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46.2 Scattered Light

The WF/PC-1 cameras are known to suffer from a time-dependent loss of throughput as well as an increase in scattered light during the time periods following a decontamination procedure. Both effects are believed to be due to the slow growth of contaminants on the field flattening windows in front of the CCDs. The scattered light changes are estimated from internal flatfields, by determining the ratio of the intensity beyond the pyramid vertex to the intensity at chip center. The figure below summarizes the scattered light behavior of all eight chips since early 1991; decontamination episodes are marked with the vertical dotted lines.



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