Results from a contamination experiment on the ISS

While investigating the feasibility of the accommodation of X-ray instrumentations on the International Space Station (ISS) a major question remained still open, i.e. the unknown extent of degradation of X-ray mirror surfaces and X-ray detector material caused by contamination in the ISS environment. Therefore, a sample expose experiment has been started in 2001 to investigate these effects in detail using the Russian expose facility provided by the Russian space industry company RKK Energia. While Kayser-Threde GmbH was responsible to organize and coordinate the experiment, gold-coated Zerodur and silicon samples have been provided by the Max-Planck-Institute (MPE). In total 5 samples were flown with the expose facility and have been exposed to the ISS environment for a total duration of 756 days. The analyses of 4 of them are presented in this paper. X-ray reflection measurements before and after the experiment at MPE's PANTER X-ray test facility and microscopy inspections revealed a thin structured surface layer which reduced the X-ray reflection of the exposed mirror samples dramatically. In addition, the samples have been analyzed with a scanning electron microscope, an energy dispersive X-ray spectrometer, and electron spectroscopy for chemical analysis. The results of all these measurements revealing the degradation of the X-ray mirrors and polished silicon detector surfaces are presented.