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PEOPLE@HES-SO – Annuaire et Répertoire des compétences

PEOPLE@HES-SO
Annuaire et Répertoire des compétences

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Jolissaint Laurent

Jolissaint Laurent

Professeur HES associé

Compétences principales

Optics

Adaptive optics

Astronomical instrumentation

Optical instruments

Optical metrology

Imaging systems

  • Contact

  • Enseignement

  • Recherche

  • Publications

  • Conférences

Contrat principal

Professeur HES associé

Téléphone: +41 24 557 64 21

Bureau: C07

Haute école d'Ingénierie et de Gestion du Canton de Vaud
Route de Cheseaux 1, 1400 Yverdon-les-Bains, CH
HEIG-VD
BSc HES-SO en Microtechniques - Haute école d'Ingénierie et de Gestion du Canton de Vaud
  • optique
  • analyse de données
  • photonique

Terminés

DAG Telescope Focal Plane Instruments Project Management
AGP

Rôle: Requérant(e) principal(e)

Financement: Erzurum Atatürk University

Description du projet : Ce projet consiste en la gestion des projets de construction et d'acquisistion des instruments scientifiques du télescope de 4 m DAG, en Turquie.

Equipe de recherche au sein de la HES-SO: Kjelberg Ivar , Baur Audrey , Jolissaint Laurent , Bretagne Alex , De Figueiredo Joackim

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 02.02.2020 - 30.06.2023

Montant global du projet: 40'000 CHF

Statut: Terminé

Design du générateur de turbulence et du modèle du télescope (calibration source + optics) pour l'optique adaptative du télescope DAG
AGP

Rôle: Requérant(e) principal(e)

Financement: I¿IK University

Description du projet : Design du générateur de turbulence et du modèle du télescope (calibration source + optics) pour l'optique adaptative du télescope DAG

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 01.10.2019 - 31.08.2020

Montant global du projet: 47'700 CHF

Statut: Terminé

Design de l'optique adaptative du télescope DAG
AGP

Rôle: Requérant(e) principal(e)

Financement: I¿IK University

Description du projet : Etude et design du système d'optique adaptative pour le télescope astronomique DAG

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent , De Figueiredo Joackim

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 03.02.2019 - 30.06.2020

Montant global du projet: 50'000 CHF

Statut: Terminé

Etude et consulting sur le développement du laboratoire de test et calibration à Erzurum pour le DAG
AGP

Rôle: Requérant(e) principal(e)

Financement: Atatürk Universitesi

Description du projet : Etude et consulting sur le développement du laboratoire de test et calibration à Erzurum pour le DAG

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 03.02.2019 - 30.06.2020

Montant global du projet: 33'000 CHF

Statut: Terminé

DAG Telescope Focal Plane Instruments Project Management
AGP

Rôle: Requérant(e) principal(e)

Financement: Erzurum Atatürk University

Description du projet : Ce projet consiste en la gestion des projets de construction et d'acquisistion des instruments scientifiques du télescope de 4 m DAG, en Turquie.

Equipe de recherche au sein de la HES-SO: Kjelberg Ivar , Baur Audrey , Jolissaint Laurent , Bretagne Alex , De Figueiredo Joackim

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 01.01.2019 - 31.05.2020

Montant global du projet: 48'200 CHF

Statut: Terminé

Développement du dérotateur de champ pour le télescope national turc DAG, platforme seeing limited
AGP

Rôle: Requérant(e) principal(e)

Financement: ISIK University

Description du projet : Design d'un dispositif opto-mécanique de dérotation du champ de vue pour la compensation de la rotation terrestre, platforme seeing limited du télescope

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent , De Figueiredo Joackim

Partenaires académiques: IAI

Durée du projet: 03.03.2019 - 28.02.2020

Montant global du projet: 51'700 CHF

Statut: Terminé

Point Spread Function Reconstruction for Astronomical Adaptive Optics Systems: Application to the W.M. Keck Telescope
AGP

Rôle: Requérant(e) principal(e)

Financement: W. M. Keck Foundation Observatory

Description du projet : Les systèmes d'optique adaptative consistent en systèmes optiques dynamiques qui corrigent en temps réel les aberrations d'origine multiple et variables dans le temps que l'on peut trouver au sein des systèmes optiques travaillant dans des conditions environnementales complexes (turbulence atmosphériques, liquides, etc.) Connaître la réponse instrumentale d'un système d'optique adaptative (OA) à une source ponctuelle (Point Spread Function, PSF), est indispensable est requise dans plusieurs cas : tout d'abord, pour le diagnostic de la performance du système; ensuite, au niveau de l'extraction du contenu scientifique des données scientifiques brutes acquises en mode OA (réduction des données). Parmi les techniques de réduction les plus usitées, on compte la déconvolution, ainsi que les mesures photométriques et astrométriques. Toutes ces techniques nécessitent une connaissance aussi précise que possible de la PSF du système. En principe, la PSF peut être simplement déterminée par l'observation d'une étoile, objet consideré ponctuel, dans le champ d'observation. Cependant, une telle étoile n'est pas toujours disponible : soit que l'on soit en mode spectroscopie, que le champ angulaire soit encombré d'étoiles lumineuses, ou que la correction OA utilise une étoile-guide non ponctuelle - un noyau actif de galaxie, un satellite naturel, etc... Par ailleurs, une telle observation consomme un précieux temps de télescope (100'000 euro/nuit sur les VLT), et de plus la non simultanéité de l'enregistrement de la PSF et de la mesure OA proprement dite fait que les conditions atmosphériques - de turbulence - ne sont plus tout à fait les mêmes, et que la PSF aura changé, dans des proportions difficiles à évaluer. Pour ces raisons a été développé, ces dernières années, une technique de reconstruction de la PSF se basant sur les mesures de l'analyseur de front d'onde acquises durant l'observation OA: en effet, ces données contiennent, sous une forme ou une autre, une information sur la structure de la PSF instantanée. Jean-Pierre Véran fut le pionnier du développement de cette technique, qu'il a appliquée avec succès au système PUEO (OA sur CFHT), et que j'ai à mon tour appliquée au système ALTAIR, l'OA du télescope GEMINI, lors de mes années de recherche au Centre National de Recherche du Canada. Depuis 2009, j'ai initié en collaboration avec les observatoires astronomiques Gemini et W.M. Keck un programme scientifique de mise au point d'une technique de PSF-R pour ces deux observatoires. Nos travaux ont déjà démontré l'efficacité de notre technique pour les modes OA faisant usage d'étoiles guide naturelles, et notre objectif cobsiste à présent à appliquer ces méthides pour les systèmes utilisant des étoiles guide artificielles (étoile laser). Noius avoins pour cela touché une bourse de recherche de 140'000 $US de la part du National Science Foundation aux Etats-Unis. Cet argent est destiné à couvrir les frais de ces travaux.

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 01.02.2013 - 31.12.2018

Montant global du projet: 127'000 CHF

Statut: Terminé

DAG Telescope Focal Plane Instruments Project Management
AGP

Rôle: Requérant(e) principal(e)

Financement: Erzurum Atatürk University

Description du projet : Ce projet consiste en la gestion des projets de construction et d'acquisistion des instruments scientifiques du télescope de 4 m DAG, en Turquie.

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 16.01.2017 - 31.12.2018

Montant global du projet: 45'000 CHF

Statut: Terminé

Design de l'optique adaptative du télescope DAG
AGP

Rôle: Requérant(e) principal(e)

Financement: ATASAM - Atatürk University - Erzurum; ISIK University

Description du projet : Etude et design du système d'optique adaptative pour le télescope astronomique DAG

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 02.03.2017 - 31.12.2018

Montant global du projet: 63'000 CHF

Statut: Terminé

Développement du dérotateur de champ pour le télescope national turc DAG
AGP

Rôle: Requérant(e) principal(e)

Financement: ATASAM - Atatürk University - Erzurum

Description du projet : Design d'un dispositif opto-mécanique de dérotation du champ de vue pour la compensation de la rotation terrestre.

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent

Partenaires académiques: IAI

Durée du projet: 12.09.2016 - 31.12.2017

Montant global du projet: 30'000 CHF

Statut: Terminé

Point Spread Function Reconstruction for Gemini North Observatory Adaptive Optics System
AGP

Rôle: Requérant(e) principal(e)

Financement: Association Universities Research Astronomy

Description du projet : Les systèmes d'optique adaptative consistent en systèmes optiques dynamiques qui corrigent en temps réel les aberrations d'origine multiple et variables dans le temps que l'on peut trouver au sein des systèmes optiques travaillant dans des conditions environnementales complexes (turbulence atmosphériques, liquides, etc.) Connaître la réponse instrumentale d'un système d'optique adaptative (OA) à une source ponctuelle (Point Spread Function, PSF), est indispensable est requise dans plusieurs cas : tout d'abord, pour le diagnostic de la performance du système; ensuite, au niveau de l'extraction du contenu scientifique des données scientifiques brutes acquises en mode OA (réduction des données). Parmi les techniques de réduction les plus usitées, on compte la déconvolution, ainsi que les mesures photométriques et astrométriques. Toutes ces techniques nécessitent une connaissance aussi précise que possible de la PSF du système. En principe, la PSF peut être simplement déterminée par l'observation d'une étoile, objet consideré ponctuel, dans le champ d'observation. Cependant, une telle étoile n'est pas toujours disponible : soit que l'on soit en mode spectroscopie, que le champ angulaire soit encombré d'étoiles lumineuses, ou que la correction OA utilise une étoile-guide non ponctuelle - un noyau actif de galaxie, un satellite naturel, etc... Par ailleurs, une telle observation consomme un précieux temps de télescope (100'000 euro/nuit sur les VLT), et de plus la non simultanéité de l'enregistrement de la PSF et de la mesure OA proprement dite fait que les conditions atmosphériques - de turbulence - ne sont plus tout à fait les mêmes, et que la PSF aura changé, dans des proportions difficiles à évaluer. Pour ces raisons a été développé, ces dernières années, une technique de reconstruction de la PSF se basant sur les mesures de l'analyseur de front d'onde acquises durant l'observation OA: en effet, ces données contiennent, sous une forme ou une autre, une information sur la structure de la PSF instantanée. Jean-Pierre Véran fut le pionnier du développement de cette technique, qu'il a appliquée avec succès au système PUEO (OA sur CFHT), et que j'ai à mon tour appliquée au système ALTAIR, l'OA du télescope GEMINI, lors de mes années de recherche au Centre National de Recherche du Canada. Depuis 2009, j'ai initié en collaboration avec les observatoires astronomiques Gemini et W.M. Keck un programme scientifique de mise au point d'une technique de PSF-R pour ces deux observatoires. Nos travaux ont déjà démontré l'efficacité de notre technique pour les modes OA faisant usage d'étoiles guide naturelles, et notre objectif cobsiste à présent à appliquer ces méthides pour les systèmes utilisant des étoiles guide artificielles (étoile laser). Nous avons établi un contrat de 32'800$US pour tester implémenter notre technique sur le système OA ALTAIR du télescope GEMINI-NORTH.

Equipe de recherche au sein de la HES-SO: Baur Audrey , Jolissaint Laurent , Mayor Jean-Michel

Partenaires académiques: IAI; Jolissaint Laurent, IAI

Durée du projet: 01.02.2013 - 31.12.2017

Montant global du projet: 33'400 CHF

Statut: Terminé

OPTICAL STUDIES OF DAG TELESCOPE
AGP

Rôle: Collaborateur/trice

Requérant(e)s: IAI, Zago Lorenzo, IAI

Financement: ATASAM - Atatürk University - Erzurum

Description du projet : A preliminary optical design of the DAG telescope. The baseline corisists in defining a convenient Ritchey-Chretien compact configuration for a field of view of 20 arcmin, with a reasonable central obscuration. A primary diameter of 4 m will be assumed. The basic model will be illustrated by a ZEMAX (optical design software) data file.

