Astronomy and Astrophysics – Astrophysics
Scientific paper
2000-04-05
Mon.Not.Roy.Astron.Soc. 317 (2000) 535
Astronomy and Astrophysics
Astrophysics
11 pages, 9 figures, 4 tables. Accepted for publication in MNRAS
Scientific paper
10.1046/j.1365-8711.2000.03607.x
The performance of an adaptive optics (AO) system on a 100m diameter ground based telescope working in the visible range of the spectrum is computed using an analytical approach. The target Strehl ratio of 60% is achieved at 0.5um with a limiting magnitude of the AO guide source near R~10, at the cost of an extremely low sky coverage. To alleviate this problem, the concept of tomographic wavefront sensing in a wider field of view using either natural guide stars (NGS) or laser guide stars (LGS) is investigated. These methods use 3 or 4 reference sources and up to 3 deformable mirrors, which increase up to 8-fold the corrected field size (up to 60\arcsec at 0.5 um). Operation with multiple NGS is limited to the infrared (in the J band this approach yields a sky coverage of 50% with a Strehl ratio of 0.2). The option of open-loop wavefront correction in the visible using several bright NGS is discussed. The LGS approach involves the use of a faint (R ~22) NGS for low-order correction, which results in a sky coverage of 40% at the Galactic poles in the visible.
Hubin Norbert N.
Le Louarn Miska
Sarazin Marc
Tokovinin Andrei
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