groussin, O.; Jorda, L.; Lamy, P.; OSIRIS Team Bibcode: 2008DPS....40.2830B Altcode: 2008BAAS...40..442B The OSIRIS imaging experiment aboard the Rosetta spacecraft will image asteroids Steins in September 2008 and Lutetia in 2010, and comet 67P/Churyumov-Gerasimenko in 2014. An accurate determination of the shape is a key point for the success of the mission operations and scientific objectives. Based on the experience of previous space missions (Deep Impact, Near, Galileo, Hayabusa), we are developing our own procedure for the shape reconstruction of small bodies. We use two different techniques : i) limb and terminator constraints and ii) ground control points (GCP) constraints. The first method allows the determination of a rough shape of the body when it is poorly resolved and no features are visible on the surface, while the second method provides an accurate shape model using high resolution images. We are currently testing both methods on simulated data, using and developing different algorithms for limb and terminator extraction (e.g.,wavelet), detection of points of interest (Harris, Susan, Fast Corner Detection), points pairing using correlation techniques (geometric model) and 3-dimensional reconstruction using line-of-sight information (photogrammetry). Both methods will be fully automated. We will hopefully present the 3D reconstruction of the Steins asteroid from images obtained during its flyby.

Acknowledgment: Sébastien Besse acknowledges CNES and Thales for funding. Title: In-orbit calibration of the polarization flat fields of the SOHO-LASCO coronagraphs Authors: Llebaria, A.; Lamy, P. Bibcode: 2008SPIE.7010E..1IL Altcode: 2008SPIE.7010E..46L Since 11 years SOHO-LASCO coronagraphs are producing a unique set of the Sun corona images in the 2-32 solar radius range. For the first time a complete set of coronal calibrated images in WL (polarized and unpolarized) for the full solar cycle is available. The telescopes are equipped with 3 polarizers at -60,0 and 60 degrees, one all pass channel and a set filters. Ground calibrations were completed with in orbit calibrations. To control the evolution of sensivity for each bandpass and for each polarizer, the LASCO-C2 and LASCO-C3 coronographs were provided with an internal system of calibration in orbit. The measures obtained in 1996 and 2003 have been used to determine the CCD flat field for each filter bandpass, the gain constant (ADU to phe- conversion) and the polarizers transmittance map. The solar corona itself was also used to control the local response. Spacecraft rotations by 45 and 90 complete the test, and allowed for a ultimate but relevant global correction of the polarized images. Title: In-flight validation of the formation flying technologies using the ASPIICS/PROBA-3 giant coronagraph Authors: Vivès, S.; Lamy, P.; Levacher, P.; Venet, M.; Boit, J. L. Bibcode: 2008SPIE.7010E..3RV Altcode: 2008SPIE.7010E.109V Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. Formation flyers open new perspectives and allow conceiving giant, externally-occulted coronagraphs using two-spacecraft system. The PROBA-3 formation flying demonstration mission, currently in its preparatory study phase, is intended to incorporate the ASPIICS (Association de Satellites Pour l'Imagerie et l'Interfromtrie de la Couronne Solaire) scientific payload. ASPIICS is a solar coronagraph designed to observe from the coronal base out to 3 solar radii with high spatial resolution in the visible range. Formation flying technique imposes new constraints and major challenges in particular in terms of metrology. ASPIICS will both use and demonstrate the formation flying features and performances. In order to fully validate the formation flying technique and to improve the scientific return, original developments linked to the formation flying constraints have been made these last years and are presented in this article. Title: The coronal dynamics imagers for the KuaFu mission Authors: Vives, S.; Lamy, P.; Rousset, G.; Boit, J. L. Bibcode: 2008AdSpR..42..106V Altcode: The Space Weather Explorer - KuaFu mission will provide simultaneous, long-term, and synoptic observations of the complete chain of disturbances from the solar atmosphere to the geospace. KuaFu-A (located at the L1 liberation point) includes Coronal Dynamics Imagers composed of a Lyman-α coronagraph (from 1.15 to 2.7 solar radii) and a white light coronagraph (out to 15 solar radii), in order to identify the initial sources of Coronal Mass Ejections (CMEs) and their acceleration profiles. The difficulty of observing the lower corona should not be underestimated since instrumental stray light remains a critical issue in the visible because of the low contrast of the corona with respect to the Sun. Observing the corona in the Lyman-α line is a valid alternative to white light observations. This approach takes advantage of both the intrinsic higher contrast of the corona with respect to the solar disk in this line compared to the visible, and the absence of F-corona at 121.6 nm. Furthermore, it has been convincingly shown that the coronal structures seen in Lyman-α correspond to those seen in the visible and which result from Thomson scattering of the coronal ionized gas. This is because the plasma is still collisional in the lower corona so that the hydrogen neutral atoms are coupled to the protons. A classical, all-reflecting internally-occulted Lyot coronagraph is required so as to preserve the image quality down to the inner limit of the field-of-view. A narrow band interference filter located in a collimated beam allows isolating the Lyman-α line. The visible coronagraph will adopt the approach of a single instrument having a large field-of-view extending from 2.5 to 15 solar radii. Such a design is based on refractive externally-occulted coronagraphs built for recent past missions, essentially the LASCO-C2 and C3 instruments and the SECCHI/COR 2 of the STEREO mission, which is itself a combination of the C2 and C3 instruments. Title: Comet 144P/KUSHIDA Authors: Kelley, M. S.; Fernandez, Y.; Weaver, H.; Toth, I.; Reach, W.; Pittichova, J.; Meech, K.; Lowry, S.; Lisse, C.; Licandro, J.; Lamy, P.; Groussin, O.; Fitzsimmons, A.; Campins, H.; Bauer, J.; A'Hearn, M.; Marsden, B. G. Bibcode: 2008MPEC....N...20K Altcode: No abstract at ADS Title: Comet Observations [245 Spitzer Space Telescope] Authors: Kelley, M. S.; Fernandez, Y.; Weaver, H.; Toth, I.; Reach, W.; Pittichova, J.; Meech, K.; Lowry, S.; Lisse, C.; Licandro, J.; Lamy, P.; Groussin, O.; Fitzsimmons, A.; Campins, H.; Bauer, J.; A'Hearn, M. Bibcode: 2008MPC..63320..13K Altcode: No abstract at ADS Title: New perspectives in solar coronagraphy offered by formation flying: from PROBA-3 to Cosmic Vision Authors: Lamy, P.; Vivès, S.; Damé, L.; Koutchmy, S. Bibcode: 2008SPIE.7010E..1HL Altcode: Formation flying opens new perspectives in solar physics, and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at a distance of hundred meters. Conditions close to those of a solar total eclipse can then be achieved offering the capability of imaging the solar corona down to the limb at very high spatial resolution. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) is a mission proposed to ESA in the framework of its PROBA-3 demonstration program of formation flying which is presently in phase A. ASPIICS is a single coronagraph which will perform both high spatial resolution imaging of the solar corona as well as 2-dimensional spectroscopy of several emission lines from the coronal base out to 3 R\beye using a Fabry-Pérot étalon interferometer. The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.01 R\beye from the solar limb. Super-ASPIICS is an even more ambitious instrument part of the scientific payload of HiRise, the High Resolution Imaging and Spectroscopy Explorer proposed to ESA in the framework of its Cosmic Vision program. With an increased inter-satellite distance of 280 m, an aperture of 300 mm, a spectral domain extending from the ultraviolet to the near-infrared, and spectroscopic capabilities, Super-ASPIICS will offer unprecedented diagnostic capabilities, including the measurement of coronal magnetic fields. Title: The Origin of Polar Streamers in the Solar Corona Authors: Zhukov, A. N.; Saez, F.; Lamy, P.; Llebaria, A.; Stenborg, G. Bibcode: 2008ApJ...680.1532Z Altcode: We investigate the large-scale three-dimensional (3D) structure of the solar corona near the maximum of the 23rd solar cycle in an attempt to determine the origin of polar streamers. We use a model that allows us to simulate the quasi-stationary configuration of the large-scale coronal density distribution. The coronal neutral line, as given by the potential field source surface (PFSS) model, serves as a proxy for mid- and low-latitude current sheets. We investigate the contribution of possible polar coronal current sheets associated with large-scale photospheric magnetic neutral lines around the poles of the Sun (polar crown neutral lines). Positions of polar neutral lines are radially extrapolated outward to obtain the configuration of polar current sheets. Coronal plasma sheets are centered around introduced current sheets. Streamer positions during Carrington rotation 1965, near the activity maximum, are calculated. Simulated synoptic maps of the coronal brightness are compared with those obtained from observations by the LASCO C2 coronagraph on board the SOHO spacecraft. We demonstrate that polar streamers are "classical" streamers situated above low-lying loops (observed by SOHO EIT) connecting the regions of opposite magnetic polarity on two sides of polar crown neutral lines. Polar streamer configurations obtained from our model are close to those observed by LASCO. Our results suggest that the PFSS model cannot adequately describe the configuration of streamers during the epoch of high solar activity. The representation of the streamer belt as a single tilted and warped current sheet becomes questionable. Multiple coronal current sheets may better correspond to the observed streamer configurations. Title: Results From SEPPCoN, a Survey to Study the Physical Properties of the Nuclei and Dust of Jupiter-Family Comets Authors: Fernandez, Y.; Kelley, M.; Lamy, P.; Reach, W.; Toth, I.; Groussin, O.; Lisse, C.; A'Hearn, M.; Bauer, J.; Campins, H.; Fitzsimmons, A.; Licandro, J.; Lowry, S.; Meech, K.; Pittichova, J.; Snodgrass, C.; Weaver, H. Bibcode: 2008AGUSM.P41A..08F Altcode: We present results from SEPPCoN, our Survey of Ensemble Physical Properties of Cometary Nuclei. This survey involves studying 100 Jupiter-family comets (JFCs) -- about 30% of the known population -- at both mid-infrared and visible wavelengths. We have used the Spitzer Space Telescope to study the comets' thermal emission, and many ground-based telescopes (Apache Point's ARC 3.5-m; ESO's NTT 3.6-m; MKO's UH 2.2-m and Keck 10-m; Palomar's 5-m and 1.5-m; ORM's WHT 4.2-m, NOT 2.6-m, and LT 2-m; Cerro Pachon's SOAR 4.1-m) to study the reflected sunlight. The Spitzer observations (imaging with IRS PU and MIPS) are complete, and the ground-based observations (imaging in at least R band) are about half complete. Almost all our targets are imaged while farther than 4 AU from the Sun, to minimize (and often eliminate) confusion caused by dust from cometary activity. The Spitzer data constrain the effective radii of the nuclei; we find preliminarily that the cumulative size distribution's power-law slope is similar to what has been found by others using visible wavelength studies, suggesting that there is no strong trend of albedo with size. The Spitzer data also tell us about the thermal inertia, and we find that many -- though not all -- cometary nuclei seem to have low values of this, consistent with a porous, fluffy, poorly-conducting, dusty surface layer. The Spitzer images show that about one-third of our sample appeared with extended dust emission despite being close to aphelion. We find that often the activity observed at these distances seems to turn off abruptly once a JFC passes aphelion. We have used dynamical analysis to constrain the dust grain sizes and thereby distinguish dust tails from dust trails. The dust temperatures are in most cases consistent with isothermal, low-albedo grains in LTE. We thank the Spitzer Science Center and the TACs of the aforementioned telescopes for supporting this research. Title: A Portrait of Asteroid 2867 Steins from Visible and Infrared Observations with Ground- and Space-Based Telescopes Authors: Lamy, P. L.; Barucci, A.; Fornasier, S.; Groussin, O.; Jorda, L.; Kaasalainen, M.; Lowry, S.; Toth, I. Bibcode: 2008LPICo1405.8163L Altcode: No abstract at ADS Title: Solar cycle evolution of the magnetic topology of the corona as deduced from Lasco-C2 Authors: Llebaria, Antoine; Lamy, Philippe; Saez, Fabien Bibcode: 2008cosp...37.1812L Altcode: 2008cosp.meet.1812L The magnetic topology of the corona is clearly revealed by the structures in the corona. Its temporal evolution can therefore be analyzed using synoptic maps of the polarized radiance pB of the K-corona or the derived electron densities. In January 2008, the LASCO-C2 coronagraph aboard SOHO has completed 12 years of quasi-continuous observations of the solar corona from 2 to 6 solar radii, thus allowing a full view of the evolution of the magnetic topology over a full solar cycle. From this data set, we have produced synoptic maps of of unsurpassed spatial and temporal resolutions. The periodic sampling (2 x 14 days) of this series best shows the global evolution of the whole corona. The onset of the Sun activity period is clearly marked by increasing twists of the neutral sheet, shifting the activity to higher and higher latitudes. The neutral sheet then splits into two or more oscillating branches branches characterized by long oscillating periods. Surprisingly this situation prevails until the end of the present 23rd cycle. Short scale variations have also been analyzed and will be discussed. Title: Hubble Investigation of the B and G Fragments of Comet 73P/Schwassmann-Wachmann 3 Authors: Weaver, H. A.; Lisse, C. M.; Mutchler, M.; Lamy, P. L.; Toth, I.; Reach, W. T.; Vaubaillon, J. Bibcode: 2008LPICo1405.8248W Altcode: No abstract at ADS Title: Kuiper Belt Objects in the Planetary Region: The Jupiter-Family Comets Authors: Lowry, S.; Fitzsimmons, A.; Lamy, P.; Weissman, P. Bibcode: 2008ssbn.book..397L Altcode: Jupiter-family comets (JFCs) are a dynamically distinct group with low orbital inclinations and orbital periods ó20 yr. Their origin has been shown computationally to be the Kuiper belt region beyond Neptune. Therefore studying the nuclei of these comets, as well as their coma species, can provide valuable insights into the nature of the kilometer-sized Kuiper belt objects (KBOs). These include their size distribution, internal structure, and composition, as well as some hints at their likely surface features. Although JFCs are much closer to the Sun than KBOs, they are still very difficult to observe due to their intrinsic faintness and outgassing comae. However, observational studies are advancing rapidly and we are now starting to place valuable constraints on the bulk physical properties of these nuclei. In this chapter, we review some of the more important findings in this field and their relevance to KBO studies. Title: A Portrait of Asteroid 21 Lutetia from Visible and Infrared Observations with Ground- and Space-Based Telescopes Authors: Lamy, P. L.; Barucci, A.; Fornassier, S.; Faury, G.; Groussin, O.; Kaasalainen, M.; Jorda, L.; Mottola, S.; Toth, I. Bibcode: 2008LPICo1405.8245L Altcode: No abstract at ADS Title: Determination of Photometric Properties of Asteroid Steins Authors: Spjuth, S.; Jorda, L.; Li, J.; Keller, H. U.; Kueppers, M.; Hviid, S.; Lamy, P. Bibcode: 2008LPICo1405.8082S Altcode: No abstract at ADS Title: Asteroids 2867 Steins and 21 Lutetia: surface composition from far infrared observations with the Spitzer space telescope Authors: Barucci, M. A.; Fornasier, S.; Dotto, E.; Lamy, P. L.; Jorda, L.; Groussin, O.; Brucato, J. R.; Carvano, J.; Alvarez-Candal, A.; Cruikshank, D.; Fulchignoni, M. Bibcode: 2008A&A...477..665B Altcode: Aims:The aim of this paper is to investigate the surface composition of the two asteroids 21 Lutetia and 2867 Steins, targets of the Rosetta space mission.
Methods: We observed the two asteroids through their full rotational periods with the Infrared Spectrograph of the Spitzer Space Telescope to investigate the surface properties. The analysis of their thermal emission spectra was carried out to detect emissivity features that diagnose the surface composition.
Results: For both asteroids, the Christiansen peak, the Reststrahlen, and the Transparency features were detected. The thermal emissivity shows a clear analogy to carbonaceous chondrite meteorites, in particular to the CO-CV types for 21 Lutetia, while for 2867 Steins, already suggested as belonging to the E-type asteroids, the similarity to the enstatite achondrite meteorite is confirmed. Title: Comet Dust and Activity in the SEPPCoN Survey Authors: Kelley, M. S.; Fernández, Y. R.; A'Hearn, M. F.; Bauer, J.; Campins, H.; Fitzsimmons, A.; Groussin, O.; Lamy, P. L.; Licandro, J.; Lisse, C. M.; Lowry, S. C.; Meech, K. J.; Pittichová, J.; Reach, W. T.; Snodgrass, C.; Toth, I.; Weaver, H. A. Bibcode: 2008LPICo1405.8272K Altcode: No abstract at ADS Title: Coronal electron density over a full solar cycle - Implications for the solar wind velocity Authors: Lamy, Philippe Bibcode: 2008cosp...37.1687L Altcode: 2008cosp.meet.1687L In January 2008, the LASCO-C2 coronagraph aboard SOHO has completed 12 years of quasicontinuous observations of the solar corona from 2 to 6 solar radii, that is over a full solar cycle. We study the temporal evolution of the electron density derived from the calibrated pB images over this unsurpassed time span, first globally, and then by distinguishing different latitude intervals so as to characterize the the equatorial and polar regions. The local density moderately increases with activity (factor 2), as the bulk of the increase essentially results from the development of new sources associated to emerging neutral or current sheets. We extensively study different typical structures of the corona, polar and trans-equatorial holes and the streamer belt to constrain the velocity profiles of different regimes of solar wind. Finally we combine LASCO-C2 density profiles, SWAN mass flux data and interplanetary solar wind velocities derived from ground-based Interplanetary Scintillation Observations (IPS) to conclude that the fast solar wind reaches its terminal velocity about 6 solar radii, and expands with constant velocity beyond this distance, while the slow solar wind reaches only half its terminal velocity value at this distance and thus continues its acceleration further out. Title: Three-dimensional reconstruction of Coronal Mass Ejections using STEREO/SECCHI-COR2 and SoHO/LASCO-C2 data. Authors: Boursier, Yannick; Lamy, Philippe; Saez, Fabien; Llebaria, Antoine Bibcode: 2008cosp...37..361B Altcode: 2008cosp.meet..361B We present a new method to perform the three-dimensional reconstruction of CMEs using stereoscopic images obtained with the STEREO/SECCHI-COR2 coronagraph, as well as images from the SoHO/LASCO-C2 and C3 coronagraphs. Our algorithm is based on a forward modeling approach appropriate to the reconstruction of surfaces in optically thin medium. It involves four main steps : i) definition of three distinct geometrical and representative models of CMEs (spherical shell, fluxrope, cloud-like), ii) generation of a library of simulated images, iii) local approximation of the observed CME by a sphere shell for a first estimate of the parameters, iv) determination of the model in the library that best fits the observed CME . The comparison between simulated and observed images is based on purely geometrical criteria and geometric invariants. The algorithm provides two estimates of the direction of propagation, an estimate of the velocity profile, and the set of parameters which define the shape and the orientation of the CME for space weather forecast. Uncertainties on the direction of propagation are derived from error measurement on the images. We have applied our algorithm to a set of CMEs observed in 2007, and when possible, our results are compared with those coming from the Geometric Localization Method (Pizzo and Biesecker, 2004 ; de Koning, C. A.; Pizzo, V. J.; Biesecker, D. A., 2007). Finally an identification of the source regions have been performed. Title: The Size, Thermal Inertia and Water Production Rate of Comet 8P/Tuttle Authors: Groussin, O.; Kelley, M. S.; Fernández, Y. R.; Jorda, L.; Lamy, P. L.; Toth, I.; Weaver, H. A. Bibcode: 2008LPICo1405.8035G Altcode: No abstract at ADS Title: Phase Angle Effects on Sungrazing Comets Observed by SOHO Authors: Knight, M. M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.; Hamilton, D. P.; Lamy, P.; Llebaria, A. Bibcode: 2008LPICo1405.8143K Altcode: No abstract at ADS Title: Solar Astrophysics, Interferometry, and Coronagraphy at DomeC/Concordia Authors: Damé, L.; Amans, J. -P.; Dournaux, J. -L.; Koutchmy, S.; Lamy, P.; Preumont, A. Bibcode: 2008EAS....33..105D Altcode: Excellent seeing, coronal conditions, and very low IR thermal background are qualities of the Dome C/Concordia station site that will allow unique solar astrophysics science. We review the science case for inner corona observations (onset of the coronal heating mechanism still poorly understood) and the promises of high angular resolution to disentangle the possible mechanisms at work between waves, convection, and reconnection in this particularly magnetically structured solar atmosphere between the high chromosphere and inner corona. For coronagraphy, IR and high resolution possibilities, Dome C is a case by itself between classical ground-based sites and space opportunities. Telescopes from 50 cm (coronagraphy oriented) to 4 m (full high resolution advantage including IR access) are proposed to benefit from these remarkable observing capabilities. Using 3×O50 cm off-axis telescopes, we first propose a medium size facility (1.4 m equivalent telescope) for very high resolution access, ADSIIC (Antarctica Demonstrator of Solar Interferometric Imaging & Coronagraphy), before the ultimate 9-telescope Solar Facility equivalent to a 4 m diameter telescope: A-FOURMI (Antarctica 4 m Interferometer). Finally, 30 m tower designs and their logistics using standard containers and elementary elements of 6 m maximum length, are presented and discussed. These towers are indeed of general interest also for the other optical and IR telescopes intended for Dome C/Concordia, allowing to get over most of the turbulent ground layer and to reach the best possible permanent seeing conditions (better than half an arcsec). Title: Three-dimensional structure of white light polar Plumes at the beginning and at the end of Solar Cycle 23 Authors: Boursier, Yannick; Llebaria, Antoine; Lamy, Philippe Bibcode: 2008cosp...37..362B Altcode: 2008cosp.meet..362B In spite of a large set of observations from spatial instruments, the 3D structure of polar plumes remains an open question. Even if the connection between plumes observed in the EUV and WL seems globally established, their dynamics and the one-to-one relationship remains unclear. We first examine and compare high cadence observations obtained in March 1997 and in March 2006 by the well know method of sinogram, and find a pronounced similarity. We then implement a forward model, introducing a fractal distribution of the electron density, and show that it provides a better agreement to the observations than classical models such as curtains or columns of plasma, at least from the geometric and photometric points of view. Title: Results from SEPPCoN, A Survey of Ensemble Physical Properties of Cometary Nuclei Authors: Fernández, Y. R.; Kelley, M. S.; Lamy, P. L.; Toth, I.; Groussin, O.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.; Fitzsimmons, A.; Licandro, J.; Lisse, C. M.; Lowry, S. C.; Meech, K. J.; Pittichová, J.; Reach, W. T.; Snodgrass, C.; Weaver, H. A. Bibcode: 2008LPICo1405.8307F Altcode: No abstract at ADS Title: Characterization of the Nucleus Fragment 73P/Schwassmann-Wachmann 3-C from Hubble Space Telescope Observation in 2001 and 2006 Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Noll, K. S. Bibcode: 2008LPICo1405.8160L Altcode: No abstract at ADS Title: Commission 21: Light of the Night Sky Authors: Gustafson, Bo A. S.; Witt, Adolf N.; Lamy, Philippe; Dwek, Eli; Lamy, Philippe; Henry, Richard C.; Mann, Ingrid Bibcode: 2007IAUTB..26..138G Altcode: Applications have been received from Dr. Peter Wheatley (proposed by UK), Prof. Harald Schuh (proposed by Austria), and Dr. Busaba Kramer (proposed by Thailand). All applications were endorsed, with the caveat that Dr. Kramer's application needs to be endorsed by at least one of the other commissions since she has not a publication record in our field. Title: Recent Evolution of the Kracht Group of Comets Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.; Hamilton, D. P.; Lamy, P.; Llebaria, A. Bibcode: 2007AAS...211.8504K Altcode: 2007BAAS...39Q.877K The Kracht group contains 29 comets discovered in SOHO images from 1996-2005 with perihelion distances of 7-11 solar radii and inclinations of 12-15 degrees. Unlike the much more populous Kreutz sungrazing group, many Kracht comets are observed to survive perihelion, and as many as five may have been observed on two apparitions, with periods ranging from 4.8-5.8 years. Kracht comets tend to arrive in clusters followed by many months devoid of comets before another cluster arrives. Ohtsuka et al. (2003) and Sekanina and Chodas (2005) have shown that the Kracht group represents an evolutionary stage of the Machholz complex, which has evolved over many centuries and also includes 96P/Machholz 1, the Marsden group of comets, the Daytime Arietids, and the Southern delta Aquarids.

Here we explain the recent evolution of individual members of the Kracht group as a series of cascading fragmentations of a few large comets (causing the temporal clusters) which have had somewhat different orbital histories since splitting from each other within the last hundred years or so (causing the gaps between temporal clusters). We use dynamical simulations to search for possible fragmentation scenarios and to estimate the rate at which the orbital elements evolve due to the gravitational influence of the planets. We predict that 8 of the 19 fragments seen since 2002 may be observable in upcoming perihelion passages, including five that should reappear before the end of 2008. If observed, two of these will have been seen at three perihelion passages, allowing a rough estimation of the mass loss due to erosion.

This research was supported by NASA Planetary Atmospheres grant NNG06GF29G. Title: Results From SEPPCoN, a Survey to Study the Physical Properties of the Nuclei and Dust of Jupiter-Family Comets Authors: Fernandez, Yanga R.; Kelley, M. S.; Lamy, P. L.; Reach, W. T.; Toth, I.; Groussin, O.; Lisse, C. M.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.; Fitzsimmons, A.; Licandro, J.; Lowry, S. C.; Meech, K. J.; Pittichova, J.; Weaver, H. A. Bibcode: 2007AAS...211.5602F Altcode: 2007BAAS...39..827F We present results from SEPPCoN, our Survey of Ensemble Physical Properties of Cometary Nuclei. This survey involves studying 100 Jupiter-family comets (JFCs) -- about 30% of the known population -- using the Spitzer Space Telescope for mid-infrared measurements of thermal emission and several ground-based telescopes for visible-wavelength measurements of reflected sunlight. The Spitzer observations (imaging with IRS PU and MIPS) are complete, and the ground-based observations (imaging in at least R band) are about half complete. Almost all our targets are imaged while farther than 4 AU from the Sun, to minimize (and often eliminate) confusion caused by dust from cometary activity. The Spitzer data constrain the effective radii of the JFC nuclei and thus give us an independent measurement of the cumulative size distribution (CSD). We find preliminarily that the CSD power-law slope is similar to what has been found by others using visible wavelength studies, suggesting that there is no strong trend of albedo with size. The Spitzer data also tell us about the JFC thermal inertia, and we find that many -- though not all -- cometary nuclei seem to have low values of this, consistent with a porous, fluffy, poorly-conducting, dusty surface layer. To our surprise, the Spitzer images show that about one-third of our sample appeared with extended dust emission despite being close to aphelion, and in many cases the dust originated from cometary activity happening right then. Interestingly, we find that the activity observed at these distances seems to turn off rather abruptly once a JFC passes aphelion. We have used dynamical analysis to constrain the dust grain sizes and thereby distinguish dust tails from dust trails. The dust temperatures are in most cases consistent with isothermal, low-albedo grains in LTE. We thank the Spitzer Science Center for supporting this research. Title: Velocity Profiles in the Solar Corona from Multi-Instrument Observations Authors: Quémerais, E.; Lallement, R.; Koutroumpa, D.; Lamy, P. Bibcode: 2007ApJ...667.1229Q Altcode: 2007arXiv0706.1913Q We present a method to derive outflow velocities in the solar corona using different data sets, including solar wind mass flux coming from the SWAN SOHO instrument, electron density values from LASCO-C2, and interplanetary solar wind velocities derived from ground-based interplanetary scintillation observations (IPS). In a first step, we combine the LASCO electron densities at 6 Rsolar and the IPS velocities and compare the product to the SWAN mass fluxes. It is found that this product represents the actual mass flux at 6 Rsolar for the fast wind, but not for the slow wind. In regions dominated by the slow wind, the fluxes derived from SWAN are systematically smaller. This is interpreted as proof that the fast solar wind has reached its terminal velocity at ~6 Rsolar and expands with constant velocity beyond this distance. On the contrary, the slow solar wind has reached only half of its terminal value and is thus accelerated farther out. In a second step, we combine the LASCO-C2 density profiles and the SWAN flux data to derive velocity profiles in the corona between 2.5 and 6 Rsolar. Such profiles can be used to test models of the acceleration mechanism of the fast solar wind. Title: Recent Evolution of the Kracht Group of Comets Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.; Hamilton, D. P.; Lamy, P.; Llebaria, A. Bibcode: 2007DPS....39.5903K Altcode: 2007BAAS...39..534K The Kracht group contains 29 comets discovered in SOHO images from 1996-2005 with perihelion distances of 7-11 solar radii and inclinations of 12-15 degrees. Unlike the much more populous Kreutz sungrazing group, many Kracht comets are observed to survive perihelion, and as many as five may have been observed on two apparitions, with periods ranging from 4.8-5.8 years. Kracht comets tend to arrive in clusters followed by many months devoid of comets before another cluster arrives. Ohtsuka et al. (2003) and Sekanina and Chodas (2005) have shown that the Kracht group represents an evolutionary stage of the Machholz complex, which has evolved over many centuries and also includes 96P/Machholz, the Marsden group of comets, and the Arietids.

Here we explain the recent evolution of individual members of the Kracht group as a series of cascading fragmentations of a few large comets (causing the temporal clusters) which have had somewhat different orbital histories since splitting from each other within the last hundred years or so (causing the gaps between temporal clusters). We use dynamical simulations to search for possible fragmentation scenarios and to estimate the rate at which the orbital elements evolve due to the gravitational influence of the planets. We predict that 8 of the 19 fragments seen since 2002 may be observable in upcoming perihelion passages, including five that should reappear before the end of 2008. If observed, two of these will have been seen at three perihelion passages, allowing a rough estimation of the mass loss due to erosion.

This research was supported by NASA Planetary Atmospheres grant NNG06GF29G. Title: SEPPCoN: Comet Dust and Activity at Moderate Heliocentric Distances as Observed with Spitzer Authors: Kelley, Michael S.; Fernández, Y. R.; Reach, W. T.; Lisse, C. M.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.; Fitzsimmons, A.; Groussin, O.; Lamy, P. L.; Licandro, J.; Lowry, S. C.; Meech, K. J.; Pittichova, J.; Toth, I.; Weaver, H. A. Bibcode: 2007DPS....39.5407K Altcode: 2007BAAS...39..525K A Survey of Ensemble Physical Properties of Cometary Nuclei (SEPPCoN) is underway to characterize the nuclei of 100 Jupiter-family comets (JFC). The survey combines both visible and mid-infrared observations to measure the JFC size and albedo distributions. We inspected Spitzer Space Telescope MIPS and IRS images of the survey targets for dust comae, tails, and trails. Out of 98 observed comets, we found 32 to have some emission from dust outside of the central point source. A few of these sources were also observed to have dust in visible, ground-based data. The heliocentric distances (rh) of the 32 targets range from 3.5 to 6.5 AU, with most between 4 and 5 AU. We derive color-temperatures for the 20 dust detections observed in both the 16 and 22 micron IRS cameras and find the color-temperature approximately varies as 280*rh^(-0.5) [K], as expected for isothermal low-albedo dust in local thermodynamic equilibrium. We discuss the evidence for outliers from this trend. We compare our observations to dust syndynes and 3-dimensional dust models to distinguish dust trails from dust tails. Unlike dust tails, dust trails only weakly respond to solar radiation pressure and, therefore, likely represent the largest (> 1 mm) grains ejected from the nucleus. We also compare observations to model images in order to determine the extent of recent coma activity. Water sublimation is expected to be greatly extinguished on comet surfaces by 3.5 AU. Dust structures observed outside of this rh could arise from recent coma activity (timescales up to weeks) caused by the sublimation of highly volatile ices (such as CO2) or the crystallization of amorphous water ice. Alternatively, the observed dust may be slowly dispersing grains ejected at a much earlier epoch (timescales up to years) when water sublimation dominated coma activity. Title: Three-dimensional reconstruction of the streamer belt and other large-scale structures of the solar corona. I. Method Authors: Saez, F.; Llebaria, A.; Lamy, P.; Vibert, D. Bibcode: 2007A&A...473..265S Altcode: Context: The high spatial resolution, white-light images obtained by the LASCO coronagraphs provide a detailed record of the solar corona over almost a full solar cycle. Their analysis and interpretation poses a formidable challenge for ultimately retrieving the 3-dimensional distribution of electrons in the corona.
Aims: Our goal is to implement an efficient forward modeling method capable of generating high-resolution synthetic images of large-scale coronal structures (the streamer belt, isolated streamers, coronal mass ejections) over any time scales (as long as a solar cycle) to be directly compared, both qualitatively and quantitatively, to coronographic images of the corona.
Methods: Our model assumes a 3-dimensional distribution of electrons described by analytic functions and represented using the octree compression's techniques. The radiance of the synthetic images is calculated with a ray-tracing algorithm that incorporates the Thomson scattering. A multi-octree generalization of the method allows simulation of the temporal evolution of the structures. We first concentrate on the coronal streamer belt. Starting from photospheric magnetograms, we calculate the position of the neutral line at the source surface (2.5 R_sun) using the potential field source surface model. The plasma sheet forming the belt is centered on the current sheet represented as the radial extension of the neutral line. Its electron density is represented by a parametric function of both the distances to the Sun center and to the current sheet. The parameters are optimized by adjusting the synthetic images to the observations, using either the coronal images or synoptic maps of the corona. The method is then extended to other large-scale coronal structures, polar plumes, and coronal mass ejections.
Results: As examples, we present results for the streamer belt observed by LASCO-C2 during two Carrington rotations, CR 1910 and CR 1913, as well as illustrations of future coronographic observations expected from the STEREO and Solar Orbiter missions. The results suggest that our method is sufficient for qualitatively and quantitatively simulating the structures of the solar corona even if some discrepancies can be noticed. A systematic analysis of the LASCO data over almost a full solar cycle will be developed in forthcoming articles. Title: Thermal Properties, Size Distribution, and Albedo Distribution of Jupiter-Family Comets Authors: Fernandez, Yanga R.; Kelley, M. S.; Lamy, P. L.; Toth, I.; Groussin, O.; Lisse, C. M.; A'Hearn, M. F.; Bauer, J. M.; Campins, H.; Fitzsimmons, A.; Licandro, J.; Lowry, S. C.; Meech, K. J.; Pittichova, J.; Reach, W. T.; Weaver, H. A. Bibcode: 2007DPS....39.4301F Altcode: 2007BAAS...39..497F We present results from SEPPCoN (Survey of Ensemble Physical Properties of Cometary Nuclei), a survey of 100 Jupiter-family comets (JFCs) using the Spitzer Space Telescope for mid-infrared measurements of thermal emission and several ground-based telescopes for visible-wavelength measurements of reflected sunlight. Our sample represents about 30% of all known JFCs. The Spitzer observations are complete, and each comet was observed at either two wavelengths (16 and 22 μm) or at one wavelength twice (24 μm). Our survey constrains the effective radii of the JFC nuclei and thence the size distribution while only assuming that cometary geometric albedos are low (few percent); we need not assume that they are all the same. Also, nearly all survey targets were observed when farther than 4 AU from the Sun to minimize (and in most cases eliminate) coma confusion. Using the observations of comets at two wavelengths, and using the Near-Earth Asteroid Thermal Model, we have estimated the JFC ensemble-average beaming parameter to be about 1.1. On average, cometary nuclei seem to have low thermal inertia and not have significant infrared beaming, although we do find that some of our survey targets have significantly higher parameters and thus likely higher thermal inertia. Analysis on the cumulative size distribution continues and we present our preliminary estimate of its shape, as well as the implications for the assumption of uniform albedo and for the extent of the small-comet (sub-km) population. So far we have obtained visible magnitudes on almost half of our targets; we plan to complete this part of the survey in the coming years. With these data we will constrain the JFC albedo distribution and again address the question of albedo uniformity; current progress on this task is reported as well. We thank the Spitzer Science Center for supporting this research. Title: Active Regions On The Nucleus Of Comet 67P/Churyumov-Gerasimenko Authors: Groussin, Olivier; Lamy, P.; Jorda, L.; Besse, S. Bibcode: 2007DPS....39.3601G Altcode: 2007BAAS...39..485G Rosetta will orbit and land on comet 67P/Churyumov-Gerasimenko in 2014. The planning of the mission depends strongly on the location and intensity of active regions. We have developped a model to calculate the water production rate of 67P as a function of heliocentric distance. Our model takes into account the orbital elements of 67P, the orientation of the pole, the rotational period, the shape (spherical or more complex) and the localisation and type of active regions (either small, very active regions or extended, low active regions). The comparison between the water production rates calculated by the model and the compilation of water production rates from the 1982 and 1996 perihelion passages by D.G. Schleicher (2006, Icarus 181, 442-457) gives some constraints on the localisation of active regions. A particular emphasis is placed on reproducing the rotational variability of the water production rate.

We derive that one small very active region covering about 4-5% of the nucleus surface and located in the Northern hemisphere at a latitude of about +65 degree is sufficient to match the data and their temporal variations. Two small active regions located in the Northern hemisphere is not excluded but less probable. One extended, low active region covering about 60% of the nucleus surface can also fit the data, but only the part in the Northern hemisphere contributes to the production rate at perihelion. The case with one region only, located in the Southern hemisphere, is excluded, so that there must be active regions in the Northern hemisphere of 67P. Finally, we conclude that the shape (spherical or more complex) has no influence on the localisation of the active regions.

