Wavelength Calibration for the LIBS Spectra of the Zhurong Mars Rover

Abstract

China’s first Mars rover, Zhurong, landed on the southern region of Utopia Planitia, Mars, on 14 May 2021 (UTC). Zhurong is equipped with the Mars Surface Composition Detection Package (MarSCoDe), which analyzes the Martian surface’s material composition. Composed of laser-induced breakdown spectroscopy (LIBS), short-wave infrared spectroscopy (SWIR), and a microimaging camera, MarsCoDe can work at a distance of 1.6–7 m to analyze element abundance and the mineralogy of targets on the Martian surface. Analysis shows that the wavelengths of MarSCoDe onboard LIBS spectra acquired within the same probe period will have different degrees of drift, leading to deviation in qualitative and quantitative elemental analysis. This paper finds that the spectrum drift follows a quadratic function relationship with the CCD temperature of the MarSCoDe spectrometer, based on which a wavelength calibration method is established. According to the function, the drift of a certain channel is calculated by the corresponding CCD temperature, and then the wavelength of the spectrum is calibrated by the drift. The accuracy of this calibration method for the position of peak wavelength in the LIBS spectrum can reach about 1/5 of the apparatus spectral width, and the cross-validation analysis using a norite standard sample shows that it is comparable to the wavelength calibration accuracy of the ChemCam onboard data product.

Alkali Trace Elements Observed by MarSCoDe LIBS at Zhurong Landing Site on Mars: Quantitative Analysis and Its Geological Implications

“…In theory, the spectral resolutions of UV, VIS, and VNIR are 0.19, 0.31, and 0.45 nm/pixel, respectively (W. Xu et al., 2021). The instrument is accompanied by 12 MCCTs: 10 powder pellets including andesite, basalt, montmorillonite, nontronite, olivine, hypersthene, K‐feldspar, gypsum, dolomite, and apatite (X. Liu et al., 2023), which are primarily used for compositional reference (e.g., Chen et al., 2022); one titanium alloy plate for wavelength calibration (e.g., Y. Zhang et al., 2023); a norite glass provided by France Institut de Recherche en Astrophysique et Planétologie (IRAP) for the cross‐calibration of LIBS instruments on Mars (Fabre et al., 2011). These 12 MCCTs are located at the back antenna's beam of the rover and approximately ∼1.7 m away from the 2‐dimensional pointing mirror.…”

Accurate multi-region wavelength calibration method for the spectrometer

“…The spectrometer is a scientific instrument that can decompose polychromatic light into spectral lines. In recent years, it has been widely applied in many fields including material analysis [1,2] , remote sensing [3,4] , and medical diagnosis [5,6] . The wavelength position and spectral resolution are two very important technical indices for spectrometers.…”