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Author name code: roddier
ADS astronomy entries on 2022-09-14
author:"Roddier, Francois"
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Title: Adaptive Optics in Astronomy
Authors: Roddier, François
2004aoa..book.....R Altcode:
Part I. Introductory Background: 1. Historical context F. Roddier;
2. Imaging through the atmosphere F. Roddier; Part II. The Design of an
Adaptive Optics System: 3. Theoretical aspects F. Roddier; 4. Wave-front
compensation devices M. Séchaud; 5. Wave-front sensors G. Rousset;
6. Control techniques P.-Y. Madec; 7. Performance estimation and
system modeling M. Northcott; Part III. Adaptive Optics with Natural
Guide Stars: 8. The COME-ON/ADONIS systems G. Rousset and J.-L. Beuzit;
9. The UH-CFHT systems F. Roddier and F. Rigaut; 10. Adaptive optics in
solar astronomy J. Beckers; Part IV. Adaptive Optics with Laser Beacons:
11. Overview of adaptive optics with laser beacons D. Sandler; 12. The
design of laser beacon AO systems D. Sandler; 13. Laser beacon adaptive
optics systems D. Sandler; Part V. The Impact of Adaptive Optics in
Astronomy: 14. Observing with adaptive optics P. Léna and O. Lai;
15. Astronomical results P. Léna and O. Lai; 16. Future expectations
F. Roddier; Index.
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Title: New neighbours. III. 21 new companions to nearby dwarfs,
discovered with adaptive optics
Authors: Beuzit, J. -L.; Ségransan, D.; Forveille, T.; Udry, S.;
Delfosse, X.; Mayor, M.; Perrier, C.; Hainaut, M. -C.; Roddier, C.;
Roddier, F.; Martín, E. L.
2004A&A...425..997B Altcode: 2001astro.ph..6277B
We present some results of a CFHT adaptive optics search for companions
to nearby dwarfs. We identify 21 new components in solar neighbourhood
systems, of which 13 were found while surveying a volume-limited
sample of M dwarfs within 12 pc. We are obtaining complete
observations for this subsample, to derive unbiased multiplicity
statistics for the very-low-mass disk population. Additionally,
we resolve for the first time 6 known spectroscopic or astrometric
binaries, for a total of 27 newly resolved companions. A significant
fraction of the new binaries has favourable parameters for accurate
mass determinations. The newly resolved companion of Gl 120.1C was
thought to have a spectroscopic minimum mass in the brown-dwarf range
(Duquennoy & Mayor \cite{duquennoy91}), and it contributed to the
statistical evidence that a few percent of solar-type stars might have
close-in brown-dwarf companions. We find that Gl 120.1C actually is
an unrecognised double-lined spectroscopic pair. Its radial-velocity
amplitude had therefore been strongly underestimated by Duquennoy &
Mayor (\cite{duquennoy91}), and it does not truly belong to their
sample of single-lined systems with minimum spectroscopic mass below
the substellar limit. We also present the first direct detection of Gl
494B, an astrometric brown-dwarf candidate. Its luminosity straddles
the substellar limit, and it is a brown dwarf if its age is less than
∼300 Myr. A few more years of observations will ascertain its mass
and status from first principles. <P />Based on observations made
at Canada-France-Hawaii Telescope, operated by the National Research
Council of Canada, the Centre National de la Recherche Scientifique de
France and the University of Hawaii. Some of the data presented herein
were obtained at the W. M. Keck Observatory, which is operated as a
scientific partnership among the California Institute of Technology,
the University of California and the National Aeronautics and Space
Administration. The Observatory was made possible by the generous
financial support of the W. M. Keck Foundation.
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Title: Deconvolution of astronomical images obtained from ground-based
telescopes with adaptive optics
Authors: Fusco, Thierry; Mugnier, Laurent M.; Conan, Jean-Marc;
Marchis, Franck; Chauvin, G.; Rousset, Gerard; Lagrange, Anne-Marie;
Mouillet, David; Roddier, Francois J.
2003SPIE.4839.1065F Altcode:
Deconvolution is a necessary tool for the exploitation of adaptive
optics corrected images, because the correction is partial. The Maximum
A Posteriori (MAP) framework is used to derive a deconvolution method
(MISTRAL) that combines the data with our knowledge of the noise
statistics as well as our prior information about the object and
the variability of the Point Spread Function. The deconvolution of
experimental and scientific data illustrates the capabilities of
this method.
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Title: A nulling wide field imager for exoplanets detection and
general astrophysics
Authors: Guyon, O.; Roddier, F.
2002A&A...391..379G Altcode: 2002astro.ph..5523G
We present a solution to obtain a high-resolution image of a wide
field with the central source removed by destructive interference. The
wide-field image is created by aperture synthesis with a rotating sparse
array of telescopes in space. Nulling of the central source is achieved
using a phase-mask coronagraph. The full (u,v) plane coverage delivered
by the 60 m, six 3-meter telescope array is particularly well-suited
for the detection and characterization of exoplanets in the infrared
(DARWIN and Terrestrial Planet Finder (TPF) missions) as well as for
other generic science observations. Detection (S/N=10) of an Earth-like
planet is achieved in 10 hours with a 1 mu m bandwidth at 10 mu m.
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Title: Curvature Wavefront Sensor For Solar Adaptive Optics
Authors: Molodij, G.; Roddier, F.; Kupke, R.; Mickey, D. L.
2002SoPh..206..189M Altcode:
Active or adaptive optics often require the ability to characterize
wavefront aberrations using natural extended sources. The task becomes
especially challenging when dealing with widely extended sources such as
the solar granulation. We propose a new approach based on the processing
of oppositely defocused images. This method, which is a generalization
of a technique known as curvature sensing, derives the wavefront
curvature from the difference between two oppositely defocused images
and determines the second momenta of the point spread function. The
proposed method measures the wavefront aberration from the images
themselves, requires little computational resources, is fast enough
to be used in a real-time adaptive optics system and is particularly
adapted to random patterns such as solar granulation or spot penumbras
whose morphology evolves during the observation. We envision the
application of the method to real-time seeing compensation in solar
astronomical telescopes, and to the correction of optical system
aberrations in remote sensing instrumentation. This effort is directed
towards building a curvature sensor for the real-time applications.
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Title: Atmospheric limitations to adaptive image compensation
(Invited Speaker)
Authors: Roddier, F.
2002ASPC..266..546R Altcode: 2002asev.conf..546R
No abstract at ADS
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Title: Concepts for a Large-Aperture, High Dynamic Range Telescope
Authors: Kuhn, J. R.; Moretto, G.; Racine, R.; Roddier, F.; Coulter, R.
2001PASP..113.1486K Altcode:
This paper summarizes concept studies for a large telescope capable
of wide-field imaging and of the highest possible dynamic range for
photometry and angular resolution. Point-spread functions (PSFs) and
scattered light levels at large offsets are computed and compared
for four telescopes of the same light-gathering power but with
different pupil functions:1. a reference monolithic mirror telescope
with a 17.4 m primary,2. a segmented mirror telescope (SMT) with a
hexagonally segmented primary,3. a hexagonal off-axis telescope (HOT)
with a distributed aperture made of 6×6.5 m unobstructed circular
mirrors that are identical off-axis sections of a parent 20 m mirror,
and4. a square off-axis telescope (SOT) whose aperture is made of 4×8
m off-axis mirrors. The characteristics of the PSFs are examined in
the diffraction- and seeing-limited regimes, assuming (1) perfect
mirror figure and (2) realistic figure errors (edge defects). The
implications of field rotation with an altitude-azimuth mounting
are discussed in each case. The implementation of adaptive optics
(AO) and the properties of AO-compensated PSFs having a Strehl
ratio of 0.5, and of coronagraphic imaging, are also discussed for
the four configurations. It is shown that, in the seeing-limited
regime and as intuitively expected, the optical performance of all
four telescopes is comparable. With higher order adaptive optics and
for coronagraphic observations, the SOT and HOT are superior to the
SMT. This distinction becomes larger with relaxed constraints on mirror
edge-polishing requirements. A full optical design is presented for the
novel HOT configuration, and optical fabrication issues are briefly
addressed. Finally, science programs and possible instrumentation
layouts with the HOT are briefly explored for different modes of
operation. It appears that the natural “optical bench” configuration
of the HOT can provide a remarkably versatile and convenient environment
for instrument deployment.
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Title: Detection of arcs in Saturn's F ring during the 1995 Sun
ring-plane crossing
Authors: Charnoz, S.; Brahic, A.; Ferrari, C.; Grenier, I.; Roddier,
F.; Thébault, P.
2001A&A...365..214C Altcode: 2000astro.ph.10449C
Observations of the November 1995 Sun crossing of the Saturn's
ring-plane made with the 3.6 m CFH telescope, using the UHAO adaptive
optics system, are presented here. We report the detection of four
arcs located in the vicinity of the F ring. They can be seen one day
later in HST images. The combination of both data sets gives accurate
determinations of their orbits. Semi-major axes range from 140 020
km to 140 080 km, with a mean of 140 060 +/- 60 km. This is about 150
km smaller than previous estimates of the F ring radius from Voyager
1 and 2 data, but close to the orbit of another arc observed at the
same epoch in HST images.
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Title: Aperture Rotation Synthesis: Optimization of the(u, v)-Plane
Coverage for a Rotating Phased Array of Telescopes
Authors: Guyon, Olivier; Roddier, François
2001PASP..113...98G Altcode:
The problem of optimizing the (u, v)-plane coverage of a rotating
phased array of telescopes is assessed. We search for solutions for
maximum uniform (u, v)-plane coverage. Using a simulated annealing
algorithm, we find the optimal configurations for rotating arrays with
between four and 10 identical telescopes. With few modifications,
the same algorithm can find optimal array configurations adapted to
specific observations for which the optimal (u, v)-plane coverage is
different. We also demonstrate that such rotation-optimized arrays
are capable of recovering images of complex sources and obtaining
spectroscopic information.
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Title: Substellar mass companion search with adaptive optics at
University of Hawaii
Authors: Baudoz, P.; Roddier, F.; Roddier, C.; Guyon, O.; Potter,
D.; Brandner, W.; Gay, J.; Rabbia, Y.; Close, L.
2000AAS...197.5208B Altcode: 2000BAAS...32.1491B
We present the search of substellar mass companions around nearby stars
which we are pursuing at University of Hawaii. Our strategy for such
survey embraces the use of two different instruments: The University
of Hawaii adaptive optics curvature system Hokupa'a placed on Gemini
North and the Observatoire de la Cote d'Azur Nulling Coronagraph
(called AIC) which is installed on PUEO (CFHT adaptive optics). We will
show how the two instruments are complementary for a substellar mass
survey. Preliminary results will be shown to demonstrate that the point
source detection limit with Hokupa'a on Gemini is very efficient at
angular distances larger than one arcseconds (8 magnitudes in K at one
arcsecond) while the point source detection limit for AIC on PUEO/CFHT
is more efficient at shorter angular distances (4 magnitudes in K at 0.1
arcsecond). This research acknowledges support by NSF, NASA and CNRS.
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Title: QSO hosts imaging capabilities of Hokupa'a on the Gemini
North telescope
Authors: Guyon, O.; Sanders, D.; Roddier, C.; Roddier, F.; Brandner,
W.; Baudoz, P.; Potter, D.
2000AAS...197.5209G Altcode: 2000BAAS...32R1491G
The University of Hawaii Adaptive Optics system, Hokupa'a, now operating
on the Gemini North telescope, offers unique possibilities of high
resolution and high dynamical range imaging of quasar hosts. This
is the only Adaptative Optics system able to guide on faint targets
(up to V magn = 17 to 18) on a 8-m class telescope, delivering images
with FWHM from 0.1 to 0.2 arcsec in K and H bands for magnitude 16
sources. With careful PSF substraction, we find that we can detect point
sources with a 7 magnitudes difference at 0.6 arcsec and 6 magnitudes
difference at 0.25 arcsec. We are currently carrying out a deep, high
dynamical range, volume-limited imaging survey of QSO hosts. We give
hosts magnitude detection limits for various QSO V magnitudes and show
how this work can answer some questions about the formation of quasars.
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Title: Instrumentation: Adaptive Optics
Authors: Roddier, F.
2000eaa..bookE2913R Altcode:
Turbulence in the Earth's atmosphere produces inhomogeneities in
the refractive index of the air, which affect the image quality of
ground-based telescopes (see SEEING). ADAPTIVE OPTICS (AO) is a means
for the real-time compensation of image degradation. It consists of
using an active optical element such as a deformable mirror to correct
the instantaneous wave-front distortions. These are measur...
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Title: Erratum: Neptune's Cloud Structure and Activity: Ground-based
Monitoring with Adaptive Optics, Volume 136, Number 1, pp.168-172
(1998)
Authors: Roddier, F.; Roddier, C.; Graves, J. E.; Northcott, M. J.;
Owen, T.
2000Icar..148..320R Altcode:
No abstract at ADS
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Title: A High-Resolution Polarimetry Map of the Circumbinary Disk
around UY Aurigae
Authors: Potter, Daniel E.; Close, Laird M.; Roddier, François;
Roddier, Claude; Graves, J. E.; Northcott, Malcolm
2000ApJ...540..422P Altcode:
We have obtained J-band (1.2 μm) polarimetry observations of the
circumbinary disk around UY Aurigae. These observations were made
possible by the use of the University of Hawaii 36 element adaptive
optics instrument, Hokupa'a, at the 3.35 m CFHT. The deep (120 minute),
high-resolution (0.15") polarization images reveal a centrosymmetric
polarization signature from the light scattered off the circumbinary
dust disk which is ~10<SUP>6</SUP> times fainter than the stars
in the binary system. A comparison with a Mie scattering model of
the circumbinary disk in UY Aurigae suggests that the polarization
signature is dominated by the smallest grains in the disk (~0.03 μm)
and further supports the hypothesis that the resolved light seen in
the optical and infrared originates from a large flattened disk of
dust surrounding both stars.
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Title: Direct exoplanet imaging possibilities of the nulling stellar
coronagraph
Authors: Guyon, Olivier; Roddier, Francois J.
2000SPIE.4006..377G Altcode:
The nulling stellar coronagraph, first proposed by Roddier and Roddier
and later demonstrated in a laboratory experiment is a technique to
produce wide-field coronagraphic images. It uses a small phase-shifting
mask in the focal plane to remove the central star by destructive
interference. When applied to a space-based interferometric array of
telescopes, it can be a powerful tool to search for faint companions
around nearby stars or image circumstellar disks. A program was written
to simulate the performance of a nulling stellar coronagraph for single
or multi aperture telescopes in space or on the ground. In this study,
we explore some aspects of the use of such a technique. By running our
simulation program on various sources, we find that a nulling stellar
coronagraph applied on a space interferometer like Darwin or TPF can
image Earth-type planets in less than an hour of exposure time.
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Title: Deconvolution of adaptive optics images: from theory to
practice
Authors: Conan, Jean-Marc; Fusco, Thierry; Mugnier, Laurent M.;
Marchis, Franck; Roddier, Claude A.; Roddier, Francois J.
2000SPIE.4007..913C Altcode:
Practical guidelines are proposed for deconvolution of partially
adaptive optics corrected images: from raw data to high photometric
precision object restoration. Preliminary processing is discussed
(detector calibration, background subtraction...). The deconvolution
scheme itself is then presented. It takes into account the noise
statistics in the image, the imprecise knowledge of the point spread
function (PSF), and the available a priori information on the object
(spatial structure, positivity...). This deconvolution scheme is
first validated on simulated images of NAOS, the AO system of the
VLT and then applied to astronomical images. In particular, an edge
preserving regularization is tested on several solar system objects:
Io, Uranus and Neptune.
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Title: First light for Hokupa'a 36 on Gemini North
Authors: Graves, J. Elon; Northcott, Malcolm J.; Roddier, Francois
J.; Roddier, Claude A.; Potter, Dan; O'Connor, Daniel J.; Rigaut,
Francois J.; Chun, Mark R.
2000SPIE.4007...26G Altcode:
The University of Hawaii adaptive optics program has recently
moved its 36 actuators system, named 'Hokupa'a 36', to the Gemini
North Telescope. First light for Hokupa'a 36 was in time for the
dedication of this telescope during June 1999 and most of the images
presented were taken with this adaptive optics system. This paper will
cover the modifications to the CFHT, Hokupa'a 36 system that were
necessary to accommodate the larger 8 meter aperture of the Gemini
Telescope. Performance at the telescope has now been measured and
compares favorably with that predicted.
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Title: Infrared very large array for the 21st century
Authors: Ridgway, Stephen T.; Roddier, Francois J.
2000SPIE.4006..940R Altcode:
In order to exploit the interferometric resolution advantage to the
utmost, an array with a significant number of telescopes and large
(and variable) baselines will be required. Achieving the sensitivity
needed for a wide range of science opportunities requires large, AO
equipped individual apertures. Dual-beam operation will be needed to
support good sky coverage. Phasing of the array for resolved sources can
be accomplished with wide-band, pair-wise combination, bootstrapping,
and phase closure. For the best sensitivity with maximum field of view,
the imaging focus must employ direct optical synthesis of the PSF, while
for best sensitivity with reduced field-of-view, pupil densification
may be used. The suggested concept, for discussion purposes, consists
of 27 telescopes of 3.5-m aperture, distributed in a Cornwell circle
configuration. Such a facility would most likely have a cost in the
range discussed for a next generation large aperture telescope. The
technical readiness is good.
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Title: Design and performance of an 85-actuator curvature system
Authors: Northcott, Malcolm J.; Graves, J. Elon; Roddier, Francois J.;
Rigaut, Francois J.
2000SPIE.4007..126N Altcode:
The UH 36 element curvature AO system, Hokupa'a-36, was recently
moved to the Gemini 8m telescope, where it was used with great
success obtaining images for the telescope dedication. Since the
36 actuator system was optimized for performance on a 4 m (CFHT)
telescope it does not provide full near IR wavelength converge on the
Gemini 8m telescope. In order to address this issue we are planning to
upgrade the system to 85 actuators. Given the slightly better seeing
expected at the Gemini telescope, the move to 85 actuators will give
Strehl ratios commensurate to those obtained with 36 actuators on the
CFHT. The limiting magnitude will scale with the telescope aperture
giving considerably better sky coverage than at the CFHT. Curvature
AO systems can scale considerably beyond 85 actuators, at this point
technology presents the most important limitations to scaling.
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Title: Search for asteroidal satellites using adaptive optics
Authors: Close, Laird M.; Merline, William J.; Dumas, C.; Chapman,
Clark R.; Roddier, Francois J.; Menard, Francois; Slater, David C.;
Duvert, Gilles; Shelton, J. Christopher; Morgan, Thomas H.
2000SPIE.4007..796C Altcode:
We utilized AO to discover a moon around asteroid 45 Eugenia by use
of the PUEO AO facility at CFHT. With PUEO we performed a search for
asteroidal satellites among two dozen asteroids, achieving moderate
Strehl ratios (35%) and FWHM of about 0.12' at H band. During
this survey, we detected a faint close companion to 45 Eugenia. The
satellite was 6.14 magnitudes (at 1.65 micrometer) fainter and located
at most 0.75' from Eugenia. Without the ability of AO to sharpen the
contrast and increase the resolution to 0.1', the detection of this
companion would have been impossible with ground-based telescopes. The
companion was found to be in a 1200 km circular orbit with a period of
4.7 days. We discovered that the bulk density of the large (215 km)
asteroid 45 Eugenia is a surprisingly low 1.2 g/cm<SUP>3</SUP>. This
has lead to the exciting possibilities that either this main belt
asteroid is a burned out comet or has a hollow 'rubble-pile' structure.
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Title: Adaptive optics imaging of Pluto-Charon and the discovery
of a moon around the Asteroid 45 Eugenia: the potential of adaptive
optics in planetary astronomy
Authors: Close, Laird M.; Merline, William J.; Tholen, David J.;
Owen, Tobias C.; Roddier, Francois J.; Dumas, C.
2000SPIE.4007..787C Altcode:
We outline two separate projects which highlight the power of adaptive
optics (AO) to aid planetary research. The first project utilized
AO to discover a moon around asteroid 45 Eugenia by use of the PUEO
AO facility at CFHT. We also utilized AO to resolve the Pluto-Charon
system by producing 0.15' FWHM images. We used the University of Hawaii
AO system (Roddier et al. 1991) at CFHT to obtain deep (20 min) narrow
band images in and out of the molecular bands of water and methane ices.
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Title: NPT: a large-aperture telescope for high dynamic range
astronomy
Authors: Joseph, Robert D.; Kuhn, Jeff R.; Tokunaga, Alan T.; Coulter,
Roy; Ftaclas, Christo; Graves, J. Elon; Hull, Charles L.; Jewitt,
D.; Mickey, Donald L.; Moretto, Gilberto; Neill, Doug; Northcott,
Malcolm J.; Roddier, Claude A.; Roddier, Francois J.; Siegmund,
Walter A.; Owen, Tobias C.
2000SPIE.4005..333J Altcode:
All existing night-time astronomical telescopes, regardless of aperture,
are blind to an important part of the universe - the region around
bright objects. Technology now exist to build an unobscured 6.5
m aperture telescope which will attain coronagraphic sensitivity
heretofore unachieved. A working group hosted by the University of
Hawaii Institute for Astronomy has developed plans for a New Planetary
Telescope which will permit astronomical observations which have never
before ben possible. In its narrow-field mode the off-axis optical
design, combined with adaptive optics, provides superb coronagraphic
capabilities, and a very low thermal IR background. These make it ideal
for studies of extra-solar planets and circumstellar discs, as well as
for general IR astronomy. In its wide-field mode the NPT provides a 2
degree diameter field for surveys of Kuiper Belt Objects and Near-Earth
Objects, surveys central to current intellectual interests in solar
system astronomy.
