   vector. If the ray intersects the target body in
                         multiple points, the selected intersection point is
                         the one closest to the observer.  The output
                         argument 'found' (see below) indicates whether an
                         intercept was found.

                         [3,1] = size(surf(i).spoint)
                         double = class(surf(i).spoint)

                         'spoint' is expressed in Cartesian coordinates,
       