This option modifies the
                             intercept obtained with the 'XLT'
                             option to account for the observer's
                             velocity relative to the solar system
                             barycenter.

                  'XCN'      Converged Newtonian light time
                             correction.  This is the same as 'XLT'
                             correction but with further iterations
                             to a converged Newtonian