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Title: Adaptive Optics in Astronomy
Authors: Roddier, François; Thompson, Laird
2000PhT....53d..69R Altcode:
No abstract at ADS
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Title: Adaptive Optics Observations of Saturn's Ring Plane Crossing
in August 1995
Authors: Roddier, F.; Roddier, C.; Brahic, A.; Dumas, C.; Graves,
J. E.; Northcott, M. J.; Owen, T.
2000Icar..143..299R Altcode:
Adaptive optics (0.15″ resolution) infrared images of the rings and
satellites of Saturn were obtained in August 1995 as the Earth was
crossing the ring plane. Twelve clumps were detected in the F ring,
including HST S5 and S7 objects. For the first time H magnitudes were
obtained for Prometheus, Pandora, Telesto, and Calypso, and J magnitudes
for Epimetheus, Janus, Mimas, Telesto, and Helene.
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Title: Five-Years of Adaptive Optics Observations of T Tau South
Authors: Roddier, F.; Roddier, C.; Brandner, W.; Charissoux, D.;
Véran, J. -P.; Courbin, F.
2000IAUS..200P..60R Altcode:
We describe the results of a five year monitoring of T Tau with adaptive
optics. Our main conclusions are: i) the orbital motion of the binary
suggests a system mass >= 3.3 M<SUB>odot</SUB>, and a minimum mass of
1.3 M<SUB>odot</SUB> for T Tau S, which rules out a very-low mass for
the infrared companion; ii) based on its near-infrared brightness and
color variations, T Tau S can be classified as an EXor-type variable;
iii) T Tau S appears to be resolved in the near-infrared AO data. The
data are consistent with a star plus an extended envelope.
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Title: Nulling Stellar Coronagraphic Imaging Using Space
Interferometric Arrays
Authors: Guyon, O.; Roddier, F.
2000ESASP.451...41G Altcode: 2000dais.conf...41G
No abstract at ADS
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Title: A New Planetary Telescope Concept
Authors: Joseph, R. D.; Kuhn, J. R.; Tokunaga, A.; Coulter, R.;
Ftaclas, C.; Graves, J. E.; Hull, C.; Jewitt, D.; Mickey, D.; Moretto,
G.; Neill, D.; Northcott, M.; Roddier, F.; Roddier, C.; Siegmund,
W.; Owen, T.
1999DPS....31.5943J Altcode: 1999BAAS...31.1591J
The NASA IRTF is arguably the only ground-based telescope in the
world dedicated to planetary astronomy. Two decades of improvement
in infrared array technology, adaptive optics, and large mirror
fabrication techniques now make it imperative that the future needs
of NASA's Planetary Astronomy program be considered in the context of
the capabilities now possible for a modern telescope. In response to
a suggestion from NASA Headquarters we have developed an innovative
telescope concept which provides unique and unsurpassed scientific
capabilities to the planetary community. We call this facility the New
Planetary Telescope (NPT). We have assumed that the main objectives
for the NPT are studies of Kuiper Belt Objects, Near-Earth Objects,
studies of circumstellar disks and extra-solar planets, and ground-based
support for NASA flight missions. These diverse scientific objectives
require capabilities ranging over wide-field imaging, high angular
resolution, high sensitivity in the optical and thermal infrared,
and superb photometric dynamic range. This study shows that it is
possible to achieve all of these performance requirements using a
6.5m unobstructed, off-axis telescope. This concept has compelling
natural advantages for adaptive optics, coronagraphic astronomical
imaging, and thermal infrared imaging. Unique features of the NPT
include wide-field imaging capability, with a field-of-view of at
least two degrees, optimization for unprecedented low scattered light
and high dynamic range astronomy, extremely low infrared emissivity,
and innovative instruments uniquely designed to take full advantage
of these capabilities. This telescope concept breaks new ground
in telescope technology, and it is therefore an ideal technical
development project for NASA. NASA is currently at the forefront
of development in interferometry using the Keck telescopes. The NPT
complements and enhances this program since it provides an important
baseline to add to those already planned on Mauna Kea. Moreover, the
NPT is the ideal telescope for a full-fledged optical/infrared array
of interferometric telescopes.
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Title: Adaptive Optics Imaging of Pluto-Charon and the Discovery of
a Moon aroun d the Asteroid 45 Eugenia: The Potential of Adaptive
Optics in Planetary Astrono my
Authors: Close, L. M.; Merline, W. J.; Tholen, D.; Owen, T.; Roddier,
F.; Dumas, C.
1999DPS....31.5910C Altcode: 1999BAAS...31.1585C
We outline two separate projects which highlight the power of adaptive
optics (AO) to aid planetary research. The first project utilized AO
to resolve the Pluto-Charon system by producing 0.15" FWHM images. We
used the University of Hawaii AO system (Roddier et al. PASP 103,
131,1991) at CFHT to obtain deep (20 min) narrow band images in/out
the molecular bands of water and methane ices. Our images confirm that
the variation of Pluto's albedo is mainly governed by the presence of
methane ice over its surface, resulting in a lower albedo at 2.26 um
than at 2.02 um. Our observations confirm also that Charon is mostly
covered with water-ice (Buie et al. NATURE 329, 522,1987). See Tholen et
al. (ICARUS submitted) for more details on these AO results. In another
application of AO, we discovered a moon around asteroid 45 Eugenia
by use of the PUEO AO facility at CFHT (Rigaut et al. PASP 110, 152,
1998). With PUEO we preformed a search for asteroidal satellites among
two dozen asteroids, achieving moderate Strehl ratios (35%) and FWHM
of about 0.12" at H band. During this survey, we detected a faint close
companion to 45 Eugenia. The satellite was 6.14 magnitudes (at 1.65 um)
fainter and located at most 0.75" from Eugenia. Without the ability
of AO (to sharpen the contrast and increase the resolution to 0.1"),
the detection of this companion would have been impossible with ground
based-telescopes. The companion was found to be in a 1200 km circular
orbit with a period of 4.7 days. A more detailed discussion of this new
satellite is given by Merline et al. in this volume. Adaptive optics
is entering a powerful new age as all the major ground based large
telescopes are developing facility AO systems. Planetary astronomy is
particularly well posed to take advantage of the diffraction-limited,
near-IR images (0.050" FWHM) that will become commonplace at all 8
m facilities in the near future (It is already occurring on the KECK
and GEMINI-North telescopes). In particular, we review plans for the
NAOS/CONICA AO facility instrument at the ESO 8m VLT that will have
first light in late 2000. It is planned that NAOS/CONICA will obtain
K-band Strehl ratios of 60% with reference objects (extended up to 3")
of brightness V=13 (or brighter). The instrument will allow guiding on
faint V=15 sources (with Strehls 20 well as tracking planetary targets
that have a velocity different from the guide source. The ability to
carry out remote service observing and an automatic data reduction
pipeline will make the ESO VLT AO system ideal for monitoring temporal
changes in planetary targets and carrying out targets of opportunity
programs in general. These AO observations were made possible by
support from the NSF, NASA, SwRI, and ESO.
---------------------------------------------------------
Title: Adaptive Optics Imaging and Spectroscopy of MWC 1080
Authors: Brandner, W.; Close, L.; Graves, B.; Northcott, M.; Potter,
D.; Roddier, C.; Roddier, F.; Tokunaga, A.; Dekany, R.; Troy, M.;
Brandl, B.; Hayward, T.; Bloemhof, E. E.; Gaidos, E.; Oppenheimer,
B. R.
1999AAS...195.0212B Altcode: 1999BAAS...31.1368B
We present adaptive optics near-infrared observations of the Herbig
AeBe binary MWC 1080 and its associated cluster of low-mass stars. The
adaptive optics data have been obtained with the 13 element curvature
sensing AO system, an optical CCD camera and the NIR camera QUIRC at
the CFHT 3.6m telescope, and with the 349/241 element Shack-Hartmann
AO system PALAO and the NIR camera PHARO at the Palomar 200” (5m)
telescope. The primary and its about 3mag fainter companion are clearly
detected and resolved at all wavebands from I to K. Spatially resolved
K-band spectra of both components of the 0.7” binary allow us for the
first time to derive individual spectral types for both components. In
addition to the central binary, the NIR data reveal about 30 faint
sources within 30” of MWC 1080. The sources exhibit various degrees
of IR excess and appear to be young low-mass stars associated with MWC
1080. By comparison with theoretical pre-main sequence evolutionary
tracks we are able to assign masses and ages. Narrow-band emission line
images in Brγ and H<SUB>2</SUB> are used to identify outflow features
and shocks. The high-spatial resolution data reveal that the bipolar,
hourglass shaped outflow cavity around MWC 1080 is illuminated by
scattered light. The pinched in, narrow waist of the hourglass can be
explained by a density gradient in the circumstellar medium, possibly
due to a circumstellar disk around MWC 1080. This research is supported
by NSF and NASA.
---------------------------------------------------------
Title: The Next-Generation Optical/IR Array
Authors: Ridgway, S. T.; Roddier, F.
1999AAS...195.2305R Altcode: 1999BAAS...31.1407R
Increasingly intense activity in optical interferometry over the past
two decades has led to the development and exploitation of numerous
prototype arrays. As interferometry gains in technical maturity, science
oriented facilities are beginning to come on-line, with at least 6
to be operational within a few years. These facilities offer major
advances in performance. Each is, however, relatively specialized,
or distinctly limited in some respects. Therefore, it appears to us
timely to consider the possible configuration of a next generation
array. In order to exploit the interferometric resolution advantage to
the utmost, an array with a significant number of telescopes and large
(and variable) baselines will be required. Achieving the sensitivity
needed for a wide range of science opportunities requires large, AO
equipped individual apertures. The suggested concept, for planning
and budgeting purposes, consists of 27 telescopes of 3.5-m aperture,
distributed in a Cornwell circle configuration. Such a facility would
most likely have a cost in the range discussed for a next generation
large aperture telescope. The technical readiness is excellent. With
an array size of 1 kilometer, J band angular resolution would be 200
microarcsec, and characterization of sources as small as 20 microarcsec
would be possible. Very high resolution interferometric imaging will
enable detailed study of compact solar system, stellar, galactic,
extragalactic and cosmological sources. The potential for studies of
normal and active galactic nuclei, interacting binaries, and YSO's,
are particularly promising. This paper was prepared for presentation
to the National Academy Decade Survey of Astronomy and Astrophysics,
and profited from the advice of many colleagues.
---------------------------------------------------------
Title: "High Angular Resolution Observations of Protoplanetary Disks
with Adaptive Optics"
Authors: Roddier, Francois
1999STIN...0004764R Altcode:
Significant results were obtained and published in the literature. The
first optical detection of a circumbinary disk was reported in the
ApJ at millimetric wavelengths. The size and inclination of this disk
were found to be consistent with millimetric observations. Evidence
was found for a cavity inside the disk as theory predicts from dust
clearing by the stellar companion.
---------------------------------------------------------
Title: An Adaptive Optics search for Low Mass Companions in the Ursa
Major Stream
Authors: Potter, D. E.; Tokunaga, A. T.; Close, L. M.; Graves, J. E.;
Northcott, M. J.; Roddier, F.; Roddier, C.; Kobayashi, N.
1999AAS...19510905P Altcode: 1999BAAS...31.1534P
We report the current status of an ongoing search for low mass
companions in the Ursa Major stream using the U. of Hawaii adaptive
optics (AO) system, Hokupa'a, and the CFHT user AO instrument, PUEO. The
high spatial resolution (FWHM<SUB>H</SUB>=0.12 arcsec), high dynamic
range (10<SUP>7</SUP> at 3 arcsec) AO images of more than half of
the Ursa Majoris stream have been obtained in a search for faint
companions to these nearby ( 25pc), young ( 0.3 Gyr) stars. The data
from these observations were image processed and Fourier filtered to
enhance point source detection in real time at the telescope using
a quick reduction software package written in IDL. The faint point
sources detected in the field are compared to a star count model of
the galaxy which estimates their probability as background stars.
---------------------------------------------------------
Title: Discovery of a moon orbiting the asteroid 45 Eugenia
Authors: Merline, W. J.; Close, L. M.; Dumas, C.; Chapman, C. R.;
Roddier, F.; Menard, F.; Slater, D. C.; Duvert, G.; Shelton, C.;
Morgan, T.
1999Natur.401..565M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Nulling Stellar Coronagraph: Laboratory Tests and
Performance Evaluation
Authors: Guyon, Olivier; Roddier, Claude; Graves, J. Elon; Roddier,
François; Cuevas, Salvador; Espejo, Carlos; Gonzalez, Salustio;
Martinez, Andrea; Bisiacchi, Gianfranco; Vuntesmeri, Valeri
1999PASP..111.1321G Altcode:
The nulling coronagraph, first proposed by Roddier and Roddier,
uses a small mask (less than half the size of the central Airy spot)
that shifts the phase of the incoming light by 180 deg to strongly
attenuate the Airy spot as well as the rings. We report on both
theoretical and laboratory performance. In our laboratory experiment,
we reduce the peak intensity of the Airy pattern by a factor of 16. We
derive estimates of the performance of a nulling coronagraph used
on a telescope equipped with an adaptive optics system, based upon
the performance of the University of Hawaii Hokupa'a adaptive optics
system. On a 3.6 m telescope at 1.65 μm, it is found that a tip/tilt
amplitude lower than 20 mas is needed for such a coronagraph to yield
an extinction better than 2 stellar mag.
---------------------------------------------------------
Title: Discovery of asteroidal satellite S/1998 (45) 1.
Authors: Merline, W. J.; Close, L. M.; Dumas, C.; Chapman, C. R.;
Roddier, F.; Ménard, F.; Colwell, W. B.; Slater, D. C.; Duvert, G.;
Shelton, C.; Morgan, T. H.
1999BAAS...31.1106M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Discovery of Asteroidal Satellite S/1998 (45) 1
Authors: Merline, W. J.; Close, L. M.; Dumas, C.; Chapman, C. R.;
Roddier, F.; Menard, F.; Colwell, W.; Slater, D. C.; Duvert, G.;
Shelton, C.; Morgan, T.
1999DPS....31.2006M Altcode:
On 1998 November 1, we performed the first imaging of an asteroidal
satellite from Earth-based observatories, when we detected a moon
of asteroid (45) Eugenia. Provisionally designated S/1998 (45) 1, the
satellite has a diameter of about 13 km and orbits the 215-km primary at
a distance of about 1200 km. The orbit is near-circular and has a period
of 4.7 days. Our observations show the object on 5 nights, spanning
two continuous orbital cycles, and it was again detected two months
later. At the time of discovery, the satellite was found to be about
6 magnitudes fainter than Eugenia, with a separation of 0.75 \arcsec;
the orbit was inclined to the line-of-sight by 45{\char'27}. Our
analysis suggests that the orbit is prograde (i.e., the orbit and
the primary spin are in the same sense) and lies approximately in
Eugenia's equatorial plane. Our measurements yield a tentative (because
of the uncertain size of Eugenia) bulk density of this C-like asteroid
of about 1.2 g cm(-3) , implying that it may be structurally and/or
compositionally similar to the C-type asteroid Mathilde, whose density
was determined from the flyby of the NEAR spacecraft to be 1.3 g cm(-3)
. We discuss the implications of these findings for the composition and
structure of Eugenia and for the mechanisms for satellite formation. We
place these findings in the context of an additional 25 asteroids for
which we have similar data, and in the context of asteroid families
and taxonomic types. These observations were made using near-infrared
(H-band at 1.65 mu ) direct imaging, with the adaptive optics system
(PUEO) of the 3.6-m Canada-France-Hawaii Telescope (CFHT) on Mauna
Kea. This is the first positive detection from a comprehensive program,
funded by NASA and NSF, to survey up to 200 asteroids for the presence
of companions. The program is carried out using the adaptive optics
systems of CFHT and the Mt. Wilson 100" telescope.
---------------------------------------------------------
Title: Images of Neptune's ring arcs obtained by a ground-based
telescope
Authors: Sicardy, B.; Roddier, F.; Roddier, C.; Perozzi, E.; Graves,
J. E.; Guyon, O.; Northcott, M. J.
1999Natur.400..731S Altcode:
Neptune has a collection of incomplete narrow rings, known as
ring arcs, which should in isolation be destroyed by differential
motion in a matter of months. Yet since first discovered by stellar
occultations in 1984, they appear to have persisted, perhaps through a
gravitational resonance effect involving the satellite Galatea. Here
we report ground-based observations of the ring arcs, obtained using
an adaptive optics system. Our data, and those obtained using the
Hubble Space Telescope (reported in a companion paper), indicate that
the ring arcs are near, but not within the resonance with Galatea,
in contrast to what is predicted by some models.
---------------------------------------------------------
Title: Filling Factor and Signal-to-Noise Ratios in Optical
Interferometric Arrays
Authors: Roddier, François; Ridgway, Stephen T.
1999PASP..111..990R Altcode:
Signal-to-noise ratios are derived for an interferometric array of
N diffraction-limited optical/IR telescopes with a Fizeau-type beam
recombination. We consider two types of objects-extended sources and
point sources-and three sources of noise-signal photon noise, sky
background noise, and detector noise. We compare the results with that
of a filled aperture, and also to that of an incoherent array, each
with the same total collecting area. Implications are briefly discussed.
---------------------------------------------------------
Title: S/1998 (45) 1
Authors: Merline, W. J.; Close, L. M.; Dumas, C.; Chapman, C. R.;
Roddier, F.; Menard, F.; Slater, D. C.; Duvert, G.; Shelton, C.;
Morgan, T.; Dunham, D. W.
1999IAUC.7129....1M Altcode: 1999IAUC.7129Q...1M; 1999IAUC.7129A...1M
W. J. Merline, Southwest Research Institute, Boulder, reports for a
large collaboration (including L. M. Close, C. Dumas, C. R. Chapman,
F. Roddier, F. Menard, D. C. Slater, G. Duvert, C. Shelton, and
T. Morgan) the discovery of a satellite of (45) Eugenia on 1998
Nov. 1.5 UT from H-, J-, and K'-band direct imaging with the 3.6-m
Canada-France-Hawaii Telescope (+ PUEO adaptive- optics system) on
Mauna Kea. The satellite is about 6 mag fainter than (45) and was
tracked intermittently on five nights over a 10-day span. Merline
et al. derive a near-circular orbit with a period of about 4.7
days, inclined to the line-of-sight by about 45 deg, with a maximum
elongation of about 0".8. The satellite was recovered with the CFHT on
1999 Jan. 4. An occultation around Mar. 27.13 of the star CMC 804951
(mag 11.9) by (45) was predicted by D. W. Dunham, but this is likely
to be visible only near the earth's north-polar regions (see updates
at http://members.home.net/dega/astchart.htm).
---------------------------------------------------------
Title: Rings of Neptune
Authors: Roddier, C.; Roddier, F.; Graves, J. E.; Guyon, O.; Northcott,
M. J.; Sicardy, B.
1999IAUC.7108....3R Altcode: 1999IAUC.7108C...1R; 1999IAUC.7108S...1R
C. Roddier, F. Roddier, J. E. Graves, O. Guyon, and M. J. Northcott,
Institute for Astronomy, University of Hawaii (UH); and B. Sicardy,
Paris Observatory, report: "Infrared (1.72-micron) images of Neptune
taken on 1998 July 6 with the UH adaptive optics system (Hokupa'a)
mounted on the Canada-France-Hawaii 3.6-m telescope have been studied
further. In addition to the observations of Neptune arcs reported on
IAUC 7051, evidence is now found for another ring structure even closer
to Neptune. Its radial distance is that of the Le Verrier ring. It
is visible only on the west ansa, and its brightness is roughly twice
that of the Adams arcs."
---------------------------------------------------------
Title: Ground-Based Interferometry with Adaptive Optics
Authors: Roddier, F.
1999ASPC..194..318R Altcode: 1999wfoi.conf..318R
Adaptive optics now routinely produces high dynamic range
diffraction-limited images on ground-based telescopes using
guide sources as far as 10 to 15 arcsec away from the object of
interest. The same principles and techniques apply to telescope
arrays. A dual-beam interferometer would allow the use of a bright
guide source to compensate the wave-front and track the fringes,
while observing much fainter nearby sources. Even a single beam
interferometer should also have two channels, one for wave-front
control, and another one for science. A dichroic beam splitter is
then used to separate the two beams. Wave-front control is done
with low-noise, fast parallel read-out detectors collecting photons
over a very wide spectral band. Wave-front `curvature' sensing is
particularly attractive to control an array of telescopes. This can
be done by using a single membrane modulator as a common reference,
but several detector arrays (one per telescope). In this case, closing
the loop will automatically co-align and co-focus all the telescopes
as if it were a single aperture. Co-phasing the array still requires
an additional sensor (fringe tracker) to sense the wave-front `piston'
modes. Because most of the scientific information is obtained under
very low fringe visibilities, fringe tracking must be done either
at a longer wavelength or - in case of an array - between adjacent
apertures. The co-phasing of a large array then becomes the adaptive
optics equivalent of reconstructing the wave-front phase from an array
of phase differences. Once individual wave-fronts are compensated,
co-focused, co-aligned, and co-phased, then it becomes possible to
record long exposure interferograms for science applications.