Equipe de recherche au sein de la HES-SO: Jolissaint Laurent , Zago Lorenzo

Partenaires académiques: IAI; Zago Lorenzo, IAI

Durée du projet: 01.01.2014 - 30.06.2015

Montant global du projet: 17'400 CHF

Statut: Terminé

2022

The european solar telescope
Article scientifique ArODES

C. Quintero Noda, R. Schlichenmaier, L. R. Bellot Rubio, M. G. Löfdahl, E. Khomenko, Audrey Baur, Laurent Jolissaint

Astronomy Astrophysics,  2022, vol. 666, no. A21

Lien vers la publication

Résumé:

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l’Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems.

2019

PRIME :
Article scientifique ArODES
PSF reconstruction and identification for multiple-source characterization enhancement – application to Keck NIRC2 imager

O. Beltramo-Martin, C. M. Correia, S. Ragland, Laurent Jolissaint, B. Neichel, T. Fusco, P. L. Wizinowich

Monthly Notices of the Royal Astronomical Society,  2019, vol. 487, no. 4, pp. 5450–5462

Lien vers la publication

Résumé:

In order to enhance the scientific exploitation of adaptive optics (AO)-assisted observations, we investigate a novel hybrid concept to improve the parametric estimation of point spread function (PSF) called PSF Reconstruction and Identification for Multiple-source characterization Enhancement (PRIME). PRIME uses both focal and pupil-plane measurements to estimate jointly the model parameters related to the atmosphere [C2n(h)⁠, seeing] and the AO system (e.g. optical gains and residual low-order errors). Photometry and astrometry are provided as by-products. The parametric model in use is flexible enough to be scaled with field location and wavelength, making it a proper choice for optimized on-axis and off-axis data-reduction across the spectrum. Here, we present the methodology and validate PRIME on engineering and binary Keck II telescope NIRC2 images. We also present applications of PSF model parameters retrieval using PRIME: (i) calibrate the PSF model for observations void of stars on the acquired images, i.e. optimize the PSF reconstruction process, (ii) update the AO error breakdown mutually constrained by the telemetry and the images in order to speculate on the origin of the missing error terms and evaluate their magnitude, and (iii) measure photometry and astrometry with an application to the triple system Gl569 images.

2018

Determination of the optical turbulence parameters from the adaptive optics telemetry :
Article scientifique ArODES
critical analysis and on-sky validation

Laurent Jolissaint, Sam Ragland, Julian Christou, Peter Wizinowich

Applied Optics,  2018, vol. 57, no. 28, pp. 7837-1856

Lien vers la publication

Résumé:

It has been demonstrated by several authors that the optical turbulence parameters associated with a given adaptive optics (AO) run—the seeing angle and outer scale—can be determined from a statistical analysis of the commands of the system’s deformable mirror (DM). The higher the accuracy on these parameters, the more we can make use of them, allowing for instance a better estimation of the seeing statistics at the telescope location or a more accurate assessment of the performance of the AO system. In the context of a point spread function reconstruction project (PSF-R) for the W. M. Keck observatory AO system, we decided to identify, in the most exhaustive way, all the sources of systematic and random errors affecting the determination of the seeing angle and outer scale from the DM telemetry, and find ways to compensate/mitigate these errors to keep them under 10%. The seeing estimated using our improved DM-seeing method was compared with more than 70 nearly simultaneous seeing measurements from open-loop PSFs on the same optical axis, and with independent seeing-monitor measurements acquired at the same time but far from the telescope (DIMM/MASS): the correlation with the open-loop PSF is very good (the error is about 10%), validating the DM-seeing method for accurate seeing determination, while it is weak and sometimes completely uncorrelated with the DIMM/MASS seeing monitor data. We concluded that DM-based seeing can be very accurate if all the error terms are considered in the DM data processing, but that seeing taken from non-collocated seeing monitors is of no use even when moderate accuracy is required.

2015

Solar ground-layer adaptive optics
Article scientifique ArODES

Deqing Ren, Laurent Jolissaint, Xi Zhang, Jianpei Dou, Rui Chen

Publications of the Astronomical Society of the Pacific,  2015, vol. 127, no. 951, pp. 469–478

Lien vers la publication

Résumé:

Solar conventional adaptive optics (CAO) with one deformable-mirror uses a small field-of-view (FOV) for wave-front sensing, which yields a small corrected FOV for high-resolution imaging. Solar activities occur in a two-dimensional extended FOV and studies of solar magnetic fields need high-resolution imaging over a FOV at least 60''. Recently, solar Tomography Adaptive Optics (TAO) and Multi-Conjugate Adaptive Optics (MCAO) were being developed to overcome this problem of small AO corrected FOV. However, for both TAO and MCAO, wavefront distortions need to be tomographically reconstructed from measurements on multiple guide stars, which is a complicated and time-consuming process. Solar Ground-Layer Adaptive Optics (S-GLAO) uses one or several guide stars, and does not rely on a tomographic reconstruction of the atmospheric turbulence. In this publication, we present two unique wavefront sensing approaches for the S-GLAO. We show that our S-GLAO can deliver good to excellent performance at variable seeing conditions in the Near Infrared (NIR) J and H bands, and is much simpler to implement. We discuss details of our S-GLAO associated wavefront approaches, which make our S-GLAO a unique solution for sunspot high-resolution imaging that other current adaptive optics systems, including the solar MCAO, cannot offer.

2010

Synthetic modeling of astronomical closed loop adaptive optics
Article scientifique ArODES

Laurent Jolissaint

Journal of the European Optical Society: Rapid Publications,  2010, vol. 5, 10055

Lien vers la publication

Résumé:

We present an analytical model of a single natural guide star astronomical adaptive optics system, in closed loop mode. The model is used to simulate the long exposure system point spread function, using the spatial frequency (or Fourier) approach, and complement an initial open loop model. Applications range from system design, science case analysis and AO data reduction. All the classical phase errors have been included: deformable mirror fitting error, wavefront sensor spatial aliasing, wavefront sensor noise, and the correlated anisoplanatic and servo-lag error. The model includes the deformable mirror spatial transfer function, and the actuator array geometry can be different from the wavefront sensor lenslet array geometry. We also include the dispersion between the sensing and the correction wavelengths. Illustrative examples are given at the end of the paper.

2009

Overcoming the boundary layer turbulence at Dome C :
Article scientifique ArODES
ground-layer adaptive optics versus tower

T. Travouillon, Laurent Jolissaint, M. C. B. Ashley, J. S. Lawrence, J. W. V. Storey

Publications of the Astronomical Society of the Pacific,  2009, vol. 121, no. 880, pp. 668-679

Lien vers la publication

Résumé:

The unique atmospheric conditions present at sites such as Dome C on the Antarctic plateau are very favorable for high spatial resolution astronomy. At Dome C, the majority of the optical turbulence is confined to a 30 to 40 m thick stable boundary layer that results from the strong temperature inversion created by the heat exchange between the air and the ice-covered ground. To fully realize the potential of the exceptionally calm free atmosphere, this boundary layer must be overcome. In this article we compare the performance of two methods proposed to beat the boundary layer: mounting a telescope on a tower that physically puts it above the turbulent layer, and installing a telescope at ground level with a ground-layer adaptive optics system. A case is also made to combine these two methods to further improve the image quality.

2008

Adaptive optics sky coverage for dome C telescopes
Article scientifique ArODES

J. S. Lawrence, M. C. B. Ashley, J. W. V. Storey, Laurent Jolissaint, T. Travouillon

Publications of the Astronomical Society of the Pacific,  2008, vol. 120, no. 872, pp. 1119-1127

Lien vers la publication

Résumé:

The unique atmospheric characteristics found at Dome C on the Antarctic plateau offer significant advantages for the operation of adaptive optics systems. An analysis is presented here comparing the performance of adaptive optics systems on telescopes located at Dome C with similar systems located at a mid-latitude site. The large coherence length, wide isoplanatic angle, and long coherence time of the Dome C atmosphere allow an adaptive optics system located there to correct to high order, observe over wide fields and use faint guide stars, resulting in a lower total wavefront error and a significant increase in sky coverage factor than can be achieved at a typical mid-latitude site. While the same performance could in principle be achievable at mid-latitude sites, this would only occur under exceptionally stable atmospheric conditions that are likely to occur on only a few nights per year.

2007

Speckle noise and dynamic range in coronagraphic images
Article scientifique ArODES

Rémi Soummer, André Ferrari, Claude Aime, Laurent Jolissaint

The Astrophysical Journal,  2007, vol. 669, no. 1, pp. 642-656

Lien vers la publication

Résumé:

This paper is concerned with the theoretical properties of high-contrast coronagraphic images in the context of exoplanet searches. We derive and analyze the statistical properties of the residual starlight in coronagraphic images and describe the effect of a coronagraph on the speckle and photon noise. Current observations with coronagraphic instruments have shown that the main limitations to high-contrast imaging are due to residual quasi-static speckles. We tackle this problem in this paper and propose a generalization of our statistical model to include the description of static, quasi-static, and fast residual atmospheric speckles. The results provide insight into the effects on the dynamic range of wave front control, coronagraphy, active speckle reduction, and differential speckle calibration. The study is focused on ground-based imaging with extreme adaptive optics, but the approach is general enough to be applicable to space, with different parameters.

2006

Performance modeling of a wide-field ground-layer adaptive optics system
Article scientifique ArODES

David R. Andersen, Jeff Stoesz, Simon Morris, Michael Lloyd-Hart, David Crampton, Laurent Jolissaint

Publications of the Astronomical Society of the Pacific,  2006, vol. 118, no. 849, pp. 1574–1590

Lien vers la publication

Résumé:

Using five independent analytic and Monte Carlo simulation codes, we have studied the performance of wide‐field ground‐layer adaptive optics (GLAO), which can use a single, relatively low order deformable mirror to correct the wave‐front errors from the lowest altitude turbulence. GLAO concentrates more light from a point source in a smaller area on the science detector, but unlike with traditional adaptive optics, images do not become diffraction‐limited. Rather, the GLAO point‐spread function (PSF) has the same functional form as a seeing‐limited PSF and can be characterized by familiar performance metrics such as full width at half‐maximum (FWHM). The FWHM of a GLAO PSF is reduced by 0 farcs1 or more for optical and near‐infrared wavelengths over different atmospheric conditions. For the Cerro Pachón atmospheric model, this correction is even greater when the image quality is poorest, which effectively eliminates "bad seeing" nights; the best seeing‐limited image quality, available only 20% of the time, can be achieved 60%–80% of the time with GLAO. This concentration of energy in the PSF will reduce required exposure times and improve the efficiency of an observatory up to 30%–40%. These performance gains are relatively insensitive to a number of trade‐offs, including the exact field of view of a wide‐field GLAO system, the conjugate altitude and actuator density of the deformable mirror, and the number and configuration of the guide stars.

Spatial frequency analytical modeling of adaptive optics for diffraction limited coronagraphs studies on extremely large segmented telescopes
Article scientifique ArODES

Laurent Jolissaint

EAS Publications Series,  2006, vol. 22, pp. 151-164

Lien vers la publication

Résumé:

In this paper, we briefly describe the principle of analytical modelization of the adaptive optics (AO) corrected point spread function in the spatial frequency domain, both for the turbulent and the telescope static aberrations, and demonstrate how this can be used for simulating AO corrected phase screens on extremely large hexagonal segmented telescopes, required for performance analysis of diffraction limited coronagraphs.

