Spatial Heterodyne Raman Spectrometer for Lunar Mineral Detection with Fixed Geometry and Sampling Analysis Design

Raman spectroscopy is essential for the in situ identification of lunar minerals, yet weak signals and stringent payload constraints demand instruments with high throughput and mechanical robustness. Here a microscope-coupled spatial heterodyne Raman spectrometer (SHRS) is developed for stable, adjustment-free operation, with performance set by an explicit sampling analysis that links magnification, pixel pitch, and detector format to achievable spectral resolution and range. The interferometer geometry is fixed in service and is established using removable alignment blocks referenced to the Littrow condition during integration and then removed from the optical path, which mitigates backlash, creep, and dust sensitivity while preserving reinstallability for verification. Guided by the sampling analysis, the laboratory prototype meets a 100–3600 cm−1 spectral range with an effective resolution better than 10 cm−1, further corroborated by the narrow FWHM of the diamond Raman line. Representative minerals are recovered at the expected wavenumber, and a broad-scan of gypsum retrieves the sulfate fundamentals and the O–H stretching envelope near 3400 cm−1, indicating maintained coverage and sensitivity into the high-wavenumber region relevant to bound water. A comparative study of sampling magnification confirms the sampling-limited predictions and shows that higher magnification improves effective SNR and peak visibility with only minor changes in width, providing practical guidance for compact SHRS design under low-signal conditions. The results support a compact, slit-free SHRS as a credible basis for future lunar and other planetary deployments.