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6 results on '"Nassima Tarmoul"'

1. Group and phase delay sensing for cophasing large optical arrays

Author

Jean-Michel Clausse, Nassima Tarmoul, F. Patru, Pascal Girard, Denis Mourard, N. Mauclert, W. Dali Ali, A. Marcotto, François Hénault, Anthony Meilland, 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), HEPPI - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-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 de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-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), 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 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), HELIOS - LATMOS, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-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 Joseph Fourier - Grenoble 1 (UJF)-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)-Centre National d'Études Spatiales [Toulouse] (CNES)-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), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-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 Joseph Fourier - Grenoble 1 (UJF)-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)

Subjects
Physics, instrumentation, business.industry, Interferometers, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, High angular resolution Telescopes, 01 natural sciences, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 010309 optics, Entrance pupil, Cophasing, Interferometry, Delay equalization, Optics, Optical path, Space and Planetary Science, 0103 physical sciences, Astronomical interferometer, business, 010303 astronomy & astrophysics, Coherence (physics), Group delay and phase delay
Abstract

International audience; The next generation of optical interferometers will provide high-resolution imaging of celestial objects by using either the aperture synthesis technique or the direct imaging principle. To determine the technical requirements, we have developed an interferometric test bench, called SIRIUS. To preserve the quality of the image, fast corrections of the optical path differences within a fraction of a wavelength have to be applied: this is the cophasing of the array, whereas making it coherent aims at stabilizing the optical path differences within a fraction of the coherence length. In the SIRIUS test bench, coherence and cophasing are achieved by fibred delay lines. Air delay lines are also used for the raw delay equalization. We present an original implementation of a piston sensor, called chromatic phase diversity, which is adaptable to any interferometer, whatever the configuration of the entrance pupil and the number of sub-pupils and whatever the interferometric combiner. Our method is based on the dispersed fringes principle and uses a derived version of the dispersed speckles method. The numerical simulation shows the performance of the method in terms of cophasing, accuracy and limiting magnitude. Experimental tests have been carried out both with optical turbulence and without. They show good results in both cases, despite some instrument-related limitations that can be eliminated. We show that our method is able to handle an amplitude of correction of ±11(λ/2) with an accuracy of ∼λ/30 over many minutes.

Published
2014
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2. Chromatic phase diversity for cophasing large array of telescopes

Author

Denis Mourard, N. Mauclert, Fabien Patru, A. Marcotto, Wassila Dali-Ali, François Hénault, P. Girard, Jean-Michel Clausse, Anthony Meilland, and Nassima Tarmoul

Subjects
Physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Phase (waves), Spectral density, law.invention, Telescope, Interferometry, Cophasing, Optics, Robustness (computer science), law, Piston (optics), Chromatic scale, business
Abstract

This paper reviews the recent laboratory results we have obtained on the demonstration of a cophasing algorithm based on the chromatic phase diversity method. The SIRIUS testbed was initially dedicated to the demonstration of the direct imaging capabilities of arrays of telescope. We have developed and numerically modeled a piston sensor based on the chromatic dependance of the spectral density phase. This method allows a global cophasing of the array over a capture range of many wavelengths aiming at improving the robustness of the method.

Published
2012
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3. Direct imaging with a hypertelescope of red supergiant stellar surfaces

Author

Nassima Tarmoul, Fabien Patru, Denis Mourard, and Andrea Chiavassa

Subjects
Physics, Betelgeuse, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Field of view, Astrophysics, Galaxy, law.invention, Photometry (optics), Telescope, Cophasing, Optics, Astrophysics - Solar and Stellar Astrophysics, law, Astrophysics::Solar and Stellar Astrophysics, Red supergiant, Astrophysics - Instrumentation and Methods for Astrophysics, business, Image resolution
Abstract

High angular resolution images obtained with a hypertelescope can strongly constrain the radiative-hydrodynamics simulations of red supergiant (RSG) stars, in terms of intensity contrast, granulation size and temporal variations of the convective motions that are visible on their surface. The characterization of the convective pattern in RSGs is crucial to solve the mass-loss mechanism which contributes heavily to the chemical enrichment of the Galaxy. We show here how the astrophysical objectives and the array configuration are highly dependent to design a hypertelescope. For a given field of view and a given resolution, there is a trade-off between the array geometry and the number of required telescopes to optimize either the (u,v) coverage (to recover the intensity distribution) or the dynamic range (to recover the intensity contrast). To obtain direct snapshot images of Betelgeuse with a hypertelescope, a regular and uniform layout of telescopes is the best array configuration to recover the intensity contrast and the distribution of both large and small granulation cells, but it requires a huge number of telescopes (several hundreds or thousands). An annular configuration allows a reasonable number of telescopes (lower than one hundred) to recover the spatial structures but it provides a low-contrast image. Concerning the design of a pupil densifier to combine all the beams, the photometric fluctuations are not critical Delta photometry < 50%) contrary to the residual piston requirements (OPD

