       otherwise it is SPICEFALSE.


   lit         is a logical flag indicating whether the surface point
               is illuminated; the point is considered to be
               illuminated if the vector from the point to the center
               of the sun doesn't intersect the target surface. `lit'
               takes into account whether the target surface casts a
               shadow on `spoint', regardless of the solar incidence
               angle at `spoint'. `lit' is returned with the value