Elsevier

Icarus

Volume 72, Issue 2, November 1987, Pages 342-357
Icarus

Photometric properties of lunar terrains derived from Hapke's equation

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Abstract

The photometric parameters of B. W. Hapke's (1986, Icarus 67, 264–280) equation are fit to the lunar disk-integrated visual lightcurve and to disk-resolved data of R. W. Shorthill, J. M. Saari, F. E. Baird, and J. R. LeCompte (1969, Photometric Properties of Selected Lunar Features, NASA Contractor Report CR-1429) for dark, average, and bright lunar terrains. The lunar nearside geometric albedo and phase integral computed from the disk-integrated results are consistent with those of earlier investigators. The single scattering albedos of disk-resolved average and bright lunar terrains are systematically larger than that of lunar mare. Average particles in dark terrain regoliths are more backscattering than those in average and bright lunar terrains. The angular width of the opposition surge is greatest in dark terrains and is found to be best explained by modest differences in regolith particle-size distributions which might accompany the normal regolith maturation process. The total amplitude of the opposition surge for dark terrains is larger than for average and bright terrains. This result appears to be a consequence of the fact that in opaque particles, a larger fraction of singly scattered light at zero phase comes from first-surface reflection. The average subcentimeter macroscopic roughness of dark terrains is significantly lower than that of average and bright terrains. The relative magnitude of this difference is consistent with that obtained from radar measurements at decimeter scales.

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