Two-Step Robust Kalman Filtering Algorithm for X-ray Pulsar Navigation

In order to improve pulsar navigation accuracy under the influence of both pulsar direction error and clock error, the two-step robust Kalman filtering (RKF) method is proposed. Firstly, the influence of system uncertainty deviation and clock error caused by pulsar azimuth error on the system is analyzed. Secondly, the navigation system model including system uncertainty deviation and clock error caused by azimuth error is re-derived, and the observability of the model is proved. Thirdly, the clock error and state are separated, and the robust filter (RF) is designed for the uncertainty deviation, and the Kalman filter (KF) is used for the clock error. The two filters are combined to obtain the two-step robust filtering algorithm. Finally, numerical simulations shows that the proposed method can improve the X-ray pulsar navigation accuracy. And has higher computational efficiency.