Attitude determination concepts for the Space Station Freedom

The requirements, technical approach, and key features of the attitude determination system (ADS) being developed for the Space Station Freedom are described. Use of current technology provides new capabilities for all attitude autonomous operation and rapid determination of attitude in a debris-filled environment. The ADS is implemented using star trackers with fixed mosaic array detectors and inertial sensors based on laser gyro technology. Star catalog characteristics, star identification techniques, the functional implementation of the ADS system, and the results of preliminary covariance performance analyses are presented. Covariance analysis indicates that the stringent accuracy requirements of the Space Station can be met with the baseline system. The automated ADS mechanization provides rapid attitude acquisition from any orientation where stars are visible; astronaut intervention is not required. The inertial sensors and the star trackers are on-orbit replaceable, are highly reliable, and promise long-life operation