The opposition effect of the moon: Coherent backscatter and shadow hiding

The electromagnetic scattering properties of Solar System regoliths are commonly interpreted using the lunar regolith as a prototype. Hence, a thorough understanding of the reflectance of lunar soil is essential to remote sensing planetary studies. We have measured the linearly and circularly polarized reflectances of samples of lunar soil in order to better understand the nature of the lunar opposition effect. Several independent observations show that the zero-phase peak is caused by both shadow hiding and coherent backscatter in roughly equal amounts. Any radiative transfer model for planetary regoliths must take this dual nature into account, The transport mean free path for photons in the lunar regolith is about 1 mu m, which is much smaller than the mean particle size. (C) 1998 Academic Press.