A Minimum Model Error Approach for Attitude Estimation

In this paper, an optimal batch estimator and smoother based on the Minimum Model Error (MME) approach is developed for three-axis stabilized spacecraft. The formulation described in this paper is shown using only attitude sensors (e.g., three-axis magnetometers, sun sensors, star trackers, etc). This algorithm accurately estimates 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 nonlinear two-point-boundary-valueproblem that can only be solved using computational intense methods. A linearized solution is also shown that is computationally more efficient than methods which solve the general form. The linearized solution is useful when an a priori estimate of the angular velocity is already known, which may be obtained from a finite difference of a determined attitude, or from propagation of a dynamics model. Results using this new algorithm indicate that an MME-based approach accurately estimates the attitude of an actual spacecraft with the sole use of magnetometer sensor measurements. 1 Assistant Professor, Catholic University of America, Dept. of Mech. Eng., Washington, D.C. 20064. Member AIAA. 2 Staff Engineer, Goddard Space Flight Center, Code 712, Greenbelt, MD 20771. Associate Fellow AIAA