7 July 2000 Adaptive optics with four laser guide stars: cone effect correction on large telescopes
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Abstract
In this paper, we study the performance of an adaptive optics system with 4 laser guide stars (LGS) and a natural guide star (NGS), and compare it to the system with 1 LGS, both installed on an 8-m telescope. Focus anisoplanatism is obtained with a numerical simulation. The typical errors of NGS wavefront are computed with analytical formulae. The entire system is studied to obtain its performance in terms of achievable Strehl ratio. This 4-LGS method allows to push adaptive optics system towards the visible part of the spectrum without tomographic reconstruction of 3D atmospheric perturbation. The cone effect is two times smaller with 4-LGS than with 1-LGS, allowing to reach almost a Strehl ratio of 0.5 at 500 nm. Considering the NGS errors and the focus anisoplanatism, the Strehl ratio (SR) can reach 0.45 at 1.25 micrometer under good seeing (GS) conditions with the Nasmyth Adaptive Optics System (14 X 14 sub-pupils wavefront sensor) at the Very Large Telescope.
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Elise Vernet-Viard, Elise Vernet-Viard, Norbert N. Hubin, Norbert N. Hubin, Miska Le Louarn, Miska Le Louarn, } "Adaptive optics with four laser guide stars: cone effect correction on large telescopes", Proc. SPIE 4007, Adaptive Optical Systems Technology, (7 July 2000); doi: 10.1117/12.390343; https://doi.org/10.1117/12.390343
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