A measurement method of the GEO satellite local oscillator error

Abstract

In recent years, Two-Way Satellite Time and Frequency Transfer (TWSTFT) method has been accredited as the most effective and high precision system. But as the frequency stabilities of today's sophisticated atomic-level clocks improve, so must the stability of a Two-Way system's method of time and frequency transfer. Carrier-phase information holds the promise of improving the stabilities of TWSTFT measurements, because of the great precision at which frequency transfers can be achieved. Many years ago, some scientists try to use carrier phase in TWSTFT, in the trial of time and frequency transferring between USNO and NIST station, some excited results proved the theory and showed the promise of carrier-phase measurement. But because of the poor stability of telecommunications GEO satellite local oscillator and some other factors, the result didn't review in other trial station. Then no further research reference was published. Based on TWSTFT system, a method for measuring the satellite oscillator frequency is presented. The radial velocity of the satellite relative to the main control station can be estimated from the relationship between the Doppler frequency shift and the frequency difference between the two stations. Then the satellite oscillator frequency can be calculated after one of the two Doppler frequencies has been measured. According to the results, the influence of transponder local oscillator can be relieved by pre-adjusting the transmitter clock. Two solutions are described to calculate the two stations velocities and satellite local oscillator. By present TWSTFT link, test campaign has been conducted with 10MChip/s PN code signal between Shanghai and Shaanxi.