This work was supported by a grant from the CNES. Title: The giant externally occulted coronagraph ASPIICS for the PROBA-3 formation flying mission Authors: Vivès, Sébastien; Lamy, Philippe; Venet, Melanie; Levacher, Patrick; Boit, J. L. Bibcode: 2007SPIE.6689E..0FV Altcode: 2007SPIE.6689E..11V Formation flying opens new perspectives in solar physics, and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at a distance of hundred meters. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interferometrie de la Couronne Solaire) is a mission proposed to ESA in the framework of its PROBA-3 demonstration program of formation flying which is presently in phase A. ASPIICS is a single coronagraph which will perform both high spatial resolution imaging of the solar corona as well as 2-dimensional spectroscopy of several emission lines from the coronal base out to 3 R(symbol) using an etalon Fabry-Perot interferometer. The selected lines will allow to address different coronal regions: the forbidden line of FeXIV at 530.285 nm (hot coronal matter), Fe IX/X at 637.4 nm (coronal holes), HeI at 587.6 nm (cold matter). An additional broad spectral channel will image the white light corona so as to derive electron densities. The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the detection of the very inner corona as close as 0.01 R(symbol) from the solar limb. Title: The BepiColombo Laser Altimeter (BELA): Concept and baseline design Authors: Thomas, N.; Spohn, T.; Barriot, J. -P.; Benz, W.; Beutler, G.; Christensen, U.; Dehant, V.; Fallnich, C.; Giardini, D.; Groussin, O.; Gunderson, K.; Hauber, E.; Hilchenbach, M.; Iess, L.; Lamy, P.; Lara, L. -M.; Lognonné, P.; Lopez-Moreno, J. J.; Michaelis, H.; Oberst, J.; Resendes, D.; Reynaud, J. -L.; Rodrigo, R.; Sasaki, S.; Seiferlin, K.; Wieczorek, M.; Whitby, J. Bibcode: 2007P&SS...55.1398T Altcode: The BepiColombo Laser Altimeter (BELA) has been selected for flight on board the European Space Agency's BepiColombo Mercury Planetary Orbiter (MPO). The experiment is intended to be Europe's first planetary laser altimeter system. Although the proposed system has similarities to the Mercury Laser Altimeter (MLA) currently flying on board NASA's MESSENGER mission to Mercury, the specific orbit and construction of the MPO force the use of novel concepts for BELA. Furthermore, the base-lined range-finding approach is novel. In this paper, we describe the BELA system and show preliminary results from some prototype testing. Title: Old and New Aspects of Prominence Physics from Coronal Observations Authors: Koutchmy, S.; Filippov, B.; Lamy, P. Bibcode: 2007ASPC..368..331K Altcode: Classical W-L eclipse observations at typical spatial resolution of 10 arcsec show dark cavities surrounding prominences. Images at higher spatial resolution processed with a spatial filter reveal small dynamical cool clouds moving inside the inner corona around prominences. More recently EIT/SoHO observations taken using the 304 Å channel showed He+ prominences sometimes not seen in cooler lines. TRACE movies of the Fe IX and XI emissions where prominences are seen in absorption also bring appreciable informations on the dynamical surrounding of prominences, without showing obvious correlations between prominence and coronal structures. Accordingly, we re-examine the significance of the cavity and propose a possible interpretation as magnetic interlaced 3-D flux ropes and loops evacuating the corona, in addition to twisted flux ropes where the prominence plasma is condensing. Future space missions like ASPIICS should pay more attention to cavities and emptiness, to coronal dynamics around prominences, in order to resolve the long-standing problem of the origin of prominences and perhaps, perform a new diagnostic of the erupting process responsible for many CMEs. Title: Characterization of Asteroid 2867 Steins, a Target of the Rosetta Mission Authors: Lamy, Philippe; Barucci, Antonella; Dotto, Elisabetta; Fornasier, Sonia; Fulchignoni, Marcello; Groussin, Olivier; Jorda, Laurent Bibcode: 2007sptz.prop40259L Altcode: We propose to re-observe asteroids 2867 Steins, one of the target of the Rosetta mission in order to definitevely ascertain its taxonomic classification and its surface composition. Our previous SST observations performed during cycle 2 had to assume a much bigger size than presently established, and our spectra do not have a good enough signal-over-noise ratio to clearly distinguish the exact position of the different bands. The proposed SST observations consist in taking low resolution spectra with the IRS instrument over its full wavelength range 5-38 micron so as to reach a signal-over-noise ratio larger than 200 in the 7-20 micron spectral range which is of prime interest for identification of the mineralogical features. Five individual spectra will be obtained for a total observing time of 1.4 hr. The expected results will allow identifying the mineralogical signatures so as to determine the taxonomic classification, the surface composition and possible weathering processes. Title: Chromospheric and Prominence Physics with the ASPIICS Formation Flying Coronagraph Authors: Lamy, P.; Vivès, S.; Koutchmy, S.; Arnaud, J. Bibcode: 2007ASPC..368..639L Altcode: Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent observing the inner corona inside typically 2--2.5 solar radii (R⊙). Formation flying opens new perspectives and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) is a mission proposed to ESA in the framework of the PROBA-3 program of formation flying which is presently under study, to exploit this technique for coronal observations. ASPIICS is composed of a single coronagraph which performs high spatial resolution imaging of the corona as well as 2-dimensional spectroscopy of several emission lines (in particular the forbidden line of Fe XIV at 530.285 nm) from the coronal base out to 3 R⊙. The classical design of an externally occulted coronagraph is adapted to the detection of the very inner corona, and the addition of a Fabry-Pérot interferometer. By tuning the position of the occulter spacecraft, it will be possible to reach the chromosphere and the upper part of the spicules. Filtergrams on the helium D3 line or even better, the hydrogen Hβ line (which is optically thin contrary to Hα) will give access to the ``cold corona'', and could allow measuring the chromospheric prolateness. Title: Measuring the physical properties of the nucleus of comet 8P/Tuttle Authors: Groussin, Olivier; Fernandez, Yanga; Jorda, Laurent; Kelley, Michael; Lamy, Philippe; Toth, Imre; Weaver, Hal Bibcode: 2007sptz.prop40270G Altcode: Comet 8P/Tuttle is a returning nearly isotropic comet (NIC), i.e., an 'Oort cloud comet', with an outstanding apparition in cycle 4, passing within 0.25 AU of the Earth. We propose to observe it with MIPS (photometry at 24 and 70 micron) and IRS (spectroscopy in the 5-38 micron range), to measure the physical properties of its nucleus: size, shape, rotation period, thermal inertia and mineralogy. This will provide the most detailed view of a NIC nucleus since the spacecraft flyby of 1P/Halley in 1986. The return of 8P is a rare opportunity that Spitzer should not miss. The results should yield a comprehensive picture of this NIC that can be compared to the detailed data collected on ecliptic comets (ECs) during the past 3 decades. The differences and similarities between NICs and ECs should yield valuable insights into the origin and evolution of comets. Title: The long-term evolution and initial size of comets 46P/Wirtanen and 67P/Churyumov-Gerasimenko Authors: Groussin, O.; Hahn, G.; Lamy, P. L.; Gonczi, R.; Valsecchi, G. B. Bibcode: 2007MNRAS.376.1399G Altcode: 2007MNRAS.tmp..179G We present a new method to study the long-term evolution of cometary nuclei in order to estimate their original size, and we consider the case of comets 46P/Wirtanen (hereafter 46P) and 67P/Churyumov-Gerasimenko (hereafter 67P). We calculate the past evolution of the orbital elements of both comets over 100000yr using a Bulirsch-Stoer integrator and over 450000yr using a Radau integrator, and we incorporate a realistic model of the erosion of their nucleus. Their long-term orbital evolution is prominently chaotic, resulting from several close encounters with planets, and this result is independent of the choice of the integrator and of the presence or not of non-gravitational forces. The dynamical lifetime of comet 46P is estimated at ~133000yr and that of comet 67P at ~105000yr. Our erosion model assumes a spherical nucleus composed of a macroscopic mixture of two thermally decoupled components, dust and pure water ice. Erosion strongly depends upon the active fraction and the density of the nucleus. It mainly takes place at heliocentric distances <4au and lasts for only ~7 per cent of the lifetime. Assuming a density of 300kgm-3 and an average active fraction over time of 10 per cent, we find an initial radius of ~1.3km for 46P and ~2.8km for 67P. Upper limit are obtained assuming a density of 100kgm-3 and an active fraction of 100 per cent, and amounts to 21km for 46P and 25km for 67P. Erosion acts as a rejuvenating process of the surface so that exposed materials on the surface may only contain very little quantities of primordial materials. However, materials located just under it (a few centimetres to metres) may still be much less evolved. We will apply this method to several other comets in the future. Title: Rotational state of the nucleus of Comet 9P/Tempel 1: Results from Hubble Space Telescope observations in 2004 Authors: Lamy, Philippe L.; Toth, Imre; A'Hearn, Michael F.; Weaver, Harold A.; Jorda, Laurent Bibcode: 2007Icar..187..132L Altcode: The nucleus of Comet 9P/Tempel 1 was first observed with the Hubble Space Telescope (HST) in December 1997 [Lamy, P., Toth, I., A'Hearn, M.F., Weaver, H., Weissman, P.R., 2001. Icarus 154, 337-344], but the temporal coverage was insufficient to determine its rotational period. Because the success of the Deep Impact mission was critically dependent on understanding the rotational state and approximate shape and size of the nucleus, we extensively re-observed 9P/Tempel 1, this time with the Advanced Camera for Surveys (HST/ACS), from May 7.9 to 9.5, 2004 (UT). At the mid-point of the observing window, the comet was 3.52 AU from the Sun, 4.03 AU from the Earth, and at a solar phase angle of 13.3°. The program was comprised of 18 separate visits, each one corresponding to an HST orbit filled with 3 ACS exposures of either 800 or 857 s duration with the F606W broadband filter. These very deep exposures revealed a star-like object, without any apparent coma. The light curve, defined by 49 data points, is characterized by a mean apparent V magnitude of 21.8 and an amplitude of 0.5 mag, indicating that we were viewing the varying cross-section of a rotating, elongated body. The periodicity was analyzed with seven different techniques yielding a rotational period in the range 39.40 to 43.00 h, and a mean value of 41.27±1.85 h (1 σ). Using an albedo p=0.04 and a linear phase law with a coefficient β=0.0465 magdeg, we determined an effective radius of 3.01 km; a possible prolate spheroid solution has semi-axes a=3.71 km, b=2.36 km and a minimum axial ratio a/b∼1.57. By comparing the light curves obtained in 1997 and in 2004, we were able to constrain the phase function of the nucleus. Finally, an upper limit of Afρ<0.04 cm is set based on the non-detection of the coma. Title: Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta Authors: Keller, Horst Uwe; Küppers, Michael; Fornasier, Sonia; Gutiérrez, Pedro J.; Hviid, Stubbe F.; Jorda, Laurent; Knollenberg, Jörg; Lowry, Stephen C.; Rengel, Miriam; Bertini, Ivano; Cremonese, Gabriele; Ip, Wing-H.; Koschny, Detlef; Kramm, Rainer; Kührt, Ekkehard; Lara, Luisa-Maria; Sierks, Holger; Thomas, Nicolas; Barbieri, Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; A'Hearn, Michael F.; Angrilli, Francesco; Barucci, Maria-Antonella; Bertaux, Jean-Loup; da Deppo, Vania; Davidsson, Björn J. R.; de Cecco, Mariolino; Debei, Stefano; Fulle, Marco; Gliem, Fritz; Groussin, Olivier; Lopez Moreno, José J.; Marzari, Francesco; Naletto, Giampiero; Sabau, Lola; Sanz Andrés, Angel; Wenzel, Klaus-Peter Bibcode: 2007Icar..187...87K Altcode: The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impact projectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showed regular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness of Tempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structures were created by the impact. Most of the material moved with ∼200ms. Much of it left the comet in the form of icy grains which sublimated and fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet ( 4.5-9×10kg of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions with gas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations of the density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain. Title: Properties of the dust cloud caused by the Deep Impact experiment Authors: Jorda, L.; Lamy, P.; Faury, G.; Keller, H. U.; Hviid, S.; Küppers, M.; Koschny, D.; Lecacheux, J.; Gutiérrez, P.; Lara, L. M. Bibcode: 2007Icar..187..208J Altcode: We present an analysis of the observations of the Deep Impact event performed by the OSIRIS narrow angle camera aboard the Rosetta spacecraft over two weeks, in an effort to characterize the cometary dust grains ejected from the nucleus of Comet 9P/Tempel 1. We adopt a Monte Carlo approach to generate calibrated synthetic images, and a linear combination of them is fitted to the calibrated images so as to determine the physical parameters of the dust cloud. Our model considers spherical olivine particles with a density of 3780 kg m -3. It incorporates constraints on the direction of the cone of emission coming from additional images obtained at Pic du Midi observatory, and constraints on the dust terminal velocities coming from the physics of the impact. We find that the slope of the differential dust size distribution of grains with radii <20 μm ( β>0.008) is 3.1±0.3, a value typical of cometary dust tails. This shows that there is no evidence in our data for an enhancement in sub-micron particles in the ejecta compared to the typical dust distribution of active comets. We estimate the mass of particles with radii <1.4 μm ( β>0.14) to be 1.5±0.2×10 kg. These particles represent more than 80% of the cross-section of the observed dust cloud. The mass carried by larger particles depends whether the gas significantly increases the kinetic energy of the grains in the inner coma; it lies in the range 1-14×10 kg for particles with radii <100 μm ( β>0.002). We obtain the distribution of terminal velocities reached by the dust after the dust-gas interaction which is very well constrained between 10 and 600 m s -1. It is characterized by Gaussian with a maximum at about 190 m s -1 and a width at half maximum of 150 m s -1. Title: Commission 21: Light of the Night Sky Authors: Gustafson, Bo Å. S.; Witt, Adolf N.; Dwek, E.; Lamy, P.; Henry, R.; Mann, I. Bibcode: 2007IAUTA..26..161G Altcode: Commission 21, one of IAU's smallest commissions, consists of some hundred members and consultants working to understand and describe the light of the night sky with emphasis on the diffuse components. Many more work on these topics without being members of the commission. Light is here defined in its broader sense of electromagnetic radiation of any frequency. The diffuse components of the light of the night sky encompass a variety of physical phenomena over the full range of cosmic distance scales and include scattered light, thermal emission, line emission, and any other emission phenomena producing a diffuse light source. These attract interest not only as scientific topics of study in their own right but also as an unwanted foreground or background against which all other sky phenomena are observed. Commission 21 has for mandate to promote research and availability of results on issues related to the diffuse light of the night sky. This document is a report on activities in this field and is not confined to the activities of its members, no distinction is made between work carried out by commission members and non commission members. The report is organized starting with a summary of the state of broad surveys that provide most of the observations. The report on developments in the various disciplines start with the sources closest to the observer known as airglow and progresses by way of the interplanetary and interstellar mediums to the increasingly distant integrated starlight, diffuse galactic light and diffuse emission in other galaxies ending with the extragalactic background radiation. Title: OSIRIS The Scientific Camera System Onboard Rosetta Authors: Keller, H. U.; Barbieri, C.; Lamy, P.; Rickman, H.; Rodrigo, R.; Wenzel, K. -P.; Sierks, H.; A'Hearn, M. F.; Angrilli, F.; Angulo, M.; Bailey, M. E.; Barthol, P.; Barucci, M. A.; Bertaux, J. -L.; Bianchini, G.; Boit, J. -L.; Brown, V.; Burns, J. A.; Büttner, I.; Castro, J. M.; Cremonese, G.; Curdt, W.; Deppo, V. Da; Debei, S.; Cecco, M. De; Dohlen, K.; Fornasier, S.; Fulle, M.; Germerott, D.; Gliem, F.; Guizzo, G. P.; Hviid, S. F.; Ip, W. -H.; Jorda, L.; Koschny, D.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Llebaria, A.; López, A.; López-Jimenez, A.; López-Moreno, J.; Meller, R.; Michalik, H.; Michelena, M. D.; Müller, R.; Naletto, G.; Origné, A.; Parzianello, G.; Pertile, M.; Quintana, C.; Ragazzoni, R.; Ramous, P.; Reiche, K. -U.; Reina, M.; Rodríguez, J.; Rousset, G.; Sabau, L.; Sanz, A.; Sivan, J. -P.; Stöckner, K.; Tabero, J.; Telljohann, U.; Thomas, N.; Timon, V.; Tomasch, G.; Wittrock, T.; Zaccariotto, M. Bibcode: 2007SSRv..128..433K Altcode: 2007SSRv..tmp...26K The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm px−1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma. Title: Civa Authors: Bibring, J. -P.; Lamy, P.; Langevin, Y.; Soufflot, A.; Berthé, M.; Borg, J.; Poulet, F.; Mottola, S. Bibcode: 2007SSRv..128..397B Altcode: 2007SSRv..tmp...81B CIVA (Comet Infrared and Visible Analyser) is an integrated set of imaging instruments, designed to characterize the 360∘ panorama (CIVA-P) as seen from the Rosetta Lander Philae, and to study surface and subsurface samples (CIVA-M). CIVA-P is a panoramic stereo camera, while CIVA-M is an optical microscope coupled to a near infrared microscopic hyperspectral imager. CIVA shares a common Imaging Main Electronics (IME) with ROLIS. CIVA-P will characterize the landing site, with an angular sampling (IFOV) of 1.1 mrad: each pixel will image a 1 mm size feature at the distance of the landing legs, and a few metres at the local horizon. The panorama will be mapped by 6 identical miniaturized micro-cameras covering contiguous FOV, with their optical axis 60∘ apart. Stereoscopic capability will be provided by an additional micro-camera, identical to and co-aligned with one of the panoramic micro-camera, with its optical axis displaced by 10 cm. CIVA-M combines two ultra-compact and miniaturised microscopes, one operating in the visible and one constituting an IR hyperspectral imaging spectrometer: they will characterize, by non-destructive analyses, the texture, the albedo, the molecular and the mineralogical composition of each of the samples provided by the Sample Drill and Distribution (SD2) system. For the optical microscope, the spatial sampling is 7 μm; for the IR, the spectral range (1-4 μm) and the spectral sampling (5 nm) have been chosen to allow identification of most minerals, ices and organics, on each pixel, 40 μm in size. After being studied by CIVA, the sample could be analysed by a subsequent experiment (PTOLEMY and/or COSAC). The process would be repeated for each sample obtained at different depths and/or locations. Title: A Portrait of the Nucleus of Comet 67P/Churyumov-Gerasimenko Authors: Lamy, Philippe L.; Toth, Imre; Davidsson, Björn J. R.; Groussin, Olivier; Gutiérrez, Pedro; Jorda, Laurent; Kaasalainen, Mikko; Lowry, Stephen C. Bibcode: 2007SSRv..128...23L Altcode: 2007SSRv..tmp...74L In 2003, comet 67P/Churyumov-Gerasimenko was selected as the new target of the Rosetta mission as the most suitable alternative to the original target, comet 46P/Wirtanen, on the basis of orbital considerations even though very little was known about the physical properties of its nucleus. In a matter of a few years and based on highly focused observational campaigns as well as thorough theoretical investigations, a detailed portrait of this nucleus has been established that will serve as a baseline for planning the Rosetta operations and observations. In this review article, we present a novel method to determine the size and shape of a cometary nucleus: several visible light curves were inverted to produce a size-scale free three-dimensional shape, the size scaling being imposed by a thermal light curve. The procedure converges to two solutions which are only marginally different. The nucleus of comet 67P/Churyumov-Gerasimenko emerges as an irregular body with an effective radius (that of the sphere having the same volume) = 1.72 km and moderate axial ratios a/b = 1.26 and a/c = 1.5 to 1.6. The overall dimensions measured along the principal axis for the two solutions are 4.49-4.75 km, 3.54-3.77 km and 2.94-2.92 km. The nucleus is found to be in principal axis rotation with a period = 12.4-12.7 h. Merging all observational constraints allow us to specify two regions for the direction of the rotational axis of the nucleus: RA = 220°+50°−30° and Dec = −70° ± 10° (retrograde rotation) or RA = 40°+50°-30° and Dec = +70°± 10° (prograde), the better convergence of the various determinations presently favoring the first solution. The phase function, although constrained by only two data points, exhibits a strong opposition effect rather similar to that of comet 9P/Tempel 1. The definition of the disk-integrated albedo of an irregular body having a strong opposition effect raises problems, and the various alternatives led to a R-band geometric albedo in the range 0.045-0.060, consistent with our present knowledge of cometary nuclei. The active fraction is low, not exceeding ~ 7% at perihelion, and is probably limited to one or two active regions subjected to a strong seasonal effect, a picture coherent with the asymmetric behaviour of the coma. Our slightly downward revision of the size of the nucleus of comet 67P/Churyumov-Gerasimenko resulting from the present analysis (with the correlative increase of the albedo compared to the originally assumed value of 0.04), and our best estimate of the bulk density of 370 kg m−3, lead to a mass of ~ 8 × 1012 kg which should ease the landing of Philae and insure the overall success of the Rosetta mission. Title: Properties of the dust cloud caused by the Deep Impact experiment Authors: Jorda, L.; Lamy, P.; Faury, G.; Keller, H. U.; Hviid, S.; Küppers, M.; Koschny, D.; Lecacheux, J.; Gutiérrez, P.; Lara, L. M. Bibcode: 2007Icar..191S.412J Altcode: 2007Icar..191..412J We present an analysis of the observations of the Deep Impact event performed by the OSIRIS narrow angle camera aboard the Rosetta spacecraft over two weeks, in an effort to characterize the cometary dust grains ejected from the nucleus of Comet 9P/Tempel 1. We adopt a Monte Carlo approach to generate calibrated synthetic images, and a linear combination of them is fitted to the calibrated images so as to determine the physical parameters of the dust cloud. Our model considers spherical olivine particles with a density of 3780 kg m-3. It incorporates constraints on the direction of the cone of emission coming from additional images obtained at Pic du Midi observatory, and constraints on the dust terminal velocities coming from the physics of the impact. We find that the slope of the differential dust size distribution of grains with radii <20 μm (β>0.008) is 3.1±0.3, a value typical of cometary dust tails. This shows that there is no evidence in our data for an enhancement in sub-micron particles in the ejecta compared to the typical dust distribution of active comets. We estimate the mass of particles with radii <1.4 μm (β>0.14) to be 1.5±0.2×10 kg. These particles represent more than 80% of the cross-section of the observed dust cloud. The mass carried by larger particles depends whether the gas significantly increases the kinetic energy of the grains in the inner coma; it lies in the range 1 14×10 kg for particles with radii <100 μm (β>0.002). We obtain the distribution of terminal velocities reached by the dust after the dust gas interaction which is very well constrained between 10 and 600 m s-1. It is characterized by Gaussian with a maximum at about 190 m s-1 and a width at half maximum of 150 m s-1. Title: Determination of the light curve of the Rosetta target asteroid (2867) Steins by the OSIRIS cameras onboard Rosetta Authors: Küppers, M.; Mottola, S.; Lowry, S. C.; A'Hearn, M. F.; Barbieri, C.; Barucci, M. A.; Fornasier, S.; Groussin, O.; Gutiérrez, P.; Hviid, S. F.; Keller, H. U.; Lamy, P. Bibcode: 2007A&A...462L..13K Altcode: 2006astro.ph.12097K Context: In 2004 asteroid (2867) Steins has been selected as a flyby target for the Rosetta mission. Determination of its spin period and the orientation of its rotation axis are essential for optimization of the flyby planning.
Aims: Measurement of the rotation period and light curve of asteroid (2867) Steins at a phase angle larger than achievable from ground based observations, providing a high quality data set to contribute to the determination of the orientation of the spin axis and of the pole direction.
Methods: On March 11, 2006, asteroid (2867) Steins was observed continuously for 24 h with the scientific camera system OSIRIS onboard Rosetta. The phase angle was 41.7 degrees, larger than the maximum phase angle of 30 degrees when Steins is observed from Earth. A total of 238 images, covering four rotation periods without interruption, were acquired.
Results: The light curve of (2867) Steins is double peaked with an amplitude of ≈0.23 mag. The rotation period is 6.052~± 0.007 h. The continuous observations over four rotation periods exclude the possibility of period ambiguities. There is no indication of deviation from a principal axis rotation state. Assuming a slope parameter of G = 0.15, the absolute visual magnitude of Steins is 13.05 ± 0.03.

Table 2 is only available in electronic form at http://www.aanda.org Title: Hubble Space Telescope observations of the nucleus of Comet 9P/Tempel 1 Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A.; Weissman, P. R. Bibcode: 2007Icar..191S...4L Altcode: 2007Icar..191....4L The nucleus of Comet 9P/Tempel 1, the target of the Deep Impact mission, was detected during Hubble Space Telescope observations taken with the wide-field planetary camera 2 (WFPC2) on 31 December 1997 when the comet's solar phase angle was 3.°8, its heliocentric distance was 4.48 AU, and its geocentric distance was 3.53 AU. Sixteen images were taken through the F675W filter, and all of them revealed a point-like source without any detectable coma. From these images, we derived the R magnitude of the nucleus in the Johnson Kron Cousins photometric system for the entire 11.5-h time span of the observations. Assuming a prolate spheroid whose spin axis lies close to the plane of the sky, the partial lightcurve indicates semi-axes a-3.9 km and b-2.8 km (assuming a geometric albedo of 0.04 for the R band and a phase coefficient of 0.04 mag deg-1) and a rotational period in the range of ∼25-33 h. The upper limit of the parameter Afρ, which characterizes the dust production rate, is 1 cm. We also derive a fractional active area at 1.78 AU of ∼4%. Title: Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta Authors: Keller, Horst Uwe; Küppers, Michael; Fornasier, Sonia; Gutiérrez, Pedro J.; Hviid, Stubbe F.; Jorda, Laurent; Knollenberg, Jörg; Lowry, Stephen C.; Rengel, Miriam; Bertini, Ivano; Cremonese, Gabriele; Ip, Wing-H.; Koschny, Detlef; Kramm, Rainer; Kührt, Ekkehard; Lara, Luisa-Maria; Sierks, Holger; Thomas, Nicolas; Barbieri, Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; A'Hearn, Michael F.; Angrilli, Francesco; Barucci, Maria-Antonella; Bertaux, Jean-Loup; da Deppo, Vania; Davidsson, Björn J. R.; de Cecco, Mariolino; Debei, Stefano; Fulle, Marco; Gliem, Fritz; Groussin, Olivier; Lopez Moreno, José J.; Marzari, Francesco; Naletto, Giampiero; Sabau, Lola; Sanz Andrés, Angel; Wenzel, Klaus-Peter Bibcode: 2007Icar..191S.241K Altcode: 2007Icar..191..241K The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impact projectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showed regular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness of Tempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structures were created by the impact. Most of the material moved with ∼200ms. Much of it left the comet in the form of icy grains which sublimated and fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet (4.5 9×10kg of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions with gas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations of the density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain. Title: Rotational state of the nucleus of Comet 9P/Tempel 1: Results from Hubble Space Telescope observations in 2004 Authors: Lamy, Philippe L.; Toth, Imre; A'Hearn, Michael F.; Weaver, Harold A.; Jorda, Laurent Bibcode: 2007Icar..191S.310L Altcode: 2007Icar..191..310L The nucleus of Comet 9P/Tempel 1 was first observed with the Hubble Space Telescope (HST) in December 1997 [Lamy, P., Toth, I., A'Hearn, M.F., Weaver, H., Weissman, P.R., 2001. Icarus 154, 337 344], but the temporal coverage was insufficient to determine its rotational period. Because the success of the Deep Impact mission was critically dependent on understanding the rotational state and approximate shape and size of the nucleus, we extensively re-observed 9P/Tempel 1, this time with the Advanced Camera for Surveys (HST/ACS), from May 7.9 to 9.5, 2004 (UT). At the mid-point of the observing window, the comet was 3.52 AU from the Sun, 4.03 AU from the Earth, and at a solar phase angle of 13.3°. The program was comprised of 18 separate visits, each one corresponding to an HST orbit filled with 3 ACS exposures of either 800 or 857 s duration with the F606W broadband filter. These very deep exposures revealed a star-like object, without any apparent coma. The light curve, defined by 49 data points, is characterized by a mean apparent V magnitude of 21.8 and an amplitude of 0.5 mag, indicating that we were viewing the varying cross-section of a rotating, elongated body. The periodicity was analyzed with seven different techniques yielding a rotational period in the range 39.40 to 43.00 h, and a mean value of 41.27±1.85 h (1σ). Using an albedo p=0.04 and a linear phase law with a coefficient β=0.0465 magdeg, we determined an effective radius of 3.01 km; a possible prolate spheroid solution has semi-axes a=3.71 km, b=2.36 km and a minimum axial ratio a/b∼1.57. By comparing the light curves obtained in 1997 and in 2004, we were able to constrain the phase function of the nucleus. Finally, an upper limit of Afρ<0.04 cm is set based on the non-detection of the coma. Title: Hubble Space Telescope observations of the nucleus and inner coma of comet 67P/Churyumov-Gerasimenko Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Jorda, L.; Kaasalainen, M.; Gutiérrez, P. J. Bibcode: 2006A&A...458..669L Altcode: Context: .Following the postponement of the launch of the Rosetta spacecraft scheduled in January 2003, comet 67P/Churyumov-Gerasimenko emerged as the most suitable new target. However a critical issue was the size, that is, the mass of its nucleus, as the surface module Philae was designed to land on a nucleus with a radius no larger than approximately 1.5 km.
Aims: . It was therefore crucial to the success of the mission to achieve a timely characterization of the nucleus of 67P/C-G so as to take any proper action on the design needed before the new launch.
Methods: . We used the Wide Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope (HST) whose superior spatial resolution enabled us to accurately separate the signal of the nucleus from that of the coma. The observations were performed on 12 and 13 March 2003, when the comet was 2.50 AU from the Sun, 1.52 AU from the Earth, and at a phase angle of 4.8°.
Results: . The nucleus of comet 67P/Churyumov-Gerasimenko was easily detected, and we measured its V and R magnitudes in the Johnson-Kron-Cousins photometric system. Assuming that the nucleus is spherical, with a geometric albedo of 0.04 and a phase coefficient of 0.04 mag/deg for the R band, we derived a radius of 1.98±0.02 km. The spheroidal solution has semiaxes a = 2.41 km and b = c = 1.55 km and a rotational period of 12.41±0.41 h. We inverted the light curve and solved it for a full three-dimensional nucleus having an overall size of 4.56×3.81×3.44 km viewed at an aspect angle of ∼80° (i.e., near equatorial view) at the time of our observations. When combined with other constraints, the direction of the pole is found at either RA = 40°+70°-20° and Dec = +70±10° (prograde rotation) or RA = 250±30° and Dec = -70±10° (retrograde rotation). The color of the nucleus is moderately red with (V-R)=0.52±0.05. From an analysis of the dust coma, we derived Afρ = 40.2±0.3 cm, a dust production rate Qd ∼ 4 kg s-1, and we characterized its color.
Title: Determination Of The Light Curve Of Rosetta Target Asteroid 2867 Steins With The Osiris Narrow Angle Camera Onboard Rosetta Authors: Kueppers, Michael; Keller, H. U.; Hviid, S. F.; Mottola, S.; Fornasier, S.; Barbieri, C.; Barucci, A.; Gutiérrez, P.; Lamy, P.; OSIRIS Team Bibcode: 2006DPS....38.5920K Altcode: 2006BAAS...38..596K On its way to comet 67P/Churyumov-Gerasimenko, the European Space Agency's Rosetta spacecraft is going to fly by Asteroids 2867 Steins in Sept. 2008 and 21 Lutetia in July 2010. While 21 Lutetia is a large main belt asteroid with a long history of investigation, relatively little is known about 2867 Steins. In particular, knowledge of the rotation period and the orientation of the rotation axis are valuable for the flyby preparations.

OSIRIS is the scientific camera system onboard Rosetta, consisting of a narrow angle camera (NAC) and a wide angle camera (WAC). In March 2006, the NAC observed 2867 Steins continuously for 24 hours, acquiring 238 images, with a clear filter. The camera performed flawlessly. The data obtained from spacecraft are unique in terms of continuous temporal coverage and phase angle. Indeed, the NAC observations were taken at a phase angle of 42 deg., compared to a maximum phase angle of 30 deg. when seen from Earth. The distance between Rosetta and 2867 Steins was 1.06 AU.

The OSIRIS data show a double peaked light curve with an amplitude of 0.23 magnitudes and a synodic rotation period of 6.052 ± 0.035 hours, in good agreement with ground based data by Hicks et al. (2004, IAU Circular 8315) and Weissman et al. (2006, ACM Conference). The continuous observations over four rotations completely exclude the possibility of period ambiguities. There is no indication of deviation from a principal axis rotation state. The observations are being combined with Earth-based data sets to derive the orientation of the spin axis and pole position for 2867 Steins.

We acknowledge funding from the national space agencies ASI, CNES, DLR, the Spanish Space Program (Ministerio de Educación y Ciencia), SNSB, and ESA. Title: Visible and Infrared Observations of Asteroid 2867 Steins, a target of the Rosetta Mission Authors: Lamy, Philippe L.; Jorda, L.; Fornasier, S.; Kaasalainen, M.; Lowry, S.; Barucci, A.; Faury, G.; Kuppers, M.; Toth, I.; Weissman, P. Bibcode: 2006DPS....38.5909L Altcode: 2006BAAS...38..594L We present the results of a coordinated campaign of visible and infrared observations aimed at fostering our knowledge of asteroid 2867 Steins in preparation of its flyby by the Rosetta spacecraft in Sept. 2008, on its way to comet 67P/Churyumov-Gerasimenko. Our data set includes 16 visible light curves and 14 infrared spectra. Fifteen light curves were obtained with various ground-based observatories and an additional one, with the narrow angle camera (NAC) of the OSIRIS scientific camera aboard Rosetta that continuously monitored 2867 Steins over 24 hr in March 2006. Simultaneous inversion of the 16 light curves allows to generate a three-dimensional shape model of 2867 Steins with axial ratios a/b = 1.2 and b/c = 1.6, to determine its rotational period (6.0481 ± 0.0004 hr) and two possible solutions for the direction of its rotational axis. The infrared spectra were obtained with the low resolution mode of the Spitzer space telescope IRS; they extend from 5 to 35 microns and sample the rotational light curve with a temporal resolution of 30 min. Preliminary analysis using a standard thermal model yield an equivalent diameter of approximately 5 km and an albedo in the range 0.30 - 0.40. This classifies 2867 Steins as an E-type asteroid, a class of differentiated bodies which experienced significant heating episodes. The large beaming factor probably implies a thermal inertia in the range 150 - 300 SI but this will be further explored using more elaborated thermal models. Title: HST Observations of the Nucleus Fragment 73P/Schwassmann-Wachmann 3-C During its Close Approach to Earth in 2006 Authors: Toth, I.; Lamy, P.; Weaver, H.; A'Hearn, M.; Kaasalainen, M.; Lowry, S. Bibcode: 2006DPS....38.0601T Altcode: 2006BAAS...38..489T Fragment C of 73P/Schwassmann-Wachmann 3 (73P) was first detected with the HST-WFPC2 on 26 November 2001 when its heliocentric and geocentric distances were 3.26 AU and 2.34 AU, respectively. At that time, we found a very active nucleus with an effective radius of 0.68±0.04 km (Toth et al., 2005: Icarus 178, 235-247). The comet's favorable apparition in April-May 2006 offered an exceptional opportunity to re-observe this nucleus at close range. Our observations took place on 10 April when the comet was 1.24 AU from the Sun, 0.29 AU from the Earth, and at a phase angle of 31°. They were performed with the HRC mode of the ACS with three standard filters, F475W ("B"), F555W ("V") and F625W ("R"), as well as with the broadband F606W (broad "V") to search for possible orbiting fragments. Fragment C was highly active, and the nucleus and the coma contributed almost equally in the central pixels. Assuming a spherical body with a geometric albedo of 0.04 and a linear phase coefficient of 0.04 mag/deg for the R-band, we derived an effective radius of 0.41±0.02 km. The light curve suggest that we were seeing the varying cross-section of an elongated body and we determined a = 0.57±0.08 km, b = c = 0.31 ±0.02 km, the minimum axial ratio 1.8±0.3, and a rotational period of 3.7±0.2 hr. Its color is characterized by (V-R) = 0.57±0.11 and (B-V) = 1.16±0.20, slightly outside the main trend among cometary nuclei, but comparable to a few of them. We were unable to detect any fragment in the vicinity of the C fragment on our deep HST images. H.A.W. acknowledges support by NASA through grant GO-10625 from the STScI, S.C.L. acknowledges support from the UK Particle Physics and Astronomy Research Council, and I.T. acknowledges support from CNRS, France. Title: Hubble Space Telescope Investigation of the Disintegration of 73P/Schwassmann-Wachmann 3 Authors: Weaver, Harold A.; Lisse, C. M.; Mutchler, M. J.; Lamy, P.; Toth, I.; Reach, W. T. Bibcode: 2006DPS....38.0602W Altcode: 2006BAAS...38..490W Following reports of dramatic temporal variability of the B and G fragments of 73P/Schwassmann-Wachmann 3 (73P/SW3) in early April 2006, our team was awarded Director's Discretionary time on the Hubble Space Telescope to investigate the continuing disintegration of the nuclei. We observed the B fragment three different times (UT 2006 April 18.974, 19.773, and 20.773) and discovered a swarm of sub-fragments trailing behind the principal nucleus, including some that were probably released coincident with the brightness outbursts reported by ground-based observers during the first few days of April. The single observation of the G fragment (UT 2006 April 18.574) also showed a nearby swarm of sub-fragments, including some that were probably released just a few days prior to the Hubble observations. For both the B and G fragments, the Hubble images provide information on the fragmentation history of both nuclei during the preceding month, if not earlier. In contrast, a single Hubble observation of the C fragment during this same period (UT 2006 April 18.642) did not reveal any new sub-fragments, consistent with the rather steady activity observed for the C fragment throughout early-April by both ground-based facilities and another Hubble program (Lamy et al.). We examine in detail the morphology and kinematics of the continuing disintegration of the B and G fragments and compare the Hubble results to those obtained from earlier and later observations with the Spitzer Space Telescope to develop a more comprehensive understanding of the nucleus disruption process.

Financial support for this work was provided by NASA through grant GO-10992 from the STScI. Title: Aphelion Observations of the Nucleus of Comet 67P/Churyumov-Gerasimenko: Target of ESA's Rosetta Comet Orbiter Mission Authors: Lowry, Stephen C.; Fitzsimmons, A.; Jorda, L.; Kaasalainen, M.; Lamy, P.; Toth, I. Bibcode: 2006DPS....38.0801L Altcode: 2006BAAS...38..492L Rosetta is ESA's new comet orbiter mission, launched in March 2004 and currently en route to Jupiter-family comet 67P/Churyumov-Gerasimenko. The probe will rendezvous with the comet in 2014 and remain in orbit around the nucleus for on-going detailed physical and compositional analysis. Pre-encounter observations of the target are important for characterization of the heliocentric light-curve behaviour and the physical properties of the nucleus, information that is critical for mission planning. We present our latest results from detailed observations carried out when the comet was near aphelion at a heliocentric distance of 5.6 AU. The comet was also at opposition, with an average phase angle of just 0.46°. Three nights of optical imaging data were taken with ESO's 3.5m NTT at La Silla (Chile), between May 10-14, 2005. The data includes CCD VRI-filter imaging taken with the EMMI instrument. The rotational signature of the nucleus was clearly detected at all passbands with no sign of resolved coma or dust trail. Full rotational light-curves in all three passbands were obtained, allowing detailed inspection of surface colours at all rotational phases. A Fourier analysis of the R-filter light-curve gives a robust best-fit synodic rotation period of 12.72 ± 0.05 hours. The observed brightness range of 0.38 ± 0.04 magnitudes implies a projected nucleus axial ratio of 1.42 ± 0.05. The mean R-filter magnitude is 22.41 ± 0.03, which corresponds to mean nucleus effective radius of 2.26 ± 0.03 km (assuming an albedo and linear phase coefficient of 0.04). The projected semi-axial dimensions are therefore 2.94 ± 0.15 and 2.07 ± 0.04 km. Our size is slightly larger than a previous estimate [Lamy et al. 2003. BAAS 35, 970], which implies a steep phase-darkening law or a more complex phase function that includes an opposition-surge effect. Title: Understanding the Kreutz Sungrazing Comets Authors: Knight, Matthew M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.; Hamilton, D. P.; Lamy, P.; Llebaria, A. Bibcode: 2006DPS....38.2002K Altcode: 2006BAAS...38..516K We present updated results of our photometric study of the Kreutz family comets observed by SOHO-LASCO. This is a continuation of earlier work by Biesecker et al. (2002) and includes all Kreutz comets which reached perihelion in the SOHO-LASCO field of view by the end of 2005, a sample of over 900 comets. Typical Kreutz light curves brighten at a relatively constant rate, reach a peak in brightness at 10-13 solar radii (prior to perihelion), then fade rapidly, with a small subset displaying a second (smaller) peak in brightness inside of 6 solar radii. We are attempting to explain these light curve features using physical models of the nucleus such as composition, density, porosity, and production rates and will report on our findings. We are also investigating the relationship between Kreutz comets and other comets observed by SOHO-LASCO (the sungrazing families: Meyer, Marsden, and Kracht, and other non-sungrazing comets) and with observations of prominent sungrazers seen from the ground, e.g. Ikeya-Seki (1965 f), to estimate production rates at larger heliocentric distances. From these rates we hope to improve the scaling relationship between size and apparent brightness and constrain the size distribution of the Kreutz family.

This research was supported by NASA Planetary Atmospheres grant NAG513295. Title: In situ dust measurements in the inner Saturnian system Authors: Srama, R.; Kempf, S.; Moragas-Klostermeyer, G.; Helfert, S.; Ahrens, T. J.; Altobelli, N.; Auer, S.; Beckmann, U.; Bradley, J. G.; Burton, M.; Dikarev, V. V.; Economou, T.; Fechtig, H.; Green, S. F.; Grande, M.; Havnes, O.; Hillier, J. K.; Horanyi, M.; Igenbergs, E.; Jessberger, E. K.; Johnson, T. V.; Krüger, H.; Matt, G.; McBride, N.; Mocker, A.; Lamy, P.; Linkert, D.; Linkert, G.; Lura, F.; McDonnell, J. A. M.; Möhlmann, D.; Morfill, G. E.; Postberg, F.; Roy, M.; Schwehm, G. H.; Spahn, F.; Svestka, J.; Tschernjawski, V.; Tuzzolino, A. J.; Wäsch, R.; Grün, E. Bibcode: 2006P&SS...54..967S Altcode: In July 2004 the Cassini-Huygens mission reached the Saturnian system and started its orbital tour. A total of 75 orbits will be carried out during the primary mission until August 2008. In these four years Cassini crosses the ring plane 150 times and spends approx. 400 h within Titan's orbit. The Cosmic Dust Analyser (CDA) onboard Cassini characterises the dust environment with its extended E ring and embedded moons. Here, we focus on the CDA results of the first year and we present the Dust Analyser (DA) data within Titan's orbit. This paper does investigate High Rate Detector data and dust composition measurements. The authors focus on the analysis of impact rates, which were strongly variable primarily due to changes of the spacecraft pointing. An overview is given about the ring plane crossings and the DA counter measurements. The DA dust impact rates are compared with the DA boresight configuration around all ring plane crossings between June 2004 and July 2005. Dust impacts were registered at altitudes as high as 100 000 km above the ring plane at distances from Saturn between 4 and 10 Saturn radii. In those regions the dust density of particles bigger than 0.5μm can reach values of 0.001m-3. Title: On the mechanisms leading to orphan meteoroid streams Authors: Vaubaillon, J.; Lamy, P.; Jorda, L. Bibcode: 2006MNRAS.370.1841V Altcode: 2006MNRAS.tmp..735V We analyse several mechanisms capable of creating orphan meteoroid streams (OMSs) for which a parent has not been identified. OMSs have been observed as meteor showers since the XIXth century and by the IRAS satellite in the 1980s. We find that the process of close encounters with giant planets (particularly Jupiter) is the most efficient mechanism to create them: only a limited section of the stream is perturbed and follows the parent body on its new orbit, while the majority of the meteoroids remain in their pre-encounter orbit or in an intermediate state, breaking the link with their parent body. Cometary non-gravitational forces can also contribute to the process since they cause the comet to drift away from its stream. However, they are not sufficient by themselves to produce an OMS. Resonances can either split or confine a stream over a long time (>1000 yr). Some meteoroid streams may look like OMSs since their parent comet is dormant or not observable (e.g. long period). Even if new techniques succeed in linking minor objects to meteoroid streams, OMSs will still exist simply because cometary nuclei are subject to complete disruption leading to their disappearance. Title: Analysis of Space Coronagraphic Images : Application to ten years of SOHO/LASCO data Authors: Burtin, M.; Llebaria, A.; Lamy, P. Bibcode: 2006ASPC..351..275B Altcode: 2006adass..15..275B Since 1996, the LASCO (Large Angle and Spectrometric Coronagraph) Coronagraphs of the ESA/NASA SOHO (Solar and Heliospheric Observatory) mission have been providing the solar astronomical and geophysical communities with an unprecedented view of the solar corona. The photometric restitution of the huge amount of data is of prime importance for understanding the physics of the corona, its evolution over a solar cycle as well as its consequences on the Earth environment, and represents a major challenge. The combination of ground calibrations, continuous in-flight calibrations and the implementation of novel procedures has been necessary to disentangle the strong intercorrelation between many instrumental effects such as vignetting, polarization, straylight, optical distortion and timing. Geometricals parameters are extracted in a first pass. The vignetting correction relies on a detailed model of the instrument supplemented by a comparison with ground-based observations of the inner corona during the 1998 total eclipse. The polarimetric response based on the Mueller method was finely corrected thanks to polarized images obtained during specific maneuvers of the SOHO spacecraft. The straylight has been deduced on a yearly basis using the unpolarized component extracted from polarization sequences. The photometric calibration and its temporal evolution relies on several hundreds stars observed over ten years of operation. We will describe the overall software and database architectures of these calibration-pipeline chains, and the final products made available on our LASCO website. Title: Magnetic Variability of the Streamer Belt Authors: Saez, F.; Lamy, P.; Llebaria, A. Bibcode: 2006ESASP.617E..74S Altcode: 2006soho...17E..74S No abstract at ADS Title: Interaction of CMEs with the Streamer Belt Authors: Llebaria, A.; Saez, F; Lamy, P.; Robelus, S.; Boursier, Y. Bibcode: 2006ESASP.617E.135L Altcode: 2006soho...17E.135L No abstract at ADS Title: The Marseille-Artemis Catalog of LASCO CMES Authors: Boursier, Y.; Lamy, P.; Llebaria, A.; Robelus, S. Bibcode: 2006ESASP.617E.119B Altcode: 2006soho...17E.119B No abstract at ADS Title: Formation flying applied to solar coronal diagnostics: the ASPIICS coronagraph Authors: Vivès, S.; Lamy, P.; Levacher, P.; Boit, J. L.; Saisse, M. Bibcode: 2006SPIE.6265E..24V Altcode: 2006SPIE.6265E..64V Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent observing the inner corona inside typically 2-2.5 solar radii. Formation flyers open new perspectives and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at approximately 100-150 m from the first one. ASPIICS (Association de Satellites Pour l'Imagerie et l'Interfromtrie de la Couronne Solaire) is a payload proposed to ESA in the framework of the PROBA-3 mission of formation flyers presently under study. ASPIICS is composed of a single coronagraph which performs high spatial resolution imaging of the corona as well as 2-dimensional spectroscopy of several emission lines (in particular the forbidden line of Fe XIV at 530.285 nm) from the coronal base out to 3 solar radii ( R solar). Thus ASPIICS will address the main questions of the coronal physics. The classical design of an externally occulted coronagraph is adapted to the detection of the very inner corona as close as 1.01 R solar and the addition of a Fabry-Perot interferometer using a so-called etalon. Title: Survey of Ensemble Physical Properties of Cometary Nuclei Authors: Fernandez, Yanga; A'Hearn, Michael; Bauer, James; Campins, Humberto; Groussin, Olivier; Lamy, Philippe; Licandro, Javier; Lisse, Carey; Lowry, Stephen; Meech, Karen; Reach, William; Toth, Imre; Weaver, Harold Bibcode: 2006sptz.prop30908F Altcode: We propose to make an albedo and radius survey of 100 cometary nuclei using IRS PU and MIPS imaging. We focus on Jupiter family comets (JFCs), which have dynamical and evolutionary connections to other Solar System groups: transneptunian objects (TNOs), Centaurs, Trojan asteroids, and extinct comet candidates. However, among these groups, the nuclei of JFCs remain the _only_ group not yet the subject of a detailed mid-infrared survey. Understanding the evolution of comets since formation is crucial for unlocking their secrets about the thermophysical and compositional environment of the protoplanetary disk. An important way to do this is to study comparisons and contrasts among comets, and between comets and related dynamical groups. To this end, we propose a mid-IR survey of JFCs. Our scientific goals are as follows. 1) Measure the thermal emission from the JFC nuclei to calculate their effective radii. 2) Use complementary ground-based visible-wavelength observations to derive the nuclei's geometric albedos. Note that simultaneity for these observations is not needed. 3) Compare the cometary albedo distribution with those of Centaurs, TNOs, Trojans, and extinct comet candidates to gauge the effects of surface evolution. The glaring albedo difference between TNOs and Centaurs versus other groups needs to be explained. 4) Test for correlations between cometary albedos and other properties of the nuclei, such as composition and dynamical age. 5) Resolve once and for all the long-standing question of just how safe it is to assume an albedo for a cometary nucleus. 6) Use these radii to derive a completely new and independent estimate of the current JFC size distribution that will resolve the ongoing debate between several groups. The number of targets in our sample is driven by the need to test recent indications that the size distribution is truncated at radii smaller than 2 km. In such a case, ours would be the definitive study of the JFC size distribution. Title: Photometric calibration of the LASCO-C2 coronagraph for Solar System objects Authors: Llebaria, A.; Lamy, P.; Danjard, J. -F. Bibcode: 2006Icar..182..281L Altcode: We present a photometric calibration of the SOHO/LASCO-C2 coronagraph appropriate to Solar System objects based on the extensive analysis of all stars down to magnitude V=8 which transited its field-of-view during the past nine years of operation (1996-2004). An automatic procedure was developed to analyze some 143,000 images, and to detect, locate and measure those stars. Aperture photometry was performed using three different aperture sizes and the zero points of the photometric transformations between the LASCO-C2 magnitudes for its three filters (orange, blue and red) and the standard V magnitudes were determined after introducing a correction for the color of the stars. The calibration coefficients for the surface photometry of extended sources were then derived from the zero points. An analysis of their temporal evolution indicates a slight decrease of the sensitivity of LASCO-C2 at a rate of ∼0.7% per year. Title: Calibration of the Soho/Lasco C3 White Light Coronagraph Authors: Morrill, J. S.; Korendyke, C. M.; Brueckner, G. E.; Giovane, F.; Howard, R. A.; Koomen, M.; Moses, D.; Plunkett, S. P.; Vourlidas, A.; Esfandiari, E.; Rich, N.; Wang, D.; Thernisien, A. F.; Lamy, P.; Llebaria, A.; Biesecker, D.; Michels, D.; Gong, Q.; Andrews, M. Bibcode: 2006SoPh..233..331M Altcode: We present a detailed review of the calibration of the LASCO C3 coronagraph on the SOHO satellite. Most of the calibration has been in place since early in the mission and has been utilized to varying degrees as required by specific analysis efforts. However, using observational data from the nearly decade-long database of LASCO images, we have re-evaluated and improved many aspects of the calibration. This includes the photometric calibration, vignetting function, geometric distortion, stray light, and exposure and observation times. Using this comprehensive set of corrections we have generated and made available a set of calibrated coronal images along with a set of periodic background images to ease the accessibility and use of the LASCO database. Title: 3D Simulations of the Solar Corona using Octree Compression Authors: Saez, F.; Lamy, P.; Llebaria, A. Bibcode: 2006IAUS..233..236S Altcode: We present a new powerful tool to simulate the streamer belt of the solar corona based on forward modeling. It takes into account the temporal evolution of the corona and provides both qualitative and quantitative results. Starting from the National Solar Observatory photospheric magnetograms, the position of the neutral line at the source surface (2.5 Rsun) is caculated using the potential field source surface model. The plasma sheet of the streamer belt is centered around the current sheet represented as the radial extension of the neutral line. The 3D electron density is represented with octree compression and the radiance images are computed by a ray-tracing algorithm implementing the Thomson scattering. A multi-octree method allows to simulate the temporal evolution of the streamer belt and to compute the synoptic maps from time-series of generated images. The comparison between the synoptic maps of the streamer belt obtained with the SOHO/LASCO-C2 coronagraph and the simulated synoptic maps constructed from our model shows a global agreement for both radiance profiles and global behaviour of the streamer and confirms earlier findings by Wang et al. (1997) that the streamers are associated with folds in the plasma sheet. However, some features cannot be explained using this method and are interpreted by introducing two types of large-scale structures. Our results suggest that the potential field source surface model is not fully adequate for the description of the fine structure of the streamer belt, even during the time of low solar activity. We present new applications of our method to future coronographic observations with SECCHI/COR-2 on STEREO and SILC on Solar Orbiter. Title: ASPIICS, a giant externally occulted coronagraph for the PROBA-3 formation flyer mission Authors: Vivès, S.; Lamy, P.; Koutchmy, S.; Arnaud, J. Bibcode: 2006cosp...36.3063V Altcode: 2006cosp.meet.3063V Formation flyers open new perspectives and allow to conceive giant externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at approximately 100 m from the first one ASPIICS Association de Satellites Pour l Imagerie et l Interferometrie de la Couronne Solaire is a mission proposed to ESA in the framework of the PROBA-3 program of formation flyers which is presently in phase A to exploit this technique for coronal observations ASPIICS is composed of a single coronagraph which performs high spatial resolution imaging of the corona as well as 2-dimensional spectroscopy of several emission lines from the coronal base out to 3 Rs The selected lines allow to address different coronal regions the forbidden line of FeXIV at 530 285 nm coronal matter Fe IX X at 637 4 nm coronal holes HeI at 587 6 cold matter An additional broad spectral channel will image the white light corona and derive electron densities The classical design of an externally occulted coronagraph is adapted to the detection of the very inner corona as close as 1 01 Rs and the addition of a Fabry-Perot interferometer using a so-called etalon ASPIICS will address the question of the coronal heating and the role of waves by characterizing propagating fluctuations waves and turbulence in the solar wind acceleration region and by looking for oscillations in the intensity and Doppler shift of spectral lines The combined imaging and spectral diagnostics capabilities available with ASPIICS Title: A portrait of the nucleus of comet 67P/Churyumov-Gerasimenko, the target of the Rosetta mission Authors: Lamy, P.; Toth, I.; Jorda, L.; Lowry, S.; Gutierrez, P.; Groussin, O.; Kaasalainen, M. Bibcode: 2006cosp...36.3366L Altcode: 2006cosp.meet.3366L We present a detailed portrait of the nucleus of comet 67P Churyumov-Gerasimenko based on observations performed with the Hubble Space Telescope with the Spitzer Space Telescope and with the ESO New Technology Telescope in Chili In all cases the observations extended over several hours so that light curves could be secured Results will encompass the size shape albedo and rotational state of the nucleus of 67P as well as a 3D solution reconstruction of its shape resulting from the inversion of the light curves Title: Properties of the DEEP IMPACT Dust Cloud Authors: Jorda, L.; Lamy, P.; Faury, G.; Keller, H. -U.; Kueppers, M.; Hviid, S.; Koschny, D.; Lecacheux, J.; Gutierrez, P.; Lara, L. Bibcode: 2006cosp...36.3223J Altcode: 2006cosp.meet.3223J The OSIRIS Narrow Angle Camera aboard ROSETTA observed in the visible the dust cloud created by the DEEP IMPACT impactor during more than 2 weeks Additional observations were also obtained at Pic du Midi Observatory in the visible before and after the impact We compare the acquired images with synthetic images resulting from a Monte-Carlo simulation to compute the mass and the kinetic energy of the dust in the cloud We also derive the size mass and velocity distributions of the dust particles Our study is however restricted to submicron particles which can be easily detected on our images Title: Electron density in polar and trans-equatorial coronal holes. Implications for the solar wind Authors: Lamy, P.; Saez, F.; Llebaria, A. Bibcode: 2006cosp...36.3338L Altcode: 2006cosp.meet.3338L We present the final analysis of the polarized images of the solar corona obtained with the LASCO-C2 coronagraph aboard SOHO over the last 10 years The calibrated polarized radiance pB has been inverted to produce 2-D maps of the electron density assuming either spherical or cylindrical symmetry We concentrate here on polar and trans-equatorial coronal holes We compare the measured profiles with those from models and past observations We attempt to determine the lowest possible density profile in a hole We finally discuss the implications of our measurements for the properties of the solar wind Title: The Coronal Dynamics Imagers for the KUAFU mission Authors: Vivès, S.; Lamy, P.; Rousset, G.; Boit, J. -L. Bibcode: 2006cosp...36.3054V Altcode: 2006cosp.meet.3054V The Space Weather Explorer - KuaFu mission will provide simultaneous long-term and synoptic observations of the complete chain of disturbances from the solar atmosphere to the geospace KuaFu-A located at the L1 liberation point includes Coronal Dynamics Imagers composed of a Lyman-alpha coronagraph from 1 1 to 2 5 solar radii and a white light coronagraph out to 15 solar radii in order to identify the initial sources of Coronal Mass Ejections CMEs and their acceleration profiles The difficulty of observing the lower corona should not be underestimated since instrumental stray light remains a critical issue in the visible because of the low contrast of the corona with respect to the Sun Observing the corona in the Lyman-alpha line is a valid alternative to white light observations The Lyman-alpha approach takes advantage of both the intrinsic higher contrast of the corona wrt the solar disk in this line compared to the visible and the absence of F-corona at 121 6nm Furthermore it has been convincingly shown that the coronal structures seen in Lyman-alpha correspond to those seen in the visible and which result from Thomson scattering of the coronal ionized gas This is because the plasma is still collisional in the lower corona so that the hydrogen neutral atoms are coupled to the protons A classical internally-occulted Lyot coronagraph is required so as to preserve the image quality down to the inner limit of the field of view Following the general concept of a Lyot coronagraph the optical design uses only mirrors A narrow band interferential filter Title: Visible and infrared observations of Asteroid Steins, a target of the Rosetta mission Authors: Lamy, P.; Barucci, A.; Jorda, L.; Lowry, S.; Carvano, J.; Fornasier, S.; Groussin, O.; Kaasalainen, M. Bibcode: 2006cosp...36.3351L Altcode: 2006cosp.meet.3351L In 2008 the ROSETTA spacecraft will flyby asteroid 2867 Steins a small main belt asteroid whose present knowledge is still very limited In particular its albedo is unknown since it has never been observed in the infrared Its rotational period of 6 06 -0 05 hours and light curve amplitude of 0 2 mag have been recently determined but the orientation of its spin axis is unknown In order to improve our knowledge of this asteroid and prepare the flyby we have conducted a campaign of visible measurements using ground-based telescopes and infrared measurements using the SST Spitzer space telescope In all cases Steins has been observed over several hours to secure rotational light curves in order to rephase them for proper interpretation We will present our results for the size shape albedo and rotational state of this asteroid as well as a 3D solution reconstruction of its shape resulting from the inversion of the light curves Title: Understanding the Kreutz sungrazing comets Authors: Knight, M. M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.; Hamilton, D. P.; Lamy, P.; Llebaria, A. Bibcode: 2006cosp...36.2697K Altcode: 2006cosp.meet.2697K We present the results of our study of the Kreutz family comets observed by SOHO-LASCO This is a continuation of earlier work by Biesecker et al 2002 and includes all Kreutz comets which reached perihelion in the SOHO-LASCO field of view by the end of 2005 a sample of over 900 comets We use physical models of the nucleus such as composition density porosity and production rates to explain the characteristic features of Kreutz light curves notably the slope of brightening the peak in brightness at 10-13 solar radii prior to perihelion and the rapid fading interior to this The possibility that there exists two distinct subgroups of Kreutz comets which reach peak brightness at slightly different heliocentric distances is reexamined and modeled We compare the Kreutz comets with other comets observed by SOHO-LASCO the sungrazing families Meyer Marsden and Kracht and other non-sungrazing comets and with observations of prominent sungrazers seen from the ground e g C 1965 S1 Ikeya-Seki to estimate production rates at larger heliocentric distances From these rates we improve the scaling relationship between size and apparent brightness and constrain the size distribution of the Kreutz family Finally we predict discovery rates of Kreutz comets by the upcoming STEREO mission and ground-based surveys such as Pan-STARRS This research was supported by NASA Planetary Atmospheres grant NAG513295 Title: 3-D simulations of the solar Corona for the STEREO and SOLAR ORBITER missions Authors: Saez, F.; Lamy, P.; Llebaria, A. Bibcode: 2006cosp...36.3344S Altcode: 2006cosp.meet.3344S We present a new powerful tool based on a forward modeling method which allows to simulate the streamer belt taking into account the temporal evolution of the solar corona and which provides both qualitative and quantitative results Starting from the NSO photospheric magnetograms the position of the neutral line at the source surface 2 5 Rsun is caculated using the potential field source surface model The plasma sheet of the streamer belt is centered around the current sheet represented as the radial extension of the neutral line The 3-D electron density is represented with octree compression and the radiance images are computed by a ray-tracing algorithm implementing the Thomson scattering A multi-octree method permits to simulate the temporal evolution of the streamer belt This method has now been generalized to hanble the plumes and the coronal mass ejections and is well adapted to multi-views of the corona such as will be offered by the STEREO mission and to out-of-ecliptic views that SOLAR ORBITER will achieve We will present synthetic images as expected from the coronagraphs of these missions Title: The Lyman Alpha Imaging-Monitor Experiment (LAIME) for TESIS/CORONAS-PHOTON Authors: Damé, L.; Koutchmy, S.; Kuzin, S.; Lamy, P.; Malherbe, J. -M.; Noëns, J. -C. Bibcode: 2006cosp...36.3524D Altcode: 2006cosp.meet.3524D LAIME the Lyman Alpha Imaging-Monitor Experiment is a remarkably simple no mechanisms and compact 100x100x400 mm full Sun imager to be flown with TESIS on the CORONAS-PHOTON mission launch expected before mid-2008 As such it will be the only true chromospheric imager to be flown in the next years supporting TESIS EUV-XUV imaging SDO and the Belgian LYRA Lyman Alpha flux monitor on the ESA PROBA-2 microsatellite launch expected in September 2007 We will give a short description of this unique O60 mm aperture imaging telescope dedicated to the investigating of the magnetic sources of solar variability in the UV and chromospheric and coronal disruptive events rapid waves Moreton waves disparitions brusques of prominences filaments eruptions and CMEs onset The resolution pixel is 2 7 arcsec the field of view 1 4 solar radius and the acquisition cadence could be as high as 1 image minute The back thinned E2V CCD in the focal plane is using frame transfer to avoid shutter and mechanisms Further more the double Lyman Alpha filtering allows a 40 AA FWHM bandwidth and excellent rejection yet providing a vacuum seal design of the telescope MgF2 entrance window Structural stability of the telescope focal length 1 m is preserved by a 4-INVAR bars design with Aluminium compensation in a large pm 10 o around 20 o Title: Combined Visible Observations Of Comet 9P/Tempel 1 During The Deep Impact Event From Pic du Midi Observatory And With The ROSETTA/OSIRIS Narrow Angle Camera Authors: Jorda, L.; Lamy, P. L.; Faury, G.; Gutierrez, P.; Keller, H. -U.; Kueppers, M.; Lecacheux, J.; Colas, F.; Hviid, S.; Lara, L. M.; OSIRIS Team Bibcode: 2005DPS....37.4414J Altcode: 2005BAAS...37.1568J We observed comet 9P/Tempel 1 before and after the impact in the visible from the Earth with the 1-m telescope at Pic du Midi Observatory and with the narrow angle camera (OSIRIS/NAC) aboard the ROSETTA spacecraft. The latter observations allowed an uninterrupted monitoring from 120 hrs pre-impact to 250 hrs post-impact, but at a low spatial resolution (1 pixel projected to 1500 km at the comet). The former observations offered a less extensive temporal coverage (about 3 hrs per night from June 25 to July 7) but at a higher spatial resolution (1 pixel projected to 600 km at the comet). The angle of 27 degrees between the two lines-of-sight further allowed to follow the same event from two different viewing angles. We present a combined preliminary analysis of the images obtained with both instruments. The dust production rate is monitored via two proxies, the [Afrho] parameter and the dust cross section, which is more appropriate in the case of a non-canonic coma. This indicates that the comet went back to its normal, pre-impact state within about 7 days of the impact thus showing that it did not create a detectable active region. Dust structures were found and followed in the coma and in the dust tail and we discuss their significance. Several spectral analysis of the pre-impact light curve reveal a periodic variation attributed to the rotation of the nucleus with a period of about 41 hrs. Title: The rotational state of the nucleus of comet 9P/Tempel 1 Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A. Bibcode: 2005DPS....37.4411L Altcode: 2005BAAS...37Q1568L The nucleus of comet 9P/Tempel 1 was observed with the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) in May 2004, in an effort to pin down its rotational period and assist in the preparation of the operations of the Deep Impact mission. The observations were performed from May 7.9 to 9.5, 2004, and extended over a 39-hour period. At the mid-point of the observing window, the comet was 3.52 AU from the Sun , 4.03 AU from the Earth and at a phase angle of 13.5 deg. The program consisted in 18 separate visits, each one corresponding to an HST orbit and including 3 identical exposures of 857 sec duration with the F606W broadband filter. These very deep exposures revealed a point-source object, albeit the nucleus, without any coma. Photometry was performed by PSF fitting, the required (model) PSFs being generated with the TinyTim software. The mean V magnitude of the nucleus was 21.85 and had an amplitude of 0.45 mag indicating that we were seeing the varying cross-section of a rotating, elongated body. There is a very clear asymmetry between the two half-periods of the light curve with one minimum being much deeper than the other. The periodicity was analyzed with six different techniques yielding a rotational period in the range 38.32 to 42.68 hr, and resulting in a mean value of 41.0 hr. Title: The colors of cometary nuclei and other primitive bodies Authors: Toth, I.; Lamy, P. L. Bibcode: 2005DPS....37.1617T Altcode: 2005BAAS...37.1563T Primitive minor objects like Kuiper-belt objects (KBOs), Centaurs, cometary nuclei and low-albedo asteroids contain a considerable amount of information regarding the formation of early solar system planetesimals and some of the primordial processes. Broadband colors by themselves offer limited insight into surface composition but correlations either between different color indices or with other (e.g., orbital) parameters can shed some light on the questions of the composition and the evolution of the minor objects. Furthermore, a systematic comparison of the color indices of various populations may provide clues on their relationships, and concur along with dynamical studies, to establish a scenario of their formation and evolution in the solar system. We present new color results on cometary nuclei obtained with the Hubble Space Telescope (HST) whose superior resolution enables us to accurately isolate the nucleus signals from the surrounding comae. By combining with scrutinized available data obtained with ground-based telescopes, we accumulated a sample of 39 cometary nuclei, 34 ecliptic comets (ECs) and 5 nearly-isotropic comets (NICs) using the nomenclature of Levison (1996). We analyze color distributions and color-color correlations as well as correlations with other physical parameters. We present our own compilation of colors of 282 objects in the outer solar system, separately considering the different dynamical populations, classical KBOs in low and high-inclination orbits, resonant KBOs (practically Plutinos), scattered-disk objects (SDOs) and Centaurs. We perform a systematic analysis of color distributions of all plausible parent-child combinations and conclude by synthesizing the implications of the colors for the origin of ecliptic comets.

