Differential X-Ray Pulsar Navigation Method Based on Pulse Arrival Time Difference

The application of differential navigation technology can eliminate the influence of pulse ephemeris error, which can improve navigation accuracy. The paper proposes a differential X-ray pulsar navigation method, which is based on the time difference of pulse arrival. The method firstly uses the photon arrival sequence to get the pulse arrival time difference (TOA), then difference the current moment from the previous moment TOA, which constructs the navigation measurement equation. In this paper, robust unscented Kalman filter is used to solve the uncertainty of measurement model. The paper analyses the influence of ephemeris error on photon TOA correction and observation equation, infer the differential navigation measurement model and measurement noise covariance matrix. Simulate and verify three Mars orbits at different altitudes at different observation time. The simulation results show that the navigation accuracy of the standard X-ray pulsar navigation method decreases by about 60% when the error is 0.007". The proposed differential navigation method can improve the navigation accuracy by 24%-31%.