Distribution of Atomic Oxygen within the internal cavities of VLEO Satellites

Operating satellites at altitudes below 300km in Very Low Earth Orbit has many advantages. However, due to the higher atmospheric density of this region, satellites encounter a higher abundance of Atomic Oxygen in the Very Low Earth Orbit environment. Since some payloads require access to space, they are located within open cavities on the surface of the spacecraft. This may make them more susceptible to the corrosive nature of Atomic Oxygen at these lower altitudes. The work presented aims to analyse the Atomic Oxygen flux within these cavities to eventually be able to estimate the damage. This problem has been approached analytically and these results have been compared with results from Direct Simulation Monte Carlo. Useful relationships and simplifications have been identified. For example, it was shown that the maximum Atomic Oxygen flux inside a simple rectangular cavity or pit was experienced at the rim of the forward-facing panel. This flux was found to be approximately half the flux seen on the front of the satellite. It was shown that the angular distribution of particles through a point in space approximated a normal distribution. This meant that the flux distribution on the forward-facing surface could be approximated by the cumulative frequency distribution of this normal distribution. It is hoped that this work will be useful to those designing the configuration (especially that of the payload) of future Very Low Earth Orbit spacecraft.