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1. Solar wavefront sensing at THEMIS with self-calibrated reference image and estimation of the noise covariance

Author

Michel Tallon, Éric M. Thiébaut, Isabelle Tallon-Bosc, Bernard F. Gelly, Loïc Denis, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Télescope héliographique pour l'étude du magnétisme et des instabilites solaires (THEMIS), Centre National de la Recherche Scientifique (CNRS), Laboratoire Hubert Curien (LHC), Institut d'Optique Graduate School (IOGS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laura Schreiber, Dirk Schmidt, and Elise Vernet

Subjects
solar adaptive optics, [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], solar wavefront sensing, Shack-Hartmann wavefront sensor, inverse problem, real-time control, unsupervised methods
Abstract

International audience; For a solar adaptive optics system equipped with a Shack-Hartmann wavefront sensor, the local wavefront slopes are measured from the displacements of the images produced by the sub-pupils of the sensor with respect to a given reference image. Measuring these displacements is challenging because of the very low contrast (at most a few percent) of the structures at the Sun surface. Additional difficulties arise from the fact that these structures evolve in time and are slightly distorted in each sub-image. In this contribution, we describe a novel approach to process the images of a solar wavefront sensor which jointly estimates the wavefront slopes, their noise covariance matrix, and the reference image. Spatio-temporal constraints are imposed on the reference image to regularize the problem and stabilize the global tip-tilt. Automatically tuned correction factors are introduced to account for the scintillation and the local distortions. Our method yields a sufficient statistic which enables an optimal wavefront reconstruction. We propose an alternating strategy to quickly solve the joint estimation problem. Special attention has been paid to make the numerical algorithm usable in real-time. Our method is implemented in the adaptive optics system of the THEMIS solar telescope equipped with a 10 × 10 Shack-Hartmann wavefront sensor delivering 400 × 400 pixel images at 1kHz. On a single CPU core, the Julia version of our algorithm provides the measurements with 90μs of latency after the image acquisition and takes an additional 200µs to update the reference image.

Published
2022
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2. The evanescent wave coronagraph project: development status and potential for space based observations

Author

Thierry Lepine, Boonrucksar Soonthornthum, Isabelle Tallon-Bosc, Eric Thiébaut, Michel Tallon, Christophe Buisset, Mary Angelie Alagao, Yves Rabbia, Saran Poshyachinda, Maud Langlois, National Astronomical Research Institute of Thailand (NARIT), Laboratoire Hubert Curien [Saint Etienne] (LHC), Université Jean Monnet [Saint-Étienne] (UJM)-Centre National de la Recherche Scientifique (CNRS)-Institut d'Optique Graduate School (IOGS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire Gemini (LG), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Zoran Sodnik, Nikos Karafolas, Bruno Cugny, Laboratoire Hubert Curien (LHC), Institut d'Optique Graduate School (IOGS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Total internal reflection, [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], business.industry, Exoplanets, Evanescent Wave, Strehl ratio, 01 natural sciences, Exoplanet, law.invention, Telescope, Wavelength, Optics, Apodization, Tunneling effect, law, 0103 physical sciences, Adaptive Optics, 010306 general physics, Adaptive optics, business, High Angular Resolution, 010303 astronomy & astrophysics, Coronagraph, Coronagraphy
Abstract

International audience; The Evanescent Wave Coronagraph (EvWaCo) is a coronagraph with an occulting mask based on the frustration of total internal reflection to i) produce an achromatic extinction of the central star and ii) reveal the faint companion surrounding the star. Results obtained in laboratory conditions show contrast performance of a few 10-6 between 10 λC/D and 20 λC/D over the full I-band centered at the wavelength λC = 800 nm with a spectral ratio of Δλ/ λC ≈ 20% in unpolarized light.In this paper, we discuss the advantages of using EvWaCo to observe and characterize exoplanets with a space-based telescope. In the first section, we describe the system and present the current results obtained with the EvWaCo testbed. We also illustrate the capability of this coronagraph to detect the companion 30,000 times (respectively, 100,000 times) fainter than the central star at distances equal to 15 Airy radii (respectively, 30 Airy radii) from the PSF center in polychromatic and unpolarized light.In the second section, we describe the design of the prototype dedicated to the on-sky tests of the instrument with the 2.4 m Thai National Telescope at horizon 2020. This prototype has been designed with the objective to reach a contrast equal to a few 10-4 at the inner working angle (IWA) equal to 3 λ/D from the star PSF center while observing through the atmosphere over the full photometric I-band. This prototype will include an adaptive optics specified to reach at λ ≈ 800 nm a Strehl ratio > 0.8 for magnitude m < 7.In the third section, we show the theoretical performance of EvWaCo: a contrast comprised between a few 10-6 and 10-7 in the I-Band between 3 λ/D and 10 λ/D in the I-Band for an IWA equal to 3 λ/D with a Gaussian apodization in unpolarized light. We also show that similar contrasts performance are obtained in the V-, R-, bands, thus illustrating the EvWaCo quasi-achromaticity. Finally, we discuss the advantages and the limitation using the proposed concept for space-based observations and spectral characterization of exoplanets.