2024

Discovery space and science with the PLACID stellar coronagraph
Conférence ArODES

Ruben Tandon, Liurong Lin, Axel Potier, Laurent Jolissaint, Audrey Baur, Derya Öztürk Cetni, Jonas G. Kühn

Proceedings of SPIE Astronomical Teelscopes + Instrumentation, 16-22 June 2024, Yokohama, Japan

Lien vers la conférence

Résumé:

The world’s first ever “adaptive stellar coronagraph” facility will be the PLACID instrument, installed on Turkey’s new national observatory 4-m DAG telescope. PLACID incorporates a customized spatial light modulator (SLM) acting as a dynamically addressed focal-plane phase mask (FPM) coronagraph in the H – Ks bands. This new approach to high-contrast imaging will be applied on-sky in late 2024/early 2025. We present a first estimate of the science discovery space for PLACID, in terms of known exoplanets and brown dwarfs, considering raw lab contrast, contrast ratios, limiting magnitudes, coronagraphic inner working angle etc. In the future, we will also look into predicted disk and binary or multiple stars systems imaging performance, with the latter being a possible niche science case for the instrument (adaptive FPM for multiple stars). This work will inform on the first light PLACID commissioning activities and early science on the DAG telescope and is deemed to evolve in function of future developments on the DAG AO instrumentation suite.

The programmable liquid-crystal active coronagraphic imager for the DAG telescope (PLACID) instrument :
Conférence ArODES
on-site status update ahead of first light

Jonas G. Kühn, Laurent Jolissaint, Audrey Baur, Liurong Lin, Axel Potier, Ruben Tandon, Derya Öztürk Cetni, Daniele Piazza, Mathias Brändli, Iljadin Manurung, Martin Rieder

Proceedings of SPIE Astronomical Telescopes + Instrumentation, 16-22 June 2024, Yokohama, Japan

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Résumé:

The Programmable Liquid-crystal Active Coronagraphic Imager for the DAG telescope (PLACID) instrument is a novel high-contrast direct imaging facility that was recently delivered to the Turkish 4-m DAG telescope, with first light anticipated by the end of 2024. In a nutshell, PLACID consists in a fore-optics coronagraphic intermediate stage platform, installed in-between the TROIA XAO system and the DIRAC HAWAII-1RG focal-plane array. The PLACID project, led by a consortium of Swiss Universities contracted by the Atatürk University Astrophysics Research and Application Center (ATASAM), has passed the Delivery Readiness Review (DRR) milestone in September 2023, and was delivered to ATASAM campus facilities in March 2024. The PLACID commissioning activities with the calibration light source at the summit, on the DAG telescope Nasmyth platform, are foreseen to take place this fall, with first light scheduled to take place before the end of the year. When on-sky, PLACID will be the world’s first “active coronagraph” facility, fielding a customized spatial light modulator (SLM) acting as a dynamically programmable focal-plane phase mask (FPM) coronagraph from H- to Ks-band. This will provide a wealth of novel options to observers, among which software-only abilities to change or re-align the FPM pattern in function of conditions or science requirements, free of any actuator motion. Future features will include non-common path aberrations (NCPA) self-calibration, optimized coronagraphy for binary stars, as well as coherent differential imaging (CDI). We hereby present the delivered PLACID instrument, its current capabilities, and Factory Acceptance commissioning results with relevant performance metrics.

2022

Eastern Anatolia Observatory (DAG) :
Conférence ArODES
the status in 2022, towards the first light

C. Yesilyaprak, O. Keskin, Laurent Jolissaint

Proceedings Ground-based and Airborne Telescopes IX, SPIE Astronomical Telescopes + Instrumentation

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Résumé:

East Anatolian Observatory’s DAG telescope, with its 4m diameter primary mirror and VIS/IR observation capability, Eastern Anatolian Observatory’s 4m diameter class DAG telescope, with VIS/IR observation capability, will be located on the Konaklı-Karaya summit at an altitude of 3170 m, near the city of Erzurum, Turkey. DAG contains both active optics (aO) and adaptive optics (AO) systems. With the enclosure assembly nearly done, and the dummy mirror integration including the M1 cell integration performed at the end of 2021; DAG telescope's AIV is planned to take place by the end of May/2022 and the Provisional Acceptance by November/2022. DAG is equipped with an in-flange derotator – KORAY (K-mirror Optical RelAY) that will direct the light to the seeing limited Nasmyth platform containing TROIA (TuRkish adaptive Optics system for Infrared Astronomy). The scientific instruments that DAG will receive in 2022, are but not limited to, a stellar coronagraph and a 30" NIR diffraction limited camera. In his paper, a global status update and expected optical performance characteristics will be presented.

TROIA adaptive optics system for DAG telescope :
Conférence ArODES
assembly and laboratory performance prior to on-sky assessment

Onur Keskin, Laurent Jolissaint, Audrey Bouxin, Cahit Yesilyaprak

Proceedings Volume 12185, Adaptive Optics Systems VIII; 121851W (2022) SPIE Astronomical Telescopes + Instrumentation

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Résumé:

In this article, we describe the current status of the development of TROIA ∗, a pyramid wavefront sensor based adaptive optics system designed for DAG, a new 4 m telescope located in Eastern Anatolia, Turkey. The wavefront uses a no-noise electron-multiplied CCD camera, and the deformable mirror has a large actuators density, allowing coronagraphic science in one hand, but also system optimization for low light level or bad seeing conditions thanks to the versatility of the P-WFS. We describe the optical design, the mounting and alignment procedure and our loop control concept. Closed loop results are described, showing that while there are still many issues to fix before the sky version, the system behaves as expected.

Design of the near infrared camera DIRAC for East Anatolia Observatory
Conférence ArODES

Ross Zhelem, Robert Content, Vladimir Churilov, Yevgen Kripak, Lew Waller, Scott Case, Slavko Mali, Rolf Muller, Mario Gonzalez, Dave Adams, Nick Binos, Timothy Chin, Tony Farrell, Urs Klauser, Yuriy Kondrat, Nirmala Kunwar, Jon Lawrence, Nuria Lorente, Summer Luo, Erica McDonald, Helen McGregor, Vijay Nichani, Naveen Pai, Minh Vuong, Jahanzeb Zahoor, Jessica Zheng, Barnaby Norris, julia Bryant, Annino Vaccarella, Nick Herrald, James Gilbert, Cahit Yesilyaprak, Bulent Gucsav, Deniz Coker, Onur Keskin, Laurent Jolissaint

Proceedings Volume 12184, Ground-based and Airborne Instrumentation for Astronomy IX; 1218440 SPIE Astronomical Telescopes + Instrumentation

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Résumé:

The 4m DAG telescope is under construction at East Anatolia Observatory in Turkey. DIRAC, the “DAG InfraRed Adaptive optics Camera”, is one of the facility instruments. This paper describes the design of the camera to meet the performance specifications. Adaptive and auxiliary optics relay the telescope F/14 input 1:1 into DIRAC. The camera has an all refractive design for the wavelength range 0.9 - 2.4 micron. Lenses reimage the telescope focal plane 33 x 33 as (9 x 9 mm) on a 1k x 1k focal plane array. With magnification of 2x, the plate scale on the detector is 33 mas/pixel. There are 4 standard filters (Y, J, H, K) and 4 narrowband continuum filters. A 12 position filter wheel allows installation of 2 extra customer filters for specific needs; the filter wheel also deploys a pupil viewer lens. Optical tolerancing is carried out to deliver the required image quality at polychromatic Strehl ratio of 90% with focus compensator. This reveals some challenges in the precision assembly of optics for cryogenic environments. We require cells capable of maintaining precision alignment and keeping lenses stress free. The goal is achieved by a combination of flexures with special bonding epoxy matching closely the CTE of the lens cells and crystalline materials. The camera design is very compact with object to image distance <220 mm and lens diameters <25 mm. A standalone cryostat is LN2 cooled for vibration free operation with the bench mounted adaptive optics module (TROIA) and coronagraph (PLACID) at the Nasmyth focus of the DAG telescope.

2020

Advances for the 4m DAG Telescope in Flange de-rotator
Conférence ArODES

Onur Keskin, Ali Cem Unal, Ilker Murat Koc, Laurent Jolissaint, Cahit Yesilyaprak

Ground-based and Airborne Telescopes VIII ; Proceedings Volume 11445, Ground-based and Airborne Telescopes VIII; 1144545 (2020) ; SPIE Astronomical Telescopes + Instrumentation, 13 December 2020, Online Only

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Résumé:

The purpose of this study is expressing advances in design stages for in flange optical field derotator system for 4 meters DAG Telescope. In-Flange Derotator KORAY (K-mirror OpticalRelAY) is designed, analysed and manufactured to meet the specifications of DAG telescope. DAG telescope, situated at Erzurum/Karakaya summit at 3150m altitude, is the first Turkish optical telescope with VIS(Visible) and IR (Infrared) observation capability. DAG, designed by Turkish engineers at FMV Isik University, is also the largest telescope (4m diameter) in Turkey and in European continent. Being one of the 2023 vision projects; the first light of DAG is expected to take place in 2021. This purpose brings some real-life challenges such as design limitations, material selection and electronic integration.

Review of PSF reconstruction methods and application to post-processing
Conférence ArODES

O. Beltramo-Martin, S. Ragland, R. Fétick, C. Correia, T. Dupuy, G. Fiorentino, T. Fusco, Laurent Jolissaint, S. Kamann, A. Marasco, D. Massari

Adaptive Optics Systems VII ; Proceedings Volume 11448, SPIE Astronomical Telescopes + Instrumentation, 13 December 2020, Online Only

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Résumé:

Determining the PSF remains a key challenge for post adaptive-optics (AO) observations regarding the spatial, temporal and spectral variabilities of the AO PSF, as well as itx complex structure. This paper aims to provide a non-exhaustive but classified list of techniques and references that address this issue of PSF determination, with a particular scope on PSF reconstruction, or more generally pupil-plane-based approaches. We have compiled a large amount of references to synthesize the main messages and kept them at a top level. We also present applications of PSF reconstruction/models to post-processing, more especially PSF-fitting and deconvolution for which there is a fast progress in the community.

SLM-based active focal-plane coronagraphy :
Conférence ArODES
status and future on-sky prospects

Jonas G. Kühn, Laurent Jolissaint, Audrey Bouxin, Polychronis Patapis

Proceedings Volume 11451, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV; 114511S (2021) ; SPIE Astronomical Telescopes + Instrumentation, 14-18 December 2020, Online Only

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Résumé:

We recently started to investigate how liquid-crystal on silicon (LCOS) spatial light modulator (SLM) would perform as programmable focal-plane phase mask (FPM) coronagraphs. Such “adaptive coronagraphs” could potentially help adapt to observing conditions, but also tackle specific science cases (e.g. binary stars). Active FPMs may play a role in the context of segmented telescope pupils, or to implement synchronous coherent differential imaging (CDI). We present a status update on this work, notably early broadband contrast performance results using our new Swiss Wideband Active Testbed for High-contrast imaging (SWATCHi) facility. Finally, we unveil the upcoming near-infrared PLACID instrument, the Programmable Liquid-crystal Adaptive Coronagraphic Imager for the 4-m DAG observatory in Turkey, with a first light planned for the end of the year 2022.

TROIA adaptive optics system for DAG Telescope
Conférence ArODES

Onur Keskin, Laurent Jolissaint, Audrey Bouxin, Cahit Yesilyaprak

Proceedings Volume 11448, Adaptive Optics Systems VII; 114481P (2020) ; SPIE Astronomical Telescopes + Instrumentation, 14-18 December 2020, Online Only

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Résumé:

This paper presents the specifications of TROIA - TuRkish adaptive Optics system for Infrared Astronomy system, the science rationale for these specifications, and description of the site technical and environmental conditions to be taken into account in the adaptive optics (AO) system design for the Eastern Anatolia Observatory - DAG telescope. With it’s 468 actuators, EMCCD camera, and the pyramid wavefront sensor configuration; TROIA is able to adapt the degree of correction to a given guide star (GS) brightness during observations. The high actuator density of TROIA AO system will allow DAG to perform astronomical observations at ExAO performances.

