LunaR: Overview of a versatile Raman spectrometer for lunar exploration

Abstract

The LunaR concept study investigated the scientific value, feasibility, and deployment options for a Raman spectrometer on future lunar landed missions. It consists of a breadboard instrument that covers the 150–4000 cm−1 wavelength range with a resolution of ∼6 cm−1; Raman scattering is induced by a 532 nm continuous wave laser. The current conceptual design envisions the Raman spectrometer performing a downward-looking, 90-point one-dimensional across-track scan (±45°off nadir) of the lunar surface with the instrument mounted on the underside of a rover. A downward-looking context camera would provide information on the physical nature of targets interrogated by the Raman spectrometer and localization of the Raman spectra. Our laboratory investigations indicate that Raman spectroscopy is applicable to addressing a wide range of lunar surface exploration goals related to geology, in situ resource identification, and condensed volatile detection in diverse geological terrains, including permanently shadowed regions. Testing of a breadboard and commercial instrument on lunar samples and analogues indicates that a complete spectral scan of a target of interest can be completed in ∼90 min, permitting its use on even short-duration lunar landed missions. All of the major minerals present on the Moon can be detected, and in many cases their compositions can be quantified or constrained.

A Raman spectroscopy–compositional–structural investigation of lunar surface materials and analogues

“…This study is a companion to related work that is designed to investigate the feasibility of a Raman spectrometer for lunar surface exploration. 41 The results of this study demonstrate that Raman spectroscopy is a powerful tool for lunar surface investigations. At a minimum, it is able to detect the presence of the major lunar rock-forming minerals and place constraints on their compositions.…”

“…This study is a companion to related work that is designed to investigate the feasibility of a Raman spectrometer for lunar surface exploration 41 . The results of this study demonstrate that Raman spectroscopy is a powerful tool for lunar surface investigations.…”

Speckle Noise Reduction via Linewidth Broadening for Planetary Laser Reflectance Spectrometers

“…For lunar applications, the primary laser-based spectroscopy techniques of interest are Raman spectroscopy (in a standoff geometry) and laser reflectance spectroscopy, which would target mineralogical features and identification and qualification of volatile species such as H 2 O/OH [16][17][18][19][20]. Here, we will focus on laser reflectance spectroscopy, which uses precisely selected laser sources to interrogate spectral features, primarily in the nearand mid-infrared portions of the spectrum.…”

“…Reflectance data from the Lunar Orbiter Laser Altimeter (LOLA) on the Lunar Reconnaissance Orbiter (LRO) were used to identify Remote Sens. 2024, 16, 1515 2 of 13 anomalously high reflectance regions at 1064 nm coincident with regions of permanent shadow that may indicate water ice exposures [6,[21][22][23], but the spatial resolution and precision of the LOLA reflectance measurements were limited partly due to the laser wavelength, which was primarily designed for altimetry measurements. Higher-precision and higher-resolution laser reflectance measurements at carefully selected laser wavelengths in the mid-infrared could quantify H 2 O/OH abundance at the tens of ppm level [24] but will require high signal-to-noise ratios (SNR) of both the transmitted and received laser energy measurements.…”