Istituto di Scienza e Tecnologie dell'Informazione     
Pardini C., Anselmo L. Review of the uncertainty sources affecting the long-term predictions of space debris evolutionary models. In: 3rd European Workshop on Space Debris Modelling and Remediation (CNES Headquarters, Paris, France, 16-18 June 2014).
From a purely mathematical point of view, the artificial debris population in low Earth orbit above 700 km is intrinsically instable, due to the physics of mutual collisions and the relative ineffectiveness of air drag in removing intact objects and fragments. However, from the practical point of view of space access and exploitation, the accurate evaluation of the time scale characterizing the expected pace of debris growth is of fundamental importance to factor in the operational impact, the technological advances, the economic consequences, and the possible need of remediation measures. Apart from the uncertainty of future launch traffic and space technology (they can be reasonably assessed for no more than twenty years), the predictions of the current long-term evolutionary models are strongly affected by a number of critical assumptions concerning the definition of catastrophic collision, the fragmentation threshold, the collision geometry and probability, and the mass, area and velocity distributions of the fragments. Any change in this set of hypotheses might have significant consequences on the time scale of debris growth and this explains the current renewed interest in satellite breakup tests carried out on the ground. Another relevant aspect affecting the expected confidence of long-term predictions is the accuracy of trajectory propagations. In low Earth orbit, in statistical terms and taking into account the long time spans generally considered, the chaotic orbital behavior induced by resonances is not significant (of course it might be so for single objects, but the overall picture is of interest here). However, the simulation outcome as a whole is strongly affected by any mismodeling of the most important non conservative perturbation, i.e. air drag, due to inaccuracies of the atmospheric density models, to long-term thermospheric changes, to wrong solar and geomagnetic activity predictions, to drag coefficient assumptions and so on. In addition, the situation can be radically changed by adverse intentional actions, as the Chinese anti-satellite test in January 2007. The Italian National Research Council (CNR) has been involved in the long-term modeling of orbital debris evolution since 1992. The aim of this presentation is to address and quantify (as much as possible) the hidden uncertainties of long-term evolutionary model forecasts, based on the experience matured in more than twenty years of activity in the field.
Subject Space Debris
Long-term Evolution
Model Uncertainty
70F15 Celestial mechanics

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