Compact, Robust Spatial Heterodyne Raman Spectrometer for Planetary Exploration

Objectives: The goal of this project is to advance and mature a new type of miniature interferometer based Raman spectrometer, the spatial heterodyne Raman spectrometer (SHRS) that we developed with previous PICASSO funding. The SHRS will be brought to TRL 3 by building a proof of concept model using monolithic optical construction techniques to provide miniaturization, robustness and high spectral performance. Raman spectroscopy is potentially a powerful tool for planetary exploration and three instruments are planned for upcoming Mars missions. But conventional Raman systems are large, heavy and fragile and expensive to engineer for planetary applications. The proposed monolithic SHRS (mSHRS) is smaller, lighter, and more robust than conventional Raman spectrometers, and has better sensitivity, larger spectral range, and a much larger field of view making it more sensitive and easier to engineer, expanding planetary applications. In the proposed project we will build on the SHRS that we previously brought to between TRL 2 and TRL 3.Some of the proposed changes lower the overall TRL to 2, but we will advance this technology to TRL3 at the end of this work. We will advance the technology by moving to a monolithic integrated optic design (mSHRS) where all optical components of the SHRS are directly bonded to each other in a very small solid-state package with no moving parts. Monolithic construction makes the system very robust to vibrations and shock and allows a much smaller spectrometer to be constructed because there are no supporting elements. The unprecedentedly small size and high sensitivity of the mSHRS will allow its use in smaller spacecraft, like CubeSats, and will allow multiple spectrometers to be flown in a single small spacecraft, greatly expanding the amount of information that can be gathered and increasing analysis throughput. The proposed mSHRS Raman spectrometer will be small enough to fit in a 1U Planetary CubeSat for standoff Raman, or in a 25-mm diameter borehole for in-situ mineralogy and high resolution spatial mapping. Expected Significance: Raman spectra provide a unique "fingerprint" to identify minerals and organic compounds in complex mixtures. The proposed monolithic Raman spectrometer is not simply a smaller version of existing instruments but a radically new design that allows truly miniature spectrometers with spectral characteristics equal to or better than larger instruments, light throughput for extended sources up to hundreds of times higher than conventional Raman instruments of comparable size, and with features not found in any dispersive Raman spectrometer such as a wide-area measurement and spatial imaging capability. NASA Relevance: The proposed miniature Raman spectrometer will be small enough for analysis in boreholes of the type that will be used on Mars, Europa and Enceladus to look below the surface and will also be small enough for use in a 1U CubeSat. The monolithic SHRS design is applicable to a broad range of planetary missions and will directly address science questions raised in the 2013 Decadal Survey for Planetary Sciences. This proposal is directly relevant to NASA's Strategic Plan 2018, Goal "Address National Challenges and Catalyze Economic Growth"; Objective 3: "Develop and Transfer Revolutionary Technologies to Enable Exploration Capabilities for NASA and the Nation". The proposed monolithic SHRS is also relevant to the PICASSO Program, "to develop new proof-of-concept instruments or instrument components, including sampling technologies that enable new science by significantly improving instrument measurement capabilities for planetary science missions." Key science objectives include bringing the time-resolved monolithic SHRS to TRL 3, and determining limitations in terms of size and weight and limits of detection for key minerals and organic compounds, and identifying design issues related to miniaturization. More »