Published
2018
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3. Science cases for a visible interferometer

Author

Philippe Stee, France Allard, Myriam Benisty, Lionel Bigot, Nicolas Blind, Henri Boffin, Marcelo Borges Fernandes, Alex Carciofi, Andrea Chiavassa, Orlagh Creevey, Pierre Cruzalèbes, Willem-Jan de Wit, Armando Domiciano de Souza, Martin Elvis, Nicolas Fabas, Daniel Faes, Alexandre Gallenne, Carlos Guerrero Pena, Michel Hillen, Sebastian Hoenig, Michael Ireland, Pierre Kervella, Makoto Kishimoto, Nadia Kostogryz, Stefan Kraus, Antoine Labeyrie, Jean-Baptiste Le Bouquin, Agnès Lèbre, Roxanne Ligi, Alessandro Marconi, Thomas Marsh, Anthony Meilland, Florentin Millour, John Monnier, Denis Mourard, Nicolas Nardetto, Keiichi Ohnaka, Claudia Paladini, Karine Perraut, Guy Perrin, Pascal Petit, Romain Petrov, Suvendu Rakshit, Gail Schaefer, Jean Schneider, Denis Shulyak, Michal Simon, Ferréol Soulez, Danny Steeghs, Isabelle Tallon-Bosc, Michel Tallon, Theo Ten Brummelaar, Éric Thiébaut, Frédéric Thévenin, Hans van Winckel, Markus Wittkowski, Juan Zorec, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Astrophysique Stellaire, Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max-Planck-Institut für Radioastronomie (MPIFR), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Institut für Astronomie, Universität Wien (IFA), Universität Wien, Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre d'Economie de l'Université Paris Nord (ancienne affiliation) (CEPN), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Biotechnologie et Chimie Marines (LBCM), Université de Brest (UBO)-Université de Bretagne Sud (UBS)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Observatoire de la Côte d'Azur, Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]
Abstract

White Paper prospective. This book is dedicated to the memory of our colleague Olivier Chesneau who passed away at the age of 41. v2 includes some corrections to text; High spatial resolution is the key for the understanding various astrophysical phenomena. But even with the future E-ELT, single dish instruments are limited to a spatial resolution of about 4 mas in the visible. For the closest objects within our Galaxy most of the stellar photosphere remains smaller than 1 mas. With the success of long baseline interferometry these limitations were soom overcome. Today low and high resolution interferometric instruments on the VLTI and CHARA offer an immense range of astrophysical studies. Combining more telescopes and moving to visible wavelengths broadens the science cases even more. With the idea of developing strong science cases for a future visible interferometer, we organized a science group around the following topics: pre-main sequence and main sequence stars, fundamental parameters, asteroseismology and classical pulsating stars, evolved stars, massive stars, active galactic nuclei (AGNs) and imaging techniques. A meeting was organized on the 15th and 16th of January, 2015 in Nice with the support of the Action Specific in Haute Resolution Angulaire (ASHRA), the Programme National en Physique Stellaire (PNPS), the Lagrange Laboratory and the Observatoire de la Cote d'Azur, in order to present these cases and to discuss them further for future visible interferometers. This White Paper presents the outcome of the exchanges. This book is dedicated to the memory of our colleague Olivier Chesneau who passed away at the age of 41.

Published
2017

4. Effective a posteriori co-phasing of interferometric fringe data

Author

Michel Tallon, Antony Schutz, Gilles Duvert, Ferréol Soulez, Isabelle Tallon-Bosc, Eric Thiébaut, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Biomedical Imaging Group [Lausanne], Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), and École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL)

Subjects
[PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 010504 meteorology & atmospheric sciences, Computer science, dispersed fringes, Phase (waves), 01 natural sciences, Optical path, Optics, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, 0103 physical sciences, Sensitivity (control systems), optical interferometry, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, phase delay tracking, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, cophasing, Phaser, Interferometry, Cophasing, A priori and a posteriori, data processing 1 METHOD, business, Algorithm, data processing
Abstract

International audience; We have recently shown that a posteriori co-phasing of multi-spectral interferograms was possible. 1 In this contribution, we extend our approach so that it can be applied to actual data as provided by Amber 2 or Matisse instruments. The main advantage of the proposed post-processing technique is that it requires no modifications of the instruments and yields interferometric observables with higher SNR and much fewer unknowns (in particular for the Fourier phase) than conventional measurements. In order to perform the co-phasing of a complete sequence of interferograms, we jointly estimate a global phase template and the frame dependent optical path errors due to the turbulence. We show that this strategy is effective for very low SNR data. We assess the effectiveness of our method on simulated and actual AMBER data. We also compare the lowest SNR that can be achieved to the theoretical bounds and estimate the gain in sensitivity compared to usual interferometric data. To overcome turbulence effects and yet reach a reasonable signal to noise ratio (SNR), interferometric observables require to integrate information over many short exposure frames computed from the so-called coherent fluxes. 3, 4 Our objective is to compensate for the variable phase changes during a given sequence so that it is possible to perform a direct integration of the coherent fluxes over many short exposures, before the computation of the long exposure chromatic complex visibilities. 1.1 Maximum Likelihood Criterion Let c ,m ∈ C be the coherent flux measured in-th spectral channel and m-th frame; it is related to the complex visibility c obj ∈ C of the observed object at the wavelength λ of the spectral channel by: 3, 4 c ,m = c atm ,m c inst c obj + n ,m , (1) where c inst ∈ C is a static instrumental complex visibility, c atm ,m ∈ C is a variable complex factor mainly due to atmospheric effects and n ,m accounts for the noise. Our objective is to provide an estimator closely related to c stat def = c inst c obj , the static part of the coherent flux. Getting rid of the c inst factor is a matter of calibrating this term either by means of internal calibration sources or by observing a calibrator whose complex visibility is known. Since we are interested in compensating for variable phase shifts, we rewrite the direct model in Eq. (1) as: c ,m = ρ ,m e i (ϕ +ψ ,m) + n ,m , (2)

