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
Satellite laser ranging(SLR)is an unambiguous measurement technique and generates high accuracy satellite orbit data.All satellites in the BeiDou navigation satellite system(BDS)carried laser retro-reflector arrays(LR...Satellite laser ranging(SLR)is an unambiguous measurement technique and generates high accuracy satellite orbit data.All satellites in the BeiDou navigation satellite system(BDS)carried laser retro-reflector arrays(LRAs),so they can be tracked by ground SLR stations in order to provide the accurate observation data.The Shanghai astronomical observatory(SHAO)designed the LRAs,and also developed the dedicated SLR systems using a 1 m-aperture telescope and a transportable cabin-based SLR system with a telescopes of 60 cm aperture.These enable BDS satellite ranging during daytime and nighttime with centimeter-level precision,allowing highly accurate estimations of satellite orbits.Moreover,some of the BDS satellites are also equipped with laser time transfer(LTT)payloads,which were developed by the SHAO and China Academy of Space Technology(CAST),providing a highly accurate time comparison between the satellites and ground clocks.This paper describes the dedicated SLR system and the design of the LRAs for BDS satellites,as well as global SLR measurements.The SLR tracking data is used for evaluating the orbit accuracy of BDS satellites and broadcast ephemeris,with an accuracy of less than 1 m.The LTT measurements to BDS satellites for a single shot have a precision of approximately 300 picoseconds,with a time stability of 20 picoseconds in 500 s.展开更多
An improved measurement algorithm, based upon the theory of two-way time transfer （ TWTT）, is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on...An improved measurement algorithm, based upon the theory of two-way time transfer （ TWTT）, is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on a relative motion model of two satellites, and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed. Theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm, the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization, and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger.展开更多
For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve t...For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve the time synchronization problem in the Naval Ship Formation. After expounding the principle and system composition of TWMTT method, the various factors influencing the synchronous precision are analyzed, such as time-interval measurement error, TWMTT equipment delay error, signal propagation error in air, and signal delay error caused by shipping. To improve the time synchronization precision, all the error sources above are deduced with mathematical measures to definite the critical one, and the signal processing measures such as Pseudo code spread spectrum time comparison signal generation technology, FFT fast acquisition technology and precise tracking technology are used into the modem which is the core equipment of the TWMTT. And, calibration method of TWMTT equipment delay are developed. Through theoretical a- nalysis and simulation verification, the precision of shipboard two-way microwave time synchroniza- tion can reach 1 ns.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
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 BDS and the National Natural Science Foundation of China(Grant No.11503068,U1631240)Shanghai Key Laboratory of Space Navigation and Position Techniques(Grant No.06DZ2101)+2 种基金CAS Key Technology Talent ProgramNatural science fund of Shanghai(20ZR1467500)the Key Research Program of the Chinese Academy of Sciences(ZDRW-KT-2019-3-6)。
文摘Satellite laser ranging(SLR)is an unambiguous measurement technique and generates high accuracy satellite orbit data.All satellites in the BeiDou navigation satellite system(BDS)carried laser retro-reflector arrays(LRAs),so they can be tracked by ground SLR stations in order to provide the accurate observation data.The Shanghai astronomical observatory(SHAO)designed the LRAs,and also developed the dedicated SLR systems using a 1 m-aperture telescope and a transportable cabin-based SLR system with a telescopes of 60 cm aperture.These enable BDS satellite ranging during daytime and nighttime with centimeter-level precision,allowing highly accurate estimations of satellite orbits.Moreover,some of the BDS satellites are also equipped with laser time transfer(LTT)payloads,which were developed by the SHAO and China Academy of Space Technology(CAST),providing a highly accurate time comparison between the satellites and ground clocks.This paper describes the dedicated SLR system and the design of the LRAs for BDS satellites,as well as global SLR measurements.The SLR tracking data is used for evaluating the orbit accuracy of BDS satellites and broadcast ephemeris,with an accuracy of less than 1 m.The LTT measurements to BDS satellites for a single shot have a precision of approximately 300 picoseconds,with a time stability of 20 picoseconds in 500 s.
基金Supported by the National High Technology Research and Development Program of China(2012AA1406)
文摘An improved measurement algorithm, based upon the theory of two-way time transfer （ TWTT）, is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on a relative motion model of two satellites, and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed. Theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm, the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization, and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger.
基金Supported by the Ministerial Level Foundation(2102812)
文摘For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve the time synchronization problem in the Naval Ship Formation. After expounding the principle and system composition of TWMTT method, the various factors influencing the synchronous precision are analyzed, such as time-interval measurement error, TWMTT equipment delay error, signal propagation error in air, and signal delay error caused by shipping. To improve the time synchronization precision, all the error sources above are deduced with mathematical measures to definite the critical one, and the signal processing measures such as Pseudo code spread spectrum time comparison signal generation technology, FFT fast acquisition technology and precise tracking technology are used into the modem which is the core equipment of the TWMTT. And, calibration method of TWMTT equipment delay are developed. Through theoretical a- nalysis and simulation verification, the precision of shipboard two-way microwave time synchroniza- tion can reach 1 ns.
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.
文摘在高精度远距离时间传递中,设备时延是影响时间传递精度的重要因素之一.本文以卫星双向时间传递的SATRE Modem发射时延的测量为例,给出了一种BPSK调制系统时延的高精度测量方法.并对国家授时中心卫星双向比对所采用的SATRE Modem的发射时延进行了测量,测量结果与国外同行的测量结果符合度优于3.5 ns.
