Photometric properties of the lunar surface derived from Clementine observations

Abstract

Photometric properties of the lunar surface in visual and near‐infrared light were studied using raw images obtained with UVVIS camera during the Clementine mission. The investigation focused on several specific regions on the lunar surface, each of which was observed by Clementine at a variety of different illumination and viewing geometries. Through these observations, the dependence of the surface brightness on the observation/illumination geometry was studied. It was shown that the disk component of this dependence, that is, the variations of brightness at constant phase angle, is different for different mare areas. The color of the lunar surface also changes with changing of the observation/illumination geometry, even if under constant phase angle. The Reiner Gamma formation displays unusual photometric properties. They are consistent with the surface being smoother than the typical mare regolith surface. The UVVIS images taken at the smallest phase angles were used to study the opposition spike, that is, the sharp increase of the surface brightness near the opposition. Steepness of the phase dependence of brightness varies over a wide range for different sites.