Binary pulsar navigation and its systematic bias suppression using sequential measurement difference

The availability and distribution of isolated X-ray pulsars suitable for navigation are limited in space. In contrast, there is a considerable number of binary pulsars available for navigation, albeit with the added complexity of accounting for the orbit of the binary pulsar system. Directly utilizing binary pulsars for spacecraft navigation has significant systematic biases. Therefore, to establish a measurement model applicable to both binary pulsars and isolated pulsars, effectively suppressing time-varying systematic biases and enhancing navigation accuracy, this paper introduces a pulsar navigation method based on the phase and Doppler frequency shift of binary pulsars. Initially, we formulated a navigation measurement model considering systematic biases, leveraging the phase and Doppler frequency shift of binary pulsars. Subsequently, a detailed analysis of systematic biases was conducted. Recognizing the characteristics of systematic biases, we further established a binary pulsar navigation measurement model with sequential difference. For deep space spacecraft, the time-varying system bias amplitude is large, but it changes slowly during the filtering period. Therefore, the proposed binary pulsar navigation measurement model with sequential difference effectively suppresses the majority of systematic bias effects. The effectiveness of the proposed method is demonstrated through 100 Monte Carlo simulation trials based on the Tianwen-1 Mars mission trajectory. The results show that the proposed method achieves a position error of approximately 824 m and a velocity estimation accuracy better than 1 m/s. Further analysis indicates that the remaining errors are primarily influenced by measurement noise and process noise, suggesting that reducing noise levels or incorporating more accurate models could further improve navigation performance.