The Thales Alenia Space study team completed a 13 month contract to study the feasibility of Active Debris Removal within mega-constellations. Within the Clean Space initiative, ESA searches for proactive answers to the environmental challenges which are faced both on Earth and in space. The Inter-Agency Space Debris Coordination Committee (IADC) has already highlighted the important topic of mega-constellations, which represent a step change in the future space environment due to the proliferation of small satellites. The study addresses the end-of-life disposal techniques considered for mega-constellations and the potential of Active Debris Removal solutions.