Published
2016
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5. Modeling chromatic instrumental effects for a better model fitting of optical interferometric data

Author

Olivier Chesneau, Michel Tallon, Isabelle Tallon-Bosc, and L. Dessart

Subjects
Physics, Data processing, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Vega, Measure (mathematics), Interferometry, Optics, Astronomical interferometer, Radiative transfer, Calibration, Chromatic scale, business, Algorithm
Abstract

Current interferometers often collect data simultaneously in many spectral channels by using dispersed fringes. Such polychromatic data provide powerful insights in various physical properties, where the observed objects show particular spectral features. Furthermore, one can measure spectral differential visibilities that do not directly depend on any calibration by a reference star. But such observations may be sensitive to instrumental artifacts that must be taken into account in order to fully exploit the polychromatic information of interferometric data. As a specimen, we consider here an observation of P Cygni with the VEGA visible combiner on CHARA interferometer. Indeed, although P Cygni is particularly well modeled by the radiative transfer code CMFGEN, we observe questionable discrepancies between expected and actual interferometric data. The problem is to determine their origin and disentangle possible instrumental effects from the astrophysical information. By using an expanded model fitting, which includes several instrumental features, we show that the differential visibilities are well explained by instrumental effects that could be otherwise attributed to the object. Although this approach leads to more reliable results, it assumes a fit specific to a particular instrument, and makes it more difficult to develop a generic model fitting independent of any instrument.

Published
2014
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6. Long baseline interferometry in the visible: the FRIEND project

Author

C. Bailet, Philippe Feautrier, Alain Spang, Olivier Chesneau, P. Balard, Philippe Berio, Stephane Lagarde, J. Dejonghe, Karine Perraut, Anthony Meilland, Nicolas Nardetto, Ph. Stee, Isabelle Tallon-Bosc, A. Marcotto, A. Duthu, Yves Bresson, Jean-Michel Clausse, Denis Mourard, Jean-Luc Gach, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Optical fiber, Spatial filter, business.industry, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, Single-mode optical fiber, Spectral bands, 01 natural sciences, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], law.invention, 010309 optics, Interferometry, Optics, law, 0103 physical sciences, Astronomical interferometer, Astrophysics::Solar and Stellar Astrophysics, Adaptive optics, business, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Remote sensing
Abstract

In the next 2 or 3 years, the two major interferometric arrays, VLTI and CHARA, will equip their telescopes of 1.8m and 1m respectively with Adaptive Optics (AO hereafter) systems. This improvement will permit to apply with a reasonable e_ciency in the visible domain, the principle of spatial filtering with single mode fibers demonstrated in the near-infrared. It will clearly open new astrophysical fields by taking benefit of an improved sensitivity and state-of-the-art precision and accuracy on interferometric observables. To prepare this future possibility, we started the development of a demonstrator called FRIEND (Fibered and spectrally Resolved Interferometric Experiment - New Design). FRIEND combines the beams coming from 3 telescopes after injection in single mode optical fibers and provides some spectral capabilities for characterization purposes as well as photometric channels. It operates in the R spectral band (from 600nm to 750nm) and uses the world's fastest and more sensitive analogic detector OCAM2. Tests on sky at the focus of the CHARA interferometer are scheduled for December 2014. In this paper, we present the first interferometric tests of the OCAM2 detector performed on CHARA in November 2012 and the concept, the expected performance and the opto-mechanical design of FRIEND.

Published
2014
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7. AMBER: a near infrared focal instrument for the VLTI

Author

Michael Geng, Martin Vannier, G. Martinot-Lagarde, M. Dugué, Yves Rabbia, S. Rebattu, Djamel Mékarnia, T. Forveille, Bruno Lopez, Karl-Heinz Hofmann, Stephane Lagarde, Carlo Baffa, Gilles Duvert, Pascal Puget, Karine Rousselet-Perraut, Fabien Malbet, Albrecht Dreiss, Udo Beckmann, Andrea Richichi, Eric Aristidi, Romain Petrov, Frédéric Cassaing, Danielle LeContel, Markus Schoeller, Yves Bresson, S. Robbe-Dubois, A. Glentzlin, Alessandro Marconi, D. Kamm, Philippe Berio, Sandro Gennari, David Mouillet, François Reynaud, P. Antonelli, K. Agabi, Isabelle Tallon-Bosc, Piero Salinari, Jean-Louis Monin, Franco Lisi, G. Mars, Alain Chelli, Etienne LeCoarer, M. Sacchettini, Gerd Weigelt, Denis Mourard, Laboratoire Universitaire d'Astrophysique de Nice (LUAN), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Max-Planck-Institut für Radioastronomie (MPIFR), Département Fresnel (FRESNEL), Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), Division technique INSU/SDU (DTI), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche en Communications Optiques et Microondes (IRCOM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory (ESO), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Active galactic nucleus, Young stellar object, FOS: Physical sciences, General Physics and Astronomy, Astrophysics, 01 natural sciences, 7. Clean energy, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 010309 optics, Optics, [CHIM.ANAL]Chemical Sciences/Analytical chemistry, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, optical interferometry, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, instrumentation, Physics, Very Large Telescope, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Spatial filter, business.industry, Astrophysics (astro-ph), Near-infrared spectroscopy, Astrophysics::Instrumentation and Methods for Astrophysics, Single-mode optical fiber, Astronomy, [CHIM.MATE]Chemical Sciences/Material chemistry, Exoplanet, astronomy, very large telescope, Interferometry, Astrophysics::Earth and Planetary Astrophysics, business, high angular resolution
Abstract

