1. TNO Science and Technology, P.O. Box 6235, 5600 HE Eindhoven, The Netherlands, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands, Dutch Space B.V., Mendelweg 30, 2333 CS Leiden, The Netherlands, and Materials Space Evaluation and Radiation Effects Section, ESA- ESTEC, P.O. BOX 299, Keplerlaan 1, NL 2200 AG Noordwijk, The Netherlands