An evaluation index for the ranking of LEO objects

A novel index, the Criticality of Spacecraft Index (CSI), designed to rank the environmental criticality of abandoned objects in LEO is presented and tested on a sample population of orbiting objects. The CSI takes into account the physical characteristics of a given object, its orbit and the environment where this is located. It can be computed either for a specific epoch or as an average for a given interval of time. The CSI has a simple analytic formulation easy to catch and compute. The CSI distribution for LEO objects in the initial population at the epoch of January 1, 2020 and mass larger than 100 kg is computed and shown. It is shown how the definition presented is a good proxy for the future collision risk and how it can help in the definition of active removal scenarios, e.g., in the ranking of the perspective mission targets.