Data fusion of three attitude sensors

A reliable Spacecraft attitude determination system, which integrate the measurements coming from the star tracker (STR), Global Positioning System (GPS) and gyros, is presented. The linearized state propagation and state update are two key algorithms in the data fusion. For state propagation, the primary information is provided by the high rate (16 Hz) sensors (gyros), whose measurement offsets are calibrated by the integrated filter. For state update, the primary information is provide by the low rate (1 Hz) sensors (STR and GPS). To minimize the update errors, the covariance matrices associated to different sensors are selected as the weightings. From the simulation results, our ideas are verified to be sound and effective.