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Compact Lunar Hydration and Mineralogy Explorer (CLuHME)

Presentation #001.10 in the session “Future Missions, Instruments, and Facilities”.

Published onOct 26, 2020
Compact Lunar Hydration and Mineralogy Explorer (CLuHME)

Compact Lunar Hydration and Mineralogy Explorer (CLuHME) is a MWIR/LWIR (2.5-12.5µm) hyperspectral imaging instrument to identify and characterize lunar materials and ice(s) on surface and walls with sub-cm spatial resolution spectroscopic data cubes from 1 meter to horizon from a lunar lander, rover, or as a handheld by an astronaut in the field (Fig. 1). Mapping distribution of water, hydroxyl (radical or groups), minerals, thermal properties, and regolith fine structure are relevant to understanding the lunar water cycle and for in situ resource utilization. Primary lunar mineralogic composition includes pyroxene, olivine, anorthite, ilmenite,and spinel, all of which contain a significant fraction of oxides by mass. Lunar highland material (theorized as original crust) is dominated by plagioclase feldspar and poor in pyroxene and olivine. In comparison, basaltic lava flow mare are a mix of plagioclase, orthopyroxene, clinopyroxene, olivine, and ilmenite. CLuHME on a polar lander can reveal the “geology of the South-Pole Aitkenbasin.” A recent study estimated ~100 billion metric tons of near surface water ice may be distributed in lunar cold traps. CLuHME optical sensing technology is based on the 3 µm (~3200–3700 cm-1, stretching-modes) vibrational bands associated with both water (nu1/nu3) and OH (nu1). Analysis of lunar equatorial soils concluded solar-wind produced OH was a viable source for water ice in polar cold-traps with slower degassing rates. Discrimination of water-bearing from OH-bearing minerals is critical to plan resource recovery operations and constrain models of exogenic and endogenic sources. As indicated by a reflectance trough, the 6 µm (1595 cm-1, nu2 bending-mode vibrational band) of monomer ice (e.g., Ih state) results in an emissivity peak unique to water (from OH), seen in dirty ice, but absent from OH-hydrates. Another relevant signature is the 12 µm (780 cm-1 libration) band of water. For thermal observations, control of the viewing (emission) angle is relevant given the angular dependence of emissivity. CLuHME also applies to missions to (1) planets, asteroids, moons, and comets in support of surface hydration and mineralogy characterizations, and (2) coma volatile fluorescence in comets.

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