北斗系统长期空间信号测距精度评估及精度提升分析

Assessment of long-term BDS signal-in-space range error and its improvement

基于后处理精密产品,评估了2015-06-01—2018-06-30北斗广播星历的性能精度.对北斗系统性能精度评估的基准问题进行了讨论,统计分析了北斗系统不同星座卫星的轨道差值与星钟差值的长期变化趋势,表明北斗系统空间信号测距精度有逐年提升的趋势.还发现北斗广播星历在2017-01-17前后做出的调整具有较好的效果,不同卫星轨道径向产生一个非零均值的偏差,分析表明该径向偏差更好地实现了轨道径向与卫星星钟参数的自洽,进而大大提高了北斗系统空间信号测距精度.并且北斗系统在2017-07-22对广播星历TGD参数进行了更新,提高了卫星钟差精度.采用4个MGEX测站数据的伪距单点定位验证北斗空间信号精度提升对北斗系统基本导航定位服务的影响,结果表明北斗系统在2017年2次更新后,北斗基本导航定位精度在NEU三个方向分别提升41%、49%和39%.2018年1—6月的统计结果表明,目前北斗系统的IGSO卫星空间信号测距精度最高,优于0.8 m,GEO与MEO卫星次之,约为1 m.

The accuracies of Beidou broadcast ephemeris from June 1,2015 to June 30,2018 are evaluated by using post-processing precision orbit and clock products.The reference alignment problem of performance evaluation of the Beidou navigation satellite system(BDS)is discussed,and the long-term variation trend of orbit and clock difference is statistically analyzed.Statistical results show that the accuracy of signal-in-space range of BDS has been increasing year by year.The Beidou broadcast ephemeris made strategic adjustments around January 17,2017,and the radial errors of different satellites have a non-zero mean deviation.The analysis shows that the radial deviation achieves the self-consistent relationship between radial errors and satellite clock errors parameters,which greatly improves the accuracy of signal-in-space range of BDS.In addition,BDS updated the broadcast ephemeris TGD(time group delay)parameters on July 22,2017,which improved the accuracy of clock errors.To assess the effect of signal-in-space range error improvement,point positioning at four MGEX stations was performed.Results show that the positioning accuracies are improved by about 41%,49%and 39%in N,E,U,respectively.The statistical results in the first half of 2018 show that the SISRE inclined geosynchronous orbit(IGSO)satellite of BDS is the highest,better than 0.8 m,followed by geostationary orbit(GEO)and medium earth orbit(MEO)satellites,about 1 m.