Delay Sability Analysis And Calibration Of IGMAS Receivers At Time Laboratories

The international GNSS Monitoring and Assessment System(iGMAS)was constructed mainly by China.It monitors and evaluates the Bei Dou/GPS/GLONASS/Galileo four satellite navigation systems by deploying tracking stations around the world.iGMAS receivers,as components of tracking stations,have important influence on the performance of iGMAS.The iGMAS receivers located at the two important time laboratories,Physikalisch-Technische Bundesanstalt(PTB)and the National Time Service Center(NTSC)of the Chinese Academy of Sciences,were analyzed in the thesis.The receivers' hardware delay was calibrated after the stability analysis.The relevant results have important application value for the Bei Dou global timing performance monitoring and evaluation using the iGMAS receivers and the Precise Timing Service(PTS)of national standard time based on the Bei Dou/GNSS.The main work and contributions of the thesis include :(1)Analysis of observation data quality.The data quality of the six iGMAS receivers participating in the experiment was analyzed from three aspects: data integrity rate,cycle slips ratio and multipath effect.The BRCH station at PTB is analyzed based on one year observation data.The complete rate of most frequency observation data is above 90%,and the multipath effect is less than 0.5 meters.Receivers at the National Time Service Center: 1)XIA4,XIA6 data integrity rate is above 95%,XIA3,XIA5,XIA9 most signals are above 90%;2)except GPS P1,GLONASS P1,BDS B1 I,the multipath effects of all other pseudorange signals of the receiver are less than 0.5 m;3)GPS and BDS signals have relatively few cycle slips,and GLONASS signals are relatively more.The abo ve results show that the data quality of the test receivers are generally good,which can support the analysis and calibration of receiver hardware delay.(2)Delay analysis and calibration of iGMAS BRCH station receiver.Based on the common clock mode,using the precise point positioning time transfer technology,the link delay between the BRCH station receiver and the PTBB receiver,which participates in the international time comparison,are calculated and analyzed.The following problems were found and solved/confirmed: 1)Some time periods are missing in the daily observation file of the BRCH station,and the receiver clock difference of the solution is abnormally dispersed.A Bernese PCF program was developed to form the complete daily observation files by combining the 15-minute observation files.All the daily observation files of BRCH station in 2018,were complemented and updated to iGMAS Xi'an Data Center;2)30th to 110 th days at 2018,The time scale of IGS rapid product is abnormal,causing the UTC(k)-IGRT clock differences sequence obtained by PPP to be diverged.The results show that the 300-day delay stability of the iGMAS BRCH station receiver is better than 0.3 ns,which is equivalent to the level of foreign commercial high-precision timing receiver.Based on the stability analysis results,the GPS signal delay of the BRCH receiver is relatively calibrated by the calibration values of the PTBB receiver published by BIPM.This part of the work serves the overseas time performance evaluation of Bei Dou global system,supporting the opening of the basic service of the Bei Dou global system at the end of 2018.(3)Time delay stability analysis and calibration of the iGMAS test receivers of the National Time Service Center.Similarly,using the common clock mode,based on the precise point positioning time transfer technology,the link delay betwee n the iGMAS receiver of the National Time Service Center and the NTP1 receiver,which participates in the international time comparison,is calculated and analyzed.The results show that: 1)iGMAS receivers XIA3 and XIA5,which are the same types,have good consistency,and the 40-day link delay stability is better than 0.5 ns,but there are 1～2 ns days deviation in some periods;2)XIA4 and XIA6,which are the same type commercial high-precision timing receivers,have good consistency,and the 40-day link delay stability is better than 0.35 ns.Based on the stability analysis results,the GPS signal link delay is relatively calibrated by means of the NTP1 receiver calibration value published by BIPM.This part of the work is directly applied to the domestic timing performance evaluation of Bei Dou global system,supporting the opening of the basic service of the Beidou global system at the end of 2018.At the same time,it provides relevant reference and delay correction for PTS,which ensures the construction and stable operation of the PTS prototype system.