Open Loop Velocity Measurement Scheme Design and Verification of Chang'E-4 Relay Satellite

An open loop velocity measurement scheme is proposed for the high accuracy orbit measurement mission of deep space probes. Firstly,deep space probe's downlink signal is sampled and recorded by narrow band model. Then,the probe's carrier signal is processed to extract carrier frequency based on the combining signal processing method,which contains FFT,CZT and local re-construction algorithms. Then,the probe's Doppler frequency is obtained and Doppler frequency's random noise level is estimated. Finally,thethe Doppler frequency obtained by the proposed method is compared with the Doppler frequency based on the deep space station's baseband velocity measurement and the accumulation carrier phase velocity measurement. The three types of Doppler frequency are utilized for the input observations of orbit determination system to evaluate the absolute accuracy of the three types of Doppler frequency. The real signal processing and analysis of the on-orbit CE-4 relay satellite shows that, the Doppler frequency accuracy in this paper is at the level of 10 mHz,which is better than the Doppler frequency based on the deep space station's baseband velocity measurement and the accumulation carrier phase velocity measurement. The probe high accuracy orbit determination results show thatthe velocity measurement absolute accuracy in this paper is at the level of 0.2 mm/s. The effectiveness of the open loop measurement technology is successfully evaluated for China's future deep space missions.