一种X射线脉冲星导航的多普勒频移估计方法

为了探索脉冲星Doppler导航在近地轨道的应用，建立了近地轨道Doppler频移估计的数学模型，引入RANSAC算法和航天器速度先验信息，改进了时域χ2统计的计算精度和搜索效率，使用RXTE卫星的Crab脉冲星实测数据进行方法校验，最后讨论了影响速度测量的主要误差。结果表明：提出的方法能够有效地跟踪航天器速度变化，对于轨道高度为570km的RXTE卫星，沿脉冲星视线方向的速度估计误差为±110m/s，加速度估计误差为±0.5m/s 2。

A Doppler Shift Estimation Method for X Ray Pulsar Based Navigation

When a spacecraft moves toward or away from the X-ray pulsars, Doppler effects are present in the pulsar signal measured by onboard X-ray detectors. By measuring the observed pulsar frequency, the speed of the spacecraft along the line of sight of the pulsar can be derived. The mathematical model is established to characterize the spacecraft’s velocity estimation by adopting the time of arrival of X-ray photons. To improve the accuracy of Doppler frequency estimation, a robust averaging technique, RANSAC, is introduced to combine with the χ2 statistical method. Besides, the priori information of the spacecraft velocity is utilized to improve the computational efficiency. The Crab pulsar data observed by RXTE satellite are applied to validate the presented method and some dominating error factors are analyzed. The results demonstrate that the method can track the spacecraft’s velocity effectively. For RXTE satellite with the orbit altitude 570km, in terms of the obvious changes in spacecraft’s acceleration, the velocity estimation error along the line of sight of the pulsar is about ±150m/s, and the corresponding acceleration estimation error is ±0.5m/s 2.