精密卫星钟差加密方法及其对星载GPS低轨卫星定轨精度影响

系统分析、比较了几种精密卫星钟差加密方法，研究了利用全球分布的IGS永久跟踪站的GPS观测数据估计高采样率卫星钟差参数的原理与方法，并将各种卫星钟差加密方法得到的结果与IGS数据分析中心估计的卫星钟差结果相比较。最后将不同加密方法得出的精密卫星钟差结果用于基于星载GPS双频非差观测值的CHAMP低轨卫星的定轨，并将不同方法得到的定轨精度进行比较。结果表明，利用地面跟踪站的GPS观测数据，可高精度、高密度地估计GPS卫星钟差，估计精度可达0．1～0．5ns。经地面GPS跟踪站数据估计的GPS卫星钟差，应用于基于PPP方法的低轨卫星定轨，其定轨精度在10cm以内。

Densification Methods of GPS Satellite Clock Errors and Their Impact on Orbit Determination Precision of LEOs

The application of so-called precise point positioning(PPP) method has been limited by the different interval of GPS satellite clock errors provided by IGS or its analysis centres and users.In order to cope with this problem,the commonly used densification methods of GPS satellite clock errors,especially the principle of estimation of high-rate satellite clock errors using IGS ground tracking stations have been analysed and compared.Then the results obtained by different densification method including estimation method are compared with the estimated high-rate satellite clock errors by IGS.After that the satellite clock errors gained by different densification methods introduced have been used for CHAMP orbit determination(OD) employing PPP method combined with dynamic models,and the precision of them are compared as well.The results show that GPS ground tracking data can be used for estimation of high rate satellite clock errors.The precision of estimation is about 0.1 ns to 0.5 ns,which is close to the precision of IGS.The OD precision of LEOs based on PPP method using satellite clock errors obtained by estimation discussed in this paper is less than 10 cm.