Spacecraft angular rate estimation from magnetometer data only

A method is presented for fast estimation of the angular rate of a tumbling spacecraft in a low-Earth orbit, from sequential readings of Earth's magnetic field. Useful as a backup algorithm in cases of rate gyro malfunctions, or during the initial acquisition phase, the estimator consists of an extended Kalman filter, based on the underlying assumption that the geomagnetic field vector does not significantly change (relative to an inertial frame of reference) during the short sampling time. Contrary to previously introduced angular rate estimators, the spacecraft's attitude is not assumed to be known (nor is it estimated as part of the proposed procedure). Moreover, the body-referenced geomagnetic field observations are not differentiated with respect to time as a prefiltering procedure, but are directly processed by the filter. A simulation study employing the standard 8th order IGRF geomagnetic field model is presented to demonstrate the performance of the algorithm. © 2000 by P. Tortora and Y. Oshman. Published by the American Institute of Aeronautics and Astronautics, Inc.