A Fast Simplified Model for X-ray Pulsar Photon Arrival Time Conversion

A high-precision X-ray photon arrival time conversion model is crucial to the accuracy of X-ray Pulsar-based Navigation. Aiming at the current problem that the complete model is complex and the simplified model has limited accuracy, a fast simplified model with accuracy no less than the existing simplified model is proposed in this paper. Through the derivation of the existing complete model, the influence of each delay item on the accuracy of the model is theoretically analyzed, and it is pointed out that the Roemer delay is still the key to the accuracy of the simplified model. A fast simplified model was obtained by changing the expression of the Roemer delay and its second-order expansion, and considering the ease of access to physical quantities in practical application. The accuracy and computational efficiency of the proposed model are analyzed by using the complete model and the proposed simplified model to time-transform the measured photon data of NICER (Neutron star Interior Composition Explorer) and HXMT (Hard X-ray Modulation Telescope) satellites. Furthermore, the influence of orbital altitude and pulsar angular position measurement errors on the accuracy of the simplified model is analyzed by numerical simulation, and the accuracy and computational efficiency of the simplified model in the application of Earth orbit at different altitudes are discussed. The results show that the computational efficiency of the simplified model proposed in this paper is improved 50% than that of the Sheikh’s simplified model and 10% than the fei’s model, without causing a decrease in accuracy. © 2024 Chinese Institute of Electronics. All rights reserved.