日地系统L2点Halo轨道自主天文导航及精度分析

针对运行于日地L₂点Halo轨道探测器，给出了质心惯性坐标系和质心旋转坐标系中的探测器运动方程，并建立了以星光角距作为观测量的导航模型，采用扩展卡尔曼滤波（EKF）算法解算探测器位置，以Cramér-Rao误差下界（CRLB）为系统可观测度的度量标准分析了不同的状态量和观测量对导航性能的影响. 通过数值仿真发现导航坐标系、主天体、导航恒星数目以及滤波器采样周期等因素对导航性能的影响较大，并依据平动点轨道运动学分析了以上因素对导航精度的影响. 

Autonomous Celestial Navigation and Analysis of Precision for Spacecraft on Halo Orbit Near L2 Point of Sun-Earth System

For the spacecraft in Halo orbits around L₂ point in Sun-Earth system, firstly, the kinematics equation of spacecraft in initial frame and rotating frame (and celestial navigation model whose measurement is starlight angle were presented. Secondly, the celestial navigation model whose measurement is starlight angle was established; thirdly, an extended Kalman filter (EKF) algorithm was used to estimate of the position of the spacecraft; finally, the performance of the system using different kinds of statement and measurement was analyzed based on the Cramér-Rao low bound method. Simulation results show that some factors that influence largely on the precision of position estimation are pointed, which includes navigation coordinate system, the major celestial body, the number of observing the stars and filter observation time. The results of the above factors impacting on the precision of celestial navigation are analyzed based on libration point orbit kinematic characteristics.