  | \     |
          |  \    |
          |   \   | T(et-lt) - O(et)
          |    \  |
          V     V V
         T(et)  T(et-lt)

      The position component of the light time corrected state
      is the vector

         T(et-lt) - O(et)

      The velocity component of the light time corrected state
      is the difference

         T_vel(et-lt)*(1-d(lt)/d(et)) - O_vel(et)

      where T_vel and O_vel are, respectively, the velocities of the
      target and observer relative to the solar system bar