Computer Science – Performance
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21546320w&link_type=abstract
American Astronomical Society, AAS Meeting #215, #463.20; Bulletin of the American Astronomical Society, Vol. 42, p.497
Computer Science
Performance
Scientific paper
A description is provided of the overall performance of the STIS CCD after HST Servicing Mission #4 and the associated updates to calibration reference files. Most aspects of CCD performance are found to be consistent with extrapolations of the trends seen prior to the failure of STIS in August 2004. However, over the 4.5 years since STIS was last operational, some CCD parameters have changed significantly. The gain value for the CCDGAIN = 4 setting has been re-determined; the new value of 4.015 e-/DN is about 0.5% lower than the value that was adopted for use prior to the August 2004 failure. The Read Noise through Amp D, as determined from unbinned bias images, has increased; it now has a value of 5.6e- for gain=1 and 8.3e- for gain = 4, up from previous values of 5.4 e- and 7.7 e-, respectively. The dark current has increased significantly, as was expected due to the on-orbit radiation environment. The dark current has increased from 0.0058 to 0.0105 e-/pixel/s in the center of the chip - roughly a factor of 2 increase. Additionally, the slope in the dark current along CCD columns has increased by a similar factor, resulting in a dark current near the detector readout amplifier that is about 30% lower than the mean over the whole detector. The charge transfer inefficiency (CTI) has increased by a factor of about 2 as well, although the increased dark current will significantly moderate the actual CTI losses for typical observations. The currently measured CTI values are in excellent agreement with a simple extrapolation of trends seen prior to the 2004 failure.
Bohlin Ralph Charles
Dixon William V.
Goudfrooij Paul
Lennon Daniel
Proffitt Charles
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