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Lunar opposition effect as inferred from Chandrayaan‐1 M 3 data
Author(s) -
Kaydash Vadym,
Pieters Carle,
Shkuratov Yuriy,
Korokhin Viktor
Publication year - 2013
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/jgre.20098
Subject(s) - coherent backscattering , brightness , opposition (politics) , wavelength , optics , physics , astrophysics , geology , spacecraft , imaging spectrometer , phase change , phase (matter) , geodesy , astronomy , spectrometer , scattering , engineering physics , quantum mechanics , politics , political science , law
The shadow‐hiding and coherent backscattering enhancement mechanisms are considered to be the major contributors to the brightness opposition effect of the Moon. However, the actual proportions of the mechanisms at different phase angles still remain not well determined. In order to assess the lunar phase function across small phase angles, we utilize imaging spectrometer data acquired by the Moon Mineralogy Mapper (M 3 ) onboard the Chandrayaan‐1 spacecraft. We calculated phase functions of apparent reflectance and color ratios in the wavelength range 541–2976 nm for several mare and highland areas. As inferred from changes in the wavelength dependence of the phase curves, the shadow‐hiding effect is a major component of the brightness opposition surge at phase angle > 2°. The coherent backscattering enhancement may contribute some to the opposition effect at phase angles < 2°. We found nonmonotonic behavior of color‐ratio phase curves that reveal the minimum at ~ 2–4°. Using lunar observations, this is the first reliable evidence of the colorimetric opposition effect found earlier for lunar samples.