Estimation of gravity anomaly in the lunar far-side from VLBI and 4-Way Doppler data

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The lunar far-side is covered by highland although the lunar near side consists of basins. This differentiation is called dichotomy. If the dichotomy is shown not only in the surface but also the lithosphere, new knowledge are given about the thermal history of the Moon. The geodetic measurement, objective of this research, provides us the internal structure such as lithosphere of the Moon. Two new methods of 4-Way Doppler and differential VLB I are applied to the Japanese lunar explorer SELENE for the geodetic measurements of the Moon. Instruments and software are developed for the measurements. Research results for 3 years are shown bellow.(1)A 4-way Doppler method was completed by using a relay satellite. This method enables Doppler measurement of the far-side for the first time.(2)A Differential VLBI method was completed. It has potential to determine the position of a satellite with an accuracy of 20cm around the Moon.(3)Reduction and analysis software for data that SELENE will obtain was developed. The lunar gravity anomaly can be estimated by this software.(4)Future plans were also investigated to explore the lunar internal structure.