Keplerian Motion VS Perturbed Motion The parameters pi are constant They are time dependent Thus, for the position and velocity vector of the perturbed motion. we have P=pt,p, (t)) p=pt,p, (o) 電 Principles of the Global Positioning System 20053-11(19 Disturbing Accelerations In reality, many disturbing accelerations act on a satellite and are responsible for the temporal variations of the Keplerian elements They can be divided into Gravitational. Nonsphericity of the Earth Tidal attraction(Direct and Indirect Non- Solar radiation pressure(direct and indirect gravitational,Air drag Relativistic effect Others(solar wind, magnetic field forces Principles of the Global Positioning System 2005-3-11(20 1010 Principles of the Global Positioning System 2005-3-11 19 Keplerian Motion vs. Perturbed Motion Principles of the Global Positioning System 2005-3-11 20 Disturbing Accelerations In reality, many disturbing accelerations act on a satellite and are responsible for the temporal variations of the Keplerian elements. They can be divided into: