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1 September 1972 Modal Control Applied To The Real-Time Figure Control Of A Spaceborne Telescope Mirror
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A method of modal control for active optical systems, suggested by Creedon and Lindgren (Ref. 1), has been implemented on a small scale for real-time automatic figure control of a large spaceborne telescope mirror'-'. The system configuration includes a set of actuators placed behind a 30-inch diameter, 1/2-inch thick mirror to deform its reflecting surface. The control sig-nals are derived from an interferometer uging a Helium-Neon Laser for a refer-ence source. The object of the method is to select a minimum set of actuators at strategic locations so that while the lower order bending mode amplitudes of the mirror's figure error are nulled, the higher order mode amplitudes are not excited. In this way, modal control suggests a strategy for an implementation to effect diffraction-limited performance while minimizing the number of active mechanical control elements required. This paper reports the validation of theoretical conclusions by comparison with experimental results for a seven point system. The results have yet to be applied to larger multi-point systems which may be encountered in practice due to the additional complexity.
© (1972) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
G. T. Volpe and H. J. Robertson "Modal Control Applied To The Real-Time Figure Control Of A Spaceborne Telescope Mirror", Proc. SPIE 0028, Instrumentation in Astronomy I, (1 September 1972);

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