On checking the calculations of the optical properties of
                    non-spherical particles

             V G Farafonov^1 and V B Il'in^2

   ^1 St.Petersburg University of Aerocosmic Instrumentation,
      Bol.Morskaya ul. 67, St.Petersburg 190000, Russia

   ^2 Sobolev Astronomical Institute, St.Petersburg University,
      Bibliotechnaya pl. 2, St.Petersburg 198504, Russia


                       Abstract

All mathematical and computational problems of the light scattering theory
for spherical particles (Mie theory) are well studied and resolved.
However, they still remain to tackle in the case of non-spherical
particles. This requires systematical testing of
corresponding numerical algorithms and codes.

We consider different aspects of such checking:
(i) reliability of the internal convergence test
in view of our recent analytical and numerical investigations
of some light scattering methods;
(ii) efficiency of checking based on the reciprocity relation;
(iii) new possibilities of comparison with other methods
that are being opened by the developing WWW
database of optical properties (DOP) of non-spherical particles.
 In particular,
a general class of scatterers (called ``weakly-Rayleigh scatterers")
to which the internal convergence test should be applied with great care
is determined.
 The reciprocity relation is shown to be a useful test
(under some conditions), specifically for absorbing scatterers.
 The DOP will contain original codes and well checked (benchmark) results
as well as information on the light scattering theory
that can be helpful in researches, applications, and education.