Molecular Contamination Analysis on SUZAKU X-ray Imaging Spectrometer

摘要

Suzaku is the fifth Japanese X-ray astronomy satellite. The X-ray telescopes consist of four X-ray Imaging Spectrometer (XIS) detectors, a single X-Ray Spectrometer (XRS) detector and a single Hard X-Ray Detector (HXD). The XIS has an X-ray CCD camera, which covers an energy range of 0.2-12 keV. Suzaku was launched on a Japanese M-V launch vehicle on July 10, 2005. The X-ray CCD effective area below 2 keV has been decreasing with time after the launch. The degradation was characterized by X-ray absorption of carbon-rich molecular contaminants with accumulation mass of 100-140 ug cm"2 on the XIS Optical Blocking Filters (OBF) in 2010. The contaminant thickness was maximal at the center of an OBF, and decreased toward the edge of the OBF. The numerical analyses suggested that molecular contaminants, outgassed from the spacecraft's materials, would accumulate in sufficient quantity to explain the phenomena well.