---------------------------------------------------------
Title: Adaptive Optics Imaging of Solar System Objects
Authors: Roddier, Francois; Owen, Toby
1999STIN...0025316R Altcode:
Most solar system objects have never been observed at wavelengths
longer than the R band with an angular resolution better than 1". The
Hubble Space Telescope itself has only recently been equipped to
observe in the infrared. However, because of its small diameter, the
angular resolution is lower than that one can now achieved from the
ground with adaptive optics, and time allocated to planetary science
is limited. We have successfully used adaptive optics on a 4-m class
telescope to obtain 0.1" resolution images of solar system objects in
the far red and near infrared (0.7-2.5 microns), aE wavelengths which
best discl"lmlnate their spectral signatures. Our efforts have been put
into areas of research for which high angular resolution is essential.
---------------------------------------------------------
Title: Planetary Science with Adaptive Optics: Results from the UH
AO Systems
Authors: Roddier, F.; Roddier, C.; Close, L.; Dumas, C.; Graves, J. E.;
Guyon, O.; Han, B.; Northcott, M. J.; Owen, T.; Tholen, D.; Brahic, A.
1999ESOC...56..401R Altcode: 1999aaop.conf..401R
No abstract at ADS
---------------------------------------------------------
Title: Future expectations
Authors: Roddier, F.
1999aoa..book..399R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The UH-CFHT systems
Authors: Roddier, F.; Rigaut, F.
1999aoa..book..205R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Adaptive Optics J Band Imaging Polarimetry Observations of
the Circumbinary Disk Around UY Aurigae
Authors: Potter, D. E.; Close, L. M.; Roddier, F.; Roddier, C.;
Graves, J. E.; Northcott, M.
1999ESOC...56..353P Altcode: 1999aaop.conf..353P
No abstract at ADS
---------------------------------------------------------
Title: Four-Year Observations of T Tauri With Adaptive Optics
Authors: Roddier, C.; Roddier, F.; Graves, J. E.; Northcott, M. J.;
Close, L.; Surace, J.; Veran, J. P.
1999ESOC...56..389R Altcode: 1999aaop.conf..389R
No abstract at ADS
---------------------------------------------------------
Title: The Nulling Coronograph
Authors: Guyon, O.; Roddier, C.; Elon Graves, J.; Roddier, F.;
Cuevas, S.; Espejo, C.; Martinez, A.; Gonzales, S.; Bisiacchi, G.;
Vuntersmeri, V.
1999ESOC...56..537G Altcode: 1999aaop.conf..537G
No abstract at ADS
---------------------------------------------------------
Title: Theoretical aspects
Authors: Roddier, F.
1999aoa..book...25R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Historical context
Authors: Roddier, F.
1999aoa..book....3R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The nulling coronagraph applied to interferometric arrays
Authors: Guyon, O.; Roddier, F.
1999ASPC..194..201G Altcode: 1999wfoi.conf..201G
The nulling stellar coronagraph, first proposed by Roddier and Roddier
(PASP 109, p. 815, 1997), uses a small phase mask to shift by 180
degrees the phase of the central part of the Airy spot. This leads to
destructive interference which strongly attenuates the central Airy spot
as well as the rings, as demonstrated by the result of an experiment
we carried out on an optical bench (Guyon et al., PASP submitted). The
nulling coronagraph can also be used on an interferometric array by
first densifying the entrance pupil (Labeyrie, A&A Supl., 118,
p. 517, 1996). The pupil is then rediluted to avoid the narrowing of the
field of view. This is the only known nulling technique that produces a
true undisturbed image with the central bright star removed. Numerical
simulations allow us to evaluate the performance of this nulling
technique with different geometrical configurations of subapertures.
---------------------------------------------------------
Title: Imaging through the atmosphere
Authors: Roddier, F.
1999aoa..book....9R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Adaptive optics in astronomy
Authors: Roddier, Francois
1999aoa..book.....R Altcode:
Adaptive optics is a powerful new technique used to sharpen telescope
images blurred by the Earth's atmosphere. This authoritative book is
the first dedicated to the use of adaptive optics in astronomy. Mainly
developed for defence applications, the technique of adaptive optics
has only recently been introduced in astronomy. Already it has allowed
ground-based telescopes to produce images with sharpness rivalling
those from the Hubble Space Telescope. The technique is expected to
revolutionise the future of ground-based optical astronomy. Written by
an international team of experts who have pioneered the development of
the field, this timely volume provides both a rigorous introduction
to the technique and a comprehensive review of current and future
systems. It is set to become the standard reference for graduate
students, researchers and optical engineers in astronomy and other areas
of science where adaptive optics is finding exciting new applications.
---------------------------------------------------------
Title: Astronomy with Adaptive Optics: Experiences from the University
of Hawaii AO Program
Authors: Close, L. M.; Roddier, F.; Potter, D.; Roddier, C.; Graves,
J. E.; Northcott, M.
1999ESOC...56..109C Altcode: 1999aaop.conf..109C
No abstract at ADS
---------------------------------------------------------
Title: NOTE: Neptune's Cloud Structure and Activity: Ground-Based
Monitoring with Adaptive Optics
Authors: Roddier, F.; Roddier, C.; Graves, J. E.; Northcott, M. J.;
Owen, T.
1998Icar..136..168R Altcode:
Since August 1995, near-infrared images of Neptune have regularly been
obtained with the University-of-Hawaii telescope. These images reveal
Neptune's cloud structure with an angular resolution reaching 0.12″
in the H band.
---------------------------------------------------------
Title: Discovery of an Arc of Particles near Enceladus' Orbit:
A Possible Key to the Origin of the E Ring
Authors: Roddier, C.; Roddier, F.; Graves, J. E.; Northcott, M. J.
1998Icar..136...50R Altcode:
High angular resolution (adaptive optics) images taken on August 12,
1995 between 11:26 and 12:23 (UT) show a faint elongated structure
apparently moving away from Saturn. The structure is consistent with
light scattered by an arc of particles on a Keplerian orbit close
to that of Enceladus. The orbit is slightly inclined (1.8°), and
the arc is 76° ahead of the satellite. It appears to be a transient
phenomenon since the arc brightness decreased by almost a factor two
during the observations, and no such structure was observed at the
same orbital position two days before. A possible explanation is that
a large block of ice previously ejected by Enceladus collided with ice
fragments trapped on the satellite orbit near its L<SUB>4</SUB>Lagrange
point. The collision likely occurred about 6 h before observations
started and produced a rapidly expanding cloud of small particles. We
estimate the total mass of particles to be at least 10<SUP>5</SUP>kg.
---------------------------------------------------------
Title: Satellites and Rings of Neptune
Authors: Roddier, C.; Roddier, F.; Graves, J. E.; Guyon, O.; Northcott,
M. J.; Sicardy, B.
1998IAUC.7051....1R Altcode: 1998IAUC.7051Q...1R
C. Roddier, F. Roddier, J. E. Graves, O. Guyon, and M. J. Northcott,
Institute for Astronomy, University of Hawaii (UH); and B. Sicardy,
Paris-Meudon Observatory, report: "Infrared (1.72- micron) images of
Neptune taken on July 6 with the UH adaptive optics system (Hokupa'a)
mounted on the Canada-France-Hawaii 3.6-m telescope have now been
thoroughly processed. In addition to the observations of Neptune
VI (Galatea), VII (Larissa), and VIII (Proteus) reported on IAUC
6987, Neptune V (Despina) and Neptune's ring arcs have also been
detected. Despina, which was far from maximum elongation, moved
substantially during the 600-s exposure time, but its average position
is consistent within +/- 1 deg of that estimated from Voyager 2 data
in 1989 (as for Proteus and Larissa). Each of the three brightest arcs
Liberte, Egalite, and Fraternite are identified. The fainter leading
arc Courage cannot be confirmed. The positions of the main arcs are
close to that given by the second orbital solution of Nicholson et
al. (1995, Icarus 113, 295), which corresponds to a mean motion of
820.1118 deg/day. Photometric profiles of the arcs have been obtained
and compared with those of Porco (1991, Science 253, 995), allowing for
the blur due to our 600-s integration time. For the two trailing arcs
(Fraternite and Egalite), the fit is very good. It shows that the arcs
are 4 +/- 2 deg ahead of the position estimated from Nicholson's second
solution. For Liberte the uncertainty is larger due to noise. Four
200-s exposures made in the J band were also analyzed. The arcs were
not detected. However, the data confirm that Galatea is 5 +/- 1 deg
ahead of the nominal predicted position (IAUC 6987). In these data,
Despina is closer to maximum elongation. Its image is sharper and its
position is again consistent within +/- 1 deg with that predicted from
Voyager data. We note that the uncertainties in the orbital parameters
derived from Voyager data by Owen et al. (1991, A.J. 101, 1511) lead to
the following standard errors on the current satellite longitudes: +/-
2.9 deg for Proteus, +/- 5.2 deg for Larissa, +/- 9.1 deg for Despina,
and +/- 8.1 deg for Galatea. The estimated errors are believed to be
conservative by typically a factor of two (ibid.). Further analysis
is thus required to see if the Galatea O-C is significant or a mere
effect of the accumulation of error between 1989 and 1998."
---------------------------------------------------------
Title: University of Mexico adaptive optics program
Authors: Cuevas, Salvador; Sotelo, Pablo D.; Garfias, Fernando;
Iriarte, Arturo; Martinez, Luis A.; Orlov, Valeri G.; Voitsekhovich,
Valeri V.; Chapa, O.; Tinoco, Silvio J.; Vernin, Jean; Avila, Remy;
Marchis, Franck; Graves, J. Elon; Northcott, Malcolm J.; Roddier,
Francois J.; Roddier, Claude A.
1998SPIE.3353..531C Altcode:
We describe different works conducing to the adaptive optics system
for the TIM 6.5m telescope. We show turbulence profiles result at our
San Pedro Martir Observatory in Baja using the Generalized SCIDAR. We
can conclude that the turbulence conditions in this site are comparable
to the major observatories in the world. From these results and taken
in account curvature AO simulations it is possible to predict the
performances in limiting magnitude and sky coverage of different AO
systems and telescopes in our observatory. We can also define the
degree of the AO system for the TIM 6.5m telescope. We made a short
description of our LOLA tip-tilt corrector system and the GUIELOA 19
elements curvature AO system. The calculation of the optics quality
for the TIM 6.5m is briefly mentioned. Studies about the influence of
the finite outerscale on the optical quality of AO corrected images
are described.
---------------------------------------------------------
Title: Wavefront curvature sensing on extended arbitrary scenes:
simulation results
Authors: Kupke, Renate; Roddier, Francois J.; Mickey, Donald L.
1998SPIE.3353..918K Altcode:
We describe and evaluate the performance of a wavefront sensor based
on curvature sensing which can be used to detect static aberrations
given an extended reference source. The description includes a full
mathematical treatment of the sensor signal, as well as how this
signal is relate to the Laplacian of the wavefront. Evaluation of
the technique is performed with computer simulations. A Monte-Carlo
simulation is utilized to evaluate the performance of the technique
in the presence of noise. The sensor was found to provide accurate
measurement of the wavefront coefficients on high-contrast extended
objects. It behaves well in the presence of a field stop, and in the
presence of additive Gaussian noise.
---------------------------------------------------------
Title: First light for Hokupa'a: 36-element curvature AO system at UH
Authors: Graves, J. Elon; Northcott, Malcolm J.; Roddier, Francois J.;
Roddier, Claude A.; Close, Laird M.
1998SPIE.3353...34G Altcode:
The University of Hawaii adaptive optics program has scaled its
previously successful 13 elements AO system to 36 actuators and named
it 'Hokupa'a', meaning 'immovable star' in Hawaiian. First light for
Hokupa'a in early November of 1997, was on the Canada France Hawaii
Telescope on Mauna Kea, an f/35, 3.35 meter telescope. Performance
at the telescope has now been measured and compares favorably with
that predicted theoretically. The extension to 36 elements has now
allowed the system to give diffraction limited performance down to
I band on stars as faint as 12.5 magnitude in median 0.7 arcsecond
seeing on Mauna Kea. Like our previous system, extensive computer
simulations were carried out to achieve the best possible match between
the curvature WFS and the deformable curvature mirror.
---------------------------------------------------------
Title: Scientific results from the University of Hawaii: adaptive
problems well suited to AO techniques
Authors: Close, Laird M.; Roddier, Francois J.; Roddier, Claude A.;
Graves, J. Elon; Northcott, Malcolm J.; Potter, Dan
1998SPIE.3353..406C Altcode:
The University of Hawaii AO group has been actively carrying out
astronomical AO observations for the last four years. The UHAO group
and out collaborators have utilized the curvature AO system to obtain
diffraction-limited images of asteroids, planets, moons, protoplanetary
disks, young stars, young star clusters, planetary nebulae, black
holes, galaxies and quasars. The current scientific capabilities
of the new 36-actuator Hokupa'a AO curvature system will be briefly
reviewed. Four key astronomical situations that are excellent for AO
observations will be discussed. Examples of scientific observational
techniques will be highlighted with actual AO astronomical results.
---------------------------------------------------------
Title: Satellites of Neptune
Authors: Roddier, C.; Roddier, F.; Graves, J. E.; Guyon, O.; Northcott,
M. J.
1998IAUC.6987....2R Altcode: 1998IAUC.6987B...1R; 1998IAUC.6987R...1R
C. Roddier, F. Roddier, J. E. Graves, O. Guyon, and M. J. Northcott,
Institute for Astronomy, University of Hawaii (UH), report: "Infrared
(1.72-micron) images of Neptune were taken on July 6 with the UH
adaptive optics system (Hokupa'a) mounted on the Canada-France-Hawaii
telescope. Neptune VIII (Proteus), VII (Larissa), and VI (Galatea) were
detected and observed from July 6.490 to 6.552 UT. Whereas Proteus and
Larissa were found to be at their expected position, Galatea was found
to be 5 +/- 1 degrees ahead of the predicted position (8.6 min early),
a difference possibly due to its interaction with Neptune's Adams ring
(cf. Ferrari and Brahic 1994, Icarus 111, 193; Hanninen and Porco 1997,
Icarus 126, 1)."
---------------------------------------------------------
Title: Maximum Gain and Efficiency of Adaptive Optics Systems
Authors: Roddier, François
1998PASP..110..837R Altcode:
A definition is given for the efficiency of an adaptive optics (AO)
system. An expression is derived that allows the efficiency of an AO
system to be simply estimated. Estimates are derived for the efficiency
of several AO systems currently used in astronomy. The advantages of
building high-efficiency systems are emphasized.
---------------------------------------------------------
Title: Adaptive Optics Imaging of the Circumbinary Disk around the T
Tauri Binary UY Aurigae: Estimates of the Binary Mass and Circumbinary
Dust Grain Size Distribution
Authors: Close, L. M.; Dutrey, A.; Roddier, F.; Guilloteau, S.;
Roddier, C.; Northcott, M.; Ménard, F.; Duvert, G.; Graves, J. E.;
Potter, D.
1998ApJ...499..883C Altcode:
We have obtained high-resolution (FWHM = 0.15") deep images of the UY
Aur binary at J, H, and K' with the University of Hawaii adaptive optics
instrument. We clearly detect an R ~ 500 AU circumbinary disk discovered
with millimeter interferometry, making UY Aur the second young binary
with a confirmed circumbinary disk. It appears that the disk is inclined
~42° from face on. We find that the near side of the disk is brighter
than the far side by factors of 2.6, 2.7, and 6.5 times at K', H, and J,
respectively. The original GG Tau circumbinary disk has been reexamined
and is found to have similar flux ratios of 1.5, 2.6, and 3.6 at K',
H, and J, respectively. A realistic power-law distribution (p = 4.7)
of spherical dust aggregates (composed of silicates, amorphous carbon,
and graphite) that reproduces the observed ISM extinction curve also
predicts these observed flux ratios from Mie scattering theory. We find
the observed preference of forward-scattering over back-scattering is
well fitted (global χ<SUP>2</SUP> minimization) by Mie scattering off
particles in the range a<SUB>min</SUB> = 0.03 μm to a<SUB>max</SUB> =
0.5-0.6 μm. The existence of a significant population of grain radii
larger than 0.6 μm is not supported by the scattering observations. <P
/>Based on the observed disk inclination we derive an orbit for UY Aur
where the mass for the binary is 1.6<SUP>+0.47</SUP><SUB>-0.67</SUB>
M<SUB>⊙</SUB>. Based on the observed K7 and M0 spectral types for
UY Aur A and B, accretion disk models for the inner disks around the
central stars were constructed. The models suggest that small (lower
limit R ~ 5-10 AU) inner disks exist around B and A. It appears that B
is accreting ~5 times faster than A, and that both inner disks may be
exhausted in ~10<SUP>2</SUP>-10<SUP>3</SUP> yr without replenishment
from the outer circumbinary disk. Our images suggest that these inner
disks may indeed be resupplied with material through thin streamers
of material that penetrate inside the circumbinary disk. Currently it
appears that such a streamer may be a close to UY Aur B. Comparison of
our IR images and the millimeter images of the gas clearly show that
the dust seen in our IR images traces the gas in the circumbinary disk,
as was also the case with GG Tau.
---------------------------------------------------------
Title: Adaptive Optics Provides a Sharp Image of Io's Volcanoes
Authors: Dumas, C.; Close, L.; Graves, B.; Northcott, M.; Roddier,
F.; Hainaut, O.; Connelley, M.
1998BCFHT..38...26D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Model of Scattering from Dust in Proto-planetary Disks
applied to O.1" resolution U. of Hawaii Adaptive Optics Images of
the Disk around Young Stars
Authors: Potter, D. E.; Close, L.; Roddier, F.
1997AAS...191.0503P Altcode: 1997BAAS...29.1213P
We present a method for using the infrared extinction profile and
observed scattered infrared radiation from dust in proto-planetary
disks to obtain constraints on the dust grain size distribution,
density profile, inclination, and extent of the disk. Our method
utilizes a Mie scattering algorithm which calculates the exact
scattering angle probabilities for light incident on a homogeneous
sphere. The dielectric properties of the dust used in the modeling
are that of a realistic mix of silicate, amorphous carbon, graphite,
and vacuum. The code produces disk images and extinction values
from given inclination angles, dust size and density distributions,
wavelengths, and flaring profiles. Parameter fitting routines can thus
be carried out between these models and high resolution observations
to constrain the parameter values of the observed disks. The recently
obtained University of Hawaii adaptive optics images of UY Aur and GG
Tau resolve circumbinary disks in both systems. We apply our method
to the intensity distributions revealed by the images to constrain the
particle size distributions and densities for both systems. We obtain
good fits to both the extinction profile and the observed intensity
variations on the front and back side of the disk with a rather steep
( ~ -4.7) power law distribution and a range of dust sizes ranging
from 0.03 and 0.6 microns. A significant population of grains larger
than 0.6 microns is not supported by the observations.
---------------------------------------------------------
Title: Adaptive Optics Infrared Imaging Polarimetry and Optical
HST Imaging of Hubble's Variable Nebula (R Monocerotis/NGC 2261):
A Close Look at a Very Young Active Herbig Ae/Be Star
Authors: Close, L. M.; Roddier, F.; Hora, J. L.; Graves, J. E.;
Northcott, M.; Roddier, C.; Hoffman, W. F.; Dayal, A.; Fazio, G. G.;
Deutsch, L. K.
