Examination of SGP4 along-track errors for initially circular orbits

摘要

This paper examines the SGP4 orbit propagation equations for the specific case of an initially circular satellite orbit, with the aim of understanding the along-trajectory errors that are observed in practice. In particular, the SGP4 equations are compared with analytic expressions obtained by means of a regular perturbation expansion and two discrepancies have been found in the along-track angle u, both of order J(2) (the primary earth oblateness term):