北斗星地双向时频传递与广广播钟差精度分析

与其他卫星导航系统不同,北斗卫星导航系统采用星地双向时间比对技术,直接测量卫星钟相对于地面保持的系统时间的钟差,并用于广播电文钟差参数的建模。讨论了电离层延迟误差、卫星相位中心误差等不同误差源对不同类型卫星双向时间同步卫星钟差精度的影响。实测数据分析结果表明,星地双向卫星钟差内符合精度(RMS)优于0.15 ns。利用双向卫星钟差序列,对广播星历钟差参数预报精度进行了分析,统计结果显示广播电文钟差参数预报1 h,精度在2 ns以内,移动卫星刚入境时,钟差参数预报6 h误差可达10 ns。

The Two Way Satellite-Ground Time Transfer of BDS and Accuracy Analysis of Broadcast Clock

The satellite clock parameters in broadcast ephemeris of Beidou navigation satellite system(BDS)is derived through the two-way satellite-ground time transfer(TWSTT)technique,where the satellite clock is directly measured using the ground antennas of monitoring stations.The mathematical model of BDS TWSTT is presented in this paper,and the random noise of observed data is analyzed,showing the RMS better than 0.15 ns.Modeling errors of the ionospheric delay and satellite phase centers affecting the measuring accuracy of TWSTT is analyzed.The time series of the TWSTT clocks are used to fit and predict the clock parameters.Statistical results show that accuracy of the navigation message clock parameters is up to 2 ns within 1 h,and the satellite clock error of IGSO/MEO could be 10 ns within 6 h due to the absense of TWSTT ground tracking.