Journal of Quantitative Spectroscopy & Radiative Transfer 79–80 (2003) 1121–1137 www.elsevier.com/locate/jqsrt Orientation-averaged radiative properties of an arbitrary conguration of scatterers Yu-lin Xu a ; ∗ , Nikolai G. Khlebtsov b a Department of Astronomy, University of Florida, P.O. Box 112055, Gainesville, FL, USA b IBPPM, Russian Academy of Sciences, Prospect Entuziastov 13, Saratov 410015, Russia Received 31 May 2002; accepted 11 October 2002 Abstract We discuss both analytical and numerical methods in calculating radiative scattering parameters of a ran- domly oriented ensemble of particles. There exist two approaches to rigorously solving multiparticle scattering. One is the generalized multiparticle Mie-solution (GMM) and the other is cluster T -matrix approach (CTM). We show that, the same as in the case of xed-orientation scattering, the random-orientation formulations of GMM and CTM have a remarkable contrast in capability of handling the overall dimension of an ensemble of particles in practical applications. We also show that the use of a standard scheme of numerical quadrature could be more ecient than straightforwardly taking an unweighted arithmetic average in discrete orientational averaging. ? 2003 Elsevier Science Ltd. All rights reserved. 1. Introduction Accurate predictions of light-scattering characteristics of partially aligned or randomly oriented ensembles of scatterers are highly desirable for a great variety of important practical applica- tions. Orientation-averaged scattering parameters can be obtained by integrating either numerically over discrete or analytically over continuous particle-orientations. These are based on xed- and random-orientation scattering solutions, respectively. Following the pioneer work of Liang and Lo [1] and Bruning and Lo [2] two approaches have been reported to rigorously solve the scattering by an ensemble of particles, which lead to two multisphere scattering far-eld solutions that appear at rst sight to be alike but are substantially dierent [3]. One is the cluster T -matrix approach (CTM) initiated by Peterson and Str om [4]. The other is used in the generalized multiparticle Mie-solution (GMM) [5–12]. Several GMM and CTM codes for calculating either xed- or random-orientation * Corresponding author. Tel: +352-3922052; fax: +352-3925089. E-mail address: xu@astro.u.edu (Y.-l. Xu). 0022-4073/03/$ - see front matter ? 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0022-4073(02)00345-X