Author name code: schuehle ADS astronomy entries on 2022-09-14 =author:"Schuele, U." OR author:"Schuehle, Udo" ------------------------------------------------------------------------ Title: What drives decayless kink oscillations in active region coronal loops on the Sun? Authors: Mandal, Sudip; Chitta, Lakshmi P.; Antolin, Patrick; Peter, Hardi; Solanki, Sami K.; Auchère, Frédéric; Berghmans, David; Zhukov, Andrei N.; Teriaca, Luca; Cuadrado, Regina A.; Schühle, Udo; Parenti, Susanna; Buchlin, Éric; Harra, Louise; Verbeeck, Cis; Kraaikamp, Emil; Long, David M.; Rodriguez, Luciano; Pelouze, Gabriel; Schwanitz, Conrad; Barczynski, Krzysztof; Smith, Phil J. Bibcode: 2022arXiv220904251M Altcode: We study here the phenomena of decayless kink oscillations in a system of active region (AR) coronal loops. Using high resolution observations from two different instruments, namely the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we follow these AR loops for an hour each on three consecutive days. Our results show significantly more resolved decayless waves in the higher-resolution EUI data compared with the AIA data. Furthermore, the same system of loops exhibits many of these decayless oscillations on Day-2, while on Day-3, we detect very few oscillations and on Day-1, we find none at all. Analysis of photospheric magnetic field data reveals that at most times, these loops were rooted in sunspots, where supergranular flows are generally absent. This suggests that supergranular flows, which are often invoked as drivers of decayless waves, are not necessarily driving such oscillations in our observations. Similarly, our findings also cast doubt on other possible drivers of these waves, such as a transient driver or mode conversion of longitudinal waves near the loop footpoints. In conclusion, through our analysis we find that none of the commonly suspected sources proposed to drive decayless oscillations in active region loops seems to be operating in this event and hence, the search for that elusive wave driver needs to continue. Title: The Lyman-$\alpha$ Emission in a C1.4 Solar Flare Observed by the Extreme Ultraviolet Imager aboard Solar Orbiter Authors: Li, Ying; Li, Qiao; Song, De-Chao; Battaglia, Andrea Francesco; Xiao, Hualin; Krucker, Säm; Schühle, Udo; Li, Hui; Gan, Weiqun; Ding, M. D. Bibcode: 2022arXiv220806182L Altcode: The hydrogen Lyman-$\alpha$ (H {\sc i} Ly$\alpha$) emission during solar flares has rarely been studied in spatially resolved images and its physical origin has not been fully understood. In this paper, we present novel Ly$\alpha$ images for a C1.4 solar flare (SOL2021-08-20T22:00) from the Extreme Ultraviolet Imager aboard Solar Orbiter, together with multi-waveband and multi-perspective observations from the Solar Terrestrial Relations Observatory Ahead and the Solar Dynamics Observatory spacecraft. It is found that the Ly$\alpha$ emission has a good temporal correlation with the thermal emissions at 1--8 Å and 5--7 keV, indicating that the flaring Ly$\alpha$ is mainly produced by a thermal process in this small event. However, nonthermal electrons play a minor role in generating Ly$\alpha$ at flare ribbons during the rise phase of the flare, as revealed by the hard X-ray imaging and spectral fitting. Besides originating from flare ribbons, the Ly$\alpha$ emission can come from flare loops, likely caused by plasma heating and also cooling that happen in different flare phases. It is also found that the Ly$\alpha$ emission shows fairly similar features with the He {\sc ii} 304 Å emission in light curve and spatio-temporal variation along with small differences. These observational results improve our understanding of the Ly$\alpha$ emission in solar flares and also provide some insights for investigating the Ly$\alpha$ emission in stellar flares. Title: A highly dynamic small-scale jet in a polar coronal hole Authors: Mandal, Sudip; Chitta, Lakshmi Pradeep; Peter, Hardi; Solanki, Sami K.; Cuadrado, Regina Aznar; Teriaca, Luca; Schühle, Udo; Berghmans, David; Auchère, Frédéric Bibcode: 2022A&A...664A..28M Altcode: 2022arXiv220602236M We present an observational study of the plasma dynamics at the base of a solar coronal jet, using high resolution extreme ultraviolet imaging data taken by the Extreme Ultraviolet Imager on board Solar Orbiter, and by the Atmospheric Imaging Assembly on board Solar Dynamics Observatory. We observed multiple plasma ejection events over a period of ∼1 h from a dome-like base that is ca. 4 Mm wide and is embedded in a polar coronal hole. Within the dome below the jet spire, multiple plasma blobs with sizes around 1−2 Mm propagate upwards to the dome apex with speeds of the order of the sound speed (ca. 120 km s−1). Upon reaching the apex, some of these blobs initiate flows with similar speeds towards the other footpoint of the dome. At the same time, high speed super-sonic outflows (∼230 km s−1) are detected along the jet spire. These outflows as well as the intensity near the dome apex appear to be repetitive. Furthermore, during its evolution, the jet undergoes many complex morphological changes, including transitions between the standard and blowout type eruption. These new observational results highlight the underlying complexity of the reconnection process that powers these jets and they also provide insights into the plasma response when subjected to rapid energy injection.

Movies associated to Figs. 1, 2, and 4 are available at https://www.aanda.org 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: The on-ground data reduction and calibration pipeline for SO/PHI-HRT Authors: Sinjan, J.; Calchetti, D.; Hirzberger, J.; Orozco Suárez, D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutierrez Marquez, P.; Kahil, F.; Kolleck, M.; Solanki, S. K.; del Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Carmona, M.; Deutsch, W.; Fernandez-Rico, G.; Fernández-Medina, A.; García Parejo, P.; Gasent Blesa, J. L.; Gizon, L.; Grauf, B.; Heerlein, K.; Korpi-Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.; Torralbo, I.; Valori, G. Bibcode: 2022arXiv220814904S Altcode: The ESA/NASA Solar Orbiter space mission has been successfully launched in February 2020. Onboard is the Polarimetric and Helioseismic Imager (SO/PHI), which has two telescopes, a High Resolution Telescope (HRT) and the Full Disc Telescope (FDT). The instrument is designed to infer the photospheric magnetic field and line-of-sight velocity through differential imaging of the polarised light emitted by the Sun. It calculates the full Stokes vector at 6 wavelength positions at the Fe I 617.3 nm absorption line. Due to telemetry constraints, the instrument nominally processes these Stokes profiles onboard, however when telemetry is available, the raw images are downlinked and reduced on ground. Here the architecture of the on-ground pipeline for HRT is presented, which also offers additional corrections not currently available on board the instrument. The pipeline can reduce raw images to the full Stokes vector with a polarimetric sensitivity of $10^{-3}\cdot I_{c}$ or better. Title: Coronal Microjets in Quiet-sun Regions Observed with the Extreme Ultraviolet Imager Onboard Solar Orbiter Authors: Hou, Zhenyong; He, Jiansen; Berghmans, David; Teriaca, Luca; Wang, Linghua; Schuehle, Udo; Tian, Hui; Chen, Yajie; Chen, Hechao; Gao, Yuhang; Bai, Xianyong Bibcode: 2022cosp...44.2536H Altcode: We report the smallest coronal jets ever observed in the quiet Sun with recent high resolution observations from the High Resolution Telescopes (HRI-EUV and HRI-Lyα) of the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter. In the HRI-EUV (174 Å) images, these microjets usually appear as nearly collimated structures with brightenings at their footpoints. Their average lifetime, projected speed, width, and maximum length are 4.6 min, 62 km $s^{-1}$, 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs can be identified in some events. A subset of these events also reveal signatures in the HRI-Lyα (H I Lyα at 1216 Å) images and the extreme ultraviolet images taken by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Our differential emission measure analysis suggests a multi-thermal nature and an average density of ~1.4x10^9 $cm^{-3}$ for these microjets. Their thermal and kinetic energies were estimated to be ~3.9x10$^{24}$ erg and ~2.9x10$^{23}$ erg, respectively, which are of the same order of the released energy predicted by the nanoflare theory. Most events appear to be located at the edges of network lanes and magnetic flux concentrations, suggesting that these coronal microjets are likely generated by magnetic reconnection between small-scale magnetic loops and the adjacent network field. Title: Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI Authors: Alipour, N.; Safari, H.; Verbeeck, C.; Berghmans, D.; Auchère, F.; Chitta, L. P.; Antolin, P.; Barczynski, K.; Buchlin, É.; Aznar Cuadrado, R.; Dolla, L.; Georgoulis, M. K.; Gissot, S.; Harra, L.; Katsiyannis, A. C.; Long, D. M.; Mandal, S.; Parenti, S.; Podladchikova, O.; Petrova, E.; Soubrié, É.; Schühle, U.; Schwanitz, C.; Teriaca, L.; West, M. J.; Zhukov, A. N. Bibcode: 2022A&A...663A.128A Altcode: 2022arXiv220404027A Context. Accurate detections of frequent small-scale extreme ultraviolet (EUV) brightenings are essential to the investigation of the physical processes heating the corona.
Aims: We detected small-scale brightenings, termed campfires, using their morphological and intensity structures as observed in coronal EUV imaging observations for statistical analysis.
Methods: We applied a method based on Zernike moments and a support vector machine (SVM) classifier to automatically identify and track campfires observed by Solar Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA).
Results: This method detected 8678 campfires (with length scales between 400 km and 4000 km) from a sequence of 50 High Resolution EUV telescope (HRIEUV) 174 Å images. From 21 near co-temporal AIA images covering the same field of view as EUI, we found 1131 campfires, 58% of which were also detected in HRIEUV images. In contrast, about 16% of campfires recognized in HRIEUV were detected by AIA. We obtain a campfire birthrate of 2 × 10−16 m−2 s−1. About 40% of campfires show a duration longer than 5 s, having been observed in at least two HRIEUV images. We find that 27% of campfires were found in coronal bright points and the remaining 73% have occurred out of coronal bright points. We detected 23 EUI campfires with a duration greater than 245 s. We found that about 80% of campfires are formed at supergranular boundaries, and the features with the highest total intensities are generated at network junctions and intense H I Lyman-α emission regions observed by EUI/HRILya. The probability distribution functions for the total intensity, peak intensity, and projected area of campfires follow a power law behavior with absolute indices between 2 and 3. This self-similar behavior is a possible signature of self-organization, or even self-organized criticality, in the campfire formation process.

Supplementary material (S1-S3) is available at https://www.aanda.org Title: The SPICE spectrograph on Solar Orbiter: an introduction and results from the first Orbits Authors: Auchère, Frédéric; Peter, Hardi; Parenti, Susanna; Buchlin, Eric; Thompson, William; Auchere, Frederic; Teriaca, Luca; Kucera, Therese; Carlsson, Mats; Janvier, Miho; Fludra, Andrzej; Giunta, Alessandra; Schuehle, Udo; Hassler, Donald M.; Grundy, Timothy; Sidher, Sunil; Fredvik, Terje; Plowman, Joseph; Aznar Cuadrado, Regina Bibcode: 2022cosp...44.1338A Altcode: The Spectral Imaging of the Coronal Environment (SPICE) instrument is the EUV imaging spectrometer on board the Solar Orbiter mission. With its ability to derive physical properties of the coronal plasma, SPICE is a key component of the payload to establish the connection between the source regions and the in-situ measurements of the solar wind. The spacecraft was successfully launched in February 2020 and completed its cruise phase in December 2021. During this period, the remote sensing instruments were mostly operated during limited periods of time for 'checkout' engineering activities and synoptic observations. Nonetheless, several of these periods provided enough opportunities already to obtain new insights on coronal physics. During the march 2022 perihelion - close to 0.3 AU - SPICE will provide its highest spatial resolution data so far. Coordinated observations between the remote sensing and in-situ instruments will provide the first opportunity to use the full potential of the Solar Orbiter mission. We will review the instrument characteristics and present initial results from the cruise phase and first close encounter. Title: Observation of Magnetic Switchback in the Solar Corona Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco; Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta, Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman; Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia; Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto; Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania; Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati, Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio; Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère, Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise; Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna; Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo; Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N. Bibcode: 2022arXiv220603090T Altcode: Switchbacks are sudden, large radial deflections of the solar wind magnetic field, widely revealed in interplanetary space by the Parker Solar Probe. The switchbacks' formation mechanism and sources are still unresolved, although candidate mechanisms include Alfvénic turbulence, shear-driven Kelvin-Helmholtz instabilities, interchange reconnection, and geometrical effects related to the Parker spiral. This Letter presents observations from the Metis coronagraph onboard Solar Orbiter of a single large propagating S-shaped vortex, interpreted as first evidence of a switchback in the solar corona. It originated above an active region with the related loop system bounded by open-field regions to the East and West. Observations, modeling, and theory provide strong arguments in favor of the interchange reconnection origin of switchbacks. Metis measurements suggest that the initiation of the switchback may also be an indicator of the origin of slow solar wind. Title: The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.; Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti, D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina, A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.; Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.; Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans, D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S. Bibcode: 2022A&A...660A.143K Altcode: 2022arXiv220213859K Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SO) spacecraft observed small extreme ultraviolet (EUV) bursts, termed campfires, that have been proposed to be brightenings near the apexes of low-lying loops in the quiet-Sun atmosphere. The underlying magnetic processes driving these campfires are not understood.
Aims: During the cruise phase of SO and at a distance of 0.523 AU from the Sun, the Polarimetric and Helioseismic Imager on Solar Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI, offering the possibility to investigate the surface magnetic field dynamics underlying campfires at a spatial resolution of about 380 km.
Methods: We used co-spatial and co-temporal data of the quiet-Sun network at disc centre acquired with the High Resolution Imager of SO/EUI at 17.4 nm (HRIEUV, cadence 2 s) and the High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5 min). Campfires that are within the SO/PHI−SO/EUI common field of view were isolated and categorised according to the underlying magnetic activity.
Results: In 71% of the 38 isolated events, campfires are confined between bipolar magnetic features, which seem to exhibit signatures of magnetic flux cancellation. The flux cancellation occurs either between the two main footpoints, or between one of the footpoints of the loop housing the campfire and a nearby opposite polarity patch. In one particularly clear-cut case, we detected the emergence of a small-scale magnetic loop in the internetwork followed soon afterwards by a campfire brightening adjacent to the location of the linear polarisation signal in the photosphere, that is to say near where the apex of the emerging loop lays. The rest of the events were observed over small scattered magnetic features, which could not be identified as magnetic footpoints of the campfire hosting loops.
Conclusions: The majority of campfires could be driven by magnetic reconnection triggered at the footpoints, similar to the physical processes occurring in the burst-like EUV events discussed in the literature. About a quarter of all analysed campfires, however, are not associated to such magnetic activity in the photosphere, which implies that other heating mechanisms are energising these small-scale EUV brightenings. Title: Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI Authors: Zhukov, A. N.; Mierla, M.; Auchère, F.; Gissot, S.; Rodriguez, L.; Soubrié, E.; Thompson, W. T.; Inhester, B.; Nicula, B.; Antolin, P.; Parenti, S.; Buchlin, É.; Barczynski, K.; Verbeeck, C.; Kraaikamp, E.; Smith, P. J.; Stegen, K.; Dolla, L.; Harra, L.; Long, D. M.; Schühle, U.; Podladchikova, O.; Aznar Cuadrado, R.; Teriaca, L.; Haberreiter, M.; Katsiyannis, A. C.; Rochus, P.; Halain, J. -P.; Jacques, L.; Berghmans, D. Bibcode: 2021A&A...656A..35Z Altcode: 2021arXiv210902169Z Context. The three-dimensional fine structure of the solar atmosphere is still not fully understood as most of the available observations are taken from a single vantage point.
Aims: The goal of the paper is to study the three-dimensional distribution of the small-scale brightening events ("campfires") discovered in the extreme-UV quiet Sun by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter.
Methods: We used a first commissioning data set acquired by the EUI's High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and we combined it with simultaneous data taken by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171 Å passband. The two-pixel spatial resolution of the two telescopes is 400 km and 880 km, respectively, which is sufficient to identify the campfires in both data sets. The two spacecraft had an angular separation of around 31.5° (essentially in heliographic longitude), which allowed for the three-dimensional reconstruction of the campfire position. These observations represent the first time that stereoscopy was achieved for brightenings at such a small scale. Manual and automatic triangulation methods were used to characterize the campfire data.
Results: The height of the campfires is located between 1000 km and 5000 km above the photosphere and we find a good agreement between the manual and automatic methods. The internal structure of campfires is mostly unresolved by AIA; however, for a particularly large campfire, we were able to triangulate a few pixels, which are all in a narrow range between 2500 and 4500 km.
Conclusions: We conclude that the low height of EUI campfires suggests that they belong to the previously unresolved fine structure of the transition region and low corona of the quiet Sun. They are probably apexes of small-scale dynamic loops heated internally to coronal temperatures. This work demonstrates that high-resolution stereoscopy of structures in the solar atmosphere has become feasible. Title: Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI Authors: Zhukov, Andrei; Mierla, Marilena; Auchere, F.; Gissot, Samuel; Rodriguez, Luciano; Soubrie, Elie; Thompson, William; Inhester, Bernd; Nicula, Bogdan; Antolin, Patrick; Parenti, Susanna; Buchlin, Eric; Barczynski, Krzysztof; Verbeeck, Cis; Kraaikamp, Emil; Smith, Philip; Stegen, Koen; Dolla, Laurent; Harra, Louise; Long, David; Schuhle, Udo; Podladchikova, Olena; Aznar Cuadrado, Regina; Teriaca, Luca; Haberreiter, Margit; Katsiyannis, Athanassios; Rochus, Pierre; Halain, Jean-Philippe; Jacques, Lionel; Berghmans, David Bibcode: 2021AGUFMSH21A..03Z Altcode: We study the three-dimensional distribution of small-scale brightening events (campfires) discovered in the extreme-ultraviolet (EUV) quiet Sun by the EUI telescope onboard the Solar Orbiter mission. We use one of the first commissioning data sets acquired by the HRI_EUV telescope of EUI on 2020 May 30 in the 174 A passband, combined with the simultaneous SDO/AIA dataset taken in the very similar 171 A passband. The spatial resolution of the two telescopes is sufficient to identify the campfires in both datasets. The angular separation between the two spacecraft of around 31.5 degrees allowed for the three-dimensional reconstruction of the position of campfires. This is the first time that stereoscopy was achieved for structures at such a small scale. Manual and automatic triangulation methods were used. The height of campfires is between 1000 km and 5000 km above the photosphere, and there is a good agreement between the results of manual and automatic methods. The internal structure of campfires is mostly not resolved by AIA, but for a large campfire we could triangulate a few pixels, which are all in a narrow height range between 2500 and 4500 km. The low height of campfires suggests that they belong to the previously unresolved fine structure of the transition region and low corona of the quiet Sun. They are probably apexes of small-scale dynamic loops internally heated to coronal temperatures. This work demonstrates that high-resolution stereoscopy of structures in the solar atmosphere has become possible. Title: Propagating brightenings in small loop-like structures in the quiet-Sun corona: Observations from Solar Orbiter/EUI Authors: Mandal, Sudip; Peter, Hardi; Chitta, Lakshmi Pradeep; Solanki, Sami K.; Aznar Cuadrado, Regina; Teriaca, Luca; Schühle, Udo; Berghmans, David; Auchère, Frédéric Bibcode: 2021A&A...656L..16M Altcode: 2021arXiv211108106M Brightenings observed in solar extreme-ultraviolet images are generally interpreted as signatures of micro- or nanoflares occurring in the transition region or at coronal temperatures. Recent observations with the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have revealed the smallest of such brightenings (called campfires) in the quiet-Sun corona. Analyzing EUI 174 Å data obtained at a resolution of about 400 km on the Sun with a cadence of 5 s on 30 May 2020, we report here a number of cases in which these campfires exhibit propagating signatures along their apparently small (3-5 Mm) loop-like structures. The measured propagation speeds are generally between 25 km s−1 and 60 km s−1. If the loop plasma is assumed to be at a million Kelvin, these apparent motions would be slower than the local sound speed. Furthermore, these brightenings exhibit nontrivial propagation characteristics such as bifurcation, merging, reflection, and repeated plasma ejections. We suggest that these features are manifestations of the internal dynamics of these small-scale magnetic structures and could provide important insights into the dynamic response (∼40 s) of the loop plasma to the heating events and also into the locations of the heating events themselves.

Movies associated to Figs 2-5, A.1, and B.1 are available at https://www.aanda.org 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: Extreme-UV quiet Sun brightenings observed by the Solar Orbiter/EUI Authors: Berghmans, D.; Auchère, F.; Long, D. M.; Soubrié, E.; Mierla, M.; Zhukov, A. N.; Schühle, U.; Antolin, P.; Harra, L.; Parenti, S.; Podladchikova, O.; Aznar Cuadrado, R.; Buchlin, É.; Dolla, L.; Verbeeck, C.; Gissot, S.; Teriaca, L.; Haberreiter, M.; Katsiyannis, A. C.; Rodriguez, L.; Kraaikamp, E.; Smith, P. J.; Stegen, K.; Rochus, P.; Halain, J. P.; Jacques, L.; Thompson, W. T.; Inhester, B. Bibcode: 2021A&A...656L...4B Altcode: 2021arXiv210403382B Context. The heating of the solar corona by small heating events requires an increasing number of such events at progressively smaller scales, with the bulk of the heating occurring at scales that are currently unresolved.
Aims: The goal of this work is to study the smallest brightening events observed in the extreme-UV quiet Sun.
Methods: We used commissioning data taken by the Extreme Ultraviolet Imager (EUI) on board the recently launched Solar Orbiter mission. On 30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its High Resolution EUV telescope (HRIEUV, 17.4 nm passband) reached an exceptionally high two-pixel spatial resolution of 400 km. The size and duration of small-scale structures was determined by the HRIEUV data, while their height was estimated from triangulation with simultaneous images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory mission. This is the first stereoscopy of small-scale brightenings at high resolution.
Results: We observed small localised brightenings, also known as `campfires', in a quiet Sun region with length scales between 400 km and 4000 km and durations between 10 s and 200 s. The smallest and weakest of these HRIEUV brightenings have not been previously observed. Simultaneous observations from the EUI High-resolution Lyman-α telescope (HRILya) do not show localised brightening events, but the locations of the HRIEUV events clearly correspond to the chromospheric network. Comparisons with simultaneous AIA images shows that most events can also be identified in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA, although they appear weaker and blurred. Our differential emission measure analysis indicated coronal temperatures peaking at log T ≈ 6.1 − 6.15. We determined the height for a few of these campfires to be between 1000 and 5000 km above the photosphere.
Conclusions: We find that `campfires' are mostly coronal in nature and rooted in the magnetic flux concentrations of the chromospheric network. We interpret these events as a new extension to the flare-microflare-nanoflare family. Given their low height, the EUI `campfires' could stand as a new element of the fine structure of the transition region-low corona, that is, as apexes of small-scale loops that undergo internal heating all the way up to coronal temperatures. Title: Capturing transient plasma flows and jets in the solar corona Authors: Chitta, L. P.; Solanki, S. K.; Peter, H.; Aznar Cuadrado, R.; Teriaca, L.; Schühle, U.; Auchère, F.; Berghmans, D.; Kraaikamp, E.; Gissot, S.; Verbeeck, C. Bibcode: 2021A&A...656L..13C Altcode: 2021arXiv210915106C Intensity bursts in ultraviolet (UV) to X-ray wavelengths and plasma jets are typical signatures of magnetic reconnection and the associated impulsive heating of the solar atmospheric plasma. To gain new insights into the process, high-cadence observations are required to capture the rapid response of plasma to magnetic reconnection as well as the highly dynamic evolution of jets. Here, we report the first 2 s cadence extreme-UV observations recorded by the 174 Å High Resolution Imager of the Extreme Ultraviolet Imager on board the Solar Orbiter mission. These observations, covering a quiet-Sun coronal region, reveal the onset signatures of magnetic reconnection as localized heating events. These localized sources then exhibit repeated plasma eruptions or jet activity. Our observations show that this spatial morphological change from localized sources to jet activity could occur rapidly on timescales of about 20 s. The jets themselves are intermittent and are produced from the source region on timescales of about 20 s. In the initial phases of these events, plasma jets are observed to exhibit speeds, as inferred from propagating intensity disturbances, in the range of 100 km s−1 to 150 km s−1. These jets then propagate to lengths of about 5 Mm. We discuss examples of bidirectional and unidirectional jet activity observed to have been initiated from the initially localized bursts in the corona. The transient nature of coronal bursts and the associated plasma flows or jets along with their dynamics could provide a benchmark for magnetic reconnection models of coronal bursts and jets.

