Modelling the Space Debris Evolution : Two New Computer

Two computer codes to simulate the long term evolution (100 years) of the Earth orbiting debris have been developed under a contract of the Euro-pean Space Agency. In one of them, called Semi Deterministic Model (SDM), the goal was to accurately follow the orbital evolution of the population, so that each large object (and a sample of the small particles) is individually propagated with a semi-analytical orbit predictor. In the other one, called STochastic Analog Tool (STAT), the population is divided in a large number of mass, eccentricity and semi-major axis bins and we follow the evolution of the number of objects in each bin, with the advantage of a reduced CPU time consumption. Explosions, collisions, launches and active retrievals are accurately simulated with common models developed for both the codes. A large number of options in the input les permit the simulation of many long term scenarios, with diierent launch policies, explosion rates and retrievals strategies, to study the outcome of possible mitigation measures. The paper presents a description of the programs.