Face-dependent impact probabilities, velocities and angles upon LDEF by space debris and natural meteoroids

For specified geocentric orbits the impact probabilities, velocities and angles upon the different faces of the Long Duration Exposure Facility (LDEF) are calculated, and it is found that quite different distributions of micro-cratering are to be expected. In particular the flux to the East (leading) face should exceed that to the West (trailing) face by a very large ratio. The North and South faces receive exposures slightly in excess of the East face for lower-velocity impacts from low-inclination orbits, but much lower exposures than the East face for high-velocity impacts from high-inclination orbits. The Space face (pointing directly away from the Earth) and the Earth face (pointing directly towards the Earth) will have been subject to very few impacts from geocentric orbits. Therefore, whilst three sides (the East, North and South) will have been hit many times by artificial space debris, the other three (the West, Space and Earth) will have been impacted almost solely by natural meteoroids from heliocentric orbits, and may be used to determine the flux of such particles in the vicinity of the Earth. The ratios of impacts upon the East, West and Space faces will be useful indicators of the velocity/orbit distribution of meteoroids.