A fast period estimation method for XPNAV based on phase difference of folded profiles

Abstract

In X-ray pulsar navigation, the processing of pulsar photon time-of-arrival (PTOA) data is a key technology, and accurate estimation of the pulsar period is essential for effective PTOA data processing. The speed of period estimation directly affects the real-time performance of the navigation system. To address the low real-time performance of existing pulsar period estimation methods, this paper proposes a fast period estimation method based on phase difference correction. The method establishes a mapping between the phase difference of two folded pulse profiles and the period estimation error. The period is then estimated through an iterative computation process. Compared with the traditional Chi-square search method and the improved $Z_2^2$-test method, the proposed method significantly reduces the number of epoch-folding operations. Using the Crab pulsar as the primary case study, both simulation and experimental results demonstrate that the proposed method achieves high computational efficiency while maintaining reliable period estimation accuracy. When the observation duration is 1000 s and the detector area is 5000 cm${}^2$, the proposed method reduces the CPU time by 99.92% and 99.90% compared to the Chi-square search and improved $Z_2^2$-test methods, respectively. This substantial improvement in computational efficiency makes the proposed method a promising tool for fast pulsar period estimation, thereby facilitating its practical application in deep space navigation.