Published online by Cambridge University Press: 04 July 2016
For many space applications, such as communication, weather, military, and scientific experiment satellites scanning precise regions, it is necessary to maintain a satellite in a fixed orientation relative to the earth. Unfortunately, a correctly positioned satellite deviates with time from this preferred orientation due to perturbing environmental forces. This explains considerable interest in libra-tional stability study in recent times.
Among the numerous methods developed for librational control, a passive technique depending on the gradient of the gravitational field has gained attention. Depending on the orbital distance, environmental effects, such as, aerodynamic, radiation, and magnetic torques, become significant compared to the gravity-gradient restoring moment. A need to determine the influence of these disturbing forces is thus evident.