Movies are available at https://www.aanda.org Title: Cosmic-ray flux predictions and observations for and with Metis on board Solar Orbiter Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi, M.; Gissot, S.; Naletto, G.; Persici, A.; Plainaki, C.; Romoli, M.; Sabbatini, F.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M.; Antonucci, E.; Bemporad, A.; Capobianco, G.; Capuano, G.; Casti, M.; De Leo, Y.; Fineschi, S.; Frassati, F.; Frassetto, F.; Heinzel, P.; Jerse, G.; Landini, F.; Liberatore, A.; Magli, E.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Schühle, U.; Slemer, A.; Straus, T.; Susino, R.; Teriaca, L.; Volpicelli, C. A.; Freiherr von Forstner, J. L.; Zuppella, P. Bibcode: 2021A&A...656A..15G Altcode: 2021arXiv210413700G Context. The Metis coronagraph is one of the remote sensing instruments hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted to carry out the first simultaneous imaging of the solar corona in both visible light (VL) and ultraviolet (UV). High-energy particles can penetrate spacecraft materials and may limit the performance of the on-board instruments. A study of the galactic cosmic-ray (GCR) tracks observed in the first VL images gathered by Metis during the commissioning phase is presented here. A similar analysis is planned for the UV channel.
Aims: We aim to formulate a prediction of the GCR flux up to hundreds of GeV for the first part of the Solar Orbiter mission to study the performance of the Metis coronagraph.
Methods: The GCR model predictions are compared to observations gathered on board Solar Orbiter by the High-Energy Telescope in the range between 10 MeV and 100 MeV in the summer of 2020 as well as with the previous measurements. Estimated cosmic-ray fluxes above 70 MeV n−1 have been also parameterized and used for Monte Carlo simulations aimed at reproducing the cosmic-ray track observations in the Metis coronagraph VL images. The same parameterizations can also be used to study the performance of other detectors.
Results: By comparing observations of cosmic-ray tracks in the Metis VL images with FLUKA Monte Carlo simulations of cosmic-ray interactions in the VL detector, we find that cosmic rays fire only a fraction, on the order of 10−4, of the whole image pixel sample. We also find that the overall efficiency for cosmic-ray identification in the Metis VL images is approximately equal to the contribution of Z ≥ 2 GCR particles. A similar study will be carried out during the whole of the Solar Orbiter's mission duration for the purposes of instrument diagnostics and to verify whether the Metis data and Monte Carlo simulations would allow for a long-term monitoring of the GCR proton flux. Title: First observations from the SPICE EUV spectrometer on Solar Orbiter Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest, S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest, C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.; Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.; Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.; Chitta, L. P. Bibcode: 2021A&A...656A..38F Altcode: 2021arXiv211011252F
Aims: We present first science observations taken during the commissioning activities of the Spectral Imaging of the Coronal Environment (SPICE) instrument on the ESA/NASA Solar Orbiter mission. SPICE is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths. In this paper we illustrate the possible types of observations to give prospective users a better understanding of the science capabilities of SPICE.
Methods: We have reviewed the data obtained by SPICE between April and June 2020 and selected representative results obtained with different slits and a range of exposure times between 5 s and 180 s. Standard instrumental corrections have been applied to the raw data.
Results: The paper discusses the first observations of the Sun on different targets and presents an example of the full spectra from the quiet Sun, identifying over 40 spectral lines from neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur, magnesium, and iron. These lines cover the temperature range between 20 000 K and 1 million K (10 MK in flares), providing slices of the Sun's atmosphere in narrow temperature intervals. We provide a list of count rates for the 23 brightest spectral lines. We show examples of raster images of the quiet Sun in several strong transition region lines, where we have found unusually bright, compact structures in the quiet Sun network, with extreme intensities up to 25 times greater than the average intensity across the image. The lifetimes of these structures can exceed 2.5 hours. We identify them as a transition region signature of coronal bright points and compare their areas and intensity enhancements. We also show the first above-limb measurements with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and far off limb measurements in the equatorial plane in Mg IX, Ne VIII, and O VI lines. We discuss the potential to use abundance diagnostics methods to study the variability of the elemental composition that can be compared with in situ measurements to help confirm the magnetic connection between the spacecraft location and the Sun's surface, and locate the sources of the solar wind.
Conclusions: The SPICE instrument successfully performs measurements of EUV spectra and raster images that will make vital contributions to the scientific success of the Solar Orbiter mission. 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: Exploring the Solar Wind from Its Source on the Corona into the Inner Heliosphere during the First Solar Orbiter-Parker Solar Probe Quadrature Authors: Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester; Bemporad, Alessandro; Capuano, Giuseppe E.; Fineschi, Silvano; Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui F.; Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd D.; Zank, Gary P.; Romoli, Marco; Bale, Stuart D.; Kasper, Justin C.; Auchère, Frédéric; Bruno, Roberto; Capobianco, Gerardo; Case, Anthony W.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso, Alain J.; Da Deppo, Vania; De Leo, Yara; Dudok de Wit, Thierry; Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino, Salvo L.; Harvey, Peter R.; Heinzel, Petr; Jerse, Giovanna; Korreck, Kelly E.; Landini, Federico; Larson, Davin; Liberatore, Alessandro; Livi, Roberto; MacDowall, Robert J.; Magli, Enrico; Malaspina, David M.; Massone, Giuseppe; Messerotti, Mauro; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo; Nisticò, Giuseppe; Panasenco, Olga; Pancrazzi, Maurizio; Pelizzo, Maria G.; Pulupa, Marc; Reale, Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini, Marco; Stevens, Michael L.; Strachan, Leonard; Straus, Thomas; Teriaca, Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli, Cosimo A.; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano; Zuppella, Paola Bibcode: 2021ApJ...920L..14T Altcode: 2021arXiv211011031T This Letter addresses the first Solar Orbiter (SO)-Parker Solar Probe (PSP) quadrature, occurring on 2021 January 18 to investigate the evolution of solar wind from the extended corona to the inner heliosphere. Assuming ballistic propagation, the same plasma volume observed remotely in the corona at altitudes between 3.5 and 6.3 solar radii above the solar limb with the Metis coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing the local properties of the solar wind to be linked to the coronal source region from where it originated. Thanks to the close approach of PSP to the Sun and the simultaneous Metis observation of the solar corona, the flow-aligned magnetic field and the bulk kinetic energy flux density can be empirically inferred along the coronal current sheet with an unprecedented accuracy, allowing in particular estimation of the Alfvén radius at 8.7 solar radii during the time of this event. This is thus the very first study of the same solar wind plasma as it expands from the sub-Alfvénic solar corona to just above the Alfvén surface. Title: Coronal Microjets in Quiet-Sun Regions Observed with the Extreme Ultraviolet Imager on Board the Solar Orbiter Authors: Hou, Zhenyong; Tian, Hui; Berghmans, David; Chen, Hechao; Teriaca, Luca; Schühle, Udo; Gao, Yuhang; Chen, Yajie; He, Jiansen; Wang, Linghua; Bai, Xianyong Bibcode: 2021ApJ...918L..20H Altcode: 2021arXiv210808718H We report the smallest coronal jets ever observed in the quiet Sun with recent high-resolution observations from the High Resolution Telescopes (HRIEUV and HRILyα) of the Extreme Ultraviolet Imager on board the Solar Orbiter (SO). In the HRIEUV (174 Å) images, these microjets usually appear as nearly collimated structures with brightenings at their footpoints. Their average lifetime, projected speed, width, and maximum length are 4.6 minutes, 62 km s-1, 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs can be identified in some events. A subset of these events also reveal signatures in the HRILyα (H I Lyα at 1216 Å) images and the extreme ultraviolet images taken by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). Our differential emission-measure (EM) analysis suggests a multithermal nature and an average density of ~1.4 × 109 cm-3 for these microjets. Their thermal and kinetic energies were estimated to be ~3.9 × 1024 erg and ~2.9 × 1023 erg, respectively, which are of the same order of the released energy predicted by the nanoflare theory. Most events appear to be located at the edges of network lanes and magnetic flux concentrations, suggesting that these coronal microjets are likely generated by magnetic reconnection between small-scale magnetic loops and the adjacent network field. Title: Challenges during Metis-Solar Orbiter commissioning phase Authors: Romoli, Marco; Andretta, Vincenzo; Bemporad, Alessandro; Casti, Marta; Da Deppo, Vania; De Leo, Yara; Fabi, Michele; Fineschi, Silvano; Frassetto, Fabio; Grimani, Catia; Heerlein, Klaus; Heinzel, Petr; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli, Enrico; Naletto, Giampiero; Nicolini, Gianalfredo; Pancrazzi, Maurizio; Pelizzo, Maria Guglielmina; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Slemer, Alessandra; Spadaro, Daniele; Straus, Thomas; Susino, Roberto; Teriaca, Luca; Uslenghi, Michela; Volpicelli, Cosimo Antonio; Zupella, Paola Bibcode: 2021SPIE11852E..5AR Altcode: Metis is the visible light and UV light imaging coronagraph on board the ESA-NASA mission Solar Orbiter that has been launched February 10th, 2020, from Cape Canaveral. Scope of the mission is to study the Sun up close, taking high-resolution images of the Sun's poles for the first time, and understanding the Sun-Earth connection. Metis coronagraph will image the solar corona in the linearly polarized broadband visible radiation and in the UV HI Ly-α line from 1.6 to 3 solar radii when at Solar Orbiter perihelion, providing a diagnostics, with unprecedented temporal coverage and spatial resolution, of the structures and dynamics of the full corona. Solar Orbiter commissioning phase big challenge was Covid-19 social distancing phase that affected the way commissioning of a spacecraft and its payload is typically done. Metis coronagraph on-board Solar Orbiter had its additional challenges: to wake up and check the performance of the optical, electrical and thermal subsystems, most of them unchecked since Metis delivery to spacecraft prime, Airbus, in May 2017. The roadmap to the fully commissioned coronagraph is here described throughout the steps from the software functional test, the switch on of the detectors of the two channels, UV and visible, to the optimization of the occulting system and the characterization of the instrumental stray light, one of the most challenging features in a coronagraph. Title: Calibrating Optical Distortions In The Solar Orbiter Spice Spectrograph Authors: Thompson, W.; Schühle, U.; Young, P. Bibcode: 2021AAS...23831302T Altcode: The Spectral Imaging of the Coronal Environment (SPICE) instrument on SolarOrbiter is a high-resolution imaging spectrometer operating at extremeultraviolet (EUV) wavelengths from 70.4-79.0 nm and 97.3-104.9 nm. Asingle-mirror off-axis paraboloid focuses the solar image onto the entranceslit of the spectrometer section. A Toroidal Variable Line Space (TVLS)grating images the entrance slit onto a pair of MCP-intensified APS detectors.Ray-tracing analysis prior to launch showed that the instrument was subject toa number of small image distortions which need to be corrected in the finaldata product. We compare the ray tracing results with measurements made inflight. Co-alignment with other telescopes on Solar Orbiter will also beexamined. Title: The Extreme ultraviolet imager onboard Solar Orbiter Authors: Berghmans, David; Harra, Louise K.; Zhukov, Andrei; Auchere, Frederic; Long, David; Schuehle, Udo; Rochus, Pierre Bibcode: 2021cosp...43E.949B Altcode: The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. With EUI we aim to improve our understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives. The EUI consists of three telescopes, the Full Sun Imager (FSI) and two High Resolution Imagers (HRIs), which are optimised to image in Lyman-$\alpha$ and EUV (174 \AA, 304 \AA) to provide a coverage from chromosphere up to corona. The EUI instrument design will be reviewed, and its scientific objectives and plans will be discussed. Early results of the EUI commissioning will be presented. Title: Relative coronal abundance diagnostics with Solar Orbiter/SPICE Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.; Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado, R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca, L.; Thompson, W. T.; Williams, D. Bibcode: 2020AGUFMSH038..09Z Altcode: Linking solar activity on the surface and in the corona to the inner heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer SPICE (SPectral Imaging of the Coronal Environment) will provide relative abundance measurements which will be key in this quest as different structures on the Sun have different abundances as a consequence of the FIP (First Ionization Potential) effect. Solar Orbiter's unique combination of remote sensing and in-situ instruments coupled with observation from other missions such as Parker Solar Probe will allow us to compare in-situ and remote sensing composition data. With the addition of modeling, these new results will allow us to trace back the source of heliospheric plasma. As high telemetry will not always be available with SPICE, we have developed a method for measuring relative abundances that is both telemetry efficient and reliable. Unlike methods based on Differential Emission Measure (DEM) inversion, the Linear Combination Ratio (LCR) method does not require a large number of spectral lines. This new method is based on linear combinations of UV spectral lines. The coefficients of the combinations are optimized such that the ratio of two linear combinations of radiances would yield the relative abundance of two elements. We present some abundance diagnostics tested on different combinations of spectral lines observable by SPICE. Title: Dynamics and thermal structure in the quiet Sun seen by SPICE Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.; Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH038..03P Altcode: We will present some of the early data of the Spectral Imaging of the Coronal Environment (SPICE) instrument on Solar Orbiter. One of the unique features of SPICE is its capability to record a wide range of wavelengths in the extreme UV with the possibility to record spectral lines giving access to a continuous plasma temperature range from 10.000 K to well above 1 MK. The data taken so far were for commissioning purposes and they can be used for a preliminary evaluation of the science performance of the instrument. Here we will concentrate on sample spectra covering the whole wavelength region and on the early raster maps acquired in bright lines in the quiet Sun close to disk center. Looking at different quiet Sun features we investigate the thermal structure of the atmosphere and flow structures. For this we apply fits to the spectral profiles and check the performance in terms of Doppler shifts and line widths to retrieve the structure of the network in terms of dynamics. While the amount of data available so far is limited, we will have a first look on how quiet Sun plasma responds to heating events. For this, we will compare spectral lines forming at different temperatures recorded at strictly the same time. Title: Observation of Smallest Ever Detected Brightening Events with the Solar Orbiter EUI HRI-EUV Imager Authors: Parenti, S.; Berghmans, D.; Buchlin, E.; Teriaca, L.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado, R.; Gissot, S.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C. Bibcode: 2020AGUFMSH038..01P Altcode: The Extreme Ultraviolet Imager (EUI) suite on board Solar Orbiter acquired its first images in May 2020. The passband of the 17.4 nm High Resolution Imager (HRI-EUV) is dominated by emission lines of Fe IX and Fe X, that is the 1 million degree solar corona. The solar atmosphere at this temperature is dynamic at all scales, down to the highest spatial resolution available from instruments priori to Solar Orbiter. During the Commissioning phase, HRI-EUV acquired several high temporal resolution (a few seconds) sequences at quiet Sun regions at disk center. The instrument revealed a multitude of brightenings at the smallest-ever detectable spatial scales which, at that time, was about 400 km (two pixels). These events appear to be present everywhere all the time. We present the first results of the analysis of these sequences with the aim of understanding the role of these small scale events in the heating of the solar corona. Title: First Results From SPICE EUV Spectrometer on Solar Orbiter Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest, S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik, T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller, D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH038..02F Altcode: SPICE (Spectral Imaging of Coronal Environment) is one of the remote sensing instruments onboard Solar Orbiter. It is an EUV imaging spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm and 96.6-105.1 nm. SPICE is capable of recording full spectra in these bands with exposures as short as 1s. SPICE is the only Solar Orbiter instrument that can measure EUV spectra from the disk and low corona of the Sun and record all spectral lines simultaneously. SPICE uses one of three narrow slits, 2"x11', 4''x11', 6''x11', or a wide slit 30''x14'. The primary mirror can be scanned in a direction perpendicular to the slit, allowing raster images of up to 16' in size.

We present an overview of the first SPICE data taken on several days during the instrument commissioning carried out by the RAL Space team between 2020 April 21 and 2020 June 14. We also include results from SPICE observations at the first Solar Orbiter perihelion at 0.52AU, taken between June 16-21st. We give examples of full spectra from the quiet Sun near disk centre and provide a list of key spectral lines emitted in a range of temperatures between 10,000 K and over 1 million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur and magnesium. We show examples of first raster images in several strong lines, obtained with different slits and a range of exposure times between 5s and 180s. We describe the temperature coverage and density diagnostics, determination of plasma flows, and discuss possible applications to studies of the elemental abundances in the corona. We also show the first off-limb measurements with SPICE, as obtained when the spacecraft pointed at the limb. Title: The Solar-C (EUVST) mission: the latest status Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu, Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto, Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki; Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren, Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca, Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William; Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic; Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise Bibcode: 2020SPIE11444E..0NS Altcode: Solar-C (EUVST) is the next Japanese solar physics mission to be developed with significant contributions from US and European countries. The mission carries an EUV imaging spectrometer with slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic Telescope) as the mission payload, to take a fundamental step towards answering how the plasma universe is created and evolves and how the Sun influences the Earth and other planets in our solar system. In April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA (Japan Aerospace Exploration Agency) has made the final down-selection for this mission as the 4th in the series of competitively chosen M-class mission to be launched with an Epsilon launch vehicle in mid 2020s. NASA (National Aeronautics and Space Administration) has selected this mission concept for Phase A concept study in September 2019 and is in the process leading to final selection. For European countries, the team has (or is in the process of confirming) confirmed endorsement for hardware contributions to the EUVST from the national agencies. A recent update to the mission instrumentation is to add a UV spectral irradiance monitor capability for EUVST calibration and scientific purpose. This presentation provides the latest status of the mission with an overall description of the mission concept emphasizing on key roles of the mission in heliophysics research from mid 2020s. Title: Calibrating optical distortions in the Solar Orbiter SPICE spectrograph Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.; Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.; Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams, D.; Sidher, S. Bibcode: 2020AGUFMSH0360029T Altcode: The Spectral Imaging of the Coronal Environment (SPICE) instrument on Solar Orbiter is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and 97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar image onto the entrance slit of the spectrometer section. A Toroidal Variable Line Space (TVLS) grating images the entrance slit onto a pair of MCP-intensified APS detectors. Ray-tracing analysis prior to launch showed that the instrument was subject to a number of small image distortions which need to be corrected in the final data product. We compare the ray tracing results with measurements made in flight. Co-alignment with other telescopes on Solar Orbiter will also be examined. Title: First results from the EUI and SPICE observations of Alpha Leo near Solar Orbiter first perihelion Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta, V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.; Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.; Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.; Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH0360024B Altcode: On June 16th 2020 Solar Orbiter made a dedicated observing campaign where the spacecraft pointed to the solar limb to allow some of the high resolution instruments to observe the ingress (at the east limb) and later the egress (west limb) of the occultation of the star Alpha Leonis by the solar disk. The star was chosen because its luminosity and early spectral type ensure high and stable flux at wavelengths between 100 and 122 nanometers, a range observed by the High Resolution EUI Lyman alpha telescope (HRI-LYA) and by the long wavelength channel of the SPICE spectrograph. Star observations, when feasible, allow to gather a great deal of information on the instrument performances, such as the radiometric performance and the instrument optical point spread function (PSF).

We report here the first results from the above campaign for the two instruments. Title: Solar Orbiter: connecting remote sensing and in situ measurements Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.; Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra, L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.; Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter, H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.; Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis, Y.; Laker, R. Bibcode: 2020AGUFMSH038..10H Altcode: A key science goal of the Solar Orbiter mission is to make connections between phenomena on the Sun and their manifestations in interplanetary space. To that end, the spacecraft carries a carefully tailored payload of six remote sensing instruments and four making in situ measurements. During June 2020, while the spacecraft was around 0.5 AU from the Sun, the remote sensing instruments operated for several days. While this was primarily an engineering activity, the resulting observations provided outstanding measurements and represent the ideal first opportunity to investigate the potential for making connections between the remote sensing and in situ payloads on Solar Orbiter.

We present a preliminary analysis of the available remote sensing and in situ observations, showing how connections can be made, and discuss the potential for further, more precise mapping to be performed as the mission progresses. Title: First Images and Initial In-Flight Performance of the Extreme Ultraviolet Imager On-Board Solar Orbiter. Authors: Auchere, F.; Gissot, S.; Teriaca, L.; Berghmans, D.; Harra, L.; Long, D.; Rochus, P. L.; Smith, P.; Schühle, U.; Stegen, K.; Aznar Cuadrado, R.; Heerlein, K.; Kraaikamp, E.; Verbeeck, C. Bibcode: 2020AGUFMSH0360025A Altcode: The Extreme Ultraviolet Imager (EUI) on board Solar Orbiter is composed of two High Resolution Imagers working at 121.6 (HRI-LYA, H I, chromosphere) and 17.4 nm (HRI-EUV, Fe IX/X, corona) and one dual-band Full Sun Imager (FSI) working at 30.4 nm (He II, transition region) and 17.4 nm (Fe IX/X, corona). During the commissioning period following the launch of Solar Orbiter and two and a half months of outgassing, EUI acquired its first solar images on May 12th, 2020 at about 0.67 AU. Most of the capabilities of the instrument have been tested during the following weeks, which revealed excellent overall performance. HRI-EUV already provided images with an angular resolution equivalent to ~0.6" (2 pixels) at 1 A.U. HRI-LYA will routinely provide images of the Sun at Lyman alpha, which have been otherwise relatively rare, with sub-second cadence capability. FSI will provide context for connection science but it will also explore regions of the corona never imaged before at EUV wavelengths, owing to its 3.8° field of view. EUI uses a complex on-board image processing system including advanced image compression and event detection algorithms. In particular, commissioning tests confirm the good performance of the compression, which is critical given the limited total telemetry volume imposed by the mission profile. In this paper, we present the main characteristics of the first images taken in each channel and we provide an initial assessment of the in-flight performance. Title: First results from combined EUI and SPICE observations of Lyman lines of Hydrogen and He II Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.; Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.; Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus, P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.; Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH0360003T Altcode: The Solar Orbiter spacecraft carries a powerful set of remote sensing instruments that allow studying the solar atmosphere with unprecedented diagnostic capabilities. Many such diagnostics require the simultaneous usage of more than one instrument. One example of that is the capability, for the first time, to obtain (near) simultaneous spatially resolved observations of the emission from the first three lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact, the SPectral Imaging of the Coronal Environment (SPICE) spectrometer can observe the Lyman beta and gamma lines in its long wavelength (SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take images dominated by the Lyman alpha line of ionized Helium at 30.4 nm (FSI-304). Being hydrogen and helium the main components of our star, these very bright transitions play an important role in the energy budget of the outer atmosphere via radiative losses and the measurement of their profiles and radiance ratios is a fundamental constraint to any comprehensive modelization effort of the upper solar chromosphere and transition region. Additionally, monitoring their average ratios can serve as a check out for the relative radiometric performance of the two instruments throughout the mission. Although the engineering data acquired so far are far from ideal in terms of time simultaneity (often only within about 1 h) and line coverage (often only Lyman beta was acquired by SPICE and not always near simultaneous images from all three telescopes are available) the analysis we present here still offers a great opportunity to have a first look at the potential of this diagnostic from the two instruments. In fact, we have identified a series of datasets obtained at disk center and at various positions at the solar limb that allow studying the Lyman alpha to beta radiance ratio and their relation to He II 30.4 as a function of the position on the Sun (disk center versus limb and quiet Sun versus coronal holes). Title: Very high-resolution observations of the solar atmosphere in H I Lyman alpha and Fe IX-X at 17.4 nm as seen by EUI aboard Solar Orbiter Authors: Aznar Cuadrado, R.; Berghmans, D.; Teriaca, L.; Gissot, S.; Schühle, U.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.; Heerlein, K.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C. Bibcode: 2020AGUFMSH0360026A Altcode: The Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter consists of three telescopes, the Full Sun Imager (FSI) and two High Resolution Imagers (HRIs). The two HRI telescopes provide images of the base of the corona, near to the chromosphere, and of the 1 million K corona. In fact, the HRI-EUV telescope operates around 17.4 nm to obtain images dominated by emission from lines generated from Fe-IX and X ions, formed at about 1 MK, while the HRI-LYA telescope provides narrow band images dominated by the H I Lyman alpha line at 121.6 nm, formed in the upper chromosphere/lower transition region of the solar atmosphere around 20,000 K. Thus, the two imagers provide a powerful diagnostics of the solar structural organization, in terms of loop hierarchies and connectivity. Here we present an analysis of the first two near-simultaneous (within 15s) high-resolution images of the solar quiet atmosphere obtained near disk center by the two high-resolution telescopes on May 30th 2020, during the commissioning phase of the mission , when Solar Orbiter was at about 0.56 AU from the Sun. Title: Coordination within the remote sensing payload on the Solar Orbiter mission Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.; Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade, S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.; Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy, S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.; Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey, B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.; Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi, M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.; Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.; Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.; Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.; Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams, D.; Woch, J.; Zhukov, A. N.; Zouganelis, I. Bibcode: 2020A&A...642A...6A Altcode: Context. To meet the scientific objectives of the mission, the Solar Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing (RS) instruments designed for joint operations with inter-instrument communication capabilities. Indeed, previous missions have shown that the Sun (imaged by the RS instruments) and the heliosphere (mainly sampled by the IS instruments) should be considered as an integrated system rather than separate entities. Many of the advances expected from Solar Orbiter rely on this synergistic approach between IS and RS measurements.
Aims: Many aspects of hardware development, integration, testing, and operations are common to two or more RS instruments. In this paper, we describe the coordination effort initiated from the early mission phases by the Remote Sensing Working Group. We review the scientific goals and challenges, and give an overview of the technical solutions devised to successfully operate these instruments together.
Methods: A major constraint for the RS instruments is the limited telemetry (TM) bandwidth of the Solar Orbiter deep-space mission compared to missions in Earth orbit. Hence, many of the strategies developed to maximise the scientific return from these instruments revolve around the optimisation of TM usage, relying for example on onboard autonomy for data processing, compression, and selection for downlink. The planning process itself has been optimised to alleviate the dynamic nature of the targets, and an inter-instrument communication scheme has been implemented which can be used to autonomously alter the observing modes. We also outline the plans for in-flight cross-calibration, which will be essential to the joint data reduction and analysis.
Results: The RS instrument package on Solar Orbiter will carry out comprehensive measurements from the solar interior to the inner heliosphere. Thanks to the close coordination between the instrument teams and the European Space Agency, several challenges specific to the RS suite were identified and addressed in a timely manner. Title: The Solar Orbiter Science Activity Plan. Translating solar and heliospheric physics questions into action Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.; Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.; Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.; Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.; Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio, L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun, A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso, F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.; Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.; Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.; van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi, L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine, D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot, S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham, G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier, K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins, J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis, I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.; Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis, G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.; Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.; Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis, K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien, H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.; Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.; Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines, J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.; Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.; Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.; Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.; Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.; Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula, G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio, A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.; Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann, T.; Young, P. R.; Zhukov, A. N. Bibcode: 2020A&A...642A...3Z Altcode: 2020arXiv200910772Z Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed. Title: The Polarimetric and Helioseismic Imager on Solar Orbiter Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer, A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.; Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.; Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.; Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.; Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott, D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.; Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.; Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.; Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.; Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.; Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.; Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila, B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.; Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.; Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond, J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h, J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.; Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell, A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai, E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa, J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas, A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.; Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel, H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I. Bibcode: 2020A&A...642A..11S Altcode: 2019arXiv190311061S
Aims: This paper describes the Polarimetric and Helioseismic Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and helioseismology instrument to observe the Sun from outside the Sun-Earth line. It is the key instrument meant to address the top-level science question: How does the solar dynamo work and drive connections between the Sun and the heliosphere? SO/PHI will also play an important role in answering the other top-level science questions of Solar Orbiter, while hosting the potential of a rich return in further science.
Methods: SO/PHI measures the Zeeman effect and the Doppler shift in the Fe I 617.3 nm spectral line. To this end, the instrument carries out narrow-band imaging spectro-polarimetry using a tunable LiNbO3 Fabry-Perot etalon, while the polarisation modulation is done with liquid crystal variable retarders. The line and the nearby continuum are sampled at six wavelength points and the data are recorded by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data are reduced on board, including being inverted under the assumption of a Milne-Eddington atmosphere, although simpler reduction methods are also available on board. SO/PHI is composed of two telescopes; one, the Full Disc Telescope, covers the full solar disc at all phases of the orbit, while the other, the High Resolution Telescope, can resolve structures as small as 200 km on the Sun at closest perihelion. The high heat load generated through proximity to the Sun is greatly reduced by the multilayer-coated entrance windows to the two telescopes that allow less than 4% of the total sunlight to enter the instrument, most of it in a narrow wavelength band around the chosen spectral line.
Results: SO/PHI was designed and built by a consortium having partners in Germany, Spain, and France. The flight model was delivered to Airbus Defence and Space, Stevenage, and successfully integrated into the Solar Orbiter spacecraft. A number of innovations were introduced compared with earlier space-based spectropolarimeters, thus allowing SO/PHI to fit into the tight mass, volume, power and telemetry budgets provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal) challenges posed by the mission's highly elliptical orbit. Title: The Solar Orbiter SPICE instrument. An extreme UV imaging spectrometer Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.; Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini, K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.; Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.; Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau, J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.; Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest, S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler, D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller, S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall, G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris, N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.; Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.; Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy, B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.; Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial, J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward, S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D. Bibcode: 2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
Aims: The Spectral Imaging of the Coronal Environment (SPICE) instrument is a high-resolution imaging spectrometer operating at extreme ultraviolet wavelengths. In this paper, we present the concept, design, and pre-launch performance of this facility instrument on the ESA/NASA Solar Orbiter mission.
Methods: The goal of this paper is to give prospective users a better understanding of the possible types of observations, the data acquisition, and the sources that contribute to the instrument's signal.
Results: The paper discusses the science objectives, with a focus on the SPICE-specific aspects, before presenting the instrument's design, including optical, mechanical, thermal, and electronics aspects. This is followed by a characterisation and calibration of the instrument's performance. The paper concludes with descriptions of the operations concept and data processing.
Conclusions: The performance measurements of the various instrument parameters meet the requirements derived from the mission's science objectives. The SPICE instrument is ready to perform measurements that will provide vital contributions to the scientific success of the Solar Orbiter mission. Title: The Solar Orbiter mission. Science overview Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.; Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.; Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.; Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.; Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.; Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D. Bibcode: 2020A&A...642A...1M Altcode: 2020arXiv200900861M
Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision 2015-2025 programme and a mission of international collaboration between ESA and NASA, will explore the Sun and heliosphere from close up and out of the ecliptic plane. It was launched on 10 February 2020 04:03 UTC from Cape Canaveral and aims to address key questions of solar and heliospheric physics pertaining to how the Sun creates and controls the Heliosphere, and why solar activity changes with time. To answer these, the mission carries six remote-sensing instruments to observe the Sun and the solar corona, and four in-situ instruments to measure the solar wind, energetic particles, and electromagnetic fields. In this paper, we describe the science objectives of the mission, and how these will be addressed by the joint observations of the instruments onboard.
Methods: The paper first summarises the mission-level science objectives, followed by an overview of the spacecraft and payload. We report the observables and performance figures of each instrument, as well as the trajectory design. This is followed by a summary of the science operations concept. The paper concludes with a more detailed description of the science objectives.
Results: Solar Orbiter will combine in-situ measurements in the heliosphere with high-resolution remote-sensing observations of the Sun to address fundamental questions of solar and heliospheric physics. The performance of the Solar Orbiter payload meets the requirements derived from the mission's science objectives. Its science return will be augmented further by coordinated observations with other space missions and ground-based observatories.

ARRAY(0x207ce98) Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz, W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado, R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.; Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel, V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau, M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar, S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.; Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.; Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.; Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud, A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.; Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.; Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan, K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.; Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.; Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq, S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.; Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining, S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort, F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.; Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.; Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.; Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.; Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane, K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit, S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen, K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.; Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.; Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.; Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N. Bibcode: 2020A&A...642A...8R Altcode: Context. The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. Solar Orbiter will advance the "connection science" between solar activity and the heliosphere.
Aims: With EUI we aim to improve our understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.
Methods: The EUI consists of three telescopes, the Full Sun Imager and two High Resolution Imagers, which are optimised to image in Lyman-α and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere up to corona. The EUI is designed to cope with the strong constraints imposed by the Solar Orbiter mission characteristics. Limited telemetry availability is compensated by state-of-the-art image compression, onboard image processing, and event selection. The imposed power limitations and potentially harsh radiation environment necessitate the use of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft's heat shield, the apertures have been kept as small as possible, without compromising optical performance. This led to a systematic effort to optimise the throughput of every optical element and the reduction of noise levels in the sensor.
Results: In this paper we review the design of the two elements of the EUI instrument: the Optical Bench System and the Common Electronic Box. Particular attention is also given to the onboard software, the intended operations, the ground software, and the foreseen data products.
Conclusions: The EUI will bring unique science opportunities thanks to its specific design, its viewpoint, and to the planned synergies with the other Solar Orbiter instruments. In particular, we highlight science opportunities brought by the out-of-ecliptic vantage point of the solar poles, the high-resolution imaging of the high chromosphere and corona, and the connection to the outer corona as observed by coronagraphs. 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: Optical design of the multi-wavelength imaging coronagraph Metis for the solar orbiter mission Authors: Fineschi, S.; Naletto, G.; Romoli, M.; Da Deppo, V.; Antonucci, E.; Moses, D.; Malvezzi, A. M.; Nicolini, G.; Spadaro, D.; Teriaca, L.; Andretta, V.; Capobianco, G.; Crescenzio, G.; Focardi, M.; Frassetto, F.; Landini, F.; Massone, G.; Melich, R.; Nicolosi, P.; Pancrazzi, M.; Pelizzo, M. G.; Poletto, L.; Schühle, U.; Uslenghi, M.; Vives, S.; Solanki, S. K.; Heinzel, P.; Berlicki, A.; Cesare, S.; Morea, D.; Mottini, S.; Sandri, P.; Alvarez-Herrero, A.; Castronuovo, M. Bibcode: 2020ExA....49..239F Altcode: 2020ExA...tmp...14F This paper describes the innovative optical design of the Metis coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a multi-wavelength, externally occulted telescope for the imaging of the solar corona in both the visible and ultraviolet wavelength ranges. Metis adopts a novel occultation scheme for the solar disk, that we named "inverse external occulter", for reducing the extremely high thermal load on the instrument at the spacecraft perihelion. The core of the Metis optical design is an aplanatic Gregorian telescope common to both the visible and ultraviolet channels. A suitable dichroic beam-splitter, optimized for transmitting a narrow-band in the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband in the visible (580-640 nm) spectral range, is used to separate the two optical paths. Along the visible light optical path, a liquid crystal electro-optical modulator, used for the first time in space, allows making polarimetric measurements. Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager Authors: Rochus, P. L.; Auchere, F.; Berghmans, D.; Harra, L.; Schmutz, W. K.; Schühle, U. Bibcode: 2019AGUFMSH21D3291R Altcode: The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out-of-the-ecliptic.

EUI aims at improving our understanding of the structure and dynamics of the solar atmosphere. EUI will take images of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.

EUI consists of 3 telescopes that are optimized to image in Lyman-a and EUV 17.4nm and 30.4 nm to provide a coverage from chromosphere up to corona. EUI is designed to cope with the strong constraints that Solar Orbiter has as a deep space mission. Limited telemetry availability is compensated by state-of-the-art image compression, on board image processing and event selection. The imposed power limitations and potentially harsh radiation environment lead to the usage of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft heat shield, the apertures were kept as small as possible. This lead to a systematic effort to optimize the throughput of every optical element and the reduction of noise levels in the sensor.

In this paper we review the design of the two elements of the EUI instrument: the Optical Bench System and the Common Electronic Box. Particular attention is also given to the on board software, the intended operations, the ground software and the foreseen data products.

