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

月球背面覆盖着高地，而月球背面则由盆地组成。这种区分被称为二分法。如果这种二分法不仅出现在月球表面，而且也出现在岩石圈中，那么我们对月球的热历史就有了新的认识。大地测量是本次研究的目标，它为我们提供了月球岩石圈等内部结构。将四路多普勒和差分多普勒两种新方法应用于日本月球探测器SELENE进行月球大地测量。为测量开发了仪器和软件。3年的研究结果如下：(1)利用中继卫星完成4路多普勒方法。这种方法首次实现了对月球背面的多普勒测量。(2)完成了一种差分VLBI方法。它有可能以20厘米的精度确定卫星在月球周围的位置。(3)开发了SELENE将获得的数据约简分析软件。利用该软件可以对月球重力异常进行估计。(4)探索月球内部结构的未来计划也被研究。

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.