<h2>AAS 95-427</h2><h2>Analytic Orbit Model for U.S. Naval Space Surveillance:  An Overview</h2><h4>P. W. Schumacher, Jr., U.S. Naval Space Command, Dahlgren, VA, R.  A. Glover, General Research Corp., Colorado Springs, CO</h4><h2> Abstract </h2>For more than two decades, the catalog of Earth satellites has been maintained using analytical orbit models based mostly on Brouwer's 1959 artificial satellite theory.   Described here are several modifications of Brouwer's formulation, which were implemented for Naval space surveillance operations, but which may not be widely understood among users of cataloged element sets.  In addition, the main differences among several models currently used by components of United States Space Command for catalog maintenance are described.  The Naval orbit model is being upgraded both for improved accuracy for high-altitude orbits and for improved compatibility with the other main (Air Force) model, work which should noticeably benefit many users of cataloged elements.
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