<h2>AAS 95-367</h2><h2>Statistical Performance of TOPEX/POSEIDON Prime Mission Ground and On-Board Ephemerides and Consequences for the Extended Mission</h2><h4>J. Kangas and A. H. Salama, Jet Propulsion Laboratory, Pasadena, CA</h4><h2> Abstract </h2>TOPEX/POSEIDON is a joint American/French ocean topography experiment, currently in the last year of its nominal mission and soon to enter a three year extended mission.  To meet science requirements, the satellite must point the altimeter accuracy of the Operational Orbit Ephemeris and its Fourier power series representation in the On-Board Computer.  The consequences for the extended mission due to this performance will be also discussed.<br><br>