Effect of mitigation measures on the long-term evolution of the debris population

The relative effectiveness of mitigation measures on the long-term evolution of the orbital debris population was investigated in detail by using a new version of the Space Debris Mitigation (SDM) analysis tool, developed under ESA/ESOC contract. Starting from new initial conditions, updated to 1999, and from a future traffic model, the influence of the selective adoption of mitigation practices was determined over a lOO-year time span. The analysis included the suppression of the release of mission-related objects, the on-orbit explosion avoidance and the de- orbiting of upper stages in low earth orbit. A particular effort was devoted to study the long-term effect of different strategies of spacecraft disposal at the end of the operational life. The end-of-life disposal of low earth satellites in orbits of given residual lifetime, in between 0 and 50 years, was simulated to assess its potential long-term benefits for the debris environment below 20 km. Moreover, for geostationary and low earth satellites above 1400 km, the re-orbiting to higher altitudes was considered as well. The results show clearly that the explosion avoidance in orbit is quite effective and should be strictly applied. However, some form of de-orbiting will be needed to roughly stabilize the long-term debris collision risk in low earth orbit.