 = size(raydir); double = class(raydir)

      rframe   the string naming the reference frame associated with
               the input ray's direction vector 'raydir'.

               Since light time corrections are not supported for
               rays, the orientation of the frame is always evaluated
               at the epoch associated with the observer, as opposed
               to the epoch associated with the light-time corrected
               position of the frame center.

               [1,c2] =