We acknowledge the support of the French "Programme National de Planétologie", jointly funded by CNRS and CNES, and of the bilateral French--Hungarian cooperation program. I. Toth further acknowledges the support of the Université de Provence, of the Hungarian Academy of Sciences through grant No. 9871. Title: Hubble Space Telescope observations of the nucleus fragment 73P/Schwassmann Wachmann 3-C Authors: Toth, I.; Lamy, P.; Weaver, H. A. Bibcode: 2005Icar..178..235T Altcode: The investigation of fragmented comets provides information on the physical properties and internal structure of cometary nuclei, as well as insights into the mechanisms responsible for cometary breakups. The Jupiter-family Comet 73P/Schwassmann-Wachmann 3 (73P/SW3) fragmented non-tidally into at least four components, and probably more, in the autumn of 1995. Fragment C was detected with the Wide Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope (HST) on 26 November 2001 when it was 3.26 AU from the Sun and 2.34 AU from the Earth. The high spatial resolution of the HST allowed us to separate the signal of the fragment from that of its coma, and to determine its R magnitude in the Johnson-Kron-Cousins photometric system from four images taken with the F675W filter. Assuming a spherical body with a geometric albedo of 0.04 and a linear phase coefficient of 0.04 mag deg -1 for the R band, we derived an effective radius of 0.68±0.04km. The pre-breakup radius of the original nucleus was estimated to be 1.1 km, which implies that the volume of fragment C is ∼25% of the total volume of the pre-breakup nucleus. The limited temporal coverage of our observations preclude deriving an accurate shape or rotational period; our measurements are consistent with a rather spherical body but an elongated shape cannot be excluded. Fragment C was very active despite its rather large heliocentric distance, with an estimated dust production rate of ∼1.5kgs (∼130 metric tons day -1). A very large fraction of the surface area of fragment C must have been sublimating to sustain such a high level of activity. Fragment C may be recovered at its next return in 2006, if it does not experience further fragmentation. Title: On the 3-dimensional structure of the streamer belt of the solar corona Authors: Saez, F.; Zhukov, A. N.; Lamy, P.; Llebaria, A. Bibcode: 2005A&A...442..351S Altcode: We investigate the three-dimensional structure of the streamer belt of the solar corona using a model that allows us to simulate its quasi-stationary configuration. Starting from the National Solar Observatory photospheric magnetograms, the position of the neutral line at the source surface (2.5 ~R_⊙) is determined using the potential field source surface model. A plasma sheet is centered around the current sheet represented as the radial extension of the neutral line. Comparing the synoptic maps of the streamer belt obtained with the SOHO/LASCO-C2 coronagraph and the simulated synoptic maps constructed from our model of the warped plasma sheet, we confirm earlier findings by Wang et al. (1997, ApJ, 485, 875; Wang et al. 2000, Geophys. Res. Lett., 27, 149) that the streamers are associated with folds in the plasma sheet. Although the large-scale structure of the streamer belt is described reasonably well, some features, however, cannot be explained in this framework. We propose that two types of large-scale structures take part in the formation of these additional features. The first one is an additional fold of the neutral line, which does not appear in the modeled source surface neutral line, but is well visible in photospheric magnetograms. The second one is a plasma sheet with a ramification in the form of a secondary short plasma sheet. We show that these structures better describe the observed configurations of the streamer belt. The secondary plasma sheet can be formed between two secondary current sheets connected to the main current sheet. Our results suggest that the potential field source surface model is not fully adequate for the description of the fine structure of the streamer belt, even during the time of low solar activity. Title: A large dust/ice ratio in the nucleus of comet 9P/Tempel 1 Authors: Küppers, Michael; Bertini, Ivano; Fornasier, Sonia; Gutierrez, Pedro J.; Hviid, Stubbe F.; Jorda, Laurent; Keller, Horst Uwe; Knollenberg, Jörg; Koschny, Detlef; Kramm, Rainer; Lara, Luisa-Maria; Sierks, Holger; Thomas, Nicolas; Barbieri, Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; A'Hearn, M. F.; Angrilli, F.; Bailey, M.; Barthol, P.; Barucci, M. A.; Bertaux, J. -L.; Burns, J. A.; Cremonese, G.; Curdt, W.; De Cecco, M.; Debei, S.; Fulle, M.; Gliem, F.; Ip, W. H.; Huhrt, E.; Llebaria, A.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Sabau, L.; Sanz Andres, A.; Sivan, J. P.; Tondello, G.; Wenzel, K. -P. Bibcode: 2005Natur.437..987K Altcode: Comets spend most of their life in a low-temperature environment far from the Sun. They are therefore relatively unprocessed and maintain information about the formation conditions of the planetary system, but the structure and composition of their nuclei are poorly understood. Although in situ and remote measurements have derived the global properties of some cometary nuclei, little is known about their interiors. The Deep Impact mission shot a projectile into comet 9P/Tempel 1 in order to investigate its interior. Here we report the water vapour content (1.5 × 1032 water molecules or 4.5 × 106kg) and the cross-section of the dust (330km2 assuming an albedo of 0.1) created by the impact. The corresponding dust/ice mass ratio is probably larger than one, suggesting that comets are `icy dirtballs' rather than `dirty snowballs' as commonly believed. High dust velocities (between 110ms-1 and 300ms-1) imply acceleration in the comet's coma, probably by water molecules sublimated by solar radiation. We did not find evidence of enhanced activity of 9P/Tempel 1 in the days after the impact, suggesting that in general impacts of meteoroids are not the cause of cometary outbursts. Title: Deep Impact Observations by OSIRIS Onboard the Rosetta Spacecraft Authors: Keller, Horst Uwe; Jorda, Laurent; Küppers, Michael; Gutierrez, Pedro J.; Hviid, Stubbe F.; Knollenberg, Jörg; Lara, Luisa-Maria; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael Bibcode: 2005Sci...310..281K Altcode: The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging system) onboard the European Space Agency's Rosetta spacecraft observed comet 9P/Tempel 1 for 17 days continuously around the time of NASA's Deep Impact mission. The cyanide-to-water production ratio was slightly enhanced in the impact cloud, compared with that of normal comet activity. Dust particles were flowing outward in the coma at >160 meters per second, accelerated by the gas. The slope of the brightness increase showed a dip about 200 seconds after the impact. Dust Afρ values before and long after the impact confirm the slight decrease of cometary activity. The dust-to-water mass ratio was much larger than 1. Title: Outgassing-induced effects in the rotational state of comet 67P/Churyumov—Gerasimenko during the Rosetta mission Authors: Gutiérrez, Pedro J.; Jorda, Laurent; Samarasinha, Nalin H.; Lamy, Philippe Bibcode: 2005P&SS...53.1135G Altcode: The new target of the Rosetta mission is comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G). In order to support the planning of the mission, in particular the strategy during the mapping and landing phases, we have performed numerical simulations of the rotational evolution of a comet in the orbit of 67P/C-G. In these simulations, the currently known observational constraints have been taken into account and a large set of initial conditions were considered. For most of the simulations, we observe that the sublimation-induced torques produce significant changes in the rotational parameters of a 67P/C-G-like comet. Typical rates of change for the spin period from the rendezvous up to the end of the nominal mission range from 0.001 to 0.05hday-1 depending on different circumstances as described in the text. At perihelion, rates of change of the orientation of the angular momentum vector amount to about 0.01- 0.1degday-1. These simulations suggest that a specific strategy should be defined in order to monitor likely variations of the rotational parameters. As an example we show a possible optimized schedule for observations with the OSIRIS instrument to determine the rotational parameters of comet 67P/C-G and their possible evolution. Title: Formation flyers applied to solar coronal observations: the ASPICS mission Authors: Vives, S.; Lamy, P.; Auchere, F.; Vial, J. -C.; Koutchmy, S.; Arnaud, J.; Prado, J. -Y.; Frassetto, F.; Naletto, G. Bibcode: 2005SPIE.5901..305V Altcode: Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent observing the inner corona inside typically 2-2.5 solar radii. Formation flyers open new perspectives and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at approximately 100 m from the first one. ASPICS (Association de Satellites Pour l'Imagerie Coronographique Solaire) is a mission proposed to CNES in the framework of their demonstration program of formation flyers which is presently under study to exploit this technique for coronal observations. In the baseline concept, ASPICS includes three coronagraphs operating in three spectral domains: the visible continuum (K-corona brightness), the HI Lyman alpha emission line at 121.6 nm, and the HeII emission line at 30.4 nm. Their unvignetted fields of view extend from 1.1 to 3.2 solar radii with a typical spatial resolution of 3 arcsec. In order to connect coronal activity to photospheric events, ASPICS further includes two disk imagers. The first one is devoted to the HI Lyman alpha emission line. The second one is a multi-channel instrument similar to SOHO/EIT and devoted to the HeII (30.4 nm), FeIX/X (17.1 nm) and FeXII (19.5 nm) emission lines. Two concepts of the space system are under consideration: a symmetric configuration where the disk imagers and the external occulter are on one spacecraft and the coronagraphs on the other, an asymmetric configuration where the external occulter is on one spacecraft and the scientific instruments are regrouped on the other one. Title: Possible optical design for ASPICS, a formation-flyer solar coronagraph for close-limb visible and Lyman-α imaging of the corona Authors: Frassetto, Fabio; Naletto, Giampiero; Vives, Sebastien; Lamy, Philippe Bibcode: 2005SPIE.5901..316F Altcode: The recent possibility of deploying clusters of satellites in flight formation allows the development of a new generation of space instruments, and among them, of externally occulted solar coronagraphs. This can be implemented by introducing a large occulter on a first satellite, and all the remaining optical system on a second satellite, located in the shadow of the occulter. Since the capability of looking close to the solar limb is directly related to the distance between the external occulter and the coronagraphic objective, formation flyers offer the capability of a major improvement in observing the lower corona from space. In this paper, we describe a possible optical design for ASPICS, a formation flyer solar coronagraph composed of two satellites separated by about 100 m. The proposed dual channel design will allow for the first time to simultaneously observe the lower and intermediate corona in both visible and ultraviolet (HI Lyman-α line) spectral regions at a 6 arcsec/pixel scale factor with a single instrument. Title: Concept of formation flyer for the ASPICS solar coronagraphic mission Authors: Leyre, Xavier; Sghedoni, M.; Vives, S.; Lamy, P.; Pailharey, E. Bibcode: 2005SPIE.5899..221L Altcode: This paper describes a concept of a formation flyer for ASPICS (Association de Satellites Pour l'Imagerie et la Coronagraphie Solaire), a giant 100 m based, externally occulted coronagraph aimed at observing the inner corona (and the solar disk) in the visible and ultra-violet. The two-satellite formation approach, based on existing space systems, is composed of a Myriade micro-satellite supporting the occulter and a Proteus platform as the main system carrying the coronagraph and imager scientific instruments. Both spacecrafts are launched as a single composite and deployed once on orbit, preferably a 3-day orbit or at the L1 Lagrange point. The coronagraph satellite acts as the "master" and provides the main functions of the mission (data handling, communication, propulsion, Guidance Navigation and control) while the Myriade acts as the "slave". The control of the formation is performed in two steps: i) RF metrology for deployment and preliminary pointing, ii) classical optical attitude sensors and metrology based on diverging laser beams. This will insure the nominal requirement of a lateral positioning with an accuracy of 1 mm and a longitudinal positioning with an accuracy of 500 mm. Title: Light Curves of Kreutz Comets Authors: Knight, M. M.; A'Hearn, M. F.; Biesecker, D. A.; Faury, G.; Hamilton, D. P.; Lamy, P.; Llebaria, A. Bibcode: 2005DPS....37.1103K Altcode: 2005BAAS...37Q.632K We present the results of our study of the light curves of the Kreutz family comets observed by SOHO-LASCO. This is a continuation of the earlier work by Biesecker et al. (2002) and includes all Kreutz comets which reached perihelion in the SOHO-LASCO field of view by the end of 2003, a sample of more than 600 comets. We do not see the bimodality of the light curves found by Biesecker et al., however we find that the brightest comets increase in brightness more rapidly and fade more slowly than fainter comets. To test if the slope of the brightening seen at the small heliocentric distances observed by SOHO-LASCO (inside 0.14 AU) extends to larger distances (1-3 AU), we imaged fields statistically likely to contain Kreutz comets prior to their entering the SOHO-LASCO field of view using the Kitt Peak National Observatory 4-m telescope with the MOSAIC wide-field imager in January 2005. No comets were discovered in these fields, however they will be searched again using the ephemerides of all Kreutz comets that reach perihelion in the SOHO-LASCO field of view during May and June 2005, since some of these comets should have been in the observed fields. This will allow us to set constraints on the rate of brightening at heliocentric distances beyond the SOHO-LASCO field of view.

This work is supported by the NASA Planetary Atmospheres Program under grant NAG513295. Title: Automatic detection of coronal mass ejections on LASCO-C2 synoptic maps Authors: Boursier, Yannick; Llebaria, Antoine; Goudail, Francois; Lamy, Philippe; Robelus, Sebastien Bibcode: 2005SPIE.5901...13B Altcode: The LASCO-C2 coronagraph on-board the SOHO solar observatory has been providing a continuous flow of coronal images for the past nine years. Synoptic maps for each Carrington rotation have been constructed from these images and offer a global view of the temporal evolution of the solar corona, particularly the occurrence of transient events such as the coronal mass ejections (CMEs), an important component of space weather activity. CMEs present distinct signatures on synoptic maps offering a novel approach to the problem of their statistical detection. We are presently testing several techniques of automatic detection based on their morphological properties. The basic procedure involves three steps: i) morphological characterization, ii) definition and application of adapted filters (optimal trade-off filters, Canny filter,...), iii) segmentation of the filtered synoptic maps. At this stage, the CMEs are detected. The efficiency of the detection of the various filters is estimated using the ROC curves. On-going studies include the classification of CMEs based on their physical properties, the determination of their velocities, and the question of their connection to the streamer belt. Title: Characterization of Asteroids 2867 Steins and 21 Lutetia, Targets of the Rosetta Mission Authors: Lamy, Philippe; Barucci, Antonella; Carvano, Jorge; Cruikshank, Dale; Dotto, Elisabetta; Fornasier, Sonia; Fulchignoni, Marcello; Groussin, Olivier; Jorda, Laurent; Migliorini, Alessandra Bibcode: 2005sptz.prop20653L Altcode: Asteroids 2867 Steins and 21 Lutetia are the new targets of the Rosetta mission. Our present knowledge of these two objects is still very limited. Their albedos are either unknown (Steins) or subject to question (Lutetia), with severe consequences for their sizes and their taxonomic classifications and their surface compositions are either unclear or controversial. We propose to investigate the physical properties (size, shape), the surface and thermal properties (albedo, thermal inertia, surface roughness) and surface composition of these two asteroids by taking advantage of the capabilities and performances of the Spitzer Space Telescope (SST), supplemented by ground-based observations. The SST observations consist in taking low resolution spectra with the IRS instrument over its full wavelength range 5-38 micron. Each asteroid will be observed 14 times at time intervals of 30 min for Steins and 40 mn for Lutetia in order to properly sample their light curve. The detailed knowledge of these asteroids that will result from our proposed program will be of critical importance for optimizing the flyby strategy of the Rosetta spacecraft and the operation of its instruments. They will later supplement the in-situ observations necessarily limited by the conditions of a fast flyby and contribute to their global characterization. Title: A Multiwavelength Investigation of Comet 73P/SW3-C Authors: Lamy, Philippe; Weaver, Harold; Jorda, Laurent; A'Hearn, Michael; Toth, Imre; Groussin, Olivier; Kaasalainen, Mikko; Lowry, Stephem Bibcode: 2005sptz.prop20001L Altcode: The nucleus of comet 73P/Schwassmann-Wachmann-3 experienced a non-tidal breakup in late 1995. The largest fragment (73P/SW3-C) survived its subsequent perihelion passage in 2001 and will return in 2006, when it will pass very close to (0.08AU) Earth. This represents an outstanding opportunity to characterize a fresh cometary nucleus, and we propose an intensive investigation using both the Hubble and Spitzer telescopes. Employing the technique that our group has developed over the past decade to characterize 31 cometary nuclei, we will use HST/ACS to photometrically resolve the nucleus of 73P/SW3-C at optical wavelengths and SST/MIPS to do the same thing at thermal infrared wavelengths, thereby allowing us to determine both the size and albedo of this fragment. We also plan to measure the lightcurve of 73P/SW3-C to obtain detailed shape information, and use HST/NICMOS to probe the composition, in particular to search for evidence of icy material on the fresh surface. Previous observations indicate that most of the remaining mass of 73P/SW3 is in the form of numerous small fragments. A few of those may have been captured by the C fragment, and the determination of their orbits would allow the first, direct measurement of the mass of a cometary nucleus. Thus, we will also perform a deep search for any possible companions to the C-fragment. Title: Deep Impact: Working Properties for the Target Nucleus Comet 9P/Tempel 1 Authors: Belton, Michael J. S.; Meech, Karen J.; A'Hearn, Michael F.; Groussin, Olivier; McFadden, Lucy; Lisse, Carey; Fernández, Yanga R.; Pittichová, Jana; Hsieh, Henry; Kissel, Jochen; Klaasen, Kenneth; Lamy, Philippe; Prialnik, Dina; Sunshine, Jessica; Thomas, Peter; Toth, Imre Bibcode: 2005SSRv..117..137B Altcode: In 1998, Comet 9P/Tempel 1 was chosen as the target of the Deep Impact mission (A’Hearn, M. F., Belton, M. J. S., and Delamere, A., Space Sci. Rev., 2005) even though very little was known about its physical properties. Efforts were immediately begun to improve this situation by the Deep Impact Science Team leading to the founding of a worldwide observing campaign (Meech et al., Space Sci. Rev., 2005a). This campaign has already produced a great deal of information on the global properties of the comet’s nucleus (summarized in Table I) that is vital to the planning and the assessment of the chances of success at the impact and encounter. Since the mission was begun the successful encounters of the Deep Space 1 spacecraft at Comet 19P/Borrelly and the Stardust spacecraft at Comet 81P/Wild 2 have occurred yielding new information on the state of the nuclei of these two comets. This information, together with earlier results on the nucleus of comet 1P/Halley from the European Space Agency’s Giotto, the Soviet Vega mission, and various ground-based observational and theoretical studies, is used as a basis for conjectures on the morphological, geological, mechanical, and compositional properties of the surface and subsurface that Deep Impact may find at 9P/Tempel 1. We adopt the following working values (circa December 2004) for the nucleus parameters of prime importance to Deep Impact as follows: mean effective radius = 3.25± 0.2 km, shape irregular triaxial ellipsoid with a/b = 3.2± 0.4 and overall dimensions of ∼14.4 × 4.4 × 4.4 km, principal axis rotation with period = 41.85± 0.1 hr, pole directions (RA, Dec, J2000) = 46± 10, 73± 10 deg (Pole 1) or 287± 14, 16.5± 10 deg (Pole 2) (the two poles are photometrically, but not geometrically, equivalent), Kron-Cousins (V-R) color = 0.56± 0.02, V-band geometric albedo = 0.04± 0.01, R-band geometric albedo = 0.05± 0.01, R-band H(1,1,0) = 14.441± 0.067, and mass ∼7×1013 kg assuming a bulk density of 500 kg m-3. As these are working values, {i.e.}, based on preliminary analyses, it is expected that adjustments to their values may be made before encounter as improved estimates become available through further analysis of the large database being made available by the Deep Impact observing campaign. Given the parameters listed above the impact will occur in an environment where the local gravity is estimated at 0.027 0.04 cm s-2 and the escape velocity between 1.4 and 2 m s-1. For both of the rotation poles found here, the Deep Impact spacecraft on approach to encounter will find the rotation axis close to the plane of the sky (aspect angles 82.2 and 69.7 deg. for pole 1 and 2, respectively). However, until the rotation period estimate is substantially improved, it will remain uncertain whether the impactor will collide with the broadside or the ends of the nucleus. Title: UVCS Observation of Sungrazer C/2001 C2: Possible Comet Fragmentation and Plasma-Dust Interactions Authors: Bemporad, A.; Poletto, G.; Raymond, J. C.; Biesecker, D. A.; Marsden, B.; Lamy, P.; Ko, Y. -K.; Uzzo, M. Bibcode: 2005ApJ...620..523B Altcode: In this paper we analyze SOHO Ultraviolet Coronagraph Spectrometer (UVCS) observations of the sungrazing comet C/2001 C2, a member of the Kreutz family, observed on 2001 February 7 at heliocentric distances of 4.98 and 3.60 Rsolar. This comet apparently went through sequential fragmentation events along its path: further indication of fragmentation processes is provided by UVCS observations, which show the presence of two separate tails in the 4.98 Rsolar data set, which we interpret as two fragments unresolved by LASCO images, one of which sublimates before reaching 3.60 Rsolar. The cometary hydrogen Lyα signal, decaying exponentially with time, has been interpreted in terms of the H2O outgassing rate and the interactions of coronal protons with atoms created by the photodissociation of water. However, one of the fragments shows an additional Lyα contribution, constant with time, which adds to the temporally decaying signal. This contribution has been ascribed to the sublimation of pyroxene dust grains, whose end products neutralize coronal protons via charge exchange processes. Hence, the two fragments have different composition; differences throughout the comet body may have been the primary cause for the comet fragmentation. Title: The SIde-Looking Coronagraph for the solar orbiter mission: Optical and mechanical designs Authors: Vivès, S.; Lamy, P.; Guitton, J.; Boit, J. L.; Dargent, P. Bibcode: 2005AdSpR..36.1406V Altcode: The SIde-Looking Coronagraph (SILC) is intented to be proposed as part of the payload of the Solar Orbiter mission of the European Space Agency. Solar Orbiter will follow elliptic orbits with a large range of heliocentric distance, from 0.21 to 0.6 AU, and will reach heliographic latitudes as high as 38°. Furthermore, the spacecraft will have an offset pointing capability so as to target any point of the solar disk. These characteristics, in addition to the severe thermal environment, are very restrictive for a coronagraph and lead us to propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally occulted coronagraph adapted to the side-looking concept. Although SILC loses the full spatial coverage of the corona, it can observe the inner part of the corona (down to 1.5 solar radii) during the whole mission and compensate the off-pointing of the spacecraft. The optical and mechanical designs of SILC are presented in detail. Title: Meteoroid Streams Associated to Comets 9P/Tempel 1 and 67P/Churyumov-Gerasimenko Authors: Vaubaillon, J.; Lamy, P.; Jorda, L. Bibcode: 2004EM&P...95...75V Altcode: 2005EM&P...95...75V The meteoroid streams associated to short-period comets 9P/Tempel 1 (the target of the Deep Impact mission). and 67P/Churyumov-Gerasimenko (the target of the Rosetta mission) are studied. Their structure is overwhelmingly under the control of Jupiter and repeated relatively close encounters cause a reversal of the direction of the spatial distribution of the stream relative to the comet* an initial stream trailing the comet as usually seen eventually collapses, becomes a new stream leading the comet and even splits into several components. Although these two comets do not produce meteor showers on Earth, this above feature shows that meteor storms can occur several years before the perihelion passage of a parent body. Title: Physical Properties of the Deep Impact Target Comet 9P/Tempel 1 from Spitzer and Hubble Space Telescope Observations Authors: Lisse, C. M.; A'Hearn, M. F.; Belton, M. J. S.; Fernandez, Y. R.; Groussin, O.; Lamy, P.; Meech, K. J.; Toth, I.; Weaver, H. A. Bibcode: 2004DPS....36.3402L Altcode: 2004BAAS...36Q1148L Comet 9P/Tempel 1 is the target of the Deep Impact mission to be launched at the end of this year. Accurate knowledge of the physical properties of the comet's nucleus is important for mission success. Current published size estimates for the nucleus are uncertain by 50% [Fernandez et al. 2003] and the current best rotational solutions have periods of 22 and 42 hours [Belton and Meech, 2004].

In Spring 2004, with the comet outside the ice line and inactive and inbound on the final leg before the DI encounter, we obtained 12 spectrophotometric (7.5-40 microns) visits of the nucleus with the Spitzer Space Telescope over a 40 hour period in March 2004, and 18 photometric (F606) visits over a 42 hour period in May 2004 with the Hubble Space Telescope. Collating these observations into lightcurves, we have applied rotational and thermal models [Belton et al. 2005, Groussin et al. 2004] to derive values for the effective radius, axial ratio, pole position, bulk surface albedo, active surface area, and thermal inertia. Initial analysis of the observations has yielded a nucleus with an average radius of about 3 km, an axial ratio of about 3, a geometric albedo of about 4%, and an active surface fraction of about 8%. The thermal inertia is low, similar to that of other primitive bodies. The rotation pole orientation's J2000 RA and Dec are either (99o,-19o) or (60o,+72o) , with an error of about 4 degrees. We present the latest results of our observations and analysis here. Title: The Cassini Cosmic Dust Analyzer Authors: Srama, R.; Ahrens, T. J.; Altobelli, N.; Auer, S.; Bradley, J. G.; Burton, M.; Dikarev, V. V.; Economou, T.; Fechtig, H.; Görlich, M.; Grande, M.; Graps, A.; Grün, E.; Havnes, O.; Helfert, S.; Horanyi, M.; Igenbergs, E.; Jessberger, E. K.; Johnson, T. V.; Kempf, S.; Krivov, A. V.; Krüger, H.; Mocker-Ahlreep, A.; Moragas-Klostermeyer, G.; Lamy, P.; Landgraf, M.; Linkert, D.; Linkert, G.; Lura, F.; McDonnell, J. A. M.; Möhlmann, D.; Morfill, G. E.; Müller, M.; Roy, M.; Schäfer, G.; Schlotzhauer, G.; Schwehm, G. H.; Spahn, F.; Stübig, M.; Svestka, J.; Tschernjawski, V.; Tuzzolino, A. J.; Wäsch, R.; Zook, H. A. Bibcode: 2004SSRv..114..465S Altcode: The Cassini-Huygens Cosmic Dust Analyzer (CDA) is intended to provide direct observations of dust grains with masses between 10-19 and 10-9 kg in interplanetary space and in the jovian and saturnian systems, to investigate their physical, chemical and dynamical properties as functions of the distances to the Sun, to Jupiter and to Saturn and its satellites and rings, to study their interaction with the saturnian rings, satellites and magnetosphere. Chemical composition of interplanetary meteoroids will be compared with asteroidal and cometary dust, as well as with Saturn dust, ejecta from rings and satellites. Ring and satellites phenomena which might be effects of meteoroid impacts will be compared with the interplanetary dust environment. Electrical charges of particulate matter in the magnetosphere and its consequences will be studied, e.g. the effects of the ambient plasma and the magnetic field on the trajectories of dust particles as well as fragmentation of particles due to electrostatic disruption. Title: The Side-Looking Coronagraph (SILC) for the Solar Orbiter mission: optical performances Authors: Vivès, Sébastien; Lamy, Philippe Bibcode: 2004ESASP.554..381V Altcode: 2004icso.conf..381V The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing instruments proposed for the payload of the Solar Orbiter mission (European Space Agency, ESA). The specificities of the Solar Orbiter mission are very restrictive for a coronagraph: large range of heliocentric distance from 0.21 to 0.6 AU, offset pointing capability of the spacecraft, severe thermal environment of limited mass and volume available. To cope with them, we propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally-occulted coronagraph adapted to the side-looking concept. The performances and the expected stray light level will be presented here together with their evolution as function of the heliocentric distance. Title: The August 11th, 1999 CME Authors: Koutchmy, S.; Baudin, F.; Bocchialini, K.; Daniel, J. -Y.; Delaboudinière, J. -P.; Golub, L.; Lamy, P.; Adjabshirizadeh, A. Bibcode: 2004A&A...420..709K Altcode: We present here a set of observations, space borne and ground based, at different wavelengths, of the solar corona at and after the time of the total solar eclipse of August 11{th}. It is used to consider some unusual features of the coronal dynamics related to a limb Coronal Mass Ejection (CME) observed after the total eclipse. The complementary aspect of simultaneous ground-based and space-borne observations of the corona is used to produce an accurate composite image of the White Light (W-L) corona before the CME. A high arch system (possibly a dome-like structure, with large cavities inside but without a cusp further out) which appeared on the eclipse W-L images, is suggested to be a large-scale precursor of the CME, well preceding the eruption of the top part of the brightest prominence recorded in W-L. This bright prominence is shown as a filament in absorption using the Transition Region And Corona Explorer (TRACE) images taken in different coronal lines. The analysis of the images of the Large Angle and Spectrometric Coronograph (LASCO) on board the Solar and Heliospheric Observatory (SoHO), showing the progression of the CME, is discussed in an attempt to make a connection with the surface event. A SoHO-EIT (Extreme UV Imager Telescope) image sequence details the prominence eruption and shows the sudden heating processes of the ejected parts. We found that there is no reason to assume that the huge cavity is significantly destabilised well before the eruption of the upper part of the low-lying bright twisted filament which coincides with the position of one of the legs of the high arch. Observations are still compatible with the assumption of both the break-out model and of the flux rope erupting model as a result of a shear or of an increasing poloıdal magnetic flux from below. We stress the possible role of buoyancy of the giant cavity as a destabilizing factor leading to the CME, noticing that some motion of coronal material back toward the surface can be seen during at least the first phase of the CME, from both EIT and LASCO observations. Title: Preliminary calibration results of the wide angle camera of the imaging instrument OSIRIS for the Rosetta mission Authors: da Deppo, V.; Naletto, G.; Nicolosi, P.; Zambolin, P.; de Cecco, M.; Debei, S.; Parzianello, G.; Ramous, P.; Zaccariotto, M.; Fornasier, S.; Verani, S.; Thomas, N.; Barthol, P.; Hviid, S. F.; Sebastian, I.; Meller, R.; Sierks, H.; Keller, H. U.; Barbieri, C.; Angrilli, F.; Lamy, P.; Rodrigo, R.; Rickman, H.; Wenzel, K. P. Bibcode: 2004ESASP.554..191D Altcode: 2004icso.conf..191D Rosetta is one of the cornerstone missions of the European Space Agency for having a rendezvous with the comet 67P/Churyumov-Gerasimenko in 2014. The imaging instrument on board the satellite is OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System), a cooperation among several European institutes, which consists of two cameras: a Narrow (NAC) and a Wide Angle Camera (WAC). The WAC optical design is an innovative one: it adopts an all reflecting, unvignetted and unobstructed two mirror configuration which allows to cover a 12°x12° field of view with an F/5.6 aperture and gives a nominal contrast ratio of about 10-4. The flight model of this camera has been successfully integrated and tested in our laboratories, and finally has been integrated on the satellite which is now waiting to be launched in February 2004. In this paper we are going to describe the optical characteristics of the camera, and to summarize the results so far obtained with the preliminary calibration data. The analysis of the optical performance of this model shows a good agreement between theoretical performance and experimental results. Title: The nuclei of comets 126P/IRAS and 103P/Hartley 2 Authors: Groussin, O.; Lamy, P.; Jorda, L.; Toth, I. Bibcode: 2004A&A...419..375G Altcode: We report the detection of the nucleus of 126P/IRAS and 103P/Hartley 2 with the Infrared Camera of the Infrared Space Observatory (ISOCAM). 126P/IRAS was observed on 12 November 1996, when it was at r_h=1.71 AU from the Sun and Δ=1.32 AU from the Earth. 103P/Hartley 2 was observed on 5 February 1998, when it was at r_h=1.21 AU from the Sun and Δ=0.91 AU from the Earth. The observations were performed with the broadband LW10 filter centered at 11.5 μm. The spatial resolution was adequate to separate the thermal emission of the nuclei from that of their respective comae. We combined the ISOCAM observations with measured water production rates, using a model that considers a spherical nucleus with a macroscopic mosaic of small and numerous active and inactive regions, and we derived a radius of 1.57±0.14 km and an active fraction at perihelion of 0.11±0.03 for 126P/IRAS, and a radius of 0.71±0.13 km and an active fraction of ∼1 at perihelion and 0.30±0.11 at 1.11 AU post-perihelion for 103P/Hartley 2. These two examples illustrate the large diversity of activity pattern that exists among cometary nuclei.

