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Proceedings Paper

Wavefront sensing with laser guide stars on the ELTs
Author(s): Nicolas Muller; Vincent Michau; Thierry Fusco; Clélia Robert; Sandrine J Thomas; Gerard Rousset
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Paper Abstract

Adaptive Optics (AO) relies on aWave Front Sensor (WFS) to measure properly the perturbations induced by the turbulence on the wavefront. Yet, source extension may limit its performance. In the case of a Shack-Hartmann (SH) WFS associated to one or more Laser Guide Stars (LGS), this extension becomes all the more problematic as the diameter of the telescope tends to increase. In order to mitigate the effects induced by the spot elongation on the quality of the WFS measurements, various algorithms are used. Most of them are non-linear, and require a reference. The design of the SH WFS itself has an influence on the measurement quality, as it also induces non-linearities. In addition, the time-evolving structure of the LGS, due to the fluctuations of the Sodium layer, has an impact on the measurements as well. Eventually, both influences are coupled in the wavefront sensing process. The present study is aimed at optimizing a whole set of carefully chosen parameters defining the design of a SH WFS, in the particular case of a LGS on an ELT. The relative impact of these parameters are studied first at the subaperture level, and then on the reconstructed wavefront.

Paper Details

Date Published: 27 July 2010
PDF: 11 pages
Proc. SPIE 7736, Adaptive Optics Systems II, 773628 (27 July 2010); doi: 10.1117/12.857948
Show Author Affiliations
Nicolas Muller, ONERA (France)
Groupement d'Intérêt Scientifique PHASE (France)
Vincent Michau, ONERA (France)
Groupement d'Intérêt Scientifique PHASE (France)
Thierry Fusco, ONERA (France)
Groupement d'Intérêt Scientifique PHASE (France)
Clélia Robert, ONERA (France)
Groupement d'Intérêt Scientifique PHASE (France)
Sandrine J Thomas, Univ. of California Observatories (United States)
Gerard Rousset, LESIA, CNRS, Observatoire de Paris à Meudon, Univ. Paris Diderot (France)
Groupement d'Intérêt Scientifique PHASE (France)

Published in SPIE Proceedings Vol. 7736:
Adaptive Optics Systems II
Brent L. Ellerbroek; Michael Hart; Norbert Hubin; Peter L. Wizinowich, Editor(s)

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