Time Keeping and Time Transfer Activities at NIM

Abstract

This paper presents recent time keeping and time transfer research activities at National Institute of Metrology (NIM). In 2018, 4 more Hydrogen masers joined the NIM clock ensemble, the total relative weight of NIM clocks has been increased, and correspondingly the algorithm of UTC (NIM) has also been modified based on the new clock ensemble. With the modification of the algorithm, the performance of UTC (NIM) has been improved continuously, the deviation of UTC (NIM) from UTC has been kept within ±5 ns, and its stability has also been improved. For GNSS time and frequency transfer, NIM has done some research work based on Beidou Navigation Satellite System(BDS), BDS time transfer experiment with the NIM-made GNSS receivers on multiple baselines has been carried out in order to promote the implementation of BDS time transfer in the calculation International Atomic Time(TAI). The experiment has shown that BDS and GPS time transfer results are consistent, and less than 1 ns time stability could be achieved at some thousand seconds averaging time. For Two Way Satellite Time and Frequency Transfer(TWSTFT), NIM started to join the Europe-Asia links with satellite ABS-2a from March 2018, the very first results of NIM-PTB showed a time stability of 0.1 ns/d. NIM has operated Software-Defined Radio (SDR)Receiver since 2017 in parallel with Satre Modem, some beneficial results could be seen . For time transfer system calibration, as one of the GNSS “Group 1” (G1) laboratories designated by BIPM, NIM has organized several calibration campaigns with the NIM-made transportable calibrator. Two Way Optical fiber Time and Frequency Transfer (TWOTFT) has also been carried out continuously at NIM.