Active Image Stabilization for Shuttle-Based Payloads

This paper presents a pointing performance analysis of the Space Infrared Telescope Facility (SIRTF) as a generic example illustrating the fundamental dynamics and control problems related to optical instruments that are, or will be, flown mounted on the Space Shuttle. The disturbance level on the Shuttle, and slew requirements of the payload itself, along with the limitations of the present instrument pointing system (IPS) is found to seriously limit the pointing accuracy of optical payloads. The implementation of an active image stabilization (AIS) system, using an active secondary mirror, is shown to provide substantial improvement in performance. Two control strategies are presented, using IPS-mounted rate integrating gyros only, or in conjunction with a focal plane sensor feedback loop.