1997ApJ...489..210C Altcode:
We present high-resolution (FWHM = 0.2") near-IR (J, H, and K')
adaptive optics images of the Herbig Ae/Be star R Monocerotis. Optical
Hubble Space Telescope (HST) WFPC2 PC camera archival images are
also presented. For the first time, adaptive optics was utilized to
make high-resolution (FWHM = 0.2") IR-imaging polarimetry maps of R
Mon. In addition, the first mid-IR array images (at 11.7 and 20.8 μm)
of R Mon have been obtained. We also present new 3.16, 3.93, and 4.67
μm images. <P />We have found that R Mon is a 0.69" binary star with
a companion that dereddens onto the classical T Tauri locus. Based on
the near-infrared photometry of this companion we believe it is a 1.5
M<SUB>⊙</SUB>, very young (<3 × 10<SUP>5</SUP> yr) classical T
Tauri star. The close presence of a young companion suggests that R
Mon itself is a rare example of a very young isolated massive star. <P
/>At the highest resolutions, R Mon is revealed to be extended by ~0.1"
east-west, and ~0.05" north-south in the visible. The young R Mon star
is not directly visible in the optical but appears as a resolved conical
reflection nebula in scattered light. At infrared wavelengths, the dense
circumstellar dust is penetrated and R Mon appears to be an unresolved
point source located at 0.06" +/- 0.02" south of the peak optical
flux. <P />The large-scale optical-IR morphology of R Mon and its large
reflection nebula (NGC 2261) suggests a thin bipolar parabolic shell
of dust. The appearance of the parabolic shell is consistent with an
inclination of 20° +/- 10° from the plane of the sky. This inclination
implies that R Mon is located 760<SUP>+800</SUP><SUB>-280</SUB> pc
distant based on previous proper-motion and radial velocity measurements
of R Mon's jet. Our high-resolution (FWHM ~ 0.2") adaptive optics
infrared polarimetry maps agree with the current interpretation that
NGC 2261 is a reflection nebula illuminated by R Mon. <P />Interior to
the parabolic shell there is a complex of twisted filaments along the
eastern edge. These filaments resemble a double-helical structure which
is well described by a power law from ~10<SUP>3</SUP> to 10<SUP>5</SUP>
AU from R Mon. This double helix may trace a twisted magnetic field
above R Mon. <P />Based on H I emission-line ratios, we find the
direct extinction toward R Mon to be A<SUB>V</SUB> = 13.1 mag in the
infrared (λ > 1.28 μm), falling to a lower value of A<SUB>V</SUB>
= 3.6 mag in the optical (λ < 1.28 μm), where scattered light
increasingly lowers the effective extinction in the line ratios. The
large A<SUB>V</SUB> = 13.1 extinction is likely due to the dusty
atmosphere of an inclined R ~ 100 AU optically thick accretion disk
surrounding R Mon. A simple model of such an accretion disk + star
system (with M<SUB>acc</SUB> ~ 8 × 10<SUP>-5</SUP> M<SUB>⊙</SUB>
yr<SUP>-1</SUP>, M<SUB>*</SUB> = 10.4 M<SUB>⊙</SUB>, R<SUB>*</SUB>
= 2 R<SUB>⊙</SUB>, and T<SUB>*</SUB> ~ 3.5 × 10<SUP>4</SUP> K)
reproduces the observed dereddened R Mon spectral energy distribution
(SED) from the optical (0.4 μm) to the millimeter region. Consideration
of the lower extinction (A<SUB>V</SUB> = 3.6) on the path followed by
the scattered visible light eliminated any need for an inner “gap”
in the accretion disk model to reproduce the SED. <P />In general,
young stellar objects (YSOs) that are obscured in the optical but
directly visible in the infrared will have different effective optical
and infrared extinctions. Infrared extinctions derived from optical
observations dominated by scattered light will be underestimates of
the true IR extinction along the direct path. The use of an independent
estimator of both the optical and infrared extinctions such as common
upper-level H I recombination lines is highly desirable. The utilization
of the correct optical and infrared extinctions may relieve the need
for optically thin inner-disk gaps to explain YSO near-IR SEDs.
---------------------------------------------------------
Title: First ground-based adaptive optics observations of Neptune
and Proteus
Authors: Roddier, F.; Roddier, C.; Brahic, A.; Dumas, C.; Graves,
J. E.; Northcott, M. J.; Owen, T.
1997P&SS...45.1031R Altcode:
High angular resolution (0.15″) K-band images of Neptune were obtained
in August 1995, with the University-of-Hawaii adaptive optics system
mounted on the 3.6m Canada-France-Hawaii telescope. The images show
bright high contrast features that are believed to be high altitude
clouds. They confirm that low latitude (<30°) cloud activity has
shifted since Voyager from the south hemisphere to the north hemisphere,
whereas higher latitude activity seems more permanent. Proteus can be
seen at the locations predicted from Voyager data. Its K-magnitude is
19.0±0.03. The corresponding geometrical albedo is identical to that
measured in the visible by Voyager.
---------------------------------------------------------
Title: Saturn
Authors: Roddier, C.; Roddier, F.; Graves, J. E.; Northcott, M. J.
1997IAUC.6697....1R Altcode:
C. Roddier, F. Roddier, J. E. Graves and M. J. Northcott, Institute
for Astronomy, University of Hawaii (UH), report: "Infrared images of
Saturn's rings were taken on 1995 Aug. 12 with the UH adaptive-optics
system mounted on the Canada-France-Hawaii telescope. After careful
processing, evidence was found for a faint streak of light moving
away from Saturn at the level of the E ring. The object is elongated
in the direction of Saturn with a sharp edge on Saturn's side and a
fuzzy tail on the other side. Assuming motion on a keplerian orbit,
the object's orbital radius must be within a few km of that of Saturn
II (Enceladus). The object's sharp edge is ahead of Enceladus by an
orbital longitude of 75 deg. Its orbit is inclined by about 2 deg
with respect to the ring plane. The object could possibly be an arc
structure confined by gravitational interaction with both Saturn I
(Mimas) and Enceladus."
---------------------------------------------------------
Title: Azimuthal distribution of arcs and clumps in the F ring of
Saturn during August 1995 ring plane crossing.
Authors: Ferrari, C.; Brahic, A.; Charnoz, S.; Thebault, P.;
Roddier, F.
1997DPS....29.1703F Altcode: 1997BAAS...29..998F
Ground-based observations of the August 1995 Saturn's ring plane
crossing with the University of Hawaii Adaptive Optics System
have led to the discovery of several new objects orbiting around
the planet. Their orbits are known with variable accuracy but most
of them are compatible with the F ring. Some of these objects are
clearly azimuthally elongated structures, possibly arcs, the others
are not resolved. Planetary arcs are swarms of clumps, which largest
particles are most probably unresolved kilometer-sized objects (Ferrari
and Brahic, 1992, 1994, 1997). Are these objects evolving with time
? On which timescale ? The F ring arcs have been first observed
during the Voyager encounters. New constraints on the evolution of
the brightest of them, on a two-weeks timescale, at the epoch of the
Voyager 2 flyby, are presented. A revised orbit of the F ring is used
to derive an azimuthal distribution of the newly discovered objects at
August 1995 epoch. This is compared with the azimuthal profile of the
F ring observed three months later, during the Sun ring plane crossing
(Nicholson et al., 1996). The possible nature and lifetime of these
new objects is discussed.
---------------------------------------------------------
Title: Stellar Coronograph with Phase Mask
Authors: Roddier, F.; Roddier, C.
1997PASP..109..815R Altcode:
The detection of faint light sources very close to a bright star is
primarily limited by light scattered by the Earth's atmosphere. This
source of scattered light can now be reduced by means of adaptive
optics, or totally eliminated by using a telescope in space. Then
diffraction by the telescope aperture becomes the primary source of
scattered light. Whereas a classical Lyot coronograph can reduce
the amount of light diffracted away from the star, it becomes
inefficient very close to the star. Instead of forming the stellar
image on an opaque mask, it is proposed here to use a small phase
plate which produces a 180 degrees phase shift on the core of the
stellar image. Light diffracted outside the core is then eliminated
by destructive interference. Applied to the Hubble Space Telescope,
the technique would easily allow detection of a stellar companion
0.3" away from a star and at least 8 magnitude fainter. (SECTION:
Astronomical Instrumentation)
---------------------------------------------------------
Title: Environment of young stars: from adaptive optics to telescope
arrays.
Authors: Roddier, F.
1997CRASB.325...35R Altcode:
Protoplanetary disks around young stars can now be observed with a
0.1″angular resolution using adaptive optics. These observations
bring a new vision of the primordial solar nebula. Unfortunately,
the close surroundings of the star are masked by its glare. A new
stellar coronagraph with a phase mask should enable one to observe much
closer to the central star. The technique applies to images produced
by telescope arrays. It could allow to detect planets at distances as
close as that between the Earth and the Sun.
---------------------------------------------------------
Title: Adaptive optics observations of solar system objects
Authors: Roddier, F.; Brahic, A.; Dumas, C.; Graves, J. E.; Han, B.;
Northcott, M. J.; Owen, T.; Roddier, C.
1997DPS....29.2701R Altcode: 1997BAAS...29.1023R
Diffraction-limited images can now be obtained from the ground using
adaptive optics. We present here a number of results obtained with
this technique by researchers at the Institute for Astronomy. These
include: 1) Observations of the rings of Saturn as the Earth was
crossing the ring plane in August 95. Evidence was found for a
dozen of 20- to 40-km diameter objects, probably clumps, orbiting
at the distance of the F-ring. Among these objects two of them have
been identified with objects 1995 S5 and S7 observed by the Hubble
Space Telescope. An eclipse of Epimetheus by the F ring was observed,
putting new constraints on its orbit as well as the size and density of
the F ring. Photometric profiles have been obtained along the rings,
and their time evolution has been modeled. 2) Observations of Titan
through narrowband filters in and out of the 1.6 micron methane
window. The surface feature observed by Smith et al and Combes et
al on the leading hemisphere has been detected as well, albeit with
morphological differences. A program of adaptive-optics observations of
Titan is under way. 3) K-band observations of Uranus and its rings. Puck
has been detected. 4) K-band observations of Neptune, confirming that
low-latitude cloud activity has shifted from the south to the north
hemisphere since Voyager observations. For the first time Proteus
was detected from Earth and its albedo was measured at 2.2 mu m. 5)
Wide band observations of Pluto and Charon. A program of narrow band
photometry of the individual components is under way. 6) Observations
of asteroid 4 Vesta during its 1996 opposition through narrow band
filters in and out the pyroxene bands. Its dimensions and shape as
well as the nature of the geological units present on its surface,
have been derived.
---------------------------------------------------------
Title: Adaptive Optics 0.2" Resolution Infrared Images of HL Tauri:
Direct Images of an Active Accretion Disk around a Protostar
Authors: Close, Laird M.; Roddier, François; J. Northcott, Malcolm;
Roddier, Claude; Elon Graves, J.
1997ApJ...478..766C Altcode:
We have obtained 0.2" FWHM images of HL Tau at K', H, and J utilizing
the University of Hawaii Adaptive Optics System at the 3.6 m CFHT. These
are the highest resolution deep images of HL Tau ever obtained in
the infrared. They provide unique insight into HL Tau's circumstellar
environment. An active accretion disk is directly resolved around HL
Tau for the first time in the infrared. The physical characteristics
of this accretion disk (R<SUB>D</SUB> ~ 150 AU, and P.A. ~ 125°)
are consistent with the inner disk discovered by submillimeter (0.8
mm) interferometry by Lay et al. (1994), and confirmed by 2.7 mm
interferometry by Mundy et al. (1996). <P />Bipolar cavities aligned
with the accretion disk axis are for the first time detected in the
infrared. We have monitored the upper cavity at comparable angular
resolution for three epochs over the last 2 yr. The cavity appears to
be expanding at up to ~30 km s<SUP>-1</SUP>. This cavity is estimated
to have been created in an outburst in the direction of the optical
jet ~100 yr ago. <P />Accurate photometry and astrometry were obtained
for the nearby 0.3" XZ Tau binary and the unresolved HL Tau star +
inner disk at K', H, and for the first time at J. The large H - K =
2.14 +/- 0.11 color of the HL Tau point source indicates an extinction
of A<SUB>J</SUB> = 7.73 +/- 0.42 (A<SUB>V</SUB> ~ 24) along the line
of sight to the star. Based on this large extinction, the SED for HL
Tau's unresolved central source was dereddened. A simple accretion
disk + star model reproduced the newly dereddened SED. The model
assumed a large infalling envelope (as observed in <SUP>13</SUP>CO; see
Hayashi et al. 1993) accreting at 5 × 10<SUP>-6</SUP> M<SUB>⊙</SUB>
yr<SUP>-1</SUP> onto a stable accretion disk (R<SUB>D</SUB> = 150 AU)
around a young 0.7 M<SUB>⊙</SUB> pre-main-sequence (PMS) star. We
find that to reproduce the observed SED, the central unresolved source
in HL Tau is required to be a very young (~10<SUP>5</SUP> yr) PMS star
surrounded by an active accretion disk. The large observed extinction
from the inclined disk implies an estimated accretion disk mass of
~0.04 M<SUB>⊙</SUB>.
---------------------------------------------------------
Title: Improved Imaging Performance of the NASA IRTF Telescope
Authors: Baron, R. L.; Joseph, R.; Tokunaga, A.; Onaka, P.; Smith,
S.; Young, T.; Roddier, F.; Roddier, C.; Hall, D.; Lin, Gang
1997AAS...18912101B Altcode: 1997BAAS...29..733B
Improved imaging of the NASA IRTF (Infrared Telescope Facility)
is being pursued intensely on a number of fronts. We report
initial results, direction for the next steps and current/expected
performance. Successful engineering and shared risk observations have
been made with a tip-tilt secondary and fast loop control system. Near
diffraction limited images (at 2.2 microns and longer wavelengths)
with effective exposures of minutes have been taken. Telescope
optics are being evaluated and alignment errors minimized using this
instrument. The system is still under development and with completion
of this work we expect this performance to be available to a large
user community.
---------------------------------------------------------
Title: Satellites of Saturn
Authors: Roddier, C.; Roddier, F.; Brahic, A.; Graves, J. E.;
Northcott, M. J.; Owen, T.
1996IAUC.6515....1R Altcode:
C. Roddier and F. Roddier, Institute for Astronomy (IfA), University
of Hawaii; A. Brahic, Observatoire de Paris; and J. E. Graves,
M. J. Northcott and T. Owen, IfA, report: "Images of Saturn's rings,
taken in Aug. 1995 with the University of Hawaii adaptive-optics
system mounted on the Canada-France-Hawaii telescope, have now been
deconvolved and carefully processed. They show evidence for at least
nine additional objects all orbiting in the F ring. A good orbital
fit (including the effects of the Saturnian J2 and J4 harmonics) was
obtained for all of them with a single distance of 140 500 +/- 500
km. The following list includes the three objects already announced
on IAUC 6407. As before, the longitudes (uncertainty +/- 1 deg) are
for the epoch 1995 Aug. 10.5 TT (at Saturn) and are measured from the
ascending node of Saturn's equator on the earth's J2000.0 equator:
S/1995 S 11, longitude 302 deg, estimated radius 12 km; S/1995 S 9,
317, 16; S/1995 S 12, 320, 10; S/1995 S 7 = 1995 S 8, 325, 20; S/1995
S 13, 330, 12; S/1995 S 14, 46, 16; S/1995 S 15, 105, 12; S/1995 S 16,
114, 10; S/1995 S 17, 116, 10; S/1995 S 18, 118, 10; S/1995 S 19, 120,
10; S/1995 S 5 = 1995 S 10, 131, 20. We also find some evidence for
S/1995 S 11, S/1995 S 15, S/1995 S 16 and S/1995 S 17 in the HST data
(cf. IAUC 6243). S/1995 S 12 is part of the possible S/1995 S 9 arc
structure mentioned on IAUC 6407, now resolved into two components;
we no longer see evidence for arc structures. The 12 objects listed
above cover a total longitude range of 135 deg. Assuming that objects
are uniformly distributed, one can estimate that the F ring contains
some 32 of them with radii larger than 10 km."
---------------------------------------------------------
Title: First infrared images of the GG Tau ring
Authors: Roddier, C.; Roddier, F.; Northcott, M. J.; Graves, J. E.
1996BCFHT..35....9R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Satellites of Saturn
Authors: Roddier, F.; Brahic, A.; Dumas, C.; Ferrari, C.; Graves,
J. E.; Northcott, M. J.; Owen, T.; Perret, L.; Roddier, C.; Thebault,
P.
1996IAUC.6407....1R Altcode:
F. Roddier, Institute for Astronomy, University of Hawaii (IfA);
A. Brahic, Observatoire de Paris and Universite de Paris (Paris);
C. Dumas, IfA; C. Ferrari, Paris; J. E. Graves, M. J. Northcott,
and T. Owen, IfA; L. Perret, Paris; C. Roddier, IfA; and P. Thebault,
Paris, report: "A new adaptive-optics system developed at the University
of Hawaii was operated at the 3.6-m Canada- France-Hawaii telescope
during four nights spanning the 1995 Aug. ring-plane crossing. Several
hundred 15-, 30-, and 60-s exposures were obtained in the bands I, J, H,
and K; the average angular resolution is 0".15 in the H band. Saturn X
(Janus), XI (Epimetheus), XII (Helene), XIII (Telesto), XIV (Calypso),
XV (Pandora), and XVI (Prometheus) were identified; positions are
in fair agreement with the new ephemerides deduced from Hubble Space
Telescope (HST) observations. Three additional objects --- S/1995 S 8,
S/1995 S 9, and S/1995 S 10 --- have been discovered. The number of
fitted observations is given below, followed by our estimate of the
equivalent orbital radius and longitude for epoch 1995 Aug. 10.5 TDT
(at Saturn), measured from the ascending node of Saturn's equatorial
plane on the earth's J2000.0 equator; the fits include the effects of
Saturnian J2 and J4 harmonics: S/1995 S 8, 16 observations, 141 400 +/-
1000 km, 323 +/- 1 deg; S/1995 S 9, 16, 141 400 +/- 2000 km, 315 +/-
1.8 deg; S/1995 S 10, 8, 140 050 +/- 100 km, 131.4 +/- 1.1 deg. S/1995
S 10 has been observed on both Aug. 9 and 10; it is co-orbital to the
F ring. This object is most probably the candidate satellite S/1995
S 5, which was observed by the HST on Aug. 10. S/1995 S 8 may be
identified with S/1995 S 7 observed by HST, since the observations are
consistent. The S/1995 S 9 azimuthal extent of 5 deg suggests an arc
structure, which may be embedded in the F ring; it cannot be linked
with any other objects discovered by HST at the same epoch."
---------------------------------------------------------
Title: Adaptive Optics Imaging of GG Tauri: Optical Detection of
the Circumbinary Ring
Authors: Roddier, C.; Roddier, F.; Northcott, M. J.; Graves, J. E.;
Jim, K.
1996ApJ...463..326R Altcode:
High angular resolution images of GG Tau have been obtained in the
I, J, H, and K bands with the University of Hawaii adaptive optics
system. The close binary pair is found to be near periastron,
and it rotates clockwise. It consists of a K7-M0 star with an M4
companion. Masses inferred from dynamical motion are larger than the
spectral type suggest. The companion appears to be younger than the
main star. Both stars seem to be surrounded with a warm unresolved
disk. Images reveal a circumbinary ring also recently detected at
millimetric wavelengths. The ring seems to be produced by light
scattered by the edge of a cavity inside a much larger disk. At the
cavity edge, the disk thickness is estimated to be one-tenth of the
cavity radius. Light which illuminates this cavity edge appears to be
reddened by absorption through the inner disks. Azimuthal variations
of the illumination indicate that the inner disks must be lumpy.
---------------------------------------------------------
Title: Saturn' Rings Edge-on Observations at 0.1 Arcsecond Resolution
With Adaptive Optics
Authors: Brahic, A.; Dumas, C.; Ferrari, C.; Graves, J.; Han, B.;
Northcott, M.; O'Connor, D.; Owen, T.; Perret, L.; Roddier, C.;
Roddier, F.; Thebault, P.
1995DPS....27.2709B Altcode: 1995BAAS...27.1132B
No abstract at ADS
---------------------------------------------------------
Title: Ground-based Near-Infrared Adaptive-Optics Imaging of the
Surface of Titan
Authors: Han, B.; Owen, T.; Brahic, A.; Dumas, C.; Roddier, F.;
Roddier, C.; Northcott, M.; Graves, J. E.; O'Connor, D.
1995DPS....27.1802H Altcode: 1995BAAS...27.1104H
No abstract at ADS
---------------------------------------------------------
Title: Near-Infrared Observations of Pluto and Charon Using Adaptive
Optics Imaging
Authors: O'Connor, D. J.; Anuskiewicz, J.; Brahic, A.; Dumas, C.;
Graves, J. E.; Northcott, M.; Owen, T.; Roddier, C.; Roddier, F.
1995DPS....27.1611O Altcode: 1995BAAS...27.1101O
No abstract at ADS
---------------------------------------------------------
Title: Adaptive Optics Imaging of Proto--Planetary Nebulae: Frosty
Leo and the Red Rectangle
Authors: Roddier, F.; Roddier, C.; Graves, J. E.; Northcott, M. J.
1995ApJ...443..249R Altcode:
Near-infrared, 0.1 arcsec resolution images of the bipolar nebulae
Frosty Leo and Red Rectangle have been obtained with an adaptive optics
system developed at the University of Hawaii. In both cases evidence
is found supporting a binary star formation mechanism for the nebulae.
---------------------------------------------------------
Title: First astronomical observations with the University-of-Hawai'i
experimental adaptive optics system.
Authors: Roddier, F.; Anuskiewicz, J.; Graves, J. E.; Northcott,
M. J.; Roddier, C.; Surace, J.; Tokunaga, A.
1995seft.conf..313R Altcode:
This paper describes the first scientific results obtained with an
experimental adaptive optics system developed at the University
of Hawai'i. Observations were made in December 1993 at the 3.6-m
Canada-France-Hawai'i Telescope (CFHT), and in January 1994 at the 4-m
United Kingdom Infrared Telescope (UKIRT). High angular resolution
images of various astronomical sources were obtained in the I band
with a CCD camera, and in the J, H and K bands with a 256×256 NICMOS
array. In all cases the observed objects were bright enough to serve
as a reference source for the wave-front sensor. A brief description
of the system and a discussion of its performance are given. The paper
describes the observations and the scientific results.
---------------------------------------------------------
Title: Application of interferometry and adaptive optics to the
detection of extra-solar planets: a computer simulation.
Authors: Roddier, C.; Roddier, F.
1995Ap&SS.223..183R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Prospects for Imaging Interferometry
Authors: Roddier, F.
1995Ap&SS.223..109R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Error propagation in a closed-loop adaptive optics system:
a comparison between Shack-Hartmann and curvature wave-front sensors.
Authors: Roddier, F.
1995OptCo.113..357R Altcode:
It is shown that the error propagation problem associated with curvature
sensing can be offset when the sensor is used in a closed feedback
loop with an unresolved reference point source. A demonstration is
given in the ideal case of full compensation under low noise conditions.
