Short-term(up to 30 days)predictions of Earth Rotation Parameters(ERPs)such as Polar Motion(PM:PMX and PMY)play an essential role in real-time applications related to high-precision reference frame conversion.Currentl...Short-term(up to 30 days)predictions of Earth Rotation Parameters(ERPs)such as Polar Motion(PM:PMX and PMY)play an essential role in real-time applications related to high-precision reference frame conversion.Currently,least squares(LS)+auto-regressive(AR)hybrid method is one of the main techniques of PM prediction.Besides,the weighted LS+AR hybrid method performs well for PM short-term prediction.However,the corresponding covariance information of LS fitting residuals deserves further exploration in the AR model.In this study,we have derived a modified stochastic model for the LS+AR hybrid method,namely the weighted LS+weighted AR hybrid method.By using the PM data products of IERS EOP 14 C04,the numerical results indicate that for PM short-term forecasting,the proposed weighted LS+weighted AR hybrid method shows an advantage over both the LS+AR hybrid method and the weighted LS+AR hybrid method.Compared to the mean absolute errors(MAEs)of PMX/PMY sho rt-term prediction of the LS+AR hybrid method and the weighted LS+AR hybrid method,the weighted LS+weighted AR hybrid method shows average improvements of 6.61%/12.08%and 0.24%/11.65%,respectively.Besides,for the slopes of the linear regression lines fitted to the errors of each method,the growth of the prediction error of the proposed method is slower than that of the other two methods.展开更多
While the geodetic excitationχ(t)of polar motion p(t)is essential to improve our understanding of global mass redistributions and relative motions with respect to the terrestrial frame,the widely adopted method to de...While the geodetic excitationχ(t)of polar motion p(t)is essential to improve our understanding of global mass redistributions and relative motions with respect to the terrestrial frame,the widely adopted method to deriveχ(t)from p(t)has biases in both amplitude and phase responses.This study has developed a new simple but more accurate method based on the combination of the frequency-and time-domain Liouville's equation(FTLE).The FTLE method has been validated not only with 6-h sampled synthetic excitation series but also with daily and 6-h sampled polar motion measurements as well asχ(t)produced by the interactive webpage tool of the International Earth Rotation and Reference Systems Service(IERS).Numerical comparisons demonstrate thatχ(t)derived from the FTLE method has superior performances in both the time and frequency domains with respect to that obtained from the widely adopted method or the IERS webpage tool,provided that the input p(t)series has a length around or more than 25 years,which presents no practical limitations since the necessary polar motion data are readily available.The FTLE code is provided in the form of Mat Lab function.展开更多
脉冲星钟模型保持方法和脉冲星时自主保持精度是决定脉冲星时应用精度的关键。根据地球时TT发布的特点以及脉冲星自转稳定特点,提出基于滑动累积窗口的脉冲星钟模型保持方法。首先利用IPTA第2批发布的2颗脉冲星观测数据开展钟模型保持...脉冲星钟模型保持方法和脉冲星时自主保持精度是决定脉冲星时应用精度的关键。根据地球时TT发布的特点以及脉冲星自转稳定特点,提出基于滑动累积窗口的脉冲星钟模型保持方法。首先利用IPTA第2批发布的2颗脉冲星观测数据开展钟模型保持精度分析,在13年以上的时间窗口内2颗源的自转频率测量值相对于平均值波动幅度在10^(-13)Hz之内,且随着时间窗口累积增加钟参数测量精度单调提高;其次,利用观测数据分析钟模型在滑动预报下的脉冲星时自主保持精度和稳定度,J0437-4715在13.58年内自主保持的脉冲星时与TT(BIPM15)偏差的RMS(root mean square)为0.454μs,长期(13.58年)稳定度为1.77×10^(-15),J1713+0747在17.46年内保持的脉冲星时与TT(BIPM15)偏差为2.471μs,长期(17.46年)稳定度为6.62×10^(-17),相对于最佳保持脉冲星时的精度分别降低24%和0.16%,但提升了短期(<1年)稳定度,长期稳定度略有恶化。展开更多