2018

A flexible adaptive optics concept for general purpose high angular resolution science on the DAG 4 m telescope
Conférence ArODES

Laurent Jolissaint, Audrey Bouxin, Ulas S. Gökay, Onur Keskin, François Rigaut, Cahit Yesilyaprak

Proceedings of SPIE. Adaptive Optics Systems VI, 10 - 15 June 2018, Austin, Texas, United States

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Résumé:

Thanks to the availability of high actuator density deformable mirrors (ALPAO 468 DM), the high versatility of the pyramid wavefront sensor and above all, the venue of essentially no noise EMCCD detectors, it becomes possible to fully adapt the degree of correction of an adaptive optics system for a given guide star brightness and atmospheric condition. Indeed, when the conditions are very good, the high actuator density of the DM allows to reach a high Strehl by using all the modes, and when the conditions are less favorable, the spatial sampling, i. the number of modes, and the sensitivity of the detector allows to maximize the Strehl beyond what would be possible with a classical, frozen SH-WFS based system. Beside, oversampling the detector allows to relax the specification on the pupil images given by the pyramid on the detector, which in turn relaxes the pyramid prism manufacturing specifications. We are now designing an AO system for the DAG 4 m telescope that will allow, on the same system, ExAO as well as low order improved seeing observations. This article reports on the AO performance analysis, the final optical design and the design of the double prism achromatic pyramid.

Project management and status update for DAG (Eastern Anatolia Observatory) the 4 meter VIS/IR optical telescope
Conférence ArODES

O. Keskin, C. Yesilyaprak, Laurent Jolissaint

Modeling, Systems Engineering, and Project Management for Astronomy VIII

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Résumé:

The new 4 m Turkish telescope, DAG (East Anatolian Observatory, Fig. 2), will be located on the summit of the mountain Konaklı-Karakaya, at an altitude of 3170 m, near the city of Erzurum, Turkey. First light is expected for August 2020. The telescope is a multi-purpose instrument, and will run observations both in the visible (VIS) and near infrared (NIR) domains, in seeing limited (SL) and adaptive optics (AO) correction mode. In his paper, status updates from DAG telescope will be presented in terms of; (i) DAG telescope optics, (ii) Nasmyth focal planes and platforms, (iii) current progress of the telescope, (iii) current progress of enclosure, (iv) current progress of the observatory building, (v) current process of the astronomical instruments & tendering phase, and (Vi) status of the Optomechatronics Research Laboratory – OPAL.

Nonlinear estimation with a pyramid wavefront sensor
Conférence ArODES

Richard A. Frazin, Laurent Jolissaint

Adaptive Optics Systems VI

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Résumé:

Due to its high sensitivity and minimal aliasing, the pyramid wavefront sensor (PyWFS) is becoming a popular choice for astronomical adaptive optics. To date, all implementations of the PyWFS modulate the input beam in order to operate the device the linear regime, however, this modulation reduces the sensitivity. Simulations in a recently published article show that model-based nonlinear estimation techniques can extend the range in which the PyWFS can be used without modulation, thus allowing modulation-free operation at lower Strehl values than previously thought possible. Further, the article shows that required calculations for the model-based nonlinear estimation do not require any real-time optical simulations and can be performed in massively parallel fashion, thus, (hopefully) allowing onsky implementation. The model-based estimation requires a realistic and phase-accurate, calibrated computational model (CCM) of the PyWFS. This article summarizes the potential benefits of modelbased nonlinear estimation and outlines a procedure to obtain the needed CCM.

Status of point spread function determination for Keck adaptive optics
Conférence ArODES

S. Ragland, T. J. Dupuy, P.L. Wizinowich, Laurent Jolissaint, J. R. Lu

Adaptive Optics Systems VI

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Résumé:

The progress achieved in implementing Point Spread Function reconstruction (PSF-R) capability at W. M. Keck Observatory (WMKO) is discussed. Observations of low-mass binary systems have been used to evaluate the improvements in astrometry and photometry using reconstructed PSFs. The on-sky performance of PSF-R is discussed by comparing the binary-fitting analysis using the reconstructed PSFs with the standard methods. We show that the PSFR in the NGS provides comparable performance to having a close reference star in the imaging science instrument. The on-sky troubleshooting efforts and the recent PSF-R technical developments are also presented. We find that the PSF-R reconstruction is more of a systems science problem that a post-processing problem. We close by discussing the lessons learned in the context of existing and future extremely large telescopes.

2016

Point spread function determination for Keck adaptive optics
Conférence ArODES

S. Ragland, Laurent Jolissaint, P. Wizinowich, M. A. van Dam, L. Mugnier, Audrey Bouxin

Adaptive Optics Systems V

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Design of a derotator for the 4 m DAG telescope
Conférence ArODES

Jérémie Baudet, Laurent Jolissaint, Onur Keskin, Cahit Yesilyaprak, Sinan K. Yerli

Ground-based and Airborne Instrumentation for Astronomy VI

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Résumé:

This paper summarize our work on the design of a field derotator for the adaptive optics instruments Nasmyth platform of DAG (Dogu Anadolu Gozlemevi), a new 4 m telescope for astronomical observations near the city of Erzurum, Turkey. While the telescope follows an astronomical object, its pupil sees a rotation of the object around the optical axis which depends on the telescope geographic coordinate and the object sky coordinate. This effect is called the field rotation. This rotation needs to be compensated during the astronomical object data acquisition. In this report we demonstrate the feasibility of placing the derotator (a K-mirror design) in the telescope fork central hole and propose a preliminary design, considering flexures.

The design of an adaptive optics telescope :
Conférence ArODES
the case of DAG

Laurent Jolissaint, Onur Keskin, Lorenzo Zago, Sinan Kaan Yerli, Cahit Yesilyaprak

Ground-based and Airborne Telescopes VI : proceedings of the SPIE astronomical telescopes + instrumentation

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Résumé:

In this paper, we describe in detail the optical design of DAG, a new 4 m telescope for Turkey. DAG is an "adaptive optics friendly" telescope, in a sense that each design decision is taken considering the potential impact on the AO performance (vibrations, static aberrations etc.) The objective is to make this telescope fully ready for AO at first light. It is designed as a Ritchey-Chrétien combination, 56 m focal length, with Nasmyth foci only, and active optics. Its total RMS error is expected to be 45 nm up to Zernike mode 78, and 26 nm for the higher, non AO corrected modes. A final design optimization has been done by the telescope manufacturers, demonstrating that our AO-based requirements can be satisfied, without much difficulty.

2015

Adaptive optics point spread function reconstruction at W. M. Keck Observatory in laser & natural guide star modes :
Conférence ArODES
final developments

Laurent Jolissaint, Sam Ragland, Peter Wizinowich

Proceedings of the 4th Adaptive Optics for Extremely Large Telescopes Meeting (AO4ELT4)

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Résumé:

We present the final development of our point spread function reconstruction algorithm for the Keck-II telescope adaptive optics system, in laser and natural guide star modes. The method makes use of AO loop telemetry, nearby C2N profiler data, and on-sky phase diversity. We describe the fundamental assumptions and the mathematical models for each components of the residual phase structure function. The reconstructed PSF is compared with on-sky single star PSF. We emphasize the importance of access to a good telemetry and the fact that non-common path aberrations also affects PSF-R. The global, statistical quality of the reconstructed PSF demonstrates the validity of the method. The algorithm is now ready for AO science data reduction (see the companion overview paper, Ragland et al.1 - this conference).

2014

Discretized aperture mapping with a micro-lenses array for interferometric direct imaging
Conférence ArODES

Fabien Patru, Jacopo Antichi, Dimitri Mawet, Laurent Jolissaint, Marcel Carbillet

Adaptive Optics Systems IV

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Résumé:

Discretized Aperture Mapping (DAM) appears as an original filtering technique easy to play with existing adaptive optics (AO) systems. In its essential DAM operates as an optical passive filter removing part of the phase residuals in the wavefront without introducing any difficult-to-align component in the Fourier conjugate of the entrance pupil plane. DAM reveals as a new interferometric technique combined with spatial filtering allowing direct imaging over a narrow field of view (FOV). In fact, the entrance pupil of a single telescope is divided into many sub-pupils so that the residual phase in each sub-pupil is filtered up to the DAM cut-off frequency. DAM enables to smooth the small scale wavefront defects which correspond to high spatial frequencies in the pupil plane and to low angular frequencies in the image plane. Close to the AO Nyquist frequency, such pupil plane spatial frequencies are not well measured by the wavefront sensor (WFS) due to aliasing. Once bigger than the AO Nyquist frequency, they are no more measured by the WFS due to the fitting limit responsible for the narrow AO FOV. The corresponding image plane angular frequencies are not transmitted by DAM and are useless to image small FOVs, as stated by interferometry. That is why AO and DAM are complementary assuming that the DAM cut-off frequency is equal to the AO Nyquist frequency. Here we describe the imaging capabilities when DAM is placed downstream an AO system, over a convenient pupil which precedes the scientific detector. We show firstly that the imaging properties are preserved on a narrow FOV allowing direct imaging throughout interferometry. Then we show how the residual pupil plane spatial frequencies bigger than the AO Nyquist one are filtered out, as well as the residual halo in the image is dimmed.

Laser guide star adaptive optics point spread function reconstruction project at W. M. Keck Observatory :
Conférence ArODES
preliminary on-sky results

Laurent Jolissaint, Sam Ragland, Peter Wizinowich, Audrey Bouxin

Adaptive Optics Systems IV

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Résumé:

We present in this paper an analysis of our preliminary results for point spread function reconstruction in laser guide star (LGS) mode for the Keck-II adaptive optics system. Our approach is based on an update of the natural guide star algorithm with the LGS terms. The first reconstruction we have done is based on a set of 13 LGS runs (telemetry data and sky PSF) for which we demonstrate already a significant correlation between the reconstructed and sky PSF metrics. At this point of the project, though, our reconstructed PSF does not reproduce the sky PSF features (and this is expected) : we discuss why, and describe the different issues we have to solve, and the different experiment we will do, in order to achieve a good reconstruction.

Status of point spread function determination for Keck adaptive optics
Conférence ArODES

S. Ragland, Laurent Jolissaint, P. Wizinowich, C. Neyman

Adaptive Optics Systems IV

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Résumé:

There is great interest in the adaptive optics (AO) science community to overcome the limitations imposed by incomplete knowledge of the point spread function (PSF). To address this limitation a program has been initiated at the W. M. Keck Observatory (WMKO) to demonstrate PSF determination for observations obtained with Keck AO science instruments. This paper aims to give a broad view of the progress achieved in this area. The concept and the implementation are briefly described. The results from on-sky on-axis NGS AO measurements using the NIRC2 science instrument are presented. On-sky performance of the technique is illustrated by comparing the reconstructed PSFs to NIRC2 PSFs. Accuracy of the reconstructed PSFs in terms of Strehl ratio and FWHM are discussed. Science cases for the first phase of science verification have been identified. More technical details of the program are presented elsewhere in the conference.

Turkey's next big science project :
Conférence ArODES
DAG the 4 meter telescope

O. Keskin, C. Yesilyaprak, S. K. Yerli, Lorenzo Zago, Laurent Jolissaint

Ground-based and Airborne Telescopes V

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Résumé:

The DAG (Turkish for Eastern Anatolia Observatory) 4-m telescope project has been formally launched in 2012, being fully funded by the Government of Turkey. This new observatory is to be located on a 3170 m altitude ridge near the town of Erzurum in Eastern Anatolia. First light is scheduled for late 2017. The DAG team’s baseline design of the telescope consists of a Ritchey-Chretien type with alt-az mount, a focal length of 56 m and a field of view up to 30 arcmin. Multiple instruments will be located at the Nasmyth foci. The optical specifications of the telescope are set by DAG team for diffraction limited performance with active and adaptive optics. Modern mirror control technologies will allow defining in a most cost effective way the figuring requirements of the optical surfaces: the low order figuring errors of the combined optical train constituted of M1-M2-M3 are defined in terms of Zernike coefficients and referred to the M1 surface area. The high order figuring errors are defined using the phase structure functions. Daytime chilling of the closed enclosure volume and natural ventilation through suitable openings during observations will be used to ensure optimal mirror and dome seeing. A design of a ground layer adaptive optics (GLAO) subsystem is developed concurrently with the telescope. In this paper, main design aspects, the optical design and expected performance analysis of the telescope will be presented.

