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High-throughput vacuum ultraviolet stimulus for flat fielding and spectral calibration of the HST advanced camera for surveys

The Advanced Camera for Surveys (ACS) will fly on the Hubble Space Telescope (HST) Servicing Mission 3b in late-2001 and includes a Solar Blind Channel (SBC) comprising correcting/magnifying relay optics, a far ultraviolet (FUV) filter selection, and a 1K X 1K multi-anode microchannel array (MAMA) detector with cesium iodide photocathode. In order to characterize SBC's flat field response over its full spectral range and to radiometrically calibrate ACS at two FUV lines through as many SBC filters as possible, a sophisticated and automated STimulus for Ultraviolet Flat Fields (STUFF) was developed whose application extends to other vacuum ultraviolet optical instrumentation having similar characterization requirements. Challenges in STUFF's development and resulting design features are presented along with results from in vacuo characterizations carried out before and during thermal vacuum testing of ACS.