Published
2010
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4. Implementation of the chromatic phase diversity method on the SIRIUS test bench

Author

Nassima Tarmoul, Alain Roussel, P. Girard, Yves Rabbia, Denis Mourard, Jean-Michel Clausse, A. Marcotto, Alain Spang, François Hénault, N. Mauclert, 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), 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), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-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), médialab (Sciences Po) (médialab), Sciences Po (Sciences Po), Joseph Louis LAGRANGE (LAGRANGE), Architecture et fonction des macromolécules biologiques (AFMB), and Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Test bench, Computer science, business.industry, Instrumentation, law.invention, Telescope, [SPI]Engineering Sciences [physics], Piston, Cophasing, Interferometry, Optics, [SDU]Sciences of the Universe [physics], law, Astronomical interferometer, Piston (optics), Chromatic scale, business, Algorithm, ComputingMilieux_MISCELLANEOUS
Abstract

As for large interferometers, the crucial point to solve is the cophasing issue. Indeed, the cophasing device must be both efficient and independent of the number of telescopes allowing a large capture range and accurate piston measurements while being easy to implement. We developed such a cophasing method named the Chromatic Phase Diversity (CPD) method. Actually, using three spectral channels, the CPD method can determine the piston errors without ambiguity and on a range much larger than ± half a wave. This method makes it possible to work whether in coherencing mode or in cophasing mode. We designed and implemented this method on the SIRIUS test bench1 at the Observatoire de la Cote d'Azur, France. We present the instrument design, the results obtained with the CPD method. The performances such as the achieved capture range, the accuracy of the piston values extraction and the attainable magnitude are described and analyzed.

Published
2010
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5. The planar optics phase sensor: a study for the VLTI 2nd generation fringe tracker

Author

Franois Hénault, Fabien Malbet, Jean-Philippe Berger, Nicolas Blind, Nassima Tarmoul, Laurent Jocou, Karine Rousselet-Perrault, Jean Surdej, Lionel Vincent, Thomas Laurent, Alain Sarlette, Denis Defrere, J. B. Lebouquin, Philippe Feautrier, E. Tatulli, Olivier Absil, Mazen Alamir, Pierre Kern, and Denis Mourard

Subjects
Very Large Telescope, Spatial filter, Computer science, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Phase (waves), Measure (physics), FOS: Physical sciences, Interferometry, Planar, Optics, Position (vector), Astrophysics - Instrumentation and Methods for Astrophysics, business, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

In a few years, the second generation instruments of the Very Large Telescope Interferometer (VLTI) will routinely provide observations with 4 to 6 telescopes simultaneously. To reach their ultimate performance, they will need a fringe sensor capable to measure in real time the randomly varying optical paths differences. A collaboration between LAOG (PI institute), IAGL, OCA and GIPSA-Lab has proposed the Planar Optics Phase Sensor concept to ESO for the 2nd Generation Fringe Tracker. This concept is based on the integrated optics technologies, enabling the conception of extremely compact interferometric instruments naturally providing single-mode spatial filtering. It allows operations with 4 and 6 telescopes by measuring the fringes position thanks to a spectrally dispersed ABCD method. We present here the main analysis which led to the current concept as well as the expected on-sky performance and the proposed design.

Published
2010
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6. Study of a new cophasing system for hypertelescopes

Author

Denis Mourard, François Hénault, and Nassima Tarmoul

Subjects
Point spread function, Entrance pupil, Interferometry, Speckle pattern, Cophasing, Optics, Computer science, business.industry, Astronomical interferometer, business, Energy (signal processing)
Abstract

As the next generation of giant optical interferometers, hypertelescopes will provide high resolution direct imaging of celestial sources by using the densification principle. 1 In order to determine the technical requirements of such an instrument, an interferometric testbench, called SIRIUS (Patru et al. 2004), has been developed at the Observatoire de la Cote d'Azur, France. The active cophasing of the beams remains the most significant hard point to preserve the quality of the image. It has been shown that this cophasing should be at the level of λ/10 so that more than 90% of the energy remains in the central peak of the point spread function. 2 In the current version of SIRIUS, the raw coherencing is done manually by adjusting air delay lines, whereas the cophasing is ensured by a fibered cophasing system. We present our study of an optimized cophasing system that we intend to develop on the SIRIUS testbench. One of the main goals is to be adaptable to any interferometer, whatever the configuration of the entrance pupil and the number of sub pupils. This new version will improve the cophasing system by using a derived version of the dispersed speckles method 3 for fine cophasing. The observed images will then be stabilized during a longer period, allowing a more efficient analysis of the studied source.

Published
2008
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