The timescales incorporated into the Primary Frequency Standard(PFS)exhibit excellent stability and accuracy.However,during the dead time of PFS,the reliability of the timescale can be compromised.To address this issu...The timescales incorporated into the Primary Frequency Standard(PFS)exhibit excellent stability and accuracy.However,during the dead time of PFS,the reliability of the timescale can be compromised.To address this issue,a resilient timekeeping algorithm with a Multi-observation Fusion Kalman Filter(MFKF)is proposed.This algorithm fuses the frequency measurements from hydrogen masers with various reference frequency standards,including PFS and commercial cesium beam atomic clocks.The simulation results show that the time deviation and instability of the timescale generated by MFKF are improved compared to those with Kalman filtering.The experimental results demonstrate that even within 70 days of PFS dead time the resilient timescale generated by MFKF can operate reliably.Furthermore,it is theoretically proven that MFKF produces a smaller post-covariance than that with singleobservation Kalman filtering.展开更多
The BeiDou Navigation Satellite System (BDS) is essentially a precise time measurement and time synchronization system for a large-scale space near the Earth. General relativity is the basic theoretical framework for ...The BeiDou Navigation Satellite System (BDS) is essentially a precise time measurement and time synchronization system for a large-scale space near the Earth. General relativity is the basic theoretical framework for the information processing in the master control station of BDS. Having introduced the basic conceptions of relativistic space-time reference systems, the space-time references of BDS are analyzed and the function and acquisition method of the Earth Orientation Parameters (EOP) are briefly discussed. The basic space reference of BDS is BeiDou Coordinate System (BDCS), and the time standard is the BDS Time (BDT). BDCS and BDT are the realizations of the Geocentric Terrestrial Reference System (GTRS) and the Terrestrial Time (TT) for BDS, respectively. The station coordinates in the BDCS are consistent with those in International Terrestrial Reference Frame (ITRF)2014 at the cm-level and the difference in scale is about 1.1 × 10^(−8) . The time deviation of BDT relative to International Atomic Time (TAI) is less than 50 ns and the frequency deviation is less than 2 × 10^(−14) . The Geocentric Celestial Reference System (GCRS) and the solar Barycentric Celestial Reference System (BCRS) are also involved in the operation of BDS. The observation models for time synchronization and precise orbit determination are established within the GCRS framework. The coordinate transformation between BDCS and GCRS is consistent with the International Earth Rotation and Reference Systems Service (IERS). In the autonomous operation mode without the support of the ground master control station, Earth Orientation Parameters (EOP) is obtained by means of long-term prediction and on-board observation. The observa-tion models for the on-board astrometry should be established within the BCRS framework.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.41931076)the National Key Research and Development Program of China(grant number 2020YFB0505801).
文摘The timescales incorporated into the Primary Frequency Standard(PFS)exhibit excellent stability and accuracy.However,during the dead time of PFS,the reliability of the timescale can be compromised.To address this issue,a resilient timekeeping algorithm with a Multi-observation Fusion Kalman Filter(MFKF)is proposed.This algorithm fuses the frequency measurements from hydrogen masers with various reference frequency standards,including PFS and commercial cesium beam atomic clocks.The simulation results show that the time deviation and instability of the timescale generated by MFKF are improved compared to those with Kalman filtering.The experimental results demonstrate that even within 70 days of PFS dead time the resilient timescale generated by MFKF can operate reliably.Furthermore,it is theoretically proven that MFKF produces a smaller post-covariance than that with singleobservation Kalman filtering.
基金the grants from the National Natural Science Foundations of China(Grant Nos.11703065,11573054)from the Chinese Ministry of Science and Technology(No.2018YFE0118500).
文摘The BeiDou Navigation Satellite System (BDS) is essentially a precise time measurement and time synchronization system for a large-scale space near the Earth. General relativity is the basic theoretical framework for the information processing in the master control station of BDS. Having introduced the basic conceptions of relativistic space-time reference systems, the space-time references of BDS are analyzed and the function and acquisition method of the Earth Orientation Parameters (EOP) are briefly discussed. The basic space reference of BDS is BeiDou Coordinate System (BDCS), and the time standard is the BDS Time (BDT). BDCS and BDT are the realizations of the Geocentric Terrestrial Reference System (GTRS) and the Terrestrial Time (TT) for BDS, respectively. The station coordinates in the BDCS are consistent with those in International Terrestrial Reference Frame (ITRF)2014 at the cm-level and the difference in scale is about 1.1 × 10^(−8) . The time deviation of BDT relative to International Atomic Time (TAI) is less than 50 ns and the frequency deviation is less than 2 × 10^(−14) . The Geocentric Celestial Reference System (GCRS) and the solar Barycentric Celestial Reference System (BCRS) are also involved in the operation of BDS. The observation models for time synchronization and precise orbit determination are established within the GCRS framework. The coordinate transformation between BDCS and GCRS is consistent with the International Earth Rotation and Reference Systems Service (IERS). In the autonomous operation mode without the support of the ground master control station, Earth Orientation Parameters (EOP) is obtained by means of long-term prediction and on-board observation. The observa-tion models for the on-board astrometry should be established within the BCRS framework.
