Time Comparisons by GPS C/A, GPS P3, GPS L3 and TWSTFT at KRISS

We present an overview of time transfer activities at Korea Research Institute of Standards and Science (KRISS). During the last few years, we have equipped the geodetic receivers for P code and carrier phase measurements, and built two-way satellite time and frequency transfer (TWSTFT) system to improve the time comparison accuracy. Now, we are conducting the time comparisons between KRISS and National Institute of Information and Communications (NICT, Japan) including several institutes in Asia using various GPS time transfer methods such as GPS C/A code, P3 code, carrier phase, and TWSTFT techniques. The equipment for time transfers are TTR6, 3S-R100, Euro-80, and a geodetic receiver (Z12-T) for GPS link, and multi-channel TWSTFT via JCSAT-1B satellite for two-way link. From the all data, we have compared and evaluated the differences between the various comparison methods by GPS versus TWTSTF