Based on observations made with the Infrared Space Observatory, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and UK) and with the participation of ISAS and NASA. Title: Lessons learned from the SOHO/LASCO-C2 calibration Authors: Llebaria, Antoine; Lamy, Philippe L.; Bout, Maurice V. Bibcode: 2004SPIE.5171...26L Altcode: The LASCO-C2 coronagraph onboard the SOHO solar probe have been providing for the last seven years an unprecedented long sequence of coronal images at high cadence (about 75 images/day). The LASCO-C2 calibrations included the determination of the geometric characteristics (attitude, distortion) as well as the photometric and photopolarimetric responses. Such calibrations needed resort to a complementary set of approaches including optical-modelling, pre-flight measures and in-orbit measures and monitoring. In this paper we discuss about the specific contribution of each of them, the example of radiometric calibration of LASCO-C2 is dominated by the strong vignetting induced by the occultors. The occultors fully mask the extended circular area centered on the Sun image. Due to operational constraints the vignetting function has been obtained using a complementary set of approaches: 1) ray tracing, 2) the geometric convolution of diaphragms, 3) the measure of uniform sources in laboratory, 4) the measures in orbit of the stars and F-corona. Finaly the relationship of radiometry with geometric calibrations, strylight calibration and the log term stability monitoring is discussed. Title: Optical design of the Lyman alpha coronagraph for the LYOT microsatellite Authors: Vives, Sebastien; Lamy, Philippe L.; Vial, Jean-Claude Bibcode: 2004SPIE.5171..298V Altcode: The LYOT (LYman Orbiting Telescope) solar mission (proposed for a CNES micro-satellite) is composed of a disk imager and a coronagraph, both working at Lyman-α (121.6 nm). The coronagraph is internally occulted and all-reflective with a field-of-view of 1.2 R up to 2.5 R and high spatial resolution (2 pixels) amounts to 5 arcsec. The optical design is driven by the requirement to use a superpolished spherical mirror to minimize the scattered light into the instrument. The LYOT mission will observe the Lyman-α corona at high cadence (1 image/5 minutes) over a period of two years. Title: Visible, externally occulted coronagraph for Solar Orbiter Authors: Vives, Sebastien; Lamy, Philippe L.; Korendyke, Clarence Bibcode: 2004SPIE.5171..131V Altcode: The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing instruments proposed for the payload of the Solar Orbiter mission. The Solar Orbiter is a mission selected in September 2000 by the European Space Agency (ESA) for the definition study phase. The Solar Orbiter will describe elliptic orbits with a large range of heliocentric distance, from 0.21 to 0.6 AU (astronomical units), that is a factor 3 for the geometric conditions and will reach heliographic latitudes as high as 38 degrees. Furthermore, the spacecraft will have offset pointing capability so as to target any point of the solar disk. These constraints (in addition to the severe thermal environment) lead us to propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally-occulted coronagraph adapted to the side-looking concept. Although SILC loses the full spatial coverage of the corona, it can observe the inner part of the corona (down to 1.5R) during the whole mission and compensate the off-pointing of the spacecraft in the two directions. The performances, resulting from ray-tracing calculations, are presented here together with the expected stray light level. Title: Measuring the Size and Shape of Comet 67P/Churyumov-Gerasimenko, the Target of the Rosetta Mission Authors: Lamy, Philippe Bibcode: 2004sptz.prop..222L Altcode: In support of the Rosetta mission, we request Director's Discretionary time to measure the size and shape of its target, the nucleus of comet 67P/Churyumov-Gerasimenko. A safe landing of the Lander package on its surface remains critically dependent upon its size which is not unambiguoulsy determined from visible photometry because of the uncertainty on its albedo. On the contrary, measurements of the thermal emission of the nucleus will allow a direct determination of its size. Observations with the Spitzer Space Telescope in late February 2004 will provide the best possible data thanks to very favourable observing conditions. We propose to use MIPS to image the nucleus at 24 microns seventeen times, over a time interval of 12.5 hr to as to cover the full light curve of the nucleus and derive both its size and shape. Complementary observations at 70 microns will help constraining its SED and the thermal model to interpret the data. By further combining with past HST observations, the rotational state of the nucleus will be better con strained and the albedo will be determined thus allowing to characterize its surface. Title: The sizes, shapes, albedos, and colors of cometary nuclei Authors: Lamy, P. L.; Toth, I.; Fernandez, Y. R.; Weaver, H. A. Bibcode: 2004come.book..223L Altcode: We critically review the data on the sizes, shapes, albedos, and colors of cometary nuclei. Reliable sizes have been determined for 65 ecliptic comets (ECs) and 13 nearly isotropic comets (NICs). The effective radii fall in the range 0.2-15 km for the ECs and 1.6-37 km for the NICs. We note that several nuclei recently measured by the Hubble Space Telescope are subkilometer in radius, and that only 5 of the 65 well-measured EC nuclei have effective radii larger than 5 km. We estimate that the cumulative size distribution (CSD) of the ECs obeys a single power law with an exponent qS = 1.9 ± 0.3 down to a radius of ~1.6 km. Below this value there is an apparent deficiency of nuclei, possibly owing to observational bias and/or mass loss. When augmented by 21 near-Earth objects (NEOs) that are thought to be extinct ECs, the CSD flattens to qS = 1.6 ± 0.2. The cumulative size distribution of NICs remains ill-defined because of the limited statistical basis compared to ECs. The axial ratios a/b of the measured nuclei of ECs have a median value of ~1.5 and rarely exceed a value of 2, although it must be noted that the observed a/b values are often lower limits because of uncertainties in the aspect angle. The range of rotational periods extends from 5 to 70 h. The lower limit is significantly larger than that of main-belt asteroids and NEOs (~2.2 h, excluding the monolithic fast rotators), and this has implications for the bulk density of cometary nuclei. By combining rotation and shape data when available, we find a lower limit of 0.6 g cm-3 for the nucleus bulk density to ensure stability against centrifugal disruption. Cometary nuclei are very dark objects with globally averaged albedos falling within a very restricted range: 0.02-0.06, and possibly even narrower. (B-V), (V-R), and (R-I) color indices indicate that, on average, the color of cometary nuclei is redder than the color of the Sun. There is, however, a large diversity of colors, ranging from slightly blue to very red. While two comets have well-characterized phase functions with a slope of 0.04 mag deg-1, there is evidence for steeper (2P/Encke, 48P/Johnson) and shallower (28P/Neujmin 1) functions, so that the observed range is 0.025-0.06 mag deg-1. The study of the physical properties of cometary nuclei is still in its infancy, with many unresolved issues, but significant progress is expected in the near future from current and new facilities, both groundbased and spaceborne. Title: Solar Cycle Variation of the Radiance and the Global Electronic Content of the Solar Corona Authors: Lamy, P.; Llebaria, A.; Quemerais, E. Bibcode: 2004cosp...35.1876L Altcode: 2004cosp.meet.1876L The question of the global activity of the solar corona, as a function of time and distance from the center of the Sun, is considered by analyzing SOHO/LASCO-C2 images over more than eight years, thus covering a large part of solar cycle 23. The polarized images are first analyzed to construct a photometric model of the F-corona wich reflects its annual variations resulting from geometric effects and of the instrumental straylight. Synoptic maps of the radiance of the K-corona are created at different distances between 2.7 and 6.5 solar radii. In order to conveniently quantify its temporal variation, the radiance is integrated first globally and then in zones of different latitudes to separate the equatorial and the polar regions. A similar analysis is performed with the electronic density obtained by the inversion of the polarized brightness assuming either a spherical or a cylindrical model of the corona. Both the radiance and the electronic density strongly vary with solar activity but the equatorial and polar regions exhibit different behaviours. These variations are compared with other indices of solar activity. Title: Dust Near The Sun Authors: Mann, Ingrid; Kimura, Hiroshi; Biesecker, Douglas A.; Tsurutani, Bruce T.; Grün, Eberhard; McKibben, R. Bruce; Liou, Jer-Chyi; MacQueen, Robert M.; Mukai, Tadashi; Guhathakurta, Madhulika; Lamy, Philippe Bibcode: 2004SSRv..110..269M Altcode: We review the current knowledge and understanding of dust in the inner solar system. The major sources of the dust population in the inner solar system are comets and asteroids, but the relative contributions of these sources are not quantified. The production processes inward from 1 AU are: Poynting-Robertson deceleration of particles outside of 1 AU, fragmentation into dust due to particle-particle collisions, and direct dust production from comets. The loss processes are: dust collisional fragmentation, sublimation, radiation pressure acceleration, sputtering, and rotational bursting. These loss processes as well as dust surface processes release dust compounds in the ambient interplanetary medium. Between 1 and 0.1 AU the dust number densities and fluxes can be described by inward extrapolation of 1 AU measurements, assuming radial dependences that describe particles in close to circular orbits. Observations have confirmed the general accuracy of these assumptions for regions within 30° latitude of the ecliptic plane. The dust densities are considerably lower above the solar poles but Lorentz forces can lift particles of sizes < 5 μm to high latitudes and produce a random distribution of small grains that varies with the solar magnetic field. Also long-period comets are a source of out-of-ecliptic particles. Under present conditions no prominent dust ring exists near the Sun. We discuss the recent observations of sungrazing comets. Future in-situ experiments should measure the complex dynamics of small dust particles, identify the contribution of cometary dust to the inner-solar-system dust cloud, and determine dust interactions in the ambient interplanetary medium. The combination of in-situ dust measurements with particle and field measurements is recommended. Title: Properties of the nuclei of Centaurs Chiron and Chariklo Authors: Groussin, O.; Lamy, P.; Jorda, L. Bibcode: 2004A&A...413.1163G Altcode: We analyze visible, infrared, radio and spectroscopic observations of 2060 Chiron in a synthetic way to determine the physical properties of its nucleus. From visible observations performed from 1969 to 2001, we determine an absolute V magnitude for the nucleus of 7.28±0.08 with an amplitude of 0.16±0.03, implying a nearly spherical nucleus with a ratio of semi-axes a/b=1.16±0.03. Infrared observations at 25, 60, 100 and 160 μm (i.e., covering the broad maximum of the spectral energy distribution) obtained with the Infrared Space Observatory Photometer (ISOPHOT) in June 1996 when Chiron was near its perihelion are analyzed with a thermal model which considers an intimate mixture of water ice and refractory materials and includes heat conduction into the interior of the nucleus. We find a very low thermal inertia of 3+5-3 J K-1 m-2 s-1/2 and a radius of 71±5 km. Combining the visible and infrared observations, we derive a geometric albedo of 0.11±0.02. We find that the observed spectra of Chiron can be fitted by a mixture of water ice (∼30%) and refractory (∼ 70%) grains, and that this surface model has a geometric albedo consistent with the above value. We also analyze the visible, infrared and radio observations of Chariklo (1997 CU26) and derive a radius of 118±6 km, a geometric albedo of 0.07±0.01 and a thermal inertia of 0+2-0 J K-1 m-2 s-1/2. A mixture of water ice (∼ 20%) and refractory (∼ 80%) grains is compatible with the near-infrared spectrum and the above albedo. Title: Rotational Properties of Deep Impact Target Comet 9P/Tempel 1 Authors: Lisse, C. M.; Groussin, O.; A'Hearn, M. F.; Weaver, H. A.; Lamy, P.; Meech, K. J.; Belton, M. J. S.; Fernandez, Y. R.; Toth, I. Bibcode: 2004cosp...35.3161L Altcode: 2004cosp.meet.3161L Comet 9P/Tempel 1 is the target of the Deep Impact mission to be launched at the end of this year. To improve our understanding of the rotational properties of the Tempel 1 nucleus [e.g., the current rotational period solutions are 22 and 42 hours with an axial ratio > 2.5 :1 (Belton and Meech, 2004)], we performed 12 spectroscopic (7.5-40 microns) observations of the nucleus with the Spitzer Space Telescope over a 42 hour period in March 2004, and 18 photometric (F606) observations over a 42 hour period in May 2004 with the Hubble Space Telescope. Ground based optical observations of the lightcurve were also obtained during these times, in order to establish the albedo and inter-phase the results. We present here the lightcurve results, and the most likely solution for the rotational periodicity. We also discuss the axial ratio of the body as estimated from the lightcurve amplitudes. Title: Visible and thermal infrared observations of the nucleus of comet 67P/Churyumov-Gerasimenko Authors: Lamy, P. L.; Jorda, L.; Toth, I.; Weaver, H. A.; Cruikshank, D.; Fernandez, Y. Bibcode: 2004cosp...35.1824L Altcode: 2004cosp.meet.1824L The nucleus of comet 67P/Churyumov-Gerasimenko was first unambiguously detected in the visible with the planetary camera of the Hubble Space Telescope in early March 2003 (Lamy, P.L. et al., BAAS 35, 970). By observing the comet over 21 hours, the rotational period was found to be 12.3 hr and assuming an albedo of 0.04, a radius of 2 km was determined. It will be further observed in the thermal infrared with the Spitzer Space Telescope in late February 2004 at a heliocentric distance of 4.5 AU where it is presumed to be inactive. The nucleus will be imaged with the multiband imaging photometer (MIPS) at 24 microns seventeen times, over a time interval of 12.5 hr to as to cover the full light curve. The infared flux will give directly access to its size. By further combining with past HST observations, the rotational state of the nucleus will be better constrained and the albedo will be determined thus allowing to characterize its surface. Title: Approach to 3-D reconstruction of the solar corona from STEREO observations Authors: Portier-Fozzani, F.; Lamy, P.; Llebaria, A. Bibcode: 2004cosp...35.3977P Altcode: 2004cosp.meet.3977P In this poster, we present the work that we planned to do at the Laboratoire d'Astrophysique de Marseille concerning 3D reconstructions for the mission STEREO. Getting 3D informations from a large images database could be sometimes very puzzling while it requires 3D inversions together with image analysis decomposition. From coronagraphic data, Vibert et al., 1997, used octree methods to rebuilt the neutral sheet of the solar corona. The octree method helps to reorganize a large number of data to be used by tomographic method. More recently, Portier-Fozzani and Inhester (SOLSPA 2001) proposed to reconstruct the solar corona in EUV by stereoscopic methods in using the solar cycle for improving the decomposition into structures to reconstruct. Portier-Fozzani, Bijaoui et al. (2002, 2004) used the Multiscale Vision Model based on spatial wavelets decomposition, to define in their image pair, groups of sub-objects, which are needed for the matching step in stereovision. We derive here how we can use these approaches for a full automatic reconstruction depending of the solar cycle. Title: Three-dimensional Model of the Streamer Belt over Solar Cycle 23 Authors: Saez, F.; Llebaria, A.; Lamy, P. Bibcode: 2004cosp...35.1854S Altcode: 2004cosp.meet.1854S White-light images of the corona obtained with the SOHO/LASCO-C2 coronagraph over more than 8 years reveal the dramatic changes of the structure and radiance distribution of the streamer belt from the minimum to the maximum of the present solar cycle. While it is qualitatively understood that the widening of the belt is a consequence of the tilting and warpening of the plasma current sheet, no quantitative study has been performed to derive physical parameters from these images. Our approach consists in reproducing the widening of the streamer belt and its periodic evolution with the solar rotation with a model combining a layer of plasma centered around the heliospheric current sheet and isolated streamers associated to active regions. We first determine the neutral sheet from solar photospheric magnetograms. Next, we introduce a parametric description of the electronic density in streamers and construct its octree representation based on a non-uniform sampling of the 3D space. The synthesized images are generated using a ray-tracing algorithm which calculates the Thomson scattering through the octree. Finally, we present a method that allows to simulate the time evolution of the coronal magnetic field during a Carrington rotation. The comparaison between the model and the LASCO-C2 observations is performed on synoptic maps, to offer a global view of the evolution of the corona, and on radiance profiles to assess the quantitative agreement. Title: The SIde-Looking Coronagraph (SILC) for the Solar Orbiter mission Authors: Vives, S.; Lamy, P.; Korendyke, C. Bibcode: 2004cosp...35..951V Altcode: 2004cosp.meet..951V The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing instruments proposed for the payload of the Solar Orbiter mission (European Space Agency, ESA). The Solar Orbiter will describe elliptic orbits with a large range of heliocentric distance, from 0.21 to 0.6 AU, that is a factor 3 for the geometric conditions, and will reach heliographic latitudes as high as 38 degrees. Furthermore, the spacecraft will have offset pointing capability so as to target any point of the solar disk. These specificities (in addition to the severe thermal environment) are very restrictive for a coronagraph and lead us to propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally-occulted coronagraph adapted to the side-looking concept. Although SILC loses the full spatial coverage of the corona, it can observe the inner part of the corona (down to 1.5 solar radii) during the whole mission and compensate the off-pointing of the spacecraft in the two directions. The performances, resulting from ray-tracing calculations, will be presented together with the first measurements of the stray light level. Title: Activity on the surface of the nucleus of comet 46P/Wirtanen Authors: Groussin, O.; Lamy, P. Bibcode: 2003A&A...412..879G Altcode: We present a thermal model of the nucleus of comet 46P/Wirtanen, constrained by the temporal variations of the water production rate, in order to understand the activity on its surface. We consider a spherical nucleus with a macroscopic mosaic of small and numerous active and inactive regions. At heliocentric distances rh > 1.5 AU, the active regions represent 5-15% of the surface. At ~ 1.5 AU, a rapid increase takes place and the active fraction reaches 70 to 100% in about 10 days, and then remains approximately constant up to perihelion where QH_2O=1.3+/-0.3*E28 molecule s-1. Post-perihelion, this fraction returns to ~ 10%. The model is consistent with a geometric albedo <=0.06. A refractory crust likely forms post-perihelion and can explain the variations of the activity over an orbit. Finally, we derived an erosion of ~ 0.5 m per revolution and a remaining lifetime for the nucleus of several hundred revolutions. Title: Long term evolution of cometary nuclei - Application to 46P/Wirtanen Authors: Groussin, O.; Lamy, P.; Valsecchi, G.; Gonczi, R. Bibcode: 2003DPS....35.3828G Altcode: 2003BAAS...35Q1488G We present a new method to study the long term evolution of cometary nuclei in order to retrieve their original size. We consider first the case of comet 46P/Wirtanen (the former target of the Rosetta mission) and we calculate the past evolution of its orbital elements over 105 years, with and without non-gravitational forces. The chaotic behaviour is simulated by considering 9 different values of the initial mean anomaly. For an homogeneous nucleus with a composition of 50% water ice + 50% dust and a density of 500 kg/m3, we obtain an initial radius in the range 1.4-7.8 km, depending upon the inital conditions. This result also depends upon the composition and the density, but not on the presence, or not, of the non-gravitational forces. We will apply this method to many other cometary nuclei in the future. Title: LASCO C2 and C3 Level-1 Images: Calibration and Pipeline Processing Authors: Thernisien, A. F.; Morrill, J.; Llebaria, A.; Rich, N.; Vourlidas, A.; Esfandiari, E.; Wang, D.; Korendyke, C.; Moses, D.; Biesecker, D.; Bout, M.; Lamy, P.; Howard, R. A. Bibcode: 2003AGUFMSH41B0461T Altcode: The LASCO C2 and C3 coronagraphs have provided coronal observations since May, 1996. Initial calibrations have been available during most of this time period. We have subsequently completed a re-evaluation and refinement of these calibration procedures. We are now able to present the final version of the level-1 data using the latest improvements from in-flight calibration results. Further details on the LASCO calibration and level-1 data access are presented at http://lasco-www.nrl.navy.mil/level_1/lascocal_index.html. In this presentation we will sum up the different aspects of the LASCO C2-C3 image corrections such as vignetting, absolute photometry, time corrections, geometric distortion, sun center position, and spacecraft orientation. Title: New spin period determination for comet 6P/d'Arrest Authors: Gutiérrez, P. J.; de León, J.; Jorda, L.; Licandro, J.; Lara, L. M.; Lamy, P. Bibcode: 2003A&A...407L..37G Altcode: A lightcurve of comet 6P/d'Arrest from R-band CCD images taken at La Palma 2.52 m NOT telescope is presented. The lightcurve shows noticeable periodic changes in brightness produced by rotational modulation. The periodogram analysis of the lightcurve shows a peak with a confidence level exceeding 99.9% at 3.336 h. Assuming an elongated nucleus, the most likely spin period is therefore 6.67 +/- 0.03 h, but other periodicities are also possible. The peak to peak amplitude is 0.082 +/- 0.016 mag. This period, and the other peaks detected in the periodogram, are not commensurable with previous estimates of the spin period of comet 6P/d'Arrest. If all the measurements are correct, the differences between this estimate and the previous ones could be due to a possible change in the spin period of comet 6P/d'Arrest or to this comet being rotating in a complex mode. Title: Outgassing-induced effects in the rotational state of comet 67P/Churyumov-Gerasimenko during the Rosetta mission. Authors: Gutierrez, P. J.; Jorda, L.; Samarasinha, N. H.; Lamy, P. Bibcode: 2003DPS....35.3802G Altcode: 2003BAAS...35..984G Comet 67P/Churyumov-Gerasimenko [hereafter 67P/C-G] is the new main target of the Rosetta mission (a cornerstone mission in ESA's "Horizon 2000" program). The Rosetta spacecraft will orbit comet 67P/C-G for almost one year in 2015, and a module will land on its surface. In order to ensure the correct interpretation of the measurements taken by the instruments onboard the spacecraft and to help in the definition of an appropriate landing strategy, we carry out numerical simulations of the evolution of the rotational state of this comet under the effects of the sublimation-induced torque from the currrent epoch to the end of the Rosetta mission. In the simulations, we will take into account the known observational constraints on the nucleus size and the spin period and consider a range of scenarios: two thermophysical models, several densities, three initial angular momentum orientations, several activity patterns on the surface, and two initial rotational states. We will present our initial results including the typical changes in the angular momentum orientation and the spin period during the operational phase. Title: SOHO/LASCO observation of an outburst of Comet 2P/Encke at its 2000 perihelion passage Authors: Lamy, P.; Biesecker, D. A.; Groussin, O. Bibcode: 2003Icar..163..142L Altcode: Comet 2P/Encke was observed with the SOHO/LASCO C2 and C3 coronagraphs over a time interval of 11 days, starting 4 days before its September 2000 perihelion passage and through several broadband visible filters. The lightcurve reveals an outburst which started 4.9 days after perihelion, with the brightness of the coma increasing by 1.5 mag in just a few hours and progressively decreasing thereafter, probably going back to its original state in about 9 days. The color information indicates that an approximately solar color continuum was detected, implying that the observed signals were dominated by solar light scattered off submillimetric dust grains. We propose that the rapid migration of the subsolar point over the southern hemisphere during the perihelion passage activates one or several new active regions enriched in submillimetric grains, with the observed outburst corresponding to the initial blow-off of their mantle. This scenario is consistent with other observations and implies that the south polar region of the nucleus of 2P/Encke has very distinct properties. Title: New Modeling of Cometary Dust Tails Authors: Jorda, L.; Lamy, P. L.; Coliac, J. -F.; Bout, M.; Colas, F.; Lecacheux, J.; Rauer, H.; Weiler, M. Bibcode: 2003DPS....35.3820J Altcode: 2003BAAS...35R.988J We present a technique for modeling cometary dust tails. The technique is based on Monte Carlo simulations of a large number of ``model-images'', recombined linearly to fit the observed CCD image of the dust tail. In essence, our technique is similar (but not identical) to that originally proposed by Kimura and Liu (1975, 1982) and developed by Fulle (1987, 1989), but incorporates new features such as the rigorous calculation of the light scattered by the dust grains. It can be used to interactively retrieve the dust size and velocity distributions and to compute the dust production rate. We present the application of this technique to comet 67P/Churyumov-Gerasimenko, the new target of ESA's Rosetta mission and to comets observed with the SOHO/LASCO coronagraphs (C/1996 B2 Hyakutake, C/2002 S2 SOHO 517, C2002 X5 Kudo-Fujikawa, C2002 V1 NEAT and 96P/Machholz 1).

-- Fulle, M., A&A 171, 327, 1987.

-- Fulle, M., A&A 217, 283, 1989.

-- Kimura, H., and Liu, C.-P., AcASn 16, 138, 1975.

-- Kimura, H., and Liu, C.-P., AcASn 23, 232, 1982. Title: The Nucleus of Comet 67P/Churyumov-Gerasimenko, the New Target of the Rosetta Mission Authors: Lamy, P. L.; Toth, I.; Weaver, H.; Jorda, L.; Kaasalainen, M. Bibcode: 2003DPS....35.3004L Altcode: 2003BAAS...35..970L We report the detection of the nucleus of comet 67P/Churyumov-Gerasimenko, the new target of the Rosetta mission, with the Planetary Camera (WFPC2) of the Hubble Space Telescope (HST). The observations were performed between 11.4 and 12.3 March 2003 (i.e., a time interval of 21 hr) when the comet was at heliocentric and geocentric distances of respectively 2.51 and 1.53 AU and at a phase angle of 4.8 deg. The high spatial resolution (a WFPC2 pixel projected to 50 km at the distance of the comet) insured a very large contrast of the nucleus over its surrounding coma, reaching a factor of typically 30 in the peak pixels. The 61 images allowed us to determine 49 R magnitudes and 12 V magnitudes of the nucleus. Assuming a spherical body with a geometric albedo of 0.04 and a phase coefficient of 0.04 mag/deg, we derived an effective radius of 1.98 +/- 0.02 km. The lightcurve data were analyzed using both the PDM (Phase Dispersion Minimization) and the Fourier technics. Assuming a classical double peak lightcurve, the two technics give the same rotational period of P=12.3 +/- 0.27 hr. This result is highly robust since the probability that the period detection with the PDM technics is due to random noise amounts to only 3E-11. The lightcurve which conspicuously deviates from a sinusoide with shallow minima and narrow, unequal maxima, was inverted in order to model the 3-dimensional shape of the nucleus using the method developed by Kaasalainen et al. (Icarus 153, 37, 2001). The rotational state is constrained to be close to principal axis rotation of maximum inertia to get physically consistent solutions. All plausible solutions share the same qualitative global shape characteristics. The model which best fits the observed lightcurve (rms deviation of 0.028 mag) has a rotation axis tilted by about 8 deg from the principal axis, a rotational period of 12.69 +/-0.10 hr, an aspect angle of 90 +/- 20 deg (i.e., equatorial view) and a slightly rugged shape. The color of the nucleus is moderately red with a color index V-R = 0.51, the most common value among cometary nuclei. The OH production rates impose a rather low active fraction at perihelion, 4% to 7%. The activity is thus limited to probably a few, very small areas, consistent with the detection of several jets in the coma. The dust production rate was characterized by Afρ = 40 cm.

We thank S. Beckwith for granting us HST Director's Discretionary time on a very short notice. This work was supported by grants from CNRS and CNES, and from NASA to H. W. Title: Hubble Space Telescope Observations of the Nucleus Fragment 73P/Schwassmann-Wachmann 3-B Authors: Toth, I.; Lamy, P. L.; Weaver, H. A. Bibcode: 2003DPS....35.3805T Altcode: 2003BAAS...35..985T The nucleus of 73P/Schwassmann-Wachmann 3 (73P/SW3), a Jupiter-Family comet, has non-tidally broken into at least three components A, B and C, in autumn 1995. Fragment B was detected with the Planetary Camera 2 of the Hubble Space Telescope on 26 November 2001. i.e., after the comet's perihelion passage on 27.9 January 2001, when it was at 3.25 AU from the Sun, 2.33 AU from the Earth, and at a solar phase angle of 7.4o. The high spatial resolution of the PC2 allowed to separate the signal of the faint nucleus fragment from that of its active coma, and we measured its R magnitude from our images taken with the F675W filter. Assuming a spherical body whose geometric albedo is 0.04 and a linear phase coefficient of 0.04 mag/deg for the R band, we derived an effective radius of 0.68+/-0.04 km. The short time span of our HST observations did not allow to determine its shape but the lower limit of its axial ratio a/b (assuming a prolate spheroid) is ∼1.16. From the pre-breakup radius of the original nucleus of 1.3 km determined by Boehnhardt et al. (2002: EMPl 90, 131), we found that the fractional volume of fragment B is about 14%. Its size of a few hundred meters, typical of fragments of other split comets, is probably too large for a primordial building block and indicate that it still is a conglomerate; further disintegration of this fragment remains possible. Its level of activity is remarkably high in spite of a heliocentric distance of ∼3.2 AU, just beyond the limit for sublimation of water ice (2.8 AU). We measured an Afρ of 19.6-23.2 cm but the determination of a dust production rate is precluded by the absence of gas production rates at the time of our observation. Ground-based observations performed in 2001 by Boehnhardt et al. (2002: EMPl 90, 131) indicate that another fragment (E) has already disappeared, and we conclude that this may well be short-term fate of fragment B as it may not survive its next perihelion passage in 2006. The tau-Herculids meteor swarm associated to 73P/SW3 will likely experience an increase of activity.

