Comparison of quasi-specular radar scatter from the moon with surface parameters obtained from images

Quasi-specular radar scatter from geologic surfaces displays a variable wavelength dependence in apparent surface roughness. Wavelength dependence will occur whenever a significant fraction of the surface has local radii of curvature comparable to the observing wavelength. This condition can be determined by comparison of the value of the integrated surface curvature spectrum with the radar wavenumber, multiplied by a constant that depends on the geometry. Variations in curvature statistics calculated from photogrammetric reduction of lunar images are consistent with the observed variations in quasi-specular scatter at the same locations. Variations in the strength of the wavelength dependence are correlated with the sizes of lunar craters that lie near the upper size limit for the local steady state distribution. This correlation is also consistent with variations in the curvature spectrum calculated from crater size-frequency distributions