时间比对融合算法分析与比较

为提升高精度时间比对的可靠性, 结合卫星双向时间比对(Two-Way Satellite Time and Frequency Transfer, TWSTFT)和GPS精密单点定位(Precise Point Positioning, PPP)时间比对长短稳特性, 利用稳定度加权、Vondrák-vCepek组合滤波以及 Kalman滤波融合方法对中国科学院国家授时中心(National Time Service Center, NTSC)和德国物理技术研究院(Physikalisch-Technische Bundesanstalt, PTB)间的TW-STFT和GPS PPP时间比对结果进行了融合处理并对3者进行了比较分析. 结果表明, 3种融合算法对于TWSTFT中的周日效应以及GPS PPP结果的``天跳''现象都有不同程度的改善, 融合结果与GPS PPP链路差值(Double Clock Difference, DCD)结果的绝对值保持在链路校准的不确定度范围内. 3者1d的时间和频率稳定度可以达到亚纳秒和10^-15量级, Vondrák-vCepek融合方法1d以内的稳定度最高, 适用于对短稳要求高的时间比对链路的融合. 稳定度加权、Kalman滤波融合保真度较好, 适用于对准确度要求高的时间比对链路融合.

Analysis and Comparison for Fusion Algorithms of Time Transfer

In order to improve the reliability of precise time comparison, this paper takes advantage of long-term stability of Two-Way Satellite Time and Frequency Transfer (TWSTFT) and short-term stability of GPS Precise Point Positioning (PPP). Stability weighting, Vondrák-vCepek combined filtering, and Kalman filtering methods are applied to fuse the TWSTFT and GPS PPP time comparison between the National Time Service Center (NTSC) and Physikalisch-Technische Bundesanstalt (PTB). The results show that the three fusion methods all improve the diurnal variations in TWSTFT and the discontinuities in GPS PPP solution, and the absolute value of the Double Clock Difference (DCD) between fusion results and PPP solution is kept within the link calibration uncertainty. The 1 d time and frequency stability of the three methods can reach the order of sub-nanosecond and 10^-15. The Vondrák-vCepek fusion method has the highest stability within 1d, which is suitable for the fusion of time comparison links with requirements for short stability. Stability weighting and Kalman filtering fusion have better fidelity, which are suitable for the fusion of time comparison links that require high accuracy.