This work was supported by the CNRS, CNES, and Université de Provence, France, and by the Hungarian Academy of Science through grant No. 9871. Title: SOHO/LASCO Observation of Comet C/2002 X5 Kudo-Fujikawa at its 2003 Perihelion Passage Authors: Bout, M. V.; Lamy, P. L.; Llebaria, A. Bibcode: 2003DPS....35.3821B Altcode: 2003BAAS...35..988B Comet C/2002 X5 Kudo-Fujikawa was observed with the SOHO/LASCO C2 and C3 coronagraphs over a time interval of 7 days, starting 4 days before its 29 January 2003 perihelion passage and through several broadband visible filters. A total of 134 images were obtained with the C3 clear filter, 51 images with the C2 orange filter completed by 20 color sequences. The lightcurves reveal that the brightness of the coma steeply increased to reach local maxima on 27 January, then suffered a drastic turnover, decreasing by about 0.8 mag to reach minimum values on 27.8, then increased again to reach absolute maxima slightly before perihelion passage and finally decreased. This pattern of activity is consistent with the apparition of a new, anti-solar dust tail widely separated from the main tail that the comet originally sported. This translates in an unusual butterfly pattern where two "decoupled" tails co-exist at the same time. Short-time variations in the lightcurves may be caused by the rotation of the nucleus, suggesting a rotation period of about 4 hours. Title: The solar high-resolution imager - coronagraph LYOT mission Authors: Vial, Jean-Claude; Song, Xueyan; Lemaire, Philippe; Gabriel, Alan H.; Delaboudiniere, Jean-Pierre; Bocchialini, Karine; Koutchmy, Serge L.; Lamy, Philippe L.; Mercier, Raymond; Ravet, Marie Francoise; Auchere, Frederic Bibcode: 2003SPIE.4853..479V Altcode: The LYOT (LYman Orbiting Telescope) solar mission is proposed to be implemented on a micro-satellite of CNES (France) under phase A study. It includes two main instruments, which image the solar disk and the low corona up to 2.5 Ro in the H I Lyman-α line at 121.6 nm. The spatial resolution is about 1” for the disk and 2.5” for corona. It also carries an EIT-type telescope in the He II (30.4 nm) line. The coronagraph needs a super polished mirror at the entrance pupil to minimize the light scattering. Gratings and optical filters are used to select the Lyman-α wavelength. VUV cameras with 2048×2048 pixels record solar images up to every 10 seconds. The satellite operates at a high telemetry rate (more then 100 kb/s, after onboard data compression). The envisaged orbits are either geostationary or heliosynchronous. Possible launch dates could be end of 2006 - beginning of 2007. Title: Commission 21: Light of the night sky (Lumière du ciel nocturne) Authors: Lamy, Philippe Bibcode: 2003IAUTA..25..199L Altcode: 2003IAUTr..25A.199L No abstract at ADS Title: Two-dimensional electron density in the solar corona from inversion of white light images - Application to SOHO/LASCO-C2 observations Authors: Quémerais, E.; Lamy, P. Bibcode: 2002A&A...393..295Q Altcode: We present here the inversion method which has been developed to derive the electron density in the Solar Corona from LASCO-C2 white light images. We discuss how our inversion scheme can be applied either to images of polarized brightness of the corona or images of total brightness after removal of the dust and stray light components. The outputs from both schemes are compared. For the inversion of two-dimensional images of the solar corona, it is necessary to assume a global geometry for the electron density. We compare results obtained for spherical and axi-symmetric geometries. Finally, our results for December 1996 are compared to previous derivations of the electron radial density profiles obtained by other measurements. Title: The Study of Comets Authors: Combi, M. R.; Capria, M. T.; Cremonese, G.; de Sanctis, M. C.; Farnham, T. L.; Fernandez, Y. R.; Festou, M. C.; Fink, U.; Green, J. R.; Harris, W. M.; Hergenrother, C. W.; Lamy, P. L.; Larson, S. M.; Levison, H. F.; Lien, D. J.; Lisse, C. M.; Meisel, D. D.; Moehlmann, D. T. F.; Mueller, B. E. A.; Samarasinha, N. H.; Sitko, M. L.; Weaver, H. A.; Weissman, P. R. Bibcode: 2002ASPC..272..323C Altcode: 2002fsse.conf..323C The study of comets is critical to our understanding the origin, structure and evolution of the solar system in general and of life itself. We present here a brief summary of our current understanding of comets and their important place in the solar system, as well as our recommendations regarding priorities for their study over the next decade in the context of a coordinated program of spacecraft missions and ground-based and theoretical investigations. Title: Sungrazing Comets Discovered with the SOHO/LASCO Coronagraphs 1996-1998 Authors: Biesecker, D. A.; Lamy, P.; St. Cyr, O. C.; Llebaria, A.; Howard, R. A. Bibcode: 2002Icar..157..323B Altcode: The Kreutz sungrazing family of comets is unique because of its small perihelion distance and because of the large number of known members of this family. SOHO/LASCO coronagraph observations beginning in 1996 have revealed an unprecedented number of Kreutz comets. These new coronagraph observations improve upon earlier observations because of a larger field-of-view, increased image cadence, and better photometric measurements. This paper presents the lightcurves of the 141 Kreutz family comets observed from 1996 through 1998. Throughout this period, the number of family members discovered each year is shown to be constant. None of the comets were detected postperihelion. The lightcurves show distinctive characteristics which reveal much about the properties of the nuclei. It is shown that the individual fragments can be related to one of two “standard candles,” which we call Universal Curves. The comets all reach a peak brightness at one of two characteristic distances (both near 12 R⊙) and that the comets fragment at another characteristic distance (about 7 R⊙). Also, evidence is seen for line emission, which varies with heliocentric distance. Title: The fractal nature of the polar plumes Authors: Llebaria, A.; Saez, F.; Lamy, P. Bibcode: 2002ESASP.508..391L Altcode: 2002soho...11..391L Polar plumes are often perceived as isolated structures, possibly tube-like, in super-radial expansion. As a consequence, coronal holes are considered composed of plumes and dominating inter-plume regions from which the fast solar wind originates. In order to test the validity of this concept, we pursued the analysis of a sequence of high cadence continuous observations obtained with the SOHO/LASCO-C2 coronagraph in March 1997. The spectral analysis of the plume pattern show that their spatial distribution is of fractal type. This implies that their distribution in a surface section of the coronal hole is self-affine and that coronal holes have a fibrous structure, at least at the spatial scales of the visible observations. Title: Electron density in coronal jets Authors: Bout, M.; Lamy, P.; Llebaria, A. Bibcode: 2002ESASP.508..379B Altcode: 2002soho...11..379B Coronal jets are observed by the SOHO/LASCO C2 and C3 coronagraphs as thin, highly collimated structures. The determination of their electron density cannot be performed with the standard inversion of pB images because of the inherent assumption of global spherical or axial symmetry of the corona which is totally inappropriate in the case of local structures. Our analysis first isolates the jets by subtracting the background corona. Their radiance is then compared to calculated models which assume a tube like structure. This allows to derive the true radial profile of their electron density. Title: Calibration of the LASCO C3 Coronal Images Authors: Morrill, J.; Biesecker, D.; Esfandiari, A.; Korendyke, C.; Moses, D.; Rich, N.; Vourlidas, A.; Wang, D.; Howard, R. A.; Lamy, P.; Llebaria, A.; Thernisien, A. Bibcode: 2002AAS...200.5503M Altcode: 2002BAAS...34R.732M The LASCO C3 coronagraph has provided coronal observations since May, 1996. Preliminary calibrations have been available during most of this time period. However, some aspects of the calibration have required re-evaluation and we are just completing a complete review of the calibration procedure for these images. In this presentation we will discuss the steps required to correct LASCO C3 images. This includes corrections required by both optical and electrical characteristics of the instrument as well as timimg and spacecraft pointing driven correctons. Title: The Nucleus of Comet 22P/Kopff and Its Inner Coma Authors: Lamy, P. L.; Toth, I.; Jorda, L.; Groussin, O.; A'Hearn, M. F.; Weaver, H. A. Bibcode: 2002Icar..156..442L Altcode: We report the detection of the nucleus of Comet 22P/Kopff with the Planetary Camera of the Hubble Space Telescope (HST) and with the Infrared Camera of the Infrared Space Observatory (ISOCAM). The HST observations were performed on 18 July 1996, 16 days after its perihelion passage of 2 July 1996, when it was at Rh=1.59 AU from the Sun and Δ=0.57 AU from the Earth. A sequence of images taken with four broad-band filters was repeated eight times over a 12-h time interval. The ISOCAM observations were performed on 15 October 1996, 106 days after the perihelion passage, when the comet was at Rh=1.89 AU from the Sun and Δ=1.32 AU from the Earth. Seven images were obtained with a broad-band filter centered at 11.5 μm. In both instances, the spatial resolution was appropriate to separate the signal of the nucleus from that of the coma. We determine the Johnson-Kron-Cousins BVRI magnitudes of the nucleus. The visible lightcurves constrain neither the rotation period nor the ratio of semiaxes. We favor the solution of a rather spherical nucleus, although the situation of a pole-on view of an irregular body cannot be excluded. The systematic decreasing trend of the lightcurves could suggest a period of several days. Combining the visible and infrared observations, we find that an ice-dust mixed model is ruled out, while the standard thermal model leads to a nuclear radius of Rn=1.67±0.18 km of albedo pv=0.042±0.006. The red color of the nucleus is characterized by a nearly constant gradient of S'=14±5% per kÅ from 400 to 800 nm. We estimate a fractional active area of 0.35 which places 22P/Kopff in the class of highly active short-period comets. At Rh=1.59 AU, the dust coma is characterized by a red color with a reflectivity gradient S'=17±3% per kÅ, compatible with that of the nucleus, and Afρ=545 cm, yielding a dust production rate of Qd=130 kg sec -1. Title: New insights on the onsets of coronal mass ejections from soho Authors: Plunkett, S. P.; Michels, D. J.; Howard, R. A.; Brueckner, G. E.; St. Cyr, O. C.; Thompson, B. J.; Simnett, G. M.; Schwenn, R.; Lamy, P. Bibcode: 2002AdSpR..29.1473P Altcode: Coronal mass ejections (CMES) are among the most dramatic forms of transient activity occurring in the solar atmosphere. Despite over twenty years of research, many basic questions related to the physics of CMEs have remained unanswered. Observations with the LASCO and EIT experiments on SOHO, combined with recent theoretical modeling, have provided new insights on some of these outstanding questions and have also raised many new ones that need to be addressed in the future. In this paper, we present some of the new results from SOHO pertaining to the source regions and onsets of CMEs, and their evolution in the corona. We emphasize the important role that studies of CMEs will play in the International Solar Cycle Studies program. Title: New Modeling of 19P/Borrelly s Spin State Authors: Jorda, L.; Gutierrez, P.; Lamy, P. Bibcode: 2002cosp...34E3221J Altcode: 2002cosp.meetE3221J Comet 19P/Borrelly has been imaged by the Deep Space 1 (DS1) spacecraft in Sept. 2001. The images allowed the retrieval of the size and shape of the comet nucleus with a high accuracy. The spin orientation of this comet has also been derived from the DS1 MICAS images and from ground-based observations obtained during the last decades. We will present here new modeling of the temporal evolution of the spin state of comet 19P/Borrelly using these new observational constraints. Title: Solar cycle variation of the radiance and the global electron density of the solar corona Authors: Lamy, P.; Llebaria, A.; Quemerais, E. Bibcode: 2002AdSpR..29..373L Altcode: The question of the global activity of the solar corona, as a function of time and distance from the center of the Sun, is considered by analyzing SOHO/LASCO-C2 daily polarized images over four years, i.e., from the minimum to the rising phase of the 23rd solar cycle. After proper correction for instrumental polarization, they are combined to produce maps of the polarized radiance pB and of the radiance of the K-corona (assuming a model for the K-corona polarization p K). The electron density is obtained by inversion of the pB images assuming local spherical symmetry. Synoptic maps are created at four distances between 2.7 and 5.5 solar radii. In order to conveniently quantify their temporal variation, the polarized radiance, the radiance and the electron density are integrated first globally and then in zones of different latitudes to separate the equatorial and the polar regions. These integrals remained constant in 1996 and then progressively increased with the rising activity of the Sun. However the polar and equatorial regions exhibited different behaviours as the former remained stable over a much longer time interval and experienced a larger increase than the latter. Title: Characterization of coronal streamers from LASCO-C2 observations and implications for the slow solar wind Authors: Lamy, P.; Bout, M.; Llebaria, A.; Thernisien, A. Bibcode: 2002cosp...34E1507L Altcode: 2002cosp.meetE1507L Recent analysis of LASCO images of the corona obtained during the rising phase of the present solar cycle indicates that there exists streamers distinct from the classical streamer belt which results from line-of-sight integration through folds in a warped current sheet (Liewer et al., 2001, JGR 106, A8, 15903). These "isolated" streamers are the result of scattering from regions of enhanced density associated with active region outflow. A preliminary quantitative analysis of LASCO-C2 images of several such structures indicates enhancement factors as large as 50 compared to the classical model of Van de Hulst (Bout et al., 2002, SOHO-11 Conference). We will report on further progress in analyzing these streamers and our attempt to measure outflow speeds. Our ultimate purpose is to assess the contribution of these structures to the slow solar wind. Title: The Properties of Sun-grazing Comets Authors: Lamy, P.; Biesecker, D. Bibcode: 2002cosp...34E3159L Altcode: 2002cosp.meetE3159L Over 450 sun -grazing comets have now been detected with the Large Angle Spectroscopic Coronagraphs (LASCO) on the Solar and Heliospheric Observatory (SOHO). The bulk of them belong to the Kreutz family while 49 are either scattered or belong to other families. In this review, we first consider the statistical properties of the distribution of the orbital elements to establish the reality of sub-groups and to characterize the process of their fragmentation. We then analyze the light curves and confront the different observed behavior with the dynamical families. For a few comets, color information is available and helps to characterize the sun-grazers. Title: Characterization of the polar plumes from high cadence LASCO-C2 observations Authors: Llebaria, A.; Thernisien, A.; Lamy, P. Bibcode: 2002AdSpR..29..343L Altcode: In order to understand the spatio-temporal characteristics of polar plumes, we analyzed a sequence of continuous observations obtained with the SOHO/LASCO-C2 coronagraph over a period of 3 days with a time resolution of 10 minutes. We generated the time intensity diagram (TID) where the radiance of the plumes is displayed as a function of their angular positions and time. The derivatives of the TID with respect to the phase angle on the one hand and to time on the other hand allow us to define the trajectories of individual plumes and their temporal variations. This confirms that polar plumes are enduring structures that are only transiently lit, as we found before, but the present analysis reveals that the blinking takes place on time scales as short as 2 hours. This is confirmed by the radial intensity diagrams (RID) which track each individual plume by displaying its radiance as a function of time and distance. These diagrams also indicate a constant speed of expansion with a mean value of 460 km/sec. Title: Properties of the surface of 46P/Wirtanen from the observed water production rate Authors: Groussin, O.; Lamy, P. Bibcode: 2002cosp...34E2963G Altcode: 2002cosp.meetE2963G We present a thermal model to explain the temporal variations of the water production rates QH2 O of comet 46P/Wirtanen, in order to analyse its surface. Our model is a differenciated spherical nucleus with a macroscopic mosaic of small and numerous active and inactive regions. At a heliocentric distance Rh >1.5 AU, the active regions represent 5-15 % of the surface. At 1.5 AU, a rapid increase takes place in about 10 days and the active fraction reaches 70 to 100 %, and then remains approximatively constant up to perihelion where QH2 O =1.1-1.7 1028 molecules s-1 . Post-perihelion, the activity goes down again to 10 %. The model is consistent with a geometric albedo lower than 0.1. A rubble mantle of a few millimeters can form post-perihelion and explain the variations of the activity over one orbit. Finally, we derived an erosion of 1 meter per revolution and a lifetime for the nucleus of several hundred revolu- tions. Title: The Rosetta/Osiris Narrow Angle Camera: Performances and Prospects for High Spatial Resolution Imaging of the Nucleus of Comet 46P/Wirtanen Authors: Lamy, P.; Jorda, L.; Origne, A.; Thomas, N.; Hviid, S. Bibcode: 2002cosp...34E3158L Altcode: 2002cosp.meetE3158L The Narrow Angle Camera (NAC) of the OSIRIS experiment is aimed at imaging a cometary nucleus, that of 46P/Wirtanen, at an unsurpassed spatial resolution of a few centimeters per pixel. We describe the innovative three-mirror, anastigmatic optical design and its all silicon carbide implementation (mirrors and structure). We report on the extended program of tests and calibrations carried out to fully characterize the instrument, in particular at low temperatures, and synthesize the actual performances. We finally discuss the future program of observation and the prospect for characterizing the asteroids Otawara and Siwa and the nucleus of 46P/Wirtanen. Title: Evolution of the Electron Density in the Streamer Belt during the Solar Authors: Llebaria, A.; Lamy, P.; Saez, F. Bibcode: 2002cosp...34E1606L Altcode: 2002cosp.meetE1606L White-light images of the corona obtained with the SOHO/LASCO-C2 coronagraph over more than six years reveal the dramatic changes of the structure and radiance distribution of the streamer belt from the minimum to the maximum of the present solar cycle. While it is qualitatively understood that the widening of the belt is a consequence of the tilting and warpening of the plasma current sheet, no quantitative study has been performed to derive physical parameters from these images in order to help characterizing the slow solar wind. Our approach consists in reproducing the widening of the streamer belt and its periodic evolution with the solar rotation with a model combining a layer of plasma centered around the heliospheric current sheet and isolated streamers associated to active regions. The Thompson scattering from the coronal electrons of this 3D model is calculated and comp ared to the LASC0-C2 images. This allows to estimate the local electron density in the corona between 3 and 6 solar radii during the rising phase of a solar cycle and to put constraints on the evolution of the slow solar wind. Title: Hubble Space Telescope Observations of the Nucleus of Comet 9P/Tempel 1 Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A.; Weissman, P. R. Bibcode: 2001Icar..154..337L Altcode: The nucleus of Comet 9P/Tempel 1, the target of the Deep Impact mission, was detected during Hubble Space Telescope observations taken with the wide-field planetary camera 2 (WFPC2) on 31 December 1997 when the comet's solar phase angle was 3.°8, its heliocentric distance was 4.48 AU, and its geocentric distance was 3.53 AU. Sixteen images were taken through the F675W filter, and all of them revealed a point-like source without any detectable coma. From these images, we derived the R magnitude of the nucleus in the Johnson-Kron-Cousins photometric system for the entire 11.5-h time span of the observations. Assuming a prolate spheroid whose spin axis lies close to the plane of the sky, the partial lightcurve indicates semi-axes a=3.9 km and b=2.8 km (assuming a geometric albedo of 0.04 for the R band and a phase coefficient of 0.04 mag deg -1) and a rotational period in the range of ∼25-33 h. The upper limit of the parameter Afρ, which characterizes the dust production rate, is 1 cm. We also derive a fractional active area at 1.78 AU of ∼4%. Title: Latest Results from SOHO/LASCO Observations of Kreutz Family Comets Authors: Biesecker, D. A.; Lamy, P. L.; St. Cyr, O. C.; Llebaria, A.; Howard, R. A. Bibcode: 2001DPS....33.4601B Altcode: 2001BAAS...33Q1123B As of September 2001, almost 350 members of the Kreutz sungrazing comet family have been observed with the LASCO coronagraphs on SOHO. The lightcurves of many of these comets share common features. They all reach a peak brightness at a heliocentric distance of about 12 solar radii (0.056 AU), then fade as they approach closer to the Sun, down to a distance of 7 solar radii where the fading stops. A closer examination reveals that two groups can be distinguished, one which peaks at 11.2 solar radii and one at 12.3 solar radii. Observations through an `Orange' filter (5400-6400 Angstroms) are systematically brighter than those through a `Clear' filter (4000-9000 Angstroms) and the difference changes with heliocentric distance. Recently, high cadence observations with other color filters have shown that the enhancement is limited to the Orange and Clear filters. This supports our idea that Na emission is a likely candidate for the enhancement. We will present these observations as well as our latest ideas to explain the LASCO observations. Title: The Nucleus of 10 Short-Period Comets Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Delahodde, C. E.; Jorda, L.; A'Hearn, M. F. Bibcode: 2001DPS....33.3101L Altcode: 2001BAAS...33Q1093L We report on the successful detection and extensive characterization of the nuclei of 10 short-period comets with the Hubble Space Telescope: 47P/Ashbrook-Jackson, 61P/Shajn-Schaldach, 70P/Kojima, 74P/Smirnova-Chernikh, 76P/West-Kohoutek-Ikemura, 82P/Gehrels 3, 86P/Wild 3, 87P/Bus, 110P/Hartley 3, 147P/Kushida-Muramatsu. The observations were performed with the Planetary Camera of WFPC2 during cycle 9, between July 2000 and June 2001. Each comet was observed eight times over a time span of about 12 hours through different filters, up to three (V, R, I) for the brightest ones. The sizes were determined assuming a geometric albedo of 0.04 for the R band and a phase law of 0.04 mag/deg. We confirm our past findings that cometary nuclei are generally extremely small; the radius of 147P/Kushida-Muramatsu was only 0.13 km. We also present the results for the colors and the lightcurves of the nuclei and discuss the implications for their shape and rotational state. This work was supported by grants from the Universite de Provence, from C.N.E.S., C.N.R.S. (France), from the Hungarian Academy of Science and from NASA through grant HST-GO-08699.01-A from the STScI. Title: Broadband infrared photometry of comet Hale-Bopp with ISOPHOT Authors: Grün, E.; Hanner, M. S.; Peschke, S. B.; Müller, T.; Boehnhardt, H.; Brooke, T. Y.; Campins, H.; Crovisier, J.; Delahodde, C.; Heinrichsen, I.; Keller, H. U.; Knacke, R. F.; Krüger, H.; Lamy, P.; Leinert, Ch.; Lemke, D.; Lisse, C. M.; Müller, M.; Osip, D. J.; Solc, M.; Stickel, M.; Sykes, M.; Vanysek, V.; Zarnecki, J. Bibcode: 2001A&A...377.1098G Altcode: Comet Hale-Bopp was observed five times with ISOPHOT, the photometer on board ESA's Infrared Space Observatory (ISO) between 4.6 and 2.8 AU. Each time, broadband photometry was performed using 4 different detectors, 5 apertures and 10 filters covering the range between 3.6 and 170 mu m. Background observations were performed with identical instrument settings at the same positions on the sky several days after the comet observations. The observation strategy and the data reduction steps are described in some detail, including the techniques to correct for variable detector responsivity. The resulting inband power values of the Hale-Bopp observations and their uncertainties are given. The mean uncertainty is 25%. The final fluxes were computed, taking into account the zodiacal background, possible offset of the comet's position from the center of the aperture, the brightness distribution within the coma, and the spectral energy distribution of the comet's emission. Strong thermal emission from a broad size distribution of dust particles was detected in all of the data sets, even at r=4.6-4.9 AU pre-perihelion and 3.9 AU post-perihelion; the total thermal energy varied as r-3. The 7.3-12.8 mu m color temperature was ~ 1.5 times the blackbody temperature, higher than that observed in any other comet. Silicate features at 10 and 25 mu m were prominent in all 5 data sets, the largest heliocentric distances that silicate emission has been detected in a comet. The presence of crystalline water ice grains is suggested from the 60 mu m excess emission at 4.6-4.9 AU, consistent with the observed Qmathrm {OH} if the icy grains were slightly warmer than an equilibrium blackbody. The average albedo of the dust is higher than that of comet P/Halley, but lower than other albedo measurements for Hale-Bopp nearer perihelion. There is no evidence for a component of cold, bright icy grains enhancing the scattered light at 4.6 AU. Simple models for a mixture of silicate and absorbing grains were fit to the ISO spectra and photometry at 2.8 AU. The observed flux at lambda > 100 mu m requires a size distribution in which most of the mass is concentrated in large particles. Dust production rates of order 1.5x 105 kg s-1 at 2.8 AU and 3x 104 kg s-1 at 4.6 AU have been found. They correspond to dust to gas mass ratios of 6 to 10. With supporting observations by ISOCAM, SWS, LWS, and ground-based observations at the European Southern Observatory at La Silla in Chile. Title: Solar Polar Plume Lifetime and Coronal Hole Expansion: Determination from Long-Term Observations Authors: DeForest, C. E.; Lamy, P. L.; Llebaria, A. Bibcode: 2001ApJ...560..490D Altcode: We have generated off-limb polar synoptic charts of polar plume evolution at various solar altitudes using EUV Imaging Telescope and Large Angle and Spectrometric Coronagraph data from 1996 December. The charts allow direct measurement of the altitude expansion of the solar minimum coronal holes. We find expansion values that are consistent with the conventional picture of superradial expansion and inconsistent with radial expansion. Using visible red line data as a bridge between EUV and white-light images of the corona, we are able to confirm that the coronal structure seen at the base of the corona is preserved throughout the considered altitude range of 1.1-3.0 Rsolar. We show that polar plumes are episodic in nature, lasting perhaps 24 hr but recurring for up to weeks at a time; this strengthens the picture that they are caused by magnetic heating under the influence of supergranulation. Title: HST and VLT Investigations of the Fragments of Comet C/1999 S4 (LINEAR) Authors: Weaver, H. A.; Sekanina, Z.; Toth, I.; Delahodde, C. E.; Hainaut, O. R.; Lamy, P. L.; Bauer, J. M.; A'Hearn, M. F.; Arpigny, C.; Combi, M. R.; Davies, J. K.; Feldman, P. D.; Festou, M. C.; Hook, R.; Jorda, L.; Keesey, M. S. W.; Lisse, C. M.; Marsden, B. G.; Meech, K. J.; Tozzi, G. P.; West, R. Bibcode: 2001Sci...292.1329W Altcode: At least 16 fragments were detected in images of comet C/1999 S4 (LINEAR) taken on 5 August 2000 with the Hubble Space Telescope (HST) and on 6 August with the Very Large Telescope (VLT). Photometric analysis of the fragments indicates that the largest ones have effective spherical diameters of about 100 meters, which implies that the total mass in the observed fragments was about 2 × 109 kilograms. The comet's dust tail, which was the most prominent optical feature in August, was produced during a major fragmentation event, whose activity peaked on UT 22.8 +/- 0.2 July 2000. The mass of small particles (diameters less than about 230 micrometers) in the tail was about 4 × 108 kilograms, which is comparable to the mass contained in a large fragment and to the total mass lost from water sublimation after 21 July 2000 (about 3 × 108 kilograms). HST spectroscopic observations during 5 and 6 July 2000 demonstrate that the nucleus contained little carbon monoxide ice (ratio of carbon monoxide to water is less than or equal to 0.4%), which suggests that this volatile species did not play a role in the fragmentation of C/1999 S4 (LINEAR). Title: Projective Transform Techniques to Reconstruct the 3-D Structure and the Temporal Evolution of Solar Polar Plumes Authors: Llebaria, A.; Thernisien, A.; Lamy, P. Bibcode: 2001ASPC..238..377L Altcode: 2001adass..10..377L A sequence of 400 images obtained over three days with the C2-LASCO/SOHO coronagraph was used to disentangle the complex evolution of the structures observed on the corona of the Sun's North pole. Projective transforms were used to find and delimit the elusive linear structures on each image (< 1:1 of SNR). From frame to frame, these structures show strong brightness variations as well as lateral shifts which are linked to rotation of the Sun. Taking advantage of solar corona rotation as a rigid body (of ~28 days period), we are able to extract short sinograms to obtain a 3-D reconstruction with few hypotheses. The whole procedure is described, emphasizing the role of the bilinear transform as a new tool in this process. Title: Division III: Planetary Systems Sciences Authors: Marov, Mikhail Ya.; A'Hearn, G. M. F.; Baggaley, J.; Bowell, E.; Bowyer, S.; Cruikshank, D.; de Bergh, C.; Keller, H.; Lamy, P.; Porubcan, V.; Watanabe, J.; Williams, I.; Zappala, V. Bibcode: 2001IAUTB..24..113M Altcode: No abstract at ADS Title: The Mars NetLander panoramic camera Authors: Jaumann, Ralf; Langevin, Yves; Hauber, Ernst; Oberst, Jürgen; Grothues, Hans-Georg; Hoffmann, Harald; Soufflot, Alain; Bertaux, Jean-Loup; Dimarellis, Emmanuel; Mottola, Stefano; Bibring, Jean-Pierre; Neukum, Gerhard; Albertz, Jörg; Masson, Philippe; Pinet, Patrick; Lamy, Philippe; Formisano, Vittorio Bibcode: 2000P&SS...48.1377J Altcode: The panoramic camera (PanCam) imaging experiment is designed to obtain high-resolution multispectral stereoscopic panoramic images from each of the four Mars NetLander 2005 sites. The main scientific objectives to be addressed by the PanCam experiment are (1) to locate the landing sites and support the NetLander network sciences, (2) to geologically investigate and map the landing sites, and (3) to study the properties of the atmosphere and of variable phenomena. To place in situ measurements at a landing site into a proper regional context, it is necessary to determine the lander orientation on ground and to exactly locate the position of the landing site with respect to the available cartographic database. This is not possible by tracking alone due to the lack of on-ground orientation and the so-called map-tie problem. Images as provided by the PanCam allow to determine accurate tilt and north directions for each lander and to identify the lander locations based on landmarks, which can also be recognized in appropriate orbiter imagery. With this information, it will be further possible to improve the Mars-wide geodetic control point network and the resulting geometric precision of global map products. The major geoscientific objectives of the PanCam lander images are the recognition of surface features like ripples, ridges and troughs, and the identification and characterization of different rock and surface units based on their morphology, distribution, spectral characteristics, and physical properties. The analysis of the PanCam imagery will finally result in the generation of precise map products for each of the landing sites. So far comparative geologic studies of the Martian surface are restricted to the timely separated Mars Pathfinder and the two Viking Lander Missions. Further lander missions are in preparation (Beagle-2, Mars Surveyor 03). NetLander provides the unique opportunity to nearly double the number of accessible landing site data by providing simultaneous and long-term observations at four different surface locations which becomes especially important for studies of variable surface features as well as properties and phenomena of the atmosphere. Major changes on the surface that can be detected by PanCam are caused by eolian activities and condensation processes, which directly reflect variations in the prevailing near-surface wind regime and the diurnal and seasonal volatile and dust cycles. Atmospheric studies will concentrate on the detection of clouds, measurements of the aerosol contents and the water vapor absorption at 936 nm. In order to meet these objectives, the proposed PanCam instrument is a highly miniaturized, dedicated stereo and multispectral imaging device. The camera consists of two identical camera cubes, which are arranged in a common housing at a fixed stereo base length of 11 cm. Each camera cube is equipped with a CCD frame transfer detector with 1024×1024 active pixels and optics with a focal length of 13 mm yielding a field-of-view of 53°×53° and an instantaneous filed of view of 1.1 mrad. A filter swivel with six positions provides different color band passes in the wavelength range of 400-950 nm. The camera head is mounted on top of a deployable scissors boom and can be rotated by 360° to obtain a full panorama, which is already covered by eight images. The boom raises the camera head to a final altitude of 90 cm above the surface. Most camera activities will take place within the first week and the first month of the mission. During the remainder of the mission, the camera will operate with a reduced data rate to monitor time-dependent variations on a daily basis. PanCam is a joint German/French project with contributions from DLR, Institute of Space Sensor Technology and Planetary Exploration, Berlin, Institut d'Astrophysique Spatiale, CNRS, Orsay, and Service d'Aéronomie, CNRS, Verrières-le-Buisson. Title: The nucleus of 13 short-period comets Authors: Lamy, P. L.; Toth, I.; Weaver, H. A.; Delahodde, C.; Jorda, L.; A'Hearn, M. F. Bibcode: 2000DPS....32.3604L Altcode: 2000BAAS...32.1061L We report the successful detection of the nucleus of 13 short-period comets with the Hubble Space Telescope. One orbit was devoted to each comet and the observations were performed with the Planetary Camera and at least two filters (V and R) and up to four (B, V, R, I) for the brightest ones. Assuming spherical nuclei with a geometric albedo of 0.04 for the R band and a phase law of 0.04 mag/deg, we determined the following radii: 4P/Faye: 1.77 km; 10P/Tempel 2: 4.60 km; 17P/Holmes: 1.71 km; 37P/Forbes: 0.81 km; 44P/Reinmuth 2: 1.63 km; 50P/Arend: 0.95 km; 59P/Kearns-Kwee: 0.79 km; 63P/Wild 1: 1.46 km; 71P/Clark: 0.68 km; 84P/Giclas: 0.90 km; 106P/Schuster: 0.94 km; 112P/Urata-Niijima: 0.90 km; 114P/Wiseman-Skiff: 0.78 km. We also obtained the spectral reflectivities of those nuclei and of their coma and calculated the dust production rates. Title: Detailed Phase Function of a Comet Nucleus: 28P/Neujmin 1 Authors: Delahodde, C. E.; Hainaut, O. R.; Lamy, P. L.; Meech, K. J. Bibcode: 2000DPS....32.3609D Altcode: 2000BAAS...32.1062D Very little is known on the surface properties of cometary nuclei -- with the notable exception of the in-situ measurements for comet Halley. A still unexplored method of investigation is the study of the solar phase function, which can give us direct information on the surface roughness as well as some independent constraints on the albedo. In order to estimate properly the Hapke parameters describing the phase function, one has to obtain measurements not only over a broad phase angle (α ) range, but also at very small phase angle, in order to sample the ``opposition surge'', a brightening of the phase curve occurring at α < 2-3o. In 2000, Comet 28P/Neujmin 1 was an ideal candidate for a phase function study: its April opposition was almost ideal (α = 0.8° ), and previous observations by Meech et al. at similar heliocentric distances (rh >= 4 AU) indicated that the comet was likely not to be active. We observed this comet using ESO's NTT and 2.2m telescopes at La Silla, on 6 epochs from April to August 2000, covering α = 0.8 - 8o , with a good sampling of the opposition surge. In order to disentangle the rotation effects from the phase effects, we obtained a complete rotation coverage at opposition, providing us with a light-curve template. For each subsequent epoch, we have obtained enough rotation coverage to re-synchronize the light-curve fragments with the template, and determine the magnitude change caused by the phase function. Using these data, we hope to present the first detailed comet nucleus phase function, and compare it with known C-type asteroids. Title: Spectral properties of the nucleus of short-period comets Authors: Toth, I.; Lamy, P. L. Bibcode: 2000DPS....32.3705T Altcode: 2000BAAS...32.1063T Comets, Edgeworth-Kuiper-Belt Objects (EKBOs), Centaurs and low albedo asteroids contain a considerable amount of information regarding some of the primordial processes that governed the formation of the early Solar System planetesimals. Opportunities to determine the colors of cometary nuclei are rare and relevant ground-based observations are difficult to perform. Color diversities and similarities between different types of small bodies have already been considered ([1] and references therein). We pursue this analysis further by introducing new BVRI colors obtained from our survey of cometary nuclei with the Hubble Space Telescope [2] as well as recent data obtained on EKBOs. We present preliminary results on the distribution of the BVRI colors (histograms, two-color diagrams) and possible relationships between the colors and orbital elements as well as the determined body sizes. The mean colors of the selected sample of the short-period (s-p) comets are: < (B-V) > = 0.91, < (V-R) > = 0.52, and < (V-I) > = 0.84. Pearson's linear correlation analysis of the (B-V) versus (V-R) and (V-R) versus (V-I) colors show significant correlations for the EKBOs+Centaurs sample while the s-p sample seems to be uncorrelated, with a few outliers. The linear regression lines of the EKBOs+Centaurs sample crosses through the sample of the s-p comets. There are no correlations of the colors versus perihelion distances, effective radii and perihelion distances as well as the (a,sin(i)) diagrams. This work was supported by grants from CNRS and CNES, France and partially by the the Hungarian Research Foundation OTKA T025049. [1] Luu, J., 1993. Icarus 104, 138. [2] Lamy, P.L. et al., this conference Title: HST and VLT Investigations of the Fragments of C/1999 S4 (LINEAR) Authors: Weaver, H. A.; West, R.; A'Hearn, M. F.; Arpigny, C.; Bauer, J. M.; Combi, M. R.; Davies, J. K.; Delahodde, C. E.; Feldman, P. D.; Fes tou, M. C.; Hainaut, O. R.; Hook, R.; Jorda, L.; Keesey, M. S. W.; Lamy, P. L.; Lisse, C. M.; Marsden, B. G.; Meech, K. J.; Sekanina, Z.; Toth, I.; Tozzi, G. -P. Bibcode: 2000DPS....32.3606W Altcode: 2000BAAS...32.1061W Observations of C/1999 S4 (LINEAR) with the Hubble Space Telescope (HST) on 2000 August 5.167--5.467 UT and with the Very Large Telescope (VLT) on August 6.978--6.999 UT revealed the presence of over 17 fragments following the breakup of the nucleus in late July. Nearly half the fragments were located in a ``swarm'' near the western ``tip'' of the dust tail (i.e., the sunward side of the tail), but several were significantly sunward of the tip, including one object that we tentatively identify as the primary remnant of the original nucleus. The correspondence between fragments in the HST and VLT images is generally very good, but the brightest fragment in the HST image is not seen in the VLT image, indicating rapid variability in activity. The dynamic nature of the fragments was further highlighted by a dramatic change in the appearance of the fragments in VLT images taken during August 9.976--9.996 UT, when they were barely detectable. The locations and brightnesses of the fragments will be presented, along with a discussion of the dynamics associated with the breakup event and its subsequent evolution. We thank the Directors of the Space Telescope Science Institute and the ESO/VLT for approving our observing programs for Director's Discretionary Time. Title: Properties of 2060 Chiron from infrared ISOPHOT observations Authors: Groussin, O.; Peschke, S.; Lamy, P. L. Bibcode: 2000DPS....32.2105G Altcode: 2000BAAS...32.1031G We present the analysis of new observations of 2060 Chiron with the Infrared Space Observatory (ISO). They were performed with the ISO photometer (ISOPHOT) from 8 to 15 June 1996, when Chiron was near perihelion at a heliocentric distance of 8.46 AU, using four filters centered at 25, 60, 100 and 160 μ m. The observed fluxes are fitted to a thermal model which considers a mixture of water ice and refractory materials on the surface and includes heat conduction into the interior of the nucleus. We derive a thermal inertia of 10 JK-1m-2s-1/2. Combining the present IR data with visible observations by Luu (1990) and Marcialis (1993), we determine a radius of 80+/-10 km and a geometric albedo of 0.14+/-0.02. Title: Observation of the origin of CMEs in the low corona Authors: Delannée, C.; Delaboudinière, J. -P.; Lamy, P. Bibcode: 2000A&A...355..725D Altcode: The aim of the main observing program with EIT on board SOHO, is to monitor the whole Sun surface in the Fe xii emission line at 195 Ä, every 17 minutes. The very beginning of some CMEs can be observed. We interpret Fe xii images in conjunction with He ii, Hα and coronagraph observations over a period of 6 days. We find that 7 prominences produced ejections. An active region produced 9 ejections. Five ejections are seen as dark bubbles propagating above the solar limb while 9 are seen as dimmings on the solar surface. The 3 other ejections are bright bubbles observed rising up above the limb. Thirteen of the 17 observed ejections are related to a CME. Two CMEs of the 15 CMEs observed with LASCO C2 are not related to Fe xii low corona events. Probably, these CMEs have their origin behind the limb. Prominences give rise to quite slow CMEs, 50-120 km s-1 while fast CMEs, 110-1000 km s-1, originate close to active regions. We conclude that CMEs start in the low corona and that large scale coronal structures reconfigurations occur when these disturbances propagate outward. Title: Properties of coronal mass ejections: SOHO LASCO observations from January 1996 to June 1998 Authors: St. Cyr, O. C.; Plunkett, S. P.; Michels, D. J.; Paswaters, S. E.; Koomen, M. J.; Simnett, G. M.; Thompson, B. J.; Gurman, J. B.; Schwenn, R.; Webb, D. F.; Hildner, E.; Lamy, P. L. Bibcode: 2000JGR...10518169S Altcode: 2000JGR...105.8169S; 2000JGRA..105.8169S We report the properties of all the 841 coronal mass ejections (CMEs) observed by the Solar and Heliospheric Observatory (SOHO) Large Angle Spectroscopic Coronagraph (LASCO) C2 and C3 white-light coronagraphs from January 1996 through June 1998, and we compare those properties to previous observations by other similar instruments. Both the CME rate and the distribution of apparent locations of CMEs varied during this period as expected based on previous solar cycles. The distribution of apparent speeds and the fraction of CMEs showing acceleration were also in agreement with earlier reports. The pointing stability provided by an L-1 orbit and the use of CCD detectors have resulted in superior brightness sensitivity for LASCO over earlier coronagraphs; however, we have not detected a significant population of fainter (i.e., low mass) CMEs. The general shape of the distribution of apparent sizes for LASCO CMEs is similar to those of earlier reports, but the average (median) apparent size of 72° (50°) is significantly larger. The larger average apparent size is predominantly the result of the detection of a population of partial and complete halo CMEs, at least some of which appear to be events with a significant longitudinal component directed along the Sun-Earth line, either toward or away from the Earth. Using full disk solar images obtained by the Extreme ultraviolet Imaging Telescope (EIT) on SOHO, we found that 40 out of 92 of these events might have been directed toward the Earth, and we compared the timing of those with the Kp geomagnetic storm index in the days following the CME. Although the ``false alarm'' rate was high, we found that 15 out of 21 (71%) of the Kp>=6 storms could be accounted for as SOHO LASCO/EIT frontside halo CMEs. If we eliminate three Kp storms that occurred following LASCO/EIT data gaps, then the possible association rate was 15 out of 18 (83%). Title: Commission 21: Light of the Night Sky: (Lumiere du Ciel Nocturne) Authors: Bowyer, S.; Lamy, P.; Dwek, E.; Gustafson, B.; Hanner, M.; Levasseur-Regourd, A. Ch.; Mikhail, J.; Mann, I.; Mukai, T.; Matsumoto, T. Bibcode: 2000IAUTA..24..152B Altcode: No abstract at ADS Title: ISOCAM Observations of Cometary Nuclei Authors: Jorda, L.; Lamy, P.; Groussin, O.; Toth, I.; A'Hearn, M. F.; Peschke, S. Bibcode: 2000ESASP.455...61J Altcode: 2000ibps.conf...61J ISOCAM images of comets C/1995 O1 (Hale-Bopp), 22P/Kopff, 46P/Wirtanen, 55P/Tempel-Tuttle, 103P/Hartley and 126P/IRAS were obtained between 7.8 and 15 microns in Oct.-Nov. 1996 and Jan.-Feb. 1998 in order to characterize their nucleus by detecting their thermal emission. All images were corrected for the dark current, detector non-uniformity and transient effects with standard methods available in CIA V3.0. Further IDL based processing is performed to correct the images from the overshot, preserve the nuclear region from glitch removal and eliminate images with a high percentage of glitches. The signal from the nucleus was measured by fitting the data with a model including the contribution from both the coma and the nucleus. By combining the thermal fluxes with the visible fluxes, obtained with the same technique from HST images, we derived the size and geometric albedo of three comets (C/1995 O1, 22P and 55P). For comets 103P and 126P, we only derived their size. The radii range from 0.56 km (103P) to 56 km (C/1995 O1). The determined geometric albedos are between 0.02 and 0.07, in agreement with previous measurements on several other nuclei. Title: Coronal Mass Ejections and Large Scale Structure of the Corona Authors: Maia, D.; Vourlidas, A.; Pick, M.; Howard, R.; Schwenn, R.; Lamy, P. Bibcode: 2000AdSpR..25.1843M Altcode: A comparative study of two events accompanied by both a flare and a CME has been performed. The data analysis has been made by comparing the observations of the LASCO/SOHO coronagraphs with those of the Nancay radioheliograph. The observations show a clear connection between coronal green and red line transient activity, burst radio emission and the CME development which is due to successive loop interactions. Signatures of these interactions are given by the radio emission. One can identify successive sequences in the evolution of the coronal restructuring leading to the full development of the CME. Identification and timing of these sequences result from the radio emission analysis. For flare-CME events , the evolution takes place in the low corona and is extremely fast of the order, on a few minutes Title: CMEs Observed Continuously from the Lower Corona to the Far Corona Authors: Delannée, C.; Delaboudinière, J. -P.; Lamy, P. Bibcode: 2000AdSpR..26...67D Altcode: A campaign of observations with EIT on board SOHO called ``CME watch'', is designed to observe the whole sun surface in 195 A&ring i.e. in a Fe XII emission line, every 17 minutes. In order to analyze the events, we also used He II and coronagraph observations of 97/11/03. By this way, the very beginning of some CMEs was observed. The ejections were seen in Fe XII as a dark bubble propagating in the corona above a prominence, and dimmings produced near an active region and propagating on the solar surface. Two of the ejections coming from the active region were produced with a very short time of delay (1 hour). All the ejections were associated to a CME. However, one CME was not related to a Fe xII low corona event, but maybe this CME had its origin behind the limb. The CME associated with the prominence was quite slow (50 km s-1) and the ones associated with the active region were quite fast (114-490 km s-1). This analysis permitted a better identification of the different CMEs appearing in the coronagraph field of view Title: Eclipse of August 11, 1999: White-light Images and Simultaneous EIT/SOHO Observations Authors: Adjabshirizadeh, A.; Baudin, F.; Bocchialini, K.; Delaboudinière, J. -P.; Grorod, P. -A.; Koutchmy, S.; Laal Aaly, M.; Lamy, P.; Lochard, J.; Mouette, J. Bibcode: 1999ESASP.448.1283A Altcode: 1999ESPM....9.1283A; 1999mfsp.conf.1283A No abstract at ADS Title: The Global Activity of the Solar Corona Authors: Llebaria, A.; Lamy, P.; Koutchmy, S. Bibcode: 1999ESASP.446..441L Altcode: 1999soho....8..441L The question of the global activity of the solar corona, as a function of time and distance from the center of the Sun, is considered by analyzing long time-series of LASCO-C2 images. Polarized images are first considered to perform the separation of the K and F components. The F-corona images are used to construct a photometric model of the F-corona wich reflects its annual variations resulting from geometric effects. This time-varying model is then subtracted from all corrected and calibrated images (unpolarized) to yield images of the K-corona. Synoptic maps are created at different distances between 2.5 and 6 solar radii and the total white-light intensity is integrated to estimate the total mass of the corona. Its variations in the range of heliocentric distance and over a time span of 3 years will be presented and discussed. Title: Monolithic SiC telescope of the OSIRIS Narrow-Angle Camera for the cometary mission ROSETTA Authors: Castel, Didier; Calvel, Bertrand; Lamy, Philippe L.; Dohlen, Kjetil; Bougoin, Michel Bibcode: 1999SPIE.3785...56C Altcode: The international Rosetta mission, now planned by ESA to be launched in January 2003, will provide a unique opportunity to directly study the nucleus of comet 46P/Wirtanen and its activity from a heliocentric distance of 3.2 AU to the perihelion passage at 1.06 AU in July 2013. We describe here the design, the development and the performances of the telescope of the Narrow Angle Camera of the OSIRIS experiment which will give high resolution images of the cometary nucleus in the visible spectrum. Title: Simultaneous LASCO/1998-Eclipse Observations Of A Large-Scale Polar Event Authors: Zhukov, A.; Koutchmy, S.; Lamy, Ph.; Delaboudinière, J. -P.; Delannée, C.; Bocchialini, K.; Guisard, S.; Filippov, B.; Veselovsky, I. Bibcode: 1999ESASP.446..731Z Altcode: 1999soho....8..731Z A relatively faint but large scale polar region event was observed in Aug. 1996 by Boulade et al. 1998 (SoHO SP 404, 217); we first reconsider this event which has been related to a high latitude filament disappearance. We continue the study of this class of events by analyzing the large scale restructuring which occurred above the N-Pole region at the time of the last Feb. 26, 1998 total solar eclipse. Well calibrated WL-eclipse images are used to provide the absolute values of electron densities of the quasi-radial structure appearing at the feet of the event. This structure can also be considered as a type of abnormally broad and curved polar plume, a type of activity already reported in the literature. Unfortunately, the examination of sequences of EIT images taken at that time seems to indicate that the roots of the structure are on the back side of the Sun. However the most impressive effects are seen in the high polar region, at several radii, based on the analysis of processed Lasco-C2 difference images. Large proper motions are deduced over density structures. Both these events confirm that polar regions are indeed showing a new class of CME activity (possibly related to the Hewish's CMEs), which is seen inside coronal holes. A whole set of interesting questions is then appearing to understand the occurrence of a polar CME propagating in the heart of a large unipolar magnetic region of the corona. Title: Characterization of the nucleus of comet Hale-Bopp from HST and ISO observations Authors: Lamy, P.; Jorda, L.; Toth, I.; Groussin, O.; A'Hearn, M. F.; Weaver, H. A. Bibcode: 1999DPS....31.2703L Altcode: High resolution images were obtained in the visible with the Planetary Camera of the Hubble Space Telescope and "B,V,R" filters and in the thermal infrared with ISOCAM and from filters centered at 7.75, 9.62, 11.4 and 15.0 micron. The latter images were carefully processed to independently correct for the temporal evolution of the signal in each pixel. Using our standard technics, we separated the nuclear and comatic contributions to retrieve the flux from the nucleus. Two thermal models were used to interpret the infrared fluxes, the Standard Thermal Model (STM) and a mixed ice-dust model. Combining the visible and thermal data, the STM model suggests a body with a radius of 35+/-6 km with an albedo of 0.05+/-0.02 and a maximum temperature of 254 K while the mixed model indicates a larger radius 52+/-5 km and a lower maximum temperature of 192 K. The spectral energy distribution is best fit with the mixed ice-dust model with an excess at 10 micron attributed to the silicate band. Title: The sungrazing comets discovered with the SOHO/LASCO coronagraphs: 1996-1998. Authors: Biesecker, D. A.; Lamy, P.; St. Cyr, O. C.; Llebaria, A.; Howard, R. Bibcode: 1999DPS....31.1404B Altcode: An unprecedented number of Kreutz sungrazing comets have been discovered with the LASCO coronagraphs on the SOHO spacecraft. We present here the results of the analysis of the first 53 sungrazing comets, which were discovered between January, 1996 and June, 1998. In this poster, we summarize the capabilities and calibration of the LASCO coronagraphs for comet observations. We discuss the frequency of the comet discoveries and summarize the properties of the computed orbits. We show examples of typical comet light curves and discuss their common features. In particular, we show that the comets are completely disintegrated before they reach perihelion. One particular feature of the observations is the presence of a dust tail for only a few sungrazers while no tail is evident for the majority of them. Analysis of the light curves is used to investigate the properties of the nuclei (size, fragmentation, destruction) and the dust production rates. This work was funded in part by NASA SOHO-GI Grant NAG5-8003. Title: The sungrazing comets discovered with the SOHO/LASCO coronagraphs: 1996-1998. Authors: Biesecker, D. A.; Lamy, P.; St. Cyr, O. C.; Llebaria, A.; Howard, R. Bibcode: 1999BAAS...31.1094B Altcode: No abstract at ADS Title: Experiments for in-situ monitoring of dust environments in the Solar System Authors: Colangeli, L.; Bussoletti, E.; Lopez Moreno, J. J.; Epifani, E.; Esposito, F.