| Preliminary Closed-Loop Results From an Adaptive Optics System Using a Sodium Resonance Guide Star (2007) | |||||||||||||||
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| A sodium guide star has been used to sense and correct atmospheric aberration during two runs at the Multiple Mirror Telescope (MMT). For the first run in 1993 May, the artificial star was created by a 0.5 W beam from a continuous-wave dye laser tuned to the D 2 resonance line, projected from a telescope centered and coaxial with the main array of six 1.8 m mirrors. Scattering by the mesospheric sodium layer produced an artificial beacon equivalent in brightness to a natural star of visual magnitude 12.5, and of angular extent 1².2 full width at half maximum (FWHM). During the second run in 1994 February, a 1.7 W dye laser was used to generate an artificial guide star of visual magnitude 10.4, and 1².1 FWHM. 1 In each case, the beacon was used by the MMT adaptive optics system to compensate in real time for atmospherically-induced differential image motion between the six mirror elements, at correction rates of up to 76 Hz. In the latter experiment, global wavefront tilt correction u... | |||||||||||||||
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