AMBER is the General User near-infrared focal instrument of the Very Large Telescope interferometer. Its specifications are based on three key programs on Young Stellar Objects, Active Galactic Nuclei central regions, masses and spectra of hot Extra Solar Planets. It has an imaging capacity because it combines up to three beams and very high accuracy measurement are expected from the spatial filtering of beams by single mode fibers and the comparison of measurements made simultaneously in different spectral channels., 10 pages

Published
2001
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8. A posteriori fringes sensing

Author

Ferréol Soulez, Éric Thiébaut, Michel Tallon, Isabelle Tallon-Bosc, AiRi, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Soulez, Ferréol

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [INFO.INFO-TS] Computer Science [cs]/Signal and Image Processing, [PHYS.ASTR.IM] Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, ComputingMilieux_MISCELLANEOUS, [SPI.SIGNAL] Engineering Sciences [physics]/Signal and Image processing, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience

Published
2013

9. A high angular and spectral resolution view into the hidden companion of epsilon Aurigae

Author

Nicolas Nardetto, Chris Farrington, Neal J. Turner, Robert E. Stencel, K. Perraut, S. T. Ridgway, Harold A. McAlister, Petr Harmanec, J. Sturmann, Ph. Stee, Olivier Chesneau, P. J. Goldfinger, T. ten Brummelaar, Isabelle Tallon-Bosc, Roxanne Ligi, Jean-Michel Clausse, Ph. Berio, Denis Mourard, L. Sturmann, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Line-of-sight, 010308 nuclear & particles physics, Plane (geometry), Vega, Astronomy, Astronomy and Astrophysics, Scale height, Astrophysics, 01 natural sciences, CHARA array, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Spectral resolution, Visibility, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Eclipse
Abstract

The enigmatic binary, e Aur, is yielding its parameters as a result of new methods applied to the recent eclipse, including optical spectro-interferometry with the VEGA beam combiner at the CHARA Array. VEGA/CHARA visibility measurements from 2009 to 2011 indicate the formation of emission wings of Hα in an expanding zone almost twice the photospheric size of the F star, namely, in a stellar wind. These may be caused by shocks in the atmosphere from large scale convective or multi-periodic pulsation modes emerging from the star. During the total eclipse phase in 2010, when the disk was in the line of sight, we saw broadening of the Hα absorption and a less steep drop of the visibility curve, consistent with the addition of neutral hydrogen in the line of sight but extended above and below the plane of the interferometrically imaged disk itself. This provides a unique constraint on the scale height of the gaseous component of the disk material, and, based on some additional assumptions, points to a mass of the central object being 2.4

Published
2012
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10. The diameter of the CoRoT target HD 49933. Combining the 3D limb darkening, asteroseismology, and interferometry

Author

B. Pichon, Chris Farrington, Pierre Morel, François-Xavier Schmider, Judit Sturmann, Laszlo Sturmann, Ph. Stee, P. Berio, R. Ligi, Harold A. McAlister, Isabelle Tallon-Bosc, Nils H. Turner, Denis Mourard, Tabetha S. Boyajian, Frédéric Thévenin, S. T. Ridgway, Karine Perraut, Pierre Kervella, Lionel Bigot, P. J. Goldfinger, T. ten Brummelaar, O. Delaa, Olivier Chesneau, Nicolas Nardetto, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), and Laboratoire Hippolyte Fizeau (FIZEAU)

Subjects
Hertzsprung–Russell diagram, FOS: Physical sciences, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asteroseismology, symbols.namesake, Angular diameter, 0103 physical sciences, Astronomical interferometer, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Stellar evolution, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, Radius, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Limb darkening, symbols, Astrophysics::Earth and Planetary Astrophysics
Abstract

Context. The interpretation of stellar pulsations in terms of internal structure depends on the knowledge of the fundamental stellar parameters. Long-base interferometers permit us to determine very accurate stellar radii, which are independent constraints for stellar models that help us to locate the star in the HR diagram. Aims: Using a direct interferometric determination of the angular diameter and advanced three-dimensional (3D) modeling, we derive the radius of the CoRoT target HD 49933 and reduce the global stellar parameter space compatible with seismic data. Methods: The VEGA/CHARA spectro-interferometer is used to measure the angular diameter of the star. A 3D radiative hydrodynamical simulation of the surface is performed to compute the limb darkening and derive a reliable diameter from visibility curves. The other fundamental stellar parameters (mass, age, and Teff) are found by fitting the large and small p-mode frequency separations using a stellar evolution model that includes microscopic diffusion. Results: We obtain a limb-darkened angular diameter of {\theta}LD = 0.445 \pm 0.012 mas. With the Hipparcos parallax, we obtain a radius of R = 1.42 \pm 0.04 Rsun. The corresponding stellar evolution model that fits both large and small frequency separations has a mass of 1.20 \pm 0.08 Msun and an age of 2.7 Gy. The atmospheric parameters are Teff = 6640 \pm 100 K, log g = 4.21 \pm 0.14, and [Fe/H] = -0.38., Comment: 4 pages, 4 figures

