In some cases it may be desirable to limit the calculations to a single incident polarization state - for example, when each solution is very time-consuming, and the target is known to have some symmetry so that solving for a single incident polarization state may be sufficient for the required purpose. In this case, set IORTH=1 in ddscat.par.
When IORTH=1, only 
and 
are available;
hence, DDSCAT cannot
automatically generate the Mueller matrix elements.
In this case, the output routine WRITESCA writes out the quantities
, 
, 
, and
for each of the scattering directions.
Note, however, that if IPHI is greater than 1, DDSCAT will automatically
set IORTH=2 even if ddscat.par specified IORTH=1: this is because
when more than one value of the target orientation angle 
is required, there
is no additional ``cost'' to solve the scattering problem for the second incident
polarization state, since when solutions are available for
two orthogonal states for some particular target orientation,
the solution may be obtained for another target orientation differing only in the
value of by appropriate linear combinations of these solutions.
Hence we may as well solve the ``complete'' scattering problem so that we can
compute the complete Mueller matrix.