Abstract
We examined various technologies on the In-situ Lunar Orientation Measurement project, in hope that the project will be selected as one of next lunar exploration missions. In this project, a physical lunar libration will be measured with the accuracy of milliarcsecond using simple and light telescope on the lunar surface, a promising candidate of the telescope is Photo Zenith Tube using a mercury Pool as reflection mirror. In this study, we excuted thermal analysis of the telescope including the mercury Pool in order to check whether it is possible to keep the mercury liquid on the lunar surface.