实时精密卫星钟轨完好性服务初步性能评估

Preliminary Performance Evaluation of Integrity Service for Real-Time Precise Satellite Orbit and Clock

  • 摘要: 实时精密卫星钟轨修正产品是实时精密单点定位(real-time precise point positioning,RT-PPP)的基础支撑信息,卫星钟轨修正产品异常将导致RT-PPP导航定位结果不再可靠,严重制约RT-PPP在生命安全相关领域的应用。传统针对RT-PPP完好性监测的研究主要关注于用户终端,要求用户终端承担较多的完好性预算并具备较强的计算能力,未完全发挥云端主控站在实时完好性监测层级的作用。针对此,构建播发前-播发后协同的实时精密卫星钟轨完好性服务架构,通过多站联合的异常检测与完好性边界评估,生成满足完好性风险与连续性风险需求的完好性信息,并实时播发给服务用户,形成实时精密卫星钟轨完好性服务。基于所构建山东省完好性监测站网实时数据流,提供实时精密卫星钟轨完好性服务,并以欧洲定轨中心产品为参考,评估完好性服务性能。实验结果表明,播发实时卫星钟轨质量标识可有效刻画实时卫星钟轨修正产品误差,完好性监测的可用性优于99.99%。

     

    Abstract:
    Objectives Integrity monitoring is essential for ensuring the reliability of real-time precise point positioning. Traditional studies mainly focus on user-level integrity monitoring, whereas the master station is primarily responsible for determining the integrity parameters required for user-level integrity monitoring. This approach places a substantial integrity-monitoring burden on users and requires considerable computational resources, thereby failing to fully exploit the role of the master station in integrity monitoring. Currently, several analysis centers publicly provide real-time precise satellite orbit and clock correction products. The standard defined by radio technical commission for maritime services (RTCM) has reserved message fields for broadcasting the integrity information of satellite orbit and clock correction products. However, to the best of our knowledge, no analysis center currently provides public integrity services for real-time precise satellite orbit and clock correction products.
    Methods This paper develops a pre- and post-broadcast integrity monitoring architecture for real-time precise satellite orbit and clock correction products. First, a quality indicator is determined using the cumulative distribution function overbounding approach. Then, a multi-station cooperative monitoring strategy, including fault detection and integrity bound evaluation, is developed. The quality indicator is evaluated to ensure compliance with the required integrity and continuity risk requirements. Finally, the integrity information is encoded into RTCM messages and broadcast to users through networked transport of RTCM via internet protocol.
    Results Based on the data stream from the integrity monitoring network established in Shandong Province and the real-time correction products provided by Centre National d'Études Spatiales, integrity services for real-time precise satellite orbit and clock correction products are generated. The performance of the proposed integrity service is preliminarily evaluated using the final satellite orbit and clock products provided by Center for Orbit Determination in Europe as the reference. The experimental results show that the availability of integrity monitoring for real-time precise satellite orbit and clock correction products exceeds 99.99%.
    Conclusions The quality indicator provided by the proposed integrity service can effectively characterize the errors in real-time precise satellite orbit and clock correction products.

     

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