Comparison of light scattering by stochastically rough spheres, best-fit spheroids and spheres

We compute light scattering by stochastically deformed spheres using a volume integral equation formalism. For computational reasons we are restricted to volume equivalent size parameters less than about eight for a collection of particles in random orientation. To see how well light scattering by rough particles can be approximated by using equal volume spheroids (computed by the T-matrix method) or by spheres (computed using Mie theory), we compute standard deviations between the different models for the intensity and linear polarization. As expected, a spheroid is a much better approximation than a sphere, particularly in the case of linear polarization. Only as an exercise we assume a power law distribution of particle sizes and compute light scattering by our realizations the intensity shows a distinct opposition spike close to backscattering and linear polarization is qualitatively astonishingly close to that observed for atmosphere less solar system objects. (C) 1998 Elsevier Science Ltd. All rights reserved.