New challenges for adaptive optics: the OWL 100-m telescope

Norbert N. Hubin; Miska Le Louarn; Marc S. Sarazin; Andrei A. Tokovinin; Elise Vernet-Viard

doi:10.1117/12.390315

7 July 2000 New challenges for adaptive optics: the OWL 100-m telescope

Norbert N. Hubin, Miska Le Louarn, Marc S. Sarazin, Andrei A. Tokovinin, Elise Vernet-Viard

Proceedings Volume 4007, Adaptive Optical Systems Technology; (2000) https://doi.org/10.1117/12.390315
Event: Astronomical Telescopes and Instrumentation, 2000, Munich, Germany

Abstract

Adaptive optics will be a key element of future Extremely Large Telescopes (ELTs) which need sharp images both to avoid object confusion and to boost sensitivity to point sources against sky background. A challenging task of correcting turbulence in the visible part of the spectrum is addressed. With an R approximately 10 natural guide star a Strehl ratio (SR) of 0.6 can be achieved at 500 nm, at the cost of an extremely low sky coverage. Thus, use of Multi-Conjugate Adaptive Optics techniques will be essential to widen the field of view (FOV). We summarize our recent theoretical results and show that with 3 deformable mirrors it is realistic to obtain a FOV diameter of 30' - 60' in the visible, or 3' - 6' in the K band. Contrary to the common belief, the layered structure of the turbulence vertical profile is not needed to achieve this limit, neither do we need to know the profile exactly. The wide corrected FOV ensures a reasonably good sky coverage in the near infrared using 4 natural guide stars (60% in the J band at medium Galactic latitudes). Artificial Laser Guide Stars will be needed to correct in the visible, using in addition a faint natural star to measure low-order wavefront aberrations. On ELTs this star can be faint, up to R equals 23, so a good sky coverage can also be obtained. A significant fraction of guide sources at these magnitudes are extragalactic.

Citation Download Citation

Norbert N. Hubin, Miska Le Louarn, Marc S. Sarazin, Andrei A. Tokovinin, and Elise Vernet-Viard "New challenges for adaptive optics: the OWL 100-m telescope", Proc. SPIE 4007, Adaptive Optical Systems Technology, (7 July 2000); https://doi.org/10.1117/12.390315

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