北斗在轨卫星广播星历精度分析

为分析北斗广播星历的精度，采用激光测距资料和精密星历作为参考进行分析。由于没有提供BDS-3试验卫星精密星历，本文设计了3天弧段的DBS-3试验卫星精密定轨试验，解算的轨道精度约为50 cm，钟差精度约为2 ns。之后联合国际GNSS监测评估系统iGMAS发布的事后BDS-2精密星历，对BDS-3/BDS-2广播星历轨道、钟差精度进行分析。为准确评估广播星历轨道精度，还采用SLR观测数据作为外部检核手段分析北斗在轨卫星广播星历轨道精度。统计了广播星历轨道误差的1D RMS和钟差误差的STD，结果表明：多数钟差精度优于 10 ns ，轨道精度优于5 m。另外为分析广播星历卫星钟的时频性能，计算了在轨卫星钟差的频率稳定度、漂移率和准确度，试验结果表明：BDS-3试验卫星各项性能指标普遍优于BDS-2，频率准确度、频率漂移率和频率稳定性指标计算结果显示BDS-3卫星相对于BDS-2卫星分别提升了42.8%,22.5%,9.5%。

Precision Analysis of BeiDou Satellites Broadcast Ephemeris

In order to analyze the accuracy of the BDS broadcast ephemeris, the laser ranging and precise ephemeris are used as the reference to do some analysis. Since there is no BDS-3 experimental satellite precise ephemeris, this paper designs the DBS-3 experimental satellite precise orbit determination experiment with a 3-day arc, and the results show that the orbit and clock offsets accuracies are about 50cm and 2ns respectively. Then combined with the BDS-2 post precision satellites ephemeris obtained from the international GNSS monitoring & assessment system (iGMAS), to evaluate the accuracy of the BDS-3/BDS-2 ephemeris-clock and ephemeris-orbit, in order to evaluate the ephemeris-orbit more accurately, the SLR observation data is used as an external means to evaluate the BDS satellite ephemeris-orbit accuracy, the 1d RMS of the ephemeris-orbit and the STD of ephemeris-clock are counted, and the results show that most clock accuracies are better than 10 ns, the orbit accuracy is better than 5 m. In addition, in order to analyze the time-frequency performance of the ephemeris-clock, the frequency stability, the drift rate and the accuracy of the satellite clock offset are calculated. The experimental results show that the performance of the BDS-3 test satellites is generally better than that of the BDS-2. The performance indicators of the frequency accuracy, frequency drift rate and frequency stability calculated show that the BDS-3 satellite increases by 42.8%, 22.5% and 9.5% compared with the BDS-2.