高动态情形下基于X射线脉冲星异步观测的导航方法研究

X-ray pulsar-based navigation (XPNAV) is a new celestial navigation method, which can automatically measure the position, velocity and time of the spacecraft without any external sources of information and has drawn much attention from international space agencies. In order to solve the problem that the estimation accuracy of the pulse time difference of arrival (TDOA) as well as the navigation accuracy decline dramatically when the spacecraft flies with high and time-varying speed, our research group plan to design a new asynchronous observation model based XPNAV method specifically for high dynamic circumstances, mainly focusing on the following issues: 1) how to estimate the time varying Doppler frequency and pulse TDOA under high dynamic circumstances; 2) how to fusion asynchronous measurements from different navigation pulsars. The key innovation points of our research are as follows: .1).A frame of how to estimate the time varying Doppler frequency and pulse TDOA step by step is expected to be proposed, in which the real-time phase model of photons detected at the spacecraft is formulated more accurately according to the pulsar spin down law at the SSB and the large-scale relativistic effects of photo signals, the large computational cost involved by the joint estimation is avoided. Besides, new Doppler frequency estimation method as well as pulse TDOA estimation method is to be designed under this frame, aiming to improve the estimation accuracy of Doppler frequency and pulse TDOA under cases of short-time observation which is unavoidably resulted by high dynamic motion of the spacecraft. The relational model between the observation time and estimation accuracy of pulse TDOA is also to be developed in order to determine the optimal observation timespan for each pulsar..2).A new asynchronous fusion filtering algorithm based on particle filter is to be designed to achieve optimal utilization of observation information from different navigation pulsars and therefore to achieve optimal pulse TDOA estimation for each pulsar. .Experiments are to be carried out to evaluate the new technique’s performance, using both simulated data and RXTE real data. Our expected achievements will provide theoretical foundations for future flying experiments of XPNAV.

X射线脉冲星导航（XPNAV）是一种新型自主天文导航方式，备受国际航天机构的关注。针对现有导航方案在航天器处于高速时变运动时难以准确估计脉冲到达时间差（TDOA），导致导航精度较低这一问题，本课题拟结合航天器轨道动力学模型，设计一种高动态情形下基于异步观测模型的XPNAV方法， 重点研究：1）轨道高动态情形下光子序列的高精度脉冲TDOA估计方法；2）脉冲星异步导航观测量的融合滤波方法。核心创新性在于：1）提出一种高动态情形下多普勒频率和脉冲TDOA分步估计框架，对轨道高动态特性进行更准确地建模，避免联合估计的巨大运算量，且针对短时观测设计光子到达时间序列的频率估计算法和脉冲TDOA估计算法，构建不同轨道高度下脉冲TDOA估计精度与观测时长之间的关系模型，为不同流量脉冲星设计不同的估计策略；2）提出一种基于粒子滤波的脉冲星异步观测数据融合算法，实现不同脉冲星信号的最优利用和最优TDOA估计。

X射线脉冲星导航（XPNAV）是一种新型自主天文导航方式，备受国际航天机构的关注。针对现有导航方案在航天器处于高速时变运动时难以准确估计脉冲到达时间（TDOA），导致导航精度较低这一问题，本课题结合航天器轨道动力学模型，设计一种高动态情形下的XPNAV方法， 重点研究：1）轨道高动态情形下光子序列的高精度脉冲TDOA估计方法；2）脉冲星导航观测量融合滤波方法。核心创新性在于：1）提出一种高动态情形下多普勒频率和脉冲TDOA分步估计框架，对轨道高动态特性进行更准确地建模，避免联合估计的巨大运算量，且针对短时观测设计光子到达时间序列的频率估计算法和脉冲TDOA估计算法，构建不同轨道高度下脉冲TDOA估计精度与观测时长之间的关系模型，为不同流量脉冲星设计不同的估计策略；2）提出一种基于无迹卡尔曼滤波的脉冲星观测数据融合算法，实现不同脉冲星信号的最优利用和最优TDOA估计。