Analytic Propagation for Satellites in Near-Circular Low-Earth Orbits

The present work is focused on providing an analytic model for the motion of an low-Earth-orbiting satellite. The model incorporates the two dominant perturbations, namely the atmospheric drag and the Earth oblateness. While the latter is modeled by the second zonal harmonic J 2 , both constant and exponential density distribution models of the atmosphere are considered. The satellite orbit is assumed to be almost circular. Closed-form equations of motion are obtained, even time-explicit in the case of a constant atmosphere. The analytic predictions are carefully validated against direct numerical simulations. The resulting model is suitable to be incorporated in onboard propagators for short-term orbit predictions