---------------------------------------------------------
Title: Testing optical telescopes from defocused stellar images
Authors: Roddier, Claude A.; Graves, J. Elon; Northcott, Malcolm J.;
Roddier, Francois J.
1994SPIE.2199.1172R Altcode:
Wave-front reconstruction from defocused stellar images has now been
widely applied to the testing of ground-based optical telescopes. We
describe here the latest improvements to the technique and discuss how
to reach a maximum accuracy. Statistics are given on the aberrations
observed over 10 different telescopes.
---------------------------------------------------------
Title: Adaptive optics at the University of Hawaii IV: a
photon-counting curvature wavefront sensor
Authors: Graves, J. Elon; Roddier, Francois J.; Northcott, Malcolm J.;
Anuskiewicz, Jim; Monnet, Guy
1994SPIE.2201..502G Altcode:
A photon counting wavefront curvature sensor (WFS) with 13 subapertures
suitable for adaptive optics in astronomy has been developed at the
University of Hawaii. This sensor is capable of using very faint point
sources or slightly extended sources to derive the wavefront signal. The
sensitivity of this sensor is continuously variable and can be adjusted
in real time to match the seeing conditions at the time. The wavefront
sampling geometry has been optimized for correcting the standard
atmosphere up to 9 orders expressed in terms of Zernike's. Its output
is used in conjunction with a newly developed deformable bimorph
mirror for high efficiency correction capabilities. This WFS has
successfully been used recently at the CFHT and UKIRT facilities on
Mauna Kea on a variety of astronomical objects. Point sources, double
stars, planetary nebula, galactic nuclei, and some of the moons of
Jupiter have all been successfully attempted. Limiting magnitude has
not been explored in great detail at the telescope, but we have taken
the system down to magnitude R equals 13.7 (V equals 15) with a 3.6
meter aperture with success. This was achieved during bright time or
whilst the full moon was present.
---------------------------------------------------------
Title: Adaptive optics at the University of Hawaii I: current
performance at the telescope
Authors: Roddier, Francois J.; Anuskiewicz, Jim; Graves, J. Elon;
Northcott, Malcolm J.; Roddier, Claude A.
1994SPIE.2201....2R Altcode:
The experimental adaptive optics system, currently developed at the
University of Hawaii, is now equipped with a VME-based control system,
and a high sensitivity wave-front sensor. The sensor uses an array of
13 photon-counting avalanche photodiodes which enable the system to
work with faint reference or `guide' sources, as faint as magnitude
15. Results of the first successful observing runs are described here.
---------------------------------------------------------
Title: Curvature-based wavefront sensor for use on extended patterns
Authors: Kupke, Renate; Roddier, Francois J.; Mickey, D.
1994SPIE.2201..519K Altcode:
We present results of simulations involving a curvature-based wavefront
sensor which uses an extended pattern as a reference source. The
proposed sensor provides measurements of both symmetric and asymmetric
aberration terms by comparing the Fourier transforms of two oppositely
defocused images. Symmetric terms such as defocus and astigmatism can
be measured without regard to the object distribution. The asymmetric
terms, such as tip and tilt, rely on averaging the signal over many
atmospheric realizations in order to determine the object phase, or on
defining an arbitrary reference phase. Only after removal of the object
Fourier transform phase can the asymmetric terms be identified. Although
this paper reports on preliminary results, we believe the proposed
sensor will be useful for both real-time compensation of atmospheric
distortions while imaging the Sun, and post-facto compensation of
optical misalignments in Earth-pointing satellites.
---------------------------------------------------------
Title: The UH Experimental Adaptive Optics System: First Telescope
Results with a Photon-Counting Avalanche Photodiode Array
Authors: Graves, J. E.; Northcott, M. J.; Roddier, C.; Roddier, F.;
Anuskiewicz, J.; Monnet, G.; Rigaut, F.; Madec, P. Y.
1994ESOC...48...47G Altcode: 1994aao..conf...47G
No abstract at ADS
---------------------------------------------------------
Title: Adaptive optics: performance and limitations [invited]
Authors: Roddier, F.
1994IAUS..158..273R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: First Astronomical Observations with the University-of-Hawaii
Experimental adaptive optics system
Authors: Roddier, F.; Anuskiewicz, J.; Graves, J. E.; Northcott,
M. J.; Roddier, C.; Surace, J.; Tokunaga, A.
1994awca.conf...23R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Problematic of Adaptive Optics Design
Authors: Roddier, F.
1994ASIC..423...89R Altcode: 1994aoa..conf...89R
No abstract at ADS
---------------------------------------------------------
Title: Prospects in Adaptive Optics for Solar Applications
Authors: Roddier, F.; Graves, J. E.
1994IAUS..154..557R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Wave-front reconstruction from defocused images and the
testing of ground-based optical telescopes.
Authors: Roddier, C.; Roddier, F.
1993JOSAA..10.2277R Altcode: 1993JOSA...10.2277R; 1993OSAJ...10.2277R
A new method has been developed for testing the optical quality of
ground-based telescopes. Aberrations are estimated from wideband
long-exposure defocused stellar images recorded with current
astronomical CCD cameras. An iterative algorithm is used that simulates
closed-loop wave-front compensation in adaptive optics. Compared with
the conventional Hartmann test, the new method is easier to implement,
has a similar accuracy, and provides a higher spatial resolution on the
reconstructed wave front. It has been applied to several astronomical
telescopes and has been found to be a powerful diagnostic tool for
improving image quality.
---------------------------------------------------------
Title: SISTERS: a space interferometer for the search for terrestrial
exo-planets by rotation shearing
Authors: Bely, Pierre Y.; Burrows, Christopher J.; Roddier, Francois
J.; Weigelt, Gerd; Bernasconi, M. C.
1993SPIE.1947...73B Altcode:
A concept for a space-based interferometer dedicated to the detection
of extrasolar earth-like planets is presented. Detection is done in
the near infrared (10 micrometers ) where the expected star to planet
flux ratio is down to 10(superscript 6) compared to 10(superscript 10)
in the visible. The longer wavelength also makes is easier to avoid
light scatter due to optics micro-roughness. Parent star cancellation is
obtained with a rotation shearing interferometer working at its null on
axis. The interferometer is of the Fizeau configuration with an aperture
composed of twelve 1.2 meter mirrors on a 20 meter ring. This size,
which corresponds to a resolving power of 0.05 arcsecond, allows for
the investigation of about 30 candidate stars. The interferometer is
supported by a chemically rigidized structure deployed by inflation. All
optical elements are passively cooled to about 70 degrees Kelvin to
reduce the instrumental infrared background. The spacecraft is located
at the second Lagrangian point of the earth-sun system in order to
minimize attitude control and baffling requirements.
---------------------------------------------------------
Title: HARDI-2: a high-angular-resolution deployable interferometer
for UV observations of nearby stars
Authors: Bely, Pierre Y.; Burrows, Christopher J.; Lamers, H. J.;
Roddier, Francois J.; Weigelt, Gerd
1993SPIE.1947...84B Altcode:
We describe a concept for an orbiting astronomical observatory which
will allow high spatial resolution far-UV observations of nearby
stars. The scientific goal is to study stellar activity and mass
loss using imaging and spectroscopy. Specific areas of study include
stellar surfaces, large scale magnetohydroynamic effects, interacting
binaries and stellar winds. The instrument is an interferometer with
an 8-meter baseline providing 3 milliarcseconds resolution at 1200
Angstrom. The interferometer configuration is of the Fizeau type which
affords excellent ultraviolet throughput because of the small number
of reflections. The collecting aperture is composed of six 0.6 meter
diameter elements distributed on a circle in such a way as lead to near
uniform u-v plan coverage when the instrument is rotated around the
line of sight. This will lead to excellent imaging capabilities. The
interferometer individual channels are kept coaligned and coherent
using the light of a nearby guide star. The supporting structure is
folded for launch and automatically deployed once on orbit. To minimize
disturbance torques and thermal shocks, the spacecraft will be located
on a high earth orbit or at the Lagrangian point.
---------------------------------------------------------
Title: Combined approach to the Hubble Space Telescope wave-front
distortion analysis.
Authors: Roddier, Claude; Roddier, Francois
1993ApOpt..32.2992R Altcode:
Stellar images taken by the Hubble Space Telescope at various focus
positions have been analyzed to estimate wave-front distortion. Rather
than using a single algorithm, the authors found that better results
were obtained by combining the advantages of various algorithms. For
the planetary camera, the most accurate algorithms consistently gave
a spherical aberration of -0.290-μm rms with a maximum deviation
of 0.005 μm. Evidence was found that the spherical aberration is
essentially produced by the primary mirror. The illumination in the
telescope pupil plane was reconstructed and evidence was found for a
slight camera misalignment.
---------------------------------------------------------
Title: Testing Telescopes from Out-Of Images - Application to
Groundbased Telescopes and to the Space Telescope
Authors: Roddier, C.; Roddier, F.
1993oia..conf..236R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SISTERS: a space interferometer for the search for terrestrial
exo-planets by rotation shearing.
Authors: Bely, P. -Y.; Burrows, C. J.; Roddier, F.; Weigelt, G.;
Bernasconi, Marco C.
1992ESASP.354...99B Altcode: 1992tsbi.rept...99B
A concept for a space-based interferometer dedicated to the detection
of extrasolar earth-like planets is presented. Detection is done in the
near infrared (10 μm) where the expected star to planet flux ratio is
down to 10<SUP>6</SUP> compared to 10<SUP>10</SUP> in the visible. The
longer wavelength also makes it easier to avoid light scatter due to
optics micro-roughness. Parent star cancellation is obtained with a
rotation shearing interferometer working at its null on axis.
---------------------------------------------------------
Title: HARDI: a high angular resolution deployable interferometer.
Authors: Bely, P. -Y.; Burrows, C. J.; Roddier, F.; Weigelt, G.
1992ESASP.354..235B Altcode: 1992tsbi.rept..235B
The authors describe a proposed orbiting interferometer covering
the UV, visible and near-IR spectral ranges. With a 6-meter baseline
and a collecting area equivalent to about a 1.4 meter diameter full
aperture, this instrument is intended to offer significant improvements
in resolution over the Hubble Space Telescope, and complement the new
generation of ground-based interferometers with much better limiting
magnitude and spectral coverage.
---------------------------------------------------------
Title: HARDI: A high angular resolution deployable interferometer
for space
Authors: Bely, Pierre Y.; Burrows, Christopher; Roddier, Francois;
Weigelt, Gerd
1992NASCP3066..114B Altcode: 1992loui.rept..114B
We describe here a proposed orbiting interferometer covering the
UV, visible, and near-IR spectral ranges. With a 6-m baseline and a
collecting area equivalent to about a 1.4 m diameter full aperture,
this instrument will offer significant improvements in resolution
over the Hubble Space Telescope, and complement the new generation
of ground-based interferometers with much better limiting magnitude
and spectral coverage. On the other hand, it has been designed as a
considerably less ambitious project (one launch) than other current
proposals. We believe that this concept is feasible given current
technological capabilities, yet would serve to prove the concepts
necessary for the much larger systems that must eventually be flown. The
interferometer is of the Fizeau type. It therefore has a much larger
field (for guiding) better UV throughout (only 4 surfaces) than phased
arrays. Optimize aperture configurations and ideas for the cophasing and
coalignment system are presented. The interferometer would be placed
in a geosynchronous or sunsynchronous orbit to minimize thermal and
mechanical disturbances and to maximize observing efficiency.
---------------------------------------------------------
Title: Status of Astronomical Adaptive Optics Developments
Authors: Roddier, F.
1992ESOC...39..571R Altcode: 1992hrii.conf..571R
No abstract at ADS
---------------------------------------------------------
Title: Towards lower cost adaptive optics systems.
Authors: Roddier, F.
1992aolt.meet...59R Altcode:
Techniques to reduce the cost of adaptive optics systems without
degrading performance are discussed.
---------------------------------------------------------
Title: Recent results of the UH (University of Hawaii) adaptive
optics system.
Authors: Graves, J. E.; McKenna, D. L.; Northcott, M. J.; Roddier, F.
1992aolt.meet..146G Altcode:
Uncompensated, tip-tilt compensated, and fully compensated images are
presented. The compensation is performed in the laboratory, after a
seeing generator, and at the telescope.
---------------------------------------------------------
Title: New optical testing methods developed at the University of
Hawaii: results on ground-based telescopes and Hubble Space Telescope
Authors: Roddier, Claude A.; Roddier, Francois J.
1992SPIE.1531...37R Altcode:
New methods have been developed to test telescope optics either at the
fabrication stage or while in operation. Results recently obtained at
the University of Hawaii are presented.
---------------------------------------------------------
Title: The UH (University of Hawaii) prototype adaptive optics system.
Authors: Graves, J. E.; McKenna, D. L.; Northcott, M. J.; Roddier, F.
1992aolt.meet..173G Altcode:
A description is given of the adaptive optics system currently built at
UH for astronomical applications. Results of laboratory and telescope
performance tests are presented.
---------------------------------------------------------
Title: The UH (University of Hawaii) wavefront curvature sensor.
Authors: Roddier, F.; Graves, J. E.; McKenna, D. L.; Northcott, M. J.
1992aolt.meet..170R Altcode:
The theory of curvature sensing is reviewed and the UH sensor is
described. Results of laboratory performance tests are presented.
---------------------------------------------------------
Title: University of Hawaii adaptive optics system: I. General
approach
Authors: Roddier, F.; Graves, J. E.; McKenna, D.; Northcott, M.
1991SPIE.1542..248R Altcode:
An innovative adaptive optics (AO) system is being developed at the
University of Hawaii to sharpen images produced by telescopes on
Mauna Kea.
---------------------------------------------------------
Title: Reconstruction of the Hubble Space Telescope mirror figure
from out-of-focus stellar images
Authors: Roddier, C.; Roddier, F.
1991SPIE.1494...78R Altcode:
From the illumination recorded in two defocused stellar images it is
possible to reconstruct both the amplitude and the phase of the incoming
wave front viewed from the focal plane, providing a powerful diagnostic
tool for telescope optics. Results obtained from defocused stellar
images taken in flight by the Hubble Space Telescope are presented.
---------------------------------------------------------
Title: Large-mirror testing facility at the National Optical Astronomy
Observatories.
Authors: Barr, L. D.; Coudé du Foresto, V.; Fox, J.; Poczulp, G. A.;
Richardson, J.; Roddier, C.; Roddier, F.
1991OptEn..30.1405B Altcode:
A method for testing the surfaces of large mirrors has been developed
to be used even when conditions of vibration and thermal turbulence in
the light path cannot be eliminated. The full aperture of the mirror
under test is examined by means of a scatterplate interferometer that
has the property of being a quasi-common-path method, although any
means for obtaining interference fringes will do. The method uses a
remotely operated CCD camera system to record the fringe pattern from
the workpiece. The typical test is done with a camera exposure of about
a millisecond to "freeze" the fringe pattern on the detector. Averaging
up to 10 separate exposures effectively eliminates the turbulence
effects. The method described provides the optician with complete
numerical information and visual plots for the surface under test and
the diffracted image the method will produce, all within a few minutes,
to an accuracy of 0.01 μm measured peak-to-valley.
---------------------------------------------------------
Title: Large-mirror testing facility at the National Optical Astronomy
Observatories
Authors: Coudé du Foresto, V.; Fox, J.; Poczulp, G. A.; Richardson,
J.; Roddier, Claude; Roddier, Francois; Barr, L. D.
1991OptEn..30.1405C Altcode:
A method for testing the surfaces of large mirrors has been developed
to be used even when conditions of vibration and thermal turbulence in
the light path cannot be eliminated. The full aperture of the mirror
under test is examined by means of a scatterplate interferometer that
has the property of being a quasi-common-path method, although any
means for obtaining interference fringes can be used. By operating
the test equipment remotely, the optician does not cause unnecessary
vibrations or heat in the testing area. The typical test is done with a
camera exposure of about a millisecond to 'freeze' the fringe pattern
on the detector. Averaging up to 10 separate exposures effectively
eliminates the turbulence effects. From the intensity information, a
phase map of the wavefront reflected from the surface is obtained using
a phase-unwrapping technique. The method provides the optician with
complete numerical information and visual plots for the surface under
test and the diffracted image the method will produce to an accuracy
of 0.01 micron measured peak-to-valley. The method has been extensively
used for a variety of test of a 1.8-m-diam borosilicate-glass honeycomb
mirror, where the method was shown to have a sensitivity equal to a
Foucault test.
---------------------------------------------------------
Title: A Simple Low-Order Adaptive Optics System for Near-Infrared
Applications
Authors: Roddier, Francois; Northcott, Malcolm; Graves, J. Elon
1991PASP..103..131R Altcode:
It is shown that low-order wavefront compensation can significantly
improve astronomical images over most of the sky. A novel approach to
wavefront sensing and compensation is described. It is optimized for
low-order correction and high efficiency. Computer-simulation results
show it can achieve the desired performance, and preliminary laboratory
tests demonstrate its feasibility.
---------------------------------------------------------
Title: Self-calibration in rotational shearing interferometry
Authors: Roddier, Claude; Roddier, Francois
1990SPIE.1351..698R Altcode:
Diffraction-limited imaging of an incoherent object observed
through fixed unknown aberrations is demonstrated using rotational
shear interferograms. Reconstruction algorithms were inspired by
radio-astronomy self-calibration methods. They require no reference
point source other than the object itself to calibrate the effects
of aberrations.
---------------------------------------------------------
Title: Variations on a Hartmann theme.
Authors: Roddier, F.
1990OptEn..29.1239R Altcode:
The author explores modifications of the classical Hartmann wavefront
sensing technique that can be used to improve its accuracy, dynamic
range, and spatial resolution. He describes a differential sensor with
variable sensitivity. The author reviews the use of various possible
Hartmann masks and discusses their interferometric properties. He
propose the use of Fourier analysis and shows its relationship to moire
methods. The author finally envisages the possibility of mapping both
the slope and the total curvature (Laplacian) of the wavefront with
the same setup.
---------------------------------------------------------
Title: Diffraction-limited imaging of unknown objects through fixed
unknown aberrations using interferometry.
Authors: Roddier, Claude; Roddier, Francois
1990JOSAA...7.1824R Altcode: 1990OSAJ....7.1824R; 1990JOSA....7.1824R
Diffraction-limited imaging of unknown objects through fixed
unknown aberrations is demonstrated using rotational shear
interferograms. Objects are assumed to be fully incoherent. No reference
point source is used to calibrate the effects of aberrations. Several
algorithms are described, and two are successfully used to reconstruct
extended objects. Best results are obtained by combining the two
successful ones.
---------------------------------------------------------
Title: Spatial interferometry in optical astronomy.
Authors: Gezari, Daniel Y.; Roddier, Francois; Roddier, Claude
1990sioa.book.....G Altcode:
This report is a bibliographic guide to publications of spatial
interferometry techniques applied to optical astronomy. Listings appear
in alphabetical order, by first author, as well as in specific subject
categories listed in chronological order, including imaging theory
and speckle interferometry, experimental techniques, and observational
results of astronomical studies of stars, the Sun, and the solar system.
---------------------------------------------------------
Title: Variations on a Hartmann theme
Authors: Roddier, Francois J.
1990SPIE.1237..662R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A space interferometer concept for the detection of extrasolar
earth-like planets.
Authors: Bely, P. Y.; Burrows, C. J.; Roddier, F.
1990SPIE.1237..198B Altcode:
A concept for a space-based interferometer dedicated to the detection
of extrasolar earth-like planets is described. The interferometer is
of the Fizeau configuration with an aperture composed of twelve 1.2 m
mirrors on a 20 m ring. The subapertures are distributed to optimize
the u-v plane coverage when the interferometer is rotated around its
axis. Parent star cancellation is obtained by the combination of a
coronagraph and a rotation shearing interferometer. The interferometer
is supported by a chemically rigidized structure deployed by
inflation. Due to the lack of side shield and the resulting limited
pointing capability with respect to the sun, it is proposed to locate
the instrument at the second Lagrangian point of the earth-sun system.
---------------------------------------------------------
Title: Testing of telescope optics: a new approach
Authors: Roddier, C.; Roddier, F.; Stockton, A.; Pickles, A.;
Roddier, N.
1990SPIE.1236..756R Altcode:
Results recently obtained for the use of the curvature-sensing method
as a substitute for slope sensing in optical wavefront reconstruction,
using long-exposure CCD images of the beam cross-section on either
side of the telescope focal plane. A program based on the solution
to the Poisson equation is then applied in order to reconstruct
the wavefront. Relative to the existing Hartmann sensing methods,
curvature-sensing yields sensitivity comparable to that of the
Shack-Hartmann test. Additional optics and reference plane-based
calibration are obviated. Tests of the new method on an 88-inch
Ritchey-Chretien telescope have yielded a map of residual wavefront
errors as a solution of the Poisson equation.
---------------------------------------------------------
Title: Seeing monitor based on wavefront curvature sensing
Authors: Roddier, F.; Graves, J. E.; Limburg, E.
1990SPIE.1236..474R Altcode:
A new wavefront sensing technique called curvature sensing is
described. It maps the wavefront total curvature rather than its slope
and has been applied to an experimental seeing monitor which detects
turbulence induced fast focus fluctuations. Some of the advantages
this monitor presents, as compared to DIMM's, are: (1) sensitivity
is increased by the use of a circular pupil, (2) the cost is lowered
by the use of a photomultiplier, (3) the loss of signal is prevented
by the system's fast run, (4) the system runs continuously, and (5)
the noise bias is continuously measured and subtracted out.
