COMPARING LONG-TERM PROJECTIONS OF THE SPACE DEBRIS ENVIRONMENT TO REAL WORLD DATA - LOOKING BACK TO 1990

摘要

Long-term projections of the Space Debris environment are commonly used to assess the trends within different scenarios for the assumed future development of spacefaring. General scenarios investigated include business-as-usual cases in which spaceflight is performed as of today over mitigation scenarios, assuming the implementation of space debris mitigation guidelines at different advances or the effectiveness of more drastic measures, such as active debris removal. One problem that always goes along with the projection of a system's behavior in the future is that affecting parameters, such as the launch rate, are unpredictable. It is common to look backwards and re-model the past in other fields of research. This is a rather difficult task for spaceflight as it is still quite young, and furthermore mostly influenced by drastic politic changes, as the break-down of the Soviet Union in the end of the 1980ies. Furthermore, one major driver of the evolution of the number of on-orbit objects turns out to be collision between objects. As of today, these collisions are, fortunately, very rare and therefore, a real-world-data modelling approach is difficult. Nevertheless, since the end of the cold war more than 20 years of a comparably stable evolution of spaceflight activities have passed. This period is used in a comparison between the real evolution of the space debris environment and that one projected using the Institute of Space System's in-house tool for long-term assessment LUCA (Long-Term Utility for Collision Analysis). Four different scenarios will be investigated in this comparison; all of them have the common starting point of using an initial population for May 1990. The first scenario, which will serve as reference, will simply be taken from MASTER-2009. All launch and mission related objects from the Two Line Elements (TLE) catalogue and other available sources are included. All events such as explosion and collisions events have been re-modelled as close to the reality as possible and included in the corresponding population. They furthermore have been correlated with TLE catalogue objects. As the latest available validated population snapshot for MASTER is May 2009, this epoch is chosen as endpoint for the simulations. The second scenario uses the knowledge of the past 25 years to perform a Monte-Carlo simulation of the evolution of the space debris environment. Necessary input parameters such as explosions per year, launch rates, and the evolution of the solar cycle. The third scenario goes a step further by only extracting mean numbers and trends from inputs such as launch and explosion rates and applying them. The final and fourth scenario aims to disregarding all knowledge of the timeframe under investigation and inputs are determined based on data available in 1989 only. Results are compared to the reference scenario of the space debris environment.