We introduce a refined formulation of the Fragmentation Environmental Index (FEI), designed to assess changes in the Low Earth Orbit (LEO) environment resulting from the fragmentation of a specific mass. The index quantifies this impact by comparing overall LEO criticalities before and after the fragmentation event. To highlight the contribution of smaller debris, we enhance the index by incorporating weighting factors tailored to optical and radar surveillance networks. Testing of the upgraded FEI on a series of simulated fragmentation events shows that it can characterize both the perturbation to the LEO environment and its temporal evolution, providing a more accurate quantification of the short- and medium-term impact of debris clouds compared to the original formulation.

Building on the definition of the Criticality of Spacecraft Index [1] and of the Shell Criticality [3], a procedure and an index able to quantify and visualize the medium term effects on the environment of a fragmentation in Low Earth Orbit is derived. The index takes into account the change in the environment caused by the fragmentation of a given mass in a specific orbit by quantifying the contribution of the fragments with respect to the original situation where the whole fragmented mass was contained in the intact objects. The index is devised in the frame of added-value SST services, such as the fragmentation detection and impact evaluation service. Thus, weighting factors are included in its formulation to highlight the contribution of the debris created in a given event, leveraged by the capabilities of a given observing network (either optical or radar). The index is applied and tested on a few simulated fragmentations. The results show that the index is able to characterize the perturbation to the environment due to the cloud of fragments and its temporal evolution. In particular, the new weighting factors are able to properly highlight the capability of a given SST network to observe and characterize a fragmentation happening in a Low Earth Orbit region.