Three Years of GLONASS Use for UTC

摘要

GPS has been used in accurate time transfer for near 30 years. TWSTFT (Two-Way Satellite Time and Frequency Transfer) has been applicable for the last 10 years. On the other hand, the first GLONASS satellite was launched in 1982 and became operational some years after. Although efforts have been made to use GLONASS since the 1990s, only in November 2009 was the first GLONASS time link introduced in the generation of UTC. At present, there are 6 GLONASS links contributing to UTC. This marked the start of the epoch of GNSS multi-technique time transfer in the history of UTC. In the frame of the UTC computation, we investigate the evolution of the GLONASS measurements used in UTC and the calibration uncertainties in the accurate time transfer with respect to GPS and TWSTFT. We review the advantages and disadvantages of different techniques and the combination of the two systems.