Analysis of close approach and collision probability between operational satellites and/ or space debris

In recent years, the number of space debris has increased significantly, which can threaten the safety of operational satellites. In this paper we developed an accurate model for active satellite protection from collision in order to determine close approaches between two objects (satellites and /or debris) using the Hoot's method and the time of close approach. We calculate the minimum relative distance considering J2 and atmospheric drag perturbations, and compared it to the close approach distance. The Collision probability between two closed objects is calculated using Chan model and analyzed in a given time-scale to avoid any dangerous collision. We applied our models on the cataloged debris (more than 1000) resulted from the crash between Iridium 33 and Cosmos 2251; in addition, ten satellites from the Iridium satellites list at the same altitudes of the debris crowdie region are considered. The numerical results have shown one real case of close approach with high probability of collision that may threaten one of those active satellites.