An accurate measurements of lunar gravity fields by the differential VLBI technique

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A new approach to investigation of lunar interior was conducted by this project, and the results will be applied to the mission of Japanese lunar exploration project SELENE. The main results are,1) The new VLBI technique by receiving several frequency signals with narrow bands was developed in stead of conventional wide band VLBI technique. It will provide us the accurate lunar gravity field at the edge of the Moon and the structure of lunar crust in SELENE project.2) A 4-way Doppler frequency method by relaying a stable signal between lunar orbiter through the relay satellite was investigated to obtain the first gravity field map in the lunar far side. This method is applied to one of the SELENE missions.3) It was found that the Doppler caused by satellite spin is one of the serious error sources in Doppler measurements.4) The new orbit determination software by using both Doppler and VLBI data was developed under the cooperation with NASA/GSFC.5) Lunar free-air gravity anomaly and the distribution of Moho around craters were derived by inversion of Doppler. These new observation and analysis methods contribute lunar and planetary explorations in the near future.