Earth-Orbiting Debris Cloud and Its Collisional Evolution

The growing hazard related to the proliferation of Earth-orbiting debris is leading to the study of realistic models for the long-term evolution of this population. Few source and sink mechanisms affect the evolution: launches and explosions provide new material, partially subject to human control, the object decay to lower shells due to the atmospheric drag (according to their altitude and area to mass ratio) and finally the orbiting objects can undergo high-velocity mutual collisions which affect their size distribution by generating swarms of fragments, playing the role of potential new projectiles. In order to simulate the collisional evolution of the debris population, we calculated the actual intrinsic collision probabilities for the orbiting objects for each altitude. We also developped a numerical algorithm to model the future collisional evolution of the low-orbiting Earth debris population. Our simulations show that the sensitivity of the results to future launch and/or deorbiting and removal policy is rather weak, so that drastic measures will nead to be taken soon in order to significantly avoid or delay a catastrophic outcome.