基于LEO增强的GNSS载波相位时间传递性能分析

Performance analysis of GNSS carrier phase time transfer based on LEO enhancement

关键词:  GNSS  LEO  载波相位  时间传递  收敛  稳定度

Key words:  GNSS  LEO  Carrier phase  Time transfer  Convergence  Stability

摘要:

全球卫星导航系统(GNSS)载波相位时间传递技术是时间频率传递领域中最为重要的技术手段之一。近年来，随着低轨卫星( LEO）星座的不断发展，基于LEO增强的时间传递方法的应用研究也在逐渐开展。主要研究了基于LEO增强的GNSS载波相位时间传递方法，并对其数学模型进行了分析，利用2条国际时间传递链路的数据，对时间传递过程中的初始收敛时间和稳定性进行了定性与定量分析。实验结果表明，正向滤波处理时，GPS+LEO载波相位时间传递相较于GPS单系统在初始进入收敛阶段的速度更快，2条时间传递链路3天的单天平均收敛时间分别由3.83 min，5.83 min缩短至1.83 min，2.33 min，提升幅度分别为52.22%和60.03%。在时间传递链路频率稳定度方面，GPS+LEO时间传递链路在10 000s时间间隔内均优于GPS时间传递链路。在事后模式下，采用双向卡尔曼滤波处理策略削弱了时间传递链路初始阶段收敛过程的误差，同时结合时间传递链路频率稳定度的对比，GPS和GPS+LEO时间传递链路的频率稳定度基本保持一致，天稳定度均能达到10-15量级。

Abstract:

Global navigation satellite system (GNSS) carrier phase time transfer technology is one of the most important technical means in the field of time and frequency transfer. In recent years, with the continuous development of low Earth orbit (LEO) constellations, research on the application of LEO-enhanced time transfer methods has been gradually carried out. The GPS carrier phase time transfer method based on LEO enhancement is mainly studied and its mathematical model is analyzed. The initial convergence time and stability of the time transfer process are qualitatively and quantitatively analyzed by using data from two international time transfer links. The experimental results show that the forward filtering process of GPS+LEO carrier phase time transfer is faster than that of GPS single system in the initial convergence stage. The average daily convergence time of the two time transfer links in 3 days is reduced from 3.83 min and 5.83 min to 1.83 min and 2.33 min respectively, with an increase of 52.22% and 60.03%. In terms of the frequency stability of the time transfer link, the GPS+LEO time transfer link is superior to the GPS time transfer link within a time interval of 10 000 s. In the post-event mode, a bidirectional Kalman filter processing strategy is used to reduce the error of the convergence process of the time transfer link in the initial stage. Meanwhile, combined with the comparison of the frequency stability of the time transfer link, the frequency stability of the GPS and GPS+LEO time transfer links is basically consistent, and the daily stability can reach the order of 10-15.