Published
2011
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11. Performances and first science results with the VEGA/CHARA visible instrument

Author

Michel Tallon, Ph. Berio, H. A. McAlister, Denis Mourard, Jean-Michel Clausse, L. Sturmann, Neal J. Turner, Nicolas Nardetto, Karine Perraut, P. J. Goldfinger, T. ten Brummelaar, Alain Spang, Olivier Chesneau, Chris Farrington, D. Bonneau, O. Delaa, Isabelle Tallon-Bosc, J. Sturmann, Ph. Stee, Laboratoire Gemini (LG), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Joseph Louis LAGRANGE (LAGRANGE), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Georgia State University, University System of Georgia (USG), Center for High Angular Resolution Astronomy (CHARA), and University System of Georgia (USG)-University System of Georgia (USG)

Subjects
Chara, Physics, biology, Vega, Astronomy, Polarimeter, biology.organism_classification, CHARA array, law.invention, Telescope, Stars, Deneb, law, [SDU]Sciences of the Universe [physics], Spectrograph
Abstract

International audience; This paper presents the current status of the VEGA (Visible spEctroGraph and polArimeter) instrument installed at the coherent focus of the CHARA Array, Mount Wilson CA. Installed in september 2007, the first science programs have started during summer 2008 and first science results are now published. Dedicated to high angular (0.3mas) and high spectral (R=30000) astrophysical studies, VEGA main objectives are the study of circumstellar environments of hot active stars or interactive binary systems and a large palette of new programs dedicated to fundamental stellar parameters. We will present successively the main characteristics of the instrument and its current performances in the CHARA environment, a short summary of two science programs and finally we will develop some studies showing the potential and difficulties of the 3 telescopes mode of VEGA/CHARA.

Published
2010
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12. Study of the atmospheric refraction in a single mode instrument - Application to AMBER/VLTI

Author

Stephane Lagarde, Isabelle Tallon-Bosc, Romain Petrov, Sylvie Robbe-Dubois, P. Antonelli, Martin Vannier, F. Rantakyrö, G. Martinot-Lagarde, Daniel Tasso, Alain Roussel, Yves Bresson, Etienne Le-Coarer, Marcel Carbillet, Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Gemini Observatory [Southern Operations Center], Association of Universities for Research in Astronomy (AURA), European Southern Laboratory, European Southern Observatory (ESO), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Division technique INSU/SDU (DTI), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), and Joseph Louis LAGRANGE (LAGRANGE)

Subjects
[PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], FOS: Physical sciences, Physics::Optics, 01 natural sciences, law.invention, 010309 optics, Telescope, Optics, law, 0103 physical sciences, Atmospheric refraction, Astrophysics::Solar and Stellar Astrophysics, Adaptive optics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Zenith, ComputingMilieux_MISCELLANEOUS, Physics, Very Large Telescope, business.industry, Single-mode optical fiber, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Refraction, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Interferometry, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, business, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

This paper presents a study of the atmospheric refraction and its effect on the light coupling efficiency in an instrument using single-mode optical fibers. We show the analytical approach which allowed us to assess the need to correct the refraction in J- and H-bands while observing with an 8-m Unit Telescope. We then developed numerical simulations to go further in calculations. The hypotheses on the instrumental characteristics are those of AMBER (Astronomical Multi BEam combineR), the near infrared focal beam combiner of the Very Large Telescope Interferometric mode (VLTI), but most of the conclusions can be generalized to other single-mode instruments. We used the software package caos (Code for Adaptive Optics Systems) to take into account the atmospheric turbulence effect after correction by the ESO system MACAO (Multi-Application Curvature Adaptive Optics). The opto-mechanical study and design of the system correcting the atmospheric refraction on AMBER is then detailed. We showed that the atmospheric refraction becomes predominant over the atmospheric turbulence for some zenith angles z and spectral conditions: for z larger than 30{\circ} in J-band for example. The study of the optical system showed that it allows to achieve the required instrumental performance in terms of throughput in J- and H-bands. First observations in J-band of a bright star, alpha Cir star, at more than 30{\circ} from zenith clearly showed the gain to control the atmospheric refraction in a single mode instrument, and validated the operating law., Mon. Not. R. Astron. Soc. (2009) accepted

Published
2009
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13. VEGA: a new visible spectrograph and polarimeter on the CHARA Array

Author

Neal J. Turner, A. Blazit, A. Domiciano de Souza, Denis Mourard, Éric Thiébaut, Isabelle Tallon-Bosc, L. Sturmann, Michel Tallon, Harold A. McAlister, Karine Perraut, Chris Farrington, A. Roussel, A. Marcotto, J. Sturmann, P. J. Goldfinger, T. ten Brummelaar, Ph. Stee, François Hénault, G. Merlin, Olivier Chesneau, Pierre Kervella, R. Foy, Jean-Michel Clausse, Y. Hughes, D. Bonneau, and D. Mattei

Subjects
Physics, Chara, biology, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Vega, Polarimeter, biology.organism_classification, CHARA array, Optics, Astrophysics::Solar and Stellar Astrophysics, Computer Science::Symbolic Computation, Astrophysics::Earth and Planetary Astrophysics, Spectral resolution, business, Spectroscopy, Spectrograph, Visible spectrum
Abstract

The VEGA spectrograph and polarimeter has been recently integrated on the visible beams of the CHARA Array. With a spectral resolution up to 35000 and thanks to operation at visible wavelengths, VEGA brings unique capabilities in terms of spatial and spectral resolution to the CHARA Array. We will present the main characteristics of VEGA on CHARA, some results concerning the performance and a preliminary analysis of the first science run.

