Results of Impact Analysis on HST Service Mission 3b Solar Arrays

It is important that our knowledge of space debris flux and its potential growth is kept up to date for effective modelling. In one particular critical size regime, knowledge of the sub-mm particle population can only be gained by in-situ detectors or the analysis of materials exposed to space. The solar arrays of Hubble Space Telescope provide a unique opportunity to gain data about these solid particles in the LEO environment and, significantly, evolution of the flux over the decade from 1993. The large area exposed for more than eight years provides high precision particle flux data up to the particle size range of 300 microns. With careful chemical analysis of residues it is also possible to distinguish between debris and meteoroids. Together with damage equations, it has been possible to identify flux distributions as a function of particle diameter. Key aspects of the survey are described, and results of the impact analysis are presented for crater diameters ranging from 3 micrometers to 7 mm. The results are compared with those obtained after the first (1993) postflight analysis, and with the models currently used to simulate the space environment. In conclusion we find good support for the models and fair agreement between PFA1 and PFA2 at medium crater dimensions although, for particles smaller than 5 microns, there is a significant discrepancy.