---------------------------------------------------------
Title: Seeing at Mauna Kea: a joint UH-UN-NOAO-CFHT study
Authors: Roddier, Francois J.; Cowie, L. L.; Graves, J. Elon; Songaila,
A.; McKenna, Daniel; Vernin, Jean; Azouit, M.; Caccia, J. L.; Limburg,
Eric J.; Roddier, Claude A.; Salmon, Derrick A.; Beland, Stephane;
Cowley, David J.; Hill, S.
1990SPIE.1236..485R Altcode:
Two short-term campaigns are described in which several instruments were
simultaneously used to obtain quantitative estimates of the various
contributions to image degradation at the Mauna Kea observatory. The
various contributions include the free atmosphere, boundary layer
turbulence, dome and mirror seeing effects, and telescope optics. A
secondary goal of the study was to investigate the relationship between
seeing and meteorological conditions on Mauna Kea, which may lead to
seeing forecasting. The first campaign was held from November 1 to
13, 1987; the second was held from June 9 to 19, 1989. The campaigns
were a cooperative effort involving five institutions: the Institute
of Astronomy and the Department of Meteorology both at the University
of Hawaii (UH), the National Optical Astronomy Observatories (NOAO) in
Tucson, the Canada-france-Hawaii Corporation (CFHT), and the Department
of Astrophysics at the University of Nice (UN), France. The general
approach, instruments used, and some of the results already obtained
are described.
---------------------------------------------------------
Title: Bibliography of spatial interferometry in optical astronomy
Authors: Gezari, Daniel Y.; Roddier, Francois; Roddier, Claude
1990STIN...9020911G Altcode:
The Bibliography of Spatial Interferometry in Optical Astronomy
is a guide to the published literature in applications of spatial
interferometry techniques to astronomical observations, theory
and instrumentation at visible and infrared wavelengths. The key
words spatial and optical define the scope of this discipline,
distinguishing it from spatial interferometry at radio wavelengths,
interferometry in the frequency domain applied to spectroscopy, or
more general electro-optics theoretical and laboratory research. The
main bibliography is a listing of all technical articles published
in the international scientific literature and presented at the
major international meetings and workshops attended by the spatial
interferometry community. Section B summarizes publications dealing
with the basic theoretical concepts and algorithms proposed and applied
to optical spatial interferometry and imaging through a turbulent
atmosphere. The section on experimental techniques is divided into
twelve categories, representing the most clearly identified major areas
of experimental research work. Section D, Observations, identifies
publications dealing specifically with observations of astronomical
sources, in which optical spatial interferometry techniques have
been applied.
---------------------------------------------------------
Title: The ESO differential image motion monitor
Authors: Sarazin, M.; Roddier, F.
1990A&A...227..294S Altcode:
This paper describes the ESO differential image-motion monitor and
reviews the theory of differential image motion measurements. It is
shown that this small transportable image-motion monitor, which is
able to operate in the open air, can yield quantitative estimates of
the image quality produced by a large telescope situated at the same
location. Several copies of this instrument are being used for the
European Very Large Telescope site testing campaign, in search of the
best possible location for this telescope.
---------------------------------------------------------
Title: Active telescope systems
Authors: Roddier, Francois J.
1989SPIE.1114.....R Altcode:
The present conference discusses topics in the fundamental limitations
of adaptive optics in astronomical telescopy, integrated telescope
systems designs, novel components for adaptive telescopes, active
interferometry, flexible-mirror and segmented-mirror telescopes,
and various aspects of the NASA Precision Segmented Reflectors
Program. Attention is given to near-ground atmospheric turbulence
effects, a near-IR astronomical adaptive optics system, a simplified
wavefront sensor for adaptive mirror control, excimer laser guide
star techniques for adaptive astronomical imaging, active systems
in long-baseline interferometry, mirror figure control primitives
for a 10-m primary mirror, and closed-loop active optics for large
flexible mirrors subject to wind buffet deformations. Also discussed are
active pupil geometry control for a phased-array telescope, extremely
lightweight space telescope mirrors, segmented-mirror manufacturing
tolerances, and composite deformable mirror design.
---------------------------------------------------------
Title: HARDI: a high angular resolution deployable interferometer
for space
Authors: Bely, Pierre Y.; Burrows, Christopher; Roddier, Francois;
Weigelt, Gerd
1989SPIE.1130...92B Altcode:
The present orbiting interferometer proposal for operation in the
UV, visible, and near-IR spectral ranges employs a 6-m baseline and
a collecting area equivalent to an approximately 1.4-m diameter
aperture. The instrument, which is of Fizeau type and therefore
possesses better UV throughput than phased arrays, is projected
to be able to furnish resolutions superior to those of the Hubble
Space Telescope, as well as to complement prospective ground-based
interferometers with its greater limiting magnitude and spectral
coverage. A single launch will suffice to place the system in GEO or
sun-synchronous orbit, in order to minimize thermal and mechanical
disturbances and maximize observing efficiency.
---------------------------------------------------------
Title: Curvature sensing and compensation: a computer simulation.
Authors: Roddier, Nicolas; Roddier, Francois
1989SPIE.1114...92R Altcode:
The concept of curvature sensing and compensation in adaptive optics
is investigated by means of a computer simulation. Satisfactory
correction is observed when the signal from a 13 element sensor is
directly applied to a simulated membrane mirror.
---------------------------------------------------------
Title: Diffraction-limited imaging through aberrated optics using
pupil-plane and/or image-plane information
Authors: Roddier, Francois; Roddier, Claude; van Peursem, Stacy
1989SPIE.1059..173R Altcode:
Diffraction-limited imaging of an unknown, incoherently illuminated
object is demonstrated through strongly aberrated optics with unknown
aberrations. No reference source other than the object itself is used
to calibrate the aberrations. Two different techniques are discussed
and their merits are compared.
---------------------------------------------------------
Title: Optical Propagation and Image Formation Through the Turbulent
Atmosphere
Authors: Roddier, F.
1989ASIC..274...33R Altcode: 1989dli..conf...33R
No abstract at ADS
---------------------------------------------------------
Title: Pupil-Plane Interferometry
Authors: Roddier, C.; Roddier, F.
1989ASIC..274..221R Altcode: 1989dli..conf..221R
No abstract at ADS
---------------------------------------------------------
Title: Diffraction-limited imaging through aberrated optics using
pupil-plane and/or image-plane information.
Authors: Roddier, F.; Roddier, C.; van Peursem, S.
1989sscn.conf..173R Altcode:
Diffraction-limited imaging of an unknown, incoherently illuminated
object is demonstrated through strongly aberrated optics with unknown
aberrations. No reference source other than the object itself is used
to calibrate the aberrations. Two different techniques are discussed
and their merits are compared.
---------------------------------------------------------
Title: Spatially resolving the stellar environment.
Authors: Roddier, Francois
1989mse..proc...65R Altcode:
High angular resolution stellar interferometry at optical wavelengths
is making rapid progress. This contribution reviews the techniques of
speckle interferometry and speckle imaging, pupil-plane interferometry,
adaptive optics, and long-baseline optical interferometry. Within a
decade or two, imaging stars and their environment will be possible
with telescope arrays in space and on the ground.
---------------------------------------------------------
Title: Compact rotational shearing interferometer for astronomical
applications.
Authors: Roddier, C.; Roddier, F.; Demarcq, J.
1989OptEn..28...66R Altcode:
The fabrication and assembly of a compact rotational shearing
interferometer with variable shear and phase compensation is
described. The interferometer has been used for seeing measurements
and interferometric imaging in optical astronomy.
---------------------------------------------------------
Title: Interferometric imaging in optical astronomy
Authors: Roddier, F.
1988PhR...170...97R Altcode:
Not Available <P />Operated by the Association of Universities for
Research in Astronomy, Inc., under contract with the National Science
Foundation.
---------------------------------------------------------
Title: Diffraction-limited astronomical infrared imaging through
the turbulent atmosphere
Authors: Christou, J. C.; Freeman, J. D.; McCarthy, D. W., Jr.;
Roddier, F.; Beckers, J. M.
1988JPhD...21S..49C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Curvature Sensing and Compensation: A New Concept in Adaptive
Optics
Authors: Roddier, F.; Roddier, C.
1988ESOC...30..667R Altcode: 1988vltt.conf..667R; 1988vlti....2..667R
The authors describe a new wavefront sensor which can favourably replace
the Shack-Hartmann sensor either for the control of telescope optics
or in adaptive optics systems. In the last case the sensor delivers
a signal which can be directly applied to a membrane mirror producing
a very simple and fast, entirely analog, control loop.
---------------------------------------------------------
Title: Coupling starlight into single-mode fiber optics
Authors: Shaklan, Stuart; Roddier, Francois
1988ApOpt..27.2334S Altcode:
The efficiency with which starlight can be coupled into a single-mode
fiber optic that is placed in the focal plane of a telescope has
been calculated. The calculations are performed for a wide range
of seeing conditions, with and without rapid image stabilization,
and for a wide range of wavelengths. The dependence of coupling
efficiency on the f-ratio of the incident beam is explored. Also, the
coupling efficiency as a function of displacement for a perfect Airy
pattern is calculated. A computer program is used which simulates
atmospheric wavefronts to determine the variance of instantaneous
coupling efficiency as a function of seeing. In perfect conditions,
the maximum efficiency at the LP11 mode cutoff is 78 percent due to
the mismatch of the Airy pattern and the nearly Gaussian mode of the
fiber. Maximum total coupled power is attained at d/r(0) = 4 with
rapid image stabilization.
---------------------------------------------------------
Title: Curvature sensing and compensation: a new concept in adaptive
optics
Authors: Roddier, François
1988ApOpt..27.1223R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Application of bispectrum analysis for phase recovery from
one-dimensional infrared speckle data.
Authors: Freeman, J. D.; Christou, J. C.; Roddier, F.; McCarthy,
D. W., Jr.; Cobb, M. L.
1988JOSAA...5..406F Altcode: 1988OSAJ....5..406F
The authors apply bispectrum analysis to one-dimensional astronomical
infrared specklegrams and compare the recovered phases and their
variances with those obtained by the Knox-Thompson algorithm. A
number of averaging techniques are used to combine the multiple object
phase estimates from the average bispectrum phases. Analysis of these
techniques indicates that only a fraction of the nonredundant support
of the bispectrum is necessary for the object phase retrieval. The
authors have calibrated their bispectra for zero-mean additive detector
noise. Results are presented for a bright point source and the nearby
binary star Ross 614AB along with its point-source comparison.
---------------------------------------------------------
Title: An Entry Level Interferometer for Space
Authors: Bely, P. Y.; Burrows, C.; Roddier, F.; Weigelt, G.
1988soae.conf....6B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Passive versus active methods in optical interferometry.
Authors: Roddier, F.
1988ESOC...29..565R Altcode: 1988hrii.conf..565R
This paper is an attempt to compare active versus passive methods
for image reconstruction. Adaptive optics is shown to provide a
better signal-to-noise ratio on bright sources whereas passive
image reconstruction is more effective on faint sources. The same
two kinds of approach and the same conclusion also apply to long
baseline interferometry and image reconstruction from aperture
synthesis. Concepts developed for adaptive optics can be applied with
profit to telescope arrays. In this case, the active approach seems
more practical.
---------------------------------------------------------
Title: Pupil Plane Interferometry
Authors: Roddier, C.; Roddier, F.
1988dli..conf..221R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Optical Propagation and Image Formation Through the Turbulent
Atmosphere
Authors: Roddier, F.
1988dli..conf...33R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Phase recovery from pupil-plane interferograms.
Authors: Roddier, C.; Roddier, F.
1988ESOC...29..257R Altcode: 1988hrii.conf..257R
No abstract at ADS
---------------------------------------------------------
Title: Application of speckle masking to 1-D infrared speckle data:
modulus recovery and imaging.
Authors: Christou, J. C.; Freeman, J. D.; McCarthy, D. W., Jr.;
Roddier, F.
1988ESOC...29..201C Altcode: 1988hrii.conf..201C
The authors have applied the speckle masking or bispectrum algorithm to
both real and simulated 1-D infrared speckle data in order to retrieve
the phase information. The bispectrum modulus has also been used as
an alternative approach to obtain the Fourier modulus of the data. The
authors show results, including images, from real data obtained using
slit scanning data as well as the NOAO infrared speckle camera.
---------------------------------------------------------
Title: Interferometric imaging in optical astronomy.
Authors: Roddier, F.
1988PhR...170...99R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Phase variances from triple correlation analysis
Authors: Roddier, Francois; Christou, Julian C.
1988OptCo..65..115R Altcode:
A simple heuristic model for the triple correlation procedure (Roddier,
1986) is extended to enable computation of the variances of bispectrum
phases. The bispectrum analysis is applied to one-dimensional infrared
speckle data obtained at the 2.3-m Stewart Observatory telescope for
an unresolved source, validating the effectiveness of the method. Good
qualitative agreement is also obtained between the measured and model
bispectrum SNR. It is noted that the recovered phases of HR 1739 show
structure that is not commensurate with a point source.
---------------------------------------------------------
Title: Fiber linked telescope arrays on the ground and in space
Authors: Connes, P.; Roddier, F.; Shaklan, S.; Ribak, E.
1987ESASP.273...73C Altcode: 1987ois..work...73C
The use of single-mode optical fibers in telescope arrays, first
proposed for a set of free-flying spacecraft, is developed and applied
to more modest, shorter range projects. The basic advantage remains a
considerable simplification in the control system; the main limitation
is spectral range. Two proposals are described: a ground-based array of
small optical telescopes supported on a radio dish, and a similar space
array. The control system is almost the same in both cases, hence the
ground-based array can be considered a test-bench for the space device.
---------------------------------------------------------
Title: Imaging strategies for a space-borne interferometer
Authors: Roddier, Francois
1987ESASP.273...23R Altcode: 1987ois..work...23R
The author describes two main strategies: (1) a large filled aperture
consisting of a mosaic of light-weight mirrors. Internal referencing is
used to coalign and approximately cophase the array. Diffraction-limited
imaging is achieved by means of interferometric techniques such
as roll deconvolution or pupil-plane interferometry. (2) A diluted
array of diffraction-limited telescopes. Such an array can be exactly
coaligned and cophased using internal and/or external references. In
case of either strategy, pointing accuracy and mechanical vibrations
will limit the system performances.
---------------------------------------------------------
Title: Single-mode fiber optics in a long-baseline interferometer
Authors: Shaklan, Stuart B.; Roddier, Francois
1987ApOpt..26.2159S Altcode:
The potential for using single-mode fiber optics to link two or more
telescopes in a large optical to near-IR astronomical interferometer
was investigated. On an optical bench, the effects of dispersion,
temperature, and birefringence on wide-bandwidth interference fringes
were observed using up to 30 m of single-mode fiber in each arm of a
Twyman-Green interferometer.
---------------------------------------------------------
Title: Application of Bispectrum Analysis to 1-D Infrared Speckle Data
Authors: Christou, J. C.; Freeman, J. D.; Roddier, F.; McCarthy,
D. W.; Cobb, M. L.
1987BAAS...19..749C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The physics of seeing: application of theory to site evaluation
and testing.
Authors: Roddier, F.
1987iopo.conf...12R Altcode:
Theory is used as a guideline to find an optimum strategy for the
evaluation of seeing quality. The ESO experimental campaign is described
as an example.
---------------------------------------------------------
Title: The Alpha-Orionis Envelope and its Evolution
Authors: Roddier, C.; Roddier, F.
1987iia..conf..231R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ground-based interferometry.
Authors: Roddier, F.
1987txra.symp...41R Altcode:
The results of high-angular-resolution interferometric observations
are reviewed, and prospects of future developments with ground-based
telescopes are discussed. Stellar sources up to magnitude m = 16 have
been resolved at the diffraction limit of large telescopes. Complete
image reconstruction of turbulence-degraded images is now currently
achieved, and new promising techniques are being developed for this
purpose. Submarcsec resolution has been achieved with long-baseline
interferometers using intensity interferometry, and marcsec resolution
is now achieved with much higher sensitivity using direct Michelson
interferometry.
---------------------------------------------------------
Title: Application of Triple Correlation to One-Dimensional Infrared
Speckle Data
Authors: Freeman, J. D.; Christou, J. C.; Roddier, F.; McCarthy,
D. W., Jr.; Cobb, M. L.
1987iia..conf...47F Altcode:
Triple correlation analysis, also known as bispectrum or speckle
masking, is a recently introduced technique to recover object phases
from atmospherically degraded short-exposure images (specklegrams). In
this paper the authors discuss how they have applied the bispectrum
analysis to 1-D infrared speckle data, taking into account additive
detector noise, to obtain object phases and to compare these phases to
those obtained using Knox-Thompson analysis. The authors also compare
three methods of obtaining the object phases from the bispectrum phases,
one of which is a rigorous statistical analysis using a minimum variance
unbiased estimator.
---------------------------------------------------------
Title: Application of bispectrum analysis to infrared speckle data.
Authors: Christou, J. C.; Freeman, J. D.; Roddier, F.; McCarthy,
D. W., Jr.; Cobb, M. L.; Shaklan, S. B.
1987SPIE..828...32C Altcode:
The bispectrum algorithm is applied to one-dimensional infrared
speckle data for retrieval of diffraction-limited phases using a
standard weighting-averaging technique to combine the multiple phase
estimates contained in the bispectrum. The bispectrum modulus is
also used to obtain visibility amplitudes. Results, including images,
are presented for three different binary stars. Simulated data have
also been used to study the behavior of the algorithm under different
signal-to-noise conditions, as well as a study of phase recovery for
different defocus conditions. The algorithm is sensitive, at a low
level, to focus changes, especially for noisy data. Comparison of
the bispectrum phases is made with those obtained from Knox- Thompson
cross spectra for all cases.
---------------------------------------------------------
Title: Processing of Interferograms
Authors: Roddier, C.; Roddier, F.
1987iia..conf...25R Altcode:
Since 1976, the authors have developed algorithms to map
both the amplitude and the phase of the fringes in pupil-plane
interferograms. These algorithms are essentially based on fast Fourier
transforms. The authors describe here the latest improvements.
---------------------------------------------------------
Title: Choix du site.
Authors: Roddier, F.
1987JAF....29...31R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Seeing and atmospheric turbulence: parameters relevant to
adaptive optics.
Authors: Roddier, F.
1987LFTR...28....7R Altcode:
Atmospheric parameters relevant to adaptive optics are reviewed and
the fundamental limitations imposed by the atmosphere are discussed.
---------------------------------------------------------
Title: Image reconstruction from rotational shear interferograms:
laboratoryand astronomical results.
Authors: Roddier, Francois; Roddier, Claude
1987SPIE..828..108R Altcode:
Images can be reconstructed from incoherent holograms recorded with a
rotation shearing interferometer. Reconstruction is possible through
strong optical aberrations if holograms are also taken either of a
reference source through the same shear, or of the same source through
a different shear.
---------------------------------------------------------
Title: Curvature sensing and compensation.
Authors: Roddier, F.; Forbes, F.; Shaklan, S.; Pinches, C.
1987LFTR...28..169R Altcode:
A new concept is proposed for real-time sensing and compensation of
atmospherically distorted wavefronts, using natural (incoherent),
possibly extended, reference sources. Instead of measuring an array
of 2-dimensional tilts, the optical sensor is sensitive to the local
wavefront curvature and to radial tilts at the pupil edge. Radial
tilts provide the boundary conditions required to solve the Poisson
equation for the wavefront. The sensor delivers a signal which can
be amplified and directly applied as a potential distribution on a
bimorph or a membrane mirror without requiring any computation.
---------------------------------------------------------
Title: High angular resolution infrared imaging at NOAO (Poster)
Authors: Christou, J. C.; Beckers, J. M.; Roddier, F.; Ridgway, S.;
Probst, R.; Freeman, J. D.; McCarthy, D. W., Jr.; Cobb, M. L.
1987iawa.conf..464C Altcode:
The authors discuss how the SBRC 58×62 InSb infrared imaging array will
be used for 2-D infrared speckle interferometry (IRSI) at NOAO. The
2-D IRSI is a logical extension of the 1-D slit-scanning technique
currently employed by a number of groups.
---------------------------------------------------------
Title: Signal-To Ratios and Beam Combination
Authors: Roddier, F.
1987iia..conf..135R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Phase Closure with Rotational Shear Interferometers
Authors: Roddier, F.; Roddier, C.
1987iia..conf...79R Altcode:
The authors show that phase closure relations can be obtained from
rotational shear interferograms and they discuss the necessary
conditions for the object phases to be recovered from such relations.
---------------------------------------------------------
Title: Redundant versus nonredundant beam recombination in an aperture
synthesis with coherent optical arrays.
Authors: Roddier, F.
1987JOSAA...4.1396R Altcode: 1987OSAJ....4.1396R
Signal-to-noise ratios for the amplitude of the object Fourier
components are compared assuming either redundant or nonredundant
beam recombination. A general condition is given for the object
brightness below which redundant beam recombination is superior. A
similar condition is found when the variance of the closure phases
is considered.
---------------------------------------------------------
Title: Seeing measurements with a pupil-plane rotation shearing
interferometer.
Authors: Roddier, C.; Roddier, F.
