基于光纤时频传递的北斗空间信号精度提升方法研究

The optical fiber time-frequency transfer can obtain the results of ultra-stable and high-precision time-frequency comparison between stations, and its development brings new opportunities for the service performance improvement of Beidou navigation satellite system. This project aims to provide models and algorithms to raise the performance of Beidou signal-in-space based on the optical fiber time-frequency transfer. Key issues of this project are as follows. Time-offset calibration and Sagnac relativistic correction using multi-source data for optical fiber time-frequency transfer, and multi-source clock data fusion based on robust Kalman filter, they are both for the precision improvement of time synchronization between Beidou stations. Precise orbit determination using Beidou regional network based on the generalized constraints of precise clock for the precision improvement of orbit determination with strong correlation between time synchronization and satellite orbit parameters. A software of Sagnac correction and time-delay calibration for optical fiber time-frequency transfer, and a technical scheme for accuracy improvement of Beidou signal-in-space based on optical fiber time-frequency transfer are provided. It is expected to provide new ideas for the improvement of Beidou signal-in-space accuracy, and to promote the application and development of optical fiber time-frequency transfer in the comprehensive PNT system with Beidou system as the core. This topic closely combines the social needs of the development of the Beidou navigation satellite system, and has important scientific significances and application values.

光纤时频传递能够获取超稳、高精度站间时频比对结果，其发展给北斗导航卫星系统服务性能提升带来了新的机遇。本项目拟研究利用光纤时频传递技术获取的高精度站间时间同步钟差提升北斗空间信号精度所需模型、算法的理论和方法。重点研究基于多源数据的光纤时频传递Sagnac相对论效应修正及时延偏差标定算法，以及基于抗差Kalman滤波的多源钟差数据融合算法，解决北斗站间时间同步钟差噪声大的问题；研究基于精密钟差广义约束的北斗区域网精密定轨参数估计算法，解决区域网精密定轨中时间同步与卫星轨道参数强相关所导致的定轨精度差的问题。提供一套光纤时频传递Sagnac修正及时延偏差标定软件，以及一套基于光纤时频传递的北斗空间信号精度提升方案。期望为北斗空间信号精度提升提供新思路，促进光纤时频传递在以北斗系统为核心的国家综合PNT体系中的应用与发展。课题紧密结合北斗导航卫星系统发展的社会需求，科研意义和应用价值重大。

光纤时频传递能够获取稳定、高精度站间时频比对结果，其发展给北斗导航卫星系统服务性能提升带来了新的机遇，不仅可以用做扩展的时频比对链路，还可提升时频比对精度，是以北斗系统为核心的国家综合PNT体系建设的重要组成部分。本项目研究了利用光纤时频传递技术获取的高精度站间时间同步钟差提升北斗空间信号精度所需模型、算法的理论和方法。重点研究了光纤时频传递Sagnac相对论效应修正及时延偏差标定算法，提出了基于大地主题解算的光纤链路Sagnac相对论修正计算方法，用于解决光纤路径位置信息稀少情况下的Sagnac修正，对比分析了PPP模糊度解算时频传递与光纤时频结果特征，为光纤链路时延偏差标定奠定了基础。综合分析了北斗系统站间、星间时差比对数据特征，研究了基于抗差Kalman滤波的多源钟差数据融合算法，为提升北斗站间时间同步精度奠定了算法基础。研究了基于钟差模型约束的北斗区域网精密定轨参数估计算法，利用时差数据短期相关性，探索了区域网精密定轨中时间同步与卫星轨道参数解耦方法。在上述理论方法研究的基础上，研制了一套光纤时频传递Sagnac修正及时延偏差标定软件，并进行了相关算法的应用验证，初步形成了基于光纤时频传递的北斗空间信号精度提升方案，为北斗空间信号精度提升提供了新思路，为促进光纤时频传递在以北斗系统为核心的国家综合PNT体系中的应用提供了方法支撑，部分研究成果已应用于北斗系统建设。研究目标基本全面完成，发表已标注国家自然科学基金资助的论文2篇，授权国家发明专利1项。