Q:  What is the period of this orbit?  Express your answer in days,
             and in seconds.


         The graph shows 3 periods over the timespan from

               start = 441   days
               end   = 456   days

         So
                        (456 - 441) days
                  P  =  ------------------  =  5.0 days
                              3


                     =   4.32 x 10^(5)   seconds



         (Fetherolf et al. derive a period of 5.069482 days,
           so this very rough estimate isn't too bad)