Semi-Autonomous Spacecraft On-Board Ephemeris Propagation

Two strategies are presented for semi-autonomous on-board trajectory propagation. 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 uses TOPEX/POSEIDON experience 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 the frequency of uplinking.