MINIMUM MODEL ERROR APPROACH FOR ATTITUDE ESTIMATION

An optimal batch estimator and smoother based on the minimum model err or (MME) approach is developed for three-axis stabilized spacecraft. T he formulation is shown using only attitude sensors, e.g., three-axis magnetometers, sun sensors, star trackers, This algorithm accurately e stimates the attitude of a spacecraft and substantially smoothes noise associated with attitude sensor measurements. The general functional form of the optimal estimation approach involves the solution of a non linear two-point-boundary-value problem that can be solved only by usi ng computationally intense methods. A linearized solution also is show n that is computationally more efficient than methods that solve the g eneral form. The linearized solution is useful when an a priori estima te of the angular velocity is already known, which can be obtained fro m a finite difference of a determined attitude, or from propagation of a dynamics model. Results using this new algorithm indicate that an M ME-based approach accurately estimates the attitude of an actual space craft with the sole use of magnetometer sensor measurements.