Perturbation methods for satellite orbits

The literature in astrodynamics abounds with perturbation techniques for satellite orbits. Various formulations have been generated in terms of orbit elements, the satellite position and velocity vectors, or combinations thereof. The computational effectiveness of any perturbation scheme depends largely on the definitions used for the dynamic state variables. Some methods are aimed at long-range predictions and orbit lifetime studies, others at short-range predictions for guidance. This paper may serve as an introduction to this field for the nonspecialist, in that it reviews the classical variation-of-parameters technique and discusses several engineering analyses that were generated in the post-Sputnik era. It also points to some connections between these relatively simple approaches and more elaborate methods of celestial mechanics. Thus it may contribute toward a comparison of several “professional” approaches whose relative merits are often debated among experts.