<h2>AAS 99-142</h2>
<h2>Centimeter Level Orbit Determination for the Topex/Poseidon Altimeter                                                                            </h2>
<h4>J. Reis, B.D. Tapley                                                                                                                                                                </h4>
University of Texas, Austin                                                                                                                                               
<h2> Abstract </h2>
The ability to determine the radial component of the satellite orbit with sufficient accuracy to fully exploit the centimeter level precision of contemporary radar altimeters requires both high fidelity force models to describe the satellite motion and accurate tracking data which is well distributed temporally and geographically. Advances in these area have culminated in the routine determination of orbits for TOPEX/POSEIDEN with a current accuracy close to 2 cm radially. In this paper, the advancements in the models and orbit determination techniques for the TOPEX/POSEIDEN altimeter mission are discussed.