Wavefront sensing with laser guide stars on the ELTs

Nicolas Muller; Vincent Michau; Thierry Fusco; Clélia Robert; Sandrine J Thomas; Gerard Rousset

doi:10.1117/12.857948

27 July 2010 Wavefront sensing with laser guide stars on the ELTs

Nicolas Muller, Vincent Michau, Thierry Fusco, Clélia Robert, Sandrine J Thomas, Gerard Rousset

Proceedings Volume 7736, Adaptive Optics Systems II; 773628 (2010) https://doi.org/10.1117/12.857948
Event: SPIE Astronomical Telescopes + Instrumentation, 2010, San Diego, California, United States

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.

Citation Download Citation

Nicolas Muller, Vincent Michau, Thierry Fusco, Clélia Robert, Sandrine J Thomas, and Gerard Rousset "Wavefront sensing with laser guide stars on the ELTs", Proc. SPIE 7736, Adaptive Optics Systems II, 773628 (27 July 2010); https://doi.org/10.1117/12.857948

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KEYWORDS

Sodium

Wavefront sensors

Wavefronts

Adaptive optics

Error analysis

Laser guide stars

Telescopes

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