2012

Adaptive optics point spread function reconstruction project at W. M. Keck Observatory :
Conférence ArODES
first results with faint natural guide stars

Laurent Jolissaint, Chris Neyman, Julian Christou, Peter Wizinowich

Adaptive Optics Systems III

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Résumé:

We discuss in this paper the last results of our adaptive optics point spread function reconstruction (PSF-R) project at theW. M. Keck Observatory. Objective of the project are recalled, followed by a short reintroduction of the basis of the method. Amongst the novelties, a method for a drastic reduction of the number of the so-called Ui,j functions for any pupil shape and an arbitrary number of actuators is presented, making the current PSF-R technique easily applicable to extremely large telescopes AO systems. Our success at reconstructing the PSF in bright natural guide star (NGS) conditions is revisited in details and confirmed. First results on PSF-R with faint NGS are presented and it is shown that our reconstructed PSF Strehl ratio drops with the NGS magnitude basically like the measured sky performance. These preliminary but encouraging results, in real conditions, can be considered as a validation of our PSF-R approach. Plans for the next steps of the project are discussed at the end of this progress report.

Dimensioning and performances of an AO system for the SALT
Conférence ArODES

L. Catala, M. Carbillet, Laurent Jolissaint, D. A. H. Buckley, S. M. Crawford

Adaptive Optics Systems III

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Résumé:

The Southern African Large Telescope (SALT), located at the South African Astronomical Observatory (SAAO) site near Sutherland, South Africa, is an 11-metre fixed-elevation telescope currently operating at UV-visible wavelengths (320-950 nm) with a near-infrared extension (850-1700 nm) due in the near future. SALT does not currently have an adaptive optics (AO) system and a feasibility study for adding one is under way. Using results from an on-going site monitoring campaign at the SAAO we have begun carrying out simulations to investigate how different AO systems might perform and could be optimized for SALT. We will present the parameters of an optimization study and performance results for a single on-axis natural guide star (NGS) AO system on SALT for operation at both visible (R) and near-IR (J and H) wavelengths.

Retrieving the telescope and instrument static wavefront aberration with a phase diversity procedure using on-sky adaptive optics corrected images
Conférence ArODES

Laurent Jolissaint, Chris Neyman, Julian Christou, Laurent Mugnier, Peter Wizinowich

Adaptive Optics Systems III

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Résumé:

We present the results of a sky source based, phase diversity experiment at the W. M. Keck Observatory to retrieve the global wavefront static aberration from the telescope primary mirror to the science imager (NIRC2). The context of this study is a point spread function reconstruct (PSF-R) project for the Keck-II and Gemini- North adaptive optics systems. We demonstrate that if we select couples of in/out-of-focus PSF with identical seeing (determined with a deformable mirror based seeing monitor), retrieving the global static wavefront from AO corrected sky images is indeed possible. A sensitivity analysis shows that the reconstructed wavefront accuracy is very sensitive to errors in the knowledge of the system's optical parameters, and an accuracy of less than 1% is required. Recommendations for an accurate sky-based phase diversity static wavefront reconstruction are given, as well as our plan for the next steps of this project at the W. M. Keck Observatory.

2011

Analytical versus end-to-end numerical modeling of adaptive optics systems :
Conférence ArODES
comparison between the code PAOLA and the Software Package CAOS

Marcel Carbillet, Laurent Jolissaint

Proceedings of the 2nd International Conference on Adaptive Optics for Extremely Large Telescopes

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Résumé:

We compare in this contribution the analytical approach together with the so-called "end-to-end" approach in the framework of astronomical adaptive optics (AO) modeling. The two tools used for this purpose are well-known and already widely used within the astronomical AO community: PAOLA (Jolissaint et al. 2006, Jolissaint 2010) on the one hand, and the Software Package CAOS (Carbillet et al. 2005) on the other hand. In addition to inter-validate the two codes, trade-offs are clearly searched in order to find optimal compromises permitting to face both exploratory simulations and large instrumental projects while combining effectiveness and certainty.

Practical experience with AO PSF reconstruction at the Keck and Gemini telescopes
Conférence ArODES

Laurent Jolissaint, Chris Neyman, Julian Christou, Laurent Mugnier, Peter Wizinowich

Proceedings of the 2nd AO4ELT conference

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Résumé:

Estimating the point spread function across the imaged field, for a given AO run, is critical for AO data reduction. In this talk I will describe our recent progress (Summer 2011) on PSF reconstruction for the Gemini North (ALTAIR) and Keck NGS based AO systems. I will shortly re-introduce the basic theory, but will put the emphasize on practical implementation issues we are facing at this two facilities, in particular how we handle and determine/calibrate the non-turbulent aberrations (telescope, instrument optics) whose amplitude can be as large as the turbulent aberrations.

2010

Adaptive optics point spread function reconstruction :
Conférence ArODES
lessons learned from on-sky experiment on Altair/Gemini and pathway for future systems

Laurent Jolissaint, Julian Christou, Peter Wizinowich, Eline Tolstoy

Adaptive Optics Systems II

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Résumé:

We present the results of an on-sky point spread function reconstruction (PSF-R) experiment for the Gemini North telescope adaptive optics system, Altair, in the simplest mode, bright on-axis natural guise star. We demonstrate that our PSF-R method does work for system performance diagnostic but suffers from hidden telescope and system aberrations that are not accounted for in the model, making the reconstruction unsuccessful for Altair, for now. We discuss the probable origin of the discrepancy. In the last section, we propose alternative PSF-R methods for future multiple natural and laser guide stars systems.

Imaka
Conférence ArODES
a Lagrange invariant of ELTs

Olivier Lai, Mark R. Chun, John Pazder, Jean-Pierre Véran, Laurent Jolissaint

Adaptive Optics Systems II

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Résumé:

The IMAKA project is a ground layer corrected wide field visible imager proposed for CFHT. It consists of three processes or components: The dome and local turbulence will be controlled by ventilation; the remaining ground layer turbulence will be corrected by a GLAO system and the free atmosphere seeing will be locally reduced by using an Orthogonal Transfer CCD to correct for tip-tilt within the isokinetic angle of field stars. In designing the AO system, whether based on an adaptive secondary mirror or using pupil relay optics, it becomes apparent that the conjugation of the deformable mirror is a difficult constraint to achieve given the large field. It turns out this problem is not isolated to IMAKA, because the Lagrange Invariant for our project is in the same range as that of EAGLE on the E-ELT for example. The effects of tilting the deformable mirror with respect to the pupil or compensating for misconjugation of an adaptive secondary mirror using a tomographic reconstructor have been investigated using Monte-Carlo simulation codes, including our code developed specifically for GLAO simulations. We report on quantitative results from IMAKA simulations for a variety of realistic turbulence conditions for each topical scheme, and allude to how these results are applicable to ELTs' adaptive optics.

METIS :
Conférence ArODES
system engineering and optical design of the mid-infrared E-ELT instrument

Rainer Lenzen, Bernhard R. Brandl, Eric Pantin, Alistair Glasse, Joris Blommaert, Laurent Jolissaint

Ground-based and Airborne Instrumentation for Astronomy III

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Résumé:

METIS is a mid-infrared instrument proposed for the European Extremely Large Telescope (E-ELT). It is designed to provide imaging and spectroscopic capabilities in the 3μm to 14μm region up to a spectral resolution of 100.000. Here the technical concept of METIS is described which has been developed based on an elaborated science case which is presented elsewhere in this conference. There are five main opto-mechanical modules all integrated into a common cryostat: The fore-optics is re-imaging the telescope focal plane into the cryostat, including a chopper, an optical de-rotator and an un-dispersed pupil stop. The imager module provides diffraction limited direct imaging, low-resolution grism spectroscopy, polarimetry and coronagraphy. The high resolution IFU spectrograph offers a spectral resolution of 100.000 for L- and M-band and optional 50.000 for the N-band. In addition to the WFS integrated into the E-ELT, there is a METIS internal on-axis WFS operating at visual wavelengths. Finally, a cold (and an external warm) calibration unit is providing all kinds of spatial and spectral calibrations capabilities. METIS is planned to be used at one of the direct Nasmyth foci available at the E-ELT. This recently finished Phase-A study carried out within the framework of the ESO sponsored E-ELT instrumentation studies has been performed by an international consortium with institutes from Germany, Netherlands, France, United Kingdom and Belgium.

Mid-infrared astronomy with the E-ELT :
Conférence ArODES
performance of METIS

S. Kendrew, Laurent Jolissaint, B. Brandl, R. Lenzen, E. Pantin

Ground-based and Airborne Instrumentation for Astronomy III

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Résumé:

We present results of performance modelling for METIS, the Mid-infrared European Extremely Large Telescope Imager and Spectrograph. Designed by a consortium of NOVA (Netherlands), UK Astronomy Technology Centre (UK), MPIA Heidelberg (Germany), CEA Saclay (France) and KU Leuven (Belgium), METIS will cover the atmospheric windows in L, M and N-band and will offer imaging, medium-resolution slit spectroscopy (R~1000- 3000) and high-resolution integral field spectroscopy (R~100,000). Our model uses a detailed set of input parameters for site characteristics and atmospheric profiles, optical design, thermal background and the most up-to-date IR detector specifications. We show that METIS will bring an orders-of-magnitude level improvement in sensitivity and resolution over current ground-based IR facilities, bringing mid-IR sensitivities to the micro- Jansky regime. As the only proposed E-ELT instrument to cover this entire spectral region, and the only mid-IR high-resolution integral field unit planned on the ground or in space, METIS will open up a huge discovery space in IR astronomy in the next decade.

Modeling the spatial PSF at the VLT focal plane for MUSE WFM data analysis purpose
Conférence ArODES

Denis Serre, Emma Villeneuve, Hervé Carfantan, Laurent Jolissaint, Vincent Mazet

Adaptive Optics Systems II

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Résumé:

MUSE is the Multi Unit Spectroscopic Explorer, an AO-assisted integral field spectrograph for visible and near-IR wavelengths which is planned to be commissioned at the UT4 of the Very Large Telescope in 2012.1 We present the status on the modeling of the spatial PSF at the UT focus and its Field-of-View (FoV) and spectral variations. Modeling these variations and studying their implications is a cornerstone for some MUSE data analysis and processing problems such as fusion, source extraction and deconvolution of MUSE datacubes. In Wide Field Mode (WFM, 1 square arc-minute FoV, 0.2 arcsec spatial sampling), MUSE can operate without Adaptive Optics (AO) correction or with a Ground Layer Adaptive Optics facility aimed at providing an almost uniform correction over a large field of view. In Narrow Field Mode (7.5 square arcseconds FoV, 0.025 arcsec spatial sampling) MUSE will make use of a Laser Tomography Adaptive Optics reconstruction, implying stronger spatial variations. By using the adaptive optics simulation tool PAOLA, we simulate in WFM the spatial PSF as a function of atmospheric turbulence parameters, observed wavelengths, AO mode and position in the field of view. We then develop a mathematical model fitting the generated data which allows, with a small number of parameters, to approximate the PSF at any spatial and spectral position of MUSE datacube. Finally, we evaluate the possibility to estimate the model parameters directly from the (future) MUSE data themselves.

Optical modelling of the European Extremely Large Telescope for high-contrast imaging tasks
Conférence ArODES

Szymon Gladysz, Laurent Jolissaint

Modeling, Systems Engineering, and Project Management for Astronomy IV

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Résumé:

We study the capability of the European Extremely Large Telescope to image exoplanets. For this task we have developed a simulation which models the telescope, adaptive-optics systems, coronagraphs, science instrument, which is the integral field spectrograph in our case, and image post-processing.

