Lunar Mineralogical Spectrometer on Chang’E-5 Mission

Abstract

AbstractThe Lunar Mineralogical Spectrometer (LMS) is one of the main payloads on the Chang’E-5 (CE-5) lunar probe, belonging to the China Lunar Exploration Program. The scientific objective of the LMS is to explore the mineralogical composition and search for evidence of -OH/H2O in the sampling area. The LMS consists of an optomechanism unit, a dustproof calibration unit (DPCU) and an electronic unit. The LMS is installed on the lander about 1.4-m above the lunar surface, the field of view (FOV) is $4.17\times 4.17^{\circ }$ 4.17 × 4.17 ∘ , the instant FOV of the visible imaging channel is 0.28 mrad, and the typical spatial resolution is 0.56 mm/pixel @ 2 m distance. The rotation range of the 2D scanner is $\pm 22.5^{\circ}$ ± 22.5 ∘ along the azimuth axis and $0\sim 30^{\circ }$ 0 ∼ 30 ∘ along the elevation axis, making it possible to observe the sampling area or to select important observing targets. The dispersing beam uses acousto-optic tunable filters, and target detection is performed with a 2D scanner. The LMS acquires spectral imaging information covering 480–950 nm, and reflectance spectra of 900–3,200-nm, both at a 5-nm/band sampling interval. The spectral resolution is $2.4\sim 9.4\text{ nm}$ 2.4 ∼ 9.4  nm in the visible and near-infrared channels and $7.6\sim 24.9\text{ nm}$ 7.6 ∼ 24.9  nm in the short–medium-wave infrared channel. The LMS has a 588-band detection capability designed for fine spectral observation of sampling points and wields a 20-band full-view multi-spectral mode to observe candidate areas prior to sampling. The DPCU of the LMS is integrated with a calibration diffuser that is used for in-flight calibration on the lunar surface using solar irradiation, thus improving the quantitative level of scientific data.