Atmospheric density fluctuations due to solar modulation & orbital debris modeling

The majority of manmade debris in Earths orbit is related to the breakup of satellites and their propulsion systems. Since the first major satellite breakup in 1961, there has been increasing concern about the hazards posed by orbital debris. Some orbits may contain very large numbers of objects of varying shapes and sizes, while others contain very few. Currently there are a number of models that are used to predict the future debris environment. The two greatest sources of uncertainty in these models are atmospheric drag in low orbits, and debris fragmentation. The atmospheric drag on orbiting debris varies as the atmosphere expands and contracts due to solar modulation. Fragmentation models are vital for the estimation of current and future debris populations. Current fragmentation models are built on empirical fits to experimental data, and observed debris populations. While these models adequately describe large debris objects, there is a large amount of uncertainty with respect to small sized debris. Therefore, there is an ongoing effort to develop alternative models that are able to make predictions based on physical arguments.