The CAOS problem-solving environment :
Conférence ArODES
recent developments

Marcel Carbillet, Gabriele Desidera, Evelyne Augier, Andrea La Camera, Armando Riccardi, Laurent Jolissaint

Adaptive Optics Systems II

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Résumé:

We present recent developments of the CAOS problem-solving environment (PSE), an IDL-based software tool whose original aim was to define and simulate as realistically as possible the behavior of a generic adaptive optics (AO) system -from the atmospheric propagation of light, to the sensing of the wave-front aberrations and the correction through a deformable mirror- but which results in a widely more general tool now. In fact, the different developments made through the last years result in a very versatile numerical tool complete of a global graphical interface (the CAOS Application Builder), a general utilities library (the CAOS Library), and different packages dedicated to a wide range of astronomical-optics-related scientific topics: the original package designed for end-to-end AO system simulations (the Software Package CAOS), an image simulation/ reconstruction package with interferometric capabilities (the Software Package AIRY), an extension of the latter specialized for the LBT instrument LINC-NIRVANA (the Software Package AIRY-LN), an ad hoc package dedicated to the VLT instrument SPHERE (the Software Package SPHERE), and an embedment of the analytical AO simulation code PAOLA (the Software Package PAOLAC).We present the status of the whole CAOS PSE, together with the most recent developments, and plans for the future of the overall tool.

The METIS AO system :
Conférence ArODES
bringing extreme adaptive optics to the mid-IR

R. Stuik, Laurent Jolissaint, S. Kendrew, S. Hippler, B. Brandl

Adaptive Optics Systems II

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Résumé:

METIS (Mid-infrared E-ELT Imager and Spectrometer) is the mid-infrared instrument proposed for the European Extremely Large Telescope (E-ELT). METIS will be the first instrument in the mid-IR that will actually require an Adaptive Optics system in order to reach a performance close to the diffraction limit. Extending Adaptive Optics for the mid-IR from the current generation of telescopes to 30-42 meter telescopes is technically challenging, but appears at first sight significantly easier than at visible and near infrared wavelengths. Adaptive Optics has been demonstrated to deliver Strehl Ratios exceeding 95% on 6-8 meter class telescopes at 10 microns, but achieving this performance on E-ELTs under normal observation conditions, requires that several higher order effects are taken into account. The performance of a mid-IR AO system drops significantly if refractivity effects and atmospheric composition variations are not compensated. Reaching Strehl Ratios of over 90% in the L, M and N band will require special considerations and will impact the system design and control scheme of AO systems for mid-IR on ELTs. The METIS instrument has finalized its preliminary design phase and in this paper we present the results of our performance estimates of the METIS AO system. We have included the effects of refractivity and composition fluctuations on the performance of the AO system and we have investigated how these effects impact the science cases for mid-IR instrumentation on an ELT.

The CAOS problem-solving environment :
Conférence ArODES
last news

M. Carbillet, G. Desidera, E. Augier, A. La Camera, A. Riccardi, Laurent Jolissaint

Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics 2010

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Résumé:

We present recent developments of the CAOS problem-solving environment (PSE), an IDL-based software tool complete of a global graphical interface, a general utilities library, and different specialized scientific packages going from end-to-end and analytical simulations to image simulation/reconstruction, with specialization to given instruments.

2009

Extreme adaptive optics in the mid-IR :
Conférence ArODES
the METIS AO system

Remko Stuik, Laurent Jolissaint, Sarah Kendrew, Stefan Hippler, Bernhard Brandl

Proceedings of the XXVIIth International Astronomical Union

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Imaging extrasolar planets with the European Extremely Large Telescope
Conférence ArODES

S. Gladysz, B. F. Castella, M. Kissler-Patig, R. Rebolo, Laurent Jolissaint

EPJ Web of Conferences : proceedings of "Research, Science and Technology of Brown Dwarfs and Exoplanets"

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Résumé:

The European Extremely Large Telescope (E-ELT) is the most ambitious of the ELTs being planned. With a diameter of 42 m and being fully adaptive from the start, the E-ELT will be more than one hundred times more sensitive than the present-day largest optical telescopes. Discovering and characterising planets around other stars will be one of the most important aspects of the E-ELT science programme. We model an extreme adaptive optics instrument on the E-ELT. The resulting contrast curves translate to the detectability of exoplanets.

Modeling the chromatic correction error in adaptive optics :
Conférence ArODES
application to the case of mid-infrared observations in dry to wet atmospheric conditions

Laurent Jolissaint, Sarah Kendrew

Proceedings of the 1st AO4ELT conference

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Résumé:

In this paper we extend to the mid-IR previous work from other authors on the effect of the chromatic correction error in adaptive optics, including the contribution of atmospheric water vapor content. An analytic model of the closed-loop AO corrected residual phase spatial power spectrum is presented that includes the overall mixed effect of anisoplanatism, servo-lag and refractive index dispersion. Calculating the Strehl ratio loss as a function of the refractive index dispersion, we demonstrate that (1) the error variance grows with the optical turbulence phase variance, but thanks to the aberration-damping effect of the outer scale of optical turbulence for large apertures, chromatic correction error variance is much reduced in comparison with an infinite outer scale case and is not a significant issue for ELTs; (2) in the mid-IR wavelengths, where the fluctuations of the refractive index of air due to water absorption lines are particularly strong, chromatic correction error might become relatively significant in terms of wavefront error (in the range 10-100 nm), but is totally negligible when compared to the imaging wavelength, even in rather wet conditions (20 mm of total integrated column of water); (3) tight errors budget, with WFS in the VIS and correction in the NIR domain, is the only case where chromatic error might become an issue, as with extreme AO systems. The power spectrum model presented here can be used to evaluate the chromatic correction error and its contribution to the long exposure PSF, using the spatial frequency approach.

Suppressing stellar residual light on extremely large telescopes by aperture modulation
Conférence ArODES

Szymon Gladysz, Erez Ribak, Bruno Femenia Castella, Laurent Jolissaint, Patrice Martinez

Proceedings of the 1st AO4ELT conference

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Résumé:

Efficient suppression of the residual stellar light is paramount to the success of exoplanet imaging efforts. We present a new approach to diffraction suppression on extremely large telescopes. The method is based on the realization that by obscuring part of the wavefront in the Lyot stop we can change the shape of the corresponding PSF. This obscuration is then modulated leading to modulated Airy pattern, while image of a planet - if present - is only slightly affected. The modulation could then be removed from the set of images, leading to better SNR of the possible planets. Simulation of the European Extremely Large Telescope has been used to test this approach.

The software package PAOLAC :
Conférence ArODES
an embedment of the analytical code PAOLA within the CAOS problem-solving environment

Marcel Carbillet, Laurent Jolissaint, Anne-Lise Maire

Proceedings of the 1st AO4ELT conference

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Résumé:

We present the Software Package PAOLAC (“PAOLA within Caos”) in its first distributed version. This new numerical simulation tool is an embedment of the analytical adaptive optics simulation code PAOLA (“Performance of Adaptive Optics for Large (or Little) Apertures”) within the CAOS problem-solving environment. The main goal of this new tool is to allow an easier and direct comparison between studies performed with the analytical open-loop code PAOLA and studies performed with the end-to-end closed-loop Software Package CAOS (“Code for Adaptive Optics Systems”), with the final scope of better understanding how to take advantage from the two approaches: one analytical allowing extremely quick results on a wide range of cases and the other extremely detailed but with a computational and memory costs which can be impressive. The practical implementation of this embedment is briefly described, showing how this absolutely does not affect any aspect of the original code which is simply directly called from the CAOS global graphical interface through ad hoc modules. A comparison between end-to-end modelling and analytical modelling is hence also initiated, within the specific framework of wide-field adaptive optics at Dome C, Antarctica.

Use of AO PSF models for the study of resolved stellar populations
Conférence ArODES

A. Deep, G. Fiorentino, Laurent Jolissaint, E. Tolstoy

Proceedings of the 1st AO4ELT conference

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Résumé:

The full scientific exploitation of AO images to study resolved stellar populations is still in a nascent stage. This requires pushing to the faint limits and carrying out deep and accurate crowded field photometry and astrometry. The main complexity of AO images is that the correction is never perfect and the PSF always has a complex residual halo around the central core which contains a large fraction of the light. The variations in seeing over short periods of time and anisoplanatism effects create strongly time dependent effects in the PSF. The aim of this study is primarily to test the ability of current photometric packages to be able to cope with a AO PSFs in a number of straightforward but scientifically important examples.

Extreme adaptive optics in the mid-IR :
Conférence ArODES
the METIS AO system

R. Stuik, Laurent Jolissaint, S. Kendrew, S. Hippler, B. Brandl

Proceedings of the 1st AO4ELT conference

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Résumé:

Adaptive Optics at mid-IR wavelengths has long been seen as either not necessary or easy. The impact of atmospheric turbulence on the performance of 8-10 meter class telescopes in the mid-IR is relatively small compared to other performance issues like sky background and telescope emission. Using a relatively low order AO system, Strehl Ratios of larger than 95% have been reported on 6-8 meter class telescopes. Going to 30-42 meter class telescopes changes this picture dramatically. High Strehl Ratios require what is currently considered a high-order AO system. Furthermore, even with a moderate AO system, first order simulations show that the performance of such a system drops significantly when not taking into account refractivity effects and atmospheric composition variations. Reaching Strehl Ratios of over 90% at L, M and N band will require special considerations and will impact the system design and control scheme of AO systems for mid-IR on ELTs. In this paper we present an overview of the effects that impact the performance of an AO system at mid-IR wavelengths on an ELT and simulations on the performance and we will present a first order system concept of such an AO system for METIS, the mid-IR instrument for the E-ELT.

Characterization of exoplanets and protoplanetary disks with the proposed E-ELT Instrument METIS
Conférence ArODES

Stefan Hippler, Wolfgang Brandner, Thomas Henning, Bernhard R. Brandl, Joris Blommaert, Laurent Jolissaint

Exoplanets and disks : their formation and diversity : proceedings of the International Conference

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Résumé:

METIS (the Mid‐infrared E‐ELT Imager and Spectrograph) is a 3‐ to 14‐micron multimode instrument for the 42‐meter European Extremely Large Telescope (E‐ELT). The instrument modes currently under study include direct and coronagraphic imaging, long‐slit spectroscopy, integral field spectroscopy and polarimetry. METIS will be interfaced with the E‐ELT adaptive optics system, and incorporate its own on‐axis natural guide star wavefront sensor, and thus achieve Strehl ratios above 90% in N band. In this paper we will describe two of the main science goals of this instrument: direct imaging of exoplanets as well as the characterization of protoplanetary disks. Because of the superior angular resolution and high contrast, METIS at the E‐ELT will be able to image exoplanets at considerably closer orbits than its cooperative competitor the Mid‐infrared Instrument (MIRI) on the James Webb Space Telescope (JWST).

2008

ASSIST :
Conférence ArODES
the test setup for the VLT AO facility

Remko Stuik, Atul Deep, Robin Arsenault, Ralf Conzelmann, Bernard Delabre, Laurent Jolissaint

Adaptive Optics Systems

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Résumé:

ASSIST: The Adaptive Secondary Setup and Instrument STimulator is the test setup for the verification and calibration of three elements of the VLT Adaptive Optics Facility.; the Deformable Secondary Mirror (DSM) the AO system for MUSE and HAWK-I (GALACSI and GRAAL). In the DSM testing mode the DSM will be tested using both interferometry and fast wave front sensing. In full AO mode, ASSIST will allow testing of the AO systems under realistic atmospheric conditions and optically equivalent to the conditions on the telescope. ASSIST is nearing its final design review and in this paper we present the current optical and mechanical design of ASSIST. In this paper we highlight some of the specific aspects of ASSIST that we are developing for ASSIST.

