A Stochastic Source-Sink Framework for Orbital Debris

Orbital debris poses a risk to the expanding governmental and commercial use of Earth orbit. In particular, the rising orbital populations increase the risk that debris growth renders parts of the orbital environment challenging or even unviable for satellite operation. Source-sink evolutionary models are useful for rapidly assessing the impact of various parameters on the orbital population. However, these models, as currently applied, provide insight into only a single evolution of the orbital population. Here, we present a stochastic framework for source-sink models that samples the full probability distribution of population outcomes given a set of rates for relevant processes (e.g., launch, decay, and collisions). We apply our model to investigate the impact of the satellite launch rate, the post mission disposal (PMD) rate of satellites, and noncompliance with PMD in the LEO orbital regime between 5002000 km. Our model indicates that the LEO orbital regime can become unstable under the 25year rule for PMD if the total number of satellites launched grows by roughly a factor of 24 over the current total. However, using a 5year PMD rule mitigates this risk. Significant rates of noncompliance with the PMD rule can limit the stability of the satellite population in the orbital regime, even under the 5year rule.