Research On Measurement And Calculation Of Instrument Time-Delay In TWSTFT

TWSTFT(Two-way Satellite Time and Frequency Transfer)is one of the important means to realize high precision remote time synchronization.In order to improve the accuracy of two-way satellite time and frequency transfer further,it is necessary to eliminate the influence of instrument time-delay on the TWSTFT system.The TWSTFT network of the Chinese Academy of Sciences is China’s first c-band two-way satellite time and frequency transfer [TWSTFT(C)] network which is developed and constructed by the National Time Service Center(NTSC).The network which can realize TWSTFT and time-sharing observation during the non-maneuvering period of GEO satellite consists of six observation stations that locate in the Chinese region and can track GEO satellite continuously.Because the influence of instrument time-delay is the main error sources of TWSTFT at present,precise measurement and calibration of instrument time-delay is the key to efficiently improve the time synchronization accuracy of TWSTFT(C)network.Because of the problem of time-delay calibration of the earth station instrument in Chinese Academy of Sciences TWSTFT network,this paper studied the method of TWSTFT portable station,designed the measurement scheme of TWSTFT portable station,and carried out the test of time-delay measurement of earth station instrument in Chinese Academy of Sciences TWSTFT network.Based on those,three-station triangle closure method is used to verify.Main research contents and achievements are as follows:1)This paper introduces the basic principle of two-way satellite time and frequency transfer,studies various error sources in TWSTFT,and emphatically analyzes the influence of environment temperature change and clock difference error term of earth station instrument time-delay.2)According to the characteristics of the TWSTFT network of the Chinese Academy of Sciences,a measuring scheme of TWSTFT portable station was designed.The actual instrument time-delay measurement test was carried out for 3 sets of c-band TWSTFT earth stations in xi ’an,kashi and sanya of the network.3)In this paper,a three-station triangle closure method is used for verification.The method is based on the TWSTFT link between the primary and secondary stations,and the clock difference between the two secondary stations is obtained by the difference algorithm.The triangle closure processing results of three stations show that the closed error is effectively reduced after using the calibration results of TWSTFT portable station,indicating that the TWSTFT portable station method is very effective in further eliminating the influence of delay error factors of earth station instrument.