Hughes Electronics Corporation

Umesh S Ketkar

Rongsheng Li

Yeong-Wei Andy Wu

Richard Yining Chiang

Bruce N Eyerly

Stephen D Burke

Vytas J Katilius

Control systems and methods are provided which enhance acquisition range, transient response and offset pointing accuracy in beacon-assisted orientation of a spacecraft to a desired spacecraft attitude A,. The methods receive a beacon signal with antennas that are arranged in a fixed angular relationship to thereby form an attitude error signal S,whose magnitude is a measure of the attitude difference between a current spacecraft attitude A,and the desired spacecraft attitude A,. A sum power P,that is the sum of the signal powers from the antennas is sensed and a signal modifier S,is generated that increases with decreases in the sum power P,. The attitude error signal S,is then modified with a term (1&plus;S,) to form an enhanced attitude error signal S,. In one embodiment, the signal modifier S,is n&verbar;P,&minus;P,&verbar;,wherein n and m are positive numbers and P,is the sum power P,when the attitude error is zero.

Beacon-assisted spacecraft attitude control systems and methods

Solar wing positioning methods are provided which favorably reduce seasonal variation of generated power in a satellite while simultaneously managing the composite system influence that off-pointed solar wing operation imposes on the satellite. The composite system influence includes environmental torques and may also include other system influences such as wing-to-body thermal radiation, thruster plume impingement and antenna/sensor field of view encroachment. In the simplest method embodiment, the solar wings are tilted asymmetrically from a nominal position to reduce seasonal power variations and are further tilted symmetrically to generate a solar pressure torque component which, on a diurnal average basis, compensates a gravity gradient torque component that is substantially generated by the net, off-pointed configuration of the wings.

Methods for reducing solar array power variations while managing the

A gimbal system includes a pair of stepper motors that drive respective drive trains of a differential drive assembly such as a differential gear assembly. Either the drive ratios or the step sizes for the two motors are offset from each other to provide four modes of operation, including modes for improved resolution and faster slew rate, and two intermediate modes with more balanced resolution and slew rate.

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Redondo Beach, CA, United States of America

Umesh S Ketkar