Chandrayaan-3 LIBS Sensor: Preflight Characterization, Inflight Operations, and Preliminary Observations

The laser-induced breakdown spectroscopy (LIBS) sensor on the Chandrayaan-3 rover, Pragyaan, is the maiden LIBS technique-based instrument to operate on the airless planetary body, the Moon. This miniaturized low-energy eye-safe LIBS (LE-LIBS) instrument performs in situ elemental investigations on the lunar surface from a close distance of 0.2 m. The LE-LIBS instrument is equipped with a compact Yb:Er:Glass <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.54~\mu $ </tex-math></inline-formula>m pulsed laser for material surface ablation and a free-space optics-coupled flat-field spectrometer to record the microplasma emission. Before the voyage, the flight instrument was characterized to assess its performance as a function of operating conditions, viz., temperature, working distance, sample form, etc., in high vacuum (HV). Performed first-cut univariate analysis resulted in <5% uncertainty in elemental abundance estimation. Over 740 LIBS spectra of the lunar regolith are recorded at 25 different sites surrounding the “Shiv Shakti” point in the southern high latitude on the Moon. Preliminary analysis of the LIBS spectra recorded in regions a few meters away from the landing point has indicated the presence of elements, viz., O, Mg, Al, Si, Ca, Fe, Ti, Mn, Cr, etc., hinting at the possible presence of Ca, Al-rich silicate minerals, and low-Ti magnesium iron silicate minerals. In this article, we report salient engineering details of the instrument, preflight characterization, inflight functionality, and preliminary performance aspects.