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Time Transfer Experiment by TCE on the ETS-VIII Satellite

Abstract : ETS-VIII, a Japanese geo-stationary satellite, launched in December 2006, has been developed to obtain the fundamental technologies for satellite positioning systems using two onboard cesium atomic clocks. At NICT, we developed Time Comparison Equipment (TCE) both onboard ETS-VIII and in the Earth station for precise time transfer between the atomic clocks on the satellite and a ground reference clock. Using code and carrier-phase data measured by TCE, the time and frequency difference between the onboard atomic clock and that on the ground is calculated by the Two-Way Satellite Ground Time and Frequency Transfer (TWSGTFT) method. Since February 2007, we have carried out the experiment to confirm the performance of TCE in orbit after the launch. As a result, we confirmed that TCE is able to measure the code phase with subnanosecond precision and measure the carrier phase with a few-picosecond precision.