Lunar Interior Exploration by Japanese Lunar Penetrator Mission, LUNAR-A

Abstract

The Institute of Space and Astronautical Science (ISAS), Japan, plans to undertake a lunar mission, named as LUNAR-A, which is to be launched in 1997. The scientific objective of the mission is to explore the lunar interior using seismometry and heat-flow measurement to obtain a better understanding of the origin and evolution of the moon. The M-V, the newest version of the Mu series launch vehicles, will be used to send a 53 kg spacecraft into a lunar transfer orbit. Three penetrators containing ultra-sensitive seismometers and heat-flow probes will be deployed from a spacecraft onto the lunar surface, and will constitute a seismic and heat-flow measurement network of a much larger span than the Apollo ALSEP network. The seismic observations are expected to provide key data on the size of the lunar core and its physical properties, as well as data on deep lunar mantle structure. The heat flow measurements at three penetrator landing sites will also provide important data on thermal structure and concentrations of heat-generating elements in the moon. Combining these data, it is expected that we will be able to obtain much stronger geophysical constraints on the origin and evolution of the moon than has been previously obtained.