粗差拟准检定法在星载GPS低轨卫星定轨中的应用

利用自适应卡尔曼滤波进行星载GPS低轨卫星定轨时,必须解决量测方程中经常存在的粗差问题．在分析以往方法的优缺点后,用拟准检定法来探测和修正量测方程中存在的粗差．该法的优点是辨识粗差准确率高,能同时定位多个粗差．另外,为了克服星载GPS低轨卫星定轨的滤波器可能出现的数值不稳定性及发散现象,还采用了UD分解算法及Sage自适应滤波器．最后用一个CHAMP卫星的模拟算例验证本方法的可行性和有效性．

Use of QUAD Method for GPS-based Orbit Determination of LEOs

Kalman filtering technique can be used as optimal estimation of motion state of a LEO (Low-Earth-Orbiter); it can be applied directly to real time Orbit Determination (OD), or to Precise Orbit Determination (POD) with post-processing mode. The OD accuracy using Kalman filters depends on a priori knowledge of system models, noise statistics, especially quality of observations from onboard GPS receiver on LEO. When using Kalman filtering technique for GPS-based OD of LEOs, the gross errors in observation equation must be well dealt with firstly. Having analyzed the characteristics of solving gross errors in pervious methods, QUasi-Accurate Detection (QUAD) of gross errors method has been employed to detect and correct gross errors in observations. The advantages of this method are: accuracy rate of detecting gross errors is high; multiple gross errors can be detected at the same time. In addition, UD decomposition technique and Sage adaptive filter are employed to overcome the instability of numerical value computation and divergence of filter that properly occurred. At last, a simulation example of CHAMP satellite is used to demonstrate the feasibility and validity of new method presented in this paper.