Optical Design of Compact high resolution Raman Spectrometer for Interplanetary Mission

This paper discusses the challenges associated with designing a space-qualified Raman Spectrometer for lunar exploration, emphasizing the need for high sensitivity, compactness, lightweight, and robustness to withstand the harsh lunar environment. The Indian Space Research Organisation (ISRO) is developing a Raman instrument for future lunar missions aimed at identifying mineral constituents in lunar soil with resolution of 8 cm(-1) within the wavenumber range of 150 cm(-1) to 3800 cm(-1). The instrument's design features a monostatic configuration, employing a common optics system for laser focusing, sample positioning, and signal reception to mitigate misalignment errors. Key optimization considerations include mass, volume, and sensitivity, given the stringent constraints of space missions. The instrument utilizes a Volume Phase Holographic (VPH) transmission grating with a groove density of 1500 lines per millimeter (lp/ mm) to meet performance requirements. This paper provides valuable insights into the challenges and design considerations inherent in developing Raman spectroscopy instruments for lunar exploration.