Comparison of scattering calculations for aggregated particles based on different models

Various theoretical methods and corresponding computer programs exist which can be used to compute electromagnetic scattering by a cluster of several arbitrarily shaped particles. The aim of this paper is to compare results of various theories to find the range of applicability of the different methods. At first some comments will be made on the programs employed: the order-of-scattering Mie program (OS-Mie), the discrete dipole approximation (DDSCAT) and the multiple multipole program (MMP). As examples, results for four spheres within varying distance will be compared. In addition computations of the scattering of one bigger transparent sphere with two smaller absorbing 'satellite' spheres and of the scattering of two small oblates will be presented. A table includes data to give a hint on the computational demands. (C) 1999 Elsevier Science Ltd. All rights reserved.