EUI will bring unique science opportunities thanks to its specific design, its viewpoint and thanks to the planned synergies with the other Solar Orbiter instruments. We highlight in particular science opportunities brought by the out-of-ecliptic vantage point of the solar poles, the high resolution imaging of the high chromosphere and corona, and the connection to the outer corona as observed by coronagraphs. Title: The Solar-C_EUVST mission Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa, Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama, Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra, Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.; Naletto, G.; Zhukov, A. Bibcode: 2019SPIE11118E..07S Altcode: Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a solar physics mission concept that was selected as a candidate for JAXA competitive M-class missions in July 2018. The onboard science instrument, EUVST, is an EUV spectrometer with slit-jaw imaging system that will simultaneously observe the solar atmosphere from the photosphere/chromosphere up to the corona with seamless temperature coverage, high spatial resolution, and high throughput for the first time. The mission is designed to provide a conclusive answer to the most fundamental questions in solar physics: how fundamental processes lead to the formation of the solar atmosphere and the solar wind, and how the solar atmosphere becomes unstable, releasing the energy that drives solar flares and eruptions. The entire instrument structure and the primary mirror assembly with scanning and tip-tilt fine pointing capability for the EUVST are being developed in Japan, with spectrograph and slit-jaw imaging hardware and science contributions from US and European countries. The mission will be launched and installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in 2025. ISAS/JAXA coordinates the conceptual study activities during the current mission definition phase in collaboration with NAOJ and other universities. The team is currently working towards the JAXA final down-selection expected at the end of 2019, with strong support from US and European colleagues. The paper provides an overall description of the mission concept, key technologies, and the latest status. Title: Optical alignment of the Solar Orbiter EUI flight instrument Authors: Mazzoli, A.; Halain, J. -P.; Auchère, F.; Barbay, J.; Meining, S.; Philippon, A.; Morinaud, G.; Roose, S.; Hellin, M. -L.; Jacques, L.; Schühle, U.; Dumesnil, C.; Mercier, R.; Renotte, E.; Rochus, P. Bibcode: 2019SPIE11180E..1OM Altcode: The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter mission will image the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). It is composed of three channels, each one containing a telescope. Two of these channels are high resolution imagers (HRI) at respectively 17.1 nm (HRI-EUV) and 121.6 nm (HRI-Ly ), each one composed of two off-axis aspherical mirrors. The third channel is a full sun imager (FSI) composed of one single off-axis aspherical mirror and working at 17.1 nm and 30.4 nm alternatively. This paper presents the optical alignment of each telescope. The alignment process involved a set of Optical Ground Support Equipment (OGSE) such as theodolites, laser tracker, visible-light interferometer as well as a 3D Coordinates Measuring Machine (CMM). The mirrors orientation have been measured with respect to reference alignment cubes using theodolites. Their positions with respect to reference pins on the instrument optical bench have been measured using the 3D CMM. The mirrors orientations and positions have been adjusted by shimming of the mirrors mount during the alignment process. After this mechanical alignment, the quality of the wavefront has been checked by interferometric measurements, in an iterative process with the orientation and position adjustment to achieve the required image quality. Title: Optical performance of the Metis coronagraph on the Solar Orbiter ESA mission Authors: Frassetto, Fabio; Da Deppo, Vania; Zuppella, Paola; Romoli, Marco; Fineschi, Silvano; Antonucci, Ester; Nicolini, Giana; Naletto, Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo; Castronuovo, Marco; Casti, Marta; Capobianco, Gerardo; Massone, Giuseppe; Susino, Roberto; Landini, Federico; Pancrazzi, Maurizio; Teriaca, Luca; Schühle, Udo; Heerlein, Klaus; Uslenghi, Michela Bibcode: 2019SPIE11180E..6YF Altcode: The Metis coronagraph aboard the Solar Orbiter ESA spacecraft is expected to provide new insights into the solar dynamics. In detail, it is designed to address three main questions: the energy deposition mechanism at the poles (where the fast wind is originated), the source of the slow wind at lower altitude, and how the global corona evolves, in particular in relation to the huge plasma ejections that occasionally are produced. To obtain the required optical performance, not only the Metis optical design has been highly optimized, but the alignment procedure has also been subjected to an accurate evaluation in order to fulfill the integration specifications. The telescope assembling sequence has been constructed considering all the subsystems manufacturing, alignment and integration tolerances. The performance verification activity is an important milestone in the instrument characterization and the obtained results will assure the fulfillment of the science requirements for its operation in space. The entire alignment and verification phase has been performed by the Metis team in collaboration with Thales Alenia Space Torino and took place in ALTEC (Turin) at the Optical Payload System Facility using the Space Optics Calibration Chamber infrastructure, a vacuum chamber especially built and tested for the alignment and calibration of the Metis coronagraph, and suitable for tests of future payloads. The goal of the alignment, integration, verification and calibration processes is to measure the parameters of the telescope, and the characteristics of the two Metis channels: visible and ultraviolet. They work in parallel thanks to the peculiar optical layout. The focusing and alignment performance of the two channels must be well understood, and the results need to be easily compared to the requirements. For this, a dedicated illumination method, with both channels fed by the same source, has been developed; and a procedure to perform a simultaneous through focus analysis has been adopted. In this paper the final optical performance achieved by Metis is reported and commented. Title: Stray light calibration for the Solar Orbiter/Metis solar coronagraph Authors: Landini, F.; Romoli, M.; Fineschi, S.; Casini, C.; Baccani, C.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.; Castronuovo, M.; Casti, M.; Capobianco, G.; Massone, G.; Susino, R.; Da Deppo, V.; Frassetto, F.; Pancrazzi, M.; Teriaca, L.; Schuehle, U.; Heerlein, K.; Uslenghi, M. Bibcode: 2019SPIE11180E..2IL Altcode: The Solar Orbiter/Metis visible and UV solar coronagraph redefines the concept of external occultation in solar coronagraphy. Classical externally occulted coronagraphs are characterized by an occulter in front of the telescope entrance aperture. Solar Orbiter will approach the Sun down to 0.28 AU: in order to reduce the thermal load, the Metis design switches the positions of the entrance aperture and the external occulter thus achieving what is called the inverted external occultation. The inverted external occulter (IEO) consists of a circular aperture on the Solar Orbiter thermal shield that acts as coronagraph entrance pupil. A spherical mirror, located 800 mm behind the IEO, back rejects the disklight through the IEO itself. To pursue the goal of maximizing the reduction of the stray light level on the focal plane, an optimization of the IEO shape was implemented. The stray light calibration was performed in a clean environment in front of the OPSys solar disk divergence simulator (at ALTEC, in Torino, Italy), which is able to emulate different heliocentric distances. Ground calibrations were a unique opportunity to map the Metis stray light level thanks to a pure solar disk simulator without the solar corona. The stray light calibration was limited to the visible light case, being the most stringent. This work is focused on the description of the laboratory facility that was used to perform the stray light calibration and on the calibration results. Title: The EUI instrument onboard Solar Orbiter: the EUV corona imaged differently Authors: Berghmans, David; Rochus, Pierre; Auchère, Frédéric; Harra, Louise; Schmutz, Werner; Schühle, Udo Bibcode: 2018csc..confE..73B Altcode: The ESA Solar Orbiter mission is designed to determine how the Sun creates and controls the heliosphere. The spacecraft will bring a combination of in situ and remote sensing instruments out of the ecliptic (>30°) and close to the sun (0.3 solar-radii). The launch of Solar Orbiter is expected (not earlier than) Feb 2019. The Extreme Ultraviolet Imager is part of the remote-sensing package of Solar Orbiter, to be operating during 3 ten-day periods of each orbit around the Sun, which last roughly half a year. These 3 periods will correspond to perihelion and maximal solar latitude north and south. The Extreme Ultraviolet Imager is itself a suite of three UV and EUV telescopes that observe the solar atmosphere both globally as well as at very high resolution. The two high-resolution imagers (HRIs) will image the solar atmosphere in the chromospheric Lyman alpha line and the coronal 17nm pass band with a resolution of 0.5 arcsec. From perihelion, this will correspond to a pixel footprint on the solar disc of (110km)^2 . The Full Sun Imager (FSI), working at the 17.4 nm and 30.4 nm EUV passbands, will provide a global view of the solar atmosphere and is therefore an essential building block for the "connection science" of the Solar Orbiter mission. The FSI field of view is large enough (228arcmin) that, even at perihelion and at maximal off-points by Solar Orbiter, the full solar disk remains in the field of view. This large FOV and the FSI's high sensitivity will allow to image the "transition corona" where the topology of streamers and pseudo-streamers fades in the solar wind. Furthermore, FSI will be the first to image all this from out of the ecliptic. In this talk we will give an overview of the EUI instrument. We will focus on the novel aspects of EUI that will allow it to image beyond what previous EUV imagers could show us: EUV imaging from the highest solar latitude, with the widest field-of-view and at highest spatial resolution. Title: Broadband EUV/FUV mirror coatings for a solar spectrograph mission Authors: Teriaca, Luca; Feigl, Torsten; Schühle, Udo Bibcode: 2018SPIE10699E..2YT Altcode: As it is rich in spectral lines emitted by plasma between 10000 K and 20 MK, the vacuum ultraviolet (VUV - 17 to 200 nm) solar spectrum is extremely valuable for instruments that study the physics of the solar atmosphere. We present multilayer coatings with simultaneous broadband reflectance in the two spectral ranges of 16.9 nm to 21.5 nm and 46.3 nm to 127.5 nm. The coatings are based on Mo/Si multilayers with a thin capping layer of boron carbide (B4C). Samples were produced and their reflectance measured. Their performance in terms of resistance to high temperatures and low micro-roughness was also assessed by measurement. Our study shows that a coating with the characteristics required by next generation spectrometers for studies of the solar atmosphere is feasible. Title: The solar orbiter Metis and EUI intensified CMOS-APS detectors: concept, main characteristics, and performance Authors: Schühle, Udo; Teriaca, Luca; Aznar Cuadrado, Regina; Heerlein, Klaus; Uslenghi, Michela; Werner, Stephan Bibcode: 2018SPIE10699E..34S Altcode: Two instruments aboard the Solar Orbiter mission, the Extreme Ultraviolet Imager and the Metis coronagraph, are using cameras of similar design to obtain images in the Lyman alpha line of hydrogen at 121.6 nm. Each of these cameras is based on an APS sensor used as readout of a single microchannel plate intensifier unit whose output current is converted into visible light photons through a phosphor screen. Before integration on the respective instruments, both detector's flight models have been characterized and calibrated. In this paper, we describe the two camera systems, the results of qualification tests, and report their performance characteristics. Title: The EUI flight instrument of Solar Orbiter: from optical alignment to end-to-end calibration Authors: Halain, J. -P.; Renotte, E.; Auchère, F.; Berghmans, D.; Delmotte, F.; Harra, L.; Schmutz, W.; Schühle, U.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Barbay, J.; Giordanengo, B.; Gissot, S.; Gottwald, A.; Heerlein, K.; Hellin, M. -L.; Hermans, A.; Hervier, V.; Jacques, L.; Laubis, C.; Mazzoli, A.; Meining, S.; Mercier, R.; Philippon, A.; Roose, S.; Rossi, L.; Scholze, F.; Smith, P.; Teriaca, L.; Zhang, X.; Rochus, P. Bibcode: 2018SPIE10699E..0HH Altcode: The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter mission will image the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral ranges. The development of the EUI instrument has been successfully completed with the optical alignment of its three channels' telescope, the thermal and mechanical environmental verification, the electrical and software validations, and an end-toend on-ground calibration of the two-units' flight instrument at the operating wavelengths. The instrument has been delivered and installed on the Solar Orbiter spacecraft, which is now undergoing all preparatory activities before launch. Title: In-flight performance of the solar UV radiometer LYRA/PROBA-2 Authors: Stockman, Y.; BenMoussa, A.; Dammasch, I.; Defise, J. -M.; Dominique, M.; Halain, J. -P.; Hochedez, J. -F.; Koller, S.; Schmutz, W.; Schühle, U. Bibcode: 2017SPIE10565E..0AS Altcode: LYRA is a solar radiometer, part of the PROBA-2 micro-satellite payload (Fig. 1). The PROBA-2 [1] mission has been launched on 02 November 2009 with a Rockot launcher to a Sun-synchronous orbit at an altitude of 725 km. Its nominal operation duration is two years with possible extension of 2 years. PROBA-2 is a small satellite developed under an ESA General Support Technology Program (GSTP) contract to perform an in-flight demonstration of new space technologies and support a scientific mission for a set of selected instruments [2]. PROBA-2 host 17 technological demonstrators and 4 scientific instruments. The mission is tracked by the ESA Redu Mission Operation Center. One of the four scientific instruments is LYRA that monitors the solar irradiance at a high cadence (> 20 Hz) in four soft X-Ray to VUV large passbands: the "Lyman-Alpha" channel, the "Herzberg" continuum range, the "Aluminium" and "Zirconium" filter channels. The radiometric calibration is traceable to synchrotron source standards [3]. LYRA benefits from wide bandgap detectors based on diamond. It is the first space assessment of these revolutionary UV detectors for astrophysics. Diamond sensors make the instruments radiation-hard and solar-blind (insensitive to the strong solar visible light) and, therefore, visible light blocking filters become superfluous. To correlate the data of this new detector technology, silicon detectors with well known characteristics are also embarked. Due to the strict allocated mass and power budget (5 kg, 5W), and poor priority to the payload needs on such platform, an optimization and a robustness of the instrument was necessary. The first switch-on occured on 16 November 2009. Since then the instrument performances have been monitored and analyzed during the commissioning period. This paper presents the first-light and preliminary performance analysis. Title: LYRA, solar uv radiometer on the technology demonstration platform PROBA-2 Authors: Stockman, Y.; Hochedez, J. -F.; Schmutz, W.; BenMoussa, A.; Defise, J. -M.; Denis, F.; D'Olieslaeger, M.; Dominique, M.; Haenen, K.; Halain, J. -P.; Koller, S.; Koizumi, S.; Mortet, V.; Rochus, P.; Schühle, U.; Soltani, A.; Theissen, A. Bibcode: 2017SPIE10567E..3KS Altcode: LYRA is a solar radiometer part of the PROBA 2 micro satellite payload. LYRA will monitor the solar irradiance in four soft X-Ray - VUV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and SpaceWeather: 1/ Lyman Alpha channel, 2/ Herzberg continuum range, 3/ Aluminium filter channel (including He II at 30.4 nm) and 4/ Zirconium filter channel. The radiometric calibration is traceable to synchrotron source standards. The stability will be monitored by on-board calibration sources (LEDs), which allow us to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of revolutionary UV detectors. Diamond sensors make the instruments radiation-hard and solar-blind (insensitive to visible light) and therefore, make dispensable visible light blocking filters. To correlate the data of this new detector technology, well known technology, such as Si detectors are also embarked. The SWAP EUV imaging telescope will operate next to LYRA on PROBA-2. Together, they will provide a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter. Title: Characterization of the UV detector of Solar Orbiter/Metis Authors: Uslenghi, Michela; Schühle, Udo H.; Teriaca, Luca; Heerlein, Klaus; Werner, Stephan Bibcode: 2017SPIE10397E..1KU Altcode: Metis, one of the instruments of the ESA mission Solar Orbiter (to be launched in February 2019), is a coronograph able to perform broadband polarization imaging in the visible range (580-640 nm), and narrow band imaging in UV (HI Lyman-α 121.6 nm) . The detector of the UV channel is an intensified camera, based on a Star-1000 rad-hard CMOS APS coupled via a 2:1 fiber optic taper to a single stage Microchannel Plate intensifier, sealed with an entrance MgF2 window and provided with an opaque KBr photocathode. Before integration in the instrument, the UVDA (UV Detector Assembly) Flight Model has been characterized at the MPS laboratory and calibrated in the UV range using the detector calibration beamline of the Metrology Light Source synchrotron of the Physikalisch-Technische Bundesanstalt (PTB). Linearity, spectral calibration, and response uniformity at 121.6 nm have been measured. Preliminary results are reported in this paper. Title: The VUV instrument SPICE for Solar Orbiter: performance ground testing Authors: Caldwell, Martin E.; Morris, Nigel; Griffin, Douglas K.; Eccleston, Paul; Anderson, Mark; Pastor Santos, Carmen; Bruzzi, Davide; Tustain, Samuel; Howe, Chris; Davenne, Jenny; Grundy, Timothy; Speight, Roisin; Sidher, Sunil D.; Giunta, Alessandra; Fludra, Andrzej; Philippon, Anne; Auchere, Frederic; Hassler, Don; Davila, Joseph M.; Thompson, William T.; Schuehle, Udo H.; Meining, Stefan; Walls, Buddy; Phelan, P.; Dunn, Greg; Klein, Roman M.; Reichel, Thomas; Gyo, Manfred; Munro, Grant J.; Holmes, William; Doyle, Peter Bibcode: 2017SPIE10397E..08C Altcode: SPICE is an imaging spectrometer operating at vacuum ultraviolet (VUV) wavelengths, 70.4 - 79.0 nm and 97.3 - 104.9 nm. It is a facility instrument on the Solar Orbiter mission, which carries 10 science instruments in all, to make observations of the Sun's atmosphere and heliosphere, at close proximity to the Sun, i.e to 0.28 A.U. at perihelion. SPICE's role is to make VUV measurements of plasma in the solar atmosphere. SPICE is designed to achieve spectral imaging at spectral resolution >1500, spatial resolution of several arcsec, and two-dimensional FOV of 11 x16arcmins. The many strong constraints on the instrument design imposed by the mission requirements prevent the imaging performance from exceeding those of previous instruments, but by being closer to the sun there is a gain in spatial resolution. The price which is paid is the harsher environment, particularly thermal. This leads to some novel features in the design, which needed to be proven by ground test programs. These include a dichroic solar-transmitting primary mirror to dump the solar heat, a high in-flight temperature (60deg.C) and gradients in the optics box, and a bespoke variable-line-spacing grating to minimise the number of reflective components used. The tests culminate in the systemlevel test of VUV imaging performance and pointing stability. We will describe how our dedicated facility with heritage from previous solar instruments, is used to make these tests, and show the results, firstly on the Engineering Model of the optics unit, and more recently on the Flight Model. For the keywords, select up to 8 key terms for a search on your manuscript's subject. Title: The qualification campaign of the EUI instrument of Solar Orbiter Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques, L.; Mazzoli, A.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Smith, P. Bibcode: 2016SPIE.9905E..2XH Altcode: The Extreme Ultraviolet Imager (EUI) instrument is one of the ten scientific instruments on board the Solar Orbiter mission to be launched in October 2018. It will provide full-sun and high-resolution images of the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). The validation of the EUI instrument design has been completed with the Assembly, Integration and Test (AIT) of the instrument two-units Qualification Model (QM). Optical, electrical, electro-magnetic compatibility, thermal and mechanical environmental verifications were conducted and are summarized here. The integration and test procedures for the Flight Model (FM) instrument and sub-systems were also verified. Following the Qualification Review, the flight instrument activities were started with the assembly of the flight units. The mechanical and thermal acceptance tests and an end-to-end final calibration in the (E)UV will then be conducted before delivery for integration on the Solar Orbiter Spacecraft by end of 2016. Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun to the Heliosphere Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta, Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo Bibcode: 2016cosp...41E.607F Altcode: The SPICE (Spectral Imaging of the Coronal Environment) instrument is one of the key remote sensing instruments onboard the upcoming Solar Orbiter Mission. SPICE has been designed to contribute to the science goals of the mission by investigating the source regions of outflows and ejection processes which link the solar surface and corona to the heliosphere. In particular, SPICE will provide quantitative information on the physical state and composition of the solar atmosphere plasma. For example, SPICE will access relative abundances of ions to study the origin and the spatial/temporal variations of the 'First Ionization Potential effect', which are key signatures to trace the solar wind and plasma ejections paths within the heliosphere. Here we will present the instrument and its performance capability to attain the scientific requirements. We will also discuss how different observation modes can be chosen to obtain the best science results during the different orbits of the mission. To maximize the scientific return of the instrument, the SPICE team is working to optimize the instrument operations, and to facilitate the data access and their exploitation. Title: Solar abundances with the SPICE spectral imager on Solar Orbiter Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin, Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany Bibcode: 2016cosp...41E.681G Altcode: Elemental composition of the solar atmosphere and in particular abundance bias of low and high First Ionization Potential (FIP) elements are a key tracer of the source regions of the solar wind. These abundances and their spatio-temporal variations, as well as the other plasma parameters , will be derived by the SPICE (Spectral Imaging of the Coronal Environment) EUV spectral imager on the upcoming Solar Orbiter mission. SPICE is designed to provide spectroheliograms (spectral images) using a core set of emission lines arising from ions of both low-FIP and high-FIP elements. These lines are formed over a wide range of temperatures, enabling the analysis of the different layers of the solar atmosphere. SPICE will use these spectroheliograms to produce dynamic composition maps of the solar atmosphere to be compared to in-situ measurements of the solar wind composition of the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to study the connectivity between the spacecraft (the Heliosphere) and the Sun. We will discuss the SPICE capabilities for such composition measurements. Title: Hydrogen Ly-α and Ly-β full Sun line profiles observed with SUMER/SOHO (1996-2009) Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2015A&A...581A..26L Altcode: Context. Accurate hydrogen spectra emitted by the entire solar disc in the Ly-α and Ly-βlines are valuable for deriving the distribution and the behaviour of atomic hydrogen in the heliosphere, for understanding the UV emissions of solar type stars better, and finally for estimating the solar energy input that mainly initiates the chemical processes occurring in the planetary and cometary outer atmospheres.
Aims: In this paper we want to accurately determine the irradiance solar spectral profiles of Ly-α and Ly-β and their evolution through the solar activity cycle 23.
Methods: The SUMER/SOHO spectrometer is a slit spectrometer that is only able to analyse a small part of the solar image. Consequently, we used the scattered light properties of the telescope to obtain average spectra over the solar disc. Then the profile is calibrated using the SOLSTICE/UARS and TIMED/SEE irradiance spectra.
Results: We obtained a set of irradiance Ly-α and Ly-β solar spectra with a 0.002 nm resolution through the solar activity cycle 23. In each line a relation between the integrated profile and the line centre intensity was obtained.Knowing the line irradiance, it is possible to deduce the central line profile intensity, a critical input into the interplanetary and planetary oxygen and hydrogen fluorescent processes.
Conclusions: The observation of H i Ly-α and Ly-β line profiles by SUMER/SOHO during the cycle 23 allows analysis of the evolution of their characteristics and accurate determination of UV radiation input into the solar system.

Profiles 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/581/A26 Title: The extreme ultraviolet imager of solar orbiter: optical design and alignment scheme Authors: Halain, J. -P.; Mazzoli, A.; Meining, S.; Rochus, P.; Renotte, E.; Auchère, F.; Schühle, U.; Delmotte, F.; Dumesnil, C.; Philippon, A.; Mercier, R.; Hermans, A. Bibcode: 2015SPIE.9604E..0HH Altcode: The Extreme Ultraviolet Imager (EUI) is one of the remote sensing instruments on-board the Solar Orbiter mission. It will provide dual-band full-Sun images of the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm), and high resolution images of the solar disk in both extreme ultraviolet (17.1 nm) and vacuum ultraviolet (Lyman-alpha 121.6 nm). The EUI optical design takes heritage of previous similar instruments. The Full Sun Imager (FSI) channel is a single mirror Herschel design telescope. The two High Resolution Imager (HRI) channels are based on a two-mirror optical refractive scheme, one Ritchey-Chretien and one Gregory optical design for the EUV and the Lyman-alpha channels, respectively. The spectral performances of the EUI channels are obtained thanks to dedicated mirror multilayer coatings and specific band-pass filters. The FSI channel uses a dual-band mirror coating combined with aluminum and zirconium band-pass filters. The HRI channels use optimized band-pass selection mirror coatings combined with aluminum band-pass filters and narrow band interference filters for Lyman-alpha. The optical performances result from accurate mirror manufacturing tolerances and from a two-step alignment procedure. The primary mirrors are first co-aligned. The HRI secondary mirrors and focal planes positions are then adjusted to have an optimum interferometric cavity in each of these two channels. For that purpose a dedicated alignment test setup has been prepared, composed of a dummy focal plane assembly representing the detector position. Before the alignment on the flight optical bench, the overall alignment method has been validated on the Structural and Thermal Model, on a dummy bench using flight spare optics, then on the Qualification Model to be used for the system verification test and qualifications. Title: The extreme UV imager telescope on-board the Solar Orbiter mission: overview of phase C and D Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques, L.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Smith, P.; Tandy, J.; Mercier, R.; Verbeeck, C. Bibcode: 2015SPIE.9604E..0GH Altcode: The Solar Orbiter mission is composed of ten scientific instruments dedicated to the observation of the Sun's atmosphere and its heliosphere, taking advantage of an out-of ecliptic orbit and at perihelion reaching a proximity close to 0.28 A.U. On board Solar Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun image sequences of the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm), and high-resolution image sequences of the solar disk in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet (121.6 nm). The EUI concept uses heritage from previous similar extreme ultraviolet instrument. Additional constraints from the specific orbit (thermal and radiation environment, limited telemetry download) however required dedicated technologies to achieve the scientific objectives of the mission. The development phase C of the instrument and its sub-systems has been successfully completed, including thermomechanical and electrical design validations with the Structural Thermal Model (STM) and the Engineering Model (EM). The instrument STM and EM units have been integrated on the respective spacecraft models and will undergo the system level tests. In parallel, the Phase D has been started with the sub-system qualifications and the flight parts manufacturing. The next steps of the EUI development will be the instrument Qualification Model (QM) integration and qualification tests. The Flight Model (FM) instrument activities will then follow with the acceptance tests and calibration campaigns. Title: VizieR Online Data Catalog: Sun hydrogen Lyman irradiance lines profiles (Lemaire+, 2015) Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schuhle, U.; Wilhelm, K. Bibcode: 2015yCat..35810026L Altcode: Set of irradiance Ly-α and Ly-β solar spectra with a 0.002nm resolution through the solar activity cycle 23. The wavelength distance from line center is given every 0.001nm.

