BeiDou Time Transfer Between PTB and NTSC

GNSS time transfer is a primary method for remote atomic clock comparisons. There are four global satellite navigation systems in operation, named GPS, GLONASS, Galileo and BeiDou. To guarantee the precision, the accuracy and the robustness of Coordinated Universal Time (UTC) generation, multi-techniques strategy has been encouraged by Consultative Committee for Time and Frequency (CCTF) since 2009 for the purpose. In order to realize BeiDou Common-View time comparisons, three GNSS receivers, which can observe BeiDou satellites were installed in the National Time Service Center, Chinese Academy of Sciences (NTSC), and Physikalisch-Technische Bundesanstalt (PTB) has updated two receivers for BeiDou tracking in August 2017. PTB currently is the pivot laboratory in UTC time links. NTSC has about 40 clocks gaining a weight of more than 5-6% of the total UTC clock weight in past years. BeiDou time (BDT) is traceable to UTC through UTC(NTSC). Therefore, it has been a particular motivation to implement time comparisons by BeiDou for the connection between PTB and NTSC. The PTB-NTSC links was established by BeiDou satellites starting in August of 2017 and its time comparison result are within expectations. In order to verify the performance of a BeiDou global service, we also made some preliminary BeiDou time transfer tests between five IGS stations and NTSC.