Abstract
Abstract The x-ray fluorescence spectrometer (XRS) on board Japanese lunar polar orbiter SELENE (Kaguya) will provide global distribution of major elemental composition on the lunar surface in energy range of characteristic K-α x-ray line emission for Mg, Al, Si, Ca, Ti, and Fe. These measurements will contribute to research of lunar origin and its evolution. The XRS shows a good energy resolution within 200 eV at 5.9 keV relying on charge coupled device (CCD) as photon energy dispersive detector. Total collective area of 100 cm2 for main detector facing the lunar surface is composed of 16 CCD chips. Instrumentation of the XRS and its performance evaluated in laboratory are presented.
Highlights
The x-ray fluorescence spectrometer (XRS) is one of 14 scientific instruments on-board SELENE (SELenological and ENgineering Explorer) mission (Sasaki et al, 2003; Kato et al, 2007), launched to the Moon in the summer of 2007 by H-IIA
Usage of 16 charge coupled device (CCD) chips with the adoption of ultra-thin beryllium optical light-tight window has allowed large effective area to collect the x-ray emitting from the lunar surface in fairly high energy resolution
With the energy resolution presented in this study, we performed a numerical series of calculation for lunar x-ray fluorescence emission and discussed the necessary integration time for achieving both sufficiently high signal to background ratio and the along-the-track spatial resolution under assumed solar x-ray conditions
Summary
The x-ray fluorescence spectrometer (XRS) is one of 14 scientific instruments on-board SELENE (SELenological and ENgineering Explorer) mission (Sasaki et al, 2003; Kato et al, 2007), launched to the Moon in the summer of 2007 by H-IIA. More recently the European Space Agency’s SMART-1 mission carried the Demonstration of a Compact Imaging X-ray Spectrometer (D-CIXS), which performed x-ray spectroscopic remote observation of lunar surface (Grande et al, 2007). As the strength of the remote XRF technique in ability of quantitative and qualitative measurement for elemental abundances such as Mg, Al, and Si, future planned lunar explorer missions such as Chinese Chang’e-1 (Sun et al, 2005) and Indian Chandrajaan-1 (Bhandari, 2005) will carry XRF spectrometers as one of its core scientific payloads. The XRS on-board SELENE aims its primary goal in global mapping of major elemental abundance of the lunar surface through remote XRF spectroscopic technique. The solar output of higher energies are relatively low, insignificant to measure the higher energies of heavier fluorescent lines. The detection system, an array of CCD chips, has relatively high energy resolution achievable with passive cooling
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