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Proceedings Paper

Sky coverage estimates for the natural guide star mode of the TMT facility AO system NFIRAOS
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Paper Abstract

Although the TMT AO system NFIRAOS will operate primarily in a laser guidestar multi-conjugate AO mode, it will also provide a conventional natural guide star (NGS) mode for use on very narrow science fields containing a bright star and/or when laser propagation is prevented by thin cirrus clouds or other circumstances. The number of bright stars suitable for use with a high order AO system is limited, so we have performed a sky coverage analysis to determine the likelyhood of achieving a given Strehl ratio when observing a randomly selected science field. The results obtained are significantly better than for existing NGS AO systems, largely due to (i) the anticipated availability of large, high-speed detector arrays with sub-electron read noise, and (ii) the benign telescope windshake disturbances predicted for TMT. Order 60×60 wavefront sensing and correction is preferred to lower order AO compensation, and an H-band Strehl of 0.25 [0.50] is obtained with sky coverage of about 1.0 [0.1] per cent at the Galactic pole in median seeing. This level of performance will provide an important capability for TMT well into the life of the observatory.

Paper Details

Date Published: 15 July 2008
PDF: 14 pages
Proc. SPIE 7015, Adaptive Optics Systems, 70155W (15 July 2008); doi: 10.1117/12.788053
Show Author Affiliations
B. Ellerbroek, TMT Observatory Corp. (United States)
David Andersen, Herzberg Institute of Astrophysics (Canada)


Published in SPIE Proceedings Vol. 7015:
Adaptive Optics Systems
Norbert Hubin; Claire E. Max; Peter L. Wizinowich, Editor(s)

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