“…The huge amount of objects (up to millions) in LEO, MEO, GEO needs a careful control of their orbits and the analysis of their dynamical stability ( [6,3,5,4,15,31]), also in view of devising appropriate mitigation measures (see, e.g., [17,27,9]). For objects in LEO, it is of crucial importance to evaluate the orbital lifetime, which is strongly affected by the atmospheric drag which provokes a decay of the orbits ( [19,22,24,32,34]).…”