Published
2008
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14. Shack-Hartmann wavefront reconstruction with elongated sodium laser guide stars: improvements with priors and noise correlations

Author

Éric Thiébaut, Isabelle Tallon-Bosc, Clémentine Béchet, and Michel Tallon

Subjects
Wavefront, Physics, business.industry, Sodium layer, Wavefront sensor, Least squares, Noise (electronics), law.invention, Telescope, Optics, Position (vector), law, business, Adaptive optics
Abstract

The current projects of Extremely Large Telescopes rely on adaptive optics systems using several sodium laser guide stars (LGSs). Because of the thickness of the sodium layer in the mesosphere, the subapertures of a Shack-Hartmann wavefront sensor will see the LGS all the more elongated as its position is distant from the launching point of the laser. This effect is significant and prompts the lasers to be launched from behind the secondary instead of from around the telescope. The elongations increase the centroiding errors and new smarter algorithms have been designed to mitigate this effect, but the loss of accuracy is still significant. Further, the measurement uncertainties are no more uniform across the pupil and correlations are introduced between the two coordinates of the gradients. From numerical simulations, we analyze the benefit of taking into account this structured correlations in wavefront reconstruction algorithms and compare the reconstruction accuracy when using least squares, weighted least squares, or minimum variance using von Karman turbulence priors. For a single LGS launched behind the secondary, numerical simulations show effective improvements when using both noise correlations and priors in wavefront reconstruction. When combining the measurements from several LGSs in a Ground Layer adaptive optics system, we show that taking into account the noise covariances yields better reconstructions when LGSs are launched from around the telescope than from behind the secondary. Further, results indicate that we could discard the measurements along the elongated direction where this elongation is greater than a given threshold.

Published
2008
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15. LITpro: a model fitting software for optical interferometry

Author

Denis Mourard, Michel Tallon, Olivier Chesneau, Éric Thiébaut, Martin Vannier, Romain Petrov, A. Domiciano de Souza, C. Béchet, S. Lafrasse, Gilles Duvert, Isabelle Tallon-Bosc, Guillaume Mella, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Markus Schöller, William C. Danchi, Françoise Delplancke, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
fitting software, [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Computer science, 01 natural sciences, 010309 optics, Set (abstract data type), symbols.namesake, Optics, Software, 0103 physical sciences, optical interferometry, 010303 astronomy & astrophysics, Global optimization, Trust region, business.industry, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Wavelength, Interferometry, Fourier transform, symbols, Partial derivative, Object model, Spectral energy distribution, Mira stars, business, Algorithm, data processing, Free parameter
Abstract

9 pages; International audience; LITpro is a software for fitting models on data obtained from various stellar optical interferometers, like the VLTI. As a baseline, for modeling the object, it provides a set of elementary geometrical and center-to-limb darkening functions, all combinable together. But it is also designed to make very easy the implementation of more specific models with their own parameters, to be able to use models closer to astrophysical considerations. So LITpro only requires the modeling functions to compute the Fourier transform of the object at given spatial frequencies, and wavelengths and time if needed. From this, LITpro computes all the necessary quantities as needed (e.g. visibilities, spectral energy distribution, partial derivatives of the model, map of the object model). The fitting engine, especially designed for this kind of optimization, is based on a modified Levenberg-Marquardt algorithm and has been successfully tested on real data in a prototype version. It includes a Trust Region Method, minimizing a heterogeneous non-linear and non-convex criterion and allows the user to set boundaries on free parameters. From a robust local minimization algorithm and a starting points strategy, a global optimization solution is effectively achieved. Tools have been developped to help users to find the global minimum. LITpro is also designed for performing fitting on heterogeneous data. It will be shown, on an example, how it fits simultaneously interferometric data and spectral energy distribution, with some benefits on the reliability of the solution and a better estimation of errors and correlations on the parameters. That is indeed necessary since present interferometric data are generally multi-wavelengths.

Published
2008
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16. AMBER, the near-infrared spectro-interferometric three-telescope VLTI instrument

