System Time and Satellite Clock for New-generation BeiDou Satellites: Preliminary Results
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摘要: 北斗卫星导航系统新一代试验卫星星座由2颗高轨倾斜地球同步轨道卫星（IGSO）和3颗中轨地球轨道卫星(MEO)组成,2016年2月全部发射入轨,其任务是验证北斗系统从目前区域导航定位授时服务走向全球服务的新技术体制设计及指标性能。导航卫星星载原子钟是最重要载荷之一,负责星上时间频率基准信号维持和产生。本文利用星地双向时频传递设备观测的星地钟差数据,评估了试验星配置的新型高精度铷钟和被动型氢钟的实际性能,定量比较了相对于北斗区域系统卫星钟的性能提升。结果表明,新一代试验星与北斗区域系统卫星钟差预报精度相比较有较大提高,IGSO卫星短期预报误差从0.65 ns减小到0.30 ns,MEO卫星短期预报误差从0.78 ns减小到0.32 ns,IGSO／MEO卫星中期预报误差均从2.50 ns减小到约1.50 ns.时频系统是新一代试验系统地面运控的重要组成部分,负责北斗新一代试验系统时间频率信号产生和维持。本文利用试验系统与UTC(BSNC)之间的比对数据,评估了新一代试验系统时间的实际性能,定量比较了相对于北斗区域系统时间的性能提升。结果表明,新一代试验系统时间相对于北斗区域系统时间性能有较大提高,万秒稳和天稳较北斗区域系统提高约半个数量级。时频体制是新一代试验系统的重要技术体制设计之一。本文利用中心节点与末节点的双向时间测量数据,评估了新一代试验系统末节点时频信号的实际性能。结果表明,中心节点与末节点之间具有很好的一致性,时差最大为0.23 ns.Abstract: Five new-generation BeiDou Satellite Navigation System (BDS) satellites, including two satellites in the Inclined Geostationary Orbit (IGSO) and three satellites in the Medium Orbit (MEO), have completed deployment on 1st February 2016. The mission of the five new-generation satellites is to validate the new system designs and the new technologies that will successfully expand BDS’s Positioning, Navigation and Timing (PNT) services from regional to global. Responsible to keep time and frequency standards that are used to generate navigation signals, atomic clocks are important payloads onboard BDS satellites. Using data from BDS’ two-way satellite time and frequency transfer system, this paper evaluates performance of those new generation atomic clocks (Hydrogen Maser and Rubidium). Compared to the regional operational satellites onboard atomic clocks, the prediction accuracy of the new-generation onboard atomic clocks is improved. The short-term prediction error of IGSO satellites drops from 0.65 ns to 0.30 ns, the shortterm prediction error of MEO satellites drops from 0.78 ns to 0.32 ns, and both the media-term prediction error of both IGSO and MEO satellites drops from 2.50 ns to 1.50 ns. Time frequency system is an important part of the ground movement control of the new generation test system, which is responsible for the generation and maintenance of the time frequency signal of the new generation test system. Using the data from the new generation test system time and UTC(BSNC), this paper evaluates performance of system time in new generation test system, compared to the regional system time, the performance of new generation test system time is improved, the 1000s stability and day stability compared to the regional system improve about half an order. Central-distributed time and frequency system is the key technology in the new generation test system. Using the two-way data from center note and frontier node, this paper evaluates performance of frontier node time in new generation test system. Results show that the center note frontier note are in good consistent, with the largest value of 0.23 ns.
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