Background
We are developing a high-sensitivity portable Raman instrument capable of detecting complex molecular species and minerals that are fundamental to investigating minerals and volatiles essential for in situ resource utilization (ISRU) and organic molecules whose detection is essential for the search for life elsewhere. Field-portable Raman spectrometers are becoming an important tool in field-based studies to understand habitability of extreme environments on Earth, which are analogs of planetary environments. Additionally, portable Raman instruments are expected to be included on future human exploration missions as an Astronaut tool. This portable instrument is specifically designed to implement field-based ISRU and astrobiology analog studies. Our portable instrument includes a monolithic integrating cavity developed as part of this work would can also coupled to existing lasers and research-grade spectrometers in Div. 15 and Div. 18 to enable non-destructive high-sensitivity analyses to determine the mineralogy and organic matter composition of returned samples from other planetary bodies, including the asteroid Bennu recently sampled by the OIRIS-Rex mission.
Approach
We leverage the integrating Cavity Enhanced Raman Spectroscopy (iCERS) breadboard design from Co-I Retherford’s PDIR 15-R8834 to build a research-grade analytical iCERS instrument, which can be used for sample return analyses for several years with a companion field-portable version for terrestrial analog sample analysis (Figure 1). This instrument, named Astronaut Raman for ISRU and Astrobiology (ARIA), provides field-based VIS (638 nm) Raman capabilities to establish scientific leadership in planetary-focused Raman spectroscopy by completing the following capability development focused tasks:
Accomplishments
We established an Optics Laboratory in Div 18’s B82, which houses laboratory space, Raman spectrometers, multiple lasers, optical components, and the clean tent for cavity production along with associated equipment and developed sample handling techniques for returned samples which must be preserved given their rarity. We designed and fabrication of our portable prototype instrument, named Astronaut Raman for ISRU and Astrobiology (ARIA), which includes four key subsystems: (1) 150 mW 638 nm laser excitation source, (2) 638 nm QEPro Raman spectrometer, (3) a newly designed monolithic integrating cavity to enhance the Raman signal, and (4) an electronics box that is powered by a 12 V rechargeable battery power supply and/or solar panels. We performed initial LOD testing of the instrument as part of our cavity optimization plan.
The monolithic integrating cavity designed for this project, consists of two sealed pieces, a top integrating cavity and a sample tray base. Each piece consists of a stainless-steel outer hull, an internal fused silica glass liner, sealant to fuse the outer hull and inner liner, and fumed silica packed in between to produce the Lambertian reflector. This design adds complexity not present in other cavity designs, because of the internal glass liner and required sealant. Additional research is required to fully optimize this new cavity design. We did train two additional staff members on integrating cavity production. We have a pending utility patent application for this new integrating cavity design and created a working method for cavity production that can be used by other SwRI researchers.
During the period of performance, we submitted 2 NASA PSTAR proposals ($400K for ARIA improvements in each proposal), and won a NASA Habitable Worlds project that will use the cavity to analyze organics in Europa and Enceladus analog ices. We also presented at Astrobiology Science Conference (AbSciCon), which yielded opportunities for additional collaborations including a SSERVI proposal, additional PSTAR proposals, and potentially a PICASSO proposal for ARIA’s future development as an astronaut tool.