Three functional models, polynomial, spectral analysis, and modified AR model, are studied and compared in fitting and predicting clock deviation based on the data sequence derived from two-way satellite time and freq...Three functional models, polynomial, spectral analysis, and modified AR model, are studied and compared in fitting and predicting clock deviation based on the data sequence derived from two-way satellite time and frequency transfer. A robust equivalent weight is applied, which controls the significant influence of outlying observations. Some conclusions show that the prediction precision of robust estimation is better than that of LS. The prediction precision calculated from smoothed observations is higher than that calculated from sampling observations. As a count of the obvious period variations in the clock deviation sequence, the predicted values of polynomial model are implausible. The prediction precision of spectral analysis model is very low, but the principal periods can be determined. The prediction RMS of 6-hour extrapolation interval is Ins or so, when modified AR model is used.展开更多
Time synchronization between ground and satellites is a key technology for satellite navigation system. With dual-channel satellite, a method called Two-Way Common-View(TWCV) satellite time transfer for Compass system...Time synchronization between ground and satellites is a key technology for satellite navigation system. With dual-channel satellite, a method called Two-Way Common-View(TWCV) satellite time transfer for Compass system is proposed, which combines both characteristics of satellite common-view and two-way satellite-ground time transfer. By satellite-ground two-way pseudo-range differencing and two stations common-view differencing, this TWCV method can completely eliminate the influence of common errors, such as satellite clock offset, ephemeris errors, troposphere delay and station coordinates errors. At the same time, ionosphere delay related to signal frequency is also weakened significantly. So the precision of time transfer is improved much more greatly than before. In this paper, the basic principle is introduced in detail, the effect of major errors is analyzed and the practical calculation model in the Earth-fixed coordinate system for this new method is provided. Finally, experiment analysis is conducted with actual Compass observing data. The results show that the deviation and the stability of the satellite dual channel can be better than 0.1 ns, and the accuracy of the two-way common-view satellite time transfer can achieve 0.4 ns. All these results have verified the correctness of this TWCV method and model. In addition, we compare this TWCV satellite time transfer with the independent C-band TWSTFT(Two-Way Satellite Time and Frequency Transfer). It shows that the result of the TWCV satellite time transfer is in accordance with the C-band TWSTFT result, which further suggests that the TWCV method is a remote high precision time transfer technique. The research results in this paper are very important references for the development and application of Compass satellite navigation system.展开更多
时间频率传递的结果会受到非模型化误差和观测噪声的影响,其噪声常为高频信号,构建低通滤波器可在一定程度上消除观测值序列中的高频噪声信号.本文对Vondrak滤波函数的本质进行剖析,通过IGG3算法对钟差序列进行定权并采用频率响应法选...时间频率传递的结果会受到非模型化误差和观测噪声的影响,其噪声常为高频信号,构建低通滤波器可在一定程度上消除观测值序列中的高频噪声信号.本文对Vondrak滤波函数的本质进行剖析,通过IGG3算法对钟差序列进行定权并采用频率响应法选择适合的滤波因子;对不同的链路分别进行卫星双向时间频率传递(two-way satellite time and frequency transfer,TWSTFT)、基于软件接收机的卫星双向时间传递(two-way satellite time and frequency transfer based on software defined receiver,SDR-TWSTFT)和短基线共视时间频率传递实验,并对钟差结果采用抗差Vondrak滤波进行平滑去噪.结果表明:滤波后的钟差序列能够很好地反映原始钟差序列的趋势;平滑后的TWSTFT钟差结果,日波动效应得到了有效的抑制,精度有明显提升;对于共视钟差结果,精度有明显提升,与精密单点定位(precise point positioning,PPP)时间传递结果的差值保持在−1.0~1.0 ns范围内.展开更多
卫星信道租赁费是目前卫星双向时间传递(Two-Way Satellite Time and Frequency Transfer, TWSTFT)的主要成本之一.在2017年5月以前,参与UTC (Coordinated Universal Time)计算的亚洲-欧洲实验室之间进行Ku波段卫星双向时间频率传递一...卫星信道租赁费是目前卫星双向时间传递(Two-Way Satellite Time and Frequency Transfer, TWSTFT)的主要成本之一.在2017年5月以前,参与UTC (Coordinated Universal Time)计算的亚洲-欧洲实验室之间进行Ku波段卫星双向时间频率传递一直使用2.5 Mcps/s码速率,带宽为2.5 MHz的伪随机码.为了在不影响时间频率传递性能的前提下降低成本,在欧亚间首次尝试采用1 Mcps/s码速率,带宽为1.7 MHz的伪随机码,进行亚欧卫星双向时间传递.并使用已校准的GPS PPP (Global Position System Precise Point Positioning)链路为双向链路进行间接校准.选择2018年12月的TWSTFT链路数据,分析链路性能发现,通过ABS-2A卫星,使用1 Mcps/s码速率构建的卫星双向时间比对链路的日频率稳定度达到10^-15,时间稳定度优于0.3 ns.与已校准的GPS PPP链路数据进行验证分析,结果表明,使用1 Mcps/s码速率进行超长距离卫星双向时间传递与已校准的GPS PPP时间传递结果一致,与传统手段相比,其系统造价低,时间传递性能可以满足国际原子时计算的需求.展开更多
基金Supported by the National Natural Science Foundations of China （No. 40474001, No. 40274002, No. 40604003）.