(2 data files). Title: Degradation assessment of LYRA after 5 years on orbit - Technology Demonstration - Authors: BenMoussa, A.; Giordanengo, B.; Gissot, S.; Dammasch, I. E.; Dominique, M.; Hochedez, J. -F.; Soltani, A.; Bourzgui, N.; Saito, T.; Schühle, U.; Gottwald, A.; Kroth, U.; Jones, A. R. Bibcode: 2015ExA....39...29B Altcode: 2015ExA...tmp....1B We present a long-term assessment of the radiometric calibration and degradation of the Large Yield Radiometer (LYRA), which has been on orbit since 2009. LYRA is an ultraviolet (UV) solar radiometer and is the first space experiment using aboard a pioneering diamond detector technology. We show that LYRA has degraded after the commissioning phase but is still exploitable scientifically after almost 5 years on orbit thanks to its redundancy design and calibration strategy correcting for instrument degradation. We focus on the inflight detector's calibration and show that diamond photodetectors have not degraded while silicon reference photodiodes that are even less exposed to the Sun show an increase of their dark current and a decrease of their photoresponse. Title: The extreme UV imager of solar orbiter: from detailed design to flight model Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Mercier, R.; Verbeeck, F.; Thome, M.; Heerlein, K.; Hermans, A.; Jacques, L.; Mazzoli, A.; Meining, S.; Rossi, L.; Tandy, J.; Smith, P.; Winter, B. Bibcode: 2014SPIE.9144E..08H Altcode: The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission will provide full-sun and high-resolution image sequences of the solar atmosphere at selected spectral emission lines in the extreme and vacuum ultraviolet. After the breadboarding and prototyping activities that focused on key technologies, the EUI project has completed the design phase and has started the final manufacturing of the instrument and its validation. The EUI instrument has successfully passed its Critical Design Review (CDR). The process validated the detailed design of the Optical Bench unit and of its sub-units (entrance baffles, doors, mirrors, camera, and filter wheel mechanisms), and of the Electronic Box unit. In the same timeframe, the Structural and Thermal Model (STM) test campaign of the two units have been achieved, and allowed to correlate the associated mathematical models. The lessons learned from STM and the detailed design served as input to release the manufacturing of the Qualification Model (QM) and of the Flight Model (FM). The QM will serve to qualify the instrument units and sub-units, in advance of the FM acceptance tests and final on-ground calibration. Title: Scattered Lyman-α radiation of comet 2012/S1 (ISON) observed by SUMER/SOHO Authors: Curdt, W.; Boehnhardt, H.; Vincent, J. -B.; Solanki, S. K.; Schühle, U.; Teriaca, L. Bibcode: 2014A&A...567L...1C Altcode: 2014arXiv1406.4343C During its sungrazing perihelion passage, comet ISON appeared in the field of view of the SUMER spectrometer and allowed unique observations at far-ultraviolet wavelengths with high spatial and temporal resolution. We report results of these observations completed on November 28, 2013, when the comet was only 2.82 Rʘ away from the Sun. Our data show the arrow-shaped dust tail in Ly-α emission trailing behind the predicted position of the nucleus, but offset from the trajectory. We interpret the emission as sunlight that is scattered at μm-sized dust particles. We modeled the dust emission and dynamics to reproduce the appearance of the tail. We were unable to detect any signature of cometary gas or plasma around the expected position of the nucleus and conclude that the outgassing processes must have stopped before the observation started. Moreover, the model we used to reproduce the observed dust tail needs a sharp fall-off of the dust production hours before perihelion transit. We compare the radiances of the disk and the dust tail for an estimate of the dust column density and tail mass. Title: Scattered Lyman-alpha radiation of comet 2012/S1 (ISON) observed by SUMER/SOHO Authors: Curdt, W.; Boehnhardt, H.; Germerott, D.; Schuehle, U.; Solanki, S.; Teriaca, L.; Vincent, J. Bibcode: 2014acm..conf..119C Altcode: During its recent perihelion passage, comet ISON came so close to the Sun that it appeared in the field of view (FOV) of the SUMER spectrometer on SOHO and allowed unique observations at far-UV wavelengths with high spatial and temporal resolution. We report results of these observations completed during the comet's encounter with the Sun on November 28.75, 2013. Our data show the dust tail trailing behind the predicted position of the nucleus seen in Lyman-alpha emission as light from the solar disk that is scattered by micron-sized dust particles. The arrow-shaped tail is offset from the trajectory and not aligned with it. We model the dust emission and dynamics to reproduce the appearance of the tail. We could not detect any signature of cometary gas or plasma around the expected position of the nucleus and conclude that the out-gassing processes must have stopped before the comet entered our FOV. Also the model we used to reproduce the observed dust tail needs a sharp fall-off of the dust production hours before perihelion. We compare the radiance of the dust tail to the Lyman-alpha emission of the disk for an estimate of the dust column density. After observing 18 years mostly solar targets, this was the first time that SUMER completed spectroscopic observations of a comet. Title: The SUMER Data in the SOHO Archive Authors: Curdt, W.; Germerott, D.; Wilhelm, K.; Schühle, U.; Teriaca, L.; Innes, D.; Bocchialini, K.; Lemaire, P. Bibcode: 2014SoPh..289.2345C Altcode: 2013arXiv1309.1314C We have released an archive of all observational data of the VUV spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on SOHO that have been acquired until now. The operational phase started with `first light' observations on 27 January 1996 and will end in 2014. Future data will be added to the archive when they become available. The archive consists of a set of raw data (Level 0) and a set of data that are processed and calibrated to the best knowledge we have today (Level 1). This communication describes step by step the data acquisition and processing that has been applied in an automated manner to build the archive. It summarizes the expertise and insights into the scientific use of SUMER spectra that has accumulated over the years. It also indicates possibilities for further enhancement of the data quality. With this article we intend to convey our own understanding of the instrument performance to the scientific community and to introduce the new, standard FITS-format database. Title: On-Orbit Degradation of Solar Instruments Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.; Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.; Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah, M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley, L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.; Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo, B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge, D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.; Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N. Bibcode: 2013SoPh..288..389B Altcode: 2013arXiv1304.5488B We present the lessons learned about the degradation observed in several space solar missions, based on contributions at the Workshop about On-Orbit Degradation of Solar and Space Weather Instruments that took place at the Solar Terrestrial Centre of Excellence (Royal Observatory of Belgium) in Brussels on 3 May 2012. The aim of this workshop was to open discussions related to the degradation observed in Sun-observing instruments exposed to the effects of the space environment. This article summarizes the various lessons learned and offers recommendations to reduce or correct expected degradation with the goal of increasing the useful lifespan of future and ongoing space missions. Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher, P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy, E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.; Zender, J. Bibcode: 2013SoPh..286...43S Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm and provides images of the low solar corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weather-relevant events and features in the low solar corona. Given the limited resources of the PROBA2 microsatellite, the SWAP telescope is designed with various innovative technologies, including an off-axis optical design and a CMOS-APS detector. This article provides reference documentation for users of the SWAP image data. Title: Status of RAISE, the Rapid Acquisition Imaging Spectrograph Experiment Authors: Laurent, Glenn T.; Hassler, D. M.; DeForest, C.; Ayres, T. R.; Davis, M.; De Pontieu, B.; Schuehle, U.; Warren, H. Bibcode: 2013SPD....44..145L Altcode: The Rapid Acquisition Imaging Spectrograph Experiment (RAISE) sounding rocket payload is a high speed scanning-slit imaging spectrograph designed to observe the dynamics and heating of the solar chromosphere and corona on time scales as short as 100 ms, with 1 arcsec spatial resolution and a velocity sensitivity of 1-2 km/s. The instrument is based on a new class of UV/EUV imaging spectrometers that use only two reflections to provide quasi-stigmatic performance simultaneously over multiple wavelengths and spatial fields. The design uses an off-axis parabolic telescope mirror to form a real image of the sun on the spectrometer entrance aperture. A slit then selects a portion of the solar image, passing its light onto a near-normal incidence toroidal grating, which re-images the spectrally dispersed radiation onto two array detectors. Two full spectral passbands over the same one-dimensional spatial field are recorded simultaneously with no scanning of the detectors or grating. The two different spectral bands (1st-order 1205-1243Å and 1526-1564Å) are imaged onto two intensified Active Pixel Sensor (APS) detectors whose focal planes are individually adjusted for optimized performance. The telescope and grating are coated with B4C to enhance short wavelength (2nd order) reflectance, enabling the instrument to record the brightest lines between 602-622Å and 761-780Å at the same time. RAISE reads out the full field of both detectors at 5-10 Hz, allowing us to record over 1,500 complete spectral observations in a single 5-minute rocket flight, opening up a new domain of high time resolution spectral imaging and spectroscopy. We present an overview of the project, a summary of the maiden flight results, and an update on instrument status.Abstract (2,250 Maximum Characters): The Rapid Acquisition Imaging Spectrograph Experiment (RAISE) sounding rocket payload is a high speed scanning-slit imaging spectrograph designed to observe the dynamics and heating of the solar chromosphere and corona on time scales as short as 100 ms, with 1 arcsec spatial resolution and a velocity sensitivity of 1-2 km/s. The instrument is based on a new class of UV/EUV imaging spectrometers that use only two reflections to provide quasi-stigmatic performance simultaneously over multiple wavelengths and spatial fields. The design uses an off-axis parabolic telescope mirror to form a real image of the sun on the spectrometer entrance aperture. A slit then selects a portion of the solar image, passing its light onto a near-normal incidence toroidal grating, which re-images the spectrally dispersed radiation onto two array detectors. Two full spectral passbands over the same one-dimensional spatial field are recorded simultaneously with no scanning of the detectors or grating. The two different spectral bands (1st-order 1205-1243Å and 1526-1564Å) are imaged onto two intensified Active Pixel Sensor (APS) detectors whose focal planes are individually adjusted for optimized performance. The telescope and grating are coated with B4C to enhance short wavelength (2nd order) reflectance, enabling the instrument to record the brightest lines between 602-622Å and 761-780Å at the same time. RAISE reads out the full field of both detectors at 5-10 Hz, allowing us to record over 1,500 complete spectral observations in a single 5-minute rocket flight, opening up a new domain of high time resolution spectral imaging and spectroscopy. We present an overview of the project, a summary of the maiden flight results, and an update on instrument status. Title: LEMUR: Large European module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric; Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len; Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green, Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem, Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet, Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto, Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu, Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele; Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas; Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann, Thomas; Winter, Berend; Young, Peter Bibcode: 2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T The solar outer atmosphere is an extremely dynamic environment characterized by the continuous interplay between the plasma and the magnetic field that generates and permeates it. Such interactions play a fundamental role in hugely diverse astrophysical systems, but occur at scales that cannot be studied outside the solar system. Understanding this complex system requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1'' and 0.3''), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with 0.14'' per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km s - 1 or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission. 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: A prototype of the UV detector for METIS on Solar Orbiter Authors: Uslenghi, M.; Incorvaia, S.; Fiorini, M.; Schühle, U. H.; Teriaca, L.; Wilkinson, E.; Siegmund, O. H.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolini, G.; Nicolosi, G.; Romoli, M.; Focardi, M. Bibcode: 2012SPIE.8443E..3IU Altcode: METIS (Multi Element Telescope for Imaging and Spectroscopy) is one of the instruments included in the science payload of the ESA mission Solar Orbiter: a coronograph able to perform broadband polarization imaging in the visible range, and narrow band imaging in UV (HI Lyman-α) and EUV (HeII Lyman-α). In addition, it will acquire spectra of the solar corona simultaneously to UV/EUV imaging. It will be equipped with two detectors: a hybrid APS dedicated to the visible channel and an Intensified APS for the UV/EUV channel. The spectroscopic channel will share the same detector as the UV/EUV corona imaging, with the spectrum imaged on a portion of the detector not used by the corona image. We present the development of the UV/EUV detector consisting of a CMOS APS imaging device to be coupled with a microchannel plate intensifier. Other than constraints related to the harsh environment (radiation, temperature, visible stray-light), the METIS UV detector has the additional challenge of managing different count rates associated with the three different kind of measurements (UV imaging, EUV imaging and spectroscopy). The required dynamic range is further extended since observations will be planned at different distances from the Sun, varying image scale over a fixed vignetting function. We will present the architecture of this UV detector, describing the prototype developed in order to optimize the performance on the overall dynamic range required by METIS. Title: METIS: a novel coronagraph design for the Solar Orbiter mission Authors: Fineschi, Silvano; Antonucci, Ester; Naletto, Giampiero; Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro; Berlicki, Arkadiusz; Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi, Mauro; Landini, Federico; Massone, Giuseppe; Malvezzi, Marco A.; Moses, J. Dan; Nicolosi, Piergiorgio; Pancrazzi, Maurizio; Pelizzo, Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.; Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela Bibcode: 2012SPIE.8443E..3HF Altcode: METIS (Multi Element Telescope for Imaging and Spectroscopy) 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 mission profile will bring the Solar Orbiter spacecraft as close to the Sun as 0.3 A.U., and up to 35° out-of-ecliptic providing a unique platform for helio-synchronous observations of the Sun and its polar regions. METIS coronagraph is designed for multi-wavelength imaging and spectroscopy of the solar corona. This presentation gives an overview of the innovative design elements of the METIS coronagraph. These elements include: i) multi-wavelength, reflecting Gregorian-telescope; ii) multilayer coating optimized for the extreme UV (30.4 nm, HeII Lyman-α) with a reflecting cap-layer for the UV (121.6 nm, HI Lyman-α) and visible-light (590-650); iii) inverse external-occulter scheme for reduced thermal load at spacecraft peri-helion; iv) EUV/UV spectrograph using the telescope primary mirror to feed a 1st and 4th-order spherical varied line-spaced (SVLS) grating placed on a section of the secondary mirror; v) liquid crystals electro-optic polarimeter for observations of the visible-light K-corona. The expected performances are also presented. Title: The EUI instrument on board the Solar Orbiter mission: from breadboard and prototypes to instrument model validation Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.; Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.; Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P. Bibcode: 2012SPIE.8443E..07H Altcode: The Solar Orbiter mission will explore the connection between the Sun and its heliosphere, taking advantage of an orbit approaching the Sun at 0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI) will provide full-sun and high-resolution image sequences of the solar atmosphere at selected spectral emission lines in the extreme and vacuum ultraviolet. To achieve the required scientific performances under the challenging constraints of the Solar Orbiter mission it was required to further develop existing technologies. As part of this development, and of its maturation of technology readiness, a set of breadboard and prototypes of critical subsystems have thus been realized to improve the overall instrument design. The EUI instrument architecture, its major components and sub-systems are described with their driving constraints and the expected performances based on the breadboard and prototype results. The instrument verification and qualification plan will also be discussed. We present the thermal and mechanical model validation, the instrument test campaign with the structural-thermal model (STM), followed by the other instrument models in advance of the flight instrument manufacturing and AIT campaign. Title: CMOS sensor and camera for the PHI instrument on board Solar Orbiter: evaluation of the radiation tolerance Authors: Piqueras, J.; Heerlein, K.; Werner, S.; Enge, R.; Schühle, U.; Woch, J.; De Ridder, T.; Meynants, G.; Wolfs, B.; Lepage, G.; Diels, W. Bibcode: 2012SPIE.8453E..14P Altcode: The ESA/NASA Solar Orbiter mission, to be launched in 2017, will explore the Sun at a much closer distance than any previous solar observatory. On board the spacecraft, a high-resolution magnetograph (PHI) will provide two-dimensional measurements of the photospheric vector magnetic field and line-of-sight velocity. The environmental conditions encountered during the mission, together with the stringent performance requirements of the instrument, define the set of specifications for the camera system. A custom designed CMOS sensor (with 2048×2050 pixels) has been developed to fulfill the aimed radiation hardness and performance. This sensor must demonstrate a cadence above 10 fps with a full-well capacity higher than 105 electrons in a 10-μm pixel pitch. We report the characterization and qualification tests. The radiation test campaign has been completed up to a TID of 150 krad(Si), proton fluence up to 4 × 1011 at 10 MeV and 2 × 1011 at 20 MeV, and with heavy ions to check for latch-up and SEFI failures. In parallel, a radiation tolerant camera electronic readout system has been built to control the sensor and readout images, digitize the data, and communicate with the data handling system of the PHI instrument. In addition, we present the main issues related to the camera design and future perspectives. Title: The solar hydrogen Lyman α to Lyman β line ratio Authors: Lemaire, P.; Vial, J. -C.; Curdt, W.; Schühle, U.; Woods, T. N. Bibcode: 2012A&A...542L..25L Altcode:
Aims: We investigate the variation in the solar hydrogen Lyman α (Lyα) to Lyman β (Lyβ) line ratio as a function of the solar activity by taking into account new results obtained by SoHO/SUMER and TIMED/SEE.
Methods: We reanalyze data of quiet and active regions previously collected with the LPSP multichannel instrument on OSO8. We then re-examine data obtained on the solar disk with SUMER and compare them with previous data. In a second step, we use the full Sun H i Lyβ profiles to determine the Lyβ contribution to the SEE profiles obtained with a 0.4 nm full width at half-maximum. The variation in the Lyα to Lyβ line ratio is then measured for part of the solar cycle 23 (2002-2008).
Results: We determine the radiance line ratio of the solar H i Lyα to Lyβ line for a quiet Sun area and the relation between the ratio of the Lyα to Lyβ irradiance and the Lyα solar irradiance. Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic field in the upper atmosphere of our closest star Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt, W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.; Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald, V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.; Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.; Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.; Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C. Bibcode: 2012ExA....33..271P Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations. Title: LEMUR (Large European Module for solar Ultraviolet Research): a VUV imaging spectrograph for the JAXA Solar-C Mission Authors: Korendyke, Clarence M.; Teriaca, Luca; Doschek, George A.; Harra, Louise K.; Schühle, Udo H.; Shimizu, Toshifumi Bibcode: 2011SPIE.8148E..0IK Altcode: 2011SPIE.8148E..17K LEMUR is a VUV imaging spectrograph with 0.28" resolution. Incident solar radiation is imaged onto the spectrograph slit by a single mirror telescope consisting of a 30-cm steerable f/12 off-axis paraboloid mirror. The spectrograph slit is imaged and dispersed by a highly corrected grating that focuses the solar spectrum over the detectors. The mirror is coated with a suitable multilayer with B4C top-coating providing a reflectance peak around 18.5 nm besides the usual B4C range above 500Å. The grating is formed by two halves, one optimized for performances around 185Å and the other above 500Å. Three intensified CCD cameras will record spectra above 50 nm while a large format CCD array with an aluminum filter will be used around 185Å. Title: The Lyman-alpha telescope of the extreme ultraviolet imager on Solar Orbiter Authors: Schühle, Udo; Halain, Jean-Philippe; Meining, Stefan; Teriaca, Luca Bibcode: 2011SPIE.8148E..0KS Altcode: 2011SPIE.8148E..19S On the Solar Orbiter mission, the Extreme Ultraviolet Imager (EUI) set of filtergraph-telescopes consists of two highresolution imagers (HRI) and one dual-band full Sun imager (FSI) that will provide images of the solar atmosphere in the extreme ultraviolet and in the Lyman-α line of hydrogen at 121.6 nm. The Lyman-α HRI, in particular, will provide imaging of the upper chromospheres/lower transition region of the Sun at unprecedented high cadence and at an angular resolution of 1" (corresponding to a spatial resolution of 200 km at perihelion). For vacuum-ultraviolet imaging of the Sun the main requirements for the instrumentation are high resolution, high cadence, and large dynamic range. We present here the novel solutions of the instrument design and show in detail the predicted performance of this telescope. We describe in detail how the high throughput and spectral purity at 121.6 nm is achieved. The technical solutions include multilayer coatings of the telescope mirrors for high reflectance at 121.6 nm, combined with interference filters and a multichannel-plate intensified CMOS active pixel camera. We make use of the design flexibilities of this camera to optimize the dynamic range in the focal plane. Title: The technical challenges of the Solar-Orbiter EUI instrument Authors: Halain, Jean-Philippe; Rochus, Pierre; Appourchaux, Thierry; Berghmans, David; Harra, Louise; Schühle, Udo; Auchère, Frédéric; Zhukov, Andrei; Renotte, Etienne; Defise, Jean-Marc; Rossi, Laurence; Fleury-Frenette, Karl; Jacques, Lionel; Hochedez, Jean-François; Ben Moussa, Ali Bibcode: 2010SPIE.7732E..0RH Altcode: 2010SPIE.7732E..20H The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter consists of a suite of two high-resolution imagers (HRI) and one dual-band full Sun imager (FSI) that will provide EUV and Lyman-α images of the solar atmospheric layers above the photosphere. The EUI instrument is based on a set of challenging new technologies allowing to reach the scientific objectives and to cope with the hard space environment of the Solar Orbiter mission. The mechanical concept of the EUI instrument is based on a common structure supporting the HRI and FSI channels, and a separated electronic box. A heat rejection baffle system is used to reduce the Sun heat load and provide a first protection level against the solar disk straylight. The spectral bands are selected by thin filters and multilayer mirror coatings. The detectors are 10μm pitch back illuminated CMOS Active Pixel Sensors (APS), best suited for the EUI science requirements and radiation hardness. This paper presents the EUI instrument concept and its major sub-systems. The current developments of the instrument technologies are also summarized. Title: First light of SWAP on-board PROBA2 Authors: Halain, Jean-Philippe; Berghmans, David; Defise, Jean-Marc; Renotte, Etienne; Thibert, Tanguy; Mazy, Emmanuel; Rochus, Pierre; Nicula, Bogdan; de Groof, Anik; Seaton, Dan; Schühle, Udo Bibcode: 2010SPIE.7732E..0PH Altcode: 2010SPIE.7732E..18H The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument launched on 2nd November 2009 on-board the ESA PROBA2 technological mission. SWAP is a space weather sentinel from a low Earth orbit, providing images at 174 nm of the solar corona. The instrument concept has been adapted to the PROBA2 mini-satellite requirements (compactness, low power electronics and a-thermal opto-mechanical system). It also takes advantage of the platform pointing agility, on-board processor, Packetwire interface and autonomous operations. The key component of SWAP is a radiation resistant CMOS-APS detector combined with onboard compression and data prioritization. SWAP has been developed and qualified at the Centre Spatial de Liège (CSL) and calibrated at the PTBBessy facility. After launch, SWAP has provided its first images on 14th November 2009 and started its nominal, scientific phase in February 2010, after 3 months of platform and payload commissioning. This paper summarizes the latest SWAP developments and qualifications, and presents the first light results. Title: The SUMER Ly-α line profile in quiescent prominences Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U. Bibcode: 2010A&A...511L...4C Altcode: 2010arXiv1002.1197C
Aims: As the result of a novel observing technique, we publish for the first time SoHO-SUMER observations of the true spectral line profile of hydrogen Lyman-α in quiescent prominences. Because SoHO is not in Earth orbit, our high-quality data set is free of geocoronal absorption. We studied the line profile to complement earlier observations of the higher Lyman lines and to substantiate recent model predictions.
Methods: We applied the reduced-aperture observing mode to two prominence targets and did a statistical analysis of the line profiles in both data sets. In particular, we investigated the shape of the profile, the radiance distribution, and the line shape-to-radiance interrelation. We also compared Ly-α data to co-temporal λ 1206 Si iii data.
Results: We find that the average profile of Ly-α has a blue-peak dominance and is reversed more if the line-of-sight is perpendicular to the field lines. The contrast of Ly-α prominence emission rasters is very low, and the radiance distribution differs from the log-normal distribution of the disk. Features in the Si iii line are not always co-spatial with Ly-α emission.
Conclusions: Our empirical results support recent multi-thread models, which predict that asymmetries and depths of the self-reversal depend on the orientation of the prominence axis relative to the line-of-sight. Title: Solar-blind UV detectors based on wide band gap semiconductors Authors: Schuhle, Udo; Hochedez, Jean-Francois Bibcode: 2010ISSIR...9..429S Altcode: Solid-state photon detectors based on semiconductors other than silicon are not yet considered mature technology but their current development opens new possibilities, also for space observations. Such devices are especially attractive for ultraviolet radiation detection, as semiconductor materials with band gaps larger than that of silicon can be produced and used as "visible-blind" or "solar-blind" detectors that are not affected by daylight. Here we evaluate the advantages of such detectors compared to silicon-based devices and report on the semiconductor detectors that have been fabricated in recent years with materials having large band-gap energies. We describe the most common pixel designs and characterize their general properties. Title: The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations Authors: Vourlidas, A.; Sanchez Andrade-Nuño, B.; Landi, E.; Patsourakos, S.; Teriaca, L.; Schühle, U.; Korendyke, C. M.; Nestoras, I. Bibcode: 2010SoPh..261...53V Altcode: 2009arXiv0912.2272V The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding rocket payload built to study the crucial interface between the solar chromosphere and the corona by observing the strongest line in the solar spectrum, the Ly α line at 1216 Å. In two flights, VAULT succeeded in obtaining the first ever subarcsecond ( 0.5\hbox{$^''$} ) images of this region with high sensitivity and cadence. Detailed analyses of those observations contributed significantly to new ideas about the nature of the transition region. Here, we present a broad overview of the Ly α atmosphere as revealed by the VAULT observations and bring together past results and new analyses from the second VAULT flight to create a synthesis of our current knowledge of the high-resolution Ly α Sun. We hope that this work will serve as a good reference for the design of upcoming Ly α telescopes and observing plans. Title: Intensified solid state sensor cameras: ICCD and IAPS Authors: Schuhle, Udo Bibcode: 2010ISSIR...9..419S Altcode: We describe the general design of intensified charge coupled devices and intensified active pixel sensors: cameras using microchannel plate intensifiers in combination with imaging arrays, like CCDs or CMOS-APS sensors. Several design options are compared and the capabilities and shortcomings of these devices will be highlighted and discussed. We describe, in particular, the properties of the intensifiers, phosphor anodes, and coupling schemes. The coupling between the intensifier and the image sensor is a special technological step that adds to this type of camera a great amount of flexibility and design options. Title: Pre-flight calibration of LYRA, the solar VUV radiometer on board PROBA2 Authors: Benmoussa, A.; Dammasch, I. E.; Hochedez, J. -F.; Schühle, U.; Koller, S.; Stockman, Y.; Scholze, F.; Richter, M.; Kroth, U.; Laubis, C.; Dominique, M.; Kretzschmar, M.; Mekaoui, S.; Gissot, S.; Theissen, A.; Giordanengo, B.; Bolsee, D.; Hermans, C.; Gillotay, D.; Defise, J. -M.; Schmutz, W. Bibcode: 2009A&A...508.1085B Altcode: Aims. LYRA, the Large Yield Radiometer, is a vacuum ultraviolet (VUV) solar radiometer, planned to be launched in November 2009 on the European Space Agency PROBA2, the Project for On-Board Autonomy spacecraft.
Methods: The instrument was radiometrically calibrated in the radiometry laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the Berlin Electron Storage ring for SYnchroton radiation (BESSY II). The calibration was done using monochromatized synchrotron radiation at PTB's VUV and soft X-ray radiometry beamlines using reference detectors calibrated with the help of an electrical substitution radiometer as the primary detector standard.
Results: A total relative uncertainty of the radiometric calibration of the LYRA instrument between 1% and 11% was achieved. LYRA will provide irradiance data of the Sun in four UV passbands and with high temporal resolution down to 10 ms. The present state of the LYRA pre-flight calibration is presented as well as the expected instrument performance.
Title: Hydrogen Lyman-α and Lyman-β spectral radiance profiles in the quiet Sun Authors: Tian, H.; Curdt, W.; Marsch, E.; Schühle, U. Bibcode: 2009A&A...504..239T Altcode: 2009arXiv0907.1069T Aims: We extend earlier work by studying the line profiles of the hydrogen Lyman-α and Lyman-β lines in the quiet Sun. They were obtained quasi-simultaneously in a raster scan with a size of about 150'' × 120'' near disk center.
Methods: The self-reversal depths of the Ly-α and Ly-β profiles. we are quantified by measuring the maximum spectral radiances of the two horns and the minimum spectral radiance of the central reversal. The information on the asymmetries of the Ly-α and Ly-β profiles is obtained through calculating the 1st and 3rd-order moments of the line profiles. By comparing maps of self-reversal depths and the moments with radiance images of the Lyman lines, photospheric magnetograms, and Dopplergrams of two other optically thin lines, we studied the spatial distribution of the Ly-α and Ly-β profiles with different self-reversal depths, and investigated the relationship between profile asymmetries and flows in the solar atmosphere.
Results: We find that the emissions of the Lyman lines tend to be more strongly absorbed in the internetwork, as compared to those in the network region. Almost all of the Ly-α profiles are self-reversed, while about 17% of the Ly-β profiles are not reversed. The ratio of Ly-α and Ly-β intensities seems to be independent of the magnetic field strength. Most Ly-α profiles are stronger in the blue horn, whereas most Ly-β profiles are stronger in the red horn. However, the opposite asymmetries of Ly-α and Ly-β are not correlated pixel-to-pixel. We also confirm that when larger transition-region downflows are present, the Ly-α and Ly-β profiles are more enhanced in the blue and red horns, respectively. The first-order moment of Ly-β, which reflects the combined effects of the profile asymmetry and motion of the emitting material, strongly correlates with the Doppler shifts of the Si iii and O vi lines, while this correlation is much weaker for Ly-α. Our analysis shows that both Ly-α and Ly-β might be more redshifted if stronger transition-region downflows are present. We also find that the observed average Ly-β profile is redshifted with respect to its rest position. Title: The Ly-α profile and center-to-limb variation of the quiet Sun Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.; Lemaire, P. Bibcode: 2008A&A...492L...9C Altcode: 2008arXiv0812.1441C Aims: We study the emission of the hydrogen Lyman-α line in the quiet Sun, its center-to-limb variation, and its radiance distribution. We also compare quasi-simultaneous Ly-α and Ly-β line profiles.
Methods: We used the high spectral and spatial resolution of the SUMER spectrometer and completed raster scans at various locations along the disk. For the first time, we used a method to reduce the incoming photon flux to a 20%-level by partly closing the aperture door. We also performed a quasi-simultaneous observation of both Ly-α and Ly-β at the Sun center in sit-and-stare mode. We infer the flow characteristic in the Ly-α map from variations in the calibrated λ 1206 Si iii line centroids.
Results: We present the average profile of Ly-α, its radiance distribution, its center-to-limb behaviour, and the signature of flows on the line profiles. Little center-to-limb variation and no limb brightening are observed in the profiles of the Ly-α line. In contrast to all other lines of the Lyman series, which have a red-horn asymmetry, Ly-α has a robust and - except for dark locations - dominating blue-horn asymmetry. There appears to be a brightness-to-asymmetry relationship. A similar and even clearer trend is observed in the downflow-to-asymmetry relationship. This important result is consistent with predictions from models that include flows. However, the absence of a clear center-to-limb variation in the profiles may be more indicative of an isotropic field than a mainly radial flow.
Conclusions: It appears that the ubiquitous hydrogen behaves in a similar way to a filter that dampens all signatures of the line formation by processes in both the chromosphere and transition region. Title: SWAP onboard PROBA2: An Innovative EUV Imager Designed for Space Weather Authors: de Groof, A.; Berghmans, D.; Defise, J. M.; Nicula, B.; Schuehle, U. Bibcode: 2008ESPM...122.116D Altcode: PROBA2 (PRoject for OnBoard Autonomy) is an ESA micro-satellite that is being prepared for launch in 2009. Its primary goal is the demonstration of new technologies in the space environment. Furthermore, the satellite carries an ambitious suite of both in-situ and remote sensing instruments for monitoring space weather, despite the modest onboard resources. Both the spacecraft and the remote sensing instruments are mainly developed within Belgium.

One of the main instruments, SWAP (Sun Watcher with APS detectors and image Processing), is a compact EUV imager. It carries the first APS detector with an EUV sensitive scintillator coating to be flown in orbit. In addition to the new detector, the PROBA2/SWAP design is innovative in the sense that the instrument will make heavy use of on-board data processing and autonomous operations. These will range from automatic off-pointing and tracking of appropriate solar events, to pre-downlink data prioritisation, and feature and event recognition procedures.

We discuss the first results of the SWAP pre-flight calibration and the strengths and weaknesses of the instrument [2]. With a narrow spectral bandpass centred around 17.4nm, a FOV of 54 arcmin and an image cadence of 1 min, its design is ideal for monitoring most CME associated phenomena on the solar disk and close to the limb.

[1] Defise J., Halain J., Berghmans D., et al. 2007, In: Proc. SPIE, 6689, 66890S