1987iopo.conf...77R Altcode:
A compact, very stable, rotation-shearing interferometer is used
to determine seeing quality from wavefront coherence measurements
on the telescope pupil. A change in the rotational shear enables
optimization of the instrument according to telescope size and
seeing conditions. Fringes are recorded directly on film without
intensification. Fried's seeing parameter r<SUB>0</SUB> is estimated
with a few per cent accuracy. The result of recent measurements is
presented.
---------------------------------------------------------
Title: A Fiber-Linked Groundbased Array
Authors: Connes, P.; Shaklan, S.; Roddier, F.
1987iia..conf..165C Altcode:
The authors give a preliminary discussion of what a multi-telescope
fiber-linked ground-based array might look like, and an account of
some encouraging fiber tests performed at NOAO.
---------------------------------------------------------
Title: Single Aperture Interferometry - General Introduction
Authors: Roddier, F.
1987iia..conf....1R Altcode:
The paper deals with interferometric techniques used to reconstructed
turbulence degraded images through a single telescope. The author
reviews the physical basis of these techniques and describes briefly
the present state of the art without trying to be exhaustive.
---------------------------------------------------------
Title: Imaging stellar structures and surfaces.
Authors: Roddier, Francois
1987LIACo..27..247R Altcode: 1987oahp.proc..247R
After having reviewed the basis of maximum entropy methods, the author
reviews several techniques which have been used to produce stellar
images starting from the most indirect ones. In the most direct ones,
interferometric techniques, the spatial coherence of the light is
measured and used to produce images almost as in a direct imaging
process. With the development of long baseline interferometry at
optical wavelengths, these techniques are likely to produce considerable
advances in the field of stellar physics.
---------------------------------------------------------
Title: Pupil plane versus image plane in Michelson stellar
interferometry.
Authors: Roddier, Francois
1986JOSAA...3.2160R Altcode: 1986OSAJ....3.2160R
Photon noise statistics are used to estimate the effect of image motion
or guiding errors on the signal-to-noise ratio for the fringe visibility
either in pupil-plane or in image-plane measurements. Pupil-plane
observations are found to provide better results in all cases.
---------------------------------------------------------
Title: Phase closure with rotational shear interferometers.
Authors: Roddier, Francois; Roddier, Claude
1986OptCo..60..350R Altcode:
Two rotational shear interferometers, with the shear angle of one being
twice that of the other, are employed to obtain phase closure relations
and to make possible the complete reconstruction of an incoherent
object through unknown aberrations. Complete image reconstruction
is possible with a single exposure in which two interferograms are
recorded simultaneously, and the present method is very efficient on
bright sources, though reconstruction on faint sources is possible
by averaging closure phasors over many exposures. It is noted that
multiple path integration would require many more phase closure
relations, and more than two interferometers.
---------------------------------------------------------
Title: Triple correlation as a phase closure technique
Authors: Roddier, François
1986OptCo..60..145R Altcode:
A simple heuristic model is used to discuss the relationship between
triple correlation and phase closure in interferometric image
reconstruction. The main properties of triple correlation are easily
rederived giving deeper insight into the method. <P />Operated by
the Association of Universities for Research in Astronomy, Inc.,
under contract with the National Science Foundation.
---------------------------------------------------------
Title: High Resolution Mirror Figure Estimates from Interferograms
Authors: Roddier, C.; Roddier, F.; Richardson, J.
1986BAAS...18..944R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New Observations of Alpha Orionis with a Rotation Shearing
Interferometer
Authors: Roddier, F.; Roddier, C.; Petrov, R.; Martin, F.; Ricort,
G.; Aime, C.
1986ApJ...305L..77R Altcode:
New two-dimensional maps of the visibility of fringes produced by Alpha
Orionis have been obtained at several wavelengths using the McMath
telescope at Kitt Peak in 1982 February. These maps show evidence
for a time evolution of the dust envelope and indicate a possible
stellar companion. Comparison with more recent speckle data favors
our interpretation.
---------------------------------------------------------
Title: Betelgeuse Correction
Authors: Roddier, F.
1986S&T....71..541R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Signal-to-noise ratio in differential speckle interferometry.
Authors: Petrov, R.; Roddier, F.; Aime, C.
1986JOSAA...3..634P Altcode: 1986OSAJ....3..634P
Expressions are given for the signal-to-noise ratio of the amplitude
and for the uncertainty of the phase of the cross spectrum of two
speckle images in the presence of photon shot noise. Applications to
astronomical observations are discussed.
---------------------------------------------------------
Title: Use of single-mode fibers in an optical interferometric array.
Authors: Shaklan, S.; Roddier, F.
1986JOSAA...3P...5S Altcode: 1986OSAJ....3....5S
No abstract at ADS
---------------------------------------------------------
Title: Interferometric seeing measurements at La Silla.
Authors: Roddier, Claude; Roddier, Francois
1986ESOC...24..269R Altcode: 1986vlt..work..269R
The transfer function for long-exposure astronomical images is the
product of the telescope transfer function and the wavefront coherence
function. Since coherence is best measured interferometrically,
interferometers appear to be the most appropriate tools to make
accurate estimates of seeing quality, independent of the optical
performance of the telescope. In 1975, C. Roddier used a rotational
shear interferometer, optimizing the instrument efficiency by adjusting
the angular shear to telescope size and seeing conditions. The increase
in sensitivity was so large that it became possible to record fringes
directly on Tri-X film without intensification. The instrument was
later used simultaneously with a scidar to estimate the relative
contribution of upper and lower layers in the atmosphere. The authors
describe similar measurements made at La Silla during the February
1986 site testing campaign.
---------------------------------------------------------
Title: National Optical Astronomy Observatories (NOAO) IR adaptive
optics program. III - Criteria for the wavefront sensor selection
Authors: Goad, L.; Roddier, F.; Beckers, J.; Eisenhardt, P.
1986SPIE..628..305G Altcode:
The NOAO IR Adaptive Optics Program has elected to develop a system
using the visual light from an object to sense the wavefront errors
and generate the corrections required to give diffraction-limited
imaging in the near-IR (2-10 microns). The performance of a variety
of possible sensors systems has been evaluated, computing both their
ideal performance and their expected performance with available
detectors. A major consideration in this evaluation is the ability of
the sensor to measure mean wavefront tilts of the visual wavefront
over subapertures corresponding to the (larger) IR wavefront scale
lengths. A Hartmann-Shack sensor with red-sensitive image intensifiers
and a Reticon detector are used.
---------------------------------------------------------
Title: Guidelines for a site testing campaign and the LASSCA (La
Silla Site Campaign) experience.
Authors: Roddier, F.
1986ESOC...24..261R Altcode: 1986vlt..work..261R
The application of state-of-the-art measurement techniques to the
evaluation of astronomical observatory sites is discussed, and the
methods used in the La Silla Site Campaign (LASSCA) to characterize a
prospective site for the ESO Very Large Telescope are described. The
limitations of conventional site assessments based on observations
through a moderate-size telescope are indicated; the effects of
atmospheric properties, refractive-index properties, and wavefront
properties on image properties are examined theoretically; and the
value of newly available wavefront measurements and remote-sensing
data on turbulence is stressed. LASSCA comprised seeing-disk profiles
and speckle interferograms, rotation shearing interferograms and
differential image-motion measurements, tower microthermal measurements
and acoustic soundings, scidar (Vernin and Pelon, 1985) turbulence
soundings, soil-temperature measurements, and tower and balloon data
on temperature and winds.
---------------------------------------------------------
Title: Concepts for a large telescope in space with interferometric
imaging
Authors: Bely, P. Y.; Roddier, F.
1986aiaa.meetQ....B Altcode:
A candidate for the successor to the Hubble Space Telescope is
presented. The telescope is a traditional Cassegrain with a 10-meter
diameter monolithic primary, passively cooled optics and a wavelength
coverage from the far ultraviolet to mid-infrared. Diffraction-limited
imagery is achieved in the visible and ultraviolet through
interferometric techniques. The observatory is located in the
geosynchronous orbit to minimize environmental constraints and increase
observing efficiency.
---------------------------------------------------------
Title: National Optical Astronomy Observatories (NOAO) infrared
adaptive optics program. II - Modeling atmospheric effects in adaptive
optics systems for astronomical telescopes
Authors: Roddier, Francois; Roddier, Claude
1986SPIE..628..298R Altcode:
However perfect an adaptive optical system can be, it will never
fully correct the image. The effects of amplitude errors due to
stellar scintillation, the effects of chromatic errors due to both
refraction and diffraction in a two-wavelength system, and the effects
of nonisoplanicity, are presently discussed. All these errors are
directly related to the height of turbulence layers. An expression is
derived for the scale height of turbulence, which should be considered
as an important parameter in selecting new sites for astronomical
observations. The performance of adaptive optical systems is usually
described in terms of Strehl ratios. The results of computations of
the whole transfer function for long exposure compensated images are
presented. It is shown that the point-spread function for a partially
compensated image generally consists of an Airy disk surrounded with a
halo. The ratio of the energy in the Airy disk over the energy in the
halo is independent of the telescope aperture and provides a better
measure of the quality of the compensation.
---------------------------------------------------------
Title: National Optical Astronomy Observatories / NOAO / Infrared
Adaptive Optics Program - Part Four - Infrared Background Speckle
Noise Induced by Adaptive Optics in Astronomical Telescopes
Authors: Roddier, F.; Eisenhardt, P.
1986SPIE..628..314R Altcode:
The infrared emission of astronomical sources is buried in a large
background due to the thermal emission of the telescope. The real time
deformations of an adaptive flexible mirror are likely to produce a
spurious modulation of this background, adding noise to the signal. The
authors estimate the amount of noise introduced by such a mirror.
---------------------------------------------------------
Title: Fiber-coupled interferometric imaging array.
Authors: Roddier, F.
1986JOSAA...3P...6R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fiber-coupled interferometric imaging array (A)
Authors: Roddier, Francois
1986JOSAA...3....6R Altcode: 1986OSAJ....3....6R
No abstract at ADS
---------------------------------------------------------
Title: National Optical Astronomy Observatories (NOAO) infrared
adaptive optics program. I - General description
Authors: Beckers, Jacques M.; Roddier, Francois J.; Eisenhardt,
Peter R.; Goad, Larry E.; Shu, Ker-Li
1986SPIE..628..290B Altcode:
The authors describe the general principles behind a polychromatic
adaptive optics program for astronomy. In this program the atmospheric
wavefront distortions are measured at visible wavelengths (700 nm)
using an astronomical object in the vicinity of the infrared object of
interest. The resulting wavefront corrections are applied to an infrared
imaging system which utilizes a two-dimensional detector array. The
authors describe the principles of this adaptive optics system.
---------------------------------------------------------
Title: IR Background Speckle Noise Induced by Adaptive Optics in
Astronomical Telescopes
Authors: Eisenhardt, P.; Roddier, F.
1985BAAS...17Q.901E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An image reconstruction of alpha Orionis.
Authors: Roddier, F.; Roddier, C.
1985ApJ...295L..21R Altcode:
A description is given of an attempt to reconstruct an image of the star
Alpha Orionis from a map of fringe visibilities obtained on November 30,
1980 with the CFH Telescope in Hawaii. The maximum entropy algorithm
proposed by Gull and Daniell (1978) was used. The data were obtained
through a 90 A bandwidth filter centered at 5350 A - a window chosen
because it avoids strong molecular absorption bands in the stellar
spectrum. The interferometric image reconstruction indicates that dust
condensation may well occur close to the stellar disk.
---------------------------------------------------------
Title: High Angular Resolution Interferometric Observations of
Betelgeuse in the Visible
Authors: Roddier, F.; Roddier, C.; Karovska, M.
1985ASSL..117...63R Altcode: 1985mlrg.proc...63R
A new high angular resolution interferometric technique, based on
pupil plane observation and rotation shearing of the wavefront, has
been developed in the authors' laboratory and compares favorably with
speckle interferometry. A two-dimensional map of the visibility of the
fringes produced by Betelgeuse has been obtained from data recorded
at the C.F.H. telescope on November 30, 1980, in the continuum at λ =
5348 Å. The map (C. Roddier and F. Roddier, 1983) shows evidence for
departure from circular symmetry. It has been interpreted as produced
by a stellar disk surrounded with an irregular envelope. The authors
present here an attempt to reconstruct an image from these data.
---------------------------------------------------------
Title: On a Possible Close Companion to αOri
Authors: Karovska, M.; Noyes, R. W.; Roddier, F.; Nisenson, P.;
Stachnik, R. V.
1985BAAS...17..598K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Polychromatic Adaptive Optics for Infrared Telescopes
Authors: Beckers, J. M.; Eisenhardt, P.; Goad, L.; Roddier, F.
1985BAAS...17R.571B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: IR background speckle noise induced by adaptive optics in
astronomical telescopes.
Authors: Roddier, F.; Eisenhardt, P.
1985SPIE..556..248R Altcode:
The infrared emission of astronomical sources is buried in a large
background due to the thermal emission of the telescope. The real time
deformations of an adaptive flexible mirror are likely to produce a
spurious modulation of this background, adding noise to the signal. The
authors estimate the amount of noise introduced by such a mirror.
---------------------------------------------------------
Title: Long-baseline Michelson interferometry with large ground-based
telescopes operating at optical wavelengths. II. Interferometry at
infrared wavelengths.
Authors: Roddier, F.; Lena, P.
1984JOpt...15..363R Altcode: 1984JOp....15..363R
The theoretical bases, techniques, and instrumentation applied
in long baseline interferometry of astrophysical objects at IR
wavelengths are surveyed. Light detection is carried out with single
photoelectric sensors functioning in the 1-30 microns window or
with one- or two-dimensional CCD device grids which measure the
incoming flux. Numerical expressions have been devised to account
for single-photon, background and detector intrinsic noise sources
and standard noise values have been calculated for each. The
SNR and phase stability of sensed image fringes determine if the
photoelectric analysis will proceed by synchronous detection or
quadratic detection, respectively. The interference will be analyzed
either in the image or in terms of the registration on the pupil plane
of the detector. Techniques for estimating the image spectral density
and limiting magnitudes are reviewed. Applications of long-baseline
systems to studying asteroids, comets, star formation, and galactic
nuclei are discussed, noting the large advantages available in visible
wavelength studies if the instrumentation was space-based.
---------------------------------------------------------
Title: Long-baseline Michelson interferometry with large
ground-based telescopes operating at optical wavelengths. I. General
formalism. Interferometry at visible wavelengths.
Authors: Roddier, F.; Lena, P.
1984JOpt...15..171R Altcode: 1984JOp....15..171R
Present knowledge on long baseline interferometry with large telescopes
is reviewed, and reasonable estimates are made of the performances which
may be expected in the visible range using this technique. The general
formalism of this interferometric scheme is discussed, with a detailed
examination of aperture size effects. The time and chromatic dependences
are presented. Michelson interferometry at visible wavelengths is
addressed, including the estimation of the image energy spectrum and
of the limiting magnitude, the limits of present technology, and the
potential of the technique.
---------------------------------------------------------
Title: PM. 09 Interferometric Image Reconstruction Using the
L. D. R. in a Light Bucket Mode
Authors: Roddier, F.; Breckinridge, J. B.
1984BAAS...16..832R Altcode:
The application of a rotational shear interferometer to the large
deployable reflector may lead to very high spatial resolution image
reconstruction. It is shown that interferometric techniques could
extend the imaging capabilities of the reflector down to the visible
where complete image reconstruction, with an angular resolution limit
of a few milliarcseconds, may still be achieved to stellar magnitudes
as faint as 21.
---------------------------------------------------------
Title: Distributions et transformation de Fourier a l'usage des
physiciens et des ingenieurs
Authors: Roddier, F.
1984detd.book.....R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Review on Increase in Spatial Resolving Power
Authors: Roddier, F.
1984apoa.conf...22R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Special requirements for high angular resolution
interferometry.
Authors: Roddier, F.
1984ESOC...18..193R Altcode: 1984stfl.work..193R
Stringent conditions imposed on the optical quality of the earth's
atmosphere by interferometric imaging techniques are reviewed. It is
suggested that these conditions be taken into account in any future
site testing campaign. Consideration is given to seeing parameters
relevant to interferometric imaging, statistics of Fried's parameter,
the life time of fringes and speckles, the isoplanatic angle, the
turbulence outerscale, and the application to site testing.
---------------------------------------------------------
Title: Measuring atmospheric seeing
Authors: Roddier, F.
1984vlti.conf..191R Altcode: 1984vlts.coll..191R; 1984IAUCo..79..191R
The techniques available for measurement of image plane, pupil plane,
turbulence, and meteorological parameters are reviewed, and their
relative merits with respect to applications are assessed. It is
inferred that image plane measurements are best suited for correcting
observations for image degradation. Pupil plane measurements, on the
other hand, are more accurate for comparing seeing conditions between
telescopes and sites. Several methods of remote turbulence sounding
are also evaluated, including sodar, radar, and Scidar (stellar
scintillation sounder). It is suggested that to improve image quality,
a combination of remote sensing techniques and pupil plane measurements
is most appropriate.
---------------------------------------------------------
Title: High angular resolution observations of alpha Orionis with
a rotationshearing interferometer.
Authors: Roddier, C.; Roddier, F.
1983ApJ...270L..23R Altcode:
A two-dimensional map of the visibility of fringes produced by α
Orionis through a rotation shearing interferometer is presented. It
shows evidence for a circumstellar envelope and for departure from
circular symmetry.
---------------------------------------------------------
Title: Testing seeing quality
Authors: Roddier, F.
1983ESOC...17..255R Altcode: 1983vlt..work..255R
Problems of good telescope site location to solve image degradation
are discussed. Differences between dome seeing, which is related
to turbulence within the instrument, and atmospheric seeing which is
related to image degradation due to the fluctuations of the atmospheric
reflective index are analyzed, stressing the need for an appropriate
choice of telescope location. Methods for site testing are presented
considering three types of parameters: meteorological (pressure,
temperature, and wind profiles), turbulence, and optical (speckle life
time and Fried parameter). Good turbulence profiles yield reliable
estimates of the image quality and techniques measuring these profiles
are covered in detail. Although in situ measurements can be done they
are cumbersome, while remote sensing through use of optical sensors
seems the most promising. These techniques not only provide accurate
estimates of optical quality of the atmosphere but also reveal the
atmospheric layers which contribute to image degradation. Relating
these turbulent layers to meteorological data yields better estimates
of their occurrence frequency and gives hints on how to possibly avoid
them by an appropriate site selection.
---------------------------------------------------------
Title: Future possibilities of ground-based interferometry in
the visible
Authors: Roddier, F.
1983ESOC...17..155R Altcode: 1983vlt..work..155R
Attention is given to the performance claims and other relative
advantages of three main classes of telescope configurations that
have been proposed to increase light collecting area: (1) a single
giant telescope of about 16 meter aperture, employing either a single
segmented mirror or multiple mirrors, (2) a limited number of large
telescopes of approximately 8 m aperture having thin, servocontrolled
mirrors, and (3) a large array of 16 telescopes of 4 m aperture. The
choice of the most advantageous system is made on the basis of high
angular resolution interferometry's requirements, whose criteria
include angular resolution, Fourier plane coverage, limiting magnitude,
accuracy, and imaging capability.
---------------------------------------------------------
Title: On the origin of speckle boiling and its effects in stellar
speckle interferometry.
Authors: Roddier, F.; Gilli, J. M.; Lund, G.
1982JOpt...13..263R Altcode: 1982JOp....13..263R
An optimum exposure time is formulated for speckle interferometric
observations of stellar objects. The exposure interval is constrained
by the need to stop as soon as the speckle pattern of the object is
captured, yet the aperture must remain open long enough to adequately
view what are nominally faint sources. It is shown that the optimum
exposure time is related to the time scale of speckle boiling or
speckle lifetime. The speckle lifetime is demonstrated to be limited
to the ratio of Fried's parameter (1966) to the standard deviation of
the wind velocities distribution and the atmospheric turbulence of
the earth atmosphere. Theoretical investigations of the effect of a
finite exposure time, the space-time correlation of speckle patterns,
the wavefront boiling time, and Michelson interferometry and adaptive
optics are presented. The results of a laboratory simulation of
astronomical speckle boiling are presented, and found to agree with
previous works. The effects of atmospheric turbulence being concentrated
in a single layer are discussed.
---------------------------------------------------------
Title: On the isoplanatic patch size in stellar speckle
interferometry.
Authors: Roddier, F.; Gilli, J. M.; Vernin, J.
1982JOpt...13...63R Altcode: 1982JOp....13...63R
No abstract at ADS
---------------------------------------------------------
Title: How to achieve diffraction limited resolution with large
space telescopes
Authors: Roddier, F.
1982AdSpR...2d...3R Altcode: 1982AdSpR...2R...3R
Large space telescopes cannot be made diffraction-limited at least for
short wavelengths. Methods for reconstructing diffraction-limited
images are reviewed including active optics, Michelson stellar
interferometry, non-redundant aperture arrays, deconvolution and
shearing interferometry. Expressions are given for the signal-to-noise
ratio in each case and the result of laboratory simulations are
presented. It is concluded that diffraction-limited images could
be obtained in the visible up to magnitude 21 with large deployable
reflectors planned to be used in the far I.R. or millimetric range.
---------------------------------------------------------
Title: High angular resolution with rotation shearing interferometers:
preliminary results and future potentials.
Authors: Roddier, F.; Roddier, C.
