Hughes Electronics Corporation

Joseph M Allard

Loren I Slafer

Michael F Barsky

Paul D Williams

Thomas M Tanner

George B Semeniuk

A Stationkeeping Mode for a spacecraft having a gimballed momentum wheel for attitude control in which the stationkeeping is divided into short duration open-loop stationkeeping maneuvers to correct orbital errors, and interlaced with closed-loop momentum management operations to manage momentum stored in the momentum wheel. The sequence of open-loop pulses are spaced to deadbeat a given dominant flexible motion of the spacecraft. Between and during the thruster pulses, the gimbaled momentum wheel is maintained in the closed-loop feedback control using gyro sensor or other inertial reference measurements. Limitations on the range of the momentum storage device and its torque capability are minimized by combining the maneuver thruster pulses with pulses from other thrusters, or by reducing the fire time of one of the maneuver thrusters, to minimize momentum buildup. Thus, thrusters are used for changing orbital velocity and managing momentum through open-loop pulsing with closed-loop momentum refinement, and the momentum storage device controls the attitude with closed-loop attitude feedback.

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Chiswick, United Kingdom

Joseph M Allard