2018.P.1.12. Water ice and ilmenite mapping of the Moon using a multiwavelength lidar on a 12U CubeSat

Author(s)

Edward Cloutis (1)
Brynn Dagdick (1)
Alexis Parkinson (1)
Roman Kruzelecky (2)
Piotr Murzionak (2)
Yang Gao (3)
Craig Underwood (3)

University of Winnipeg, Canada
MPB Communications Inc., Canada
University of Surrey, United Kingdom

Session

P.1

Keywords

Moon; cubesat; ilmenite; water ice; lidar; reflectance spectroscopy

Abstract

Introduction: Detecting and mapping water ice in lunar permanently-shadowed regions (PSRs) is scientifically important and for enabling extended human presence on the Moon. Through an ESA SysNova concept study, we have defined some preliminary operational characteristics for a 12U lunar CubeSat. The proposed orbit would enable mapping of a 300 km diameter region centered on the lunar South Pole in ~13 days from a 20 km nadir orbit. The main science instruments are a dual-frequency co-aligned lidar: 532 and 1560 nm, which would acquire data with a spatial resolution of ~4 x 44 m per point, and an ~1.3 km swath width. The lidar detectors could also acquire passive reflectance spectra, enabling mapping of unshadowed regions. Tentative identified wavelengths for this are: 280 and 1064 nm. The latter may also be operational in active mode, giving 4 passive and 3 active wavelengths.

Laboratory studies of lunar analogues: To assess how well the proposed lidar system would be able to detect water ice, we conducted reflectance measurements on mare (JSC-1) and highland (CHENOBI) lunar regolith simulants. Reflectance spectra were measured in lidar mode (i=e=0°) for a range of sample types, including coarse and fine powders, loose and packed powders, various abundances of water ice, and varying tilt angles.
Results: Pure water ice reflectance at 532 nm increases with decreasing particle size. Both simulants have similar 532/1560 nm ratios that vary slightly with changes in porosity and grain size. The addition of mixed-in water ice results in increases in this reflectance ratio, but no systematic change in reflectance at 532 nm. This is because the 1560 nm bandpass is located in a moderately strong water ice absorption band, while 532 nm reflectance is largely insensitive to water ice presence.

These results indicate that the use of both 532 nm reflectance and 532/1560 nm reflectance ratio allows for discrimination of dry versus water ice-bearing regolith, and highland from mare. It also allows constraints to be placed on the physical state of any surficial ice.

Future directions: We will be conducting additional spectroscopic studies that will examine the effects of water ice grain size, surficial water ice/frost versus mixed-in water ice, regolith over bedrock, topography, and additional simulants. The goal is to understand how this two-lidar system can quantify physical and compositional properties of PSRs, and mapping of ilmenite-rich terrains.

Acknowledgements: This study was supported by ESA, CSA, NSERC, CFI, MRIF, and UWinnipeg.