文摘Three functional models, polynomial, spectral analysis, and modified AR model, are studied and compared in fitting and predicting clock deviation based on the data sequence derived from two-way satellite time and frequency transfer. A robust equivalent weight is applied, which controls the significant influence of outlying observations. Some conclusions show that the prediction precision of robust estimation is better than that of LS. The prediction precision calculated from smoothed observations is higher than that calculated from sampling observations. As a count of the obvious period variations in the clock deviation sequence, the predicted values of polynomial model are implausible. The prediction precision of spectral analysis model is very low, but the principal periods can be determined. The prediction RMS of 6-hour extrapolation interval is Ins or so, when modified AR model is used.
基金supported by the National Natural Science Foundation of China(Grant No.41174027)the National High-tech Research and Development Program(863 Program)(Grant No.2013AA122402)
文摘Time synchronization between ground and satellites is a key technology for satellite navigation system. With dual-channel satellite, a method called Two-Way Common-View(TWCV) satellite time transfer for Compass system is proposed, which combines both characteristics of satellite common-view and two-way satellite-ground time transfer. By satellite-ground two-way pseudo-range differencing and two stations common-view differencing, this TWCV method can completely eliminate the influence of common errors, such as satellite clock offset, ephemeris errors, troposphere delay and station coordinates errors. At the same time, ionosphere delay related to signal frequency is also weakened significantly. So the precision of time transfer is improved much more greatly than before. In this paper, the basic principle is introduced in detail, the effect of major errors is analyzed and the practical calculation model in the Earth-fixed coordinate system for this new method is provided. Finally, experiment analysis is conducted with actual Compass observing data. The results show that the deviation and the stability of the satellite dual channel can be better than 0.1 ns, and the accuracy of the two-way common-view satellite time transfer can achieve 0.4 ns. All these results have verified the correctness of this TWCV method and model. In addition, we compare this TWCV satellite time transfer with the independent C-band TWSTFT(Two-Way Satellite Time and Frequency Transfer). It shows that the result of the TWCV satellite time transfer is in accordance with the C-band TWSTFT result, which further suggests that the TWCV method is a remote high precision time transfer technique. The research results in this paper are very important references for the development and application of Compass satellite navigation system.
文摘时间频率传递的结果会受到非模型化误差和观测噪声的影响,其噪声常为高频信号,构建低通滤波器可在一定程度上消除观测值序列中的高频噪声信号.本文对Vondrak滤波函数的本质进行剖析,通过IGG3算法对钟差序列进行定权并采用频率响应法选择适合的滤波因子;对不同的链路分别进行卫星双向时间频率传递(two-way satellite time and frequency transfer,TWSTFT)、基于软件接收机的卫星双向时间传递(two-way satellite time and frequency transfer based on software defined receiver,SDR-TWSTFT)和短基线共视时间频率传递实验,并对钟差结果采用抗差Vondrak滤波进行平滑去噪.结果表明:滤波后的钟差序列能够很好地反映原始钟差序列的趋势;平滑后的TWSTFT钟差结果,日波动效应得到了有效的抑制,精度有明显提升;对于共视钟差结果,精度有明显提升,与精密单点定位(precise point positioning,PPP)时间传递结果的差值保持在−1.0~1.0 ns范围内.
文摘卫星信道租赁费是目前卫星双向时间传递(Two-Way Satellite Time and Frequency Transfer, TWSTFT)的主要成本之一.在2017年5月以前,参与UTC (Coordinated Universal Time)计算的亚洲-欧洲实验室之间进行Ku波段卫星双向时间频率传递一直使用2.5 Mcps/s码速率,带宽为2.5 MHz的伪随机码.为了在不影响时间频率传递性能的前提下降低成本,在欧亚间首次尝试采用1 Mcps/s码速率,带宽为1.7 MHz的伪随机码,进行亚欧卫星双向时间传递.并使用已校准的GPS PPP (Global Position System Precise Point Positioning)链路为双向链路进行间接校准.选择2018年12月的TWSTFT链路数据,分析链路性能发现,通过ABS-2A卫星,使用1 Mcps/s码速率构建的卫星双向时间比对链路的日频率稳定度达到10^-15,时间稳定度优于0.3 ns.与已校准的GPS PPP链路数据进行验证分析,结果表明,使用1 Mcps/s码速率进行超长距离卫星双向时间传递与已校准的GPS PPP时间传递结果一致,与传统手段相比,其系统造价低,时间传递性能可以满足国际原子时计算的需求.
