A new data reduction approach for the Clementine NIR data set: Application to Aristillus, Aristarchus and Kepler


  • Stéphane Le Mouélic,

  • Yves Langevin,

  • Stéphane Erard


The Clementine spacecraft, launched in January 1994, has performed a nearly global surface mapping of the moon in eleven broad spectral bands at a resolution of ∼200 m. The UV-visible (UV/VIS) camera performed observations in five bands ranging from 0.415 to 1.0 μm, while the near infrared camera (NIR) acquired data in six spectral bands ranging from 1.1 to 2.78 μm. UV/VIS images are calibrated to ∼4%. The calibrated NIR data set is yet to be finalized due to instrumental problems. Independently of the calibration effort for the full data set which is under the responsibility of the PI team, we present here the first results of a heuristic approach to extract mineralogical information from raw images in regions of particular interest. We processed images of craters Aristillus, Aristarchus, and Kepler. We computed band ratios using 0.75, 0.9, 0.95, 1.0, 1.1, 1.25, 1.5, and 2.0 μm images to map the compositional heterogeneity and to discriminate between pyroxene, olivine, or feldspar rich areas. Absolute reflectance spectra have been derived using telescopic spectra as ground truth. High orthopyroxene and clinopyroxene contents have been detected and spatially mapped on Aristillus. Our results are in good agreement with previous studies in the case of Aristarchus and show additional details due to the improved registration. Two regions exhibit spectra consistent with a high proportion of olivine with <25% pyroxene. The rim of Kepler exhibits a strong feature at 2 μm correlated with the 1 μm feature, suggesting either a high orthopyroxene content or a very immature soil. Our method could be of interest for further investigations of the lunar surface using Clementine NIR data.