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Proceedings Paper

SPHERE eXtreme AO control scheme: final performance assessment and on sky validation of the first auto-tuned LQG based operational system
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Paper Abstract

The SPHERE (Spectro-Polarimetry High-contrast Exoplanet Research) instrument is an ESO project aiming at the direct detection of extra-solar planets. SPHERE has been successfully integrated and tested in Europe end 2013 and has been re-integrated at Paranal in Chile early 2014 for a first light at the beginning of May. The heart of the SPHERE instrument is its eXtreme Adaptive Optics (XAO) SAXO (SPHERE AO for eXoplanet Observation) subsystem that provides extremely high correction of turbulence and very accurate stabilization of images for coronagraphic purpose. However, SAXO, as well as the overall instrument, must also provide constant operability overnights, ensuring robustness and autonomy. An original control scheme has been developed to satisfy this challenging dichotomy. It includes in particular both an Optimized Modal Gain Integrator (OMGI) to control the Deformable Mirror (DM) and a Linear Quadratic Gaussian (LQG) control law to manage the tip-tilt (TT) mirror. LQG allows optimal estimation and prediction of turbulent angle of arrival but also of possible vibrations. A specific and unprecedented control scheme has been developed to continuously adapt and optimize LQG control ensuring a constant match to turbulence and vibrations characteristics. SPHERE is thus the first operational system implementing LQG, with automatic adjustment of its models. SAXO has demonstrated performance beyond expectations during tests in Europe, in spite of internal limitations. Very first results have been obtained on sky last May. We thus come back to SAXO control scheme, focusing in particular on the LQG based TT control and the various upgrades that have been made to enhance further the performance ensuring constant operability and robustness. We finally propose performance assessment based on in lab performance and first on sky results and discuss further possible improvements.

Paper Details

Date Published: 7 August 2014
PDF: 17 pages
Proc. SPIE 9148, Adaptive Optics Systems IV, 91480O (7 August 2014); doi: 10.1117/12.2052847
Show Author Affiliations
C. Petit, ONERA (France)
J.-F. Sauvage, ONERA (France)
T. Fusco, ONERA (France)
Lab. d’Astrophysique de Marseille (France)
A. Sevin, Observatoire de Paris, CNRS (France)
M. Suarez, European Southern Observatory (Germany)
A. Costille, Lab. d'Astrophysique de Marseille, CNRS (France)
A. Vigan, Lab. d'Astrophysique de Marseille, CNRS (France)
C. Soenke, European Southern Observatory (Germany)
D. Perret, Observatoire de Paris, CNRS (France)
S. Rochat, Institut de Planétologie et d’Astrophysique de Grenoble, CNRS (France)
A. Barrufolo, INAF (Italy)
B. Salasnich, INAF (Italy)
J.-L. Beuzit, Institut de Planétologie et d’Astrophysique de Grenoble, CNRS (France)
K. Dohlen, Lab. d'Astrophysique de Marseille, CNRS (France)
D. Mouillet, Institut de Planétologie et d’Astrophysique de Grenoble, CNRS (France)
P. Puget, Institut de Planétologie et d’Astrophysique de Grenoble, CNRS (France)
F. Wildi, Univ. of Genève (Switzerland)
M. Kasper, European Southern Observatory (Germany)
J.-M. Conan, ONERA (France)
C. Kulcsár, Institut d'Optique Graduate School, CNRS (France)
H.-F. Raynaud, Institut d'Optique Graduate School, CNRS (France)


Published in SPIE Proceedings Vol. 9148:
Adaptive Optics Systems IV
Enrico Marchetti; Laird M. Close; Jean-Pierre Véran, Editor(s)

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