Author

Franco Lisi, Denis Mourard, K. Agabi, A. Glentzlin, P. Stefanini, Piero Salinari, G. Martinot-Lagarde, J. M. Clausse, Markus Schöller, Philippe Mathias, O. Hernandez Utrera, E. Nussbaum, J.-C. Valtier, A. Spang, Carlo Baffa, Fabien Malbet, Udo Beckmann, Michel Tallon, Alain Chelli, Sandro Gennari, O. von der Lühe, Pierre Mege, M. Accardo, Karl-Heinz Hofmann, C. Perrier, Mario Kiekebusch, Keiichi Ohnaka, M. Heiden, Ph. Stee, S. Robbe-Dubois, C. Connot, Frédéric Cassaing, T. Lesourd, D. Ferruzzi, Dieter Schertl, M. Sacchettini, L. Gluck, P. Kern, Gerd Weigelt, Alessandro Marconi, D. Mouillet, F. Vakili, S. Busoni, Renaud Foy, J. M. Le Contel, Florentin Millour, A. Robini, J. Behrend, D. Tasso, Leonardo Testi, D. Kamm, Isabelle Tallon-Bosc, Didier Fraix-Burnet, Y. Bresson, P. Antonelli, François Reynaud, T. Forveille, Yves Magnard, Bruno Lopez, C. Gil, Andrea Richichi, E. Le Coarer, E. Tatulli, J. Colin, Martin Vannier, S. Lagarde, G. Mars, Gilles Duvert, A. Domiciano de Souza, A. Gallardo, T. Blöcker, José Pacheco, Thomas Driebe, E. Altariba, A. Roussel, Stefan Kraus, Romain Petrov, Eric Aristidi, Elisabetta Giani, Morgan Lopez, K. Perraut, Philippe Feautrier, M. Heininger, D. Le Contel, N. Ventura, Yves Rabbia, S. Rebattu, J. L. Monin, Gérard Zins, Bram Acke, Fredrik T. Rantakyrö, A. Delboulbe, M. Dugué, W. Solscheid, Pascal Puget, Brahim Arezki, S. Bonhomme, E. Fossat, Laboratoire Universitaire d'Astrophysique de Nice (LUAN), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Laboratoire Gemini (LG), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Département Fresnel (FRESNEL), Observatoire de la Côte d'Azur, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), European Southern Observatory (ESO), Laboratoire Universitaire d'Astrophysique de Nice, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA), ONERA - The French Aerospace Lab [Châtillon], ONERA, Observatoire de la Côte d'Azur (OCA), Centre National de la Recherche Scientifique (CNRS), Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Association EURATOM-CEA (CEA/DSM/DRFC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Division technique INSU/SDU (DTI), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, PHOTONIQUE, XLIM (XLIM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), ONERA-Université Paris Saclay (COmUE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
[SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], techniques, Context (language use), Astrophysics, 01 natural sciences, law.invention, 010309 optics, Telescope, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Optics, Palomar Testbed Interferometer, law, Observatory, instrumentation: high angular resolution, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Scientific instrument, Physics, Very Large Telescope, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Interferometry, Space and Planetary Science, interferometric, Closure phase, business, techniques: spectroscopic
Abstract

Context: Optical long-baseline interferometry is moving a crucial step forward with the advent of general-user scientific instruments that equip large aperture and hectometric baseline facilities, such as the Very Large Telescope Interferometer (VLTI). Aims: AMBER is one of the VLTI instruments that combines up to three beams with low, moderate and high spectral resolutions in order to provide milli-arcsecond spatial resolution for compact astrophysical sources in the near-infrared wavelength domain. Its main specifications are based on three key programs on young stellar objects, active galactic nuclei central regions, masses, and spectra of hot extra-solar planets. Methods: These key science goals led to scientific specifications, which were used to propose and then validate the instrument concept. AMBER uses single-mode fibers to filter the entrance signal and to reach highly accurate, multiaxial three-beam combination, yielding three baselines and a closure phase, three spectral dispersive elements, and specific self-calibration procedures. Results: The AMBER measurements yield spectrally dispersed calibrated visibilities, color-differential complex visibilities, and a closure phase allows astronomers to contemplate rudimentary imaging and highly accurate visibility and phase differential measurements. AMBER was installed in 2004 at the Paranal Observatory. We describe here the present implementation of the instrument in the configuration with which the astronomical community can access it. Conclusions: .After two years of commissioning tests and preliminary observations, AMBER has produced its first refereed publications, allowing assessment of its scientific potential.

Published
2007
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17. System analysis of the AMBER instrument on VLTI

Author

Romain Petrov, Denis Mourard, Karine Rousselet-Perraut, Thierry Forveille, Frédéric Cassaing, François Reynaud, Pierre Mege, Isabelle Tallon-Bosc, Karl-Heinz Hofmann, Fabien Malbet, and Michel Tallon

Subjects
Physics, Very Large Telescope, business.industry, Near-infrared spectroscopy, Astrophysics::Instrumentation and Methods for Astrophysics, Photometry (optics), Background noise, Interferometry, Optics, Astronomical interferometer, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, business, Spectrograph, Data reduction, Remote sensing
Abstract

We present a summary of the global system analysis that led to the current definition of the AMBER instrument. AMBER is a near infrared multi-beam combiner for the Very Large Telescope Interferometer. This analysis goes through the following issues: atmospheric systematics including atmospheric turbulence and dispersion, analysis of single mode optical fibers, photometry calibration, spectral dispersion, background noise, data reduction and calibration steps.

Published
2003
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18. SPID: a high spectral resolution diffraction-limited camera

Author

Éric Thiébaut, Renaud Foy, Michel Tallon, A. Blazit, Andre Baranne, Isabelle Tallon-Bosc, and Francoise-Claude Foy

Subjects
Physics, Wavefront, Brightness, Laser guide star, Optics, Image quality, business.industry, Bandwidth (signal processing), Speckle imaging, Wavefront sensor, Adaptive optics, business
Abstract

SPID aims at offering a high spectral resolution in both short-exposure (speckle imaging) and long-exposure (adaptive optics with partial compensation) modes. It offers an adjustable spectral resolution (from 60 up to 3000) in the range 400 - 750 nm. For differential observation of astronomical objects, SPID gives images in two spectral bandwidths at the same time. The width and the central wavelength of each bandwidth can be chosen independently. A high image quality is achieved thanks to a new design derived from a Courtes' monochromator. SPID also includes a wavefront sensor for post-compensation processing. A short-exposure mode allows us to achieve diffraction limited images but with a low signal-to-noise ratio. Depending on the object brightness and on the seeing quality, adaptive optics will allow us to improve significantly the signal-to-noise ratio and sometimes to observe a diffraction limited core in long-exposure mode. Depending on the scientific goal, the availability of the two modes will drive the best choice. The current status of SPID is presented together with first results obtained at CFHT in the short-exposure mode.

