“…Usually, it consists of the mother satellite of mass m 1 moving in an unperturbed Kepler circular orbit and the sub-satellite of mass m 2 attached to the mother satellite through an elastic massless tether of length l(t). Although active debris removal using a tethered tug-debris system is a relatively new topic, several books [88][89][90] and hundreds of scientific articles have been already published [90][91][92][93]. However, many aspects of this problem remain unexplored.…”