一种顾及IGS-RTS数据接收中断的厘米级星载GPS实时定轨方法

A Centimeter-Level Real-Time Orbit Determination Method Using Space-Borne GPS Measurements Considering IGS-RTS Data Receiving Interruption

当前,在低轨导航增强、对地观测和科学应用等领域,低轨卫星对轨道参数的精度和实时性提出了更高的要求。利用国际GNSS服务组织实时服务(international global navigation satellite system service real-time service,IGS-RTS)播发的GPS卫星轨道与钟差改正数,针对极区实时改正数接收中断情况下实现厘米级星载GPS实时定轨的关键问题开展研究。首先分析了实时改正数及其短时外推引起的星历综合误差的变化特性;然后以此为依据,在星载GPS实时精密定轨数学模型中构建分段随机游走的伪模糊度参数随机模型,以减小星历综合误差对实时精密定轨的影响,从而实现厘米级精度的实时定轨。采用自主研制的实时精密定轨软件SATODS,使用GPS广播星历与CLK93实时产品,对为期一周的重力场恢复和气候实验(gravity recovery and climate experiment,GRACE)C卫星的GPS双频实测数据模拟在轨实时精密定轨处理。实验结果表明,在考虑极区改正数接收中断的情况下,所提实时精密定轨方法可以达到7.04 cm的位置精度以及0.20 mm/s的速度精度,所提方法具有可行性和有效性。

Objectives:At present,low earth orbit(LEO)satellites with missions,such as LEO navigation enhancement,earth observation and scientific application,require higher accuracy and real-time performance of orbit parameters.Because of the limitations of GPS broadcast ephemeris errors,the accuracy of traditional real-time orbit determination using space-borne GPS measurements is still a long way to catch up with real-time centimeter-level orbit demand.The use of real-time orbit and clock corrections for precise positioning applications will be extended into orbit if they are available via a satellite link to geostationary orbit(GEO)satellites.However,the data link to GEO constellation may not be available over the polar regions.Methods:The centimeter-level real-time precise orbit determination(RTPOD)method using space-borne GPS measurements with international global navigation satellite system service real-time service(IGS-RTS)data receiving interruption in the polar regions is studied.Firstly,the characteristics of ephemeris comprehensive errors caused by real-time corrections and its short-time extrapolation are analyzed.Based on the analysis,a pseudo-ambiguity is modeled as a stochastic process with piecewise random walk and estimated in the mathematical model of RTPOD to reduce the ephemeris comprehensive error,and then the centimeter-level accuracy can be realized.Finally,using GPS broadcast ephemeris and IGS-RTS products(CLK93),the onbroad RTPOD data processing for one week GPS measurements from the GRACE C satellite is simulated by the SATODS software.Results:The experimental results show that,considering the receiving interruption of real-time corrections in polar regions,the position and velocity accuracies are 7.04 cm and 0.20 mm/s,respectively.Conclusions:The proposed method is feasible and effective.