Three-axis spacecraft attitude control using polar star sensor

Abstract

A three-axis attitude control system for a spacecraft in an equatorial orbit includes at least a horizon sensor for producing pitch-representative signals. A star sensor has a boresight parallel to the spacecraft pitch axis, and produces signals representative of the two-axis location of a selected pole star relative to the boresight. The star sensor signals are processed in conjunction with the pitch-representative signals and with orbit-location information, to produce roll and yaw information. The pitch, roll and yaw information controls spacecraft torquing. In a particular embodiment of the invention, the horizon sensor arrangement also produces roll signals, which are processed with the roll signals from the star sensor.