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Morales, R.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Ruiz-Falco, A.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Coradini, A.; Giovane, F.; Gruen, E.; Gustafson, B.; Maag, C.; Weissman, P. R. Bibcode: 1999DPS....31.2906C Altcode: "Dust" is present in the Solar System, from planetary surfaces to comets. The in-situ monitoring of its physical and dynamical properties is one of the main scientific tasks to be achieved in order to characterise grains and to correctly understand their role in the evolution of Solar System bodies. A new generation of methods for in-situ exploration of dusty environments in the Solar System has been studied and adopted in different instruments under development or study for future planetary space missions. Mass flux measurements by quartz crystal microbalances, optical detection of single grains and momentum monitoring by piezoelectric transducers are techniques which provide high sensitivity for grains at relatively low (below some hundreds m/s) velocities. The GIADA (Grain Impact Analyser and Dust Accumulator) experiment is part of the payload of the ESA Rosetta orbiter, targeted to a rendez-vous of 46P/Wirtanen comet. Thanks to GIADA, one of the prime scientific objectives of the mission will be fulfilled, i.e. the monitoring of the cometary coma dust environment. The dust flux from different directions vs. time and the momentum and velocity vs. mass of particles will be measured, while comet will approach the Sun. The MAGO (Martian Atmospheric Grain Observer) instrument, under study in the framework of the next Mars exploration opportunities (e.g.: Mars Surveyor Program 2003) adopts similar technical solutions and is aimed at measuring, directly for the first time, the dust mass flux in the Martian atmosphere and the dynamical properties of airborne particles vs. time. Finally, similar measurement techniques can be integrated with other detection/collection systems (e.g. aerogel collectors) to monitor the dust in the near Earth environment, e.g. from the space station. Title: Characterization of the nucleus of comet Hale-Bopp from HST and ISO observations. Authors: Lamy, P.; Jorda, L.; Toth, I.; Groussin, O.; A'Hearn, M. F.; Weaver, H. A. Bibcode: 1999BAAS...31.1116L Altcode: No abstract at ADS Title: Hubble Space Telescope Observations of the Nucleus of Comet 45P/Honda-Mrkos-Pajdusakova and Its Inner Coma Authors: Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A. Bibcode: 1999Icar..140..424L Altcode: The nucleus of Comet 45P/Honda-Mrkos-Pajdusakova was detected during Hubble Space Telescope observations taken with the Wide-Field Planetary Camera 2 (WFPC2) in February 1996 when the comet was 0.17 AU from the Earth. The high spatial resolution (1 pixel projected to 5.6 km at the distance of the comet) allowed us to separate the signal of the nucleus from that of the coma, and images taken through five broadband filters allowed us to determine the UBVRI magnitudes of the nucleus in the Johnson-Kron-Cousins photometric system (sometime known as the Landolt system). Assuming a spherical body whose geometric albedo is 0.04 for the V band and a phase coefficient of 0.04 mag/deg, we derive an effective radius of 0.34 km. The uncertainty is dominated by the unknown phase law; the radius may be as small as 0.22 km if the phase coefficient is 0.03 mag/deg. The correlated variations of the magnitudes over 1 day suggest an elongated body with an axis ratio of at least 1.3. The strong reddening of the nucleus in the ultraviolet progressively decreases, and its color tends to neutral in the near infrared. We also derive a fractional active area of 11% and a dust production rate of 1.0 kg s-1 (86 metric tons day-1). Title: Streamer disconnection events observed with the LASCO coronagraph Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Rich, N. B.; Lamy, P. L. Bibcode: 1999GeoRL..26.1349W Altcode: We present Large Angle Spectrometric Coronagraph (LASCO) observations of two events that suggest magnetic disconnection in coronal streamers. During the 1-2 days preceding each event, successions of narrow looptops are seen rising slowly through the 2-6 RS field of view, forming a bright streamer stalk which continues to elongate with time. As the streamer becomes ever more constricted, it eventually severs at a heliocentric distance of ∼4 RS. The lower part of the stalk collapses back to form a cusplike structure extending to ∼3 RS, while the disconnected segment is observed as a kink or density enhancement that propagates outward with a speed of order 200 km s-1. We interpret these non-CME events as transient openings and closings of magnetic flux rooted at the boundaries of coronal holes. Title: Influence of image compression on the in situ stereoscopic reconstruction of a cometary surface for the ROSETTA mission. Authors: Takerkart, S.; Lamy, P.; Llebaria, A. Bibcode: 1999CRASB.327..547T Altcode: As part of the ROSETTA mission, the surface science package, wich will land on the nucleus of the comet 46P/Wirtanen, includes a stereoscopic imaging instrument CIVA-P. The data volume required by the scientific objectives and the limited capability of the telemetry imposes the use of image-loss compression techniques. The authors study the influence of the losses due to compression on the three-dimensional surface reconstruction. They prove that the best strategy consists in compressing both the left and right images with the same ratio, transmitting them and finally applying on Earth the stereoscopic calculation on the decompressed images. Title: ISOPHOT observations of comet Hale-Bopp: initial data reduction Authors: Grun, E.; Peschke, S. B.; Stickel, M.; Muller, T. G.; Kruger, H.; Bohmhardt, H.; Brooke, T. Y.; Campins, H.; Crovisier, J.; Hanner, M. S.; Heinrichsen, I.; Keller, H. U.; Knacke, R.; Lamy, P.; Leinert, C.; Lemke, D.; Lisse, C. M.; Muller, M.; Osip, D. J.; Solc, M.; Sykes, M.; Vanysek, V.; Zarnecki, J. Bibcode: 1999ESASP.427..181G Altcode: 1999usis.conf..181G; 1998astro.ph.12171G Comet Hale-Bopp was observed five times with ISOPHOT, the photometer on board the Infrared Space Observatory (ISO). Each time broadband photometry was performed using 4 different detectors, 5 apertures and, 10 filters covering the range between 3.6 to 175 μm. Calibration measurements using the internal Fine Calibration Source were done together with each individual measurement. Background observations were performed with identical instrument settings at the same positions on the sky several days after the comet observations. The observation strategy and the initial data reduction steps are described in some detail and the resulting in-band power values of the Hale-Bopp observations and their uncertainties are derived. Initial reduction of these measurements was performed in 3 steps: (1) processing of raw data by removing instrumental and energetic particle effects, (2) averaging of the individual signals, and (3) determination of the detector responsivities and their uncertainties. The detector signal is determined by two different methods and the best value is chosen. At the present level of processing uncertainties range from 10% to a factor of 3 for the low power levels at short wavelengths. The in-band power levels at different wavelengths varied over 3 orders of magnitude. Title: LASCO observations of the coronal rotation Authors: Lewis, D. J.; Simnett, G. M.; Brueckner, G. E.; Howard, R. A.; Lamy, P. L.; Schwenn, R. Bibcode: 1999SoPh..184..297L Altcode: The near-rigid rotation of the corona above the differential rotation of the photosphere has important implications for the form of the global coronal magnetic field. The magnetic reconfiguring associated with the shear region where the rigidly-rotating coronal field lines interface with the differentially-rotating photospheric field lines could provide an important energy source for coronal heating. We present data on coronal rotation as a function of altitude provided by the Large Angle Spectrometric Coronagraph (LASCO) instrument aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. LASCO comprises of three coronagraphs (C1, C2, and C3) with nested fields-of-view spanning 1.1 R⊙ to 30 R⊙. An asymmetry in brightness, both of the Fe xiv emission line corona and of the broad-band electron scattered corona, has been observed to be stable over at least a one-year period spanning May 1996 to May 1997. This feature has presented a tracer for the coronal rotation and allowed period estimates to be made to beyond 15 R⊙, up to 5 times further than previously recorded for the white-light corona. The difficulty in determining the extent of differential motion in the outer corona is demonstrated and latitudinally averaged rates formed and determined as a function of distance from the Sun. The altitude extent of the low latitude closed coronal field region is inferred from the determined rotation periods which is important to the ability of the solar atmosphere to retain energetic particles. For the inner green line corona (<2 R⊙) we determine a synodic rotation period of (27.4±0.1) days, whereas, for the outer white- light corona, (>2.5 R⊙) we determine a rotation period of (27.7±0.1) days. Title: Time Domain Analysis of Solar Coronal Structures Through Hough Transform TEC hniques Authors: Llebaria, A.; Lamy, P. Bibcode: 1999ASPC..172...46L Altcode: 1999adass...8...46L The Hough transform technique is applied to a series of images from the LASCO/C2 coronagraph in order to understand the temporal evolution of radial structures on the solar corona, the so-called ``polar plumes''. They may corotate with the solar corona and therefore change aspect with time due to projection effects on the plane of the sky. In the images these structures suddenly appear, shift, mix, and fade away on short periods of time. >From a long series of images (~100), we determined for each image the polar intensity profile and built up the evolution of such profiles against time. The result is a Time Intensity Diagram (TID) where intensities are plotted with respect to time and position coordinates. Radial structures appear as peak intensities in each profile and therefore as bright points in the TID. The Hough transform techniques are applied to detect coherent trajectories. This technique has been applied successfully to study coronal plumes on coronal images obtained by different instruments aboard the SOHO satellite. Title: The GIADA Experiment for Rosetta Mission to Comet 46P/Wirtanen: Design and Performances Authors: Bussoletti, E.; Colangeli, L.; Lopez Moreno, J. J.; Epifani, E.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Girela, F.; Herranz, M.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Benini, E.; Casini, L.; Cherubini, G.; Coradini, A.; Giovane, F.; Grün, E.; Gustafson, B.; Maag, C.; Weissmann, P. R. Bibcode: 1999AdSpR..24.1149B Altcode: Rosetta is one of the most ambitious missions planned by ESA for the beginning of the next millennium. It will explore from very close a comet nucleus along its trajectory up to perihelion. In the instrument complex forming the scientific payload, the GIADA (Grain Impact Analyser and Dust Accumulator) experiment is devoted to study the cometary dust flux evolution and grain dynamic properties. To achieve the required performances and the expected scientific return, GIADA has been designed as a multi-sensor instrument. It is able to detect grain passage by laser light scattering measurement, particle momentum through piezoelectric transducers and mass flux by means of quartz crystal microbalances. In this paper we describe the technical solutions and performances which have been reached on the development models of GIADA Title: Preface Authors: Lamy, Philippe; Thomas, Nicolas Bibcode: 1999AdSpR..24.1079L Altcode: No abstract at ADS Title: The panoramic camera of the ROSETTA mission: performances of prototype 3D microcameras Authors: Beauvivre, S.; Lamy, P.; Nguyen-Trong, T.; Reynaud, J. -L. Bibcode: 1999AdSpR..24.1105B Altcode: We present the evaluation of the performances of microcameras prototypes manufactured in 3D packaging technology developed for the panoramic camera of the lander for the ROSETTA cometary mission. Two different prototypes were tested, one manufactured by Alcatel and the other by CSEM. A specific laboratory setup with cooling capabilities was implemented to perform electrical, mechanical and photometric tests in the temperature range -90°C to +20°C. Our results show that the photometric performances are nominal and do not change in this temperature range. The reduced size of the camera, associated with its operating mode, leads to a transient thermal behaviour that does not affect the cameras properties when operated at temperatures below -55°C. We show that this kind of miniature camera is suitable to deep space missions like ROSETTA, provided specific cares are taken in the electrical and mechanical designs. Title: The GIADA experiment for ROSETTA mission to comet 46P/wirtanen: Design and performances Authors: Bussoletti, E.; Colangeli, L.; Lopez Moreno, J. J.; Epifani, E.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Girela, F.; Herranz, M.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Benini, E.; Casini, L.; Cherubini, G.; Coradini, A.; Giovane, F.; Grün, E.; Gustafson, B.; Maag, C.; Weissmann, P. R. Bibcode: 1999AdSpR..24.1139B Altcode: No abstract at ADS Title: Exploration of small bodies in the solar system: I. Initial results and future prospects : proceedings of the B1.1 Symposium of COSPAR Scientific Commission B which was held during the Thirty-second COSPAR Scientific Assembly, Nagoya, Japan, 12-19 July, 1998 Authors: Lamy, P. L.; Thomas, N. Bibcode: 1999AdSpR..24.....L Altcode: No abstract at ADS Title: Experiments for in-situ monitoring of dust environments in the Solar System. Authors: Colangeli, L.; Bussoletti, E.; López-Moreno, J. J.; Epifani, E.; Esposito, F.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Morales, R.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Ruiz-Falco, A.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Coradini, A.; Giovane, F.; Gruen, E.; Gustafson, B.; Maag, C.; Weissman, P. R. Bibcode: 1999BAAS...31R1119C Altcode: No abstract at ADS Title: CME observed continuously from the lower corona to the far corona (CME's onset on November 3, 1997). Authors: Delannée, C.; Delaboudinière, J. -P.; Lamy, P. Bibcode: 1999joso.proc..162D Altcode: A program of observations with EIT on board SOHO, is to observe the whole sun surface in 195 Å, i.e. in a Fe XII emission line, every 17 minutes. The very beginning of some CMEs is observed. The authors correlate each Fe XII observation with He II, Hα and coronagraph observations on 97/11/03 and 97/11/04. They found that three prominences were ejected, and that an active region produced 4 ejections. The ejections are dark bubbles propagating above the sun limb, and dimmings propagating on the solar surface in Fe XII. They each produced an associated CME. One CME was not correlated to a Fe XII low corona event. Maybe, this CME had its origin behind the limb. The prominence gave a quite slow CME, i.e. about 50 km s-1 and the active region produced some quite fast CMEs, i.e. about 300 km s-1. Title: Hubble Space Telescope observations of the nucleus and inner coma of comet 19P/1904 Y2 (Borrelly) Authors: Lamy, Philippe L.; Toth, Imre; Weaver, Harold A. Bibcode: 1998A&A...337..945L Altcode: The nucleus of comet 19P/Borrelly was detected using the Planetary Camera (WFPC2) of the Hubble Space Telescope (HST). During the time of our observations, the comet was 0.62 AU from the Earth, 1.40 AU from the Sun, and had a solar phase angle of 38°. The high spatial resolution of the HST images allowed us to discriminate clearly between the signal from the nucleus and that from the coma. The lightcurve of the nucleus indicates that it is a highly elongated body rotating with a synodic period of 25.0+/-0.5 hr. Assuming that the nucleus has a geometric albedo of 4% and is a prolate spheroid with a rotational axis pointing in the direction determined by Sekanina (1979), we derive that its semi-axes are 4.4+/-0.3 km and 1.8+/-0.15 km. The corresponding fractional active area of $() sim$8 {%} suggests a moderately active comet. The highly anisotropic coma is dominated by a strong sunward fan, and the dust production rate exhibited signs of temporal variability throughout our observations. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, under NASA contract NAS 5-26555 Title: Joint Nancay Radioheliograph and LASCO Observations of Coronal Mass Ejections - II. The 9 July 1996 Event Authors: Pick, M.; Maia, D.; Kerdraon, A.; Howard, R.; Brueckner, G. E.; Michels, D. J.; Paswaters, S.; Schwenn, R.; Lamy, P.; Llebaria, A.; Simnett, G.; Lanzerotti, L. J.; Aurass, H. Bibcode: 1998SoPh..181..455P Altcode: The development of a coronal mass ejection on 9 July 1996 has been analyzed by comparing the observations of the LASCO/SOHO coronagraphs with those of the Nancay radioheliograph. The spatial and temporal evolution of the associated radioburst is complex and involves a long-duration continuum. The analysis of the time sequence of the radio continuum reveals the existence of distinct phases associated with distinct reconnection processes and magnetic restructuring of the corona. Electrons are accelerated in association with these reconnection processes. An excellent spatial association is found between the position and extension of the radio source and the CME seen by LASCO. Furthermore, it is shown that the topology and evolution of the source of the radio continuum involve successive interactions between two systems of loops. These successive interactions lead to magnetic reconnection, then to a large scale coronal restructuring. Thus electrons of coronal origin may have access to the interplanetary medium in a large range of heliographic latitudes as revealed by the Ulysses observations. Title: Comet 9P/Tempel 1 Authors: Lamy, P. Bibcode: 1998IAUC.7000....3L Altcode: 1998IAUC.7000C...1L; 1998IAUC.7000S...1L P. Lamy, Laboratoire d'Astronomie Spatiale, and his team report the detection of the nucleus of comet 9P with the Hubble Space Telescope (+ WFPC2) on 1997 Dec. 31 at Delta = 3.53 AU and r = 4.48 AU: "The slightly incomplete lightcurve indicates an elongated body having semi-axes a = 3.9 and b = 2.8 km (assuming a geometric albedo of 0.04) and a rotational period of about 25 hr. No coma was detected." Title: Geomagnetic storms caused by coronal mass ejections (CMEs): March 1996 through June 1997 Authors: Brueckner, G. E.; Delaboudiniere, J. -P.; Howard, R. A.; Paswaters, S. E.; St. Cyr, O. C.; Schwenn, R.; Lamy, P.; Simnett, G. M.; Thompson, B.; Wang, D. Bibcode: 1998GeoRL..25.3019B Altcode: (1) All but two geomagnetic storms with Kp ≥ 6 during the operating period (March 1996 through June 1997) of the Large Angle Spectroscopic Coronagraph (LASCO) experiment on the Solar and Heliospheric Observatory (SOHO) spacecraft can be traced to Coronal Mass Ejections (CMEs). (2) These geomagnetic storms are not related to high speed solar wind streams. (3) The CMEs which cause geomagnetic effects, can be classified into two categories: Halo events and toroidal CMEs. (4) The CMEs are accompanied by Coronal Shock Waves as seen in the Extreme Ultraviolet Imaging Telescope (EIT) Fe XII images. (5) Some CMEs are related to flares, others are not. (6) In many cases, the travel time between the explosion on the Sun and the maximum geomagnetic activity is about 80 hours. Title: The Solar Minimum Active Region 7978, Its X2.6/1B Flare, CME, and Interplanetary Shock Propagation of 9 July 1996 Authors: Dryer, M.; Andrews, M. D.; Aurass, H.; DeForest, C.; Galvin, A. B.; Garcia, H.; Ipavich, F. M.; Karlický, M.; Kiplinger, A.; Klassen, A.; Meisner, R.; Paswaters, S. E.; Smith, Z.; Tappin, S. J.; Thompson, B. J.; Watari, S. I.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Lamy, P.; Mann, G.; Arzner, K.; Schwenn, R. Bibcode: 1998SoPh..181..159D Altcode: The first X-class flare in four years occurred on 9 July 1996. This X2.6/1B flare reached its maximum at 09:11 UT and was located in active region 7978 (S10° W30°) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio observations of the type II shock, and GOES disk-integrated soft X-ray flux during an extended period that included energy build-up in this active region. Title: The nucleus and inner coma of Comet 46P/Wirtanen Authors: Lamy, P. L.; Toth, I.; Jorda, L.; Weaver, H. A.; A'Hearn, M. Bibcode: 1998A&A...335L..25L Altcode: We report the detection of the nucleus of comet 46P/Wirtanen from analysis of images taken with the Planetary Camera (WFPC2) of the Hubble Space Telescope (HST) on 28 August 1996. The high spatial resolution (a WFPC2 pixel projects to 50 km at the distance of the comet) allowed us to separate the signal of the nucleus from that of the coma and to determine the Landolt V and R magnitudes of the nucleus. Assuming a spherical body with a geometric albedo of 0.04 and a phase coefficient of 0.04 mag/deg, we derived a radius of 0.60+/-0.02 km. The color of the nucleus is moderately red with a gradient of 10{%} per 1000 Angstroms at optical wavelengths. From the lightcurve data we derived a rotational period of 6.0+/-0.3 hr and find that the ratio of the semi-axes of the assumed ellipsoidal body must satisfy a/b >= 1.2. From an analysis of the dust coma, we derived that Afrho is 23 cm and that the dust production rate is 4 kg sec(-1) . Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-26555 Title: Joint Nançay Radioheliograph and LASCO Observations of Coronal Mass Ejections - I. The 1 July 1996 Event Authors: Maia, D.; Pick, M.; Kerdraon, A.; Howard, R.; Brueckner, G. E.; Michels, D. J.; Paswaters, S.; Schwenn, R.; Lamy, P.; Llebaria, A.; Simnett, G.; Aurass, H. Bibcode: 1998SoPh..181..121M Altcode: The development of a coronal mass ejection on 1 July 1996 has been analyzed by comparing the observations of the LASCO/SOHO coronagraph with those of the Nançay radioheliograph. This comparison brings new insight and very useful diagnosis for the study of CME events. It is shown that the initial instability took place in a small volume located above an active region and that the occurrence of short radio type III bursts implies a triggering process due to magnetic field interactions. The subsequent spatial and temporal evolution of the radio emission strongly suggests that the large scale structure becomes unstable within the first minute of the event. Title: LASCO observations of an Earth-directed coronal mass ejection on May 12, 1997 Authors: Plunkett, S. P.; Thompson, B. J.; Howard, R. A.; Michels, D. J.; St. Cyr, O. C.; Tappin, S. J.; Schwenn, R.; Lamy, P. L. Bibcode: 1998GeoRL..25.2477P Altcode: Coronal mass ejections (CMEs) that occur near the center of the solar disk are most likely to impact Earth. Detection of such events as ‘halos’ in white-light coronagraphs has been somewhat controversial in recent years. We present observations from the LASCO coronagraphs on SOHO that provide convincing evidence of the detection of an Earth-directed CME on May 12, 1997. The event began at about 04:35 UT and propagated outwards from the Sun with a projected speed of around 250 km s-1. Using some reasonable assumptions about the geometry of the CME, we estimate the true speed to be around 600 km s-1. The onset of the event in LASCO is coincident (to within measurement uncertainties) with an eruptive event detected in extreme ultraviolet observations of the solar disk by the SOHO EIT. This is the first reported observation of a halo CME at projected distances greater than 10 R⊙, with a clearly identifiable solar origin. We discuss the possibility that at least some of the enhanced brightness observed by LASCO may be due to a compressional wave propagating in the corona. Title: Space exploration of the outer space solar system and cometary nuclei. Proceedings. B0.2 and B0.6 Symposia of COSPAR Scientific Commission B held during the Thirty-first COSPAR Scientific Assembly, Birmingham (UK), 14 - 21 Jul 1996. Authors: Matson, D. L.; Thomas, N.; Lamy, P. Bibcode: 1998AdSpR..21.....M Altcode: This is a collection of six papers. Current and planned exploration activities for the giant planets, Jupiter and Saturn are discussed. The volume starts with an account of the results of the mass spectrometer measurements of the Jovian atmosphere. This is a key result from the instrumented probe which the Galileo spacecraft delivered to Jupiter. Next are results of measurements on the location of the Jovian magnetopause and bow shock. Then, several theoretical investigations explore effects in the magnetospheres of Jupiter and Saturn. Finally, data from the Pioneer and Voyager spacecraft are used to model some of the properties of energetic electrons in the Saturnian magnetosphere. Title: Origin of Streamer Material in the Outer Corona Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Walters, J. H.; Brueckner, G. E.; Howard, R. A.; Michels, D. J.; Lamy, P. L.; Schwenn, R.; Simnett, G. M. Bibcode: 1998ApJ...498L.165W Altcode: We investigate the nature and origin of the outward-moving density inhomogeneities (``blobs'') detected previously with the Large Angle and Spectrometric Coronagraph on the Solar and Heliospheric Observatory. The blobs are concentrated around the thin plasma layer that surrounds the heliospheric current sheet and that constitutes the outer streamer belt; they represent only a small, fluctuating component of the total density within the plasma sheet. As noted before in Sheeley et al., blobs are characterized by low speeds and are continually emitted from the elongated tips of helmet streamers at 3-4 Rsolar from Sun center. We suggest that both the blobs and the plasma sheet itself represent closed-field material injected into the solar wind as a result of footpoint exchanges between the stretched helmet-streamer loops and neighboring open field lines. The plasma sheet is thus threaded by newly reconnected, open magnetic field lines, which lend the white-light streamer belt its filamentary appearance. Since in situ observations at 1 AU show that the slow wind (with speeds below 500 km s-1) spreads over an angular extent much greater than the <~3° width of the plasma sheet, we deduce that a major component of this wind must originate outside the helmet streamers (i.e., from just inside coronal holes). Title: Comet 55P/Tempel-Tuttle Authors: Lamy, P.; Znojil, V.; Biver, N. Bibcode: 1998IAUC.6851....2L Altcode: 1998IAUC.6851R...1L; 1998IAUC.6851B...1L P. Lamy, Laboratoire d'Astronomie Spatiale, and his team report the detection of the nucleus of comet 55P with the Hubble Space Telescope (+ WFPC2) on Jan. 9 at Delta = 0.46 AU: "After removing the faint contribution of the coma to the central pixels, the magnitude of the nucleus was R = 16.62, showing no variation over 10 hr. For a geometric albedo of 0.04 and a phase coefficient of 0.04 mag/deg, the mean effective radius is 1.8 km, the largest uncertainty coming from the phase law. The red color of the nucleus is characterized by a normalized reflectivity gradient of 0.16 percent/nm." Visual m_1 estimates: Mar. 1.75 UT, 8.7 (V. Znojil, Brno, Czech R., 25x100 binoculars); 18.24, 9.7: (N. Biver, Honolulu, HI, 0.26-m reflector). Title: Discrimination of point-like objects in astronomical images using surface curvature. Authors: Llebaria, A.; Lamy, P.; Malburet, P. Bibcode: 1998A&AS..127..587L Altcode: We present a method for the discrimination of point-like objects in astronomical images using surface curvature. The principal curvatures k_1 and k_2 are calculated using a local quadric approximation to the log of the intensity of the original image. The analysis of the (k_1, k_2) diagram allows to easily separate various shapes and to establish a criterion for discrimination. A mask is then generated and the invalid pixels are replaced by a local, pyramidal interpolation using a non-linear, multiresolution method. We present two applications, the discrimination and removal of stars from the dust tail of comet P/Halley observed while it was crossing the Milky Way, and the removal of cosmic ray impacts from images of the solar corona obtained with a space-coronagraph. Title: Reconstruction of the Electron Density Distribution in the Solar Corona Based on LASCO C2 Observations Authors: Gabryl, J. -R.; Cugnon, P.; Lamy, P. Bibcode: 1998ASPC..155..361G Altcode: 1998sasp.conf..361G No abstract at ADS Title: DFA-the dust flux analyzer for the Rosetta orbiter Authors: Lamy, P.; Perruchot, S.; Reynaud, J. -L.; Leese, M. R.; McDonnell, J. A. M.; Green, S. F.; Busoletti, E.; Colangeli, L.; Fulle, M.; Rotundi, A.; Giovane, F.; Gustafson, B.; Perrin, J. -M. Bibcode: 1998AdSpR..21.1557L Altcode: We describe the scientific objectives, the design concept and the implementation of the Dust Flux Analyser (DFA) for the ESA Rosetta mission. DFA is designed to detect individual dust particles in order to study their physical and dynamical properties as a function of time and of orbital position, to monitor the spatial distribution of the dust production and correlate it with the nucleus emission sites and to analyse gas-dust interactions and the evolution of the coma. The instrument is composed of three detectors with a common electronic box. The Velocity Measurement System (VMS) will measure the velocity of the incoming dust particles and the dust detector (MOM), its momentum. A separate deposition system (DEP) composed of three quartz microbalances will monitor the cometary dust flux in three directions. DFA will be able to detect dust particles in the size range 5-1000 μm and velocity range 0.1-150 m.s^-1. Required resources are a mass of 4.9 kg, a power of 3.6 W to 16.7 W and a telemetry of 50 to 512 kBits per hour depending upon the operating modes. Title: OSIRIS-the optical, spectroscopic and infrared remote imaging system for the Rosetta Orbiter Authors: Thomas, N.; Keller, H. U.; Arijs, E.; Barbieri, C.; Grande, M.; Lamy, P.; Rickman, H.; Rodrigo, R.; Wenzel, K. -P.; A'Hearn, M. F.; Angrilli, F.; Bailey, M.; Barucci, M. A.; Bertaux, J. -L.; Brieß, K.; Burns, J. A.; Cremonese, G.; Curdt, W.; Deceuninck, H.; Emery, R.; Festou, M.; Fulle, M.; Ip, W. -H.; Jorda, L.; Korth, A.; Koschny, D.; Kramm, J. -R.; Kührt, E.; Lara, L. M.; Llebaria, A.; Lopez-Moreno, J. J.; Marzari, F.; Moreau, D.; Muller, C.; Murray, C.; Naletto, G.; Nevejans, D.; Ragazzoni, R.; Sabau, L.; Sanz, A.; Sivan, J. -P.; Tondello, G. Bibcode: 1998AdSpR..21.1505T Altcode: The scientific objectives, design, and implementation of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) for the International Rosetta Mission are described. The instrument comprises two camera systems with a common electronics box. A narrow angle camera will provide high resolution images of the structure and morphology of the nucleus of a comet. A wide angle camera with high straylight rejection and dynamic range will be used to investigate the innermost coma and the emission process at the surface of the comet. An infrared imaging system, which dramatically enhances the scientific return has been included in the narrow angle camera at little extra cost. Title: Time domain analysis of polar plumes observed with LASCO-C2 and EIT Authors: Llebaria, A.; Lamy, P.; Deforest, Ce.; Koutchmy, S. Bibcode: 1998ESASP.421...87L Altcode: 1998sjcp.conf...87L No abstract at ADS Title: The panoramic cameras for the Champollion and Roland Cometary Surface Science Packages Authors: Lamy, P.; Bibring, J. -P.; Nguyen-Trong, T.; Soufflot, A.; Boit, J. L.; Dohlen, K. Bibcode: 1998AdSpR..21.1581L Altcode: We describe the scientific objectives, the design concept and the implementation of the panoramic cameras which are parts of the In-situ Imaging System (ISIS) and of the Roland Imaging System (ROLIS) for respectively the Champollion and Roland Surface Science Packages of the ESA Rosetta mission. Both instruments will characterize the cometary surface near the landing site, from the anchoring legs at spatial scales not achievable by the orbiter cameras, to the local horizon. ROLIS-P will further monitor the cometary activity and the resulting changes in the local topography. Both instruments are composed of several identical miniaturized cameras incorporating a 1024 x 1024 pixels, frame transfer CCD and a wide-angle optics having a field-of-view of 70 deg. ISIS-P includes six such cameras to record the full panorama without any mechanical rotation plus three additional ones to offer stereoscopic capability in three of the six fields-of-view. ROLIS-P takes advantage of the rotating capability of the Roland probe and is therefore limited to a single pair of (stereo) cameras. The camera heads with associated electronics will be integrated in a single module using the technology of three-dimensional packaging of electronic components resulting in highly compact, extremely lightweight units. Both instruments will provide unique information on the cometary surface at a spatial scale of 2 mm. Title: Development of Coronal Mass Ejections and Association with Interplanetary Events Authors: Pick, M.; Maia, D.; Howard, R.; Thompson, B.; Lanzerotti, L. J. L.; Bothmer, V.; Lamy, P. Bibcode: 1997ESASP.415..195P Altcode: 1997cpsh.conf..195P No abstract at ADS Title: Evidence of an Erupting Magnetic Flux Rope: LASCO Coronal Mass Ejection of 1997 April 13 Authors: Chen, J.; Howard, R. A.; Brueckner, G. E.; Santoro, R.; Krall, J.; Paswaters, S. E.; St. Cyr, O. C.; Schwenn, R.; Lamy, P.; Simnett, G. M. Bibcode: 1997ApJ...490L.191C Altcode: A coronal mass ejection (CME) observed by LASCO exhibits evidence that its magnetic field geometry is that of a flux rope. The dynamical properties throughout the fields of view of C2 and C3 telescopes are examined. The results are compared with theoretical predictions based on a model of solar flux ropes. It is shown that the LASCO observations are consistent with a two-dimensional projection of a three-dimensional magnetic flux rope with legs that remain connected to the Sun. Title: White-Light Coronal Mass Ejections: A New Perspective from LASCO Authors: St. Cyr, O. C.; Howard, R. A.; Simnett, G. M.; Gurman, J. B.; Plunkett, S. P.; Sheeley, N. R.; Schwenn, R.; Koomen, M. J.; Brueckner, G. E.; Michels, D. J.; Andrews, M.; Biesecker, D. A.; Cook, J.; Dere, K. P.; Duffin, R.; Einfalt, E.; Korendyke, C. M.; Lamy, P. L.; Lewis, D.; Llebaria, A.; Lyons, M.; Moses, J. D.; Moulton, N. E.; Newmark, J.; Paswaters, S. E.; Podlipnik, B.; Rich, N.; Schenk, K. M.; Socker, D. G.; Stezelberger, S. T.; Tappin, S. J.; Thompson, B.; Wang, D. Bibcode: 1997ESASP.415..103S Altcode: 1997cpsh.conf..103S No abstract at ADS Title: Circumstellar grains: radiation pressure and temperature distribution Authors: Lamy, P. L.; Perrin, J. -M. Bibcode: 1997A&A...327.1147L Altcode: The ratio beta of the radiation pressure force to the gravitational attraction is calculated for circumstellar grains. Eleven stars of various spectral type are considered and their spectral flux compiled from available data sometimes supplemented by appropriate models. The materials composing the grains are a silicate (obsidian), organic materials (ice tholin, poly-HCN), graphite and glassy carbon. The radius of the grain extends from 0.005 to 25 mu m. beta exceeds 1 for submicronic grains around the hottest stars with the exception of the obsidian grains. As far as the coldest stars are concerned, the results are not so clear and depend sharply on the illuminating stars as well as the nature of the material of the solid particles. Their temperatures are also studied and two examples are given for obsidian and graphite grains of radii 0.01, 0.1, 1 and 10 mu m. Our results are of interest for thin stellar shells such as exo-zodiacal clouds and for the inner region of dense shells where multiple scattering effects are not taking place. Title: LASCO Observations of Disconnected Magnetic Structures Out to Beyond 28 Solar Radii During Coronal Mass Ejections Authors: Simnett, G. M.; Tappin, S. J.; Plunkett, S. P.; Bedford, D. K.; Eyles, C. J.; St. Cyr, O. C.; Howard, R. A.; Brueckner, G. E.; Michels, D. J.; Moses, J. D.; Socker, D.; Dere, K. P.; Korendyke, C. M.; Paswaters, S. E.; Wang, D.; Schwenn, R.; Lamy, P.; Llebaria, A.; Bout, M. V. Bibcode: 1997SoPh..175..685S Altcode: Two coronal mass ejections have been well observed by the LASCO coronagraphs to move out into the interplanetary medium as disconnected plasmoids. The first, on July 28, 1996, left the Sun above the west limb around 18:00 UT. As it moved out, a bright V-shaped structure was visible in the C2 coronagraph which moved into the field-of-view of C3 and could be observed out to beyond 28 solar radii. The derived average velocity in the plane of the sky was 110 ± 5 km s-1 out to 5 solar radii, and above 15 solar radii the velocity was 269 ± 10 km s-1. Thus there is evidence of some acceleration around 6 solar radii. The second event occurred on November 5, 1996 and left the west limb around 04:00 UT. The event had an average velocity in the plane of the sky of ∼54 km s-1 below 4 R⊙, and it accelerated rapidly around 5 R⊙ up to 310 ± 10 km s-1. In both events the rising plasmoid is connected back to the Sun by a straight, bright ray, which is probably a signature of a neutral sheet. In the November event there is evidence for multiple plasmoid ejections. The acceleration of the plasmoids around a projected altitude of 5 solar radii is probably a manifestation of the source surface of the solar wind. Title: First View of the Extended Green-Line Emission Corona At Solar Activity Minimum Using the Lasco-C1 Coronagraph on SOHO Authors: Schwenn, R.; Inhester, B.; Plunkett, S. P.; Epple, A.; Podlipnik, B.; Bedford, D. K.; Eyles, C. J.; Simnett, G. M.; Tappin, S. J.; Bout, M. V.; Lamy, P. L.; Llebaria, A.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D. Bibcode: 1997SoPh..175..667S Altcode: The newly developed C1 coronagraph as part of the Large-Angle Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft has been operating since January 29, 1996. We present observations obtained in the first three months of operation. The green-line emission corona can be made visible throughout the instrument's full field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured from Sun center). Quantitative evaluations based on calibrations cannot yet be performed, but some basic signatures show up even now: (1) There are often bright and apparently closed loop systems centered at latitudes of 30° to 45° in both hemispheres. Their helmet-like extensions are bent towards the equatorial plane. Farther out, they merge into one large equatorial `streamer sheet' clearly discernible out to 32 R⊙. (2) At mid latitudes a more diffuse pattern is usually visible, well separated from the high-latitude loops and with very pronounced variability. (3) All high-latitude structures remain stable on time scales of several days, and no signature of transient disruption of high-latitude streamers was observed in these early data. (4) Within the first 4 months of observation, only one single `fast' feature was observed moving outward at a speed of 70 km s-1 close to the equator. Faster events may have escaped attention because of data gaps. (5) The centers of high-latitude loops are usually found at the positions of magnetic neutral lines in photospheric magnetograms. The large-scale streamer structure follows the magnetic pattern fairly precisely. Based on our observations we conclude that the shape and stability of the heliospheric current sheet at solar activity minimum are probably due to high-latitude streamers rather than to the near-equatorial activity belt. Title: The Relationship of Green-Line Transients to White-Light Coronal Mass Ejections Authors: Plunkett, S. P.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Paswaters, S. E.; St. Cyr, O. C.; Socker, D. G.; Wang, D.; Simnett, G. M.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Tappin, S. J.; Schwenn, R.; Lamy, P. L.; Llebaria, A. Bibcode: 1997SoPh..175..699P Altcode: We report observations by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft of three coronal green-line transients that could be clearly associated with coronal mass ejections (CMEs) detected in Thomson-scattered white light. Two of these events, with speeds >25 km s-1, may be classified as `whip-like' transients. They are associated with the core of the white-light CMEs, identified with erupting prominence material, rather than with the leading edge of the CMEs. The third green-line transient has a markedly different appearance and is more gradual than the other two, with a projected outward speed <10 km s-1. This event corresponds to the leading edge of a `streamer blowout' type of CME. A dark void is left behind in the emission-line corona following each of the fast eruptions. Both fast emission-line transients start off as a loop structure rising up from close to the solar surface. We suggest that the driving mechanism for these events may be the emergence of new bipolar magnetic regions on the surface of the Sun, which destabilize the ambient corona and cause an eruption. The possible relationship of these events to recent X-ray observations of CMEs is briefly discussed. Title: MHD Interpretation of LASCO Observations of a Coronal Mass Ejection as a Disconnected Magnetic Structure Authors: Wu, S. T.; Guo, W. P.; Andrews, M. D.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Socker, D. G.; Dere, K. P.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J. Bibcode: 1997SoPh..175..719W Altcode: We present a qualitative and quantitative comparison of a single coronal mass ejection (CME) as observed by LASCO (July 28-29, 1996) with the results of a three-dimensional axisymmetric time-dependent magnetohydrodynamic model of a flux rope interacting with a helmet streamer. The particular CME considered was selected based on the appearance of a distinct `tear-drop' shape visible in animations generated from both the data and the model. Title: EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Kreplin, R. W.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Delaboudinière, J. P.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Chauvineau, J. P.; Marioge, J. P.; Defise, J. M.; Jamar, C.; Rochus, P.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert, W.; Clette, F.; Cugnon, P.; Van Dessel, E. L.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M. Bibcode: 1997SoPh..175..601D Altcode: We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 100 km s-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200-400 km s-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 104 km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb. Title: Estimating the Size of Hale-Bopp's Nucleus Authors: Weaver, H. A.; Lamy, P. L. Bibcode: 1997EM&P...79...17W Altcode: A variety of independent methods have been used to estimate the size of the nucleus of comet Hale-Bopp. Several groups have analyzed optical and infrared images of the comet and claim to detect the signature of the nucleus, despite the presence of a strong coma. A detection of the nucleus was also claimed during mm- and cm-wave observations of Hale-Bopp shortly before perihelion. A team of observers detected the occultation of a star by the nucleus of Hale-Bopp in October 1996. The maximum observed gas production rate of the comet near perihelion can be used to place a lower limit on the size of the nucleus. This paper critically reviews the many different methods used to constrain the size of Hale-Bopp's nucleus. All of the techniques are affected by systematic errors that can be difficult to quantify precisely. Nevertheless, the available evidence strongly suggests that the nucleus of Hale-Bopp has an effective radius of at least 15 km and is probably in the range 20 35 km. Thus, the prodigious gas and production rates from this comet are naturally explained by its unusually large size. Title: Origin and Evolution of Coronal Streamer Structure During the 1996 Minimum Activity Phase Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Kraemer, J. R.; Rich, N. B.; Andrews, M. D.; Brueckner, G. E.; Dere, K. P.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Paswaters, S. E.; Socker, D. G.; Wang, D.; Lamy, P. L.; Llebaria, A.; Vibert, D.; Schwenn, R.; Simnett, G. M. Bibcode: 1997ApJ...485..875W Altcode: We employ coronal extrapolations of solar magnetograph data to interpret observations of the white-light streamer structure made with the LASCO coronagraph in 1996. The topological appearance of the streamer belt during the present minimum activity phase is well described by a model in which the Thomson-scattering electrons are concentrated around a single, warped current sheet encircling the Sun. Projection effects give rise to bright, jet-like structures or spikes whenever the current sheet is viewed edge-on multiple spikes are seen if the current sheet is sufficiently wavy. The extreme narrowness of these features in polarized images indicates that the scattering layer is at most a few degrees wide. We model the evolution of the streamer belt from 1996 April to 1996 September and show that the effect of photospheric activity on the streamer belt topology depends not just on the strength of the erupted magnetic flux, but also on its longitudinal phase relative to the background field. Using flux transport simulations, we also demonstrate how the streamer belt would evolve during a prolonged absence of activity. Title: Measurements of Flow Speeds in the Corona Between 2 and 30 R⊙ Authors: Sheeley, N. R.; Wang, Y. -M.; Hawley, S. H.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A. Bibcode: 1997ApJ...484..472S Altcode: Time-lapse sequences of white-light images, obtained during sunspot minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph on the Solar and Heliospheric Observatory, give the impression of a continuous outflow of material in the streamer belt, as if we were observing Thomson scattering from inhomogeneities in the solar wind. Pursuing this idea, we have tracked the birth and outflow of 50-100 of the most prominent moving coronal features and find that:

