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Session 18 - STIS.
Display session, Wednesday, January 07
Exhibit Hall,
The STIS on-board target acquisition and acquisition/peakup routines have been designed to accurately locate a target in the center of a slit or behind a bar/wedge. All acquisitions use the CCD camera to initially obtain a direct image of the target field. The on-board flight software then processes the image to locate the position of the target, and centers the target in the reference aperture. Analysis to date of STIS acquisitions (ACQ) for point sources have shown that the ACQ is positioning the target within 0.025 arcseconds of the center of the aperture; diffuse source acquisitions are slightly less accurate, depending on the size of the source. For observations into the smaller slits, the ACQ is followed by a peakup acquisition (ACQ/PEAK). Results show that the ACQ/PEAKs are working very accurately when performed after a successful ACQ. Here we present the mechanics, the observational requirements, and the accuracies of the on-board STIS target acquisitions. We also present those updates to the flight software which we have implemented to improve the quality of target acquisitions.