Exploring the impact of PSF reconstruction errors on the reduction of astronomical adaptive optics based data
Conférence ArODES

Laurent Jolissaint, Hervé Carfantan, Eric Anterrieu

Adaptive Optics Systems

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Résumé:

Astronomical adaptive optics (AO) data analysis requires the knowledge of the PSF associated to the AO run. With new AO modes soon to become available (LTAO, GLAO) there is a request from the AO users community for the development of new PSF reconstruction algorithms. Question is: what is the required accuracy on the quality of the reconstruction ? Guide-lines are needed in order to check the validity/usefulness of a given PSF reconstruction approach. LTAO/GLAO PSF reconstruction algorithms are being studied but are not available yet, so we propose to analyze this issue by simulating AO data with an AO modeling tool, and doing the data reduction using modeled AO PSF with an increased level of difference with the initial AO PSF, for parameters that have potentially a large impact on the PSF structure: the seeing angle, the C2N vertical distribution, the residual tip-tilt, LGS altitude fluctuations, and off-axis PSF variation (anisoplanatic effects). Results are given in the context of data analysis of an LTAO mode mimicking the planned VLT/GALACSI system. We do not take into account any instrument mode, and the telescope is assumed without aberrations. The current study is focused on the most critical type of data reduction: deconvolution. Algorithms are reviewed, and it is shown that for most classical deconvolution methods, the main impact of PSF reconstruction errors can already be described using either the so-called residual filter (ratio of exact OTF over reconstructed OTF) or more simply the difference between the exact and the reconstructed PSF. Using these two metrics, we explore the consequences of uncertainties on the five parameters introduced above. It is found that (1) in general, the impact of PSF reconstruction errors, while noticeable, appears to be surprisingly low, relaxing apparently the need for highly sophisticated PSF reconstruction algorithms; (2) in the case of Winer-like deconvolution, tip-tilt uncertainty is the most critical parameter, and has a noticeable impact on the residual PSF wings - which can be a problem when looking for faints objects in the vicinity of a bright star; (3) in the case of source extraction (CLEAN-like algorithms), seeing error clearly dominates, and the other errors have basically the same impact; (4) the impact of numerical effects during PSF deconvolution or extraction (sub-pixel PSF positioning error) is of the same order of magnitude than the effect of AO PSF parameters uncertainties.

METIS :
Conférence ArODES
the Mid-infrared E-ELT Imager and Spectrograph

Bernhard R. Brandl, Rainer Lenzen, Eric Pantin, Alistair Glasse, Joris Blommaert, Laurent Jolissaint

Ground-based and Airborne Instrumentation for Astronomy II

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Résumé:

METIS, the Mid-infrared ELT Imager and Spectrograph (formerly called MIDIR), is a proposed instrument for the European Extremely Large Telescope (E-ELT), currently undergoing a phase-A study. The study is carried out within the framework of the ESO-sponsored E-ELT instrumentation studies. METIS will be designed to cover the E-ELT science needs at wavelengths longward of 3μm, where the thermal background requires different operating schemes. In this paper we discuss the main science drivers from which the instrument baseline has been derived. Specific emphasis has been given to observations that require very high spatial and spectral resolution, which can only be achieved with a ground-based ELT. We also discuss the challenging aspects of background suppression techniques, adaptive optics in the mid-IR, and telescope site considerations. The METIS instrument baseline includes imaging and spectroscopy at the atmospheric L, M, and N bands with a possible extension to Q band imaging. Both coronagraphy and polarimetry are also being considered. However, we note that the concept is still not yet fully consolidated. The METIS studies are being performed by an international consortium with institutes from the Netherlands, Germany, France, United Kingdom, and Belgium.

Atmospheric refractivity effects on mid-infrared ELT adaptive optics
Conférence ArODES

Sarah Kendrew, Laurent Jolissaint, Richard J. Mathar, Remko Stuik, Stefan Hippler

Adaptive Optics Systems

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Résumé:

We discuss the effect of atmospheric dispersion on the performance of a mid-infrared adaptive optics assisted instrument on an extremely large telescope (ELT). Dispersion and atmospheric chromaticity is generally considered to be negligible in this wavelength regime. It is shown here, however, that with the much-reduced diffraction limit size on an ELT and the need for diffraction-limited performance, refractivity phenomena should be carefully considered in the design and operation of such an instrument. We include an overview of the theory of refractivity, and the influence of infrared resonances caused by the presence of water vapour and other constituents in the atmosphere. 'Traditional' atmospheric dispersion is likely to cause a loss of Strehl only at the shortest wavelengths (L-band). A more likely source of error is the difference in wavelengths at which the wavefront is sensed and corrected, leading to pointing offsets between wavefront sensor and science instrument that evolve with time over a long exposure. Infrared radiation is also subject to additional turbulence caused by the presence of water vapour in the atmosphere not seen by visible wavefront sensors, whose effect is poorly understood. We make use of information obtained at radio wavelengths to make a first-order estimate of its effect on the performance of a mid-IR ground-based instrument. The calculations in this paper are performed using parameters from two different sites, one 'standard good site' and one 'high and dry site' to illustrate the importance of the choice of site for an ELT.

2007

ASSIST :
Conférence ArODES
development of a test-infrastructure for the VLT AO facility

Remko Stuik, Robin Arsenault, Atul Deep, Bernard Delabre, Pascal Hallibert, Laurent Jolissaint

Astronomical Adaptive Optics Systems and Applications III

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Résumé:

ASSIST - The Adaptive Secondary Setup and Instrument STimulator is a test setup to verify the operation of three elements of the VLT Adaptive Optics Facility, namely the Deformable Secondary Mirror (DSM) and the two AO systems using this DSM, the AO system for the visible light integral field spectrograph MUSE (GALACSI) and the AO system for the IR wide field imager HAWK-I (GRAAL). To support the testing of these elements, ASSIST will provide both an interferometry setup for testing the DSM as well as a full atmospheric turbulence simulator and star simulator to mimic the conditions at the telescope. To test the instruments using the DSM, the output beam is matched the output beam of the VLT telescope, including the correct exit-pupil and high-quality imaging and a similar hardware interface is provided. Since one of the modes to be verified is nearly diffraction limited, also the thermal and vibrational stability are very important, with strong constraints on both the mechanical as well as the optical design.

2006

Analytical modeling of the optical transfer function of a segmented telescope with/without adaptive optics correction of the telescope's dynamical aberrations
Conférence ArODES

Laurent Jolissaint, Brent Ellerbroek, George Angeli

Modeling, Systems Engineering, and Project Management for Astronomy II

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Résumé:

An all-analytic optical transfer function (OTF) tool for characterizing the performance of a large segmented telescope with/without adaptive optics (AO) correction of the telescope dynamical aberrations is presented. This tool is to be applied to the determination of the Thirty Meter Telescope (TMT) optical budget error, for both telescope aberrations and AO systems specifications. It takes into account the effect of the dynamical aberrations of all optical surfaces from all the hexagonal segments to the tertiary mirror, and includes as an option AO correction of these errors. Here we present the mathematical development of the method, and give an example of application to a 73 segments 10-m telescope, without AO correction.

The MOAO system of the IRMOS near-infrared multi-object spectrograph for TMT
Conférence ArODES

David R. Andersen, Stephen S. Eikenberry, Murray Fletcher, William Gardhouse, Brian Leckie, Jean-Pierre Véran, Laurent Jolissaint

Ground-based and Airborne Instrumentation for Astronomy

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Résumé:

The near-Infrared Multi-Object Spectrograph (IRMOS) for TMT is one of the most powerful astronomical instruments ever envisioned. The combination of the collecting area of TMT, the unique image-sharpening capabilities of the Multi-Object Adaptive Optics (MOAO) system, and the multiplexing advantage of the multi-object integral-field spectra provided by the IRMOS back-end make it capable of addressing some of the leading scientific challenges of the coming decades. Here we present an overview of one potential IRMOS concept and then focus on the MOAO system. In particular we will describe our concept for the laser and natural guide star wavefront sensors, deformable mirrors and the calibration system of MOAO. For each of these design elements, we describe the key trade studies which help define each subsystem. From results of our studies, we assemble a MOAO ensquared energy budget. We find that 50% of the energy is ensquared within the 50 milli-arcsecond spatial pixel of the IRMOS integral field units for a wavelength of 1.65μm. Given the requirements placed on the MOAO system to achieve this performance, large ensquared energies can be achieved with even finer plate scales for wavelengths longer than 1.5μm.

2005

Speckle statistics in direct and coronagraphic imaging
Conférence ArODES

Rémi Soummer, Claude Aime, André Ferrari, Anand Sivaramakrishnan, Laurent Jolissaint

Proceedings of the International Astronomical Union

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Résumé:

In this communication, we study the statistical properties of the light intensity in direct and coronagraphic images, in the context of ground-based Extreme Adaptive Optics observations. The same approach can also be used for space observations with different scales. We show that a coronagraph only affects the perfect part of the wave and leaves the uncorrected part of the wavefront almost unaffected. This statistical model can explain the ‘speckle pinning’ effect (presence of speckles at the position of the diffraction rings), as an amplification of the speckle noise. This statistical approach can be verified on real adaptive optics data.

2004

Multiple-layer optical turbulence generator principle and SLODAR characterization :
Conférence ArODES
preliminary results

Laurent Jolissaint, Onur Keskin, Colin Bradley, Brian Wallace, Aaron Hilton

Optics in Atmospheric Propagation and Adaptive Systems VII

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Résumé:

We present in this paper the status and preliminary results of an experiment to create a calibrated profile of turbulent layers, both in position and strength, using a calibrated hot air turbulence generator (turbulator), in so-called multi-pass mode. Cn2 profile is retrieved using the SLODAR technique. First results, with only one layer, show the validity of our approach, and give us confidence that a multiple pass scheme is doable and measurable with a few modifications of the current set-up.

An analytic model for the study of the impact of mirror segmentation on AO performance and application to a 30-m segmented telescope
Conférence ArODES

Laurent Jolissaint, Jean-Francois Lavigne

Modeling and Systems Engineering for Astronomy

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Résumé:

Primary mirrors of the next generation of extremely large telescopes will be highly segmented. Since these telescopes will be equipped with adaptive optics (AO), it is very important to examine in details what are the consequences of different segmentation schemes on the delivered image quality after AO correction. We do so using our analytical AO simulation code PAOLA {Performance of Adaptive Optics for Large (or Little) Apertures}, upgraded to include AO correction of the primary mirror static aberrations. This study allows us to derive requirements on the geometry of the primary mirror, and the maximum acceptable segments positioning and figuring errors knowing that part of their amplitude will be corrected by the AO system offset. The first important issue is the influence of the segments size and gap width. These parameters have indeed a strong impact on the structure of the wings of the diffraction limited point spread function (PSF), but on the other hand, with the smooth AO residual halo superimposed onto it, the relative importance of the wing structures is decreased. To assess these effects, we consider the case of an AO system working in a near infrared classical mode on a 30-m segmented telescope and examine how the encircled energy radius and image contrast evolve with segment size and gap width. The second important issue is the effect of residual segment positioning & figuring errors after active optics and AO correction. Using appropriate metrics, we characterise the maximum acceptable segment positioning & figuring errors residuals in a classical AO mode, for one of the pupils studied in the first part of our work.

Evaluation of the on-sky performance of Altair
Conférence ArODES

Jeff A. Stoesz, Jean-Pierre Véran, Francois Rigaut, Glen Herriot, Laurent Jolissaint

Advancements in Adaptive Optics

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Résumé:

In this paper we evaluate the on-sky performance of Altair, the facility adaptive optics instrument at the Gemini North telescope. We describe the method for doing this on-sky evaluation, which includes: 1) the choice of suitable stellar fields for PSF observations that must cover a range of guide star magnitudes and angular separations from the guide star; 2) the observation strategy and data reduction pipeline; and 3) the PSF database from which the performance results are queried. The database stores observatory system parameters and performance observations such as FWHM, Strehl, encircled energy, wave front sensor flux, as well as coherence length (ro) and outer scale (Lo) of the turbulence measured in closed loop and therefore coincident with the focal plane observations of the telescope. From the database we derive 20 to 24% Noll efficiency of the system and an estimated distribution of effective turbulence height above the summit to be 3.3 ± 0.6km. The performance evaluation strategy used on Altair is quite general and could be used for other adaptive optics systems.

