The Raman Laser Spectrometer: A performance study using ExoMars representative crushed samples

Abstract

The Raman Laser Spectrometer (RLS) is one of three key analytical instruments incorporated within the body of the ExoMars 2022 rover. The rover will collect samples from different sites on the Oxia Planum plain, using a drill capable of penetrating the near subsurface and rocky outcrops to a depth of 2 m. Samples are passed to the Analytical Laboratory Drawer (ALD) in the heart of the rover vehicle, where the Sample Preparation and Distribution System (SPDS) processes and transports the crushed material into a refillable container (RC), which is then presented to the analytical instruments for exobiology and geological investigation. The final sample grain distribution of the powder sample following the crushing and flattening processes is a critical aspect of the RLS instrument that has a direct impact on its overall performance, related to its mineral identification and operational capabilities. This paper provides a comparative overview of the performance of a set of Raman instruments, the RLS micro-Raman Laboratory Equipment, the RLS ExoMars Simulator, and the RLS Engineering and Qualification Model (EQM) using Martian representative crushed samples, along with an evaluation of instrument performance as a function of the operational scenario. The results from the work performed by the RLS team confirm the capability of the RLS instrument performances, by acquiring good-quality spectra from crushed samples provided by the SPDS, whose science return can be further optimized when improving the RLS instrument operation sequence.