GPS卫星钟的特性与预报研究

Study of GPS satellite clock's behaviors and prediction

经实验分析发现:GPS卫星钟差的预报精度与卫星的种类密切相关,最近发射的BLOCK ⅡR和BLOCKIIR-M类卫星比以往的BLOCK ⅡA类卫星要更加稳定,其卫星钟差的预报精度明显较高。直接利用IGS超快速产品和线性模型预报后6小时的卫星钟差,精度在0.5纳秒水平;但一些BLOCK ⅡA类卫星是不稳定的,通过对其预报残差的分析发现:同一颗卫星每天在相同时段用相同的模型去预报其卫星钟差,预报所得的残差呈周期性变化,并且这种周期性变化并不完全重合,还具有一定的随机性。依据这一特性本文构建了一个新的预报模型来实时预报GPS卫星钟差。该模型不仅能预报卫星钟差的总体变化趋势,还能预报残差的周期性变化以及随机项的变化,因此精度更高。预报结果均与IGS发布的最终产品相比,实验显示利用该方法实时预报GPS卫星钟差,预报精度可达0.5纳秒水平。

By intensively analyzing recent years IGS SCE data, the author found that the precision of predicting GPS SCE is obviously dependent on the stability of the individual satellite clock. The most recent GPS satellites （BLOCK IIR and BLOCK//R-M） are more stable than the former GPS satellites （BLOCK IIA） . In this paper, the author easily predicted their next 6 hours SCE with LM and IGS ultra rapid products （URP） . However, some of BLOCK IIA satellites clocks are instable. Therefore, the paper further analyzed their residuals and found that its residuals showed periodicity together with randomness. Then it suggested a new model for realtime SCE prediction. This model could predict not only the overall trend of SCE, but also the changing of periodic and random terms. Based on the new model and IGS URP, the SCE predicted precisions better than 0. 5ns in real time.