AAS 95-411

Semi-Autonomous Spacecraft On-Board Ephemeris Propagation

A. H. Salama and J. Kangas, Jet Propulsion Laboratory, Pasadena, CA

Abstract

Autonomous navigation can be accomplished by automating and migrating orbit determination, trajectory propagation and maneuver design to the spacecraft. This paper is concerned only with semi-autonomous on-board trajectory propagation. Two strategies are presented. One implements a semi-analytic method and rectifies, when needed, a simple on-board (on-line) ephemeris. The method is called rectification in which only several parameters are uplinked to the spacecraft infrequently. The other strategy applies the lessons learned from TOPEX/POSEIDON ephemeris representation to build a data compression device for a wide range of orbits. A trade-off study is conducted to relate accuracy requirements with semi-major axis and eccentricity to minimize frequency of uplinking.