Lunar x-ray spectrometer experiment on the SELENE mission

Major elemental mapping of lunar surface has been planned using the XRS instrument on the SELENE orbiter. Arrayed charge-coupled devices (CCD) are used due to its high energy resolution. By thermal design of the XRS with radiation cooling, CCD is kept cool enough to reduce excitation of thermal electrons and improve signal-to-noise ratio: During lunar x-ray fluorescence spectrometry, concurrent monitoring of solar x-rays as well as in situ calibration of x-ray fluorescence using a standard sample is performed for quantitative elemental analysis. Observed data are processed with on-board electronics that effectively extracts x-ray events. In one-year mission, the XRS will cover all the lunar surfaces except for polar region and map elemental composition with spatial resolution of 20km. We present instrumentation of the XRS and its current status of development, as well as showing the XRS observation plan of lunar elemental mapping. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.