 earth at 'et'
      % in the J2000 frame without aberration correction.
      %
      [pos, et] = <a href="cspice_spkpos.html">cspice_spkpos</a>( 'MOON', et, 'J2000', 'NONE', 'EARTH' );

      %
      % Convert the array of position vectors 'pos' to spherical
      % coordinates.
      %
      [r, colat, lon] = <a href="cspice_recsph.html">cspice_recsph</a>(pos);

      %
      % Convert the spherical to rectangular.
      %
      [rectan] = <b>cspice_sphrec</b>(r, colat, lon);

      %
      % Calculate t