为了提升时间传递链路的可靠性,国际权度局(Bureau International des Poids et Mesures,BIPM)自2020年起将Galileo时间比对正式作为UTC(Coordinated Universal Time)计算的备份链路,因此对接收机Galileo信号时延校准是全球各守时实验...为了提升时间传递链路的可靠性,国际权度局(Bureau International des Poids et Mesures,BIPM)自2020年起将Galileo时间比对正式作为UTC(Coordinated Universal Time)计算的备份链路,因此对接收机Galileo信号时延校准是全球各守时实验室参与UTC链路的必要工作.以德国物理技术研究院(Physikalisch-Technische Bundesanstalt,PTB)和中国科学院国家授时中心(National Time Service Center,NTSC)已校准的GPS(GlobalPositioning System)链路为参考,将PT09接收机设为参考站,对NTSC的NT02和NT05两台不同型号接收机的GalileoE3(GalileoE1&E5a)总时延进行校准并验证.结果表明:NT02和NT05GalileoE3总时延分别为74.6ns和46.5ns,校准不确定度均为3.5ns,且校准时延比较稳定;NT02和NT05校准后与其他守时实验室已校准接收机的GPSP3和GalileoE3链路的共视比对结果基本一致;以NTP3与其他实验室接收机GPSP3链路的共视比对结果为参考,其偏差均值均小于1.5ns,在校准不确定度范围内.展开更多
原子时具有较高的短期稳定度,基于毫秒脉冲星自转建立的脉冲星时具有较高的长期稳定度,两者融合可构建长短稳优势兼具的时间尺度。本文通过经典加权平均算法,初步构建一个脉冲星与原子钟融合的联合时间尺度(composite time scale,CT)。...原子时具有较高的短期稳定度,基于毫秒脉冲星自转建立的脉冲星时具有较高的长期稳定度,两者融合可构建长短稳优势兼具的时间尺度。本文通过经典加权平均算法,初步构建一个脉冲星与原子钟融合的联合时间尺度(composite time scale,CT)。基于国际权度局(BIPM)公布的TA(NTSC)-TAI原子时数据,并选取国际脉冲星计时阵(IPTA)公布的计时精度最高的4颗脉冲星,通过并列加权法和分类加权法这两种组合方式得到CT。结果表明并列加权法得到的CT相对于各脉冲星时在10年以内的稳定度改善明显,4~10年内稳定度与稳定度较高的脉冲星J0437-4715接近。分类加权法得到的CT对比并列加权的稳定度结果在采样区间两极优势明显,0.26年达到5.1×10^(-15),16.8年达到1.0×10^(-15),其中4颗星相比2颗星得到的CT于5.2年后稳定度有显著提高,且分类加权法得到的CT相对于TAI偏差更小,时间尺度更平稳。综上说明原子钟组的短稳特性可以对脉冲星钟组的短期噪声进行抑制,同时脉冲星时可提高联合时间尺度CT的长期稳定度。展开更多
氢原子钟具有较高的短期稳定度,将其作为主钟可在短期内产生高精度的本地时间信号.但氢钟存在频率漂移现象,导致其长期稳定度较差,从而影响本地时间的准确性.毫秒脉冲星自转高度稳定,借助于其长期稳定度高的特性,可定期实现对氢原子钟...氢原子钟具有较高的短期稳定度,将其作为主钟可在短期内产生高精度的本地时间信号.但氢钟存在频率漂移现象,导致其长期稳定度较差,从而影响本地时间的准确性.毫秒脉冲星自转高度稳定,借助于其长期稳定度高的特性,可定期实现对氢原子钟的频率驾驭,并对实时信号加以控制.首先分析了国际脉冲星计时阵(International Pulsar Timing Array,IPTA)第二批发布数据中四颗毫秒脉冲星的稳定度随时间的变化,同时采用哈达玛方差分析了中国科学院国家授时中心(National Time Service Center,NTSC)一台氢钟的频率稳定性能,最终给出了利用脉冲星驾驭氢原子钟频率的方法.展开更多
基金supported by National Natural Science Foundation of China,China(No.42004016)HuBei Natural Science Fund,China(No.2020CFB329)+1 种基金HuNan Natural Science Fund,China(No.2023JJ60559,2023JJ60560)the State Key Laboratory of Geodesy and Earth’s Dynamics self-deployment project,China(No.S21L6101)。
文摘Short-term(up to 30 days)predictions of Earth Rotation Parameters(ERPs)such as Polar Motion(PM:PMX and PMY)play an essential role in real-time applications related to high-precision reference frame conversion.Currently,least squares(LS)+auto-regressive(AR)hybrid method is one of the main techniques of PM prediction.Besides,the weighted LS+AR hybrid method performs well for PM short-term prediction.However,the corresponding covariance information of LS fitting residuals deserves further exploration in the AR model.In this study,we have derived a modified stochastic model for the LS+AR hybrid method,namely the weighted LS+weighted AR hybrid method.By using the PM data products of IERS EOP 14 C04,the numerical results indicate that for PM short-term forecasting,the proposed weighted LS+weighted AR hybrid method shows an advantage over both the LS+AR hybrid method and the weighted LS+AR hybrid method.Compared to the mean absolute errors(MAEs)of PMX/PMY sho rt-term prediction of the LS+AR hybrid method and the weighted LS+AR hybrid method,the weighted LS+weighted AR hybrid method shows average improvements of 6.61%/12.08%and 0.24%/11.65%,respectively.Besides,for the slopes of the linear regression lines fitted to the errors of each method,the growth of the prediction error of the proposed method is slower than that of the other two methods.
