Space debris or natural? Impacts on NASA's Long Duration Exposure Facility.

The Long Duration Exposure Facility has provided the most complete in-situ study of the near Earth environment to date. This thesis details the spacecraft conception and development culminating in a 69 month excursion into low Earth orbit. The techniques required to analyse the retrieved data are discussed, and indeed, these techniques are applicable to any spacecraft surface or terrestrial experimental hypervelocity impact project. The results have shown that all faces of the LDEF have been impacted by both natural and anthropogenic space debris to some extent. The current models employed to determine the relative proportions of these populations on the LDEF are shown to be inadequate, although the assumptions used are quite sweeping. The modelling presented shows a definite need to use a more anisotropic distribution when discussing the natural environment that incorporates both meteor streams and comet encounters. The problems and concerns surrounding the present anthropogenic space debris population is discussed in detail concluding with the need for better Earth and space borne detection systems and understanding of orbital dynamics of small particles, presently undetectable. An average particle density for interplanetary particles of lgcnr3 is derived from a comparison of data from different experimental surfaces on the Space face of LDEF. The impact direction distributions of both natural and anthropogenic space debris is illustrated, including an enhanced space debris distribution, which accounts for some of the limits in the presently tracked data sets. These data sets are discussed in terms of generation, ownership and orbital distribution.