        T(et) - O(et)

      and a velocity obtained by taking the difference of the
      corresponding velocities. In the geometric case, the
      returned velocity is actually the time derivative of the
      position.


      Reception case
      ==============

      When any of the options &quot;LT&quot;, &quot;CN&quot;, &quot;LT+S&quot;, &quot;CN+S&quot; is selected
      for `abcorr', spkezr_c computes the position of the target body at
      epoch et-lt, where `lt' is the one-way light time. Let T