Predictive filtering for attitude estimation without rate sensors

A real-time predictive filter is derived for spacecraft attitude estimation without the utilization of angular rate measurements from gyros. The formulation is shown using only attitude sensors (three-axis magnetometers, sun sensors, star trackers, etc.). The new 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 the real-time predictive filter accurately estimates the attitude of an actual spacecraft with the sole use of magnetometer sensor measurements.