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[THESE] Commande haute performance pour l'optique adaptative du Gran Telescopio Canarias– Thèses et Post-Doc

30 janvier 2019

Description du poste :

GTCAO_control_PhD_subject (PDF / 126,50 kB)

High-performance adaptive optics control for the Gran Telescopio Canarias

GENERAL CONTEXT

The Gran Telescopio Canarias (GTC), is a 10.4 m diameter telescope with a segmented primary mirror. It is located in one of the top astronomical sites in the Northern Hemisphere: the Observatorio del Roque de los Muchachos (ORM, La Palma, Canary Islands). The GTC is a Spanish initiative led by the Instituto de Astrofísica de Canarias (IAC). GTC is supported by the Spanish Government and the Local Government from the Canary Islands through the European Funds for Regional Development (FEDER) provided by the European Union. Support also includes the participation of Mexico (Instituto de Astronomía de la Universidad Nacional Autónoma de México (IA-UNAM) and Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE)), and the US University of Florida.

Being the largest telescope in the world and thanks to its location at the ORM, GTC will allow the study of key questions in astrophysics such as the nature of black holes, the formation history of stars and galaxies in the early universe, the physics of distant planets around other stars, and the nature of dark matter and dark energy in the universe.

ADAPTIVE OPTICS SYSTEM OF GTC

GTC was designed to provide diffraction limited observations in the near infrared. Since the beginning, the development of an Adaptive Optics system for GTC (GTCAO) was considered necessary to provide high order correction in the near infrared, to maximize image quality. AO systems aim at recovering diffraction-limited images thanks to a real-time compensation of optical aberrations caused by atmospheric turbulence or other sources of aberrations like small tracking errors, structure vibrations due to wind or components such as pumps, fans, etc.

The GTCAO system [1][2] designed and developed during the last years is based on a single deformable mirror conjugated to the telescope pupil, with 21 actuators across the GTC pupil. The wavefront sensor is a Shack-Hartmann sensor, with 20 x 20 subapertures, that uses an OCAM2 camera. In GTCAO it is planned to correct wavefront tip-tilt with the lightweight secondary mirror of the telescope, the drive system of which is capable of fast chopping and tip-tilt correction. Residual high temporal frequencies of the tip-tilt will be corrected by the deformable mirror.

GTCAO has been designed to provide a corrected beam with a Strehl Ratio (SR) of 0.65 in K-band with bright natural guide stars.

The baseline regulator of the GTCAO system is a linear regulator (auto-regressive moving average filter structure) for tip and tilt modes combined with a leaky proportional-integral (PI) controller for high-order modes. Several parameterizations are envisioned for operating the system, depending on turbulence conditions. Parameter tuning is planned to be based on stability margins and rejection bandwidth of the closed loop.

HIGH-PERFORMANCE CONTROL WITH THE ADAPTIVE OPTICS TEAM AT LABORATOIRE CHARLES FABRY

The AO team at Laboratoire Charles Fabry (LCF) (Institut d’Optique Graduate School (IOGS)-CNRS, Palaiseau, France) is renowned for its expertise in optimal AO control [3][4][5][6]. Other recent works worldwide also show that optimal control is an appealing strategy for on-sky operation [7][8][9]. The design of such high-performance regulators for GTCAO is thus a direction to be explored in order to evaluate their potential. These regulators rely on a fine modelling of the perturbation, including possible structure vibrations, windshake, dome turbulence, etc. The model is then used to build a Kalman filter, which predicts the perturbation (to compensate for loop delay) and which is at the heart of the regulator.

HIGH-PERFORMANCE CONTROL FOR GTCAO

The PhD student will have to interact closely with the GTCAO team to get a deep understanding of the AO system and its requirements, of the observing conditions and perturbation types, in a nutshell of all specificities of the GTCAO system that need to be accounted for in the model used to design the regulator. Also, as models rely on parameters (physical or not), they need to be regularly updated according to evolution of disturbance statistics. The identification strategy also plays an important role in control performance and has thus to be considered altogether with control design.

Simulations will be conducted on the DASP+DARC platform, developed by University of Durham, and that is used and further developed for GTCAO by the GTCAO team. This platform integrates the same Real-Time Controller (RTC) than the one used on the real system. If the real-time structure of the RTC regulator needs to be modified to test new solutions, this will be done in close interaction also with the University of Durham, who will supervise the RTC modifications. Once solutions are validated on the platform, the selected regulators can be directly integrated on the bench itself.

