
Proceedings Paper
HST/WFC3: understanding and mitigating radiation damage effects in the CCD detectorsFormat | Member Price | Non-Member Price |
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Paper Abstract
At the heart of the Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) UVIS channel is a 4096x4096 pixel e2v
CCD array. While these detectors continue to perform extremely well after more than 7 years in low-earth orbit, the
cumulative effects of radiation damage are becoming increasingly evident. The result is a continual increase of the hotpixel
population and the progressive loss in charge-transfer efficiency (CTE) over time. The decline in CTE has two
effects: (1) it reduces the detected source flux as the defects trap charge during readout and (2) it systematically shifts
source centroids as the trapped charge is later released. The flux losses can be significant, particularly for faint sources in
low background images. In this report, we summarize the radiation damage effects seen in WFC3/UVIS and the
evolution of the CTE losses as a function of time, source brightness, and image-background level. In addition, we
discuss the available mitigation options, including target placement within the field of view, empirical stellar
photometric corrections, post-flash mode and an empirical pixel-based CTE correction. The application of a post-flash
has been remarkably effective in WFC3 at reducing CTE losses in low-background images for a relatively small noise
penalty. Currently, all WFC3 observers are encouraged to consider post-flash for images with low backgrounds. Finally,
a pixel-based CTE correction is available for use after the images have been acquired. Similar to the software in use in
the HST Advanced Camera for Surveys (ACS) pipeline, the algorithm employs an observationally-defined model of how
much charge is captured and released in order to reconstruct the image. As of Feb 2016, the pixel-based CTE correction
is part of the automated WFC3 calibration pipeline. Observers with pre-existing data may request their images from
MAST (Mikulski Archive for Space Telescopes) to obtain the improved products.
Paper Details
Date Published: 29 July 2016
PDF: 11 pages
Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 99045D (29 July 2016); doi: 10.1117/12.2233407
Published in SPIE Proceedings Vol. 9904:
Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave
Howard A. MacEwen; Giovanni G. Fazio; Makenzie Lystrup; Natalie Batalha; Nicholas Siegler; Edward C. Tong, Editor(s)
PDF: 11 pages
Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 99045D (29 July 2016); doi: 10.1117/12.2233407
Show Author Affiliations
S. M. Baggett, Space Telescope Science Institute (United States)
J. Anderson, Space Telescope Science Institute (United States)
M. Sosey, Space Telescope Science Institute (United States)
C. Gosmeyer, Space Telescope Science Institute (United States)
J. Anderson, Space Telescope Science Institute (United States)
M. Sosey, Space Telescope Science Institute (United States)
C. Gosmeyer, Space Telescope Science Institute (United States)
M. Bourque, Space Telescope Science Institute (United States)
V. Bajaj, Space Telescope Science Institute (United States)
H. Khandrika, Space Telescope Science Institute (United States)
C. Martlin, Space Telescope Science Institute (United States)
V. Bajaj, Space Telescope Science Institute (United States)
H. Khandrika, Space Telescope Science Institute (United States)
C. Martlin, Space Telescope Science Institute (United States)
Published in SPIE Proceedings Vol. 9904:
Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave
Howard A. MacEwen; Giovanni G. Fazio; Makenzie Lystrup; Natalie Batalha; Nicholas Siegler; Edward C. Tong, Editor(s)
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