Effects of water and ice layers on the scattering properties of diffuse reflectors

Measurements were made of the angular distribution of power scattered from a diffuse reflector illuminated by a laser beam directed normal to the surface of the reflector. Experiments were performed on dry, wet, and ice-covered planar targets. They revealed that the diffuse component of scattered power from a wet or icecovered target is reduced by an amount proportional to the inverse of the square of the index of refraction of the layer, which is consistent with simple theory. Backscattered radiation from a water-or ice-covered target was found to be enhanced compared with that from a dry target in the region about a cone centered on the line normal to the target. The half-angles of the cones for dry, water-covered, and ice-covered targets were 2.5, 12.5, and 30 degrees , respectively. The large half-angles of the covered targets may be due to multiple reflections within the layer. Small air bubbles in the ice and the roughness of the ice surface may be responsible for the particularly large increase in half-angle of the ice-covered target.