[2] De Groof A., Berghmans D., Nicula B., et al. 2008, Solar Phys. 249, 147-163 Title: The line profile and center-to-limb variation of quiet-Sun Lyman-alpha emission Authors: Curdt, W.; Tian, H.; Teriaca, L.; Schühle, U.; Lemaire, P. Bibcode: 2008ESPM...12.2.91C Altcode: We study the emission of the hydrogen Lyman-alpha line in the quiet Sun, its center-to-limb variation, and its radiance distribution, which we also compare to the Lyman-beta line. We use the high spectral and spatial resolution of the SUMER spectrometer and take raster scans at various locations on the disk. For the first time, we have used a new method to reduce the incoming photon flux to a 20%-level by partly closing the aperture door. We also performed a quasi-simultaneous observation of both Ly-a and Ly-b at Sun centre in sit-and-stare mode. We deduce the flow characteristic in Ly-a map from variations of the calibrated Si III line centroids. We present the average profile of Ly-a, its radiance distribution, its center-to-limb behaviour, and the signature of flows on the line profiles. Different from all other lines of the Lyman series, which have a red-horn asymmetry, Ly-a has a robust and dominating blue-horn asymmetry. To our knowledge, this result is only predicted by models which include flows. Title: CMOS-APS Detectors for Solar Physics: Lessons Learned during the SWAP Preflight Calibration Authors: De Groof, A.; Berghmans, D.; Nicula, B.; Halain, J. -P.; Defise, J. -M.; Thibert, T.; Schühle, U. Bibcode: 2008SoPh..249..147D Altcode: 2008SoPh..tmp...62D CMOS-APS imaging detectors open new opportunities for remote sensing in solar physics beyond what classical CCDs can provide, offering far less power consumption, simpler electronics, better radiation hardness, and the possibility of avoiding a mechanical shutter. The SWAP telescope onboard the PROBA2 technology demonstration satellite of the European Space Agency will be the first actual implementation of a CMOS-APS detector for solar physics in orbit. One of the goals of the SWAP project is precisely to acquire experience with the CMOS-APS technology in a real-live space science context. Such a precursor mission is essential in the preparation of missions such as Solar Orbiter where the extra CMOS-APS functionalities will be hard requirements. The current paper concentrates on specific CMOS-APS issues that were identified during the SWAP preflight calibration measurements. We will discuss the different readout possibilities that the CMOS-APS detector of SWAP provides and their associated pros and cons. In particular we describe the "image lag" effect, which results in a contamination of each image with a remnant of the previous image. We have characterised this effect for the specific SWAP implementation and we conclude with a strategy on how to successfully circumvent the problem and actually take benefit of it for solar monitoring. Title: Search for photospheric footpoints of quiet Sun transition region loops Authors: Sánchez Almeida, J.; Teriaca, L.; Sütterlin, P.; Spadaro, D.; Schühle, U.; Rutten, R. J. Bibcode: 2007A&A...475.1101S Altcode: 2007arXiv0709.3451S Context: The footpoints of quiet Sun Transition Region (TR) loops do not seem to coincide with the photospheric magnetic structures appearing in traditional low-sensitivity magnetograms.
Aims: We look for the so-far unidentified photospheric footpoints of TR loops using G-band bright points (BPs) as proxies for photospheric magnetic field concentrations.
Methods: We compare TR measurements with SoHO/SUMER and photospheric magnetic field observations obtained with the Dutch Open Telescope.
Results: Photospheric BPs are associated with bright TR structures, but they seem to avoid the brightest parts of the structure. BPs appear in regions that are globally redshifted, but they avoid extreme velocities. TR explosive events are not clearly associated with BPs.
Conclusions: The observations are not inconsistent with the BPs being footpoints of TR loops, although we have not succeeded to uniquely identify particular BPs with specific TR loops. Title: SWAP: a novel EUV telescope for space weather Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Berghmans, David; Denis, François; Mazy, Emmanuel; Thibert, Tanguy; Lecat, Jean-Hervé; Rochus, Pierre; Nicula, Bogdan; De Groof, Anik; Hochedez, Jean-François; Schühle, Udo; Ravet, Marie-Françoise; Delmotte, Frank Bibcode: 2007SPIE.6689E..0SD Altcode: 2007SPIE.6689E..24D The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is being developed to be part of the PROBA2 payload, an ESA technological mission to be launched in early 2008. SWAP is directly derived from the concept of the EIT telescope that we developed in the '90s for the SOHO mission. Several major innovations have been introduced in the design of the instrument in order to be compliant with the requirements of the PROBA2 mini-satellite: compactness with a new of-axis optical design, radiation resistance with a new CMOS-APS detector, a very low power electronics, an athermal opto-mechanical system, optimized onboard compression schemes combined with prioritization of collected data, autonomy with automatic triggering of observation and off-pointing procedures in case of Solar event occurrence, ... All these new features result from the low resource requirements (power, mass, telemetry) of the mini-satellite, but also take advantage of the specificities of a modern technological platform, such as quick pointing agility, new powerful on-board processor, Packetwire interface and autonomous operations. These new enhancements will greatly improve the operations of SWAP as a space weather sentinel from a low Earth orbit while the downlink capabilities are limited. This paper summarizes the conceptual design, the development and the qualification of the instrument, the autonomous operations and the expected performances for science exploitation. Title: Multi-wavelength Analysis of a Quiet Solar Region Authors: Tsiropoula, G.; Tziotziou, K.; Giannikakis, J.; Young, P.; Schühle, U.; Heinzel, P. Bibcode: 2007ASPC..368..171T Altcode: 2007arXiv0704.1592T We present observations of a solar quiet region obtained by the ground-based Dutch Open Telescope (DOT), and by instruments on the spacecraft SOHO and TRACE. The observations were obtained during a coordinated observing campaign on October 2005. The aim of this work is to present the rich diversity of fine-scale structures that are found at the network boundaries and their appearance in different instruments and different spectral lines that span the photosphere to the corona. Detailed studies of these structures are crucial to understanding their dynamics in different solar layers, as well as the role such structures play in the mass balance and heating of the solar atmosphere. Title: T he Lower Transition Region As Seen In The H I Lyman-α Line Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2007ESASP.641E..84T Altcode: The SUMER spectrometer aboard SOHO has been used to acquire several raster images and temporal series of quiet-Sun targets at both disk centre and the limb. Spectra have been recorded simultaneously in the H I Lyman α and the Si III 120.6 nm line. Both spatial and temporal maps of the integrated radiances appear very similar in the two lines, despite the huge difference in optical thickness, a result showing the H I Lyman α to be a good diagnostic of the dynamics and morphology of the lower transition region. Oscillations can be detected and studied at all observed locations. At disk centre, the 3 minute oscillations are sporadically observed in the inter-network but also at locations at the edges of network lanes, while 5 minute oscillations clearly dominate the network. At the limb, evidence of 3 to 5 minute oscillations is found at the base of spicules. Moreover, H I Lyman α spectra shows a high degree of variability, revealing also the signature of explosive events. The combination of high spectral purity images and slit spectra in the H I Lyman α line would therefore be an exceptional new tool to investigate the nature of the solar transition region. This line is therefore of interest for both, a high resolution channel in the EUI instrument and for the EUS spectrometer. Title: T he Lower Transitio n Region As Seen In The H I Lyman-α Line. Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2007ESASP.641E..36T Altcode: The SUMER spectrometer aboard SOHO has been used to acquire several raster images and temporal series of quiet-Sun targets at both disk centre and the limb. Spectra have been recorded simultaneously in the H I Lyman α and the Si III 120.6 nm line. Both spatial and temporal maps of the integrated radiances appear very similar in the two lines, despite the huge difference in optical thickness, a result showing the H I Lyman α to be a good diagnostic of the dynamics and morphology of the lower transition region. Oscillations can be detected and studied at all observed locations. At disk centre, the 3 minute oscillations are sporadically observed in the inter-network but also at locations at the edges of network lanes, while 5 minute oscillations clearly dominate the network. At the limb, evidence of 3 to 5 minute oscillations is found at the base of spicules. Moreover, H I Lyman α spectra shows a high degree of variability, revealing also the signature of explosive events. The combination of high spectral purity images and slit spectra in the H I Lyman α line would therefore be an exceptional new tool to investigate the nature of the solar transition region. This line is therefore of interest for both, a high resolution channel in the EUI instrument and for the EUS spectrometer. Title: T hin Silicon Carbide Coating Of The Primary Mirror Of VUV Imaging Instruments Of Solar Orbiter Authors: Schühle, U.; Uhlig, H.; Curdt, W.; Feigl, T.; Theissen, A.; Teriaca, L. Bibcode: 2007ESASP.641E..83S Altcode: We investigate the thermo-optical and vacuum- ultraviolet properties of thin silicon carbide (SiC) coatings on transparent substrates in view of their use for Solar Orbiter remote sensing VUV instrumentation. We have made experimental studies with thin SiC coatings on quartz plates to evaluate their reflective properties in the VUV spectral range between 58 nm and 123 nm. We discuss the results in relation to the visible and near infrared optical properties of the samples. A thin SiC coating of 10 nm thickness is shown to be a very promising compromise between high VUV reflectivity and low vis/IR absorption. The overall absorption of the solar spectrum by such a mirror is less than 8 %. This will be beneficial for instruments requiring a large aperture due to diffraction and radiometric limitation, in coping with the thermal heat load during the Solar Orbiter mission. As an example, we propose a design of the primary telescope mirror for the Extreme Ultraviolet Spectrometer (EUS). Title: EUI, The Ultraviolet Imaging Telescopes Of Solar Orbiter Authors: Hochedez, J. -F.; Appourchaux, T.; Defise, J. -M.; Harra, L. K.; Schühle, U.; Auchère, F.; Curdt, W.; Hancock, B.; Kretzschmar, M.; Lawrence, G.; Leclec'h, J. -C.; Marsch, E.; Mercier, R.; Parenti, S.; Podladchikova, E.; Ravet, M. -F.; Rochus, P.; Rodriguez, L.; Rouesnel, F.; Solanki, S.; Teriaca, L.; Van Driel, L.; Vial, J. -C.; Winter, B.; Zhukov, A. Bibcode: 2007ESASP.641E..33H Altcode: The scientific objectives of Solar Orbiter rely ubiquitously on EUI, its suite of solar atmosphere imaging telescopes. In the configuration discussed here, EUI includes three co-aligned High Resolution Imagers (HRI) and one Full Sun Imager (FSI). FSI and two HRIs observe in extreme ultraviolet passbands, dominated by coronal emission. Another HRI is designed for the hydrogen Lyman α radiation in the far UV, imaging the Chromosphere and the lower Transition Region. The current EUI design and some of its development challenges are highlighted. EUI profits from co-rotation phases, solar proximity and departure from the ecliptic. In synergy with the other S.O. payload, EUI probes the dynamics of the solar atmosphere, provides context data for all investigations and helps to link in-situ and remote-sensing observations. In short, it serves all four top-level goals of the mission. For these reasons, the EUI suite is keenly anticipated in the European scientific community and beyond. Title: Instrumental Approaches To Achieve The Measurements Required For Exploring The Energetics, Dynamics A nd Fine-Scale Structure Of The Sun's Magnetized Atmosphere Authors: Schühle, U. Bibcode: 2007ESASP.641E..17S Altcode: An overview is given about the technical implementation of the remote sensing instrumentation of the Solar Orbiter mission. We will discuss the "science implementation" related to the specific scientific goal "Explore the energetics, dynamics and fine-scale structure of the Sun's magnetized atmosphere". The technical approaches to implement the observational scenarios outlined in the Science Requirements Document (SRD) are reviewed. Some technical design options proposed for the remote sensing instruments will be shown in detail and some open technical issues are highlighted in regard to answering the question "How do we achieve this goal?". Title: Optical Design Of The Extreme Ultraviolet Spectrometer (EUS) On Board Solar Orbiter Authors: Middleton, K.; Da Deppo, V.; Poletto, L.; Schühle, U.; Thomas, R. J.; Young, P. R. Bibcode: 2007ESASP.641E..48M Altcode: We present optical designs for the Extreme Ultraviolet Imaging Spectrometer (EUS) proposed for Solar Orbiter. We summarise the scientific requirements for EUS and show how they translate into an instrument specification and optical design. Two design options are presented: one utilising a normal incidence telescope and one utilising a grazing incidence telescope. Both options use the same design of spectrometer, which incorporates a Toroidal Varied Line-Space (TVLS) grating, allowing high quality imaging at relatively large spectrometer magnifications. This results in a very compact yet high performance design. We give estimates of the instrument's optical performance and throughput and discuss briefly some heat management strategies. Title: LYRA - a solar UV radiometer using diamond detectors Authors: Theissen, A.; Benmoussa, A.; Schühle, U.; Hochedez, J. -F.; Schmutz, W. Bibcode: 2007msfa.conf...27T Altcode: LYRA, the Lyman-α radiometer, is a highcadence (100 Hz) solar VUV radiometer which will measure diskintegrated irradiances in 4 wavelength channels. Special emphasis is given on novel detectors based on diamond which will be tested for the first time in space. Two kinds of detectors are employed: MSM and PiNtype detectors. Their particular advantage compared to silicon detectors lies in their solar blindness with a UV/visible reduction ratio of at least four orders of magnitude, which simplifies the design of UV instruments. Title: S pace Qualification Of A Thin Wafer Lithium Niobate Etalon For The Visible Light Imager And Magnetograph (Vim) Authors: Schühle, U.; Mathew, S. K.; Wedemeier, M.; Hartwig, H.; Ballesteros, E.; Martinez Pillet, V.; Solanki, S. K. Bibcode: 2007ESASP.641E..82S Altcode: For the Visible Light Imager and Magnetograph (VIM) a high-resolution filtergraph is under design. The system takes advantage of a lithium niobate (LiNbO3) crystal which can be used as a scanning filter using high voltage for tuning. We have undertaken first studies to qualify a lithium niobate wafer of 70 mm aperture size for deployment and use in space. We show the results of the mechanical mounting and vibration and thermal cycling tests as well as stability tests under fast voltage tuning in vacuum. Although these tests have all been very successful, further environmental testing is necessary to fully space-qualify the filter for the Solar Orbiter mission. Title: Solar Coronal Magnetic Field Mapper Authors: Solanki, S. K.; Raouafi, N. -E.; Gandorfer, A.; Schühle, U.; Lagg, A. Bibcode: 2006ESASP.617E.160S Altcode: 2006soho...17E.160S No abstract at ADS Title: Hα Chromospheric Mottles and their UV/EUV Counterparts Seen by SOHO/Sumer Authors: Tziotziou, K.; Heinzel, P.; Tsiropoula, G.; Schühle, U. Bibcode: 2006ESASP.617E.112T Altcode: 2006soho...17E.112T No abstract at ADS Title: The Dynamic Nature of the Lower Transition Region as Revealed by Spectroscopy of the Hydrogen Lyman-α Line Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2006ESASP.617E..77T Altcode: 2006soho...17E..77T No abstract at ADS Title: Prominence Parameters Derived from Hydrogen Lyman-α Spectral Profiles Measured by SOHO/SUMER Authors: Gunár, S.; Teriaca, L.; Heinzel, P.; Schühle, U. Bibcode: 2006ESASP.617E..63G Altcode: 2006soho...17E..63G No abstract at ADS Title: LYRA, a solar UV radiometer on Proba2 Authors: Hochedez, J. -F.; Schmutz, W.; Stockman, Y.; Schühle, U.; Benmoussa, A.; Koller, S.; Haenen, K.; Berghmans, D.; Defise, J. -M.; Halain, J. -P.; Theissen, A.; Delouille, V.; Slemzin, V.; Gillotay, D.; Fussen, D.; Dominique, M.; Vanhellemont, F.; McMullin, D.; Kretzschmar, M.; Mitrofanov, A.; Nicula, B.; Wauters, L.; Roth, H.; Rozanov, E.; Rüedi, I.; Wehrli, C.; Soltani, A.; Amano, H.; van der Linden, R.; Zhukov, A.; Clette, F.; Koizumi, S.; Mortet, V.; Remes, Z.; Petersen, R.; Nesládek, M.; D'Olieslaeger, M.; Roggen, J.; Rochus, P. Bibcode: 2006AdSpR..37..303H Altcode: LYRA is the solar UV radiometer that will embark in 2006 onboard Proba2, a technologically oriented ESA micro-mission. LYRA is designed and manufactured by a Belgian Swiss German consortium (ROB, PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international collaborations. It will monitor the solar irradiance in four UV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and Space Weather: (1) the 115 125 nm Lyman-α channel, (2) the 200 220 nm Herzberg continuum range, (3) the Aluminium filter channel (17 70 nm) including He II at 30.4 nm and (4) the Zirconium filter channel (1 20 nm). The radiometric calibration will be traceable to synchrotron source standards (PTB and NIST). The stability will be monitored by onboard calibration sources (LEDs), which allow to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of a pioneering UV detectors program. Diamond sensors make the instruments radiation-hard and solar-blind: their high bandgap energy makes them insensitive to visible light and, therefore, make dispensable visible light blocking filters, which seriously attenuate the desired ultraviolet signal. Their elimination augments the effective area and hence the signal-to-noise, therefore increasing the precision and the cadence. The SWAP EUV imaging telescope will operate next to LYRA on Proba2. Together, they will establish a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter. Title: SWAP onboard PROBA 2, a new EUV imager for solar monitoring Authors: Berghmans, D.; Hochedez, J. F.; Defise, J. M.; Lecat, J. H.; Nicula, B.; Slemzin, V.; Lawrence, G.; Katsyiannis, A. C.; van der Linden, R.; Zhukov, A.; Clette, F.; Rochus, P.; Mazy, E.; Thibert, T.; Nicolosi, P.; Pelizzo, M. -G.; Schühle, U. Bibcode: 2006AdSpR..38.1807B Altcode: SWAP (Sun Watcher using Active Pixel system detector and image processing) is a solar imager in the extreme ultraviolet (EUV) that has been selected to fly in 2007 on the PROBA 2 technological platform, an ESA program. SWAP will use an off-axis Ritchey Chrétien telescope equipped with an EUV enhanced active pixel sensor detector (coated APS). This type of detector has advantages that promise to be very profitable for solar EUV imaging. SWAP will provide solar coronal images at a 1-min cadence in a bandpass centered on 17.5 nm. Observations with this specific wavelength allow detecting phenomena, such as solar flares or EIT-waves, associated with the early phase of coronal mass ejections. Image processing software will be developed that automatically detects these phenomena and sends out space weather warnings. Together with its sister instrument LYRA, also onboard PROBA 2, SWAP will serve as a high performance solar monitoring tool to be used in operational space weather forecasting. The SWAP data will complement the solar observations provided by instruments like SOHO-EIT, and STEREO-SECCHI. Title: The Dynamics of the Lower Transition Region as Inferred from Spectroscopy of the Hydrogen LYMAN-α Line Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2005ESASP.600E.100T Altcode: 2005ESPM...11..100T; 2005dysu.confE.100T No abstract at ADS Title: A new relation between the central spectral solar H I Lyman α irradiance and the line irradiance measured by SUMER/SOHO during the cycle 23 Authors: Emerich, Claude; Lemaire, Philippe; Vial, Jean-Claude; Curdt, Werner; Schühle, Udo; Wilhelm, Klaus Bibcode: 2005Icar..178..429E Altcode: The spectral irradiance at the center of the solar H I Lyman α ( λ=121.5664nm, referred to as Lyα in this paper) line profile is the main excitation source responsible for the atomic hydrogen resonant scattering of cool material in our Solar System. It has therefore to be known with the best possible accuracy in order to model the various Lyα emissions taking place in planetary, cometary, and interplanetary environments. Since the only permanently monitored solar irradiance is the total one (i.e. integrated over the whole Lyα line profile), Vidal-Madjar [1975. Evolution of the solar Lyman alpha flux during four consecutive years. Solar Phys. 40, 69-86] using Orbiting Solar Observatory 5 (OSO-5) satellite Lyα data, established a semi-empirical formula allowing him to deduce the central spectral Lyα irradiance from the total one. This relation has been extensively used for three decades. But, at the low altitude of the OSO-5 orbit, the central part of the solar line profile was deeply absorbed by a large column of exospheric atomic hydrogen. Consequently, the spectral irradiance at the center of the line was obtained by a complex procedure confronting the observations with simulations of both the geocoronal absorption and the self-reversed shape of the solar Lyα profile. The SUMER spectrometer onboard SOHO positioned well outside the hydrogen geocorona, provided full-Sun Lyα profiles, not affected by such an absorption [Lemaire et al., 1998. Solar H I Lyman α full disk profile obtained with the SUMER/SOHO spectrometer. Astron. Astrophys. 334, 1095-1098; 2002. Variation of the full Sun Hydrogen Lyman α and β profiles with the activity cycle. Proc. SOHO 11 Symposium, ESA SP-508, 219-222; 2004. Variation of the full Sun Hydrogen Lyman profiles through solar cycle 23. COSPAR 2004 Meeting], making it—for the first time—possible to measure the spectral and total Lyα solar irradiances directly and simultaneously. A new relation between these two quantities is derived in an expression that is formally similar to the previous one, but with significantly different parameters. After having discussed the potential causes for such differences, it is suggested that the new relation should replace the old one for any future modeling of the numerous Lyα absorptions and emissions observed in the Solar System. Title: The Structure of the Lower Transition Region as Inferred from the Hydrogen LYMAN-α Line Radiance Authors: Teriaca, L.; Schühle, U.; Solanki, S. K.; Curdt, W.; Marsch, E. Bibcode: 2005ESASP.596E..66T Altcode: 2005ccmf.confE..66T No abstract at ADS Title: On the nature of the unidentified solar emission near 117 nm Authors: Wilhelm, K.; Schühle, U.; Curdt, W.; Hilchenbach, M.; Marsch, E.; Lemaire, P.; Bertaux, J. -L.; Jordan, S. D.; Feldman, U. Bibcode: 2005A&A...439..701W Altcode: Spectral observations of the Sun in the vacuum-ultraviolet wavelength range by SUMER on SOHO led to the discovery of unusual emission features - called humps here - at 116.70 nm and 117.05 nm on either side of the He i 58.43 nm line. This resonance line is seen in the second order of diffraction, whereas the humps are recorded in the first order with the SUMER spectrometer. In its spectra both orders are superimposed. Two less pronounced humps can be detected at 117.27 nm and near 117.85 nm. After rejecting various possibilities of an instrumental cause of the humps, they are studied in different solar regions. Most of the measurements, in particular those related to the limb-brightening characteristics, indicate that the humps are not part of the background continuum. An assembly of spectrally-unresolved atomic or ionic emission lines might be contributing to the hump at 117.05 nm, but no such lines are known near 116.7 nm. It is concluded that we detect genuine radiation, the generation of which is not understood. A two-photon emission process, parametric frequency down conversion, and molecular emissions are briefly considered as causes of the humps, but a final conclusion could not be reached. Title: Variation of the full Sun hydrogen Lyman profiles through solar cycle 23 Authors: Lemaire, P.; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2005AdSpR..35..384L Altcode: The hydrogen Lyman (Lyα, 121.267 nm and Lyβ, 102.572 nm) lines are important contributors to the solar extreme ultra violet (EUV) flux which illuminates the upper Earth’s atmosphere. From high resolution spectral observations performed with the solar ultraviolet measurement of emitted radiations (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO), the detailed profiles of these two lines have been obtained. Some insights into the variation of the shape of the profiles, sampled throughout the present solar cycle 23, are given and discussed. Title: SWAP: Sun watcher with a new EUV telescope on a technology demonstration platform Authors: Defise, Jean-Marc; Lecat, Jean-Hervé; Mazy, Emmanuel; Rochus, Pierre; Rossi, Laurence; Thibert, Tanguy; Gillis, Jean-Marie; Berghmans, David; Hochedez, Jean-François; Schühle, Udo Bibcode: 2004ESASP.554..257D Altcode: 2004icso.conf..257D SWAP (SWAP (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument that has been selected to fly on the PROBA-2 technology demonstration platform, a program of the European Space Agency (ESA) to be launched in 2006. SWAP is based on an off-axis degraded Ritchey Chretien telescope that will image the EUV solar corona at 19.5 nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity enhanced CMOS APS detector. The optical design and the optical coatings are derived from the Extreme Ultraviolet Imaging Telescope (EIT) operating on-board SOHO since 1995. It has been adapted for a single wavelength telescope with off-axis optics. It allows to use smaller optics and filters, with simple internal baffles avoiding external protruding parts. The superpolished optics will receive a multilayer coating that provides spectral selection centred on 19.5 nm and EUV reflectivity in normal incidence. This compact design is specifically adapted for accommodation on PROBA-2, where mass and envelope requirements are very stringent The SWAP PROBA-2 program will be an opportunity to demonstrate this new optical concept, while it will also validate space remote sensing with APS detectors, as well as on-board image processing capabilities. On the science outcomes, SWAP will provide solar corona images in the Fe XII line on a baselined 2-min cadence. Observations with this specific wavelength allow detecting phenomena, such as solar flares or 'EIT-waves', associated with the early phase of coronal mass ejections. The SWAP data will complement the observations provided by SOHO-EIT, and STEREO-SECCHI. Title: A New Relation between Central and Total Solar H I Lyman-α Irradiances, as measured by SOHO during Solar Cycle 23 (1996-2003) Authors: Emerich, C.; Lemaire, P.; Vial, J. -C.; Curdt, W.; Schüle, U.; Wilhelm, K. Bibcode: 2004AAS...204.9802E Altcode: 2004BAAS...36..984E The spectral irradiance at the center of the solar H Ly-α line profile is the main excitation source responsible for the atomic hydrogen resonant scattering in cool material. It has therefore to be known with the best possible accuracy to model the H Ly-α emissions taking place in planetary, cometary and interplanetary environments. On the other hand, the only permanently monitored solar irradiance is the total one - either measured by near-Earth satellites, or deduced from its correlation with solar activity indexes. It is the reason why Vidal-Madjar (1975) using OSO-5 satellite H Ly-α data, established a semi-empirical formula allowing to deduce the central H Ly-α irradiance from the integrated one. This relation has been extensively used for three decades. In fact, at the low altitude of the OSO-5 orbit, the observed central part of the solar line profiles was deeply absorbed by a large column of exospheric atomic hydrogen. Consequently, the solar line center irradiances were not measured directly, but obtained by confronting the measurements with simulations of both the geocoronal absorption and the self-reversed shape of the central solar profile itself.

On the contrary, the SOHO/SUMER spectrometer orbiting well outside the H geocoronal envelope (at the L1 Sun-Earth Lagrange point), provided full Sun H Ly-α profiles, exempt from any central geocoronal absorption (Lemaire et al. (1998, 2002, 2004)). This has made it possible to directly measure the central H Ly-α solar irradiances as a function of the integrated ones, during eight years of Solar Cycle 23. The newly obtained relation confirms the general trend of the previous one, but it is characterized by significantly different coefficients. It will therefore provide new and more accurate inputs for the future modeling of the various Ly-α emissions occurring inside the Solar System. Title: Flare observation of the Sun as a star by SUMER/SOHO in the hydrogen Lyman continuum Authors: Lemaire, P.; Gouttebroze, P.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2004A&A...418..737L Altcode: During the execution of the programme ``Sun as a star'', while the SUMER (Solar Ultraviolet Emission of Emitted Radiation)/SOHO (SOlar and Heliospheric Observatory) slit was collecting the scattered radiation from the telescope mirror far away from the solar disk image, a class X5.3/3b flare erupted on the solar disk, on 25 August 2001. During the first phase of the flare a relative increase of a few percent was detected at the head of the hydrogen Lyman continuum. After correction from the instrumental parameters, the relative signal increase is 70% at the head of the Lyman continuum (910 Å), and 190% in the C II 904 Å multiplet. Accounting for the area of the flare region, the local increase of the radiance of the Lyman continuum and of the C II lines is estimated to be a factor of several thousands. We compare this result with other solar observations and models.

