实时卫星钟差基准精化方法

在基于精密单点定位(PPP)的授时方法中,卫星钟差产品的高精度时间基准至关重要. 针对实时卫星钟差产品时间基准不够稳定的问题,本文采用一组具有原子钟外部输入的国际全球卫星导航系统(GNSS)服务(IGS)跟踪站建立了顾及原子钟变化特性的基准精化方法. 该方法首先采用阿伦方差对不同的IGS跟踪站外接原子钟进行稳定度分析,挑选出一组稳定度高的原子钟用以精化时间基准. 在此基础上,利用阿伦方差分析各台原子钟的噪声参数特征,并确定不同原子钟之间的权比关系. 最终,建立时间基准改正量的随机模型,并计算出精化后的时间基准. 通过实例验证表明:与IGS事后精密钟差产品定义的时间基准比较,改正后的实时钟差基准单天内的标准差(STD)优于0.1 ns,相比于改正前最高提升了93％. 同时,基准改正后的天内万秒稳达到10-15量级,实现了一个量级的提高. 此外,通过相对钟差精度的分析,表明钟差基准修正不影响PPP的定位精度. 

The method of refining real-time satellite clock offset reference

For timing based on PPP method, the high-accuracy time reference of satellite clock products is very important. Aiming at the problem that the time reference of real-time satellite clock products is not stable enough, this paper uses a set of IGS tracking stations with external input of atomic clock to establish a reference refinement method that takes into account the variation characteristics of atomic clocks. Firstly, we analyze the stability of the external atomic clock of the IGS tracking station based on Allan variance, and select highly stable atomic clocks to correct the time reference. On this basis, the Allan variance is used to calculate the noise parameters of each atomic clock and the corresponding weight ratio relationship. Finally, this paper establishes a stochastic model of time reference corrections and calculates the time reference after refinement. By comparing with the time reference implied by the IGS precision clock products, the STD of the corrected time reference is better than 0.1 ns in a single day, up to 93％ compared to before the correction. At the same time, the long-term stability at 10 000 s can reach the level of 10-15, achieving an order of magnitude improvement.