Raman Deep Ultraviolet - Visible Spectrograph Concepts for Lunar and Ocean World Missions

Raman spectroscopy is well suited for numerous volatile, mineralogical, and astrobiological studies, making Raman destined to become a core payload instrument on future lunar and Ocean World missions. As previously demonstrated for the Moon, the relative ratios of C-H-O-N-S volatile species are diagnostic of the key source and loss processes for lunar volatiles (Mandt et al. 2022) and all are constrainable with Raman measurements. Assessments of mineral trace species, hydration states, and space weathering (npFe0/SMFe) related alterations of olivine and plagioclase feldspar are all possible with Raman spectral features, providing relative chronological constraints for investigating surface composition and evolution. In particular, the ability to fingerprint complex molecules of interest to astrobiology (e.g., pigments, amino acids, bacteria types, etc.) makes Raman instrument concepts well suited to Ocean World mission investigations. After several years of internal research and development (IR&D) funding from SwRI, a newly awarded DALI program is further advancing the development of a Lunar Raman Deep-Ultraviolet Visible Spectrograph (LR-DUV-VIS; e.g., “du-viz”) concept from TRL 4 to 6. This concept focuses on a dual-laser Deep-UV+Visible Raman system capable of detecting complex molecules and performing compositional assays with a fiber-fed focusing lens sensor. An ongoing IR&D project focuses on the sample handling techniques required for an enhanced Raman method that uses a TRL 6 deep-UV optimized integrating cavity, generally named integrating Cavity Enhanced Raman Spectroscopy (iCERS). Both approaches allow avoiding the effects of autofluorescence background signals and degeneracy of emission line features for different species by using both 266 nm and 633 nm space-rated laser sources developed by Fibertek in partnership with TOPTICA Photonics. We’ll describe the instrument concepts enabled by theses parallel development efforts, including the status of laser, spectrograph, sensor (both focusing lens and integrating cavity), electronics, and sample handling subsystems. The fiber-fed approach enables easy adaptation of the developed sub-systems for custom science investigations with various landed, rover, lunar terrain vehicle, astronaut-assisted, and flyby opportunities.