Appendix A is only available in electronic form at http://www.edpsciences.org Title: Development of imaging arrays for solar UV observations based on wide band gap materials Authors: Schuehle, Udo H.; Hochedez, Jean-Francois E.; Pau, Jose Luis; Rivera, Carlos; Munoz, Elias; Alvarez, Jose; Kleider, Jean-Paul; Lemaire, Philippe; Appourchaux, Thierry; Fleck, Bernhard; Peacock, Anthony; Richter, Mathias; Kroth, Udo; Gottwald, Alexander; Castex, Marie-Claude; Deneuville, Alain; Muret, Pierre; Nesladek, Milos; Omnes, Franck; John, Joachim; Van Hoof, Chris Bibcode: 2004SPIE.5171..231S Altcode: Solar ultraviolet imaging instruments in space pose most demanding requirements on their detectors in terms of dynamic range, low noise, high speed, and high resolution. Yet UV detectors used on missions presently in space have major drawbacks limiting their performance and stability. In view of future solar space missions we have started the development of new imaging array devices based on wide band gap materials (WBGM), for which the expected benefits of the new sensors - primarily visible blindness and radiation hardness - will be highly valuable. Within this initiative, called "Blind to Optical Light Detectors (BOLD)", we have investigated devices made of AlGa-nitrides and diamond. We present results of the responsivity measurements extending from the visible down to extreme UV wavelengths. We discuss the possible benefits of these new devices and point out ways to build new imaging arrays for future space missions. Title: SWAP: Sun watcher using APS detector on-board PROBA-2, a new EUV off-axis telescope on a technology demonstration platform Authors: Defise, Jean-Marc; Berghmans, David; Hochedez, Jean-Francois E.; Lecat, Jean-Herve M.; Mazy, Emmanuel; Rochus, Pierre L.; Thibert, Tanguy; Nicolosi, Piergiorgio; Pelizzo, Maria G.; Schuehle, Udo H.; Van der Linden, Ronald A. M.; Zhukov, Andrei N. Bibcode: 2004SPIE.5171..143D Altcode: SWAP (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument that has been selected to fly on the PROBA-II technology demonstration platform, a program of the European Space Agency (ESA) to be launched in 2006. This paper presents the instrument concept and its scientific goals. SWAP uses an off-axis Ritchey Chretien telescope that will image the EUV solar corona at 19.5 nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity enhanced CMOS APS detector. This type of detector has advantages that promise to be very profitable for solar EUV imaging. The SWAP design is built on a similar concept as the MAGRITTE instrument suite for the NASA Solar Dynamics Observatory (SDO) mission to be launched in 2007. The optics have been adapted to the detector size. The SWAP PROBA-2 program will be an opportunity to demonstrate and validate the optical concept of MAGRITTE, while it will also validate space remote sensing with APS detectors. On the science outcomes, SWAP will provide solar corona images in the Fe XII line on a baselined 1-min cadence. Observations with this specific wavelength allow detecting phenomena, such as solar flares or 'EIT-waves", associated with the early phase of coronal mass ejections. Image recognition software will be developed that automatically detects these phenomena and sends out space weather warnings. Different modules of this software will run both on the ground system as well as on the onboard computer of PROBA II. The SWAP data will complement the observations provided by SOHO-EIT, and STEREO-SECCHI. Title: MAGRITTE: an instrument suite for the solar atmospheric imaging assembly (AIA) aboard the Solar Dynamics Observatory Authors: Rochus, Pierre L.; Defise, Jean-Marc; Halain, Jean-Philippe; Jamar, Claude A. J.; Mazy, Emmanuel; Rossi, Laurence; Thibert, Tanguy; Clette, Frederic; Cugnon, Pierre; Berghmans, David; Hochedez, Jean-Francois E.; Delaboudiniere, Jean-Pierre; Auchere, Frederic; Mercier, Raymond; Ravet, Marie-Francoise; Delmotte, Franck; Idir, Mourad; Schuehle, Udo H.; Bothmer, Volker; Fineschi, Silvano; Howard, Russell A.; Moses, John D.; Newmark, Jeffrey S. Bibcode: 2004SPIE.5171...53R Altcode: The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory will characterize the dynamical evolution of the solar plasma from the chromosphere to the corona, and will follow the connection of plasma dynamics with magnetic activity throughout the solar atmosphere. The AIA consists of 7 high-resolution imaging telescopes in the following spectral bandpasses: 1215Å. Ly-a, 304 Å He II, 629 Å OV, 465 Å Ne VII, 195 Å Fe XII (includes Fe XXIV), 284 Å Fe XV, and 335 Å Fe XVI. The telescopes are grouped by instrumental approach: the MAGRITTE Filtergraphs (R. MAGRITTE, famous 20th Century Belgian Surrealistic Artist), five multilayer EUV channels with bandpasses ranging from 195 to 1216 Å, and the SPECTRE Spectroheliograph with one soft-EUV channel at OV 629 Å. They will be simultaneously operated with a 10-second imaging cadence. These two instruments, the electronic boxes and two redundant Guide Telescopes (GT) constitute the AIA suite. They will be mounted and coaligned on a dedicated common optical bench. The GTs will provide pointing jitter information to the whole SHARPP assembly. This paper presents the selected technologies, the different challenges, the trade-offs to be made in phase A, and the model philosophy. From a scientific viewpoint, the unique combination high temporal and spatial resolutions with the simultaneous multi-channel capability will allow MAGRITTE / SPECTRE to explore new domains in the dynamics of the solar atmosphere, in particular the fast small-scale phenomena. We show how the spectral channels of the different instruments were derived to fulfill the AIA scientific objectives, and we outline how this imager array will address key science issues, like the transition region and coronal waves or flare precursors, in coordination with other SDO experiments. We finally describe the real-time solar monitoring products that will be made available for space-weather forecasting applications. Title: Variation of the full Sun hydrogen Lyman profiles through solar cycle 23 Authors: Lemaire, P.; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2004cosp...35..510L Altcode: 2004cosp.meet..510L The hydrogen Lyman (121.267 nm and 102.572 nm) lines are important contributors to the solar EUV flux which illuminates the upper Earth's atmosphere. From high resolution spectral observations performed with the SUMER FUV-EUV spectrometer on SoHO, the detailed profiles of these two lines have been obtained. Some insights into the variation of the shape of the profiles, sampled throughout the present solar cycle 23, are shown and discussed. Title: Calibration of space instrumentation with synchrotron radiation Authors: Richter, M.; Gottwald, A.; Scholze, F.; Schühle, U.; Ulm, G. Bibcode: 2004cosp...35.1938R Altcode: 2004cosp.meet.1938R The Physikalisch-Technische Bundesanstalt (PTB) is Germany's national metrology institute providing scientific and technical services. For more than 20 years, PTB has used synchrotron radiation at the electron storage rings BESSY I and BESSY II for photon metrology in the spectral range from UV radiation to X-rays, e.g. for the calibration of radiation sources, detectors, and spectrometers as well as for the characterization of optical components. Most of the measurements are based on two different primary standards, electron storage rings as primary radiation source standards and cryogenic electrical substitution radiometers as primary detector standards. Many activities are related to radiometric calibrations of space-based instruments for extraterrestrial, solar, and astronomical missions. Outstanding examples have been the calibration of the SUMER and CDS spectrographs of the SOHO mission, X-ray detector calibrations for the X-ray observatories Chandra and XMM-Newton, and the calibration of Lyman-alpha detectors for the NASA satellites TWINS. This contribution presents examples from recent work, in particular within the framework of the ESA projects PROBA 2 and Solar Orbiter. Title: Solar-Blind Diamond Detectors for Lyra, the Solar VUV Radiometer on Board Proba II Authors: Benmoussa, A.; Hochedez, J. -F.; Schmutz, W. K.; Schühle, U.; Nesládek, M.; Stockman, Y.; Kroth, U.; Richter, M.; Theissen, A.; Remes, Z.; Haenen, K.; Mortet, V.; Koller, S.; Halain, J. P.; Petersen, R.; Dominique, M.; D'Olieslaeger, M. Bibcode: 2003ExA....16..141B Altcode: Fabrication, packaging and experimental results on the calibration of metal-semiconductor-metal (MSM) photodetectors made on diamond are reported. LYRA (Lyman-α RAdiometer onboard PROBA-2) will use diamond detectors for the first time in space for a solar physics instrument. A set of measurement campaigns was designed to obtain the XUV-to-VIS responsivity of the devices and other characterizations. The measurements of responsivity in EUV and VUV spectral ranges (40 240 nm) have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The longer wavelength range from 210 to 1127 nm was measured with monochromatic light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a photoresponse which lie in the 35 65 mA/W range at 200 nm (corresponding to an external quantum efficiency of 20 40%) and indicate a visible rejection ratio (200 500 nm) higher than four orders of magnitude. Title: Cleanliness and calibration stability of UV instruments on SOHO Authors: Schuehle, Udo H. Bibcode: 2003SPIE.4853...88S Altcode: Optical instruments for solar observations from space have in the past suffered from degradation of responsivity caused by contamination from various materials used in spacecraft and instrument construction. This was particularly detrimental in the ultraviolet range of the spectrum where the solar irradiance is weak, compared to the visible, yet strong enough to cause polymerization of organic contaminants on optical surfaces that are continuously exposed. The Solar and Heliospheric Observatory (SOHO) mission could largely avoid such effects. Material selection and special design features of instruments and spacecraft contributed mostly to this success. The various kinds of remote sensing instruments on SOHO have achieved a stability of their responsivity through special cleanliness requirements. This contribution will highlight those design aspects which are generally useful for future solar missions. Analysis of instrument responsivity data shows that under these circumstances the stability was actually not limited by contamination but by the instabilities inherent to the present detector technology. Title: Intercalibration of SUMER and CDS on SOHO. III. SUMER and CDS-GIS Authors: Pauluhn, Anuschka; Lang, Jim; Breeveld, Eddie R.; Solanki, Sami K.; Schühle, Udo Bibcode: 2003ApOpt..42..657P Altcode: Simultaneous observation of the same solar sources with different instruments is one way to test prelaunch radiometric calibrations and to detect changes in responsivity with time of extreme-ultraviolet instruments in space. Here we present the results of intercalibration of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrometer (detectors A and B) and the GIS (Grazing Incidence Spectrometer), one of two spectrometers that compose the CDS (Coronal Diagnostic Spectrometer) on the Solar and Heliospheric Observatory (SOHO). The two instruments observed simultaneously radiances of emission lines at or near the center of the solar disk. The emission line chosen for intercomparison was Ne viii at 770 Å. However, such an intercomparison of the SUMER and CDS-GIS measurements means comparing two data sets with large differences in resolution and field of view. The latter difference, especially, introduces differences in the measured intensities caused by the solar variability that is relatively strong in the 770- Å line. Using a statistical approach to overcome this problem, we found that the ratio of the GIS to the SUMER average radiances amounted to 2.6 +/- 0.9 before the SOHO ’s loss of attitude and to 2.1 +/- 0.7 afterward. These findings confirm earlier estimates of the GIS ’s responsivity being too low, and an update of the GIS calibration is recommended. Despite the large differences in resolution and field of view of the two instruments, the shapes of their normalized and rescaled histograms of the radiances agree well and therefore represent characteristic features of the Ne viii line. Title: New UV detectors for solar observations Authors: Hochedez, Jean-Francois E.; Schuehle, Udo H.; Pau, Jose L.; Alvarez, Jose; Hainaut, Olivier; Appourchaux, Thierry P.; Auret, F. D.; Belsky, Andrei; Bergonzo, Philippe; Castex, M. C.; Deneuville, A.; Dhez, Pierre; Fleck, Bernhard; Haenen, Ken; Idir, Mourad; Kleider, Jean Paul; Lefeuvre, Elie; Lemaire, Philippe; Monroy, E.; Muret, P.; Munoz, Elias; Nesladek, Milos; Omnes, Franck; Pace, Emanuele; Peacock, Anthony J.; Van Hoof, Chris A. Bibcode: 2003SPIE.4853..419H Altcode: BOLD (Blind to the Optical Light Detectors) is an international initiative dedicated to the development of novel imaging detectors for UV solar observations. It relies on the properties of wide bandgap materials (in particular diamond and Al-Ga-nitrides). The investigation is proposed in view of the Solar Orbiter (S.O.) UV instruments, for which the expected benefits of the new sensors -primarily visible blindness and radiation hardness- will be highly valuable. Despite various advances in the technology of imaging detectors over the last decades, the present UV imagers based on silicon CCDs or microchannel plates exhibit limitations inherent to their actual material and technology. Yet, the utmost spatial resolution, fast temporal cadence, sensitivity, and photometric accuracy will be decisive for the forthcoming solar space missions. The advent of imagers based on wide-bandgap materials will permit new observations and, by simplifying their design, cheaper instruments. As for the Solar Orbiter, the aspiration for wide-bandgap material (WBGM) based UV detectors is still more sensible because the spacecraft will approach the Sun where the heat and the radiation fluxes are high. We describe the motivations, and present the program to achieve revolutionary flight cameras within the Solar Orbiter schedule as well as relevant UV measurements. Title: Quiet-Sun chromospheric network evolution Authors: Lemaire, Philippe; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2002ESASP.505..477L Altcode: 2002solm.conf..477L; 2002IAUCo.188..477L Using the SUMER/SOHO spectrometer we have observed the same quiet-Sun area during several days in a set of eight spectral lines of the transition region. Line intensity maps of the rastered areas are used to separate the interior of the supergranular cells from the network. Then, following the evolution of the supergranular pattern, we measure the variations of intensity and the Doppler shifts at several temperatures of formation of the transition region. We find that the overall flow velocity of the cell interior and the network generally decays within ten hours, which represents a significant part of the supergranular lifetime. Title: Preface (SOLMAG 2002) Authors: Tsiropoula, Georgia; Schühle, Udo Bibcode: 2002ESASP.505D..13T Altcode: 2002IAUCo.188D..13T; 2002solm.confD..13T No abstract at ADS Title: Intercalibration of CDS and SUMER Authors: Pauluhn, A.; Lang, J.; Schühle, U.; Solanki, S. K.; Wilhelm, K.; Pike, C. D.; Thompson, W. T.; Rüedi, I.; Hollandt, J.; Huber, M. C. E. Bibcode: 2002ESASP.508..223P Altcode: 2002soho...11..223P The outcome of the Joint Observing Programme (JOP) Intercal-01, which is the intercalibration of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument (detectors A and B) and the two CDS (Coronal Diagnostic Spectrometer) instruments, the Normal Incidence Spectrometer (NIS) and the Grazing Incidence Spectrometer (GIS), is presented. Recent calibration updates of both instruments have been employed, and the results indicate a very good correlation and agreement of the measured radiances within the individual uncertainties. Title: Variation of the full Sun hydrogen Lyman α and β profiles with the activity cycle Authors: Lemaire, Philippe; Emerich, C.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2002ESASP.508..219L Altcode: 2002soho...11..219L Full Sun hydrogen Lyman α and β profiles obtained through the activity cycle are needed to compare with stars, to understand the hydrogen distribution in the heliosphere and to evaluate the processes in the upper planetary atmospheres. Using the SUMER/SOHO telesocope scattered light properties, we have measured the Lyman α and β profiles at different epochs of the solar activity cycle. Here we report modifications in the intensity and the shape of the profiles. Title: Transition region quiet sun velocity field evolution Authors: Lemaire, P.; Artzner, G.; Vial, J. -C.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 2002AdSpR..30..487L Altcode: The UV/EUV SUMER spectrometer aboard SOHO can record profiles of lines emitted by elements at different stages of ionization corresponding to several temperatures within the transition region temperature range. During the solar cycle minimum in July 1996, we were able to observe the quiet Sun during five consecutive days. From the line positions we have determined the velocity fields and follow their time variations at different temperatures in the transition region. The line intensity maps are used to separate supergranular cells and network and they allow to compare the behaviors of the velocity fields evolution in the two structures. The results are critically analyzed and discussed. Title: Solar Vacuum-ultraviolet Radiometry with SUMER Authors: Wilhelm, K.; Schuhle, U.; Curdt, W.; Dammasch, I. E.; Hollandt, J.; Lemaire, P.; Huber, M. C. E. Bibcode: 2002ISSIR...2..145W Altcode: 2002ESASR...2..145W; 2002rcs..conf..145W Since the beginning of 1996, the space-based telescope and spectrograph SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on the SOlar and Heliospheric Observatory (SOHO) of ESA and NASA has obtained spectra of many features of the quiescent and active Sun with high spectral and spatial resolution. In addition, irradiance and radiance measurements of line and continuum emission have been performed in the wavelength range 46.5 nm to 161.0 nm. The instrument was radiometrically calibrated against the Berlin Electron Storage ring for SYnchrotron radiation (BESSY I), a primary source standard, with the help of a transfer source standard based on a hollow-cathode discharge lamp. A thorough cleanliness programme, specifically aimed at chemical contamination control, resulted in an excellent radiometric stability of the normal-incidence optical system as well as of the detectors. This has been verified under operational conditions by various techniques employed during the SOHO mission, such as line-ratio studies, observations of stars, and comparisons with other instruments. The observations provide vacuum-ultraviolet (VUV) radiometry of the Sun in many emission lines and continua of atoms and ions with relative standard uncertainties of 15 % (detector A) and 20 % (detector B) for the wavelength range 53 nm to 124 nm, with larger uncertainties outside this interval and after the SOHO recovery in 1998. We report on the present state of the SUMER radiometric calibration and provide a full bibliography related to this topic. Title: The Solar Orbiter Mission and Design Recommendations Authors: Schuhle, U.; Thomas, R.; Hochedez, J. -F. Bibcode: 2002ISSIR...2..361S Altcode: 2002ESASR...2..361S; 2002rcs..conf..361S A short overview is given of the Solar Orbiter mission. First, the key scientific aims of the mission are briefly described. As the mission profile has consequences on the design of the payload instruments and their calibration, the mission design is described. Possible implications and problems for the cleanliness and the calibration stability of the instruments are outlined. Some solutions are discussed. Title: Intercalibration of CDS and SUMER Authors: Pauluhn, A.; Lang, J.; Schuhle, U.; Solanki, S. K.; Wilhelm, K.; Thompson, W. T.; Pike, C. D.; Ruedi, I.; Hollandt, J.; Huber, M. C. E. Bibcode: 2002ISSIR...2..235P Altcode: 2002rcs..conf..235P; 2002ESASR...2..235P Simultaneous observations of the same solar features with different instruments provide a way to compare radiometric calibrations and detect changes in responsivity with time of EUV instruments in space within the combined uncertainties of the individual instruments. Here we present the intercalibration of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument (detectors A and B) and the two CDS (Coronal Diagnostic Spectrometer) instruments, the Normal Incidence Spectrometer (NIS) and the Grazing Incidence Spectrometer (GIS) on the Solar and Heliospheric Observatory (SOHO). This work describes the results of the Joint Observing Programme Intercal 01 and presents quiet-Sun comparisons from March 1996 up to February 2001, which represents the complete set of all available Intercal 01 measurements. Recent calibration updates of both instruments are employed, and the results indicate a very good correlation and agreement of the measured radiances within the combined uncertainties. Title: Properties of ultraviolet lines observed with the Coronal Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun Authors: Stucki, K.; Solanki, S. K.; Pike, C. D.; Schühle, U.; Rüedi, I.; Pauluhn, A.; Brković, A. Bibcode: 2002A&A...381..653S Altcode: We present an analysis of 14 ultraviolet emission lines belonging to different atoms and ions observed inside polar coronal holes and in the normal quiet Sun. The observations were made with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO). This study extends previous investigations made with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer to higher temperatures. We compare line intensities, shifts and widths in coronal holes with the corresponding values obtained in the quiet Sun. While all lines formed at temperatures above 7 x 105 K show clearly the presence of the hole in their intensities, differences in line width are more subtle, with cooler lines being broader in coronal holes, while hotter lines tend to be narrower. According to the present data all lines are blueshifted inside the coronal hole compared to the normal quiet Sun. Almost all the lines formed between 80 000 K and 600 000 K (i.e. transition-region lines) show a correlation between blueshifts and brightness within coronal holes. This is in agreement with the conclusion reached by Hassler et al. (\cite{Hassler1999}) that the fast solar wind emanates from the network and supports our previous study (Stucki et al. 2000b). For coronal lines, this trend seems to be reversed. Title: New UV Detector Concepts Authors: Hochedez, J. -F.; Schuhle, U.; Lemaire, P. Bibcode: 2002ISSIR...2..371H Altcode: 2002rcs..conf..371H; 2002ESASR...2..371H BOLD (Blind to the Optical Light Detectors) is an international initiative dedicated to the development of novel imaging detectors for UV solar observations. It relies on the properties of wide-bandgap semiconductor materials (in particular diamond and Al-Ganitrides). This investigation is proposed in view of the Solar Orbiter UV instruments, for which the expected benefits of the new sensors, visible blindness and radiation hardness, will be highly valuable. Despite various advances in the technology of imaging detectors over the last few decades, the present UV imagers based on silicon CCDs or microchannel plates exhibit limitations which are inherent to their actual material and technology. Yet the utmost spatial resolution, fast temporal cadence, sensitivity, and photometric accuracy will all be decisive for forthcoming solar space missions. The advent of imagers made of large wide-bandgap semiconductors would surmount many present weaknesses. This would open up new scientific prospects and, by simplifying their design, would even make the instruments cheaper. As for the Solar Orbiter, the aspiration for wide-bandgap semiconductor-based UV detectors is still more desirable because the spacecraft will approach the Sun where heat and radiation fluxes are high. We describe the motivations leading to such new developments, and present a programme to achieve revolutionary flight cameras within the Solar Orbiter schedule. Title: Intercalibration of SUMER and CDS on SOHO. II. SUMER detectors A and B and CDS NIS Authors: Pauluhn, Anuschka; Rüedi, Isabelle; Solanki, Sami K.; Schühle, Udo; Wilhelm, Klaus; Lang, Jim; Thompson, William T.; Hollandt, Jörg Bibcode: 2001ApOpt..40.6292P Altcode: Results of an intercalibration between the extreme-ultraviolet spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on board the Solar and Heliospheric Observatory (SOHO) are reported. The results of the joint observing program Intercal_01 are described, and intercalibration results up to July 2000 of both SUMER detectors A and B and of the CDS Normal Incidence Spectrometer (NIS) are presented. The instruments simultaneously observed radiance of emission lines at the center of the Sun, and three lines have been chosen for intercomparison: He I 584 Å, Mg X 609 Å, and Mg X 624 Å. Initially the same area was observed by both instruments, but, after restrictions were imposed by the scanning mechanism of SUMER in November 1996, the instruments viewed areas of different sizes. Nevertheless, the temporal correlation between the two instruments remained good through June 1998, when contact with the SOHO spacecraft was lost. Until then the CDS instrument measured (33+/-5)% and (38+/-7)% (+/-1σ) higher intensity than SUMER in the Hz I 584-Å line on average for detectors A and B, respectively. Data from SUMER detector B agreed well for Mg X 609 Å and Mg X 624 Å with the CDS intensities, showing offsets of (2+/-10)% and (9+/-15)%, much less than the data of detector A with offsets of (7+/-8)% and (16+/-7)% for the two lines, respectively, relative to CDS. Finally, the intercalibration measurements after the loss and recovery of the SOHO spacecraft are analyzed. The data for observations from November 1998 to July 2000 are compared, and it is shown that, although the responses of the instruments have changed, the CDS and the SUMER still perform well, and their temporal correlation is good. Title: The SUMER spectral atlas of solar-disk features Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi, B. N.; Schühle, U.; Lemaire, P. Bibcode: 2001AIPC..598...45C Altcode: 2001sgc..conf...45C A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of the Sun between 670 Å and 1609 Å in first order of diffraction has been derived from observations obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory) [1]. The atlas contains spectra of the average quiet Sun, a coronal hole and a sunspot on disk. Different physical parameters prevalent in the bright network (BN) and in the cell interior (CI)-contributing in a distinct manner to the average quiet-Sun emission-have their imprint on the BN/CI ratio, which is also shown for the entire spectral range. With a few exceptions, all major lines are given with their identifications and wavelengths. Lines that appear in second order are superimposed on the first order spectra, but below 500 Å the responsivity of the normal-incidence optical system is very low. The spectra include emissions from atoms and ions in the temperature range 6 103 K to 2 106 K, i.e., continua and mission lines emitted from the lower chromosphere to the corona. This spectral atlas, with its broad wavelength coverage, provides a rich source of new diagnostic tools for studying the physical parameters in the chromosphere, the transition region and the corona. In particular, the wavelength range below 1100 Å as observed by SUMER represents a significant improvement over the spectra produced in the past. In view of the manifold appearance and temporal variation of the solar atmosphere it is obvious that our atlas can only be a-hopefully typical-snapshot. The spectral radiances are determined with a relative uncertainty of 0.15 to 0.30 (1σ), and the wavelength scale is accurate to typically 10 mÅ, which is the level achievable with semi-automatic processing. The SUMER solar-disk spectral atlas will be published in the near future by Curdt et al. [2]. It includes profiles of the average quiet Sun, an equatorial coronal hole, and a sunspot. As an example we show in Fig. 1 the spectral range from 1300 Å to 1342 Å with the prominent O I and C II lines. Resolved emission lines are indicated by a mark, the measured wavelength in angstrom, and the identification, if available. Marks point to line lists available in the literature, where additional information about a specific line can be found [3-7]. New lines or identifications are indicated. Lines observed in first order and in second-order of diffraction are distinguished. Only the three least-significant digits of the wavelength values are given. If available, unidentified lines are characterized by the temperature classification defined in [3] (a: Te<3 105 b: Te~3 105 c: Te~4 105 d: 6 105<Te <9 105 e: Te~1.4 106 f: Te~1.8 106). The vertical axes are scaled to spectral radiance in units of mW sr-1 m-2 Å-1 on the left the radiometric calibration for first order lines is given, on the right for second order lines. Note, that second order lines are always superimposed on a first order background. We have taken care of the type of photocathode (bare or KBr) when applying the radiometric calibration to different sections of the spectrum. Also displayed in green is the BN/CI ratio in an attempt to characterize the quiet-Sun chromospheric network structure. A pre-print of the SUMER spectral atlas and a line list is available at http://www.linmpi.mpg.de/~curdt. . Title: Wide bandgap EUV and VUV imagers for the Solar Orbiter Authors: Hochedez, Jean-François; Lemaire, Philippe; Pace, Emanuele; Schühle, Udo; Verwichte, Erwin Bibcode: 2001ESASP.493..245H Altcode: 2001sefs.work..245H No abstract at ADS Title: The SUMER spectral atlas of solar-disk features Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi, B. N.; Schühle, U.; Lemaire, P. Bibcode: 2001A&A...375..591C Altcode: A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of the Sun between 670 Å and 1609 Å in the first order of diffraction has been derived from observations obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory). The atlas contains spectra of the average quiet Sun, a coronal hole and a sunspot on the disk. Different physical parameters prevalent in the bright network (BN) and in the cell interior (CI) - contributing in a distinct manner to the average quiet-Sun emission - have their imprint on the BN/CI ratio, which is also shown for almost the entire spectral range. With a few exceptions, all major lines are given with their identifications and wavelengths. Lines that appear in second order are superimposed on the first order spectra. These lines are clearly marked in the atlas. The spectra include emissions from atoms and ions in the temperature range 6*E3 K to 2*E6 K, i.e., continua and emission lines emitted from the lower chromosphere to the corona. This spectral atlas, with its broad wavelength coverage, provides a rich source of new diagnostic tools to study the physical parameters in the chromosphere, the transition region and the corona. In particular, the wavelength range below 1100 Å as observed by SUMER represents a significant improvement over the spectra produced in the past. In view of the manifold appearance and temporal variation of the solar atmosphere, it is obvious that our atlas can only be a - hopefully typical - snapshot. Brief descriptions of the data reduction and calibration procedures are given. The spectral radiances are determined with a relative uncertainty of 0.15 to 0.30 (1sigma ) and the wavelength scale is accurate to typically 10 mÅ. The atlas is also available in a machine readable form. Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/375/591 Title: VizieR Online Data Catalog: SUMER Spectral Atlas of Solar Disk Features (Curdt+, 2001) Authors: Curdt, W.; Brekke, P.; Feldman, U.; Wilhelm, K.; Dwivedi, B. N.; Schuhle, U.; Lemaire, P. Bibcode: 2001yCat..33750591C Altcode: List of spectral lines in the wavelength range from 668Å to 1611Å identified in SUMER (Solar Ultraviolet Measurements of Emitted Radiation, spectrograph on the spacecraft SOHO) spectra of the average quiet Sun (QS), a coronal hole (CH) and a sunspot on disk (SS). Spectral lines observed in second order of diffraction which are also given here, extend the lower wavelength limit to below 500Å. For each entry we give the observed wavelengths in angstrom, the identification, the transition, the peak of spectral radiance, Lpeak, in mW/(sr*m2*Å) (incl. background), and a cross-reference to other line lists available in the literature (cf., Sect. 5.1). For second-order lines radiance entries are generally not provided, since the background separation in both orders of diffraction is a non-trivial task, which can not be automated. Only a few radiance values of strong second-order lines with negligible first-order contribution are given, which are marked by an asterisk (*). (1 data file). Title: Chromospheric Dynamics as can be Inferred from SUMER/SOHO Observations Authors: Rybák, J.; Kučera, A.; Curdt, W.; Schühle, U.; Wöhl, H. Bibcode: 2001ASSL..259..247R Altcode: 2001dysu.conf..247R Experience with the SUMER/SOHO observations of the chromospheric dynamics and the reduction of the acquired data is summarized on base of the SOHO Joint Operation Program 78 which is focused on the variability of the chromosphere and the transition region to the corona. Title: Comparison of quiet-Sun radiances measured by CDS and SUMER on SOHO Authors: Pauluhn, A.; Solanki, S. K.; Schühle, U.; Wilhelm, K.; Lang, J.; Thompson, W. T.; Rüedi, I.; Hollandt, J.; Huber, M. C. E. Bibcode: 2001SSRv...97...63P Altcode: Since the beginning of the SOHO (Solar and Heliospheric Observatory) mission an intercalibration programme was carried out which included simultaneous observations of the EUV instruments CDS (Coronal Diagnostic Spectrometer) and SUMER (Solar Ultraviolet Measurements of Emitted Radiation) of common targets on the quiet Sun. The observations in the chromospheric line of He i (584 Å) and the two coronal lines of Mg x (609 Å and 624 Å) thus cover the long period of 4 years and provide a data set highly suitable not only for instrumental comparison but also for studies of the quiet Sun's long term variability. Up to the SOHO accident, both instruments show a very good temporal correlation and stability. Even after the loss and recovery of the spacecraft, when the instruments had been exposed to extreme temperature conditions, the performance of the CDS and SUMER instruments is still good, as is the temporal correlation. However, the ratio between the efficiencies of the two instruments, which remained constant with time until the SOHO accident seems to have changed afterwards. In the coronal lines both instruments show an increase of average radiances towards the solar maximum. Title: Statistical Features of the Quiet Sun in EUV Authors: Pauluhn, A.; Solanki, S. K.; Rüedi, I.; Landi, E.; Schühle, U. Bibcode: 2001IAUS..203..416P Altcode: The frequency distribution of the extreme ultraviolet (EUV) intensities in the quiet Sun has in the past usually been modelled using two Gaussians. Here we test this and other distribution functions against observed distributions with exceptional statistics. The data were obtained in a number of spectral lines observed with two extreme ultraviolet spectrometers, CDS (Coronal Diagnostic Spectrometer) and SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on board the Solar and Heliospheric Observatory (SOHO). We show that the frequency distribution of the radiance is best modelled by a lognormal distribution or by a sum of a lognormal and a Gaussian. The fact that the radiance distribution of the quiet Sun including the network and the intranetwork is better reproduced by a single lognormal distribution function than by two Gaussians suggests that the same heating processes are acting in both types of features. The shape of the distribution function shows a clear temperature dependence. Title: Properties of Solar Polar Coronal Hole Plasmas Observed above the Limb Authors: Doschek, G. A.; Feldman, U.; Laming, J. M.; Schühle, U.; Wilhelm, K. Bibcode: 2001ApJ...546..559D Altcode: We determine the line-of-sight emission measure distribution and nonthermal motions as a function of height above the limb in the north and south polar coronal holes. These quantities are derived from extreme-ultraviolet (EUV) spectra obtained from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) spacecraft. The SUMER slit was oriented along the north-south direction for all the observations, and the spatial resolution is about 1". The spectra were obtained from a number of different types of observations in 1996. We select a group of emission lines for analysis for which, under the usual assumption of ionization equilibrium, the maximum emissivities span the temperature range from about 3×105 K up to about 1.1×106 K. We compare our results with recently published similar observations of a west limb quiet-Sun streamer region, with other coronal hole results based on SUMER spectra, and with earlier observations of the quiet Sun and coronal holes obtained from Skylab and rocket spectra. We find that the electron temperature in the polar holes increases with height above the limb, that the emission measure distribution of plasma located at line-of-sight heights less than about 60" peaks at a temperature of about 9×105 K, and that nonthermal motions sometimes, but not always, increase slightly with height above the limb. When observed, these increases level off above the limb at about 120". We speculate that the increases with height above the limb may be a manifestation of the fast solar wind. They may also be due to the reduction in transition region structures with increasing limb height. We also discuss wave heating as a cause of the line width increases. Title: Radiance of Solar Spectral Lines observed with CDS and SUMER on SOHO (CD-ROM Directory: contribs/pauluhn) Authors: Pauluhn, A.; Schühle, U.; Solanki, S. K.; Rüedi, I.; Lang, J.; Pike, C. D.; Thompson, W. T.; Huber, M. C. E. Bibcode: 2001ASPC..223..721P Altcode: 2001csss...11..721P No abstract at ADS Title: Comparison of far-ultraviolet emission lines formed in coronal holes and the quiet Sun Authors: Stucki, K.; Solanki, S. K.; Schühle, U.; Rüedi, I.; Wilhelm, K.; Stenflo, J. O.; Brković, A.; Huber, M. C. E. Bibcode: 2000A&A...363.1145S Altcode: We present an analysis of 26 far-ultraviolet emission lines belonging to 19 atoms and ions observed on both sides of the boundary of polar coronal holes as well as other quiet Sun areas along the limb. The observations were made with the SUMER instrument (Solar Ultraviolet Measurements of Emitted Radiation) onboard the Solar and Heliospheric Observatory (SOHO). We compare line intensities, shifts and widths in coronal holes with the corresponding values obtained in the quiet Sun. We find that with increasing formation temperature, spectral lines show on average an increasingly stronger blueshift in coronal holes relative to the quiet Sun at equal heliospheric angle, with the coolest lines in our sample (formation temperature ~ 104 K) indicating a small relative redshift. With respect to the rest wavelength, however, only lines formed above 5 * 105 K show blueshifts in coronal holes, which is not very different from the quiet Sun. The width of the lines is generally larger (by a few kilometers per second) inside the coronal hole. Intensity measurements clearly show the presence of the coronal hole in Ne VIII lines as well as in Fe XII, and provide evidence for a slightly enhanced emission in polar coronal holes for lines formed below 105 K. This last result is, however, less certain than the rest due to relatively poor statistics. Intensity histograms also exhibit distinct differences between coronal hole and quiet-Sun data. For cooler chromospheric lines, such as Ni II, the coronal holes display a greater spread in intensities than the quiet Sun. Transition-region lines, e.g. O IV, do not reveal such differences, while Ne VIII shows characteristics of a coronal line with lower average intensity and lower intensity spread inside holes. Title: Statistics of quiet Sun extreme ultraviolet intensities Authors: Pauluhn, A.; Solanki, S. K.; Rüedi, I.; Landi, E.; Schühle, U. Bibcode: 2000A&A...362..737P Altcode: The frequency distribution of the extreme ultraviolet (EUV) emission line intensities in the quiet Sun has in the past often been modelled using two Gaussians. This gives adequate fits to observed distributions of average statistical significance. In this paper we test this and other distribution functions against observed distributions with exceptional statistical significance. The data were obtained in a number of spectral lines observed with two extreme ultraviolet spectrometers on board the Solar and Heliospheric Observatory (SOHO). In this way, the influence of spatial resolution and other instrument-specific parameters can be identified. The observations span a period of more than two years and provide a very large data set of radiance measurements of the quiet Sun at or near solar disk centre. We show that the frequency distribution of the radiance is best modelled by a lognormal distribution. The fact that the radiance distribution of the quiet Sun including the network and the intranetwork is better reproduced by a single lognormal distribution function than by two Gaussians suggests that the same heating processes are acting in both types of features. The parameters of the lognormal fit show a clear temperature dependence, with the transition region lines exhibiting the largest skewness of the distribution and the chromospheric intensity distributions being the most symmetric. Title: On the relationship between shift and intensity of ultraviolet lines in coronal holes and the quiet Sun Authors: Stucki, K.; Solanki, S. K.; Schühle, U.; Rüedi, I. Bibcode: 2000A&A...362L..49S Altcode: We study the relationship between wavelength shifts and intensities of chromospheric, transition-region and coronal ultraviolet emission lines in polar coronal holes and in the normal quiet Sun using SUMER data. Within coronal holes almost all the lines showing the network and formed above 30 000 K show a correlation between blueshifts and brightness. This extends and supports the conclusion reached by Hassler et al. (1999) that the fast solar wind emanates from the network. In the normal quiet Sun, however, we find that only lines formed above 2-3 * 105 K show such a trend, the cooler lines being more redshifted in the network. This suggests that either there is a fundamental difference in the initial acceleration of the solar wind in coronal holes and the normal quiet Sun, or that the wavelength-shift versus brightness relationship in the quiet Sun stems from other processes or structures (loops) than in coronal holes (open field lines). Title: Radiance variations of the quiet Sun at far-ultraviolet wavelengths Authors: Schühle, U.; Wilhelm, K.; Hollandt, J.; Lemaire, P.; Pauluhn, A. Bibcode: 2000A&A...354L..71S Altcode: We have measured the radiance of quiet-Sun areas at the centre of the solar disk using the vacuum-ultraviolet telescope-spectrograph SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on the Solar and Heliospheric Observatory (SOHO). The radiances of selected emission lines have been measured from March 1996 to the present. The lines that have been observed regularly since the beginning of the SOHO mission are He i 584 Å, Mg x 609 Å and 624 Å, Ne viii 770 Å, N v 1238 Å, and the H i Lyman continuum at 880 Å. We investigate the variability of these emission lines during the solar minimum and the ascending phase of the present solar activity cycle. The transition region and coronal lines show an increasing trend of up to 100% since the sunspot minimum. The results are important for models of solar VUV variability on the basis of radiance contrast ratios of solar disk regions. Our spatially resolved images allow a separation of the network and cell areas of the quiet-Sun. Both regimes show similar variations. Title: Mid-term Radiance Variation of Far-Ultraviolet Emission Lines from Quiet-Sun Areas Authors: Schühle, U.; Hollandt, Jorg; Pauluhn, Anuschka; Wilhelm, Klaus Bibcode: 2000ESASP.463..427S Altcode: 2000sctc.proc..427S No abstract at ADS Title: Solar Irradiances of Ultraviolet Emission Lines Measured During the Minimum of Sunspot Activity in 1996 and 1997 Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.; Schuhle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Humbler, M. C. E. Bibcode: 2000PCEC...25..389W Altcode: No abstract at ADS Title: Radiometric Calibration of the Vacuum-Ultraviolet Spectrograph SUMER on the SOHO Spacecraft with the B Detector Authors: Schühle, Udo; Curdt, Werner; Hollandt, Jörg; Feldman, Uri; Lemaire, Philippe; Wilhelm, Klaus Bibcode: 2000ApOpt..39..418S Altcode: The Solar Ultraviolet Measurement of Emitted Radiation (SUMER) vacuum-ultraviolet spectrograph was calibrated in the laboratory before the integration of the instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft in 1995. During the scientific operation of the SOHO it has been possible to track the radiometric calibration of the SUMER spectrograph since March 1996 by a strategy that employs various methods to update the calibration status and improve the coverage of the spectral calibration curve. The results for the A Detector were published previously Appl. Opt. 36, 6416 (1997) . During three years of operation in space, the B detector was used for two and one-half years. We describe the characteristics of the B detector and present results of the tracking and refinement of the spectral calibration curves with it. Observations of the spectra of the stars and Leonis permit an extrapolation of the calibration curves in the range from 125 to 149.0 nm. Using a solar coronal spectrum observed above the solar disk, we can extrapolate the calibration curves by measuring emission line pairs with well-known intensity ratios. The sensitivity ratio of the two photocathode areas can be obtained by registration of many emission lines in the entire spectral range on both KBr-coated and bare parts of the detector s active surface. The results are found to be consistent with the published calibration performed in the laboratory in the wavelength range from 53 to 124 nm. We can extrapolate the calibration outside this range to 147 nm with a relative uncertainty of 30% (1 ) for wavelengths longer than 125 nm and to 46.5 nm with 50% uncertainty for the short-wavelength range below 53 nm. Title: Comparison of Transient Network Brightenings and Explosive Events in the Solar Transition Region Authors: Chae, Jongchul; Wang, Haimin; Goode, Philip R.; Fludra, Andrzej; Schühle, Udo Bibcode: 2000ApJ...528L.119C Altcode: The relation between transient network brightenings, known as blinkers, and explosive events is examined based on coordinated quiet Sun observations in the transition region line O V λ630 recorded by the Coronal Diagnostic Spectrometer (CDS), in the transition region line Si IV λ1402 recorded by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument, and in photospheric magnetograms taken by the Big Bear Solar Observatory videomagnetograph. From these observations, we find that (1) explosive events, which are traditionally defined as features with very broad UV line profiles, tend to keep away from the centers of network brightenings and are mostly located at the edges of such brightenings, (2) CDS blinkers consist of many small-scale, short-lived SUMER ``unit brightening events'' with a size of a few arcseconds and a lifetime of a few minutes, and most importantly (3) each SUMER unit brightening event is characterized by a UV line profile that is not as broad as those of explosive events, but still has significantly enhanced wings. Our results imply that, like explosive events, individual unit brightening events involve high velocities, and, hence, blinkers may have the same physical origin as explosive events. It is likely that transient network brightenings and explosive events are both due to magnetic reconnection--but with different magnetic geometries. Title: Radiance Variations of Vacuum-Ultraviolet Emission Lines of the Quiet Sun Observed with SUMER on SOHO Authors: Schuhle, U.; Pauluhn, A.; Hollandt, J.; Lemaire, P.; Wilhelm, K. Bibcode: 2000PCEC...25..429S Altcode: No abstract at ADS Title: Solar spectroradiometry with the telescope and spectrograph SUMER on the Solar and Heliospheric Observatory SOHO Authors: Wilhelm, K.; Schühle, U.; Curdt, W.; Dammasch, I. E.; Hollandt, J.; Lemaire, P.; Huber, M. C. E. Bibcode: 2000Metro..37..393W Altcode: No abstract at ADS Title: Dynamics of Chromiospheric and Transition Region Lines Observed with SOHO/SUMER and the GCT/Tenerife Authors: Muglach, K.; Fleck, B.; Schühle, U.; Stolpe, F.; Foing, B. H.; Wilhelm, K. Bibcode: 2000AdSpR..25.1731M Altcode: High-resolution spectroscopic observations of the quiet Sun have been carried out in September 1996 at the German Gregory Coudé Telescope (GCT) in Tenerife and in May 1997 with the SUMER instrument onboard SOHO. Time sequences of spectra in the visible and near infrared as well as in the ultraviolet have been taken, covering a range of heights from the solar photosphere up into the transition region. In this contribution we present the dynamical behaviour observed at the various heights in the solar atmosphere Title: Solar Ultraviolet Irradiance and Radiance Observations by SUMER on SOHO Authors: Dammasch, I. E.; Wilhelm, K.; Curdt, W.; Schühle, U. Bibcode: 1999ESASP.448.1165D Altcode: 1999ESPM....9.1165D; 1999mfsp.conf.1165D No abstract at ADS Title: Chromospheric and Transition Region Dynamics - Reasons and Consequences of the Long-period Instrumental Periodicities of SUMER/SOHO Authors: Rybák, J.; Curdt, W.; Kucera, A.; Schühle, U.; Wöhl, H. Bibcode: 1999ESASP.448..361R Altcode: 1999mfsp.conf..361R; 1999ESPM....9..361R No abstract at ADS Title: The solar ultraviolet spectrum from 1200 Å to 1560 Å: a radiometric comparison between SUMER/SOHO and SOLSTICE/UARS Authors: Wilhelm, K.; Woods, T. N.; Schühle, U.; Curdt, W.; Lemaire, P.; Rottman, G. J. Bibcode: 1999A&A...352..321W Altcode: After short descriptions of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrometer onboard SOHO (the Solar and Heliospheric Observatory) and the SOLSTICE (Solar-Stellar Irradiance Comparison Experiment) spectrometer on UARS (the Upper Atmosphere Research Satellite), a radiometric comparison is carried out of solar irradiance spectra measured by SOLSTICE and spectra derived from SUMER radiance observations of quiet-Sun regions in the wavelength range from 1200 Å to 1560 Å. The emission lines N v (lambda 1238) and C iv (lambda 1548) are considered in detail. For these lines, irradiance data are also available from full-Sun raster scans of SUMER and deviations of less than 15% are found between SOLSTICE and SUMER results - well within the combined uncertainty margins. Title: Relationship between Line Shift and Intensity Inside Coronal Holes Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Schüehle, U. Bibcode: 1999ESASP.446..633S Altcode: 1999soho....8..633S We analyse SUMER spectra of a group of lines belonging to chromospheric, transition region and coronal ions obtained on both sides of the boundary of polar coronal holes as well as at other locations along the limb. We study the relationship between line shifts and intensities in coronal holes and compare to values obtained in the quiet Sun. We find that within coronal holes, a trend can be detected in some transition region lines, like O V and N V, in the sense that the lines are more strongly blueshifted in brighter regions. This is in agreement with the conclusion reached by Hassler et al. (1999, Science 283, 810-813) that the fast solar wind emanates from the network. Furthermore, a correlation of line shifts of ions formed at higher temperatures (Ne VIII, Fe XII) with intensities of lines showing network structures (Si I, N III) is presented. Title: The SUMER EUV Atlas in the Spectral Range 670 A - 1498 A Authors: Curdt, W.; Brekke, P.; Schühle, U.; Wilhelm, K.; Dwivedi, B. N. Bibcode: 1999ESASP.446..251C Altcode: 1999soho....8..251C An extreme ultraviolet spectral atlas between 660 and 1600 A (first order) of a quiet Sun, a coronal hole, and a Sun spot region has been derived from observations with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on SOHO. More than 1000 emission lines are given with the best available identification. The spectra are radiometrically calibrated. Lines in second order are superimposed on this spectrum. The spectral scans include emissions from atoms and ions in the temperature range from 6 000 to 2000 000 K, i.e., continua and emission lines emitted from the lower chromosphere to the corona. This broad wavelength coverage provides an important new diagnostic tool for studying the essential physical parameters throughout the upper solar atmosphere. In particular, the wavelength range shortward of 1100 A as observed by SUMER represents a significant improvement over the spectra produced in the past. A brief description of the data reduction and calibration procedures is given. The absolute intensities are determined with an uncertainty of better than +- 15% in most of the range presented, and the wavelength scale is accurate to better than 0.01 A. The atlas will also be available in machine readable form. Title: Molecular Hydrogen Lines Observed with SUMER in the Spectrum of a Sunspot Authors: Schüehle, U.; Brown, C. M.; Curdt, W.; Feldman, U. Bibcode: 1999ESASP.446..617S Altcode: 1999soho....8..617S No abstract at ADS Title: Chromospheric And Transition Region Dynamics - Reasons and Consequences of the Short Period Instrumental Periodicities of SOHO/SUMER Authors: Rybak, Jan; Curdt, Werner; Kučera, Ales; Schüehle, Udo; Wöehl, Hubertus Bibcode: 1999ESASP.446..579R Altcode: 1999soho....8..579R The instrumentally caused oscillations of the spectral lines intensity and velocity, determined with the SUMER spectrometer onboard SoHO, are presented. On examples of two long-term measurements of O I, C II and O VI lines, it is shown that the reason of this instrumental effect was the insufficient precision of the solar rotation compensation of the spectrometer slit position. In both observational runs the standard rotation compensation procedure, performed on-line by the instrument, was selected for the long-term observations. The minor periodical motion of the slit position on the solar disk was taking place during such observations and this effect produced the regular changes of the measured line intensities and velocities. The significant enhancements of the oscillations amplitudes around the frequency 2.56 mHz and its harmonics were detected in the cases of observations, performed at the disk center. Unfortunately, these frequencies are just in the range of the typical oscillations determined till now in the upper solar atmosphere ! Consequences of this instrumental effect for SUMER measurements of the chromospheric and transition region dynamics are discussed. Procedures how to exclude the effect from the data post-facto as well as how to modify the future SUMER oscillations measurements in order to avoid the effect are proposed Title: Coordinated observations between SOHO/SUMER and ground during the 1998 total eclipse: Non-thermal line broadenings and electron densities in a polar coronal hole Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy, S.; Schühle, U. Bibcode: 1999AIPC..471..285P Altcode: 1999sowi.conf..285P Alfvén waves represent one of the most prominent ways of heating the solar corona and accelerating the solar wind. One of their signatures is to broaden the spectral lines in excess of their thermal width. Here we aim to combine observations of non-thermal broadenings measured by SUMER in OVI (1037.6 Å) line and electronic densities derived from white-light observations during the 1998 total eclipse. After checking the validity of the frequently-used assumption of equal ion and electron temperatures, we compute the variation of the non-thermal velocity as a function of height in an interplume region within the south polar coronal hole. Title: Properties of Quiet-Sun Coronal Plasmas at Distances of 1.03<=Rsolar<=1.50 along the Solar Equatorial Plane Authors: Feldman, U.; Doschek, G. A.; Schühle, U.; Wilhelm, K. Bibcode: 1999ApJ...518..500F Altcode: We determine the physical properties, i.e., electron temperature, density, line-of-sight emission measure, and element-abundance variation with height, in the Sun's equatorial west limb streamer region from extreme-ultraviolet (EUV) spectra recorded by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) spacecraft. The spectra were recorded on 1996 November 21-22 during a special ``roll'' maneuver in which the SUMER slit was oriented in the east-west direction. Because the SUMER spectrometer is stigmatic along the slit length, the spectra are spatially resolved in the east-west direction. The spectra we discuss cover an effective distance range outside the west limb from 1.03 to 1.50 solar radii (Rsolar) the maximum spatial resolution is 1''. We select a group of emission lines for analysis that under the usual ionization equilibrium assumption span the temperature range from 3×105 up to 2×106 K. However, we note that above the limb a major fraction of a line intensity may arise at a temperature that is far from the temperature of maximum emitting efficiency in ionization equilibrium. In this paper we assume ionization equilibrium in deriving plasma parameters. Readers can redo our analysis without this assumption if desired, because the line intensities we present in this paper are simply the measured photon production rates in the lines. Assuming ionization equilibrium, we determine the electron temperature, electron density, line-of-sight emission measure, and abundance variation with height above the limb from the line intensities and line intensity ratios. The spatial resolution has allowed us to detect an apparent element-abundance variation as a function of height above the west limb that is strong evidence for gravitational settling of ``heavy'' elements. Title: Coronal Hole Properties Observed with SUMER Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Stenflo, J. O.; Brković , A.; Schühle, U.; Wilhelm, K.; Huber, M. C. E. Bibcode: 1999SSRv...87..315S Altcode: We analyze SUMER spectra of 14 lines belonging to 12 ions, obtained on both sides of the boundary of polar coronal holes as well as at other locations along the limb. We compare line intensities, shifts and widths in coronal holes with values obtained in the quiet Sun. We find that with increasing formation temperature, spectral lines show an increasingly stronger blueshift in coronal holes relative to the quiet Sun at an equal heliospheric angle. The width of the lines is generally larger (by a few km/s) inside the coronal hole. Intensity measurements show the presence of the coronal hole in Ne VIII lines as well as in Fe XII, with evidence for a slightly enhanced emission in polar coronal holes for lines formed below 105 K. Title: Coronal Holes Versus Normal Quiet Sun Observed with SUMER Authors: Stucki, K.; Solanki, S. K.; Rüedi, I.; Stenflo, J. O.; Brković, A.; Schühle, U.; Wilhelm, K.; Huber, M. C. E. Bibcode: 1999Ap&SS.264...53S Altcode: 1998Ap&SS.264...53S We present a preliminary analysis of spectral lines obtained with the SUMER instrument (Solar Ultraviolet Measurements of Emitted Radiation) onboard the Solar and Heliospheric Observatory (SOHO), as observed during three observing campaigns. From the 70 observed spectral lines, we selected 12, representing 9 ions or atoms, in order to analyse line intensities, shifts and widths in polar coronal holes as well as in the normal quiet Sun. We find that coronal lines show a distinct blueshift in coronal holes relative to the quiet Sun at equal heliospheric angle, while there is no evidence for such a shift for lines formed at temperatures below 10^5 K. The widths of lines formed at temperatures above 3 - 10^4 K are slightly increased inside the coronal hole, but unaffected for lower temperatures. Intensity measurements clearly show the center-to-limb variation, as well as an intensity diminution inside the coronal hole for lines formed above approximately 10^5 K. Title: Outflow Velocities at the Base of a Polar Coronal Hole During the 1998 Total Eclipse Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy, S.; Schühle, U. Bibcode: 1999SSRv...87..291P Altcode: Polar coronal holes represent the most convincing site from which the high-speed solar wind originates. Here we report high-accuracy Doppler shifts measured in the O VI (1037.6 Å) line obtained by SUMER on SOHO inside an interplume region within the south polar coronal hole. We infer limits on the outflow velocity and draw hints about the flow geometry. Title: Signatures of Coronal Hole Spectra Between 660 Å and 1460 Å Measured with SUMER on SOHO Authors: Schühle, U.; Curdt, W.; Wilhelm, K.; Solanki, S. K.; Stucki, K. Bibcode: 1999SSRv...87..299S Altcode: Spectra of the northern polar coronal hole measured with the SUMER spectrometer on SOHO on 25 October 1996 are analyzed. We present spectra taken at locations on the solar disk where part of the spectrometer slit intersects a polar coronal hole region and an area of brighter emission from outside of the coronal hole area. By comparing the line intensities between the parts of the spectrum taken inside the "dark" area of the coronal holes and the brighter regions, we work out the signatures of the specific coronal hole in the chromosphere, transition region and lower corona. We find that emissions of neutral atom lines, of which there are many in the spectrum of SUMER, show no difference between the coronal hole and the bright boundary areas, whereas all ionized species show strong intensity enhancements, including the continuum emissions of carbon and hydrogen. These enhancements are larger than in normal quiet Sun areas. Title: Solar irradiances of UV and EUV lines during the minimum of the sunspot activity in 1996 Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.; Schühle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Huber, M. C. E. Bibcode: 1999AdSpR..24..229W Altcode: Full Sun observations in UV and EUV emission lines were performed by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric preflight calibration of SUMER is traceable to a primary radiometric source standard - the electron storage ring BESSY. Based on this calibration and on its inflight refinements, the irradiance values at SOHO have been obtained for the lines He i (λ584.33), O v (λ629.74), Ne viii (λ770.41), S v (λ786.47), O iv (λ787.72), S vi (λλ933.39, 944.52), H i Ly ɛ (λ937.80), C iii (λ977.04), N v (λ1238.81), Si i (λ1256.52), and C iv (λ1548.20), and the continuum near 1549 Å. In this contribution, we compare our measurements with other recent irradiance determinations and discuss, in particular, the observations in the C iv line. Title: The Electron Pressure in the Solar Lower Transition Region Determined from O V and Si III Density-sensitive Line Ratios Authors: Doschek, G. A.; Feldman, U.; Laming, J. M.; Warren, H. P.; Schüle, U.; Wilhelm, K. Bibcode: 1998ApJ...507..991D Altcode: We determine the electron density at the temperatures of formation of O+4 and Si+2 ions, which are about 2.5 × 105 and 3.2 × 104 K in ionization equilibrium, respectively. These temperatures occur in the lower transition region of the Sun's atmosphere and allow a test of the often invoked assumption of constant pressure in quiet-Sun models. The O+4 density is determined from a density-sensitive spectroscopic O V line ratio involving 2s2p3P-2p23P transitions that fall near 760 Å. The Si+2 density is determined from a density-sensitive Si III line ratio within the 3s3p3P-3p23P multiplet near 1300 Å. There are few available line ratio techniques for determining the density and hence electron pressure in the quiet-Sun and coronal hole transition regions using lines emitted by the same ion, and determining these quantities is the principal motivation for this work. The spectra used in our analysis were obtained from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) experiment on the Solar and Heliospheric Observatory (SOHO). We determine the electron density and pressure in typical quiet-Sun/coronal hole regions, and densities in active region brightenings and in an explosive event. Our O V and Si III results indicate that constant pressure is valid or nearly valid in quiet-Sun lower transition regions, although there are complications arising from the weakness of a key Si III line in the quiet-Sun disk spectra. We also discuss our results in light of other density measurements and theories regarding the structure and heating of the transition region. Title: Coronal Composition above the Solar Equator and the North Pole as Determined from Spectra Acquired by the SUMER Instrument on SOHO Authors: Feldman, U.; Schühle, U.; Widing, K. G.; Laming, J. M. Bibcode: 1998ApJ...505..999F Altcode: Using spectra obtained by the SUMER instrument on the Solar and Heliospheric Observatory (SOHO) we have determined the composition of the bulk of the coronal plasma in the vicinity of the solar surface over a polar coronal hole and an equatorial region. Our measurements show that although low first ionization potential (FIP) elements are enriched by about a factor of 4 in the corona above the quiet equatorial region, little or no enrichment exists above the north polar coronal hole. These observations are in good agreement with the Ulysses in situ observations in both fast speed and slow speed winds. Title: SUMER Measurements of Nonthermal Motions: Constraints on Coronal Heating Mechanisms Authors: Chae, Jongchul; Schühle, Udo; Lemaire, Philippe Bibcode: 1998ApJ...505..957C Altcode: We have determined nonthermal velocities in the quiet Sun at temperatures between 104 K and 2 × 106 K by measuring the widths of a number of EUV and far-ultraviolet (FUV) lines taken with SUMER on board the SOHO spacecraft. The broadenings owing to the SUMER instrument and the finite opacity in each line have been carefully examined. The nonthermal velocity at temperatures below 2 × 104 K is smaller than 10 km s-1. The velocity increases with temperature, reaches a peak value of 30 km s-1 around 3 × 105 K, and then decreases with the temperature. The coronal nonthermal velocity is about 20 km s-1. There exists a strong correlation between intensity and nonthermal velocity at temperatures 2 × 104-1 × 105 K. The correlation at higher temperatures weakens as temperature increases. Furthermore, there is a spatial correlation between the nonthermal velocities inferred from a set of any two lines with temperatures below 2 × 105 K. Neither significant center-to-limb variation nor meaningful dependence on the integration time was found from the measured nonthermal velocities. We have discovered the existence of high-velocity components in the observed S VI λ933.4 line profiles. The average nonthermal velocity and intensity fraction of this S VI line high-velocity component are found to be 55 km s-1 and 0.25, respectively.

