CE-5T1探月飞行器地月转移段和环月段的实时定轨

Real-time orbit determination for transfer orbit and lunar orbit of the CE-5T1 probe

随着我国探月工程和深空探测工程的实施,传统的地基测轨手段联合最小二乘定轨预报的模式已难以满足定轨任务的实时性需求,为此需要发展飞行器的自主测轨手段和定轨方法.本文采用扩展卡尔曼滤波算法对探月飞行器进行实时定轨研究.对CE-5T1月地转移段约2.5?h弧长的星基GNSS伪距数据进行滤波处理,计算结果表明,以预报轨道为先验参考轨道,约1?h后滤波即可稳定收敛,且收敛后轨道精度与批处理统计定轨精度相当,位置偏差(Root Mean Square,RMS)约在30?m,速度偏差好于1?cm/s.对CE-5T1环月段地基测量数据进行滤波计算,计算结果表明,对于轨道周期为2h的月球探测器,位置偏差好于50m(RMS).由于之前的定轨信息通过协方差矩阵传递保留,月球遮挡探测器以及月球升落引起的地面测轨数据长弧段间断不会影响后续可视弧段的滤波精度,且只需一两个观测数据即可快速收敛至滤波稳定.

In order to meet the needs of autonomous capability for the lunar exploration, an analysis of real-time orbit determination is proposed in this paper for the CE-5T1 probe by using extended Kalman filter. For the lunar-Earth transfer orbit, compared with the least squares method, the accuracy of orbit determination result using 2.5 h satellite-based GNSS data is about 30 m in position, and 1 cm/s in velocity by using EKF method, as well as the velocity of convergence is better than 1 h. For the lunar orbit, the result shows that the EKF method is able to achieve the same level accuracy to the least squares method, furthermore, through a better orbit forecast algorithm design, the Earth-based observation gap caused by the shelter of the moon has little influence to the filter accuracy of the following observation arc.