       'ELLIPSOID'

                     The illumination angle computation uses a
                     triaxial ellipsoid to model the surface of the
                     target body. The ellipsoid's radii must be
                     available in the kernel pool.


                  'DSK/UNPRIORITIZED[/SURFACES = &lt;surface list&gt;]'

                     The illumination angle computation uses
                     topographic data to model the surface of the
                     target body. These data