Observational characteristics of nonthermal motions carry some problems that should be solved when interpreting observed nonthermal motions in terms of either unresolved loop flows or Alfvén waves. The isotropic and very small scale nature of the observed nonthermal motions appears to be suited to the MHD turbulence interpretation of nonthermal motions. The turbulent heating rates inferred from the measured nonthermal motions can account for the radiative loss throughout the transition region and corona if the nonthermal motions are truly turbulent motions whose mechanical energy is injected at a scale of 1000 km (Kolmogorov-type turbulence) or 15 km (Kraichnan-type turbulence). The existence of high-velocity components at temperatures 6 × 104-2 × 105 K appears as observational evidence supporting nanoflare heating at these temperatures. Title: Chromospheric Upflow Events Associated with Transition Region Explosive Events Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip R.; Schühle, Udo Bibcode: 1998ApJ...504L.123C Altcode: Transition region explosive events are considered to be a manifestation of small-scale magnetic reconnection ubiquitously occurring--even in the quiet Sun. In this paper, we report a close association between transition region explosive events and chromospheric upflow events seen in Hα. From a comparison of the Big Bear Solar Observatory (BBSO) Hα spectrograph data and the Solar and Heliospheric Observatory (SOHO) / Solar Ultraviolet Measurements of Emitted Radiation (SUMER) data, we found a succession of chromospheric upflow events at sites where repeated explosive events occurred. Individual chromospheric events appear as compact dark features that are best visible in Hα-0.5 Å and that have a size of 2"-3" and a lifetime of 1-2 minutes. They are characterized by an upward motion of 15-30 km s-1, a temperature of 104 K, a mass density of 1×10-13 g, and a nonthermal velocity less than 10 km s-1. Unlike spicules, which display descending motion following their ascending phase, these upflow events are not followed by noticeable redshifts. ``Hα jets'' at -1.0 Å studied by Wang et al. appear to be a special case of this kind of chromospheric upflow event. The physical characteristics of chromospheric upflow events and their close association with transition region explosive events suggest that chromospheric upflow events may be the manifestation of cool plasma material flowing into magnetically diffusive regions, while explosive events represent hot plasma material flowing out of the same regions. Title: The Si/Ne Abundance Ratio in Polar Coronal Hole and Quiet-Sun Coronal Regions Authors: Doschek, G. A.; Laming, J. M.; Feldman, U.; Wilhelm, K.; Lemaire, P.; Schühle, U.; Hassler, D. M. Bibcode: 1998ApJ...504..573D Altcode: Using spectra obtained from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory (SOHO) spacecraft, we determine the Si/Ne abundance ratio in diffuse, interplume polar coronal hole regions, as well as the ratio relative to quiet-Sun coronal regions. Ne has the second highest first ionization potential (FIP) of solar abundant elements, and Si is a low-FIP element. Thus the Si/Ne ratio is a sensitive indicator of abundance variations due to the FIP effect. We develop new spectroscopic diagnostics for the determination of the Si/Ne abundance ratio. Assuming ionization equilibrium, we find that the Si/Ne abundance ratio in interplume polar coronal hole regions is about a factor of 2 greater than the photospheric value and is close to or the same as in coronal quiet-Sun regions. This result pertains to the electron temperature range 5-8 × 105 K. However, the combined atomic physics, instrumental, and statistical uncertainty in this result is about a factor of 2, and therefore this observed enhancement is consistent with no enhancement in the polar hole abundances. Nevertheless, our results follow the same trend, i.e., a greater than photospheric abundance ratio of low-FIP elements in the corona relative to high-FIP elements, as found from other abundance measurements in the corona that involve different atomic physics and different instruments. Therefore we feel that our results reflect an actual abundance enhancement, despite being within an uncertainty level bar that encompasses photospheric abundances. We also examine the Ne/Mg abundance ratio over a 24.5 hr observation and find no significant abundance variations. (Mg is a low-FIP element.) Thus, no large transient abundance variations appear to occur on timescales shorter than about a day, although this result is based on only one observation. From lines of Mg VII, Mg VIII, Mg IX, and Mg X we find that the electron temperature along the line of sight increases with height above the limb over the polar coronal holes, as has been previously reported. We determine the emission measure distribution as a function of height from Mg VII, Mg VIII, and Mg X lines. We determine average temperatures along the line of sight over the polar holes from Ne VIII/Ne VII, Mg VIII/Mg VII, and Si VIII/Si VII line ratios. We also discuss the temperature properties of the coronal hole and quiet-Sun regions using forbidden lines of Fe X and Fe XI. We comment on the possibility that ionization equilibrium is not valid in polar coronal hole regions, a possible scenario in light of recent observations that show outflows in coronal holes beginning at about the temperature of formation of Ne VIII. Title: High-Temperature Lines in SUMER Spectra Recorded Above a Bright Solar Active Region Authors: Feldman, U.; Curdt, W.; Doschek, G. A.; Schühle, U.; Wilhelm, K.; Lemaire, P. Bibcode: 1998ApJ...503..467F Altcode: We identify spectral lines emitted by solar abundant elements due primarily to transitions within the 2s22pk and 3s23pk (where k = 1, 5) ground configurations of ions that are formed in ionization equilibrium between 2 × 106 and 8 × 106 K. The transitions were identified in spectra of a bright active region recorded 1997 September 6, by the Solar Ultraviolet Measurements of Emitted Radiation Spectrometer (SUMER) flown on the Solar and Heliospheric Observatory (SOHO). Some of these lines provide useful plasma diagnostic tools for measuring the physical conditions in the solar corona. Title: Evidence in Support of the ``Nanoflare'' Picture of Coronal Heating from SUMER Data Authors: Judge, P. G.; Hansteen, V.; Wikstøl, Ø.; Wilhelm, K.; Schühle, U.; Moran, T. Bibcode: 1998ApJ...502..981J Altcode: We study high signal-to-noise profiles of O IV emission lines obtained using the SUMER instrument on SOHO. Data for the quiet Sun obtained close to the disk center and at the solar limb were acquired. After careful data processing in which disk data were analyzed differentially against limb data, we find a systematic correlation between a density-sensitive emission-line ratio and Doppler shift across the same emission-line profiles. While unidentified blended lines cannot be completely discounted, the data suggest that the effects of such blends are small. Based on theoretical results in an earlier paper, we argue that if wave motions are responsible for the observed behavior, then the data reveal evidence for compressive waves propagating downward from the corona to the chromosphere. This analysis naturally lends support to the dominance of the ``nanoflare'' mechanism for coronal heating over other theories that invoke upward wave propagation, but other mechanisms capable of generating downward-propagating waves cannot be discounted. If, instead, steady flows are the cause of the observed behavior, such as return flows from spicules, then they must be such that the density is higher in the downflowing plasma. While these particular data do not allow us to discriminate between waves or steady flows, additional data from SOHO should be able to address this problem. This work required and achieved very accurate wavelength calibrations (better than 1/5 of a pixel on the detectors), taking SUMER close to its observational capabilities. We therefore present the elements of the analysis and calibration of SUMER data that may be of interest to other users. Title: Solar irradiances and radiances of UV and EUV lines during the minimum of sunspot activity in 1996 Authors: Wilhelm, K.; Lemaire, P.; Dammasch, I. E.; Hollandt, J.; Schuehle, U.; Curdt, W.; Kucera, T.; Hassler, D. M.; Huber, M. C. E. Bibcode: 1998A&A...334..685W Altcode: Full Sun observations in UV and EUV emission lines were performed by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric pre-flight calibration of SUMER is traceable to a primary radiometric source standard - the electron storage ring BESSY. Based on this calibration, the irradiance values at SOHO and at 1 AU have been obtained for the lines He i (lambda 584.33 { Angstroms}), O v (lambda 629.74 { Angstroms}), Ne viii (lambda 770.41 { Angstroms}), S v (lambda 786.47 { Angstroms}), O iv (lambda 787.72 { Angstroms}), S vi (lambda lambda 933.39, 944.52 { Angstroms}), H i Ly epsilon (lambda 937.80 { Angstroms}), C iii (lambda 977.04 { Angstroms}), N v (lambda 1238.81 { Angstroms}), Si i (lambda 1256.52 { Angstroms}), and C iv (lambda 1548.20 { Angstroms}). The spatially resolved measurements allowed good estimates to be made of the active region contributions to the irradiance of the quiet Sun. The centre-to-limb radiance variations of these lines have also been obtained from these measurements. For quiet solar conditions, a radiance spectrum was determined for wavelengths from 800 { Angstroms} to 1500 { Angstroms} near the centre of the solar disk. Title: Solar H i Lyman alpha full disk profile obtained with the SUMER/SOHO spectrometer Authors: Lemaire, P.; Emerich, C.; Curdt, W.; Schuehle, U.; Wilhelm, K. Bibcode: 1998A&A...334.1095L Altcode: An uncalibrated solar hydrogen Lyman alpha profile was obtained with the use of the spectrometer on SOHO. The collection of the light scattered by the telescope permitted to average the profile over the full solar disk. The profile taken at the L1 Sun-Earth Lagrangian position is free of the central geocoronal absorption. Then, taking advantage of the absolute flux measured by the SOLSTICE/UARS spectrometer, an absolute line profile intensity is derived, and is compared with previous observations at minimum solar activity. Title: Photospheric Magnetic Field Changes Associated with Transition Region Explosive Events Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip R.; Schühle, Udo Bibcode: 1998ApJ...497L.109C Altcode: From a comparison of the Solar and Heliospheric Observatory SUMER spectral data and a time series of Big Bear Solar Observatory magnetograms, we present observational clues to the physical origin of transition region explosive events. First, explosive events rarely occur in the interior of strong magnetic flux concentrations but rather are preferentially found in regions with weak and mixed polarity fluxes that display magnetic neutral lines. Second, the majority of explosive events happen during the ``cancellation'' of photospheric magnetic flux. Third, there is a strong tendency for explosive events to occur repeatedly, as bursts, while local photospheric magnetic flux continuously decreases because of cancellation. These results strongly support the idea that transition region explosive events are a manifestation of magnetic reconnection occurring in the quiet Sun. Furthermore, one may infer from the third result that the explosive events represent repetitive fast magnetic reconnections in the transition region, which are initiated by slow magnetic reconnections occurring beneath. Title: The Magnetic Reconnection Explorer (MAGREX) Authors: Schühle, U.; Antionchos, S. K.; Barbee, T. W., Jr.; Bixler, J. V.; Brown, C. M.; Carter, P. H., II; Curdt, W.; Davila, J. M.; Doschek, G.; Feldman, U.; Goldstein, W. H.; Kordas, J.; Lemaire, P.; Mariska, J. T.; Marsch, E.; Moses, J. D.; Seely, J. F.; Wilhelm, K.; Woods, T. N. Bibcode: 1998ESASP.417..289S Altcode: 1998cesh.conf..289S No abstract at ADS Title: Oscillations in Chromosphere and Transition Region Based on SUMER Measurements Authors: Kucera, A.; Curdt, W.; Rybák, J.; Schühle, U.; Wöhl, H. Bibcode: 1998ASPC..155..351K Altcode: 1998sasp.conf..351K No abstract at ADS Title: Solar Radiometry with the Telescope and Vaccum-Ultraviolet Spectrometer Sumer on the Solar and Heliospheric Observatory (SOHO) Authors: Hollandt, J.; Schuhle, U.; Curdt, W.; Dammasch, I. E.; Lamaire, P.; Wihelm, K. Bibcode: 1998Metro..35..671H Altcode: No abstract at ADS Title: VLA-SOHO Observations of Evolving Coronal Structures on the Sun Authors: Willson, R. F.; Lang, K. R.; Thompson, B.; Schuehle, U.; Zarro, D. M. Bibcode: 1998ASPC..154..727W Altcode: 1998csss...10..727W Very Large Array (VLA) observations at 3.5, 6.2, and 91.6 cm wavelength have been combined with EUV spectroheliograms from the Solar and Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS) and Extreme Ultraviolet Telescope (EIT) to study evolving sources in the transition region and corona above a solar active region. In some cases, transient events, lasting minutes to tens of minutes, were observed at both radio and EUV wavelengths, while other events were detected in only one spectral domain. The combined data sets suggest that the EUV-associated microwave sources are produced by thermal gyroresonance or nonthermal gyrosynchrotron radiation, primarily in regions of high magnetic field strength near sunspots. Observations at 91.6 cm also show the sudden appearance of a low-lying, nonthermal source in the low corona around the time that cool, outwardly-propagating plasma was detected by the SOHO/EIT. Title: Observations of the solar atmosphere from the Solar and Heliospheric Observatory (SOHO). Authors: Schühle, U. Bibcode: 1997JXST....7..249S Altcode: The Solar and Heliospheric Observatory (SOHO) spacecraft was launched on December 2, 1995, into a halo orbit around the first Lagrangian Point L1 between Sun and Earth, carrying into space a payload of twelve Sun observing instruments. Among them is a set of four complementary telescope/spectrometers to study phenomena and dynamics of the Sun's atmosphere in the far or extreme ultraviolet: The Extreme-Ultraviolet Imaging Telescope (EIT), the Coronal Diagnostic Spectrometer (CDS), the Solar Ultraviolet Measurements of Emitted Radiation (SUMER), and the Ultraviolet Coronagraph Spectrometer (UVCS). The spectral coverage of these instruments, which extents from 151 to 1610 Å, allows remote sensing investigations of the solar atmosphere by means of spectroscopic and imaging techniques with a spatial resolution down to 1 arcsec. Each one of these instruments by itself is a technological achievement making use of normal incidence, grazing incidence, or multilayer optical techniques to cover the appropriate spectral ranges for each scientific objective. Many of the plasma diagnostic studies have been carried out during the first months of the mission, and this contribution will give an overview of the capabilities of each instrument and the types of observations being made by individual and joint operations. Title: The solar disk spectrum between 660 and 1175 Anstroms (first order) obtained by SUMER on SOHO Authors: Curdt, W.; Feldman, U.; Laming, J. M.; Wilhelm, K.; Schuehle, U.; Lemaire, P. Bibcode: 1997A&AS..126..281C Altcode: SUMER -- Solar Ultraviolet Measurements of Emitted Radiation -- onboard of SOHO -- Solar and Heliospheric Observatory -- obtained its first spectrum on January 25, 1996 near the north polar limb. The range from 660 Angstroms to 1175 Angstroms which has never before been observed with such a good spectral resolution contains a wealth of spectroscopic details. Identification of about 400 lines in this spectral range is given. We list the wavelengths of identified transitions and provide their absolute peak intensities. General spectral features of the most abundant elements H, He, C, N, O, Ne, Mg, Si, S, Ar, and Fe are described. In this spectral range many density- and temperature-sensitive line pairs are found. It is shown in examples how they can be used as diagnostic tools. Table 1 and Fig.nearlimb are also available in digital form at the CDS via anonymous ftp to cdsarc.u-strasbg. fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Title: The Off-Limb Behaviour of the Solar Transition Region FIP Effect Authors: Laming, J. M.; Feldman, U.; Drake, J. J.; Schuhle, U.; Curdt, W.; Wilhelm, K.; Lemaire, P. Bibcode: 1997AAS...191.7301L Altcode: 1997BAAS...29.1320L We investigate the behaviour of the solar FIP effect (the abundance enhancement of elements with first ionization potential < 10 eV by factor of 3-4 in the corona with respect to photospheric values) with height above the limb in a region of diffuse quiet corona observed by the SUMER instrument on SOHO. Line ratios formed at log T > 5.8 show coronal abundances for all heights. Line ratios formed at lower temperatures are consistent with coronal abundances well off the limb, with the apparent magnitude of the FIP enhancement decreasing by a factor of 1.5 - 2 as one approaches the solar limb. Thus our observations support a spatial variation in the quiet sun transition region FIP effect inferred previously from studies of the full disk solar spectrum (Laming, Drake, & Widing 1995, ApJ, 443, 416 and references therein). This result adds to the probability that emission from the solar disk transition region and corona originates from qualitatively different structures for values of log T {<atop >} 5.8, having different FIP effects. Title: Sonnenradiometrie mit SUMER auf SOHO. Authors: Hollandt, J.; Curdt, W.; Schühle, U.; Wilhelm, K. Bibcode: 1997PhyBl..53.1101H Altcode: 1997PhB....53.1101H No abstract at ADS Title: A Coronal Spectrum in the 500--1610 Angstrom Wavelength Range Recorded at a Height of 21,000 Kilometers above the West Solar Limb by the SUMER Instrument on Solar and Heliospheric Observatory Authors: Feldman, U.; Behring, W. E.; Curdt, W.; Schühle, U.; Wilhelm, K.; Lemaire, P.; Moran, T. M. Bibcode: 1997ApJS..113..195F Altcode: We present a solar coronal spectrum recorded by the extreme UV spectrometer SUMER on the Solar and Heliospheric Observatory. The spectrum was taken between 21:28 UT on 1996 June 25 and 02:47 UT on 1996 June 26, at a height of 21,000 km above the west equatorial limb with the slit oriented in the north-south direction. At the time of the observations the Sun was rather quiet, and the west limb appeared ``devoid of any activity.'' The spectrum, which covers the 500-1610 Å wavelength range, originates from plasmas with temperatures ranging between 1.5 × 104 and 1.5 × 106 K. Identification of lines originating from different temperature regimes is facilitated by the appearance of their intensity along the 300" long slit.

