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NFIRAOS: TMT's facility adaptive optics system.

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Title: NFIRAOS: TMT's facility adaptive optics system.
Author: Hickson, Paul; Pfrommer, Thomas
Issue Date: 2010
Publicly Available in cIRcle 2011-09-19
Publisher Society of Photo-Optical Instrumentation Engineers
Citation: Herriot, Glen; Andersen, David; Atwood, Jennifer; Boyer, Corinne; Beauvillier, Annie; Byrnes, Peter; Conan, Rod; Ellerbroek, Brent L.; Fitzsimmons, Joeleff; Gilles, Luc; Hickson, Paul; Hill, Alexis; Jackson, Kate; Lardiere, Olivier; Pazder, John; Pfrommer, Thomas; Reshetov, Vladimir; Roberts, Scott; Veran, Jean-Pierre; Wang, Lianqi; Wevers, Ivan. NFIRAOS: TMT's facility adaptive optics system. Adaptive Optics Systems II, edited by Brent L. Ellerbroek, Michael Hart, Norbert Hubin, Peter L. Wizinowich. Proceedings of SPIE Volume 7736, 77360B, 2010. http://dx.doi.org/10.1117/12.857662
Abstract: NFIRAOS, the TMT Observatory's initial facility AO system is a multi-conjugate AO system feeding science light from 0.8 to 2.5 microns wavelength to several near-IR client instruments. NFIRAOS has two deformable mirrors optically conjugated to 0 and 11.2 km, and will correct atmospheric turbulence with 50 per cent sky coverage at the galactic pole. An important requirement is to have very low background: the plan is to cool the optics; and one DM is on a tip/tilt stage to reduce surface count. NFIRAOS' real time control uses multiple sodium laser wavefront sensors and up to three IR natural guide star tip/tilt and/or tip/tilt/focus sensors located within each client instrument. Extremely large telescopes are sensitive to errors due to the variability of the sodium layer. To reduce this sensitivity, NFIRAOS uses innovative algorithms coupled with Truth wavefront sensors to monitor a natural star at low bandwidth. It also includes an IR acquisition camera, and a high speed NGS WFS for operation without lasers. For calibration, NFIRAOS includes simulators of both natural stars at infinity and laser guide stars at varying range distance. Because astrometry is an important science programme for NFIRAOS, there is a precision pinhole mask deployable at the input focal plane. This mask is illuminated by a science wavelength and flat-field calibrator that shines light into NFIRAOS' entrance window. We report on recent effort especially including trade studies to reduce field distortion in the science path and to reduce cost and complexity. Copyright 2010 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Affiliation: Science, Faculty ofPhysics and Astronomy, Department of
URI: http://hdl.handle.net/2429/37462
Peer Review Status: Reviewed
Scholarly Level: Faculty

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