A Quantitative Evaluation of the Environmental Impact of the Mega Constellations

The main focus of this work is to highlight the main parameters driving the future evolution of the debris environment, in presence of the planned LEO mega constellation of satellites. The goal is to define the best management practices, able to minimize the debris production in the future. First, in order to identify the most important parameters that are actually driving the evolution of the environment and in an effort to discrimiate between possibly equivalent scenarios, we applied tools from the statistical sciences, namely the Wilcoxon signed rank test, i.e., a nonparametric test which, without assuming normality in the data, allows us, given two samples, to assess whether their population mean ranks differ. Then, building on the index described in [6] and [3] and on the analysis of the simulations performed in the aforementioned studies, by means of a simplified model of the constellation building and managing, we define an index able to quantify the environmental impact of the mega constellations. The index takes into account the physical and orbital characteristics of the constellation satellites, along with the mitigation practices adopted for each constellation. Based on the expected collision risk and the capability of avoiding impacts, the operational and non-operational satellites and the related upper stages, present in each constellation, enter the index computation with different relative weights to properly account for the global constellation effects on the environment. An averaged, time evolving, index computed on altitude shells can give quantitative and visually effective indication of the effectivenes of the mitigation practices applied by a constellation operator. The model and the associated index, along with other metrics described in [6] and [4], allows us not only to highlight the prominence of some of the parameters entering in the definition of a satellite constellation but also to "predict" the influence that a change in that particular parameter is going to produce on the long term evolution of the environment. The metrics and the index are applied to the results of a sub-sample of the long term simulations, showing the relative importance of different design parameters and allowing a better ranking of possible mitigation measured. In the simulated scenarios, the parameters playing a major role in the effect that a mega-constellation cause on the environment are: the mass and the area of the satellites, the failure rate in the operational orbit and the collision avoidance success rate.