Well over 800 lines have been found, many of which were not previously observed. We present the entire spectrum and discuss line identifications. A table of the wavelengths of lines observed, with their identifications and peak intensities, is provided. Although we have identified lines previously detected in laboratory plasmas and a number of new lines not previously observed, over 40% of the SUMER lines remain unidentified. Among the newly detected lines, some have a potential as plasma density diagnostics. Title: Observations of Polar Plumes with the SUMER Instrument on SOHO Authors: Hassler, D. M.; Wilhelm, K.; Lemaire, P.; Schühle, U. Bibcode: 1997SoPh..175..375H Altcode: We present new observations of O vi 1032 Å line profiles in polar plumes, and inter-plume regions, on the disk and above the limb in the north coronal hole obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on the SOHO (Solar and Heliospheric Observatory) spacecraft. On 22 May 1996, a 5 x 5 arc min spectroheliogram was scanned above the north polar coronal hole with the entrance slit extending from 1.03 to 1.33 solar radii with 1.5 arc sec spatial resolution and ≈ 0.044 Å per pixel spectral resolution in the wavelength range 1020-1040 Å. Detailed plume structure in O vi 1032 Å can be seen extending beyond 1.3 solar radii, with intensities in the plume regions 10-50% brighter, but line widths 10-15% narrower, than the inter-plume regions. Possible explanations for this observed anti-correlation between line width and intensity in the plume and inter-plume regions are discussed. We conclude that the source of the high-speed solar wind may not be polar plumes, but the inter-plume lanes associated with open magnetic field regions of the chromospheric network. Title: Laboratory Identification of Temperature Diagnostic Si VII and S IX Lines Present in the Solar Coronal Spectra Measured by SUMER/SOHO Authors: Kink, I.; Jupén, C.; Engström, L.; Feldman, U.; Laming, J. M.; Schühle, U. Bibcode: 1997ApJ...487..956K Altcode: The solar coronal spectrum between 500 and 1610 Å and at a height of 21,000 km above the west equatorial limb has recently been recorded by the SUMER instrument on SOHO. Using laboratory spectra obtained with the beam-foil technique, we report the identification of 32 lines observed in this spectrum as 2s22p33s-2s22p33p and 2s22p33p-2s22p33d transitions in Si VII and S IX. Theoretical gA-values and branching ratios for the observed lines, obtained from semiempirical configuration interaction calculations, are also presented. Intensity ratios between the 2s22p4 3P1-2s22p4 1S0 forbidden transition and transition from the newly identified high-excitation lines that appear in the same wavelength range are temperature sensitive. Calculations of the intensity ratios between the forbidden line and the high-excitation lines for three temperatures are presented. A comparison between the calculations and some of the SUMER observations is provided. Title: Radiometric calibration of SUMER: refinement of the laboratory results under operational conditions on SOHO Authors: Wilhelm, Klaus; Lemaire, Philippe; Feldman, Uri; Hollandt, Jörg; Schühle, Udo; Curdt, Werner Bibcode: 1997ApOpt..36.6416W Altcode: No abstract at ADS Title: Electron Density Diagnostics for the Solar Upper Atmosphere from Spectra Obtained by SUMER/SOHO Authors: Laming, J. M.; Feldman, U.; Schühle, U.; Lemaire, P.; Curdt, W.; Wilhelm, K. Bibcode: 1997ApJ...485..911L Altcode: We evaluate the electron density in various solar regions above the limb observed by the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) instrument on SOHO. We find in general good agreement among line ratios from Be-, B-, N-, and Mg-like ions, giving densities of order 108 cm-3. Title: Turbulent Velocities and Ion Temperatures in the Solar Corona Obtained from SUMER Line Widths Authors: Seely, J. F.; Feldman, U.; Schühle, U.; Wilhelm, K.; Curdt, W.; Lemaire, P. Bibcode: 1997ApJ...484L..87S Altcode: Turbulent plasma velocities and ion temperatures were determined from the line widths recorded by the Solar Ultraviolet Measurements of Emitted Radiation instrument on the Solar and Heliospheric Observatory spacecraft. From the widths of the lines of five light elements (Ne, Na, Mg, Si, and S) and a heavy element (Fe), it was possible to determine the contributions of turbulent plasma motion and ion thermal motion to the line widths. The results indicated that the turbulent velocity was approximately 22 km s-1 at 30" above the limb and decreased to less than 10 km s-1 at 109" and 209" above the limb. At 30" above the limb, the ion temperatures of the hotter lines were comparable to the electron temperatures for ionization equilibrium. The ion temperatures of the cooler lines were higher than the ionization equilibrium temperatures; at 109" and 209" above the limb, the ion temperatures were at least a factor of 2.5 higher than the ionization equilibrium temperatures. Title: Electron Densities in the Solar Polar Coronal Holes from Density-Sensitive Line Ratios of Si VIII and S X Authors: Doschek, G. A.; Warren, H. P.; Laming, J. M.; Mariska, J. T.; Wilhelm, K.; Lemaire, P.; Schühle, U.; Moran, T. G. Bibcode: 1997ApJ...482L.109D Altcode: We derive electron densities as a function of height in the north and south polar coronal holes from a forbidden spectral line ratio of Si VIII. Si VIII is produced at about 8 × 105 K in ionization equilibrium. We also derive densities from a similar line ratio of S X (1.3 × 106 K). The spectra were obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer flown on the Solar and Heliospheric Observatory spacecraft. In addition to the primary mechanism of electron impact excitation, the derivation of theoretical level populations for Si VIII and S X includes both proton and resonance capture excitation. We compare the coronal hole results to quiet-Sun coronal measurements obtained outside the east and west limbs. We find for distances of a few arcseconds outside the solar limb that the average line-of-sight electron densities in the coronal holes are about a factor of 2 lower than in quiet-Sun regions. The decrease of density with height is exponential in the polar holes. We also confirm the result known from a variety of earlier observations that the temperature of most of the plasma in coronal holes does not exceed about 106 K. Title: Translimb Spectroscopy with SOHO/SUMER Authors: Ayres, T. R.; Lemaire, P.; Schuhle, U.; Wilhelm, K.; Ruedi, I.; Solanki, S. Bibcode: 1997SPD....28.0104A Altcode: 1997BAAS...29..879A We have used SUMER to obtain deep exposures of the 1300--1400 Angstroms spectrum, at the extreme limb and off-limb. Previous ``translimb'' studies in the thermal infrared had revealed remarkable extensions of cold material (T ~ 3000 K)---traced by carbon monoxide emission lines---into the heart of the hot chromosphere. A main objective of our program was to search for corresponding far-UV signatures of the ``thermally-bifurcated'' low chromosphere; for example, radiatively fluoresced emissions of the CO A--X 4th-positive system (collisional excitation would be negligible in cold gas). We conducted two separate observing programs with SUMER. Both made use of the 1('') -diameter circular aperture, translated across the limb in the minimum motor step increments of 0.('') 375, along the central meridian in the Northern polar coronal hole. The first program executed for nine hours beginning 19UT 25 Oct 1996. The full wavelength range was 1340--1400 Angstroms. It was recorded in two overlapping segments, placing key regions of the spectrum alternately on the KBr and bare parts of the detector, to help isolate 2nd-order features. Each segment was integrated for 500 s, and 32 pairs were obtained to span a 12('') swath centered on the optical limb. The second program was conducted 00--09UT 01 Dec 1996. It consisted of a single wavelength setting (1300--1340 Angstroms) with exposure time 500 s, but twice the spatial coverage of the earlier series: 64 steps, for a total displacement of 24('') . The strong chromospheric resonance lines of atomic oxygen (1302--1305 Angstroms) and ionized carbon (1334--1335 Angstroms) were observed on the bare part of the MCP camera. We report our progress in cataloging the rich, diverse translimb emission spectrum; and our efforts to deduce fundamental properties of the thermally heterogeneous chromosphere. [-3mm] SOHO is a project of international cooperation; the participation of TRA was supported by NASA grant NAG5-3226. Title: New Insights into the Physical Mechanisms of Polar Plumes with Observations from the SUMER Instrument on SOHO Authors: Hassler, Donald M.; Wilhelm, Klaus; Lemaire, Philippe; Schuehle, Udo Bibcode: 1997SPD....28.0802H Altcode: 1997BAAS...29..912H SUMER (Solar Ultraviolet Measurements of Emitted Radiation) line profiles above the limb in coronal holes are important for constraining thermodynamic models governing the outflow of the solar wind. Observational constraints in terms of thermal and nonthermal velocities, and upper limits on wave velocity amplitudes can be directly compared with in-situ observations. We present new observations of line profiles in polar plumes, and inter-plume regions, above the limb in coronal holes obtained with the SUMER instrument on the SOHO spacecraft. Detailed structure can be seen extending beyond 1.5 solar radii (out to the edge of the SUMER field-of-view), with intensities in the plume regions roughly 10-50% brighter than the inter-plume regions, but line widths in the plumes roughly 10% narrower than the inter-plume regions. Possible explanations for this observed anti-correlation between line width and intensity, and the correspondence with observed in-situ solar wind signatures will be discussed. Title: VizieR Online Data Catalog: Solar disk spectrum (660-1175A) (Curdt+ 1997) Authors: Curdt, W.; Feldman, U.; Laming, J. M.; Wilhelm, K.; Schuehle, U.; Lemaire, P. Bibcode: 1997yCat..41260281C Altcode: The near-limb quiet-Sun spectrum recorded on January 25, 1996 near the solar North pole is presented in tabular form and in graphical form. Table 1 - the line list - lists all lines found in the spectrum providing absolute peak intensities, measured and literature wavelengths, identification, and classification of the transition. Fig. 4 is a display the composite spectrum. The most prominent lines are labelled. In this figure intensities are given in instrumental units and logarithmic scale. (1 data file). Title: Determination of the Formation Temperature of Si IV in the Solar Transition Region Authors: Doschek, G. A.; Mariska, J. T.; Warren, H. P.; Wilhelm, K.; Lemaire, P.; Kucera, T.; Schühle, U. Bibcode: 1997ApJ...477L.119D Altcode: Using spectra obtained with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory spacecraft, we deduce the temperature of formation of the Si IV ion in the solar transition region from the Si IV ultraviolet spectral line intensity ratio, 3p 2P3/2-3d 2D3/2,5/2/3s 2S1/2-3p 2P1/2, and compare the result to the temperature predicted under the assumption of ionization equilibrium. The wavelengths are as follows: 2D3/2,5/2, 1128.325, 1128.340 Å 2P1/2, 1402.770 Å. Ratios are derived for typical features of the quiet Sun, such as cell center and network, and are systematically higher than those predicted at the 6.3 × 104 K ionization equilibrium temperature of formation of Si IV. For most solar features the ratios imply a temperature of formation of about 8.5 × 104 K. The ratios for the faintest features imply a temperature of formation of up to 1.6 × 105 K. It is not clear, however, that all the discrepancies between the measured and theoretical ratios are due to a temperature effect. Accurate temperature measurements are important since a large discrepancy from ionization equilibrium has significant implications for the physics of the transition region, such as the possible presence of nonthermal electrons. Title: First Results from SOHO on Waves Near the Solar Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.; Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.; Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten, R. J. Bibcode: 1997ASPC..118..284S Altcode: 1997fasp.conf..284S We present first results from simultaneous observations with the CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995) for a description of the instruments} onboard SOHO and the VTT at Tenerife. Our aim is to study the wave propagation, shock formation, and transmission properties of the upper chromosphere and transition region. The preliminary results presented here include the variation of velocity power spectra with height, difference in power between internetwork and network regions, and variations in mean flows displayed by different spectral lines. Title: SUMER Observations Detecting Downward Propagating Waves in the Solar Transition Region Authors: Wiskstøl, Ø.; Judge, P. G.; Hansteen, V.; Wilhelm, K.; Schühle, U.; Moran, T. Bibcode: 1997ESASP.404..731W Altcode: 1997cswn.conf..731W No abstract at ADS Title: Bright Plumes and Dark Lanes as Observed in MgX 625 Å and NV 1239 Å in the Solar Polar Corona Authors: Marsch, E.; Tu, C. -Y.; Wilhelm, K.; Curdt, W.; Schühle, U.; Dammasch, I. E. Bibcode: 1997ESASP.404..555M Altcode: 1997cswn.conf..555M No abstract at ADS Title: A New Look at the Quiet Sun Network in the Upper Atmosphere During a Minimum of Activity Cycle Authors: Lemaire, P.; Schuehle, U.; Curdt, W.; Wilhelm, K.; Poland, A.; Falciani, R. Bibcode: 1997ESASP.404..517L Altcode: 1997cswn.conf..517L No abstract at ADS Title: First Results of the SUMER Telescope and Spectrometer on SOHO - I. Spectra and Spectroradiometry Authors: Wilhelm, K.; Lemaire, P.; Curdt, W.; Schühle, U.; Marsch, E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Huber, M. C. E.; Vial, J. -C.; Kühne, M.; Siegmund, O. H. W.; Gabriel, A.; Timothy, J. G.; Grewing, M.; Feldman, U.; Hollandt, J.; Brekke, P. Bibcode: 1997SoPh..170...75W Altcode: SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) - observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar coronal hole. Using detector A of the instrument, this range was later extended to 1610 Å. The second-order spectra of detectors A and B cover 330 to 805 Å and are superimposed on the first-order spectra. Many more features and areas of the Sun and their spectra have been observed since, including coronal holes, polar plumes and active regions. The atoms and ions emitting this radiation exist at temperatures below 2 × 106 K and are thus ideally suited to investigate the solar transition region where the temperature increases from chromospheric to coronal values. SUMER can also be operated in a manner such that it makes images or spectroheliograms of different sizes in selected spectral lines. A detailed line profile with spectral resolution elements between 22 and 45 mÅ is produced for each line at each spatial location along the slit. From the line width, intensity and wavelength position we are able to deduce temperature, density, and velocity of the emitting atoms and ions for each emission line and spatial element in the spectroheliogram. Because of the high spectral resolution and low noise of SUMER, we have been able to detect faint lines not previously observed and, in addition, to determine their spectral profiles. SUMER has already recorded over 2000 extreme ultraviolet emission lines and many identifications have been made on the disk and in the corona. Title: SOHO observations of the north polar solar wind Authors: Peres, G.; Ciaravella, A.; Betta, R.; Orlando, S.; Reale, F.; Kohl, J.; Noci, G.; Fineschi, S.; Romoli, M.; Brekke, P.; Fludra, A.; Gurman, J. B.; Lemaire, P.; Schuhle, U. Bibcode: 1997ESASP.404..587P Altcode: 1997cswn.conf..587P No abstract at ADS Title: High resolution solar ultraviolet measurements Authors: Lemaire, P.; Wilhelm, K.; Schühle, U.; Curdt, W.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial, J. -C. Bibcode: 1997AdSpR..20.2249L Altcode: The increase of our understanding of the processes acting in the solar corona and maintaining it is strongly dependent on the quality of the data that are obtained to check theories. The fine structure of the solar atmosphere seen from the photosphere and extending to the hottest parts of the corona requires data with high resolution in all parameter space (angular, spectral and temporal). To constrain the hypotheses that are proposed to describe the solar corona, it is necessary to establish an accurate energy budget taking into account the processes which are acting from the chromosphere to the corona. Some requirements can be established and compared with the data collected so far (or about to be collected) with the present SUMER (Solar Utraviolet Measurements of Emitted Radiations) instrumentation. Title: First Results of the SUMER Telescope and Spectrometer on SOHO - II. Imagery and Data Management Authors: Lemaire, P.; Wilhelm, K.; Curdt, W.; SchÜle, U.; Marsch, E.; Poland, A. I.; Jordan, S. D.; Thomas, R. J.; Hassler, D. M.; Vial, J. C.; KÜhne, M.; Huber, M. C. E.; Siegmund, O. H. W.; Gabriel, A.; Timothy, J. G.; Grewing, M. Bibcode: 1997SoPh..170..105L Altcode: SUMER - Solar Ultraviolet Measurements of Emitted Radiation - is not only an extreme ultraviolet (EUV) spectrometer capable of obtaining detailed spectra in the range from 500 to 1610 Å, but, using the telescope mechanisms, it also provides monochromatic images over the full solar disk and beyond, into the corona, with high spatial resolution. We report on some aspects of the observation programmes that have already led us to a new view of many aspects of the Sun, including quiet Sun, chromospheric and transition region network, coronal hole, polar plume, prominence and active region studies. After an introduction, where we compare the SUMER imaging capabilities to previous experiments in our wavelength range, we describe the results of tests performed in order to characterize and optimize the telescope under operational conditions. We find the spatial resolution to be 1.2 arc sec across the slit and 2 arc sec (2 detector pixels) along the slit. Resolution and sensitivity are adequate to provide details on the structure, physical properties, and evolution of several solar features which we then present. Finally some information is given on the data availability and the data management system. Title: Building the Spectrum of a G2V Star During a Minimum of Activity Cycle Authors: Lemaire, P.; Schuehle, U.; Curdt, W.; Wilhelm, K.; Hassler, D. Bibcode: 1997ESASP.404..513L Altcode: 1997cswn.conf..513L No abstract at ADS Title: Investigation of the Dynamics of Chromosphere and Photosphere from Spectra Obtained by Parallel Observations using SUMER on SOHO and the VTT on Tenerife Authors: Curdt, W.; Kucera, A.; Rybak, J.; Schuhle, U.; Wohl, H. Bibcode: 1997ASPC..118..322C Altcode: 1997fasp.conf..322C This is a preliminary report about parallel observations of chromospheric and photospheric spectra in the ultraviolet and visible spectral regions using SUMER on SOHO and the VTT on Tenerife performed begin of September 1996. The aim is to search for relations of vertical velocity patterns in the upper photosphere and chromosphere in the solar disk center. In addition temporal changes in these parts of the solar atmosphere are investigated. Title: Dynamical Properties of the Chromosphere and Transition Region in the Supergranular Network: What Precision of the Spectral Line Characteristics Can be Reached? Authors: Curdt, W.; Kucera, A.; Rybák, J.; Schühle, U.; Wöhl, H. Bibcode: 1997ESASP.404..307C Altcode: 1997cswn.conf..307C No abstract at ADS Title: Radiometric calibration of the telescope and ultraviolet spectrometer SUMER on SOHO Authors: Hollandt, Jörg; Schühle, Udo; Paustian, Wolfgang; Curdt, Werner; Kühne, Michael; Wende, Burkhard; Wilhelm, Klaus Bibcode: 1996ApOpt..35.5125H Altcode: The prelaunch spectral-sensitivity calibration of the solar spectrometer SUMER (Solar Ultraviolet Measurements of Emitted Radiation) is described. SUMER is part of the payload of the Solar and Heliospheric Observatory (SOHO), which begins its scientific mission in 1996. The instrument consists of a telescope and a spectrometer capable of taking spatially and spectrally highly resolved images of the Sun in a spectral range from 50 to 161 nm. The pointing capabilities, the dynamic range, and the sensitivity of the instrument allow measurements both on the solar disk and above the limb as great as two solar radii. To determine plasma temperatures and densities in the solar atmosphere, the instrument needs an absolute spectral-sensitivity calibration. Here we describe the prelaunch calibration of the full instrument, which utilizes a radiometric transfer-standard source. The transfer standard was based on a high-current hollow-cathode discharge source. It had been calibrated in the laboratory for vacuum UV radiometry of the Physikalisch-Technische Bundesanstalt by use of the calculable spectral photon flux of the Berlin electron storage ring for synchrotron radiation (BESSY)-a primary radiometric source standard. Title: A Solar EUV Spectral Atlas Observed with SUMER Authors: Brekke, P.; Wilhelm, K.; Lemaire, P.; Curdt, W.; Schuhle, U.; Poland, A.; Kucera, T.; Hassler, D. M.; Siegmund, O. H. W. Bibcode: 1996AAS...188.3713B Altcode: 1996BAAS...28..879B We present the first solar EUV spectral atlas in the wavelength range 500 -- 1600 { Angstroms}. The spectra were recorded with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) which is part of the ESA/NASA Solar and Heliospheric Observatory (SOHO). The solar spectrum below 1200 { Angstroms} is not very well known. Thus, the present spectral atlas, and SUMER observations in general, represents a new important diagnostic tool to study essential physical parameters of the solar atmosphere. It includes emission from atoms and ions in the temperature range 10(4) to 2 x 10(6) K. Thus, emission lines and continua emitted from the lower chromosphere to the lower corona can be studied. The atlas is also useful as a planning tool for SUMER studies to determine useful dwell times, possible blends, and to select proper data extraction windows. The angular resolution of SUMER is close to 1 arcsec, but the atlas presented here represents an average along part of the 1-arcsec wide slit, typically 30 arcsec. The spectral resolving power of the instrument is lambda /Delta lambda = 17770-38300. For more details about the SUMER instrument we refer to Wilhelm et al. (Solar Physics, 162, 189, 1995). The spectral data in this atlas were obtained with the spectrometer slit positioned at the center of the solar disk with a dwell time of 300 s to bring up weak lines and continua. The full spectral range was put together from a number of exposures each covering approximately 20 { Angstroms} in 1st order on the coated, and therefore most sensitive, part (KrB) of the detector. 1st and 2nd order spectra are superimposed. The spectral atlas is available in a computer readable format together with a IDL program to read and display the data using a widget interface. The atlas and the programs can be obtained via the World Wide Web (http://hydra.mpae.gwdg.de/mpae_projects/SUMER/sumer.html) or by contacting one of the authors. Title: Intercalibration and Co-Registration of the LASCO, UVCS and SUMER instruments on SOHO Authors: Michels, J.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Curdt, W.; Hollandt, J.; Lemaire, P.; Schuhle, U.; Wilhelm, K.; Korendyke, C.; Moran, T.; Raymond, J. C.; Romoli, M.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano, S.; Naletto, G.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L. Bibcode: 1996AAS...188.3706M Altcode: 1996BAAS...28..878M Joint observations of equatorial streamers by three SOHO instruments have been used for radiometric intercalibration, co-registration and other spectroscopic comparisons. The results are used to track the stability of the radiometric calibrations of the Ultraviolet Coronagraph Spectrometer (UVCS) and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) experiment at overlapping wavelenghs. Observations of equatorial streamers at heliocentric heights from 1.25 to 1.5 R_⊙ are used for the intercalibrations. The results are compared to pre-launch laboratory calibrations and to observations of stars. The first stellar observation was for 38 AQI. These UV observations are compared to coronal green line (Fe XIV) observations obtained with the Large Angle Spectrometric Coronagraph (LASCO) C1 coronagraph obtained in the same time frame. Intercomparisons of spectral line profiles among LASCO, SUMER, and UVCS are also planned. The LASCO research is supported by NASA Grant NDPR S92835D; the UVCS research is supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland, and SUMER is financially supported by BMFT/DARA, CNES, NASA and PRODEX (Swiss Contribution). Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schühle, U.; Lemaire, P.; Gabriel, A.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kühne, M.; Timothy, J. G.; Hassler, D. M.; Siegmund, O. H. W. Bibcode: 1995SoPh..162..189W Altcode: The instrument SUMER - Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 × 106K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in many solar features, and will support penetrating studies of underlying physical processes, including plasma flows, turbulence and wave motions, diffusion transport processes, events associated with solar magnetic activity, atmospheric heating, and solar wind acceleration in the inner corona. Specifically, SUMER will measure profiles and intensities of EUV lines; determine Doppler shifts and line broadenings with high accuracy; provide stigmatic images of the Sun in the EUV with high spatial, spectral, and temporal resolution; and obtain monochromatic maps of the full Sun and the inner corona or selected areas thereof. SUMER will be flown on the Solar and Heliospheric Observatory (SOHO), scheduled for launch in November, 1995. This paper has been written to familiarize solar physicists with SUMER and to demonstrate some command procedures for achieving certain scientific observations. Title: Some design and performance features of SUMER: solar ultraviolet measurements of emitted radiation Authors: Wilhelm, Klaus; Curdt, W.; Marsh, E.; Schuehle, Udo H.; Lemaire, Philippe; Gabriel, Alan H.; Vial, J. -C.; Grewing, Michael; Huber, Martin C.; Jordan, S. D.; Poland, Arthur I.; Thomas, Roger J.; Kuehne, Mikhael; Timothy, J. Gethyn; Hassler, Donald M.; Siegmund, Oswald H. Bibcode: 1995SPIE.2517....2W Altcode: The instrument SUMER (solar ultraviolet measurements of emitted radiation) is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 multiplied by 106 K and above. The observations will be performed, on board SOHO (solar and heliospheric observatory) scheduled for launch in November 1995, by a scanning, normal-incidence telescope/spectrometer system in the wavelength range from 500 to 1610 angstrom. Spatial resolution requirements compatible with the pointing stability of SOHO are less than 1000 km corresponding to about 1-arcsec angular resolution. Doppler observations of EUV line shifts and broadenings should permit solar plasma velocity measurements down to 1 km s-1. We report here on some specific features of this instrument related to its pointing as well as its spatial and spectral resolution capabilities. Title: Solar Ultraviolet Measurements of Ultraviolet Radiation (SUMER) instrument on SOHO: design, performance predictions, and calibration aspects Authors: Schuehle, Udo H. Bibcode: 1994SPIE.2283...47S Altcode: The solar EUV spectrometer SUMER will operate in the wavelength range 500 angstrom to 1600 angstrom on the SOHO spacecraft. It will allow measurements of profiles, Doppler shifts, and intensities of solar extreme ultraviolet lines. Various mechanisms for pointing and focusing of the optical components contribute to the versatility of the instrument. The normal incidence optical design of the telescope and the spectrometer puts very stringent constraints on the cleanliness of the instrument and the mechanical design. The calibration techniques used, including imaging tests in the EUV, wavelength, and radiometric calibrations are outlined, and performance predictions are given. Title: 'SUMER' - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kuhne, M.; Lemaire, P.; Marsch, E.; Poland, A. I.; Schuhle, U.; Thomas, R. J.; Timothy, J. G.; Vial, J. -C. Bibcode: 1994scs..conf..619W Altcode: 1994IAUCo.144..619W SUMER is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. The spatial and spectral resolution capabilities of the instrument are considered in some detail, and a new detector concept is introduced. Title: SUMER - Solar Ultraviolet Measurements of Emitted Radiation Authors: Wilhelm, K.; Curdt, W.; Marsch, E.; Schuehle, U.; Gabriel, A. H.; Lemaire, P.; Vial, J. -C.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Poland, A. I.; Thomas, R. J.; Kuehne, M.; Timothy, J. G. Bibcode: 1993BAAS...25.1192W Altcode: No abstract at ADS Title: The Cleanliness Control Program for SUMER/SOHO Authors: Schühle, U. Bibcode: 1993uxrs.conf..373S Altcode: No abstract at ADS