Ground-layer adaptive optics performance in Antarctica
Conférence ArODES

T. Travouillon, J.S. Lawrence, Laurent Jolissaint

Advancements in Adaptive Optics

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Résumé:

Ground layer Adaptive Optics (GLAO) is a new variant of adaptive optics that aims at correcting the seeing over a wide field of view by conjugating the deformable mirror to the boundary layer altitude.The South Pole is expected to be particularly to GLAO due to the absence of high altitude jets and the confinement of 96% of the seeing within a 220 m boundary layer. We present here the comparison of a GLAO system on a 2 m class infrared telescope at the South Pole and at Paranal. Our results, which show that the two sites obtain similar performance, are derived analytically using the simulation tool PAOLA (Performance of Adaptive Optics for Large Apertures).

OPERA, an automatic PSF reconstruction software for Shack-Hartmann AO systems :
Conférence ArODES
application to Altair

Laurent Jolissaint, Jean-Pierre Véran, José Marino

Advancements in Adaptive Optics

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Résumé:

When doing high angular resolution imaging with adaptive optics (AO), it is of crucial importance to have an accurate knowledge of the point spread function associated with each observation. Applications are numerous: image contrast enhancement by deconvolution, improved photometry and astrometry, as well as real time AO performance evaluation. In this paper, we present our work on automatic PSF reconstruction based on control loop data, acquired simultaneously with the observation. This problem has already been solved for curvature AO systems. To adapt this method to another type of WFS, a specific analytical noise propagation model must be established. For the Shack-Hartmann WFS, we are able to derive a very accurate estimate of the noise on each slope measurement, based on the covariances of the WFS CCD pixel values in the corresponding sub-aperture. These covariances can be either derived off-line from telemetry data, or calculated by the AO computer during the acquisition. We present improved methods to determine 1) r0 from the DM drive commands, which includes an estimation of the outer scale L0 2) the contribution of the high spatial frequency component of the turbulent phase, which is not corrected by the AO system and is scaled by r0. This new method has been implemented in an IDL-based software called OPERA (Performance of Adaptive Optics). We have tested OPERA on Altair, the recently commissioned Gemini-North AO system, and present our preliminary results. We also summarize the AO data required to run OPERA on any other AO system.

Predicting the aerodynamic performance of the Canadian Very Large Optical Telescope
Conférence ArODES

Joeleff Fitzsimmons, Jennifer Dunn, Glen Herriot, Laurent Jolissaint, Scott Roberts

Modeling and Systems Engineering for Astronomy

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Résumé:

A variety of aerodynamic studies have been completed to assist in the development of an integrated model for the Thirty Meter Telescope. These studies investigated the characteristics of wind loading on the Canadian Very Large Optical Telescope (VLOT) and produced preliminary data for input into the VLOT integrated model. We describe the details of, and present the results from, the computational fluid dynamic (CFD) analyses and wind tunnel (WT) tests. The validity of the CFD results is assessed through correlation studies that compare the CFD and WT results. Through extensive comparison of the mean and RMS coefficients of pressure and the power spectral density plots of the pressures within the enclosure, excellent correlations between the experimental and computational results are shown.

An analytic model for natural guide star wide-field adaptive optics
Conférence ArODES

Jeff A. Stoesz, Laurent Jolissaint, Jean-Pierre Véran, Jeff LeDue

Advancements in Adaptive Optics

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Résumé:

Wide-Field Adaptive Optics (WFAO) is an AO mode in which one deformable mirror is used to achieve modest adaptive optics correction of the atmospheric turbulence, but in a much wider field of view than classical AO. At the heart of the concept is the desire to trade image quality at the center of the field of view for better image quality at the edge of a wide field (typically ~10') and is also called Improved Seeing AO (ISAO) or Ground Layer AO (GLAO) in the literature. An analytical (Fourier domain) model allows us to rapidly derive requirements on the number, brightness and distribution of guide stars for a WFAO system running on an 8-m or 30-m telescope, as well as basic AO system requirements such as loop rate and DM actuator density. In this paper we derive the Fourier domain filter that describes WFAO and present a method for evaluating WFAO performance and sky coverage. We test our performance evaluation on a pathological case, computing the scientifically relevant metric, radius of 50\% encircled energy for a typical Cn2 profile.

2003

Adaptive optics and site requirements for the search of Earth-like planets with ELTs
Conférence ArODES

O. Lardière, P Salinari, Laurent Jolissaint, M. Carbillet, A. Riccardi

Proceedings of the Second Backaskog Workshop on Extremely Large Telescopes

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Résumé:

Since 1995, expolanets discoveries have triggered a renewal of the permanent question about the possible presence of life outside the solar system. Direct detection and characterization of earth-like extrasolar planets orbiting main-sequence stars are now among the most exciting and challenging astronomical topics where new major scientific results from space missions and also from ground-based ELT are expected. To scale the performances of an ELT for exoplanets searching, we examine the relative impact of three fundamental parameters (the actuator pitch, the telescope diameter and the site) on the image contrast. Then, we calculate the planet/star flux ratio needed to reach SNR=3 in 10h (only the photon noise is considered) from long-exposure AO-PSF computed with PAOLA (a fast analytical code developed by one of us: L.J.) for different ELT sizes and AO parameters under different observational conditions (atmospheric turbulenece, star magnitude) with or without coronagraphy. We find that an actuator pitch of 0.1 m is optimal for exoplanet searching in the visible and near-IR from 10 to 40 pc. Lastly, we emphasize that the site choice is as important as the telescope size choice is: a 15m telescope is just enough for coronagraphic search for exo-earths at 10pc (SNR=3 in 10h) from the promising Dome C (Antarctica), while a 30m ELT is needed to succeed the same observation in the same time from the Mauna Kea.

Aerodynamic modeling of the Canadian Very Large Optical Telescope
Conférence ArODES

Joeleff Fitzsimmons, Glen Herriot, Laurent Jolissaint, Scott Roberts, Kevin Cooper

Second Backaskog Workshop on Extremely Large Telescopes

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Résumé:

A variety of aerodynamic studies are ongoing to assist in the development of an integrated model for the Canadian Very Large Optical Telescope (VLOT). The purpose of these studies is to investigate the characteristics of wind loading on VLOT and to produce preliminary data for input into the VLOT integrated model. We describe these various aerodynamic studies, which include analytical and statistical approximations, computational fluid dynamics analyses and wind tunnel testing. Next, we present the methods developed for coupling the wind loads into the structural dynamics module within the VLOT integrated model. Preliminary results from the computational fluid dynamics and wind tunnel studies are presented. Finally, the future plans for expanded studies and characterization of primary mirror seeing and dome seeing are outlined.

Wide field adaptive optics upper limit performances
Conférence ArODES

Laurent Jolissaint, Jean-Pierre Véran, Jeffrey A. Stoesz

Second Backaskog Workshop on Extremely Large Telescopes

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Résumé:

Wide Field Adaptive Optics (WFAO) is a new proposed astronomical adaptive optics mode allowing a significant improvement of the seeing limited point spread function characteristics over large fields -- several arc minutes in diameter, using only one deformable mirror optically conjugated to an optimal altitude. In this paper, we present the WFAO upper limit performances, based on the assumption that the refractive index fluctuation field above the telescope is perfectly known. Our results are based on analytical developments for the residual phase power spectrum after WFAO correction, implemented in PAOLA, an analytical AO simulation tool, developed at the Herzberg Institute of Astrophysics. Results are presented for several sites: Mauna Kea, Cerro Tololo, Cerro Paranal. For each of these locations, we give the WFAO-PSF properties as a function of the field angle, the conjugation altitude of the deformable mirror, the imaging infrared wavelength, and the cone aperture angle over which the tomographic information is averaged to drive the deformable mirror actuators.

Dual conjugate adaptive optics testbed :
Conférence ArODES
progress report

Brian Wallace, Colin Bradley, Harvey Richardson, Jeff Kennedy, Onur Keskin, Laurent Jolissaint

Astronomical Adaptive Optics Systems and Applications

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Résumé:

In this paper, we describe the progress of the construction of the Multi-Conjugate Adaptive Optics laboratory test-bed at the University of Victoria, Canada. The test-bench will be used to support research in the performance of multi-conjugate adaptive optics, turbulence simulators, laser guide stars and miniaturizing adaptive optics. The main components of the test-bed include two micro-machined deformable mirrors, a tip-tilt mirror, four wavefront sensors, a source simulator, a dual-layer turbulence simulator, as well as computational and control hardware. The paper describes changes in the opto-mechanical design, characteristics of the hot-air turbulence generator, performance achievements with the tip-tilt and MEMS deformable mirrors as well as the design and performance of the wavefront sensors and control software.

Hot-air turbulence generator for multiconjugate adaptive optics
Conférence ArODES

Onur Keskin, Laurent Jolissaint, Colin Bradley, Sadik Dost, Inna Sharf

Advanced Wavefront Control: Methods, Devices, and Applications

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Résumé:

In this article, a simple low-cost, statistically repeatable, hot air optical turbulence generator based on the mixing of two air flows with different temperatures is described. Characterization results show that it is possible to create any turbulence strength up to CN2Δh ≈ 6 x 10-10 m1/3, allowing Fried's parameter as small as r0 ≈ 1.7 mm for one crossing through the turbulator or r0 ≈ 1.1 mm for two crossings. Outer scale of (L0 ≈ 133 ± 60 mm) is found to be compatible to the turbulator chamber size (170 mm), and inner scale (l0 ≈ 7.6 mm ± 3.8 mm) compatible with usual values measured by other authors for the free atmosphere. Power spectrum analysis of the centroid of the focused image shows a perfect and accurate agreement with Kolmogorov's theory, allowing to conclude that this device can be used with confidence to emulate good and easily controllable turbulence. In particular, this turbulator will be used with the MCAO test bench developed at the University of Victoria. By allowing two passes of the optical beam through the turbulator, without overlapping, two independent turbulent layers, set at equivalent altitudes of 5 and 15 km above the telescope entrance pupil, will be generated.

2001

Design of the dual conjugate adaptive optics test-bed
Conférence ArODES

Inna Sharf, K. Bell, D. Crampton, J. Fitzsimmons, Glen Herriot, Laurent Jolissaint

Proceedings of the 2002 ESO Conference and Workshop

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Résumé:

In this paper, we describe the Multi-Conjugate Adaptive Optics laboratory test-bed presently under construction at the University of Victoria, Canada. The test-bench will be used to support research in the performance of multi-conjugate adaptive optics, turbulence simulators, laser guide stars and miniaturizing adaptive optics. The main components of the test-bed include two micro-machined deformable mirrors, a tip-tilt mirror, four wavefront sensors, a source simulator, a dual-layer turbulence simulator, as well as computational and control hardware. The paper will describe in detail the opto-mechanical design of the adaptive optics module, the design of the hot-air turbulence generator and the configuration chosen for the source simulator.

Fast computation and morphologic interpretation of the Adaptive optics point spread function
Conférence ArODES

Laurent Jolissaint, Jean-Pierre Véran

Proceedings of the 2002 ESO Conference and Workshop

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Résumé:

We reconsider here the long exposure AO PSF computation based on a analytical derivation of the spatial power spectrum of the residual phase (Rigaut et al. 1998), and applied it to the case of giant telescopes with or without MCAO. This approach is proven to be faster in computation time than any other Monte-Carlo ones, for a high level of accuracy. With the addition of an interpretation of the AO PSF wings in term of the residual phase angular power spectrum, we show that both approachs, the analytical and the angular interpretation, lead to a powerful tool for assessing the effect of the different parts of the spectrum on the different parts of the AO PSF. Using this tool, we present some examples of the relationship between the spectrum and the PSF wings, for the atmospheric, noise, aliasing and anisoplanatism components, and show that the effects of the residual phase is more critical for a giant than for a modest size telescope, for which these effects are hidden by the diffraction structures.

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