Attitude Estimation for a Spinning Satellite from Gyroscope and Star Mapper Data

Star mappers measure attitude parameters at different, not regular, time instants. They never give a simultaneous set of measurements sufficient for a complete attitude determination. Gyroscopes sense angle deviations and give a continuous, complete, attitude estimate whose variance steadily increases withtime. By combining measurements from star mappers and gyros, the attitude parameters can be reconstructed withanerror variance which is kept bounded as the time increases. An analytic solution to the problem is given and a "guaranteed variance" estimation algorithm for gyro drift rates, based on simple computations, is proposed.