quot;RADII&quot;, 3, &amp;dim, radii );

                 /.
                 Find the position of the center of Mars with respect
                 to MGS.  The position of the observer with respect
                 to Mars is required for the call to `<a href="surfpt_c.html">surfpt_c</a>'.  Note:
                 the apparent position of MGS with respect to Mars is
                 not the same as the negative of Mars with respect to MGS.
                 ./
                 <a href="vsub_c.html">vsub_c</a