<h2>AAS  96-174</h2><h2>PREDICITIVE FILTERING FOR ATTITUDE ESTIMATION WITHOUT RATE SENSORS</h2><h4>J. L. Crassidis and F. L. Markley, Goddard Space Flight Center</h4><h2> Abstract </h2>In this paper, a real-time predictive filter is derived for spacecraft attitude estimation without the utilization of angular rate measurements from  gyros. The formulation described in this paper is shown using only attitude sensors. The real-time nonlinear filter predicts the required torque modeling error input in order to propagate the spacecraft dynamic model, so that model responses match the measured vector observations.  The real-time predictive filter is used to estimate the attitude of the Solar, Anomalous, Magnetospheric Particle Explorer (SAMPEX) spacecraft. Results using this new algorithm indicate that it estimates the attitude of an actual spacecraft with the sole use of magnetometer sensor measurements.<br><br>