ATTITUDE DETERMINATION AND AUTONOMOUS ON-ORBIT CALIBRATION OF STAR TRACKER FOR THE GIFTS MISSION

EO-3 GIFTS mission (2004). The camera is designed to be autonomously self-calibrating, and capable of a rapid/reliable solution of the lost-in-space problem as well as recursive attitude estimation. Two efficient Kalman filter algorithms for attitude, camera principal point offset, and focal length estimation are developed. These algorithms make use of three axis gyros for the rate data and star camera split field-of-view line-of-sight vector measurements. To model the optics of the camera the pinhole model is used, which is found to be sufficiently accurate for most of star cameras. The relative merits of the two algorithms are then studied for estimating the principal point offset, focal length and attitude of a simulated spacecraft motion. Simulation results indicate that both algorithms produce precise attitude estimates by determining the principal point offset, focal length and rate bias; however, reliability and robustness characteristics favor the second algorithm