Radio Science Experiments in Chang’e Series Missions

Planetary radio science experiments have been carried out in Chinese lunar exploration missions of Chang’e-1/2/3. The astronomical VLBI technique was adopted for tracking and orbiting of the Chinese Chang’e 1 & 2 missions, and played an important role in positioning the orbit injection and hard landing. Besides the orbiters’ POD work and lander positioning work using open loop and close loop R&RR and VLBI tracking data, many other experiments have also been done. In orbiter missions, the lunar gravity field model was improved by using Chang’e-1 R&RR data, and new topographical features were discovered based on the new model. Also, the micro-wave passive method was used to study the lunar surface and sub-surface features. In extended mission of Chang’e-2, POD by R&RR and VLBI played the key role in L2 Lissajous orbit mission,and in Toutatis asteroid fly-by mission. In Chang’e-3 landing mission, a 3-way open loop lunar radio phase ranging and Doppler technique was suggested and tested. This method, called Lunar Radio Phase Ranging (LRPR) can be a new space geodetic technique to measure the station position, earth tide and rotation, lunar orbit, tide and liberation, by means of independent observation, or to work together with Lunar Laser Ranging. Also, it can be used in future Mars mission.