1982ASSL...92..207R Altcode: 1982IAUCo..67..207R; 1982ialo.coll..207R
A rotation-shearing interferometer has been designed and constructed
which consists of a beam-splitting cube and two phase-compensated
roof prisms giving high-contrast, high-luminosity fringes at any
rotation angle. A chromatic lens system provides a pupil image
with a magnification proportional to the inverse of the wavelength
thus permitting the use of large optical bandwidths; the bandwidth
is limited by turbulence to a few hundred Angstroms as in speckle
interferometry. Visual estimates of the diameter of the star Betelgeuse
(alpha Ori) at 10 wavelengths are presented; observations of other
stars are also briefly discussed.
---------------------------------------------------------
Title: Rotation interferometry: a new technique for achieving high
angular resolution.
Authors: Roddier, C.; Roddier, F.; Vernin, J.
1981siha.conf..165R Altcode: 1982siha.conf..165R
No abstract at ADS
---------------------------------------------------------
Title: Atmospheric limitations to high angular resolution imaging.
Authors: Roddier, F.
1981siha.conf....5R Altcode: 1982siha.conf....5R
The statistics of wavefront perturbations are reviewed, their
implications for high-angular resolution imaging are discussed, and
expressions are given for the signal-to-noise ratios and the limiting
magnitudes in several cases. The described coherence properties of
wavefront perturbations include the probability density function,
spatial coherence, spatio-temporal coherence, spatio-angular coherence,
and spectral coherence. The SNR in high resolution imaging is addressed,
including the SNR in the image spectrum, the energy transfer function,
the effect of pupil redundancy and sampling, the minimum integration
time, and the limiting stellar magnitude in the visible.
---------------------------------------------------------
Title: The effects of atmospheric turbulence in optical astronomy
Authors: Roddier, F.
1981PrOpt..19..281R Altcode:
Atmospheric turbulence is examined in terms of its effects on
optical astronomy. The statistical properties of atmospheric
turbulence are explored, considering structure, temperature and
humidity fluctuations, and the dependence of the contribution
of turbulence to optical propagation with height and time. The
statistical properties of the perturbed complex field are analyzed
for the output of a thin turbulent layer, multiple and thick layers,
and fourth order moments. Long exposure images are considered for the
relation between the object and the image, for an expression of the
optical transfer function, for resolving power, and for application to
Michelson's stellar interferometry. Short exposure images vary with
the image energy spectrum and the probability density functions of
stellar speckles. Attention is also given to the effects of exposure
time and nonisoplanicity effects, optical path fluctuations, stellar
scintillation, and applications to high resolution imaging. It is noted
that astronomical instruments may become useful for atmospheric remote
sensing, as is now done for stellar scintillation.
---------------------------------------------------------
Title: Twin-image holography with spectrally broad light
Authors: Roddier, C.; Roddier, F.; Martin, F.; Baranne, A.; Brun, R.
1980JOpt...11..149R Altcode:
The bandwidth limitation to incoherent twin-image holography is
examined, and a solution to the problem for the reconstruction and
recording of turbulence- or aberration-degraded astronomical images is
presented. The maximum usable bandwidth to prevent chromatic blurring
is shown to vary inversely with the total number of pixels in the
reconstructed image; however, it is noted that the use of very short
exposures in the restoration of turbulence-degraded images favors an
increase in bandwidth. Previously designed achromatic interferometers
are indicated, and it is pointed out that the chromatic effect in the
hologram irradiance distribution disappears if an image is produced
in front of the interferometer with a magnification proportional to
the wavelength, as in rotation shearing interferometry. A chromatic
lens system based on two meniscus lenses providing a chromatic change
in magnification is outlined, and experimental results obtained with
the system and demonstrating the utility of the system in increasing
fringe numbers are presented.
---------------------------------------------------------
Title: New trends in stellar speckle interferometry.
Authors: Roddier, F.
1980SPIE..243...83R Altcode:
Recent advances are presented of the stellar speckle interferometer
technique, with particular attention given to (1) the extension of
the technique to infrared wavelengths, (2) improved calibration of
atmospheric effects, and (3) an improved understanding of atmospheric
effects. Arrays of detector elements are now available, but they
are extremely expensive. Theoretical estimates of the modulation
transfer function can be obtained from numerical computations, assuming
log-normal statistics for the wavefront perturbations, which was first
done by Korff (1973). Improved calculations, which take the central
telescope obstruction into account, were made by Roddier (1979) and
were found to be in good agreement with the photoelectric measurements
made by Aime et al. (1979) in the visible, as well as with infrared
measurements obtained by Chelli et al. (1979). The discussion of the
atmospheric effects includes the effects of a single thin turbulent
layer at a certain altitude above the telescope, moving at a certain
wind velocity.
---------------------------------------------------------
Title: Observations of the Sun with interferometry and
speckle-interferometry techniques
Authors: Roddier, F.
1980fsoo.conf...96R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle and Intensity Interferometry. Applications to Astronomy
Authors: Roddier, F.
1980LNP...112..344R Altcode: 1980ipcp.conf..344R
No abstract at ADS
---------------------------------------------------------
Title: Statistical determination of a morphological parameter in
solar granulation: spatial distribution of granules.
Authors: Aime, C.; Martin, F.; Grec, G.; Roddier, F.
1979A&A....79....1A Altcode:
Summary. This article is concerned with the study of morphological
properties of solar granulation, which are derived from two dimensional
harmonic (power spectrum) analysis of the granule position. By
use of a morphological model for the granulation, it is shown that
the deviations in granules positions from an hexagonal reference
structure (Benard Cells) have a gaussian distribution. A mathematical
analysis demonstrates that the histograms of intergranular separation
found in various literature may be interpreted as Rice-Nakagami
distributions. The usefulness of such harmonic techniques is shown
for research into ordered or quasi-periodic structures. Key words:
solar granulation - harmonic analysis - morphology
---------------------------------------------------------
Title: Modulation Transfer Function for Infra-red Stellar Speckle
Interferometry: Evidence for a Log-normal Statistic
Authors: Chelli, A.; Lena, P.; Roddier, C.; Roddier, F.; Sibille, F.
1979AcOpt..26..583C Altcode: 1979JMOp...26..583C
No abstract at ADS
---------------------------------------------------------
Title: Rotation-shearing interferometry
Authors: Roddier, F.
1979hars.proc...32R Altcode: 1979IAUCo..50...32R
An approach toward correcting wavefront errors, imaging with a coherence
interferometer, is presented. This consists of post detection processing
of interferograms in the pupil space. While similar to Michelson
interferometry, it allows observation of all the Fourier components of
the image at the same time. Imaging through fixed aberrations is covered
noting that the signal to noise ratio in incoherent holograms decreases
as the square root the number of resolved pixels in the image. Imaging
through turbulence is demonstrated with a double point source as
the object. While none of the images shows a resolved structure, the
double point source is clearly resolved in the restored image with a
correct ratio of intensities between the two point sources. Finally,
astronomical applications are discussed including use with the 1.52
m telescope of the Haute Provence Observatory.
---------------------------------------------------------
Title: Imaging with a Coherence Interferometer in Optical Astronomy
Authors: Roddier, C.; Roddier, F.
1979ASSL...76..175R Altcode: 1979ifcf.coll..175R; 1979IAUCo..49..175R
A technique of imaging with a coherence interferometer is described
which consists of postdetection processing of interferograms in the
pupil space. This technique, also called incoherent holography, consists
of observing the interference pattern produced by two superimposed
images of the telescope pupil, one being rotated with respect to the
other. Imaging through fixed aberrations and imaging through turbulence
are discussed.
---------------------------------------------------------
Title: The effects of atmospheric turbulence on the formation of
visible and infrared images.
Authors: Roddier, F.
1979JOpt...10..299R Altcode: 1979JOp....10..299R
The paper briefly reviews the properties of atmospheric turbulence
relevant to image formation. Statistics of associated wavefront
perturbations are described, and their consequences are examined for
both classical and interferometric imaging.
---------------------------------------------------------
Title: Observations of the sun with interferometry and
speckle-interferometry techniques.
Authors: Roddier, F.
1979MmArc.106...96R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Estimation errors for the covariance determination of
stationary and ergodic stochastic processes with a nonzero mean value.
Authors: Martin, F.; Borgnino, J.; Aime, C.; Ricort, G.; Roddier, F.
1979JOpt...10...99M Altcode: 1979JOp....10...99M
No abstract at ADS
---------------------------------------------------------
Title: Defocusing effects in astronomical speckle interferometry
Authors: Roddier, F.; Ricort, G.; Roddier, C.
1978OptCo..24..281R Altcode:
Theoretical transfer functions for astronomical speckle interferometry,
through a defocused telescope, have been computed assuming a log-normal
complex amplitude for the incoming wavefront. They are found to be in
reasonable agreement with recently published observations. The theory
also applies to the effect of astigmatism.
---------------------------------------------------------
Title: Observations of the Sun with interferometry and speckle
interferometry techniques
Authors: Roddier, F.
1978fsoo.conf...96R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Experiments for large multi-mirror telescopes. I.- Detection
of non radial stellar oscillations.
Authors: Roddier, F.; Fossat, E.; Grec, G.; Roddier, C.
1978otf..conf..357R Altcode:
Preliminary measurements made with a 2-m telescope equipped with a
sodium cell have shown that nonradial oscillations similar to the
solar 5-min oscillations could be detected on bright stars with an
integration time of three hours and a 5-m telescope. Because of their
aberrations, large optical telescopes of the future will act as light
collectors rather than imaging devices. An analysis demonstrates how
interferometric techniques can be used to obtain good images with a
multi-mirror telescope.
---------------------------------------------------------
Title: Experiments for large multi-mirror telescopes. II.- Imaging
with a multi-mirror telescope.
Authors: Roddier, F.; Roddier, C.
1978otf..conf..359R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: One-dimensional stellar and solar speckle interferometry
Authors: Aime, C.; Roddier, F.
1977OptCo..21..435A Altcode:
A new technique called “one-dimensional speckle-interferometry”
is analysed. It appears to be a good compromise between standard
speckle-interferometry and Michelson interferometry for precise,
high resolution astronomical measurements.
---------------------------------------------------------
Title: Defocusing effects in astronomical speckle interferometry.
Authors: Roddier, F.; Ricort, G.; Roddier, C.
1977OptCo..24..281R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Seeing effects removal in a Michelson stellar interferometer.
Authors: Roddier, C.; Roddier, F.
1976JOSA...66.1347R Altcode: 1976OSAJ...66.1347R
There is no unique definition of the fringe contrast in a
random structure such as the image given by a Michelson stellar
interferometer. A definition is given which leads to a contrast
value independent of the seeing conditions provided the wave-front
perturbations on the two apertures are uncorrelated. Moreover, if
simultaneous observations through a single aperture are available,
the seeing effects can be completely removed.
---------------------------------------------------------
Title: Imaging through turbulence with telescope arrays
Authors: Aime, C.; Roddier, F.
1976OptCo..19...57A Altcode:
By applying speckle-interferometry technique to the synthetic image
given by an array of large telescopes, quantitative measurements of
object power-spectra can be made in spite of atmospheric turbulence,
provided the apertures are sufficiently apart so that the wave-front
perturbations remain uncorrelated. The signal-to-noise ratio depends
upon the redundancy of the array.
---------------------------------------------------------
Title: On the fringe visibility in a Michelson stellar interferometer.
Authors: Roddier, C.; Roddier, F.
1976JOSA...66..580R Altcode: 1976OSAJ...66..580R
Speckle interferometry theory is applied to Michelson
interferometry, and the fringe contribution in the stellar image
Wiener spectrum is calculated as a function of aperture diameter
and seeing conditions for an unresolved star. Computing the Wiener
spectrum for a turbulence-degraded point-source image facilitates
quantitative determination of fringe visibility in Michelson stellar
interferometry. Fringe contributions to the image Wiener spectrum
become independent of aperture diameters at large apertures. The results
encourage the use of long-baseline Michelson interferometry with large
telescopes for quantitative measurements of very-small-scale light
distributions in stellar sources, with negligible image degradation
by atmospheric turbulence.
---------------------------------------------------------
Title: Treatment of astronomical images degraded by atmospheric
fluctuations.
Authors: Roddier, F.
1976RvPA...11..195R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effects of the atmosphere in stellar speckle interferometry.
Authors: Roddier, F.; Roddier, C.
1976JOSA...66..181R Altcode: 1976OSAJ...66..181R
No abstract at ADS
---------------------------------------------------------
Title: The treatment of astronomical images degraded by atmospheric
fluctuations.
Authors: Roddier, F.
1975AnTel..30..304R Altcode:
Atmospheric turbulence can produce speckle distortion in astronomical
images. Various methods, based on phase reconstruction and speckle
interferometry, are discussed for restoring images thus distorted. It
is shown that complete restoration is theoretically possible by means
of incoherent-light holography.
---------------------------------------------------------
Title: Principle of production of an acoustic hologram of the
solar surface
Authors: Roddier, F.
1975CRASB.281...93R Altcode:
A procedure is described which permits point-by-point
photographic recording of the complex amplitude of photospheric
oscillations. Examination of such holograms in coherent light could
lead to a visualization of subjacent acoustic sources. The method
is based on a previous investigation by Sheeley and Bhatnagar (1971)
employing Doppler photography.
---------------------------------------------------------
Title: Influence of exposure time on spectral properties of
turbulence-degraded astronomical images.
Authors: Roddier, C.; Roddier, F.
1975JOSA...65..664R Altcode: 1975OSAJ...65..664R
No abstract at ADS
---------------------------------------------------------
Title: Atmospheric turbulent layers localisation by optical processing
of stellar shadow pattern
Authors: Martin, F.; Borgnino, J.; Roddier, F.
1975NROpt...6...15M Altcode:
An optical information processing technique, commonly used for
speckle-pattern analysis, is applied to the study of the motion of
shadow patterns associated with stellar scintillation. The intensities
of the diffraction patterns produced by several double-exposure
photographs are added on a single plate. Interference fringes are
observed at right angles to the direction of displacement. Fringe
spacing is inversely proportional to the speed of motion. By fitting
the velocity deduced from fringe measurements to the results of
meteorological wind soundings, an approximate altitude is obtained
for the atmospheric turbulence layers producing stellar scintillation.
---------------------------------------------------------
Title: Détection au sol de la turbulence stratosphérique par
intercorrélation spatioangulaire de la scintillation stellaire.
Authors: Vernin, J.; Roddier, F.
1975CRASB.280..463V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Evidence for Large-Scale Oscillations of the Solar Photosphere
Authors: Fossat, E.; Ricort, G.; Aime, C.; Roddier, F.
1974ApJ...193L..97F Altcode:
Doppler shifts of the Na D1 line, averaged over large solar areas up to
the whole sun, have been recorded with a sodium resonance device. The
power spectra of the observed fluctuations show that (1) the 5-minute
oscillation has an horizontal coherence of 35,000 km at the level of
the sodium line formation; (2) the corresponding peak at 3.3 mHz is
not predominant for scales greater than 5'. New oscillations appear
with a 10-minute period.
---------------------------------------------------------
Title: Detection of atmospheric turbulent layers by spatiotemporal and
spatioangular correlation measurements of stellar-light scintillation.
Authors: Rocca, A.; Roddier, F.; Vernin, J.
1974JOSA...64.1000R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle interferometry through small multiple
apertures. Michelson stellar interferometer and aperture synthesis
in optics.
Authors: Roddier, F.
1974OptCo..10..103R Altcode:
The use of a Michelson stellar interferometer or multiple-hole
interferometers is considered as a special case of speckle
interferometry. Formulas are given for the power spectrum of the
interference pattern produced by the multiple apertures. The limitation
in stellar magnitude is shown to increase with the number of apertures,
while it is independent of the telescope size when a large single
aperture is used.
---------------------------------------------------------
Title: Correlation measurements on the complex amplitude of stellar
plane waves perturbed by atmospheric turbulence
Authors: Roddier, C.; Roddier, F.
1973JOSA...63..661R Altcode: 1973OSAJ...63..661R
The mutual coherence function (MCF) of the complex amplitude of stellar
light waves perturbed by atmospheric turbulence has been determined
interferometrically. Results are in good agreement with horizontal
laser-beam determinations. Stellar measurements provide quantitative
estimations of seeing conditions for astronomical observations.
---------------------------------------------------------
Title: Experimental determination of two-dimensional spatiotemporal
power spectra of stellar light scintillation. Evidence for a
multilayer structure of the air turbulence in the upper troposphere.
Authors: Vernin, J.; Roddier, F.
1973JOSA...63..270V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Sodium Experiment for Photospheric Velocity Field
Observations
Authors: Fossat, E.; Roddier, F.
1971SoPh...18..204F Altcode:
A method for studying small scale photospheric velocity fields with
a balloon experiment is proposed. A sodium resonance cell is used
with a diffraction limited telescope. Good pointing accuracy is not
necessary. Preliminary results of ground-based observations are given.
---------------------------------------------------------
Title: A Model of the Solar Photospheric Velocity Field
Authors: Gonczi, G.; Roddier, F.
1971A&A....11...28G Altcode:
The velocity field in the solar photosphere is determined from an
analysis of the geometrical properties (asymmetry and general shape)
of the profiles of the Sr 4607 line observed by Roddier (1965) with
an atomic beam spectrograph. Below an optical depth of 4 x 10-8 (at
5000 A), the adopted model has two adjacent columns with different
microturbulence which is anisotrope and increasing with depth. The
column with the smallest microturbulence rises with a velocity of
0.7 km/s and the other one descends with a velocity of 0.3 km/s. This
model gives profiles of Sr 14607 from the centre to the limb of the
solar disk which are in good agreement with the experimental ones,
and it is also in good agreement with some recent observations of the
photospheric microstructures. Key words: velocity field - turbulence -
convection - microturbulence - line profile
---------------------------------------------------------
Title: Line Profiles in Sunspot Umbrae and Penumbrae by Atomic
Beam Spectroscopy
Authors: Roddier, F.
1971IAUS...43..249R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interpretation of the East-West Asymmetry of the Initial
Appearance of Sunspots
Authors: Rix, H.; Roddier, F.
1970A&A.....9..301R Altcode:
The East-West asymmetry in the initial appearance of s'mspots is
explained, assuming that sunspots begin to form at a level deeper
than optical depth unity and move towards the surface of the s'm,
by the variation of the photospheric opacity with height combined
with the variation of the heliocentric angle as the observation moves
from the centre to the limb. This contribution to the asymmetry is
the same order of magnitude as the contribution from the classical
"foreshortening effect". A conical model of a sunspot is used to include
the contribution of these two effects. A comparison of the theory with
the observed East-West asymmetry gives a mean ascentional velocity
of the sunspots of 3 m/s. This comparison gives further evidence that
the evolution of some sunspots is interrupted.
---------------------------------------------------------
Title: A Fourier Spectrum Analysis of Long Samples of Solar Line
Oscillations
Authors: Gonczi, G.; Roddier, F.
1969SoPh....8..255G Altcode:
Sequences of the oscillations of solar lines up to 2 hours 20 min long
have been recorded at the same point on the sun. The power spectra show
several peaks separated by 0.85 × 10<SUP>−3</SUP> cps on average
from each other. A sharp main peak at 3.3 × 10<SUP>−3</SUP> cps
(300 sec period) is almost always present.
---------------------------------------------------------
Title: Observation of the Solar Line Oscillations with an Atomic-Beam
Spectro-Photometer
Authors: Roddier, F.
1967ApJ...147.1113R Altcode:
An atomic-beam resonance spectrophotometer has been used with the
McMath solar telescope to observe the 300-sec oscillation of velocity
in photospheric granules. The Sr 4607 line profile periodically changes
between a symmetric profile at the expected wavelength and an asymmetric
one shifted to the violet.
---------------------------------------------------------
Title: Étude à haute résolution de quelques raies de Fraunhofer
par observation de la résonance optique d'un jet atomique. III
Authors: Roddier, F.
1966AnAp...29..639R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Sodium D Lines in Comet Ikeya-Seki
Authors: Livingston, W.; Roddier, F.; Spinrad, H.; Slaughter, C.;
Chapman, D.
1966S&T....31...24L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Microturbulence Above the Hydrogen Convection Zone
Authors: Roddier, F.
1966IAUTB..12..553R Altcode:
No abstract at ADS
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Title: Micromotions, Macromotions, and Non-LTE Effects
Authors: Pecker, J. -C.; Roddier, F.
1965SAOSR.174..437P Altcode:
No abstract at ADS
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Title: Étude à haute résolution de quelques raies de Fraunhofer par
observation de la réponse optique d'un jet atomique. I. Réalisation
d'un spectrographe à jet atomique.
Authors: Roddier, F.
1965AnAp...28..463R Altcode:
No abstract at ADS
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Title: Étude à haute résolution de quelques raies de Fraunhofer par
observation de la réponse optique d'un jet atomique. II. Résultats
des observations solaires
Authors: Roddier, F.
1965AnAp...28..478R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Etude à Haute Résolution du Profil de la Raie λ = 4607.3
Å du Strontium Neutre en Différents Points du Disque Solaire et
Mesure des Longeurs d'Onde au Spectrographe à Jet Atomique
Authors: Blamont, J. E.; Roddier, F.
1964CRASB.258..449B Altcode:
No abstract at ADS
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Title: Precise Observation of the Profile of the Fraunhofer Strontium
Resonance Line. Evidence for the Gravitational Red Shift on the Sun
Authors: Blamont, J. E.; Roddier, F.
1961PhRvL...7..437B Altcode:
No abstract at ADS
