The effects of scattering geometry on the spectrophotometric properties of powdered material

The characteristics of reflectance spectra are being used as a basis in investigations to infer the composition of planetary surfaces. However, the reflectance spectra of powdered materials depend not only on the composition of these materials, but also on other variables. A description is presented of the results of an exploratory series of measurements designed to investigate the importance of scattering geometry as a variable in determining the shapes of spectral reflectance curves, taking into account half a dozen materials of planetary interest. It is noted that the considered results are consistent with those reported by Adams and Felice (1967), especially the results on the variation with phase angle of the Red/Blue color ratio for various silicate materials. The measurements demonstrate in detail that scattering geometry does affect the shapes of spectral reflectance curve. In some cases this effect is quite significant.