The Gaussian form of the variation-of-parameter equations formulated in equinoctial elements - Applications: Airdrag and radiation pressure

The Gaussian form of the equations for the variation of parameters is derived, particularly for the case of equinoctial elements. Equations are given for the true and eccentric longitudes as fast angular variables, and the perturbation is resolved along various mutually orthogonal components. The equations are applied to two cases of nonconservative perturbations: air drag and radiation pressure. Explicit first-order results are presented for the variation of the equinoctial elements and time after one revolution.