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27 June 2006 NFIRAOS: TMT narrow field near-infrared facility adaptive optics
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Although many of the instruments planned for the TMT (Thirty Meter Telescope) have their own closely-coupled adaptive optics systems, TMT will also have a facility Adaptive Optics (AO) system, NFIRAOS, feeding three instruments on the Nasmyth platform. This Narrow-Field Infrared Adaptive Optics System, employs conventional deformable mirrors with large diameters of about 300 mm. The requirements for NFIRAOS include 1.0-2.5 microns wavelength range, 30 arcsecond diameter science field of view (FOV), excellent sky coverage, and diffraction-limited atmospheric turbulence compensation (specified at 133 nm RMS including residual telescope and science instrument errors.) The reference design for NFIRAOS includes six sodium laser guide stars over a 70 arcsecond FOV, and multiple infrared tip/tilt sensors and a natural guide star focus sensor within instruments. Larger telescopes require greater deformable mirror (DM) stroke. Although initially NFIRAOS will correct a 10 arcsecond science field, it uses two deformable mirrors in series, partly to provide sufficient stroke for atmospheric correction over the 30 m telescope aperture, but mainly to improve sky coverage by sharpening near-IR natural guide stars over a 2 arcminute diameter "technical" field. The planned upgrade to full performance includes replacing the ground-conjugated DM with a higher actuator density, and using a deformable telescope secondary mirror as a "woofer." NFIRAOS feeds three live instruments: a near-Infrared integral field Imaging spectrograph, a near-infrared echelle spectrograph, and after upgrading NFIRAOS to full multi-conjugation, a wide field (30 arcsecond) infrared camera.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Glen Herriot, Paul Hickson, B. L. Ellerbroek, D. A. Andersen, T. Davidge, D. A. Erickson, I. P. Powell, R. Clare, L. Gilles, C. Boyer, M. Smith, L. Saddlemyer, and J.-P. Véran "NFIRAOS: TMT narrow field near-infrared facility adaptive optics", Proc. SPIE 6272, Advances in Adaptive Optics II, 62720Q (27 June 2006);


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