As an extension of the＂teleparallel＂equivalent of general relativity,f（T）gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modif...As an extension of the＂teleparallel＂equivalent of general relativity,f（T）gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modified gravity also has impacts on the Solar System,we might test it during future interplanetary missions with ultrastable clocks.In this work,we investigate the effects of f（T）gravity on the dynamics of the clock and its time transfer link.Under these influences,theΛ-term and theα-term of f（T）gravity play important roles.Here,Λis the cosmological constant andαrepresents a model parameter in f（T）gravity that determines the divergence from teleparallel gravity at the first order approximation.We find that the signal of f（T）gravity in the time transfer is much more difficult to detect with the current state of development for clocks than those effects on dynamics of an interplanetary spacecraft with a bounded orbit with parameters 0.5 au≤a≤5.5 au and 0≤e≤0.1.展开更多
High precision and stable clock is extremely important in communication and navigation.The miniaturization of the clocks is considered to be the trend to satisfy the demand for5G and the next generation communications...High precision and stable clock is extremely important in communication and navigation.The miniaturization of the clocks is considered to be the trend to satisfy the demand for5G and the next generation communications.Based on the concept of meter bar and the principle of the constancy of light velocity,we designed a micro clock,Space Time Clock(STC),with the size smaller than 1 mm×1 mm and the power dissipation less than 2 m W.Designed in integrated circuit of 0.18μm technology,the instability of STC is assessed to be 2.23×10^(-12)and the trend of the instability is reversely proportional toτ.With the potential ability to reach the level of 10instability on chip in the future,the period of the STC’s signal is locked on the delay time defined by the meter bar which keeps the time reference constant.Because of its superior performance,the STC is more suitable for mobile communication,PNT(Positioning,Navigation and Timing),embedded processor and deep space application,and becomes the main payload of the ASRTU satellite scheduled to launch next year and investigate in space environment.展开更多
With the increasingly high requirement of clock source accuracy for seismic data servers and equipment,the development of a multipurpose timing system is urgently needed in the seismic industry. We have developed low-...With the increasingly high requirement of clock source accuracy for seismic data servers and equipment,the development of a multipurpose timing system is urgently needed in the seismic industry. We have developed low-cost timing equipment according to the actual earthquake industry situation. This set of timing equipment can provide a unified solution to the different environment and different earthquake instruments with different timing precision demands.展开更多
A two-way satellite time and frequency transfer(TWSTFT) device equipped in the BeiDou navigation satellite system(BDS)can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method w...A two-way satellite time and frequency transfer(TWSTFT) device equipped in the BeiDou navigation satellite system(BDS)can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method with high accuracy because most system errors such as orbital error, station position error, and tropospheric and ionospheric delay error can be eliminated by calculating the two-way pseudorange difference. Another method, the multi-satellite precision orbit determination(MPOD)method, can be applied to estimate satellite clock errors. By comparison with MPOD clock estimations, this paper discusses the applications of the BDS TWSTFT clock observations in satellite clock measurement, satellite clock prediction, navigation system time monitor, and satellite clock performance assessment in orbit. The results show that with TWSTFT clock observations, the accuracy of satellite clock prediction is higher than MPOD. Five continuous weeks of comparisons with three international GNSS Service(IGS) analysis centers(ACs) show that the reference time difference between BeiDou time(BDT) and golbal positoning system(GPS) time(GPST) realized IGS ACs is in the tens of nanoseconds. Applying the TWSTFT clock error observations may obtain more accurate satellite clock performance evaluation in the 104 s interval because the accuracy of the MPOD clock estimation is not sufficiently high. By comparing the BDS and GPS satellite clock performance, we found that the BDS clock stability at the 103 s interval is approximately 10.12, which is similar to the GPS IIR.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 11103010)funded by the Natural Science Foundation of China (Grant No. 11103085)+3 种基金the Fundamental Research Program of Jiangsu Province of China (Grant No. BK20131461Grant No. BK2011553)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110091120003)the Fundamental Research Funds for the Central Universities (No. 1107020116)
文摘As an extension of the＂teleparallel＂equivalent of general relativity,f（T）gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modified gravity also has impacts on the Solar System,we might test it during future interplanetary missions with ultrastable clocks.In this work,we investigate the effects of f（T）gravity on the dynamics of the clock and its time transfer link.Under these influences,theΛ-term and theα-term of f（T）gravity play important roles.Here,Λis the cosmological constant andαrepresents a model parameter in f（T）gravity that determines the divergence from teleparallel gravity at the first order approximation.We find that the signal of f（T）gravity in the time transfer is much more difficult to detect with the current state of development for clocks than those effects on dynamics of an interplanetary spacecraft with a bounded orbit with parameters 0.5 au≤a≤5.5 au and 0≤e≤0.1.
基金National Natural Science Foundation of China(No.11973021)Harbin Institute of Technology,Research Centre of Satellite Technology and Department of Microelectronics Science and Technologysupported by the ASRTU satellite project。
文摘High precision and stable clock is extremely important in communication and navigation.The miniaturization of the clocks is considered to be the trend to satisfy the demand for5G and the next generation communications.Based on the concept of meter bar and the principle of the constancy of light velocity,we designed a micro clock,Space Time Clock(STC),with the size smaller than 1 mm×1 mm and the power dissipation less than 2 m W.Designed in integrated circuit of 0.18μm technology,the instability of STC is assessed to be 2.23×10^(-12)and the trend of the instability is reversely proportional toτ.With the potential ability to reach the level of 10instability on chip in the future,the period of the STC’s signal is locked on the delay time defined by the meter bar which keeps the time reference constant.Because of its superior performance,the STC is more suitable for mobile communication,PNT(Positioning,Navigation and Timing),embedded processor and deep space application,and becomes the main payload of the ASRTU satellite scheduled to launch next year and investigate in space environment.
基金supported by the Xinjiang Earthquake Science Foundation(201308)
文摘With the increasingly high requirement of clock source accuracy for seismic data servers and equipment,the development of a multipurpose timing system is urgently needed in the seismic industry. We have developed low-cost timing equipment according to the actual earthquake industry situation. This set of timing equipment can provide a unified solution to the different environment and different earthquake instruments with different timing precision demands.
基金supported by the National Natural Sciences Foundation of China(Grant No.41574029)Youth Innovation Promotion Association CAS(Grant No.2016242)
文摘A two-way satellite time and frequency transfer(TWSTFT) device equipped in the BeiDou navigation satellite system(BDS)can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method with high accuracy because most system errors such as orbital error, station position error, and tropospheric and ionospheric delay error can be eliminated by calculating the two-way pseudorange difference. Another method, the multi-satellite precision orbit determination(MPOD)method, can be applied to estimate satellite clock errors. By comparison with MPOD clock estimations, this paper discusses the applications of the BDS TWSTFT clock observations in satellite clock measurement, satellite clock prediction, navigation system time monitor, and satellite clock performance assessment in orbit. The results show that with TWSTFT clock observations, the accuracy of satellite clock prediction is higher than MPOD. Five continuous weeks of comparisons with three international GNSS Service(IGS) analysis centers(ACs) show that the reference time difference between BeiDou time(BDT) and golbal positoning system(GPS) time(GPST) realized IGS ACs is in the tens of nanoseconds. Applying the TWSTFT clock error observations may obtain more accurate satellite clock performance evaluation in the 104 s interval because the accuracy of the MPOD clock estimation is not sufficiently high. By comparing the BDS and GPS satellite clock performance, we found that the BDS clock stability at the 103 s interval is approximately 10.12, which is similar to the GPS IIR.
