MoonIS Spectrometer on RASHID rover 3: investigating the lunar permanently shadowed regions

 MoonIS (Moon Infrared Spectrometer) is a VIS–NIR spectrometer (0.4–2.3 μm) om  board of  the Emirates Lunar Mission (ELM) of the Mohammed Bin Rashid Space Centre (MBRSC) [1]. Rashid Rover 3 aims to investigate the geology and mineralogy of the southern polar terrain, explore Permanently Shadowed Regions (PSRs), and characterize the presence and distribution of water ice and hydroxyl on and beneath the lunar surface. The mission will investigate the lunar South Pole region, with launch currently planned not earlier of 2029. MoonIS spectrometer is a heritage of the Ma_MISS instrument on board the Rosalind Franklin rover of the ESA ExoMars mission [2].

Lunar PSRs are considered among the most promising reservoirs of water ice in the inner Solar System and constitute prime targets for sustainable lunar exploration. These permanently shadowed regions act as cold traps for volatiles delivered through cometary and asteroidal impacts, surface–solar wind interactions, and possibly endogenic outgassing processes [3–7]. Although hydrogen-bearing species have been detected, the fine-scale geomorphology, physical state, and spatial distribution of ice within PSRs remain poorly constrained because of the limited spatial resolution and signal-to-noise ratio of current datasets [8–11]. Moreover, the extent to which lunar water ice is exposed at the surface is still uncertain, as its morphology does not exhibit the expected diagnostic characteristics [12–14].

In situ investigations are therefore essential to constrain the abundance, distribution, and origin of lunar polar volatiles, as well as to clarify their implications for the history of water in the Solar System. For this reason, several space agencies are planning rover missions aimed at investigating water ice and the overall surface composition within PSRs, while also paving the way for future human exploration of the Moon.

 

MoonIS is derived from the Ma_MISS spectrometr on board of  ESA’s ExoMars Rosalind Franklin rover, with significant adaptations to its optical head, calibration system, thermomechanical design, and electronics in order to operate under the harsh environmental conditions of the lunar surface. The instrument architecture consists of an optical head mounted on the rover mast and connected, through optical fibers, to a spectrometer unit located inside the rover body. Each fiber is coupled to a dedicated optical element and mapped onto the spectrometer slit, enabling the simultaneous acquisition of multiple spatial elements (“pseudo-pixels”) and the generation of hyperspectral images. The MoonIS optical head is composed of three optical elements specifically designed to maximize spatial coverage and spectral performance. By combining mast scanning and rover motion, the instrument will investigate the terrain surrounding the rover in both illuminated regions and Permanently Shadowed Regions (PSRs). To enable spectral observations within these extremely dark environments, MoonIS incorporates an onboard illumination system capable of acquiring measurements independently of solar illumination. In addition, the implementation of an external calibration target is being considered to ensure accurate radiometric and spectral calibration throughout the mission.

 

The primary scientific objectives of MoonIS are to:

• Detect and discriminate between H₂O- and OH-bearing materials;
• Quantify the abundance and spatial distribution of hydrated phases and water ice;
• Map the mineralogical composition of the landing site;
• Identify the major lunar lithological units;
• Detect and quantify key minerals, including pyroxenes, olivines, feldspars, and spinels;
• Characterize mineral assemblages and their spatial variability.

 

The instrument spectral range (0.4-2.3 micron), spectral resolution, signal-to-noise ratio, and spatial sampling have been specifically optimized to achieve these objectives under both illuminated and permanently shadowed conditions. By providing high-quality in situ hyperspectral measurements, MoonIS will deliver critical ground-truth data for the characterization of lunar polar volatiles, significantly improving our understanding of the origin, evolution, and preservation of water on the Moon, while also supporting future robotic and human exploration activities.

Acknowledgments:
This work is supported by ASI–INAF Agreement n. 2024-64-HH.0. The instrument is funded by ASI and manufactured by Leonardo S.p.A. (Italy).

 

References: [1] De Sanctis, et al. (2025) (EPSC-DPS2025-587). [2] De Sanctis et al. (2017): Astrobiology 17, 6, 7. [3]  McCubbin et al. (2015) American Mineralogist 100: 1668-1707. [4] Honniball et al. (2021) Nature Astronomy 5: 121-127. [5] Pieters et al. (2009) Science, 326, 568–572. [6] Arnold, J. R. (1979) J.G.R. 84, 5659–5668. [7] Wang, J. et al. (2025) P.N.A.S. U.S.A. 122, e2501614122. [8] Hayne, P. O. et al. (2015) Icarus 255, 58–69. [9] Feldman, W. C. et al. Science 281, 1496–1500 (1998). [10] Lucey, P. G. et al. (2014) J.G.R. Planets 119, 1665–1679. [11] Massa et al. (2026) ELS 2026. [12] Ando, J., et al. (2025) P.S.J. 6, 62 (2025). [13] Williams, J.-P. et al. P.S.J. 5, 209 (2024). [14] Mahanti, P. et al. J.A.S.S. 40, 131–148 (2023).