Baseline Values and Sensitivity Analysis of the THEMIS Space Debris Index

Fragmentations caused by explosions or collisions contribute a significant share of the growing space debris population. These present a risk to active spacecraft and have caused collisions in the past. Each satellite has the potential to fragment and thereby threaten spacecraft in its vicinity. Politecnico di Milano developed a tool for Tracking health of environment and missions in Space (THEMIS) under a European Space Agency (ESA) project. It quantifies a mission’s environmental impact using a space-debris index based on the Environmental Consequences of Orbital Breakups (ECOB) approach. In this approach, the probability and severity of a potential fragmentation are combined. THEMIS is undergoing beta testing and is being upgraded in a follow-up project. Since the approach is new, questions about interpreting the Index values have been raised. In this paper, reference values for selected missions in LEO and MEO, covering Earth observation, telecommunication and navigation applications are investigated. The sensitivities of index changes to orbital parameters, satellite properties and collision avoidance as well as post mission disposal strategies are estimated.