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The high precision gamma-ray spectrometer (GRS) is carried on the first Japan's large-scaled lunar explorer, SELENE (KAGUYA) circling a polar orbit. The GRS consists of a large Ge crystal as a main detector and massive bismuth germanate crystals and a plastic scintillator as anticoincidence detectors. Since the successful launch on Sep. 14, 2007, radiation damage in the Ge detector has been induced from the incidence of energetic particles from space, which degraded its energy resolution. Then the Ge detector was annealed for 2 days at 85±5 K and the resolution is recovered to the level at the initial phase of the early observation. The special operations were conducted in December, 2008 in order to measure backgrounds gamma rays from the materials of the spacecraft body and the GRS instrument itself. The GRS data from the 100 km altitude reveal the global distribution of trace elements of Th and K on the Moon which delineates the distributions of KREEP component of lunar materials. Th and K-rich materials are concentrated around the Imbrium basin in Procellarum KREEP Terrane (PKT) and intermediately concentrated in South Pole–Aitken basin area on the farside. Results from special operations and observation are described and discussed.

Research Institute for Science and Engineering., Waseda Univ., Japan College of Health Science, Saitama Prefectural University,, Japan Inst. of Space and Astronautical Science, JAXA, Japan Nippon Medical School, Japan Dep. of Chemistry, Tokyo Metropolitan Univ., Japan National Institute of Polar Research, Japan Japan Agency for Marine-Earth Science and Technology, Japan Research Institute, Chiba Institute of Technology, Japan Centre d’Etude Spatiale des Rayonnements,Toulouse, France Dep. of Meteorites, Univ. of New Mexico, USA *nhasebe@waseda.jp