Next generation compact IR spectrometers for the Moon

Abstract

Our understanding of the origin, movement, and storage of water on the Moon remains largely unconstrained. Measurements of water absorption features over the same swaths as a function of time of day from a nearly polar orbit, the science goal proposed for the BIRCHES (Broadband InfraRed Compact High-resolution Exploration Spectrometer) payload designed and built for the Lunar Ice Cube orbiter, was intended to provide such essential constraints. BIRCHES was a compact version of OVIRS (Origins Spectral Interpretation Resource Identification Security Regolith Explorer Visible InfraRed Spectrometer) plus a compact cryocooler. IR spectrometer capabilities have been greatly advanced, since its selection in 2015 for the NASA NEXT STEP program, in terms of sensitivity, spectral coverage, and less active cooling demand as exemplified by the NASA GSFC Compact Thermal Imager (CTI), which utilizes a Type II SLS (Strained Super Lattice) combined with the ACADIA processor, follow on to the OVIRS SIDECAR (System Image, Digitizing, Enhancing, Controlling, And Retrieving) ASIC. Although initially developed for astronomical applications, the CTI has, with the addition of a cryocooler, already been modified for lunar surface applications. The 'Next generation' orbital mission and surface package concepts discussed here would utilize advanced versions of BIRCHES, of comparable mass, power and volume but with superior performance, and would likely be significantly more robust and 'roomy', due to availability of high-performance thermal protection components and a larger 12U platform. A compact textual camera and internal calibration source would thus be added.