the above assumptions, may be as large as (V/C)**2 * the
         distance between the observer and the uncorrected target
         position: 300 km or equivalently 6 km/AU.

      In practice, the difference between positions obtained using
      one-iteration and converged light time is usually much smaller
      than the value computed above and can be insignificant. For
      example, for the spacecraft Mars Reconnaissance Orbiter and
      Mars Express, the position error for the one-iteration light
  