卫星导航系统时间溯源新方法研究

The system times of GNSS are all steered to the local realization of UTC. The time difference between GNSS system time and UTC(K) are broadcast in the navigation message of satellites. Currently, this difference is monitor by the common view or TWSTF links between the system time and UTC(K). Based on the analysis of error distribution in the generation of time difference, a new method for the acquisition this difference is proposed. The time difference is directly monitor at the timing laboratory which has been steered to the UTC with receivers. And the difference between the system time that broadcast by each satellite and the UTC (K) is analyzed and modeled. . The parameters that generated from the difference not only contain the time difference between system time and UTC(K) but also effects by the errors in the one-way timing which can be canceled with the errors in the user receiving results. This not only can enhance the timing accuracy but also the positioning accuracy. . In another aspect, the GEO satellites are different from MEO. It is necessary to make use of the advantages of GEO satellite in time transfer.

卫星导航系统的时间都需要溯源到UTC，并在导航电文中广播溯源模型参数。目前，所有的卫星导航系统的溯源方式都是正向的直接比对，通过系统时间与UTC(K)的比对获得系统时间与UTC偏差。在对直接比对溯源误差分布规律进行研究的基础上，提出了逆向接收溯源的新方法。在与UTC有溯源链路的守时实验室接收卫星导航系统的授时信号，分析卫星广播时间与UTC(K)的偏差，根据偏差变化规律计算时间溯源模型。. 这样计算的溯源模型，不但实现了系统时间与UTC的偏差的测量，还包含系统授时的误差，用户在使用过程中相当于进行了一次差分，不但可以将授时精度由目前的10ns量级提高到3ns量级，还可以提高定位精度。. 需要对这种溯源方法进行深入研究，针对GEO和MEO的特点，分析逆向接收溯源方法的误差传播规律，提出有针对性的解决办法，最大发挥GEO卫星在时间传递方面的优势。

目前卫星导航系统的授时精度最高只有十几纳秒，无法满足用户对纳秒级时间精度的需求。为此，本项目提出一种纳秒级的授时方法，只需改变北斗系统的溯源参数产生方式即可。通过在用户端监测配置高精度监测接收机，在用户端监测授时偏差，该偏差中不仅反应了卫星导航系统时间与标准时间的偏差，同时也包含了传输路径延迟误差。将监测值广播给用户，使用后可进一步抵消用户授时中的各项误差源。在喀什、三亚等地的测试结果表明基于该方法可以实现优于5ns的授时，验证了该方法的可行性。该方法的提出填补了纳秒级授时方法的空白。

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