Assessments of the impacts of orbital fragmentations using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM)

This study evaluates the environmental impacts of orbital fragmentation such as an anti-satellite test, collision between two objects, and explosion. A debris environment evolutionary model named NEODEEM, jointly developed by Kyushu University and JAXA, is used to predict future populations and calculate collision probabilities after a fragmentation. This study focuses on characteristics of the fragmented objects, such as altitude, mass, and whether they belong to a Large Constellation (LC). When a fragmentation occurs at higher altitudes, the new fragments will remain in orbit for a long time. Due to this accumulation, the fragments will not only keep the number of objects and probability of collision higher but also cause the risk of secondary collisions between fragments and background objects. When a collision occurs inside an LC at a lower altitude, the impacts will be short-term because most of fragments decay quickly. However, the number of conjunctions, i.e., operational roads, will increase rapidly because many satellites are operated at the same altitude. This study also discusses a collision probability to an LC taking into account the small size of fragments larger than 1 cm.