


   srfvec      is the vector from the observer's position at `et' to
               the aberration-corrected (or optionally, geometric)
               position of `spoint', where the aberration corrections
               are specified by `abcorr'. `srfvec' is expressed in the
               target body-fixed reference frame designated by
               `fixref', evaluated at `trgepc'.

               The components of `srfvec' are given in units of km.

               One can use the CSPICE function <a h