Published
2000
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19. Spectrally resolved interferometry with the Grand Interferometre a 2 Telescopes: results and prospects

Author

Philippe Stee, Denis Mourard, Farrokh Vakili, Peter R. Lawson, Daniel Bonneau, Isabelle Tallon-Bosc, Fabrice Vallee, and Guy Merlin

Subjects
Physics, Spectrometer, business.industry, Detector, Visibility (geometry), Optical table, Astrophysics::Instrumentation and Methods for Astrophysics, law.invention, Speckle pattern, Interferometry, Optics, law, Calibration, Astronomical interferometer, business, Remote sensing
Abstract

This paper describes the present status of the Grand Interferometre a 2 Telescopes (GI2T). We review the general features of this instrument and present the scientific programs pursued by our group. Attention is given here to procedures of instrumental and visibility calibration, including the response of both the detector and spectrometer. We discuss the method of data analysis and the attainable accuracy of astrophysical parameters. The current limitations of the GI2T and development of our new optical table are presented.

Published
1994
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20. Progress on GI2T

Author

Ph. Stee, Isabelle Tallon-Bosc, Antoine Labeyrie, Frédéric Morand, Denis Mourard, Farrokh Vakili, and D. Bonneau

Subjects
Physics, Cooley–Tukey FFT algorithm, Optics, Luminous blue variable, business.industry, Michelson stellar interferometer, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Speckle imaging, business, Photon counting detector
Abstract

The purpose of this paper is to describe the operation of GI2T, the visible Michelson stellar interferometer with two 1.5 m apertures, as well as a presentation of its desired evolution.

Published
1994
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21. Spatio-spectral encoding of fringes in optical long-baseline interferometry

Author

Ph. Berio, P. J. Goldfinger, T. ten Brummelaar, A. Blazit, John D. Monnier, Nicolas Nardetto, Isabelle Tallon-Bosc, Olivier Chesneau, Roxanne Ligi, O. Delaa, Denis Mourard, D. Bonneau, Ph. Stee, Alain Spang, J.-B. Le Bouquin, Chris Farrington, Karine Perraut, Florentin Millour, Jean-Michel Clausse, Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Vega, Astronomy and Astrophysics, Polarimeter, 01 natural sciences, CHARA array, 010309 optics, Interferometry, Optics, Space and Planetary Science, 0103 physical sciences, Astronomical interferometer, Closure phase, Astrophysics::Solar and Stellar Astrophysics, Spectral resolution, business, 010303 astronomy & astrophysics, Spectrograph, ComputingMilieux_MISCELLANEOUS, Remote sensing
Abstract

Context. One of the main challenges of optical stellar interferometers is to increase the number of telescopes in the recombining unit to provide a larger number of measurements and an improved imaging capability. At the same time there is a need to preserve the spectroscopic capabilities, which leads to complex recombining schemes that may inhibit development. Aims. We describe the possibilities of combining the spatial and spectral encoding of fringes for the design of more compact beam combiners and for minimizing the number of pixels that must be read. Methods. We establish the formalism of the spatio-spectral fringe encoding, discuss general applications, and describe an implementation in the 3T/4T observing mode of the VEGA (Visible spEctroGraph and polArimeter) instrument installed at the coherent focus of the CHARA Array located on Mt Wilson in California. We finally present the science cases made possible by this instrumental implementation in the case of VEGA/CHARA. Results. We demonstrate the interest in implementing an optimized spatio-spectral encoding of fringes in a multi-telescope beam combiner. On-sky results, obtained with the 3T mode of the VEGA combiner are presented. At visible wavelengths and with the hectometric baselines of CHARA, sub-mas stellar diameters could be determined with a precision of a few percent with a spectral resolution of 5000. Our first estimates of closure phase show that accuracies better than 1 degree can be achieved. Conclusions. The first on-sky results obtained with the 3T-4T VEGA instrument using spatio-spectral fringe encoding show the validity of using this principle in the design of future complex beam combiners.

Published
2011
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22. Dispersed fringe tracking with the multi-ro apertures of the Grand Interféromètre à 2 Télescopes

Author

A. Blazit, Denis Mourard, Peter R. Lawson, Farrokh Vakili, Laurent Koechlin, Isabelle Tallon-Bosc, Frédéric Morand, D. Bonneau, and Ph. Stee

Subjects
Physics, business.industry, Materials Science (miscellaneous), Detector, Astrophysics::Instrumentation and Methods for Astrophysics, Image processing, Tracking (particle physics), Industrial and Manufacturing Engineering, Coherence length, Interferometry, Optics, Optical path, Astrophysics::Solar and Stellar Astrophysics, Spatial frequency, Speckle imaging, Business and International Management, business
Abstract

A new fringe tracker based on photon-counting detectors and real-time image processing has been implemented on the Grand Interferometre a 2 Telescopes at the Observatoire de la Cote d'Azur. Fringe visibilities have been recorded on P Cygni and other stars across the Hαemission line with optical path differences stabilized to between 4 and 7 µm rms (1% of the coherence length). We present our initial results and describe the principle, implementation, and performance of the fringe tracker.

Published
1996
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