WFPC2 Filters after 16 Years on Orbit

In a joint investigation by GSFC and STScI, the Selectable Optical Filter Assembly (SOFA) of WFPC2 was extracted and the filter wheels removed and examined for any on-orbit changes. The filters were inspected, photographed and scanned with a spectrophotometer at GSFC. The data have been analyzed at STScI with a view towards understanding how prolonged exposure to the HST space environment affected the filters and what the resultant impacts are to WFPC2 calibrations. We summarize our results from these post-SM4 laboratory studies, including a comparison of preto post-mission filter throughput measurements, evaluations of the UV filter red leaks, and assessment of the condition of the filter coatings.