Simulation method of Probe VLBI Signal

VLBI (Very Long Baseline Interferometry)technique is an important method for orbit measurement of deep space probe. In order to research the data processing methods of the VLBI center and evaluate the measurement capability of the VLBI system, at present the routine method is observing actual deep space probe by carrying out large observation experiment to get probe signal that is received by VLBI terminals. Compared with actual observation, simulating probe signal based on the characteristics of the track and beacon is a better choice. The actual downlink signal is radio-frequency signal, which will be converted to intermediate-frequency signal, then collected by receiver. In simulation, we construct the intermediate-frequency signal directly to reduce the amount of calculation, and generate the digital terminal signal via resampling. Because of the relative motion between the probe and the VLBI station, the frequency of the signal shifts accordingly, which is called Doppler effect. To simulate the actual probe signal, we build the delay model, and investigate the simulation method about the Doppler effect of the typical point frequency signal and finite bandwidth signal. By comparing the simulated signal with the actual signal received by VLBI terminal, and analyzing the VLBI correlation result, the feasibility of the simulation method is verified, which paves the road for the following VLBI application in the moon and Mars.