AN ANALYSIS OF STATE VECTOR PROPAGATION USING DIFFERING FLIGHT DYNAMICS PROGRAMS

摘要

Since the demonstration of the first numerically generated space catalog by the United States Navy in 1997, the issue of how to transition from the two-line element sets (TLEs), to routine use of numerical vectors in satellite flight dynamics operations is generating some unique challenges. Specifically, how will organizations efficiently interact with and use orbital data from programs outside their control. The historical TLE operations used analytically generated datasets for a majority of their calculations which required strict adherence to a specific mathematical technique. Use of numerical techniques presents different challenges even though the underlying mathematical technique is the same. This paper provides results of an experiment in which various initial state vectors, representing a cross-section of the existing satellite population, were propagated from several days to a month. The ephemerides, created by several legacy flight dynamics programs, are compared to ephemerides from Analytical Graphics Inc.'s Satellite Tool Kit (STK). There is no assertion of right or wrong answers within the comparisons, rather, the relative differences are shown to gauge the effectiveness of the setup for each case. Most of the comparisons show that mm to cm-level comparisons are possible with careful attention to parameters. Differences are discussed including potential error sources. One goal is to present a format that simplifies transmission and use of state vector information between programs, seeking a standard for better integration of interoperability. This will avoid significant expenses in using entirely new, or unavailable software. Tables are presented to demonstrate the effect of various force models and their contribution to the satellite orbit. Finally, sample ephemeris information, potential new formats to exchange data, and STK scenario setups are included to initiate a community forum on numerical ephemeris propagations.