1. They originate about 3-4 R⊙ from Sun center as radially elongated structures above the cusps of helmet streamers. Their initial sizes are about 1 R⊙ in the radial direction and 0.1 R⊙ in the transverse direction.

2. They move radially outward, maintaining constant angular spans and increasing their lengths in rough accord with their speeds, which typically double from 150 km s-1 near 5 R⊙ to 300 km s-1 near 25 R⊙.

3. Their individual speed profiles v(r) cluster around a nearly parabolic path characterized by a constant acceleration of about 4 m s-2 through most of the 30 R⊙ field of view. This profile is consistent with an isothermal solar wind expansion at a temperature of about 1.1 MK and a sonic point near 5 R⊙.

Based on their relatively small initial sizes, low intensities, radial motions, slow but increasing speeds, and location in the streamer belt, we conclude that these moving features are passively tracing the outflow of the slow solar wind. Title: Using LASCO Observations to Infer Solar Wind Flow Near the Sun Authors: Sheeley, N. R., Jr.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Koomen, M. J.; Paswaters, S. E.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; St Cyr, O. C.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A. Bibcode: 1997SPD....28.0301S Altcode: 1997BAAS...29..907S We have continued to track individual coronal features as they become detached from helmet streamers and move outward from the Sun. The composite speed profile for 50-100 features has a parabolic shape with a constant acceleration of about 4 m/s(2) over the 2-30 R field of view. This well-determined speed profile contrasts strongly with the nearly uniform scatterplot obtained for about 50 nominal coronal mass ejections (CMEs), and suggests that these detached bits of coronal ``debris'' are passively tracing the speed of the slow solar wind. We have also begun the more difficult task of tracking outflow along polar plumes and will summarize these results as of June 1997. Title: The Solar Minimum X2. 6/1B Flare and CME of 9 July 1996; Part 1: Solar Data Authors: Andrews, M. D.; Dryer, M.; Aurass, H.; DeForest, C.; Kiplinger, A. L.; Meisner, R.; Paswaters, S. E.; Smith, Z.; Tappipn, S. J.; Thompson, B. J.; Watari, S. I.; Lamy, P.; Mann, G.; Schwenn, R.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.; Koomen, M. Bibcode: 1997ESASP.404..169A Altcode: 1997cswn.conf..169A No abstract at ADS Title: Intercomparison between UVCS/WLC and LASCO/C2 measured polarized brightness Authors: Romoli, M.; Biesecker, D.; Benna, C.; Fineschi, S.; Lamy, P. L.; Llebaria, A.; Kohl, J. L.; Noci, G. Bibcode: 1997ESASP.404..637R Altcode: 1997cswn.conf..637R No abstract at ADS Title: Characterisation of Polar Plumes from LASCO-C2 Images in Early 1996 Authors: Lamy, P.; Liebaria, A.; Koutchmy, S.; Reynet, P.; Molodensky, M.; Howard, R.; Schwenn, R.; Simnett, G. Bibcode: 1997ESASP.404..487L Altcode: 1997cswn.conf..487L No abstract at ADS Title: The April 7, 1997 Event: LASCO and Nancay Radioheliograph Joint Observations Authors: Maia, D.; Pick, M.; Howard, R.; Brueckner, G. E.; Lamy, P. Bibcode: 1997ESASP.404..539M Altcode: 1997cswn.conf..539M No abstract at ADS Title: The Solar Minimum X2. 6/1B Flare and CME of 9 July 1996; Part 2: Propagation Authors: Dryer, M.; Andrews, M. D.; Aurass, H.; DeForest, C.; Karlicky, M.; Kiplinger, A.; Klassen, A.; Meisner, R.; Ipavich, F. M.; Galvin, A. B.; Paswaters, S. E.; Smith, Z.; Tappin, S. J.; Thompson, B. J.; Watari, S. -I.; Michels, D. J.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Lamy, P.; Mann, G.; Arzner, K.; Schwenn, R. Bibcode: 1997ESASP.404..331D Altcode: 1997cswn.conf..331D No abstract at ADS Title: Acceleration of Coronal Mass Ejections in the Upper Corona: Observations from Lasco/Soho Authors: Simnett, G. M.; Tappin, S. J.; Brueckner, G. E.; Howard, R. A.; Lamy, P.; Michels, D. J.; Schwenn, R. Bibcode: 1997ICRC....1..181S Altcode: 1997ICRC...25a.181S No abstract at ADS Title: Dynamical Evolution of a Coronal Mass Ejection (CME) to Magnetic Cloud: A Preliminary Analysis of the January 6-10, 1997 CME Observed by LASCO/SOHO Authors: Wu, S. T.; Guo, W. P.; Michels, D. J.; Andrews, M. D.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Moses, J. D.; Socker, D. G.; Dere, K. P.; Bougeret, Jean-Louis; Lamy, P. L.; Schwenn, R.; Simnett, G. M. Bibcode: 1997ESASP.404..739W Altcode: 1997cswn.conf..739W No abstract at ADS Title: In-Orbit Calibration of the Distortion of the SOHO/LASCO-C2 Coronagraph Authors: Llebaria, A.; Aubert, S.; Lamy, P.; Plunkett, S. Bibcode: 1997ASPC..125..435L Altcode: 1997adass...6..435L This paper describes distortion calibration procedures for the SOHO/LASCO-C2 Coronagraph, based on in-orbit data and extensive image processing methods. It addresses specific problems of externally occulted coronagraphs (obstructed center of field-of-view, strong vignetting, and presence of stray light) and limitations inherent to space-based instrumentation (cosmic rays and limited number of reference points). Title: EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker, D. G.; Delaboudiniere, J. P.; Hochedez, J. F.; Lamy, P. L.; Schwenn, R.; Simnett, G. M.; Defise, J. M.; Catura, R. C. Bibcode: 1997IAUJD..19E..18D Altcode: We present the first observations of the initiation of a corona mass ejection (CME) seen on the disk of the Sun. Observations with the EIT and LASCO experiments on SOHO show that the CME starts in a small volume and is associated with slow motions of prominence material. At about the same time, a shock wave is created that travels out into the corona at a velocity of 400 km s^{-1} ahead of an eruptive prominence. This shock wave is clearly the event that is later seen as a classical CME when observed in the coronagraph above 1.5 solar radii. Although the CME clearly starts in a small region, a chain of activity near the limb may also be associated with this event. Title: The Streamer Belt at Solar Minimum: Simulation and Comparison with LASCO-C2 Images Authors: Vibert, D.; Lamy, P.; Liebaria, A. Bibcode: 1997ESASP.404..713V Altcode: 1997cswn.conf..713V No abstract at ADS Title: Reconstruction of the electron density distribution in the solar corona based on LASCO C2 observations Authors: Cugnon, P.; Gabryl, J. -R.; Lamy, P. Bibcode: 1997IAUJD..19E..17C Altcode: From total intensities images provided by the C2 coronagraph with orange filter (visible range) we try to reconstruct the large scale electron density in the corona, using a model based on the assumption of an axisymmetric corona, which allows for a separation between the angular and radial descriptions. This method has been successfully applied to the eclipse observations of 1991 and 1994 and gave results up to 3.1 solar radii. In the case of LASCO C2, the range extends from 2.5 to 7 solar radii, where the F-corona gets more and more predominant. In order to extract the K-corona signal, accurate values of the F-corona must be subtracted from total intensities. An iterative process based on pre-existing tables is applied for this purpose. We also trace the evolution of the global structure of the corona during a solar rotation. Title: Electronic Densities in Coronal Holes from LASCO-C2 Images Authors: Lamy, P.; Quemerais, E.; Llebaria, A.; Bout, M.; Howard, R.; Schwenn, R.; Simnett, G. Bibcode: 1997ESASP.404..491L Altcode: 1997cswn.conf..491L No abstract at ADS Title: Joint Radioheliograph and LASCO Observations of Coronal Mass Ejections Authors: Pick, M.; Maia, D.; Howard, R.; Kerdraon, A.; Brueckner, G. E.; Lamy, P.; Schwenn, R.; Aurass, H. Bibcode: 1997ESASP.404..601P Altcode: 1997cswn.conf..601P No abstract at ADS Title: Visibility of Earth-Directed Coronal Mass Ejections Authors: Michels, D. J.; Howard, R. A.; Koomen, M. J.; Plunkett, S.; Brueckner, G. E.; Lamy, Ph.; Schwenn, R.; Biesecker, D. A. Bibcode: 1997ESASP.404..567M Altcode: 1997cswn.conf..567M No abstract at ADS Title: Analysis of a High Latitude Slow CME with Travelling Ejecta Authors: Boulade, S.; Delanné, C.; Koutchmy, S.; Lamy, P.; Llebaria, A.; Howard, R.; Schwenn, R.; Simnett, G. Bibcode: 1997ESASP.404..217B Altcode: 1997cswn.conf..217B No abstract at ADS Title: Synthetic Images of the Solar Corona from Octree Representation of 3-D Electron Distributions Authors: Vibert, D.; Llebaria, A.; Netter, T.; Balard, L.; Lamy, P. Bibcode: 1997ASPC..125..230V Altcode: 1997adass...6..230V Empirical and theoretical modeling of 3-D structures in the solar corona is confronted by the tremendous amount of data needed to represent phenomena with a large dynamic range both in size and magnitude, and with a rapid temporal evolution. Octree representation of the 3-D coronal electron distribution offers the right compromise between resolution and size, allowing computation of synthetic images of the solar corona. Title: The infrared spectrum of comet C/1995 O1 (Hale-Bopp) at 4.6 AU from the Sun. Authors: Crovisier, J.; Brooke, T. Y.; Hanner, M. S.; Keller, H. U.; Lamy, P. L.; Altieri, B.; Bockelee-Morvan, D.; Jorda, L.; Leech, K.; Lellouch, E. Bibcode: 1996A&A...315L.385C Altcode: Comet C/1995 O1 (Hale-Bopp) was observed on 27 April 1996 with the ISOPHOT instrument of ISO when it was at 4.6 AU from the Sun. The 2.5-12μm spectrum was recorded at low resolution. We present here the preliminary results of this observation. The 2.5-5μm spectrum shows emission in the CO_2_ ν_3_ band. The CO_2_ production rate is about 1.3x10^28^ s^-1^. The 6-12μm spectrum shows thermal emission at a colour temperature of 162K (6-8μm range) and a strong silicate band around 10μm, with a narrow feature at 11.2μm indicative of crystalline silicates. Title: STEREO: a solar terrestrial event observer mission concept Authors: Socker, Dennis G.; Antiochos, S. K.; Brueckner, Guenter E.; Cook, John W.; Dere, Kenneth P.; Howard, Russell A.; Karpen, J. T.; Klimchuk, J. A.; Korendyke, Clarence M.; Michels, Donald J.; Moses, J. Daniel; Prinz, Dianne K.; Sheely, N. R.; Wu, Shi T.; Buffington, Andrew; Jackson, Bernard V.; Labonte, Barry; Lamy, Philippe L.; Rosenbauer, H.; Schwenn, Rainer; Burlaga, L.; Davila, Joseph M.; Davis, John M.; Goldstein, Barry; Harris, H.; Liewer, Paulett C.; Neugebauer, Marcia; Hildner, E.; Pizzo, Victor J.; Moulton, Norman E.; Linker, J. A.; Mikic, Z. Bibcode: 1996SPIE.2804...50S Altcode: A STEREO mission concept requiring only a single new spacecraft has been proposed. The mission would place the new spacecraft in a heliocentric orbit and well off the Sun- Earth line, where it can simultaneously view both the solar source of heliospheric disturbances and their propagation through the heliosphere all the way to the earth. Joint observations, utilizing the new spacecraft and existing solar spacecraft in earth orbit or L1 orbit would provide a stereographic data set. The new and unique aspect of this mission lies in the vantage point of the new spacecraft, which is far enough from Sun-Earth line to allow an entirely new way of studying the structure of the solar corona, the heliosphere and solar-terrestrial interactions. The mission science objectives have been selected to take maximum advantage of this new vantage point. They fall into two classes: those possible with the new spacecraft alone and those possible with joint measurements using the new and existing spacecraft. The instrument complement on the new spacecraft supporting the mission science objectives includes a soft x-ray imager, a coronagraph and a sun-earth imager. Telemetry rate appears to be the main performance determinant. The spacecraft could be launched with the new Med-Lite system. Title: Spectroscopic Observations of Comet C/1995 O1 (Hale-Bopp) with the Infrared Space Observatory Authors: Crovisier, J.; Bockelee-Morvan, D.; Lellouch, E.; Brooke, T. Y.; Hanner, M. S.; Keller, H. U.; Jorda, L.; Altieri, B.; Leech, K.; Lamy, P. L. Bibcode: 1996DPS....28.0921C Altcode: 1996BAAS...28.1092C Comet C/1995 O1 (Hale-Bopp) was selected to be observed in the target-of-opportunity comet program of the Infrared Space Observatory (ISO). The first results of the spectroscopic part of this program are reported here. Comet Hale-Bopp was observed on 27 April 1996 with the ISOPHOT instrument of ISO when it was at 4.6 AU from the Sun. The 2.5--12 mu m spectrum was recorded at low resolution. The 2.5--5. mu m spectrum shows emission in the CO_2 nu_3 band at 4.26 mu m. Upper limits for other molecular bands (H_2O, CO, CH_3OH) are in agreement with observations of these species at other wavelengths. The CO_2 production rate is about 1.3 x 10(28) molecules s(-1) . This is about one third of the H_2O and CO production rates observed at other wavelengths, which indicates that carbon dioxide is an important constituant of cometary volatiles at this heliocentric distance. The 6--12 mu m spectrum shows thermal emission at a colour temperature of 162 K (6--8 mu m range) and a strong silicate band around 10 mu m, with a narrow feature at 11.2 mu m indicative of crystalline silicates. There is no indication of differences of composition for grains in comets Hale-Bopp and Halley. Comet Hale-Bopp is to be observed at higher spectral resolution with the SWS and LWS instruments of ISO in September-October 1996. Title: Comet 46P/Wirtanen Authors: Lamy, P. Bibcode: 1996IAUC.6478....2L Altcode: P. Lamy, Laboratoire d'Astronomie Spatiale, and his team report the apparent detection of the nucleus of 46P with the Hubble Space Telescope (+ WFPC2) on Aug. 28: "After removing the small contribution of the (stable) coma to the central pixels, the R magnitude of the nucleus was found to vary from 21.6 to 21.9 over time intervals of 1.5 hr, though a clear rotational pattern is not evident. For a geometric albedo of 0.04, the mean effective radius is 0.58 km." Title: HST Observations of the Nuclei of Comets 45P/Honda-Mrkos-Pajdusakova, 22P/Kopff, and 46P/Wirtanen Authors: Lamy, P. L.; A'Hearn, M. F.; Toth, I.; Weaver, H. A. Bibcode: 1996DPS....28.0804L Altcode: 1996BAAS...28.1083L Comet 45P/Honda-Mrkos-Pajdusakova (H-M-P) was observed with the Planetary Camera (WFPC2) of the Hubble Space Telescope on two consecutive days, 4 and 5 February 1996, at which time the geocentric distance was 0.17 AU (1 pixel projected to a distance of 5.6 km at the comet) and the phase angles were 93 and 88 deg, respectively. Although much fainter than expected, the nucleus was clearly detected superimposed on a very weak coma. The accuracy of the determination of the size of the nucleus is limited primarily by the unknown phase law for such large phase angles. Assuming a constant phase coefficient of 0.04 mag/deg and a geometric albedo of 0.04 near 675 nm, we derived an effective diameter of 0.70 km. Comet 22P/Kopff was observed on 18 July 1996 at a geocentric distance of 0.57 AU (1 pixel projected to a distance of 19 km at the comet) and a phase angle of 3 deg. Over the 11 hour time interval spanned by the observations, we see a variation in the nuclear magnitude that corresponds to changes in the effective nuclear diameter from 3.30 to 3.84 km, using the same assumptions as above for the albedo and phase law. The uncertainty in the nuclear diameter is determined primarily by the systematic error in estimating the contribution of the coma to the peak pixel intensity. The light curve data are being used to determine the rotation period for the nucleus. Comparison of our derived sizes with published gas production rates for comets H-M-P and Kopff indicate that the fractional active surface area is ~ 10% for each nucleus. Comet 46P/Wirtanen will be observed on 28 August 1996, and we expect to report preliminary results on its size. Title: LASCO Observations of the 03Feb96 Streamer Blow-out Authors: Andrews, M. D.; Korendyke, C. M.; Koomen, M. J.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C. St.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunkett, S.; Simnett, G. M. Bibcode: 1996AAS...188.3716A Altcode: 1996BAAS...28..880A The C2 and C3 telescopes on the Large Angle Spectrometric Coronograph (LASCO) have recorded images of a Streamer Blow-out which occured on 03Feb96. We will present a series of images produces by combining data from the 2 coronographs. These images show a rapid evolution of the coronal streamer belt over projected distances of 2 to 20 solar radii. The streamer belt shows a dramatic brightening, which is seen to propagate outward. A bubble-like structure is seen to move away from the Sun and expand. At the end of this event, the equatorial corona is significantly less bright than prior to the event. Title: LASCO Observations of the Solar Corona to 32 Rsun Authors: Cook, J. W.; Koomen, M. J.; Korendyke, C. M.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Morrill, J. S.; Moses, J. D.; Socker, D. G.; Paswaters, S. E.; Wang, D.; Moulton, N. E.; Cyr, O. C. St.; Andrews, M. D.; Schwenn, R.; Podlipnik, B.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J.; Plunkett, S.; Biesecker, D. A. Bibcode: 1996AAS...188.3717C Altcode: 1996BAAS...28..880C The Large Angle Spectrometric Coronagraph (LASCO) was launched on board the SOHO satellite on 2 December 1995. The C3 externally-occulted coronagraph of LASCO observes the solar corona over a field from 3.7-32 R_ ⊙, using a 1024x1024 CCD detector with a pixel size corresponding to 56 arc sec. Observations can be made using color filters ranging from the blue (420-520 nm) to the near-IR (860-1050 nm), and through polarizing filters. We report on early observations of the solar corona out to 32 Rsun. Title: Preliminary Photometric Calibration of LASCO C3 Coronagraph Images using Pre-Flight Laboratory Images of Standard Sources and In-Flight Images of Standard Stars Authors: Korendyke, C. M.; Koomen, M. J.; Andrews, M. D.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunkett, S.; Simnett, G. M. Bibcode: 1996AAS...188.3621K Altcode: 1996BAAS...28..876K The C3 coronagraph is a wide field (+/-8.0 degrees), externally occulted, white light coronagraph. The instrument is one of three coronagraphs comprising the Large Angle Spectrometric COronagraph (LASCO) experiment mounted on the Solar Heliospheric Observatory satellite. The satellite was launched on Dec. 2, 1996; C3 observations began in early Jan. 1997. The coronagraph optical train includes a set of five broadband color filters mounted in a wheel. Prior to flight, an image was obtained through each color filter of a well characterized, rear-illuminated, opal glass diffusing screen. The C3 in-flight images, in addition to the coronal structures, also contain several hundred bright stars. We present a comparison of the photometric calibration derived from standard stars with the laboratory measurements. The resulting calibration is then used to examine color variations in the white light corona over the field of view. The LASCO experiment was developed by a scientific consortium of members from NRL (USA), MPAe (Germany), LAS (France) and U. Birmingham (United Kingdom). Title: Optical designs for the Rosetta narrow-angle camera Authors: Dohlen, Kjetil; Saisse, Michel; Claeysen, Genevieve; Lamy, Philippe L.; Boit, Jean-Lucien Bibcode: 1996OptEn..35.1150D Altcode: Optical designs for the Rosetta narrow-angle camera (NAC) and its UV spectrograph are presented. The NAC requires a 600 mm focal length system of focal ratio f/7 imaging a square field of width 2.3 deg onto a square detector array 2048 pixels wide. A cartographic method has been used to search for flat-field, three-mirror anastigmats (TMA) with the required geometrical constraints and at least one spherical surface; the use of spherical surfaces reduces fabrication cost and complexity and facilitates alignment. Two such systems are described, one with a spherical secondary, the other with a spherical tertiary. A deterministic alignment method is outlined where alignment defects are calculated from measurements of image position and Zernike wavefront coefficients. For the spectrograph, an all-reflecting, Thevenin-type concentric spectrograph has been designed. This design offers excellent image quality both spectrally and spatially along a long slit and it is compact and easily accommodated. Title: A coronal optical imager for a solar probe Authors: Lamy, P.; Koutchmy, S. Bibcode: 1996AdSpR..17c..95L Altcode: 1996AdSpR..17...95L A Coronal Optical Imager (COI) can make a significant contribution to a solar probe, for instance, by detecting the faintest plasma and magnetic structures, by analyzing the He/H ratio and the cool plasma component and by observing possible sources of dust near the Sun. We describe an instrument which combines the capability of EUV, UV and visible imaging as well as visible polarimetry, and propose two versions respectively adapted to a spinning and a 3-axis stabilized probes. Title: Observations of Comet P/Faye 1991 XXI with the Planetary Camera of the Hubble Space Telescope Authors: Lamy, P. L.; Toth, I.; Grün, E.; Keller, H. U.; Sekanina, Z.; West, R. M. Bibcode: 1996Icar..119..370L Altcode: Comet P/Faye 1991 XXI (1991 n) was observed with the planetary camera (PC) of the Hubble Space Telescope (HST) between October 29 and November 21, 1991, when its geocentric distance was in the range 0.62-0.67 AU. The resulting high resolution-a single PC pixel projected to a distance of ∼20 km at the comet-made it possible to clearly discriminate the nucleus and to study the dust coma within ∼100 km from the nucleus. The spherical aberration which affected the early operation of the HST has severely complicated the analysis and image restoration using the Richardson-Lucy method has failed to give satisfactory results. The coma is dominated by the point spread function (PSF) of the nucleus up to a radial distance of ∼100 km and cannot be recovered. Beyond, it is affected by the spherical aberration up to approximately 750 km and was analyzed by comparison with a grid of models convolved with appropriate PSFs. Beyond 750 km, it remains unaffected and can be studied directly. From the outer to the innermost regions, the coma presents an elongated shape which may be explained either by an active source on the nucleus or, more likely, by a projection effect of the dust tail. If this second interpretation is correct, then the temporal evolution of the comet is very slow and smooth, suggesting an extended source of dust on the nucleus. The dust production rate, corrected for the projection effect of the tail, amounts to 125 kg sec-1. Title: Summary Remarks Authors: Lamy, Ph. L. Bibcode: 1996ASPC..104..527L Altcode: 1996IAUCo.150..527L; 1996pcdi.conf..527L No abstract at ADS Title: An Optical Instrument to Characterize Individual Dust Particles Authors: Giovane, F.; Gustafson, B. A. S.; Lamy, Ph. L. Bibcode: 1996ASPC..104..247G Altcode: 1996pcdi.conf..247G; 1996IAUCo.150..247G No abstract at ADS Title: Laboratory Measurements of Light Scattering by Dust Particles Authors: Combet, Pp.; Lamy, Ph. L. Bibcode: 1996ASPC..104..409C Altcode: 1996pcdi.conf..409C; 1996IAUCo.150..409C No abstract at ADS Title: Observations of the comet Hyakutake by the LASCO coronagraph on the SOHO satellite. Authors: Andrews, M. D.; Paswaters, S. E.; Brueckner, G. E.; Korendyke, C. M.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Morril, J. S.; Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles, C. J.; Plunket, S.; Simnet, G. M. Bibcode: 1996BAAS...28.1195A Altcode: No abstract at ADS Title: Dust Flux Analyser experiment for the Rosetta mission Authors: Leese, M. R.; McDonnell, J. A. M.; Green, S. F.; Busoletti, E.; Clark, B. C.; Colangeli, L.; Crifo, J. F.; Eberhardt, P.; Giovane, F.; Grün, E.; Gustafson, B.; Hughes, D. W.; Jackson, D.; Lamy, P.; Langevin, Y.; Mann, I.; McKenna-Lawlor, S.; Tanner, W. G.; Weissman, P. R.; Zarnecki, J. C. Bibcode: 1996AdSpR..17l.137L Altcode: 1996AdSpR..17..137L We present the description of a design for a proposed Dust Flux Analyser for the Rosetta cometary mission. A concept first developed for the NASA/ESA Tempel II Rendezvous and Halley Intercept Mission /1/, the instrument is able to measure dust particle parameters and fluxes over a velocity range typical of emission from cometary surfaces. It would be mounted on the Rosetta Orbiter and would measure the variation in flux rate throughout all mission phases at the comet. The instrument would measure particle flux, velocity, momentum and density, shape and scattering properties. Title: Concepts for Dust Velocity Measurements on a Cometary Orbiter Authors: Perruchot, S.; Lamy, Ph. L.; Giovane, F.; Gustafson, B. A. S. Bibcode: 1996ASPC..104..255P Altcode: 1996IAUCo.150..255P; 1996pcdi.conf..255P No abstract at ADS Title: The Large Angle Spectroscopic Coronagraph (LASCO) Authors: Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Socker, D. G.; Dere, K. P.; Lamy, P. L.; Llebaria, A.; Bout, M. V.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J. Bibcode: 1995SoPh..162..357B Altcode: The Large Angle Spectroscopic Coronagraph (LASCO) is a three coronagraph package which has been jointly developed for the Solar and Heliospheric Observatory (SOHO) mission by the Naval Research Laboratory (USA), the Laboratoire d'Astronomie Spatiale (France), the Max-Planck-Institut für Aeronomie (Germany), and the University of Birmingham (UK). LASCO comprises three coronagraphs, C1, C2, and C3, that together image the solar corona from 1.1 to 30 R⊙ (C1: 1.1 - 3 R⊙, C2: 1.5 - 6 R⊙, and C3: 3.7 - 30 R⊙). The C1 coronagraph is a newly developed mirror version of the classic internally-occulted Lyot coronagraph, while the C2 and C3 coronagraphs are externally occulted instruments. High-resolution imaging spectroscopy of the corona from 1.1 to 3 R⊙ can be performed with the Fabry-Perot interferometer in C1. High-volume memories and a high-speed microprocessor enable extensive on-board image processing. Image compression by a factor of about 10 will result in the transmission of 10 full images per hour. Title: Comet 19P/Borrelly Authors: Lamy, P. Bibcode: 1995IAUC.6204....2L Altcode: P. Lamy, Laboratoire d'Astronomie Spatiale, Marseille, and his team report: "Using the Wide Field Planetary Camera 2 of the Hubble Space Telescope, we have detected a highly elongated nucleus rotat- ing with a synodic period of 24.7 hr. The prolate spheroid that gives the best fit to the nuclear-magnitude light curve has major and minor axes dimensions of 8.3 and 3.3 km, respectively, assuming a geometric albedo of 4 percent. We estimate that about 10 percent of the surface area is active." Title: Visible and Radio Observations of Comet 19P/Borrelly Authors: Bockelée-Morvan, D.; Biver, N.; Colom, P.; Crovisier, J.; Gérard, E.; Jorda, L.; Davies, J. K.; Dent, B.; Colas, F.; Despois, D.; Paubert, G.; Lamy, P. Bibcode: 1995DPS....27.3308B Altcode: 1995BAAS...27.1144B No abstract at ADS Title: HST Observations of the Nucleus of Comet 19P/Borrelly 1994 I Authors: Lamy, P. L.; Toth, I.; Weaver, H. A. Bibcode: 1995DPS....27.3315L Altcode: 1995BAAS...27.1145L No abstract at ADS Title: Temporal and Spatial Variations among the SL9 Fragments Authors: Weaver, H. A.; A'Hearn, M. F.; Arpigny, C.; Feldman, P. D.; Lamy, Ph.; Meech, K. J.; Noll, K. S.; Smith, T. E. Bibcode: 1995DPS....27.2016W Altcode: 1995BAAS...27Q1115W No abstract at ADS Title: The Hubble Space Telescope (HST) Observing Campaign on Comet Shoemaker- Levy 9 Authors: Weaver, H. A.; A'Hearn, M. F.; Arpigny, C.; Boice, D. C.; Feldman, P. D.; Larson, S. M.; Lamy, P.; Levy, D. H.; Marsden, B. G.; Meech, K. J.; Noll, K. S.; Scotti, J. V.; Sekanina, Z.; Shoemaker, C. S.; Shoemaker, E. M.; Smith, T. E.; Stern, S. A.; Storrs, A. D.; Trauger, J. T.; Yeomans, D. K.; Zellner, B. Bibcode: 1995Sci...267.1282W Altcode: The Hubble Space Telescope made systematic observations of the split comet P/Shoemaker-Levy 9 (SL9) (P designates a periodic comet) starting in July 1993 and continuing through mid-July 1994 when the fragments plunged into Jupiter's atmosphere. Deconvolutions of Wide Field Planetary Camera images indicate that the diameters of some fragments may have been as large as ~2 to 4 kilometers, assuming a geometric albedo of 4 percent, but significantly smaller values (that is, <1 kilometer) cannot be ruled out. Most of the fragments (or nuclei) were embedded in circularly symmetric inner comae from July 1993 until late June 1994, implying that there was continuous, but weak, cometary activity. At least a few nuclei fragmented into separate, condensed objects well after the breakup of the SL9 parent body, which argues against the hypothesis that the SL9 fragments were swarms of debris with no dominant, central bodies. Spectroscopic observations taken on 14 July 1994 showed an outburst in magnesium ion emission that was followed closely by a threefold increase in continuum emission, which may have been caused by the electrostatic charging and subsequent explosion of dust as the comet passed from interplanetary space into the jovian magnetosphere. No OH emission was detected, but the derived upper limit on the H_2O production rate of ~1027 molecules per second does not necessarily imply that the object was water-poor. Title: Direct detection of a cometary nucleus with the Hubble Space Telescope. Authors: Lamy, P. L.; Toth, I. Bibcode: 1995A&A...293L..43L Altcode: We report the unambiguous detection with the Planetary Camera of the Hubble Space Telescope of the nucleus of comet P/Faye 1991XXI during its last perihelion passage when it was at 0.6AU from the Earth. The high resolution of the HST allowed to discriminate the nucleus against the bright coma. The reduced V magnitude of the nucleus ranges between 15.5 and 15.9. Assuming a geometric albedo of 0.04, we found a rather spherical body with a mean radius of 2.68km. Title: Discrimination of Point-like Objects in Astronomical Images using Surface Curvature Authors: Llebaria, A.; Lamy, P.; Malburet, P. Bibcode: 1995ASPC...77..484L Altcode: 1995adass...4..484L A new method for the discrimination of point-like objects in astronomical images is presented. The method makes use of the surface curvature of the image, without any a priori knowledge of the shape of the point-like objects. Title: The LASCO database at LAS Authors: Mathieu, C.; Llebaria, A.; Lamy, P. Bibcode: 1995VA.....39..109M Altcode: In the framework of the SOHO (Solar Heliospheric Observatory) space mission of observation of the sun, conducted jointly by ESA and NASA, the Marseilles Laboratoire d'Astronomie Spatiale (LAS) contributes to the LASCO experiment — a study of the Solar corona — within an international consortium. Our laboratory participates in LASCO data reduction and is responsible for setting up a national database for French investigators. This database shall provide access to a huge amount of data, resulting from the collection and archiving of about 180 images per day (each image having a size between 2 and 4 Mo), during the whole mission duration (2 years; launch scheduled in September 1995). Of a relational structure (Sybase), the database is designed to store calibration images, from before and after launch, as well as mission images. It is intended to build interfaces to automatically load the new images into the database and into the IDL image processing software. Data will be made available to French astronomers through a WWW server which will provide compressed images, transferable via networks. The server will also offer interactive access to the data and will deliver the necessary information on how to retrieve the images and on the status of the ongoing mission. Tools developed at ESO, such as WDB or STARCAT, will be used appropriately. Title: The coronal aureole. Authors: Fang, Y.; Lamy, P. L.; Llebaria, A. Bibcode: 1995A&A...293..208F Altcode: We calculate the coronal aureole using the Fourier transform and we show that the outer corona significantly contributed to its value. We further propose a new, simple mathematical method which allows to derive the scattering function directly from two observational images taken successively during an eclipse. This method is successfully tested using different models of the scattering function. Title: Pulsars at 1 MeV: the Crab and PSR 1509-58. Authors: Combet, P.; Lamy, P. L. Bibcode: 1995AdSpR..15j..65C Altcode: 1995AdSpR..15R..65C The Compton Imaging Telescope COMPTEL observed at an early stage of the CGRO sky survey pulsed emission from the two classical γ-ray pulsars, Crab and Vela. Further efforts were necessary to detect one of the four new pulsars detected by the other CGRO instruments, namely PSR 1509-58. These are the only three pulsars detected so far at an energy of 1 MeV. In spite of the similarity of their timing parameters, the Crab pulsar and PSR 1509-58 display very different characteristics in their MeV emissions, observed by COMPTEL. Title: HST Observations of Comet P/Faye 1991 XXI Authors: Lamy, P. L.; Toth, I.; Grün, E.; Keller, H. U.; Sekanina, Z.; West, R. M. Bibcode: 1994BAAS...26.1552L Altcode: No abstract at ADS Title: Capabilities of the Cosmic Dust Analyser (CDA) for the Mission CASSINI Authors: Srama, R.; Grün, E.; Fechtig, H.; Jeßberger, E. K.; Pernicka, E.; Lura, F.; Möhlmann, D.; Wäsch, R.; Ahrens, J.; Auer, S.; Cruise, A. M.; Havnes, O.; Igenbergs, E.; Johnson, T. V.; Lamy, P.; Morfill, G. E.; Schwehm, G. H.; Svestka, J.; Tuzzolino, A. J.; Zook, H. A.; Cassini-Cda-Team Bibcode: 1994DPS....26.2109S Altcode: 1994BAAS...26.1142S No abstract at ADS Title: HST Monitoring of Comet P/Shoemaker-Levy 9 Authors: Weaver, H. A.; Noll, K. S.; Storrs, A. D.; Smith, T. E.; A'Hearn, M. F.; Arpigny, C.; Feldman, P. D.; Boice, D. C.; Stern, S. A.; Lamy, P. L.; Larson, S. M.; Levy, D. H.; Scotti, J. V.; Marsden, B. G.; Meech, K. J.; Shoemaker, C. S.; Shoemaker, E. M.; Sekanina, Z.; Trauger, J. T.; Yeomans, D. K.; Zellner, B. Bibcode: 1994DPS....26.0101W Altcode: 1994BAAS...26.1564W No abstract at ADS Title: IR Observations of the K and F Corona During the 1991 Eclipse Authors: Kuhn, J. R.; Lin, H.; Lamy, P.; Koutchmy, S.; Smartt, R. N. Bibcode: 1994IAUS..154..185K Altcode: No abstract at ADS Title: The potential of the dust grains of comet halley Authors: Lamy, P.; Lafon, J. -P. J.; Dumas, C. Bibcode: 1993AdSpR..13j.259L Altcode: 1993AdSpR..13..259L We calculate the electrostatic potential of silicate, graphite and carbon submicronic grains in the coma of comet P/Halley located at 1 AU from the Sun using the ``orbit-limited'' solution. The physical properties of the materials as well as the plasma parameters of the subsolar cometosheath are taken into account. We find that the potential lies between -3 and +4 volts in all cases, under likely conditions. It could be negative, between 0 and -10 volts, if the plasma would be a little more dense than usually admitted, as suggested by recent measures. Title: Status of the LASCO Instrument Development Program Authors: Moses, D.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Lamy, P.; Schwenn, R.; Simnett, G. M. Bibcode: 1993BAAS...25.1192M Altcode: No abstract at ADS Title: Absolute Photometry of the Dust Tail of Comet P/Halley Authors: Lamy, P.; Malburet, P. Bibcode: 1993LPICo.810..178L Altcode: No abstract at ADS Title: Observation of Comet Faye (1991n) with the Hubble Space Telescope Authors: Lamy, P.; Toth, I. Bibcode: 1993LPICo.810..179L Altcode: No abstract at ADS Title: Changing Properties of the Dust Coma of P/Halley: Implications for an Inhomogeneous Nucleus Authors: Lamy, P.; Cosmovici, C.; Schwarz, G. Bibcode: 1993LPICo.810..180L Altcode: No abstract at ADS Title: The Large Angle Spectroscopic Coronagraph (LASCO): visible light coronal imaging and spectroscopy. Authors: Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C.; Michels, D. J.; Socker, D. G.; Lamy, P.; Llebaria, A.; Maucherat, J.; Schwenn, R.; Simnett, G. M.; Bedford, D. K.; Eyles, C. J. Bibcode: 1992ESASP.348...27B Altcode: 1992cscl.work...27B The Large Angle Spectroscopic Coronagraph (LASCO) is a triple coronagraph being jointly developed for the SOlar and Heliospheric Observatory (SOHO) mission by the Naval Research Laboratory (USA), the Laboratoire d'Astronomie Spatiale (France), the Max Planck Institut für Aeronomie (Germany), and the University of Birmingham (UK). LASCO comprises three nested coronagraphs (C1, C2, and C3) that image the solar corona from 1.1 Rsun to 30 Rsun. Title: No Evidence of a Circumsolar Dust Ring from Infrared Observations of the 1991 Solar Eclipse Authors: Lamy, P.; Kuhn, J. R.; Lin, H.; Koutchmy, S.; Smartt, R. N. Bibcode: 1992Sci...257.1377L Altcode: During the past 25 years there have been many attempts to detect a possible dust ring around the sun, with contradictory results. Before the 1991 eclipse, infrared eclipse experiments used single-element detectors to scan the corona along the ecliptic for excess surface brightness peaks. The availability of relatively large-format infrared array detectors now provides a considerable observational advantage: two-dimensional mapping of the brightness and polarization of the corona with high photometric precision. The 1991 eclipse path included the high-altitude Mauna Kea Observatory, a further advantage to measure the corona out to large angular distances from the sun. Results are reported from an experiment conducted on Mauna Kea with a HgCdTe-array detector sensitive to wavelengths between 1 and 2.5 micrometers, using broad-band J, H, and K filters. Although the sky conditions were not ideal, the H- and K-band surface brightnesses clearly show the inhomogeneous structure in the K-corona and the elliptical flattening of the F-corona, but no evidence of a circumsolar, local dust component out to 15 solar radii. Title: LASCO - Large Angle Spectrometric Coronagraph for SOHO Authors: Howard, R. A.; Brueckner, G. E.; Dere, K. P.; Korendyke, C. M.; Koomen, M. J.; Michels, D. J.; Moses, D.; Socker, D. G.; Schwenn, R.; Inhester, B.; Lamy, P.; Maucherat, A.; Simnett, G. M.; Eyles, C. Bibcode: 1992AAS...180.3307H Altcode: 1992BAAS...24..781H No abstract at ADS Title: The Physics and Dynamics of Charged Dust Grains Authors: Lamy, P. Bibcode: 1992ibpd.conf..369L Altcode: No abstract at ADS Title: The Zodiacal Light Authors: Lamy, P. Bibcode: 1992iawi.conf..251L Altcode: No abstract at ADS Title: Laboratory Spectroscopy for ISO Report of the ISO Working-Group Authors: Encrenaz, T.; Crovisier, J.; D'Hendecourt, L.; Lamy, P.; Tully, J. A. Bibcode: 1992iawi.conf..141E Altcode: No abstract at ADS Title: Data Analysis of the HST Observations of Comet P/Faye Authors: Lamy, Ph.; Llebaria, A.; Adorf, H. -M. Bibcode: 1992ESOC...44..481L Altcode: 1992swhs.conf..481L No abstract at ADS Title: Photomultiplier for optically probing Comet Halley Authors: Giovane, Frank; Eichhorn, G.; McKisson, J.; Weinberg, J. L.; Weisenberger, Andrew; Lamy, P.; Llebaria, A.; Detaille, M; Levasseur-Regourd, A. C.; Le Blanc, J. M. Bibcode: 1991ApOpt..30.2579G Altcode: A low mass eight-color channel photopolarimeter was developed for the Giotto spacecraft. Utilizing the spin of the spacecraft, a multichannel plate photomultiplier, and a unique optical design, the instrument required no moving parts to measure color and linear polarization. The photopolarimeter collected data as the spacecraft passed through the coma of Comet Halley on March 13 and 14, 1986. This instrument's design, calibration, and reduction are discussed and some final results are presented. Title: Changing Properties of the Dust Coma of P/Halley: Implications for an Inhomogeneous Nucleus Authors: Lamy, P.; Cosmovici, C.; Schwarz, G. Bibcode: 1991LPICo.765..130L Altcode: No abstract at ADS Title: Electric Effects on Cometary Grains Authors: Lafon, J. P. J.; Lamy, Ph.; Bouzinac, C. Bibcode: 1991isrs.conf..213L Altcode: No abstract at ADS Title: Physical Properties of Cometary Dust Authors: McDonnell, J. A. M.; Lamy, P. L.; Pankiewicz, G. S. Bibcode: 1991ASSL..167.1043M Altcode: 1991cphe.conf.1043M; 1991IAUCo.116.1043M Prior to the 1986 apparition of Comet Halley, all attempts to determine the physical properties of cometary dust were limited to remote observations and the analysis of various particles captured by the earth's atmosphere. The in situ measurements made by the three spacecraft that passed within 10,000 km of the nucleus provided the first opportunity to investigate both the full size-range of particles and the complete process of dust production. Information on composition is derived through mass spectra and the scattering and emission of light from the grains, while the dynamics of the dust coma can be modeled from the three separate sets of measurements made over a period of eight days. Title: Future Observations of the F-Corona with the LASCO Coronagraph Space Experiment Authors: Lamy, P. L.; Llebaria, A.; Maucherat, A.; Koutchmy, S.; Giovane, F. Bibcode: 1991ASSL..173..191L Altcode: 1991IAUCo.126..191L; 1991oeid.conf..191L No abstract at ADS Title: Synthetic Maps of the Brightness and Polarization of the F-Corona Authors: Fang, Y.; Lamy, P. L.; Llebaria, A. Bibcode: 1991ASSL..173..195F Altcode: 1991oeid.conf..195F; 1991IAUCo.126..195F No abstract at ADS Title: The Optical Properties of Interplanetary Dust (invited Review) Authors: Lamy, P. L.; Perrin, J. M. Bibcode: 1991ASSL..173..163L Altcode: 1991oeid.conf..163L; 1991IAUCo.126..163L No abstract at ADS Title: On the Validity of Effective-Medium Theories in the Case of Light Extinction by Inhomogeneous Dust Particles Authors: Perrin, J. -M.; Lamy, P. L. Bibcode: 1990ApJ...364..146P Altcode: The application of Maxwell-Garnett and Bruggeman effective-medium theories to the problem of light scattering by inhomogeneous dust particles is investigated. It is shown that in the framework of classical electrodynamics these theories are not rigorously valid when applied to particles. Numerical computations of scattering using a discrete dipole approximation for very small grains composed of a matrix material with embedded inclusions are carried out, and the results are compared with results obtained using these effective-medium theories. It is shown that the application of these theories to the studies of the interactions of light with inhomogeneous dust particles is limited. Title: Optical linear polarization measurements of Comet Halley from the Giotto Halley Optical Probe Experiment. Authors: Weisenberger, A. G.; Giovane, F.; Eichhorn, G.; Lamy, P.; Llebaria, A. Bibcode: 1990BAAS...22..744W Altcode: No abstract at ADS Title: The dust tail of comet Halley. Authors: Lamy, P. L. Bibcode: 1990ch2..book....1L Altcode: 1990ch......2....1L Contents: 1. From early ages to the present day: an historical perspective of cometary dust tails. 2. From streamers to striae: a perspective on structures in cometary tails. 3. A good perspective on the dust tail of comet Halley. 4. The dust tail of comet Halley in 1986. 5. Photopolarimetric properties of the tail and its modelling. Title: The color of the zodiacal light and the size distribution and composition of interplanetary dust Authors: Perrin, J. -M.; Lamy, P. L. Bibcode: 1989A&A...226..288P Altcode: The color of the zodiacal light is studied in the general context of light scattered by dust particles. It is shown that the color is controlled by various mechanisms in a complex way. The spectral variation of the complex index of refraction, the size distribution function and the roughness of the dust grains all play a significant role in the color of the scattered light. It is also shown that the very geometrical conditions of observation of the zodiacal light result in a color effect which depends upon the elongation. Title: Optical properties of irregular interstellar grains. Authors: Perrin, J. M.; Lamy, P. L. Bibcode: 1989IAUS..135P.381P Altcode: In order to study the interaction of light with interstellar grains, the authors represent an irregular particle by a network of interacting dipoles whose polarizability is determined in a first approach by the Clausius-Mossoti relationship. Typically, 10000 dipoles are considered. In the case of spherical particles, the results from Mie theory are fully recovered. Title: Comet P/Halley at a heliocentric preperihelion distance of 2.6 AU - Jet activity and properties of the dust coma Authors: Lamy, P. L.; Malburet, P.; Llebaria, A.; Koutchmy, S. Bibcode: 1989A&A...222..316L Altcode: This paper presents an in-depth analysis of a high-resolution photograph of comet P/Halley obtained on September 12, 1985 when it was a heliocentric distance of 2.6 AU preperihelion. The coma has a diameter of 138,000 km and exhibits structures which are interpreted as three jets, one best seen in the outer part of the coma extending to 29000 km and the two others, in the inner part extending to about 7000 km. The integrated magnitude and radial profiles of the coma are given showing that the comet does not follow the simple steady-state, radial outflow model. By combining the photometric result with nearly simultaneous ultraviolet and infrared observations, it is found that the strong reddening in the ultraviolet gradually levels off in the visible as the color becomes neutral at 2 microns and blue beyond 3 microns. A geometric albedo at zero phase angle of 0.04 is obtained, as well as a dust production rate of 30 to 120 kgs. Title: Infrared properties of rough cometary grains Authors: Perrin, J. M.; Lamy, P. L. Bibcode: 1989AdSpR...9c.241P Altcode: 1989AdSpR...9..241P In order to study the interaction of light with cometary grains, we represent an irregular particle by a network of interacting dipoles whose polarizability is determined in a first approach by the Clausius-Mossiti relationship. Typically, 10000 dipoles are considered. In the case of spherical particles, the results from Mie theory are fully recovered. The main interest of this method is to study with a good accuracy the implications of surface roughness and/or inhomogeneities on optical properties in the infrared spectral range, particularly of the silicate emission features. Title: Optical properties of organic grains: Implications for interplanetary and cometary dust Authors: Lamy, Philippe L.; Perrin, Jean-Marie Bibcode: 1988Icar...76..100L Altcode: On the basis of the organic material "tholin" whose optical constants have been measured by B. N. Khare et al. (1984, Icarus 60, 127-137), we investigate the optical properties of tholin grains and find an original behavior, intermediate between dielectric and absorbing material. Solving for the interaction with the solar radiation field, we obtain the ratio β of the radiation pressure and gravitational forces and the temperature distribution. The temperature is a strong function of the size of the grains with the submicron grains much hotter than the blackbody. The presence of such an organic material in cometary dust looks very promising for explaining several "puzzling" observations such as the CN jets and the absence of the silicate emission feature at heliocentric distances beyond ⋍1.5 AU. Title: Light scattering of large rough particles application to cometary grains. Authors: Lamy, Philippe L.; Perrin, J. M. Bibcode: 1988ioch.rept..156L Altcode: While the electromagnetic field scattered by a spherical particle is classically obtained by the Helmholtz equation, the general case of an arbitrary particle may be investigated in the general framework of the interaction of a wave with a scattering potential. A wave function then satisfies the Schroedinger equation. The general solution of the Schroedinger equation is given. The main disadvantage of this approach are its restriction to large particles and its scalar nature preventing the calculation of the polarization. However, Perrin and Lamy have shown how to avoid the second limitation and retrieve a vectorial description. They proved that in the case of large spheres when the ad hoc assumptions are satisfied, the expression of the scattering amplitude may be approximated by an expansion series in partial waves, i.e., on a discrete basis. The analogy may be generalized, and the ratio of the two components for a rough particle obtained by taking the ratio of the reflectivities for the two directions of polarization. These reflectivities involve the simple and double reflections calculated following the method developed by Wolff for rough surfaces. The theory is further detailed. Title: Laboratory Measurements of Light Scattering by Dust Particles Authors: Bliek, P.; Lamy, P. Bibcode: 1988ASSL..149..253B Altcode: 1988ecda.book..253B No abstract at ADS Title: Etude de la dynamique du nuage zodiacal par la mesure du décalage Doppler. Authors: Lamy, P.; Koutchmy, S.; Bücher, A.; Robley, R. Bibcode: 1988jopl.conf..227L Altcode: At the Pic-du-Midi Observatory, the authors have started a program to observe the spectrum of the zodiacal light in the region of the b absorption lines of Mg I. They use a 1 m spectrograph with a holographic grating followed by a focal reducer to obtain a 19 Å/mm dispersion over the micro-channel plate camera. Calibrated spectra obtained with an exposure time of 10 minutes systematically show earth atmospheric emission lines attributed to both N I and OH. The temporal variability of these emissions prevents an accurate determination of the line profiles. Title: Observations et propriétés des poussières de la comète de Halley. Authors: Lamy, P.; Perrin, J. M.; Koutchmy, S.; Grün, E.; Llebaria, A.; Malburet, P. Bibcode: 1988jopl.conf..211L Altcode: The authors present the results of various observations and analysis of the dust grains of comet Halley. Title: Comet P/Halley - Implications of the mass distribution function for the photopolarimetric properties of the dust coma. Authors: Lamy, P. L.; Gruen, E.; Perrin, J. M. Bibcode: 1987A&A...187..767L Altcode: The dust particle fluences measured aboard the Vega (SP-1 and SP-2 impact sensors) and Giotto probes (DIDSY impact sensors) are analyzed to obtain the differential size distribution function of the dust in the coma of comet Halley. The brightness integral is then calculated for perfectly spherical (Mie scattering) and rough grains of various compositions. It is shown that the photopolarimetric observations rule out the dominating presence of weakly obsorbing silicates such as olivine but are compatible with rough moderately absorbing silicate grains having a density decreasing with radius and with rough graphite grains. A mixture of the two types gives in fact the best agreement with the observations. Title: The Dust Tail of Comet p/ Halley in 1986APR Authors: Lamy, P. L.; Pedersen, H.; Vio, R. Bibcode: 1987A&A...187..661L Altcode: Images of the dust tail of comet Halley were obtained with the ESO wide-field CCD camera during April 1986 with the Johnson B, V and R filters in polarized light. An analysis of selected images taken on April 6 and 11, processed for photometric analysis, is presented. Results are given for the absolute brightness, the color, the polarization and its variation with wavelength. Title: Compatibility of the in-situ mass distribution with photopolarimetricobservations of comet Halley. Authors: Lamy, P. L.; Grün, E.; Perrin, J. M. Bibcode: 1987ESASP.278..409L Altcode: No abstract at ADS Title: Similarity and diversity of the polarization of comets. Authors: Perrin, J. -M.; Lamy, P. L. Bibcode: 1987ESASP.278..411P Altcode: 1987dsc..proc..411P The polarization measurements of the dust coma of 10 comets including P/Halley were analyzed. Separation of the dust from the gas, emphasizing the value of the narrow-band and spectropolarimetric data, is outlined. Polarization curves are deduced, implying unambiguous differences in the physical properties of the cometary dust. The negative branch of polarization is discussed and intepreted as suggesting a rough surface for the grains. Title: Book Review: Interrelationship among circumstellar, interstellar, and planetary dust. Edited by Joseph A. Nuth III and Robert E. Stencel. NASA Conference Publication 2403, Proceedings of a workshop held at the Aspen Institute's Wye Plantation Conference Center, Wye, MD, February 27 to March 1, 1985 Authors: Lamy, Philippe L. Bibcode: 1987Icar...71..198L Altcode: No abstract at ADS Title: B00K-REVIEW - Properties and Interactions of Interplanetary Dust Authors: Giese, R. H.; Lamy, P. Bibcode: 1987Sci...236.1009G Altcode: No abstract at ADS Title: Night sky optical spectrum from a high altitude observatory. Authors: Louistisserand, S.; Bucher, A.; Koutchmy, S.; Lamy, P. Bibcode: 1987A&AS...68..539L Altcode: Night sky spectrum between 380 and 660 nm with effective spectral resolution of 0.2 nm is presented for evaluation of effects produced by the different sources of light including lights of urban origin. Numerous emission lines superposed on a continuum spectrum are identified. Title: Radiation pressure and temperature of Beta Pictoris circumstellar dust grains. Authors: Lamy, P. Bibcode: 1987BAAS...19..633L Altcode: No abstract at ADS Title: Book-Review - Properties and Interactions of Interplanetary Dust 85TH Colloquium I.A.U. / Marseille 1984 Authors: Giese, R. H.; Lamy, P. Bibcode: 1987ApL....25..270G Altcode: No abstract at ADS Title: Book-Review - Properties and Interactions of Interplanetary Dust - 85TH Colloquium of the I.A.U. Marseille - 1984 Authors: Giese, R. G.; Lamy, P. Bibcode: 1987ApL....25..265G Altcode: No abstract at ADS Title: Ground-Based Large-Scale Monochromatic Images of Comet Halley during the Giotto Flyby Authors: Koutchmy, S.; Lamy, P.; Loucif, M.; Malburet, P. Bibcode: 1986ESASP.250c..79K Altcode: 1986ehc3.conf...79K A wide-field camera (f = 135 mm) equipped with an image-tube was set up at the geophysical observatory of Tamanrasset during the first half of March. Monochromatic images were obtained in CN (390 nm), CO+ (426.3 nm) and in the continuum (582 nm), in March 14.19, a few hours after the Giotto flyby. Title: The Dust Tail of Comet Halley: Brightness, Colour, Polarisation Authors: Lamy, P.; Pedersen, H.; Vio, R. Bibcode: 1986ESASP.250b..69L Altcode: 1986ehc2.conf...69L Images of the dust tail of comet Halley were obtained with the ESO wide-field CCD camera during April 1986 with the Johnson B, V and R filters in polarized light. A preliminary analysis of selected images taken on April 6 and 11, processed for photometric analysis, is presented. Results are given for the absolute brightness, the color, the polarization and its variation with wavelength. Title: Comet Halley: Implications of the Impact Measurements for the Optical Properties of the Dust Authors: Lamy, P. L.; Perrin, J. -M. Bibcode: 1986ESASP.250b..65L Altcode: 1986ehc2.conf...65L The cumulative mass flux function obtained by VEGA-2 SP-2 impact instrument is used to calculate the brightness integral, for grains of various compositions, in the framework of Mie theory and of the authors' model for light scattering by rough grains. Polarization for large scattering angles and color in the ultra violet and visible range are also obtained. The results are compared with the space and ground-based observations. General indications on the properties of cometary dust are outlined. Title: Inner Coma Dust and Gas as a Function of Distance to the Nucleus: Measurements from Giotto Authors: Levasseur-Regourd, A. C.; Bertaux, J. -L.; Dumont, R.; Eichhorn, G.; Festou, M.; Giese, R. H.; Giovane, F.; Lamy, P.; Leblanc, J. M.; Llebaria, A.; Weinberg, J. L. Bibcode: 1986ESASP.250c.232L Altcode: No abstract at ADS Title: Early resolved structures in the coma of Comet Halley Authors: Dossin, F.; Guerin, P.; Koutchmy, S.; Lamy, P.; Malburet, P. Bibcode: 1986ESASP.250b.173D Altcode: 1986ehc2.conf..173D Three high-resolution photographs of comet Halley were obtained on September 12, 1985 with the Schmidt telescope operated by CNRS and Liège University at the Observatoire de Haute-Provence on hypered Kodak 2415 film and exposure times of 1 hour. The best image (FWHM of 2 arcsec) has been analyzed in order to deduce the 2-dimensional distribution of light presumably scattered by the dust. Two jet-like structures are present in the near nuclear region, one extending outward up to 15 arcsec. The total absolute magnitude has also been determined. Title: Book-Review - Properties and Interactions of Interplanetary Dust Authors: Giese, R. H.; Lamy, P.; Ingham, M. F. Bibcode: 1986Obs...106..130G Altcode: No abstract at ADS Title: Book-Review - Properties and Interactions of Interplanetary Dust Authors: Giese, R. H.; Lamy, P. Bibcode: 1986S&T....72Q..41G Altcode: No abstract at ADS Title: Volume scattering function and space distribution of the interplanetary dust cloud Authors: Lamy, P. L.; Perrin, J. -M. Bibcode: 1986A&A...163..269L Altcode: The Volume Scattering Function (VSF) and the spatial distribution of the interplanetary dust cloud are examined by inversion of the brightness integral of the F-corona and the zodiacal light. Intensity and polarization observations are used to produce functional representations in the plane of symmetry of the interplanetary cloud, in the meridian plane, and at selected ecliptic latitudes. A modified fan model is shown to be compatible with the brightness data at d = 1 and 0.3 AU, and indicates that the VSF and the local polarization depend upon the heliocentric distance of the observer, but are independent of the latitude. The variations of the VSF and the polarization with respect to the scattering angle may be explained by the preferential removal of absorbing grains as beta-meteoroids. Title: Inner Coma Dust and Gas in Comet Halley as a Function of Distance to the Nucleus: Measurements from GIOTTO Authors: Levasseur-Regourd, A. -C.; Bertaux, J. L.; Dumont, R.; Eichhorn, G.; Festou, M. C.; Giese, R. H.; Giovane, F.; Lamy, P.; Leblanc, J. M.; Llebaria, A.; Weinberg, J. L. Bibcode: 1986BAAS...18..790L Altcode: No abstract at ADS Title: Properties of Organic Interplanetary Grains Authors: Lamy, P. L.; Perrin, J. M. Bibcode: 1986BAAS...18..820L Altcode: No abstract at ADS Title: Book-Review - Properties and Interactions of Interplanetary Dust Authors: Giese, R. H.; Lamy, P. Bibcode: 1986Sci...232.1654G Altcode: No abstract at ADS Title: Optical probing of comet Halley from the Giotto spacecraft Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.; Festou, M.; Giese, R. H.; Giovane, F.; Lamy, P.; Le Blanc, J. M.; Llebaria, A.; Weinberg, J. L. Bibcode: 1986Natur.321..341L Altcode: The Halley optical probe experiment (HOPE) aboard the Giotto spacecraft has provided the first measurements of the optical properties of the dust and of some gaseous species (CN, C2, CO+ and OH) from inside the coma of comet Halley. The dust spatial distribution, inferred from sunlight scattering, obeys an r-2 law for distances from the nucleus r>=2,000 km. The more rapid increase of dust density with distance observed in the innermost coma probably reflects the presence of a jet, or a surge of activity within a few hours before closest approach. The CN and OH signals increase more slowly than the dust signals, but faster than predicted by a simple model (of solar-excited resonance fluorescence) for the distribution of these species1. This effect is probably caused in part by the dust contribution, as well as by the production from parent molecules of OH and CN in an excited state. Title: The Giotto optical probe experiment Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.; Festou, M.; Giese, R. H.; Giovane, F.; Lamy, P.; Llebaria, A.; Weinberg, J. L. Bibcode: 1986gmis.rept..187L Altcode: The Halley Optical Probe Experiment (HOPE) was designed to provide in-situ photopolarimetric data on the dust cloud and the gaseous atmosphere in Halley/s coma. The probe concept, instrumentation, and possibilities for cross-correlation between the HOPE results and those of other space and ground-based experiments are presented. The instrument was turned on successfully on 13 September 1985. Title: Periodic Comet Halley (1982i) Authors: Ney, E. P.; Knutson, A. G.; Wootten, Alyn; Loren, R.; Koutchmy, S.; Lamy, P. Bibcode: 1986IAUC.4161....1N Altcode: E. P. Ney and A. G. Knutson, University of Minnesota, report the following infrared magnitudes measured with a 26" diaphragm at the O'Brien Observatory: 1985 Dec. 12.08 UT, K = 6.8, L = 6.1, [8.6 micron] = -0.5, N = -1.8, [12.5 micron] = -1.9, [18 micron] = -3.3; Dec. 14.00, [8.6 micron] = 0.9, N = -0.8, [12.5 micron] = 0.0, [18 micron] = = -2.8; Dec. 25.05, J = 6.8, K = 7.1, L = 5.2, M = 3.1, [8.6 micron] = -0.5, N = -1.6, [12.5 micron] = -1.6, [18 micron] = -3.0; 1986 Jan. 1.0, N = -1.4, [12.5 micron] = -0.9; Jan. 7.9, H = 6.0, K = 6.1, L = 3.9, M = 1.2, [8.6 micron] = -1.5, N = -2.8, [12.5 micron] = -2.6, [18 micron] = -4.0. The silicate feature at 10 micron is ~ 0.5 mag above the continuum. A. Wooten, National Radio Astronomy Observatory, reports: "R. Loren, University of Texas, obtained spectra of P/Halley in the region of the P(2,1) line of protonated water (H3O+) at 307.19241 GHz on Jan. 6 with the 4.9-m telescope of the Millimeter Wave Observatory at Fort Davis. No emission was detected, rms(TR*) = 0.85 placing a preliminary upper limit of 5 x 10**-27 s**-1 for the H3O+ production rate. Receiver tuning was verified through observation of CHEOH at 307.16594 GHz in OMC-1." S. Koutchmy, Institut d'Astrophysique, Paris; and P. Lamy, Laboratoire d'Astronomie Spatiale, Marseilles, telex that 100 image-tube spectra (180 A/mm resolution, range 350-700 nm) were obtained with the Haute Provence Observatory's 0.8-m telescope during 1985 Dec. 10-15. CN emission was detected, extending up to 2 deg away from the sun, but no ions were noted until Dec. 12. From Dec. 13.8 UT onward the N2+ (0,0) line at 391.4 nm was seen in the vicinity of the coma and extending in the antisolar direction up to 2 deg. Observations with the Marly spectrograph (range 326-526 nm, dispersion 80 A/mm, slit width 50 micron, slit length projection 3'7, IIa-O hypered plates) on the 1.20-m f/6 telescope during 1985 Dec. 2.76-2.98 and 3.72-3.97 UT revealed CN, C2 and C3 (all well observed); N2+ (0,0) extending over 16"; CO+ (3,0) lines at 400.18 and 402.4 nm extending over 37" and 14", respectively; CO2+ (0,1) at 367.4 nm was suspected; numerous Fraunhofer absorption lines (including H and K and several Fe lines) were also noted. Photographs (hypered IIIa-J and 2415 emulsions) of the plasma tail with the 0.62-m f/3.5 and 0.30-m f/2 Schmidt telescopes during Dec. 3- 15 revealed an inner part (extending < 1 deg from the head) whose orientation oscillated about the antisolar direction with a maximum deviation of + 5P and a characteristic time of one to two days. Title: Cometary dust: observational evidences and properties. Authors: Lamy, P. L. Bibcode: 1986acm..proc..373L Altcode: Cometary dust in both the coma and the tail is observed by its scattered light and its thermal emission provided that they are carefully separated from the emission lines. Color, phase function, polarization and spectral signatures are the basic properties which help in characterizing the dust grains. There do not appear to be systematic differences among various comets as the reddening, the strong forward scattering and the polarization behavior appear to be wide-spread common features also shared by interplanetary dust grains. The interpretation of some of these features in terms of rough, slightly absorbing grains is discussed. Title: The Giotto Optical Probe Experiment. Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.; Festou, M.; Giese, R. H.; Giovane, F.; Lamy, P.; Llebaria, A.; Weinberg, J. L. Bibcode: 1986ESASP1070..187L Altcode: The Halley Optical Probe Experiment (HOPE) has been designed to provide in-situ photopolarimetric data on both the dust cloud and the gaseous atmosphere in Halley's coma. The Optical Probe's concept is presented here, together with a description of the instrumentation and the possibilities for cross-correlation between the HOPE results and those of other space and ground-based-experiments. The instrument was turned on successfully on 13 September 1985. Title: Periodic Comet Halley (1982i) Authors: Jewitt, D.; Meech, K.; Ricker, G.; Lamy, P.; Koutchmy, S.; Vial, J. C. Bibcode: 1985IAUC.4148....1J Altcode: D. Jewitt, K. Meech, and G. Ricker, Massachusetts Institute of Technology, communicate: "Observations from McGraw-Hill Observatory on Kitt Peak over 4 nights show variable structures in the inner coma of P/Halley. Images were taken through broad and narrowband interference filters using the MIT 'MASCOT' CCD camera on the 1.3-m telescope. Jet-like structures were observed in position angles 358 and 313 on Nov. 29 UT. The jets extended 10 000 km in the plane of the sky and had widths comparable to the atmospheric seeing. The jets were visible in both broad and narrowband continuum filters and are probably dust features. The jets showed no variation in position angle or brightness in an observing interval of > 3 hr but were absent on the preceding and following nights." Meech and Jewitt also report: "Observations of P/Halley with the Kitt Peak 0.61-/0.91-m Schmidt telescope (with baked IIIa-J plates and exposure times 30-60 min) show that extensive tail development has occurred within the past month. Observations on Nov. 6-9 showed only a transient, faint anti-solar tail (length 20' on Nov. 6.20) which faded in < 1 day. Observations on Dec. 4-8 show a persistent plasma tail (length > 2.5 deg) displaying a classical streamer morphology. We are able to follow knots, kinks, and streamers in the tail for up to 6 hr. The measured speeds of 3 tail knots are 190, 216, and 240"/hr (39, 45, and 50 +/- 5 km/s along the tail, km/s), considerably less than the solar wind speed but similar to the speeds measured in the tails of other comets. No evidence for acceleration of the features is seen. Two episodes of ray formation have been seen in 25 hr of observation; the rays form in ~ 1 hr and evolve over several hr, but fade in < 18 hr. The tail as a whole shows gross brightness changes from night to night. No dust tail is seen." P. Lamy, Laboratoire d'Astronomie Spatiale, Marseille, and S. Koutchmy, Institut d'Astrophysique, Paris, telex: "Four consecutive 1-hr-exposure IIIa-J hypered plates obtained between Dec. 6.79-6.96 UT by Koutchmy and J. C. Vial with the 0.62-m f/3 Schmidt telescope of Haute Provence Observatory show a disturbed, narrow, plasma tail of length > 2 deg. The tail's inner part deviates southward from the anti-solar direction by 4.8 +/- 0.7 deg; the outer part widens and nears the anti-solar direction. The point of bifurcation seems to move radially outward with time." Title: Zodiacal Light and the Spatial Density of Interplanetary Grains Authors: Lamy, P. L.; Perrin, J. M. Bibcode: 1985ASSL..119..239L Altcode: 1985piid.proc..239L; 1985IAUCo..85..239L Using the Lamy and Perrin (1980) model of light scattering by large, rough grains, the compatibility of the observed properties of the zodiacal light with models of the spatial density of interplanetary grains is investigated. The agreement is not yet satisfactory and probably calls for further revision of the density distribution function. The previous conclusion that submicronic grains gives a nonnegligible contribution is confirmed. Title: Ground-based observations of the dust emission from comet Halley Authors: Lamy, P. Bibcode: 1985AdSpR...5l.317L Altcode: 1985AdSpR...5..317L A preliminary analysis of the dust emission from comet Halley is presented based on large scale observations of its dust tail. Selected images obtained between February 22 and May 10, 1986 are compared to synchrone-syndyne graphs to infer the history of the dust production and the properties of the dust, at least qualitatively. Quantitative modeling of the dust tall has also been initiated and preliminary results are shown for the cases of isotropic and anisotropic (jet) dust production. Title: The F-Corona and the Circum-Solar Dust Evidences and Properties (ir) Authors: Koutchmy, S.; Lamy, P. L. Bibcode: 1985ASSL..119...63K Altcode: 1985IAUCo..85...63K; 1985piid.proc...63K This review deals with the main properties of the F-corona. Analysis of its morphology and photometry allows to derive a new axisymmetric, non-spherical model. Polarization, color and infra-red properties are further considered. The authors suggest the existence of a variable "local" component superimposed on a quasi-stationary "far" component. Title: In-situ photopolarimetric measurements of dust and gas in the coma of Halley's comet Authors: Levasseur-Regourd, A. -C.; Bertaux, J. -L.; Le Blanc, J. M.; Weinberg, J. L.; Giovane, F.; Dumont, R.; Festou, M.; Giese, R. H.; Lamy, P.; Llebaria, A. Bibcode: 1985AdSpR...5l.197L Altcode: 1985AdSpR...5..197L The Halley Optical Probe Experiment (HOPE) on board the Giotto spacecraft has provided the first in-situ measurements, both of the dust and of some gaseous species, from inside the coma of the comet. The instrument has already been described /1/, together with first results /2/. The purpose of this note is to show how optical measurements can lead to in-situ information, how those were obtained during the 13-14 march 1986 Halley fly-by, and what is the status of the data analysis. Title: Preliminary Results of a Dust Scattering Experiment Authors: Bliek, P.; Lamy, P. L.; Courtes, G. Bibcode: 1985ASSL..119..231B Altcode: 1985IAUCo..85..231B; 1985piid.proc..231B An experimental device of the nephelometer type for the study of the scattering properties of dust particles is presented. A fluidized bed generator produces a continuously flowing aerosol which is illuminated by either a He-Ne laser or a Xenon arc lamp with interference filters. The size of the dust particles ranges between 1 and 30 microns. The scattering properties of dust particles are measured in the two directions of polarization. The first results are presented. Title: Properties and interactions of interplanetary dust Authors: Giese, R. H.; Lamy, P. Bibcode: 1985ASSL..119.....G Altcode: 1985piid.proc.....G; 1985IAUCo..85.....G The conference presents papers on zodiacal light and F-coronal observations as well as space, ground, laboratory and optical studies of interplanetary dust, the relationship between this dust and comets, its interactions with plasma, its dynamics and spatial distribution. Particular attention is given to ground-based observations of near ecliptic zodiacal light brightness, the change in near-ecliptic zodiacal light brightness with heliocentric distance, IRAS observations of interplanetary dust emission, and observation of the F-corona radial velocities field between 3 and 7 solar radii. Other topics include orbits of interplanetary dust particles inside 1 AU as observed by Helios, chemical and isotopic compositons of refractory elements in deep sea spherules, optical models of the three dimensional distribution of interplanetary dust, the particle-size-distribution function of cometary dust, laboratory simulation of chemical interactions of accelerated ions with dust and ice grains, and an analysis of IRAS' solar system dust bands. Title: Doppler Shifts Measurements of the Zodiacal Light at the PIC Midi Observatory Authors: Robley, R.; Buecher, A.; Koutchmy, S.; Lamy, Ph. Bibcode: 1985ASSL..119...85R Altcode: 1985IAUCo..85...85R; 1985piid.proc...85R The authors have started a program to observe the spectrum of the zodiacal light in the region of the b absorption lines of Mg I. They use a 1 meter spectrograph with a holographic grating followed by a focal reducer to obtain a 19 Å/mm dispersion over the micro-channel plate camera. Calibrated spectra obtained with an exposure time of 10 minutes systematically show earth atmospheric emission lines attributed to both N I and OH. The temporal variability of these emissions prevents an accurate determination of the line profiles. The authors best processed measurements of Doppler shifts obtained during five nights do not allow to discriminate between circular and hyperbolic orbits of the interplanetary dust. Title: Optical Properties of Rough Grains: a Theoretical Study Authors: Perrin, J. M.; Lamy, P. L. Bibcode: 1985ASSL..119..245P Altcode: 1985IAUCo..85..245P; 1985piid.proc..245P Recent work on the light scattering by large rough particles has led the authors to propose a model based on the high-energy approximation, the laws of geometrical optics and a mathematical description of the properties of the particle roughness. The influence of the various parameters of the model including those characterizing the roughness on the total intensity and the polarization is presented. Title: Some Remarks on the Density of Interplanetary Dust Grains Authors: Lamy, P. L. Bibcode: 1985ASSL..119..137L Altcode: 1985piid.proc..137L; 1985IAUCo..85..137L The relevance of the bulk density as a physical parameter characterizing interplanetary dust grains is discussed. The various measurements which lead to a determination of this parameter are reviewed. The specific case of the collected interplanetary dust grains is considered. Title: A Coronascanner for a Sun Oriented Space Mission Authors: Koutchmy, S.; Lamy, P. L. Bibcode: 1985ASSL..119..141K Altcode: 1985IAUCo..85..141K; 1985piid.proc..141K No abstract at ADS Title: Photographic Observations of the Inner Zodiacal Light Aboard Saliout 7 Authors: Nikolskii, G.; Koutchmy, S.; Lamy, P. L.; Nesmianovich, I. A. Bibcode: 1985ASSL..119....7N Altcode: 1985IAUCo..85....7N; 1985piid.proc....7N Color photographs of the inner zodiacal light were obtained aboard Salyut 7 with Kodak Ekta 400. Absolute calibrations were performed in-flight with attenuated sunlight. The photometric analysis was carried out in three colors and corrections were introduced for the O I emission of the F layers. The brightness of the zodiacal light along the ecliptic is found in good agreement with published data while its color is found slightly redder than the sun. Its out-of-ecliptic variation coincides neither with the fan nor the ellipsoidal model; the photometric axis is found near the projection of the orbital plane of Venus. Title: Astrophysical and geophysical observations with piramig/salyut 7 experiment Authors: Levasseur-Regourd, A. C.; Courtes, G.; Herse, M.; Koutchmy, S.; Lamy, P.; Muliarchik, T. M.; Rocca-Volmerange, B.; Savchenko, S. A.; Secher, B.; Tovmassian, H. M.; Beresovoy, A. N.; Chretien, J. L.; Ivanchenkov, A. S.; Djanibekov, V. A.; Lebedev, V. V.; Popov, L. I.; Savitskaya, S. E.; Serebrov, A. A. Bibcode: 1985AdSpR...5c..27L Altcode: 1985AdSpR...5...27L The facility offered by the Salyut 7 vehicle has allowed teams of scientists of 3 CNRS french laboratories to develop an instrument optimized for several disciplines in astrophysics and geophysics. P.I.R.A.M.I.G. (Photography Infra-Red Atmosphere, Interplanetary Medium, Galaxies) is a wide field (10° and 40°) camera devoted to high sensitivity photographic photometry. The spectral range is limited to the visible and near-infrared (400-850 nm), the main advantage being to observe above the absorving and emitting layers of the atmosphere. Title: Electrostatic Charge of Interplanetary Dust Grains: New Results Authors: Lamy, P. L.; Lefevre, J.; Millet, J.; Lafon, J. P. Bibcode: 1985ASSL..119..335L Altcode: 1985IAUCo..85..335L; 1985piid.proc..335L A continuing program aimed at improving the determination of the charge of interplanetary as well as cosmic grains is presented. Recent data have been combined to generate two high-resolution solar spectra corresponding to the maximum and minimum of activity. The energy distribution of photoelectrons emitted by quartz grains under solar irradiation is calculated using the new laboratory measurements of Quemerais et al. (1986). Finally, the method of Lafon, Millet and Lamy (1981) is used to find the electrostatic potential of these grains. Title: A spectral photopolarimeter for Giotto: Halley optical probe experiment Authors: Levasseur-Regourd, A. C.; Bertaux, J. L.; Dumont, R.; Festou, M. C.; Giese, R. H.; Giovane, G.; Weinberg, J. L.; Lamy, P.; Llebaria, A. Bibcode: 1984AdSpR...4i.287L Altcode: 1984AdSpR...4..287L The Halley Optical Probe Experiment (HOPE) is designed to provide in situ photopolarimetric data on both the dust cloud and the gaseous atmosphere in Halley's coma. The optical probe concept is presented here, together with a description of the instrumentation and with the possibilities for cross-checks between HOPE results and those of other space and ground-based experiments. Title: The Betelgeuse shell : CCD/Fabry-Perot surface brightness photometry at K I lambda 7699A and mass loss. Authors: Mauron, N.; Fort, B.; Querci, F.; Dreux, M.; Fauconnier, T.; Lamy, P. Bibcode: 1984A&A...130..341M Altcode: Surface brightness photometric measurements of the Betelgeuse circumstellar shell at K I 7699 A were observed with a Fabry-Perot etalon and a CCD camera. Emission strength decreased as r exp -3.5 + or - 0.8, where r is the distance from the star. Also noted was that the emission strength, related to the mass-loss rate, and the slope of the decreasing intensity, related to the K I ionization and the density distribution, did not agree with values obtained by Honeycutt et al. (1980), but did concur with the model of Jura by Morris (1981). A mass-loss rate of 4 x 10 to the -6th solar mass/year was presented and the carbon scarcity in the shell was decreased to a factor of six. A slight departure from symmetry was found and tentatively attributed to photospheric brightness asymmetry. Title: Optical properties of cometary grains: a new model. Authors: Lamy, P. L.; Perrin, J. M. Bibcode: 1983UppOR..25...49L Altcode: No abstract at ADS Title: Nature, origin and evolution of interplanetary dust grains. Authors: Lamy, P. L. Bibcode: 1983HiA.....6..427L Altcode: The survey is based for the most part on studies carried out in recent years at the Laboratoire d'Astronomie Spatiale, in Marseille (France). The topics covered are the size distribution and physical properties of interplanetary dust grains, collisions among interplanetary dust grains, the implications for zodiacal light, and mass flux at 1 AU. A summary is given of the work presented by Le Sergeant d'Hendecourt and Lamy (1980). In discussing collisions among interplanetary dust grains, it is noted that certain investigators (Zook and Berg, 1975; Dohnanyi, 1976) have proposed that the population '2' of small, essentially submicronic grains could be the fragments of collisions between large grains ejected by radiation pressure, thereby creating an outflow of what are called 'beta-meteoroids' as detected by Pioneer 8 and 9. In another study by Le Sergeant d'Hendecourt and Lamy (1981), this mechanism was examined, and it was concluded that the calculated flux of fragments could not match by far the observed flux of submicronic grains. Title: Optical properties of rough cometary grains Authors: Lamy, Ph. L.; Perrin, J. M. Bibcode: 1983acm..proc..273L Altcode: The authors use their new model of light scattering by large rough particles to investigate the optical properties of cometary grains. The efficiency factor for extinction increases rapidly with increasing roughness while that for absorption remains fairly constant and while the ratio of radiation pressure to gravity decreases. Title: Widefield Ultraviolet Observations of Comet Halley with the FAUST SPACELAB-1 Instrument Authors: Bowyer, S.; Courtes, G.; Kimble, R.; Deharveng, J. M.; Malina, R. F.; Lamy, P. Bibcode: 1983rrsb.conf..207B Altcode: No abstract at ADS Title: Large-scale Photographic Observations, Photometry, Colorimetry and Polarimetry of Cometary Tails Authors: Lamy, P. L.; Koutchmy, S. Bibcode: 1982ncgb.conf..243L Altcode: 1982gbhc.work..243L The use of large-scale photographic observations to characterize the dust tails of comets is discussed, with emphasis on plans being developed for observing Halley's Comet in 1986. The techniques used to investigate the geometric structure of the dust tail and its evolution (including detached structures, bursts, striae, and large-scale extensions), the integrated magnitude from blue to far IR, and color and polarization parameters are reviewed and illustrated with data and images from recent studies of other comets. The requirements for a network of identical cameras for Halley observations are examined: minimum 30-deg field of view, spectral coverage and filter separation, polarizers, calibration, color emulsions, and data-reduction schemes. Many of the problems inherent in ground observations programs could be avoided by using a space instrument such as the very-wide-field camera flown on the first Spacelab mission; this device is briefly described. Title: Wide field ultraviolet observations of Comet Halley with the FAUST Spacelab I instrument Authors: Bowyer, S.; Kimble, R.; Malina, R. F.; Lamy, P.; Courtes, G.; Deharveng, J. M. Bibcode: 1982AdSpR...2l.207B Altcode: 1982AdSpR...2..207B The wide field (7.5°), arc minute imaging, and spectroscopic capabilities of the Far Ultraviolet FAUST telescope which will be flown on Spacelab I can provide valuable information on Comet Halley. The use of the FAUST instrument in obtaining images of the hydrogen coma at 1216 Å, and in obtaining objective grating spectroscopy from 1300-3300 Å of the comet and tail, are described. The FAUST images would provide large field of view data that are required for model calculations of gas production rates and the determination of scale lengths and lifetimes of ion species. Title: A coronographic mode for large telescopes. Authors: Courtes, G.; Lamy, P.; Mauron, N.; Saisse, M. Bibcode: 1982ASSL...92...73C Altcode: 1982IAUCo..67...73C; 1982ialo.coll...73C Lyot's coronographic technique of stray-light reduction has been applied to the Faint Object Camera of the Space Telescope. In addition, the application of the coronographic mode to the design of the Mount Chiran 1-m and ESO 3.6-m Ritchey-Chretien telescopes has given new levels of performance in the detection of faint features in stellar and planetary observations. As an example, observations of a new satellite of Saturn, 1980 S10 (Dione B), are examined. Title: An Opportunity for the Observations of Comets with Widefield Cameras Aboard the Salyut Space Station Authors: Lamy, P. L.; Koutchmy, S. Bibcode: 1981motc.conf..190L Altcode: No abstract at ADS Title: Collisional processes among interplanetary dust grains: An unlikely origin for the β meteoroids Authors: Le Sergeant Dhendecourt, L. B.; Lamy, P. L. Bibcode: 1981Icar...47..270L Altcode: The question of the collisional production of the β meteoroids is reexamined incorporating recent experimental results (A. Fugiwara, G. Kamimoto, A. Tsukamoto, 1977, Icarus31, 277-288). The collisional model yields a flux of fragments supported by the conservation of mass flux which does not account by far for the observed flux of submicron grains. Particles larger than about 100 μm will be destroyed by collisions inside 1 AU, well before they can get near the Sun. The existence of two independent populations of interplanetary dust grains as proposed by L. B. Le Sergeant and Ph. L. Lamy (1978, Nature266, 822-824; 1980, Icarus43, 350-372) appears reinforced. It is proposed that the bulk of submicron grains does not necessarily travel in hyperbolic orbits and that β meteoroids may be a phenomenon—possibly transitory—of limited importance. Title: Observations of Saturn's outer ring and new satellites during the 1980 edge-on presentation Authors: Lamy, P. L.; Mauron, N. Bibcode: 1981Icar...46..181L Altcode: Observations of Saturn's satellites and external rings during the 1980 edge-on presentation were obtained with a focal coronograph. A faint satellite traveling in the orbit of Dione and leading it by 72° has been detected, together with the two inner satellites already suspected (cf. J. W. Fountain and S. M. Larson, 1978,Icarus36, 92-106). The external ring has been observed on both east and west sides; it may extend up to ⋍8.3 Saturn radii, and appears structured. Title: Infrared Imaging and Speckle Observations with a TV Camera Authors: Lamy, P.; Koutchmy, S. Bibcode: 1981Msngr..23....5L Altcode: The lack of suitable two-dimensional detectors has been a major problem for infrared imaging in astronomy, and most results so far have been obtained by scanning the object with a single detector (e. g., Terrile and Westphal,lcarus, 30, 730, 1977). The relative merit of both techniques was thoroughly investigated by Hall (Applied Optics, 10, 838, 1971) who concluded that, below about 2.5 ~lm, camera tubes should be preferred to scanners. Besides, sufficiently long times required by the scanning technique are not always available for some astronomical applications. These considerations led us to acquire a standard television camera equipped with an infrared vidicon tube N156 manufactured by Hamamatsu Co. (Japan). Title: Satellites of Saturn. Authors: Lamy, P. Bibcode: 1981IAUC.3572....2L Altcode: No abstract at ADS Title: Satellites of Saturn Authors: Lamy, P. Bibcode: 1981IAUC.3574....2L Altcode: P. Lamy, Laboratoire d'Astronomie Spatiale, Marseilles, telexes that further examination of plates taken at the Haute Provence Observatory (cf. IAUC 3463, 3491) reveals a new satellite, 1980 S 29, of mag ~ 14.5 to 15. On 1980 Mar. 16.126 UT, 1980 S 29 was located 19".75 east of Saturn. It may correspond to one or more of 1980 S 7, 1980 S 20, 1980 S 23, 1980 S 26 or 1980 S 27. In addition, 1980 S 3 was measured at a position 22".7 west of Saturn on Mar. 16.9156. Title: Comets. Authors: Festou, M. C.; Lamy, P. Bibcode: 1981Rech...12...46F Altcode: No abstract at ADS Title: The Halley Optical Probe Experiment Authors: Levasseur-Regourd, A. C.; Weinberg, J. L.; Giovane, F.; Schuerman, D. W.; Lamy, P.; Festou, M.; Bertaux, J. L.; Dumont, R.; Llebaria, A.; Giese, R. H. Bibcode: 1981giot.proc..121L Altcode: No abstract at ADS Title: On the electrostatic potential of interplanetary grains - Influence of the thermionic effect Authors: Millet, J.; Lafon, J. P. L.; Lamy, P. L. Bibcode: 1980A&A....92....6M Altcode: The general theory of the floating potential of a cosmic grain (Lafon et al. 1980) was used to investigate the importance of the thermionic emission for interplanetary iron and carbon grains in the vicinity of the sun. This emission prevents the potential of carbon grains from becoming strongly negative and allows small grains to exist in regions where they would otherwise be destroyed. Title: On the size distribution and physical properties of interplanetary dust grains Authors: Le Sergeant D'Hendecourt, L. B.; Lamy, Ph. L. Bibcode: 1980Icar...43..350L Altcode: This paper synthesizes information on the size distribution and physical properties of interplanetary dust grains obtained from analyses of lunar microcraters performed until 1979. The different aspects of these analyses (counting methods, simulation, calibrations) are summarized and a large amount of data is collected and discussed in order to clarify past contradictions. The number of small microcraters ( Dc < 5 μm) is found to be higher than previously derived and the ratio P/ Dc (depth to crater diameter) to depend upon their sizes. All results converge to a two-component dust population: Population 1 consists principally of large grains ( d > 2 μm) with density typical of silicates while Population 2 consists of small grains ( d < 2 μm) with higher density typical of iron, with a minor component of silicates. The conclusion appears to be further supported by spatial measurements and collection experiments. Fluffy grains of very low density (0.3 g/cm 3) are probably not present to a large extent. Title: Satellites of Saturn Authors: Lamy, P.; Mauron, N. Bibcode: 1980IAUC.3491....3L Altcode: P. Lamy and N. Mauron, Laboratoire d'Astronomie Spatiale, Marseilles, send the following precise measurements of 1980 S 10 (cf. IAUC 3463) with respect to the center and equatorial plane of Saturn: Mar. 15.9528 UT, +57".24 (east), -0".55 (south); 15.9851, +58".93, -0".38; 16.0236, +60".40, -0".37; 16.0892, +61".45, -0".57; 16.126, +61".65, -0".67. They also provide the measurements: 1966 S 2, Mar. 15.9851, 22".45 west; 1980 S 3, Mar. 16.126, 19".75 east. They add that orbital analysis shows that 1980 S 10 (= 1980 S 6: cf. IAUC 3483) leads Saturn IV (Dione) by 72o.0. 1980 S 13 could not be found on plates taken on Mar. 15.9528 and 16.962 on the assumption that it trails Saturn IV by 57o and was brighter than magnitude 18. Title: The New Satellite Dione B and Outer Ring of Saturn. Authors: Lamy, P. L.; Mauron, N. Bibcode: 1980BAAS...12R.728L Altcode: No abstract at ADS Title: Satellites of Saturn Authors: Lecacheux, J.; Laques, P.; Wierick, G.; Lelievre, G.; Smith, B. A.; Blume, W. H.; Lamy, P.; Mauron, N. Bibcode: 1980IAUC.3483....1L Altcode: J. Lecacheux, Observatoire de Meudon, reports the following analyses and further electronographic observations by P. Laques at Pic du Midi and by G. Wierick and G. Lelievre at Haute Provence of separations of satellites (+ = east, - = west) from Saturn's center: 1966 S 2 = 1980 S 1 = 1980 S 2: Mar. 1.0488 UT, +22".16; 17.031, +21".83. Revised elements from the data on IAUC 3470-3474: greatest eastern elongation = 1980 Mar. 18.317 UT + light time + 0.0019 (U - 45o.6) + 0.69465 E. The identities with 1979 S 7 and 1979 S 1 are invalid, the orbital longitude of 1966 S 2 at the time of the closest approach of Pioneer 11 having been L = 121o +/- 3o. [Editorial Note. It now seems probable that the correct definition of 1966 S 2 is orbit 16 in the paper by Aksnes and Franklin (1978, Icarus 36, 107); see also Fountain and Larson (1978, ibid. 36, 92). The designation 1966 S 1 refers to an orbit with period 0.75 day, and no object with this period is now believed to exist.] 1980 S 3 = 1980 S 4 = 1980 S 5 = 1980 S 8 (observation on IAUC 3463 only) = 1980 S 11 = 1980 S 15 = 1980 S 16 = 1980 S 17 = 1980 S 19: Mar. 17.009 UT, -21".6; 18.040, +22".3. Elements (fitting the indicated observations with a standard deviation of 0".5): greatest eastern elongation = 1980 Mar. 18.645 UT + light time + 0.0019 (U - 45o.6) + 0.6939 E. Other published observations (i.e., 1979 S 7, 1980 S 7, 1980 S 9, 1980 S 18, 1980 S 20, 1980 S 21 and the IAUC 3466 observation attributed to 1980 S 8 [here redesignated 1980 S 23: Ed.] do not fit any single circular solution. [Editorial Note. The suggestion that there exists a second satellite essentialy in the orbit of 1966 S 2 and about 180o from it was privately made to the Central Bureau by B. A. Smith, University of Arizona, early in March. It is quite possible that 1980 S 3 = 1979 S 1, for which W. H. Blume has given the time of greatest western elongation (at Saturn) as 1979 Aug. 31.997 +/- 0.004 UT. 1979 S 2 and 1979 S 4 can together presumably be related to 1966 S 2 and 1980 S 3.] 1980 S 6 = 1980 S 10 = 1980 S 12 = 1980 S 14: Mar. 1.030 UT, +62".4; 1.049, +62".2; 1.099, +61".4; 1.131, +59".9 (refinement to IAUC 3457). [Editorial Note. The suggestion that 1980 S 6 = 1980 S 10 with period 2.75 days was included with the information provided by P. Lamy and N. Mauron for publication on IAUC 3463. Both Smith and Lecacheux have suggested that 1980 S 6 is associated with the triangular libration point leading Saturn IV (Dione). It is possible that 1980 S 13 is associated with the corresponding trailing point.] Title: Satellites of Saturn Authors: Harris, A. W.; Gibson, J.; Lecacheux, J.; Fort, B.; Fauconnier, T.; Dreux, M.; Vapillon, L.; Laques, P.; Auge, A.; Despiau, R.; Lamy, P.; Mauron, N. Bibcode: 1980IAUC.3463....1H Altcode: A. W. Harris, Jet Propulsion Laboratory, reports that observations by J. Gibson and himself with the 2.5-m reflector at Mount Wilson Observatory suggest that the satellite 1966 S 2 attained its greatest elongations from Saturn around the following times: Mar. 13.16 UT (west), 13.51 (east), 14.54 (west), 15.2 (west) and 17.32 (west). Several other condensations, some of them obviously transient ring knots, were also noted. Three of them, each ~ 1 mag fainter than 1966 S 2, were somewhat more persistent and showed motion suggesting that they might be satellites. The designations, inferred times of greatest elongations and separations of these objects from Saturn were: 1980 S 7, Mar. 13.29, 23" east; 1980 S 8, Mar. 15.19, 24" east; 1980 S 9, Mar. 15.27, 25" west (clear of rings). J. Lecacheux, B. Fort, T. Fauconnier, M. Dreux and L. Vapillon, Meudon Observatory; and P. Laques, A. Auge and R. Despiau, Pic du Midi Observatory, communicate the following separations (uncertainty +/- 0".2) of 1966 S 2 east (+) or west (-) of Saturn's center: Feb. 29.022 UT, -20".09; Mar. 1.0571, +21".76; 1.0575, +21".43; 1.0634, +20".78; 16.9439, +22"; 17.9661, -22".20; 18.0401, -24".64; 18.0443, -23".90; 18.0494, -23".33; 18.1052, -17".74; 18.1065, -17".57. The observations were made using a Lallemand electronographic camera and a CCD camera on the 1.05-m Pic du Midi reflector. The best exposure (Mar. 18.0401) shows the starlike object very clearly detached from the A ring, brighter than Saturn VII (Hyperion) but fainter than Saturn I (Mimas); the inferred time of greatest western elongation is Mar. 18.017 UT. The following ephemeris has been deduced from these observations and those by Pascu and by Smith et al. on IAUC 3454, 3456 and 3457: greatest eastern elongation = 1980 Mar. 18.316 UT + light time + 0.0019 (U - 45o.6) + 0.69468 E. [Editorial Note. This formula is also in good agreement with the above observations by Harris and Gibson. On the other hand, it indicates a greatest eastern elongation on 1979 Dec. 9.3 UT, rather than Dec. 9.5 UT; cf. the observation by Mulholland on IAUC 3430.] P. Lamy and N. Mauron, Laboratoire d'Astronomie Spatiale, Marseilles, report that observations with the Chiran 1-m telescope at the Haute Provence Observatory showed 1966 S 2 to be 24" west of Saturn's center on Mar. 15.983 UT. A faint nebulosity (mag ~ 16), possibly another satellite, was detected on several plates; this object, designated 1980 S 10, attained a maximum elongation of 61".4 west of Saturn's center on Mar. 16.024 UT (cf. 1980 S 6, IAUC 3457). Title: Collisions among Interplanetary Dust Grains Authors: Le Sergeant, L. B.; Lamy, P. L. Bibcode: 1980IAUS...90..289L Altcode: No abstract at ADS Title: Two-Dimensional Photographic Photometry of the Zodiacal Light from Spatial Observations Authors: Lamy, P. L.; Llebaria, A.; Koutchmy, S. Bibcode: 1980IAUS...90...37L Altcode: No abstract at ADS Title: The electrostatic potential of interplanetary grains Authors: Lafon, J. P. J.; Lamy, P. L.; Millet, J. M. Bibcode: 1980IAUS...90..303L Altcode: The plasma sheath and its bulk velocity are included as parameters for calculating the electrostatic potential of cosmic grains. The most important effects determining the charge of the grain to be considered in calculations are photoelectric emission and sticking of solar wind electrons and ions, except at small heliocentric distances. The results use parameters for two representative components of the solar wind and include the influence of bulk velocity which is important through the positive ions. The role of the solar wind appears clearly in the effect of its bulk velocity on the potential. The electrostatic potential is shown to increase slightly with increasing heliocentric distance and levels off at 1 AU, although thermionic emission will come into play and increase the potential. Title: Zodiacal light models with a bimodal population Authors: Lamy, P. L.; Perrin, J. M. Bibcode: 1980IAUS...90...75L Altcode: The compatibility of the observed properties of interplanetary dust grains in zodiacal light with a model made of two populations is investigated. Population 1 consists principally of large grains (with radius s greater than 2 microns) of density typical of silicates or chondritic materials in nearly circular orbit while Population 2 consists of small grains (s less than 2 microns) with typically metallic densities (abt 8 g/cu cm) in hyperbolic orbits. The spatial densities and volume scattering functions (VSF) of the two populations are deduced from the observed brightness of the zodiacal light. Though no clear-cut conclusions are reached, some general trends are detected: (1) the VSF of the zodiacal light is entirely compatible with the spatial density of grains obtained from lunar and space measurements. (2) Under all circumstances, the contribution of Population 2 appears to be non-negligible. (3) A minimum albedo of 0.5 (probably unrealistic) is required in order to explain the observed VSF with Population 1 alone on the basis of the model of Fresnel reflection plus an isotropic term. Title: 2-D observations of IR-stellar speckles. Authors: Lamy, P.; Koutchmy, S. Bibcode: 1979JOpt...10..331L Altcode: 1979JOp....10..331L The first observations of speckle images of Alpha Orionis as obtained at the Cassegrain focus of the 193-cm Telescope of the Haute Provence Observatory using an IR-TV camera are discussed. The specific nature of the 2-micron images is outlined. Title: Radiation forces on small particles in the solar system Authors: Burns, J. A.; Lamy, P. L.; Soter, S. Bibcode: 1979Icar...40....1B Altcode: We present a new and more accurate expression for the radiation pressure and Poynting-Robertson drag forces; it is more complete than previous ones, which considered only perfectly absorbing particles or artificial scattering laws. Using a simple heuristic derivation, the equation of motion for a particle of mass m and geometrical cross section A, moving with velocity v through a radiation field of energy flux density S, is found to be (to terms of order v/c) m v˙ = ( SA/c)Q pr[(1 - ṙ/c) Ŝ - v/c] , where Ŝ is a unit vector in the direction of the incident radiation, ṙ is the particle's radial velocity, and c is the speed of light; the radiation pressure efficiency factor Qpr ≡ Qabs + Qsca(1 - <cos α>), where Qabs and Qsca are the efficiency factors for absorption and scattering, and <cos α> accounts for the asymmetry of the scattered radiation. This result is confirmed by a new formal derivation applying special relativistic transformations for the incoming and outgoing energy and momentum as seen in the particle and solar frames of reference. Qpr is evaluated from Mie theory for small spherical particles with measured optical properties, irradiated by the actual solar spectrum. Of the eight materials studied, only for iron, magnetite , and graphite grains does the radiation pressure force exceed gravity and then just for sizes around 0.1 μm; very small particles are not easily blown out of the solar system nor are they rapidly dragged into the Sun by the Poynting-Robertson effect. The solar wind counterpart of the Poynting-Robertson drag may be effective, however, for these particles. The orbital consequences of these radiation forces-including ejection from the solar system by relatively small radiation pressures-and of the Poynting-Robertson drag are considered both for heliocentric and planetocentric orbiting particles. We discuss the coupling between the dynamics of particles and their sizes (which diminish due to sputtering and sublimation). A qualitative derivation is given for the differential Doppler effect, which occurs because the light received by an orbiting particle is slightly red-shifted by the solar rotation velocity when coming from the eastern hemisphere of the Sun but blue-shifted when from the western hemisphere; the ratio of this force to the Poynting-Robertson force is ( R ⊙/r) 2[( w ⊙/n) - 1] , where R⊙ and w⊙ are the solar radius and spin rate, and n is the particle's mean motion. The Yarkovsky effect, caused by the asymmetry in the reradiated thermal emission of a rotating body, is also developed relying on new physical arguments. Throughout the paper, representative calculations use the physical and orbital properties of interplanetary dust, as known from various recent measurements. Title: Astronomical applications of infrared television imaging. Authors: Lamy, P. L.; Nguyen-Trong, T.; Adjabschirzadeh, A.; Koutchmy, S. Bibcode: 1979A&A....77..257L Altcode: Infrared imaging between 1 and 2.4 microns was realized with a television camera operated at the conventional video rate. A M2 star of visual magnitude 5.6 was detected at 1.2 and 1.6 microns. Alpha Ori was further observed at 2 microns and the corresponding smearing function was found to improve with increasing wavelength. The image structure (speckle) of Alpha Ori was visualized in the infrared and is briefly characterized as compared to the visible. Solar observations at 1.6 microns included direct imagery of sunspots and simultaneous spectrography of the photosphere and sunspot umbra. The Zeeman splitting of the 1.5648 microns Fe I line was observed and measurements are shown to be possible on processed CRT pictures. Title: Comet West 1975n. I. Observations near and after perihelion passage. Authors: Koutchmy, S.; Coupiac, P.; Elmore, D.; Lamy, P.; Sevre, F. Bibcode: 1979A&A....72...45K Altcode: Photographic observations of Comet West 1975n from a high altitude site are reported. A small value of the absolute magnitude of the Comet 1.5 d after perihelion passage is deduced. Morphological characteristics of the strongly structured dust tail are obtained, using a statistical analysis based on the optical data processing of a transparency. The deduced two-dimensional power spectrum is considered. The temporal behavior of the main features of the tail is discussed using several selected pictures. Title: Comet West 1975n part II: study of the striated tail. Authors: Lamy, P. L.; Koutchmy, S. Bibcode: 1979A&A....72...50L Altcode: The dynamical evolution of the striae in the tails of comet West 1975n is investigated. A synchrone-syndyne analysis of the overall tail structure is attempted, but it is found that the classical synchrone-syndyne description does not apply to the dynamical evolution of the striae. A subsequent examination of the main properties of the stria structure strongly suggests that all striae within a given tail appear to originate from a synchronic edge. A scenario for the formation of striae is proposed, according to which the bulk of the dust constituting a tail is released at or around perihelion and subsequently swept out under the influence of some unknown interaction that organizes the dust into narrow streaks, or striae. It is concluded that the unknown interaction involves the solar wind and a convected magnetic field. Title: Cometary Dust - Importance of Large-Scale and In-Situ Observations Authors: Lamy, P. L. Bibcode: 1979comi.work..131L Altcode: No abstract at ADS Title: Interplanetary dust: are there two independent populations? Authors: Le Sergeant, L. B.; Lamy, P. L. Bibcode: 1978Natur.276..800L Altcode: A RE-EXAMINATION of the information on the size distribution and physical properties of interplanetary dust grains as inferred from space measurements, particularly lunar microcraters, leads to the novel interpretation outlined here in terms of two independent populations. This hypothesis still suffers from uncertainties in existing data but should stimulate new experimental and theoretical work. Title: Photon Counting and Analog Television Systems with Digital Real Time Image Processing and Display Authors: Cenalmor, V.; Lamy, Ph. L.; Perrin, J. M.; Nguyen-Trong, T. Bibcode: 1978A&A....69..411C Altcode: Summary. For a photon counting television system (PCTS) and an analog television system (ATS), we developed a common acquisition, real-time processing and visualisation unit which is basically composed of a random access memory of 64 kilowords of 16 bits, a microprocessor, a television color display and a floppy disk recorder. Image processing is performed either by the microprocessor or by a minicomputer connected to the system. Preliminary results obtained at the telescope are reported. Key words: television photon counting image processing Title: Photometrical analysis of the June 30, 1973 solar corona. Authors: Koutchmy, S.; Stellmacher, G.; Koutchmy, O.; Dzubenko, N. I.; Ivanchuk, V. I.; Popov, O. S.; Rubo, G. A.; Vsekhsviatskii, S. K.; Lamy, P. Bibcode: 1978A&A....69...35K Altcode: In order to deduce reliable values of the K and F coronal, a method of photographic photometry has been applied to study compensated high-resolution pictures obtained during the June 30, 1973, solar total eclipse, including a color one. The correctly exposed images of calibration stars are used to obtain intensities in units of the mean brightness of the sun. An account is made, in both the blue and the red spectral ranges, for the sky background as well as for the coronal aureola effects. The N-polar and E-equatorial regions are shown to be relatively homogeneous; their intensities are especially studied in the radial direction and compared with published values of the K and F coronae. No flattening and no color effect are found in the inner part (distance less than 2.5 solar radii) of the F corona. Title: Propagating inhomogeneities in the dust tail of comet West 1975 Authors: Koutchmy, S.; Lamy, P. Bibcode: 1978Natur.273..522K Altcode: COMET West has displayed some remarkable properties. Sekanina1 has studied the multiple splitting of its nucleus and also discussed the strange structure of its dust tail. This tail is characterised by a system of bright bands which do not correspond to the true synchronous band2 and which are shown by very few comets. We call these striae (striated tail) and to study them we have examined numerous original and duplicate pictures, and selected four observations (Table 1) which reveal that the morphology was relatively well conserved during the evolution of the dust tail over a period of more than 4 days. We have identified three striae (Fig. 1) which seem to propagate in space while retaining their basic form. This phenomenon is not unusual in plasmas, such as gas tails of comets3 or streamers in the solar K-corona4,5. However, this is apparently the first time that it has been observed in dust `clouds'. These striae, which we describe here, are made of dust grains which can be readily demonstrated by the wide-field colour photographs made by comet observers: the gas tail (type I) appears distinctly blue because of CN emission and is directly in the anti-solar direction as well as being well separated from the large dust tail (type II) which has a neutral colour. Title: Optical properties of silicates in the far ultraviolet Authors: Lamy, P. L. Bibcode: 1978Icar...34...68L Altcode: Near-normal incidence reflectance measurements in the interval 1026-1640 Å were performed on four silicates already studied in the visible and infrared by Pollack et al. (1973). We use a Kramers-Kronig analysis of these data to calculate the complex index of refraction m = n - ik. New transmission measurements improve the determination of k in the interval 2500-4500 Å, except for andesite, which is more opaque than found by Pollack et al. Title: Workshop on cometary missions. ESOC Darmstadt, 17 - 19 April 1978. Chairmen's summaries and extended abstracts of invited contributions. Authors: Arpigny, C.; Bertaux, J. L.; Bodechtel, J.; Dalmann, B. -K.; Fechtig, H.; Festou, M.; Giese, R. H.; Grün, E.; Haser, L.; Hughes, D. W.; Ip, W. -H.; Jockers, K.; Keller, H. U.; Keppler, E.; Kissel, J.; Koutchmy, S.; Krankowsky, D.; Lämmerzahl, P.; Lamy, P. L.; Levasseur-Regourd, A. -C.; Lukoshhus, D.; Malaise, D.; Mariani, F.; Michel, K. W.; Neukum, G.; Orfei, R.; Rosenbauer, H.; Röser, S.; Schlude, F.; Schmidt, H. U.; Schubart, J.; Schwehm, G. H.; Sieber, A.; Wänke, H.; Wallis, M. K.; Zerull, R. H. Bibcode: 1978wocm.book.....A Altcode: No abstract at ADS Title: Radiation pressure and Poynting-Robertson drag for small spherical particles. Authors: Soter, S.; Burns, J. A.; Lamy, P. L. Bibcode: 1977cami.coll..121S Altcode: 1977IAUCo..39..121S Robertson's expression for the velocity-dependent effect of solar radiation on the motion of small particles is difficult because of its dependence on relativistic considerations, and it is also deficient in that it assumes perfectly absorbing particles. The present paper gives a heuristic derivation of the Poynting-Robertson effect. Robertson's expression for perfectly absorbing particles is obtained but on a much simpler physical basis, and an expression is also obtained for a particle that in general scatters, transmits, and absorbs light. Some numerical results on the solar radiation forces felt by small particles of cosmochemically important compositions are given. Title: Traitement des Images TÉLÉVISION - Application à une CAMéRA Infra Rouge Authors: Lamy, P. L.; Nguyen-Trong, T.; Perrin, J. M. Bibcode: 1977aaid.coll...17L Altcode: 1977IAUCo..40...17L No abstract at ADS Title: A Corrected Derivation of the Poynting-Robertson Effect Authors: Burns, J. A.; Soter, S.; Lamy, P. L. Bibcode: 1976BAAS....8..434B Altcode: No abstract at ADS Title: The Poynting-Robertson effect for small spherical particles. Authors: Burns, J. A.; Soter, S.; Lamy, P. L. Bibcode: 1976BAAS....8..471B Altcode: No abstract at ADS Title: Study of the Anti-Tail of Comet Kohoutek from an Observation on 17 January 1974 Authors: Lamy, Ph. L.; Koutchmy, S. Bibcode: 1976LNP....48..343L Altcode: 1976IAUCo..31..343L As part of our program of observation of Comet Kohoutek at Pic-du-Midi observatory, we obtained, on January 17.8 UT, 1974 a photograph in polarized light showing dramatically the (dust) antitail extending for almost 1° from the Comet's head (reported in Sky and Telescope, June 1974); indeed the comet is visible in polarized light further away than in total light as noticed by Weinberg and Beeson (IAU Colloquium No. 25, 1974) for Comet Ikeya-Seki. A photometric and polarimetric study was performed (Bücher, A., Robley, R., and Koutchmy, S., 1975, Astron. Astrophys. 39, 289) showing that the anti-tail is strongly polarized (up to 50 %). These large degrees of polarization are of the same order of magnitude as those reported for the tail of Comet Ikeya-Seki by Matjagin Sabitov and Kharitonov (1967, Astron. Zh. 44, 1075) and by Weinberg and Beeson (op. cit.). As discussed by these latter authors, particle alignment is precluded as a significant contributor to polarization in the tail of comets. Polarization by large spheres as obtained from the Fresnel reflection coefficients applies only in the case of perfect surface, a circumstance very unlikely in interplanetary space; the scattering is in fact controlled by the surface microstructures (Van de Hulst, private communication). Therefore we hypothesized that submicronic grains should play an important role in the anti-tail. The classical method of Finson and Probstein (1968, Astrophys. J. 154, 327, 353) was used to draw the sky plane view of the syndynes for the day of observation. Since the ratio β of the radiation pressure force to the gravitational attraction is proportional to the third power of the grains' radius s for ≲z 0.1 μ, submicronic grains with typical radii of 0.02 μ may indeed be present in the anti-tail and provide a straight-forward explanation of the observed polarization. This size is of the same order of magnitude as that inferred for interstellar grains which may well be embedded in the comet's nucleus as well as meteorites for which there exists good evidence. Our conclusion does not rule out the presence of millimeter-size grains as proposed by Sekanina and Gary and O'Dell in their preliminary investigations (1974, Icarus 23, 502, 519) which did not take into account the polarimetric result; such grains may well coexist with the submicronic ones. Finally, the line of maximum intensity is close to a synchrone corresponding to a time of emission 100 days before perihelion passage. This supports the synchronic formation of anomalous tails and possibly of tails as proposed by Vsekhsvyatsky (1932, Astron. Zh. 9, 166). Title: Temperature Distribution and Lifetime of Interplanetary Ice Grains Authors: Lamy, P.; Jousselme, M. F. Bibcode: 1976LNP....48..443L Altcode: 1976IAUCo..31..443L An improved solution for the temperature distribution of interplanetary ice grains is presented using the refractive index measured at 100 K. The efficiency factors for absorption are obtained from Mie theory, and the calculation is carried out for micron- and submicron-size grains at 50, 100 and 150 K. Corresponding lifetimes are given. Title: Orbital Evolution of Circum-Solar Dust Grains Authors: Lamy, P. Bibcode: 1976LNP....48..437L Altcode: 1976IAUCo..31..437L The orbital evolution of circumsolar dust grains is obtained by numerical integration of the equations of motion which includes the grains' interactions with the solar radiation field and the solar wind. A previous solution is improved by avoiding a classical approximation for the Poynting-Robertson term, leading to an important revision of the orbital behavior. Results are presented for obsidian grains whose inward spiraling is stopped by the effect of sublimation. Title: Study of the Inner Satellites of Saturn by Photographic Photometry Authors: Koutchmy, S.; Lamy, P. L. Bibcode: 1975Icar...25..459K Altcode: Good photographs of Saturn and its five inner satellites were obtained on January 2, 1974 with the 105 cm telescope at Pic du Midi Observatory with exposure times of 45 sec. The spread function is constant over the field, and isotropic. The true photometric profiles of the satellites are obtained after deriving a model for the stray light coming from the rings. The magnitudes, computed by integration, are in good agreement with published values except for Mimas, which is nearly one magnitude fainter then previously believed. Title: On the dynamics of interplanetary dust grains Authors: Lamy, Philippe Louis Bibcode: 1975PhDT.......173L Altcode: No abstract at ADS Title: On the Dynamics of Interplanetary Dust Grains. Authors: Lamy, P. L. Bibcode: 1975PhDT.........6L Altcode: The interaction of spherical grains of various materials whose radii lie in the micronic and submicronic range with the interplanetary medium is solved. This includes: (1) interaction with the solar radiation field which is solved using Mie scattering theory and taking into account the precise dependence of optical properties upon wavelength; (2) interaction with solar wind considering corpuscular tangential drag; and (3) interaction with the interplanetary magnetic field in terms of a diffusion or random walk through a series of electromagnetic scatterings. Numerical results for these interactions span in the entire solar system with elliptical orbits of grains of various materials and sizes and provide a clear global picture of dust grain interactions that includes grain dynamic considerations. Title: Interaction of interplanetary dust grains with the solar radiation field. Authors: Lamy, P. L. Bibcode: 1974A&A....35..197L Altcode: The interaction of interplanetary dust grains with the solar radiation field is investigated for micronic and submicronic spheres of quartz, obsidian, andesite, ice, and iron. The dependence of the complex indices of refraction on wavelength was taken into account using Mie theory to obtain the efficiency factors for absorption and radiation pressure. The temperature distributions differ markedly from past results, and show that silicate grains can come very close to the sun, thus justifying the existence of a dusty component of the solar corona up to approximately 2 solar radii. Improved vapor pressure formulas yield increased lifetimes for interplanetary grains. It is shown that the onset of rapid destruction by sublimation is extremely sudden and has a well-defined location which depends upon the absorption character of the grains' material. The radiation pressure force never exceeds the gravitational force for silicates and ice. Title: The Dynamics of Circum-solar Dust Grains Authors: Lamy, Ph. L. Bibcode: 1974A&A....33..191L Altcode: Summary. The inward spiraling of interplanetary dust grains under the Poynting-Robertson and corpuscular pressure drags is shown to be either counterbalanced or reduced by the effect of the net increase of the radiation pressure force caused by the decrease of the grains' radii when sublimating. Precise trajectories, obtained for the first time, show that silicate grains remain in the vicinity of the Sun where they describe an impressive number of orbits. Dynamical dust4ree zones are clearly established and the location of regions of probable concentration are predicted; infrared emission spectra show remarkable features which can serve as signatures for the nature of the dust. It is also concluded that grains whose radii are less than about 0.2 m play a negligible r6le in the F-corona. Key words: interplanetary dust - F-corona - circumstellar envelopes - infrared spectrum Title: Infrared Photometry of the Outer Corona. Authors: Lamy, Ph. L.; Koutchmy, S. Bibcode: 1974BAAS....6..311L Altcode: No abstract at ADS