Interaction between electromagnetic radiations and West Ford needle clusters: Models and application

Radar observations of small space debris made with the Goldstone radar facility has shown that a population of small particles do exist at an altitude larger than 2000 km. This population has been identified with clusters of copper needles created upon the deployment of the West Ford needles project, by MIDAS satellites in 1961 and 1963. This set of particles is either not taken into account in the debris models or only add to other populations. However, it could affect, for instance, the space borne astronomical experiments. In order to assess this threat it is necessary to model their physical and geometric characteristics. A preliminary modelling using spheres suggests that some improvement is needed. We propose a better approach with long conductive circular cylinders as a model for the clusters. The interaction of solar light with these particles allows us to estimate the spurious flux scattered inside space borne instruments. We conclude that for a given spatial configuration light flashes can affect seriously the operating mode of high-sensitivity instruments.