Introduction to the lunar gamma-ray spectrometer for Korea Pathfinder Lunar Orbiter

Presently, KPLO (The Korea Pathfinder Lunar Orbiter)'s Gamma-Ray Spectrometer (KGRS) is being developed for an engineering model. The scheduled final KGRS development will be completed no later than mid-2019. The KPLO weighs approximately 550 kg and it will be launched in late 2020 by Falcon 9 rocket. The KPLO Gamma-Ray Spectrometer system is a compact low-weight instrument for the chemical analysis of lunar surface materials within a gamma-ray energy range from 10s keV to 10 MeV. The KGRS will collect low energy gamma-ray signals by either X-ray fluorescence or by natural radioactive decay in the low energy regions of spectrum and higher-energy gamma rays due to either neutron capture or inelastic scatter. The GRS system will determine the elemental compositions of the near surface of the Moon for investigation of the lunar geology and resources. The main LaBr _{3} detector of KGRS is surrounded by an anti-coincidence counting module of a boron-loaded plastic scintillator to reduce both low energy gamma-ray background from the spacecraft and housing materials and high energy gamma-ray background from cosmic rays. The main detector has high and low gain settings for gamma-ray energy ranges up to 3 and 10 MeV, respectively. One month of calibration and 11 months of a nominal mission period are planned with a minimum required GRS background measurement at anti-nadir direction. The planned altitude of KPLO in orbit is 100 ± 40 km, and KGRS data will be collected every 10 sec. The KGRS investigation will help to assess open questions related to the spatial distribution and origin of the elements on the lunar surface and will contribute to unraveling geological surface evolution and elemental distributions of potential lunar resources. This talk introduces the current development of KGRS and prospective scientific outcomes by KGRS data.