Scanning time-resolved standoff Raman instrument for large-area mineral detection on planetary surfaces

Abstract

A S canning St andoff R aman S pectroscopy (SSTRS) system has been developed to map out the spatial distributions of selected minerals at long distances (10–100 m). The SSTRS is based on a standoff Raman system, which is mounted inside a custom pan and tilt scanner. Computer software is used to control the direction of the pan-tilt scanner and to point the laser beam onto the distant samples. Measurements are made in an x-y grid pattern on a target area defined by the user. The Raman spectra collected at each grid point are processed to identify the distribution of minerals present from their respective Raman fingerprints. In the initial experiment, the Raman spectra of barite (BaSO 4 ), gypsum (CaSO 4 ·2H 2 O), plagioclase feldspar (solid solution of NaAlSi 3 O 8 -CaAl 2 Si 2 O 8 ), α -quartz ( α -SiO 2 ) rocks, and silica glass were measured at 30 m distance. The Raman spectra at the grid points are measured and processed to obtain a Raman mineral image of the distant minerals by selecting respective Raman fingerprints of α -quartz, gypsum and plagioclase feldspar. The ability to provide interpolated Raman images of distant mineral species is illustrated. The new SSTRS system works well and now offers the ability to obtain spatial distribution maps of distant mineral species from their Raman fingerprints.