Importance

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Abstract

The attitude corrections required to remove attitude errors induced by orbit inclination deviations from the normal orbit plane, as well as the residual errors, are minimized by placing the satellite bias momentum at an inertial attitude lying substantially between the normals of the nominal and actual orbits, and using a payload reorientation means to adjust the payload attitude about three axes based on a combination of sensor data and offsets computed from the known orbit kinematics. In one embodiment, a momentum bias satellite is in an orbit slightly inclined from the geostationary orbit. The desired angular momentum vector attitude is chosen based on the orbit, the desired payload attitude, and the gimbal capabilities, and executed using thrusters. This reorientation limits the required gimbal travel. Based on this information, time-varying payload offsets in yaw, pitch and roll are computed from the nominal attitude produced by nulling earth sensor errors in roll and pitch, and using momentum bias and yaw estimation to control yaw. These offsets are implemented by a 3-axis gimbal between the momentum bias and the payload. Other sensors, actuators, or orbits could be used, including beacon sensors, star sensors, magnetic torquing, solar torquing, electronic steering, and other gimbal arrangements.

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First Claim