基金supported by the National Natural Science Foundation of China(grant numbers 41874025 and 41474022)。
文摘While the geodetic excitationχ(t)of polar motion p(t)is essential to improve our understanding of global mass redistributions and relative motions with respect to the terrestrial frame,the widely adopted method to deriveχ(t)from p(t)has biases in both amplitude and phase responses.This study has developed a new simple but more accurate method based on the combination of the frequency-and time-domain Liouville's equation(FTLE).The FTLE method has been validated not only with 6-h sampled synthetic excitation series but also with daily and 6-h sampled polar motion measurements as well asχ(t)produced by the interactive webpage tool of the International Earth Rotation and Reference Systems Service(IERS).Numerical comparisons demonstrate thatχ(t)derived from the FTLE method has superior performances in both the time and frequency domains with respect to that obtained from the widely adopted method or the IERS webpage tool,provided that the input p(t)series has a length around or more than 25 years,which presents no practical limitations since the necessary polar motion data are readily available.The FTLE code is provided in the form of Mat Lab function.
文摘脉冲星钟模型保持方法和脉冲星时自主保持精度是决定脉冲星时应用精度的关键。根据地球时TT发布的特点以及脉冲星自转稳定特点,提出基于滑动累积窗口的脉冲星钟模型保持方法。首先利用IPTA第2批发布的2颗脉冲星观测数据开展钟模型保持精度分析,在13年以上的时间窗口内2颗源的自转频率测量值相对于平均值波动幅度在10^(-13)Hz之内,且随着时间窗口累积增加钟参数测量精度单调提高;其次,利用观测数据分析钟模型在滑动预报下的脉冲星时自主保持精度和稳定度,J0437-4715在13.58年内自主保持的脉冲星时与TT(BIPM15)偏差的RMS(root mean square)为0.454μs,长期(13.58年)稳定度为1.77×10^(-15),J1713+0747在17.46年内保持的脉冲星时与TT(BIPM15)偏差为2.471μs,长期(17.46年)稳定度为6.62×10^(-17),相对于最佳保持脉冲星时的精度分别降低24%和0.16%,但提升了短期(<1年)稳定度,长期稳定度略有恶化。
文摘为了提升时间传递链路的可靠性,国际权度局(Bureau International des Poids et Mesures,BIPM)自2020年起将Galileo时间比对正式作为UTC(Coordinated Universal Time)计算的备份链路,因此对接收机Galileo信号时延校准是全球各守时实验室参与UTC链路的必要工作.以德国物理技术研究院(Physikalisch-Technische Bundesanstalt,PTB)和中国科学院国家授时中心(National Time Service Center,NTSC)已校准的GPS(GlobalPositioning System)链路为参考,将PT09接收机设为参考站,对NTSC的NT02和NT05两台不同型号接收机的GalileoE3(GalileoE1&E5a)总时延进行校准并验证.结果表明:NT02和NT05GalileoE3总时延分别为74.6ns和46.5ns,校准不确定度均为3.5ns,且校准时延比较稳定;NT02和NT05校准后与其他守时实验室已校准接收机的GPSP3和GalileoE3链路的共视比对结果基本一致;以NTP3与其他实验室接收机GPSP3链路的共视比对结果为参考,其偏差均值均小于1.5ns,在校准不确定度范围内.
文摘原子时具有较高的短期稳定度,基于毫秒脉冲星自转建立的脉冲星时具有较高的长期稳定度,两者融合可构建长短稳优势兼具的时间尺度。本文通过经典加权平均算法,初步构建一个脉冲星与原子钟融合的联合时间尺度(composite time scale,CT)。基于国际权度局(BIPM)公布的TA(NTSC)-TAI原子时数据,并选取国际脉冲星计时阵(IPTA)公布的计时精度最高的4颗脉冲星,通过并列加权法和分类加权法这两种组合方式得到CT。结果表明并列加权法得到的CT相对于各脉冲星时在10年以内的稳定度改善明显,4~10年内稳定度与稳定度较高的脉冲星J0437-4715接近。分类加权法得到的CT对比并列加权的稳定度结果在采样区间两极优势明显,0.26年达到5.1×10^(-15),16.8年达到1.0×10^(-15),其中4颗星相比2颗星得到的CT于5.2年后稳定度有显著提高,且分类加权法得到的CT相对于TAI偏差更小,时间尺度更平稳。综上说明原子钟组的短稳特性可以对脉冲星钟组的短期噪声进行抑制,同时脉冲星时可提高联合时间尺度CT的长期稳定度。
文摘氢原子钟具有较高的短期稳定度,将其作为主钟可在短期内产生高精度的本地时间信号.但氢钟存在频率漂移现象,导致其长期稳定度较差,从而影响本地时间的准确性.毫秒脉冲星自转高度稳定,借助于其长期稳定度高的特性,可定期实现对氢原子钟的频率驾驭,并对实时信号加以控制.首先分析了国际脉冲星计时阵(International Pulsar Timing Array,IPTA)第二批发布数据中四颗毫秒脉冲星的稳定度随时间的变化,同时采用哈达玛方差分析了中国科学院国家授时中心(National Time Service Center,NTSC)一台氢钟的频率稳定性能,最终给出了利用脉冲星驾驭氢原子钟频率的方法.
