基于北斗GEO卫星的精密共视时间频率传递方法

使用GNSS载波相位观测数据开展时间频率传递存在的重要问题，是整周模糊度固定问题未能很好的解决。本项目提出基于北斗GEO卫星的精密共视时间频率传递方法（PCVTFT），使用北斗GEO卫星的载波相位观测数据和北斗全球连续监测评估系统（iGMAS）产品，进行站间时间频率传递。建立PCVTFT方法数学模型，研究该方法的误差传递特性，研究多频多星情况的数据处理方法，并基于iGMAS平台开展试验研究。主要特色是固定接收机对GEO卫星一直可视，只存在首次模糊度（而MEO卫星每天2次模糊度）。这样在时间传递的时候，可有效减少模糊度数量；在频率传递的时候，便于实现任意校频周期的频率传递，不受模糊度影响。预期时间传递准确度可达亚纳秒量级，稳定度优于0.1ns。该方法不仅为高性能原子钟的国际比对提供了一种好方法，并且依托我国北斗和iGMAS来做，可以更好地满足导航、通信、深空探测等国家重要领域的需求。

An important problem in GNSS carrier-phase time and frequency transfer is that integer ambiguity resolution is not well resolved. This project proposes a method of Precise Common-view Time and Frequency Transfer (PCVTFT) based on BDS GEO satellites, which enables the between-station time and frequency transfer utilizing the carrier-phase data from BDS GEO satellites and the products of the international GNSS Monitoring and Assessment System (iGMAS). A mathematical model of the PCVTFT method will be established, and its error propagation characteristics will also be studied. The method for multi-frequency multi-satellite data processing will be investigated, and experiments are planned to be carried out on the platform the iGMAS. The proposed method benefits from the fact that the static receiver used in the study is always visible to the GEO satellites, so that the ambiguities only need to be resolved once at the beginning (for MEO satellites, twice in a day). In this way, the number of ambiguities to be resolved is decreased during the process of time transfer. This is beneficial for realizing the frequency transfer under arbitrary frequency calibration period that is unaffected by ambiguity resolution. The accuracy of the time transfer is expected to reach the sub-ns level and the stability is expected to be better than 0.1 ns. This provides a good option for international time and frequency comparison of high-performance atomic clocks, and moreover, based on BDS and iGMAS, it could better satisfy the needs of navigation, communications, deep space exploration, and other importand fields at national level.