BENCH AND ON-SKY TESTING WITH THE IAC IN THE CANARY ISLANDS

After an extensive study in simulation, selected regulators will be tested on the GTCAO bench. These tests will be conducted with the GTCAO team on site. The PhD student will thus have to spend some time at IAC under the supervision of the GTCAO team. If successful, these tests will be followed by on-sky testing at GTC in La Palma, in order to evaluate the potential of the new regulators in real-life environment.

APPLICATION

An international co-tutelle with Spain is being investigating but not yet validated. In the case of a co-tutelle, the PhD student will have to spend about 1 year in the Canary Islands.

The candidate must hold a master’s degree (master, engineering school) that includes strong skills in instrumentation for astronomy and some skills in control theory. The candidate should be strongly interested and challenged by the applicative aspects, from simulation to implementation on an operational system, and by the collaborative work with the different teams.

The candidate should apply by contacting the PhD director and co-supervisors, and through the ADUM website http://adum.fr. The deadline is May, 12, 2019.

Additional information can be obtained by contacting the thesis director and co-supervisors:

Caroline Kulcsár, thesis director (LCF-IOGS) Caroline.kulcsar@institutoptique.fr

Henri-François Raynaud (LCF-IOGS) Henri-francois.raynaud@institutoptique.fr

Icíar Montilla (IAC) imontilla@iac.es

PHD GRANT

This subject is submitted to the Doctoral School of Université Paris Saclay (France) for possible funding. The salary is 1 758 € including taxes, which corresponds approximately to 1 400 € free of tax.

REFERENCES

[1] Cagigal, M. Núñez, Ramosa, LF Rodríguez, Araujoa, O. Tubio, et al. Feedback control baseline for GTC adaptive optics with NGS. AO4ELT5, 2017.

[2] De la Rosa, J. Marco, et al. GTCAO Real Time Control System software design. AO4ELT5, 2017.

[3] Le Roux, Brice, Conan, Jean-Marc, Kulcsár, Caroline, et al. Optimal control law for classical and multiconjugate adaptive optics. JOSA A, 2004, vol. 21, no 7, p. 1261-1276.

[4] Kulcsár, Caroline, Raynaud, Henri-François, Petit, Cyril, et al. Minimum variance prediction and control for adaptive optics. Automatica, 2012, vol. 48, no 9, p. 1939-1954.

[5] Sivo, Gaetano, Kulcsár, Caroline, Conan, Jean-Marc, et al. First on-sky SCAO validation of full LQG control with vibration mitigation on the CANARY pathfinder. Optics express, 2014, vol. 22, no 19, p. 23565-23591.

[6] Sivo, Gaetano, Juvénal, Rémy, Kulcsár, Caroline, et al. Real-time implementation of an LQG tip-tilt controller for regular science observation on GeMS. SPIE, 2016. p. 99094Y.

[7] Petit, C., Sauvage, J.-F., Fusco, T., et al. Sphere eXtreme AO control scheme: final performance assessment and on sky validation of the first auto-tuned LQG based operational system. SPIE, 2014. p. 91480O.

[8] Poyneer, Lisa A., De Rosa, Robert J., Macintosh, Bruce, et al. On-sky performance during verification and commissioning of the Gemini Planet Imager's adaptive optics system. SPIE, 2014. p. 91480K.

[9] Wang, Lianqi, Gilles, Luc, Ellerbroek, Brent, et al. Physical optics modeling of sky coverage for TMT NFIRAOS with advanced LQG controller. SPIE, 2014. p. 91482J.

Equipe | Service :

Laboratoire Charles Fabry, équipe Optique adaptative du groupe Imagerie et information

Localisation :

Laboratoire Charles Fabry (Palaiseau, France) avec des missions potentiellement longues (1 an maximum en tout) aux Îles Canaries (Espagne) dans l'équipe de l'Instituto de Astrofisica de Canarias

Profil recherché :

Master/école d'ingénieur en optique, avec des connaissances en instrumentation et en automatique. Un goût pour le traitement de données réelles, les aspects physiques des systèmes et le travail en collaboration est indispensable.

Date de début :

1 octobre 2019

Durée :

3 ans

Financement :

Financement demandé : MESR (Ecole doctorale EOBE de l'Université Paris Saclay)

La date limite de candidature est le 12 mai 2019.

Candidature en contactant les encadrants et sur le site ADUM : http://adum.fr

Contacts :

Thesis director

Caroline Kulcsár (LCF-IOGS) Caroline.kulcsar@institutoptique.fr

Co-supervisors

Henri-François Raynaud (LCF-IOGS) Henri-francois.raynaud@institutoptique.fr

Icíar Montilla (IAC) imontilla@iac.es

Contact

Nathalie  Baudry
Gestionnaire Ressources Humaines
Tél 01 64 53 33 01

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