First results of real-time time and frequency transfer using GPS code and carrier phase observations

We have used code and carrier phase data from the global positioning system (GPS) satellites to estimate time differences between atomic clocks in near (<10 s) real-time. For some sites we have used data transmitted via Internet connections and TCP/IP, while for other sites data were collected in deferred time, but processed by a Kalman filter-based software as if they were available in real time. Satellite orbit and clock data of different quality have been used. The real-time estimates of time differences of the station clocks have been compared to those estimated from regular postprocessing using accurate satellite orbits and clocks from the international GPS service (IGS). First results show that the standard deviation of the differences between the real-time carrier phase-based and the postprocessing estimates of the clock time differences can be less than 100 ps for baselines of about 1000 km.