Homogeneity assessment of the supermcan calibration targets

J. M. Madariaga, J. Aramendia, G. Arana, L. Gómez-Nubla, S. Fernandez-Ortiz de Vallejuelo, K. Castro, C. Garcia-Florentino, M. Maguregui, I. Torre-Fdez, J. A. Manrique, G. Lopez-Reyes, J. Moros, A. Cousin, S. Maurice, A.M. Ollila, R. C. Wiens, F. Rull, J. Laserna, V. Garcia-Baonza, M. Madsen, O. Forni, J. Lasue, S.M. Clegg, S. Robinson, P. Bernardi, P. Caïs, J. Martinez-Frias, P. Beck, S. Bernard, M.H. Bernt, E. Cloutis, O. Beyssac, C. Drouet, B. Dubois, G. Dromart, C. Fabre, O. Gasnault, I. Gontijo, J.R. Johnson, J. Medina, P.-Y. Meslin, G. Montagnac, V. Sautter, S.K. Sharma, M. Veneranda, P.A. Willis, Spectrochimica Acta Part B, in press


The SuperCam instrument, onboard of Perseverance rover, Mars 2020 mission, is designed to perform remote analysis on the Mars surface employing several spectroscopic techniques such as Laser Induced Breakdown Spectroscopy (LIBS), Raman, andTime-Resolved Fluorescence (TRR/TRF) and Visible and InfraRed (VISIR) reflectance. In addition, SuperCam also acquires high resolution images using a color remote micro-imager (RMI) as well as sounds with its microphone. SuperCam has three main subsystems, the Mast Unit (MU) where the laser for chemical analysis and collection optics are set, the Body Unit (BU) where the different spectrometers are located inside the rover, and the calibration target (SCCT) exposed outdoor to perform calibration tests at similar ambient conditions than analyzing the samples. To perform adequate calibrations when in Mars, the 22 mineral samples included in the complex SCCT device must have a high homogeneity distribution of major and minor elements. The analysis and verification of such homogeneity for the 5/6 replicates of the samples included in the SCCT has been the aim of this work. To verify the physico-chemical homogeneity of the calibration targets micro Energy Dispersive X-ray Fluorescence imaging was first used on the whole surface of the targets, then the relative abundances of the detected elements were computed on 20 randomly distributed areas of 100×100 microns. For those targets showing a positive Raman response, micro-Raman spectroscopy imaging was performed on the whole surface of the targets at a resolution of 100×100 microns. The %RSD values for the major elements measured with EDXRF were compared with similar values obtained by two independent LIBS set-ups at spot sizes of 300 microns in diameter. The statistical analysis shown which elements were homogeneously distributed in the 22 mineral targets of the SCCT, proposing their uncertainty values for further calibration works. Moreover, nine of the 22 targets shown a goof Raman response and their mineral distribution was also computed. Those targets can be also used for calibration purposes of the Raman part of SuperCam using the wavenumbers proposed in this work.

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