SELENE, the Japanese Lunar Orbiting Satellites Mission: Present Status and Science Goals

Introduction: Lunar remote-sensing mission SELENE has started as a joint mission of ISAS and NASDA of Japan in 1998 FY. Japanese space agency and institutes of ISAS, NASDA and NAL have been merged into a space agency JAXA in October 2003. SELENE project is certainly identified as a JAXA’s science mission. Launch target is rescheduled for 2007 summer due to delay of completion of launch vehicles, H2 and H2A. Now science instruments are being carried out functional checks and calibration before integration. In April 2006 over-all integration and environment tests of interface, vibration, thermalvacuum, and end-to-end GDST will be set about in TKSC of JAXA and in SOAC (SELENE Operation and data Analysis Center) of Sagamihara/JAXA. After completing several tests for a year, the SELENE spacecraft will be shipped to Tanagashima launch site. Science Goals and Instruments: Key questions on lunar science are “What’s origin of the Moon ?”, “How does the Moon have evolved ? ”, and “What history does the lunar environment have passed ? “. Science topics to be studied by using SELENE data are surface composition of chemistry and mineralogy, evolution tectonics of surface including subsurface to 5 km depth, gravity field of whole moon and magnetic field distribution for the study on origin and evolution of the Moon. Lunar environment are investigated in observing charged and neutral particles impinged on the surface. 14 science instruments onboard the SELENE satellite to remote-sense the lunar surface and environment for above lunar science have been selected by an evaluation board of the Steering Committee of Space Science. Final specifications of the instruments are summarized in Table 1 after some revises and improvement through the implementation. Largest change of configuration are taken on in the differential VLBI experiment. VRAD sub-satellite, Vstar carrying VLBI radio source is adapted due to cancellation of landing experiment in which radio source planed to be installed in the lander. Figure 1 shows a schematic drawing of SELENE satellite in the lunar-transfer orbit before separation of sub-satellites, after deployments of high-gain antenna and solar cell paddle. High Definition TV cameras install on the Z-panel of lower module for broadcasting mission of space born movies, i.e..” Rising Earth on the lunar horizon”. The total mass of science instruments is kept within nominal mass of 297 kg, so mass budget has propulsion margin of 113 kg, which will employ for an optional observation after nominal duration of about an year.