Non-singular and non-conventional orbit perturbation equations

The derivation of equations for fast orbital elements describing a perturbed orbital motion is discussed. The criteria necessary to select an appropriate set of orbital parameters are presented together with the equations necessary for determining the evolution of a satellite's position vector within an inertial reference frame. Nonsingular perturbation equations for near-circular and near-equatorial orbits are presented; the use of quasi-angles and difference elements are described. The derivation of nonconventional perturbation equations for quasi-slow elements in near-circular and near-equatorial orbits is obtained and an example revealing the applicability of the theory is provided.