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Proceedings Paper

Distortion of the pixel grid in HST WFC3/UVIS and ACS/WFC CCD detectors and its astrometric correction
Author(s): Vera Kozhurina-Platais; John Mackenty; David Golimovski; Marco Sirianni; David Borncamp; Jay Anderson; Norman Grogin
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Paper Abstract

The geometric distortion of the CCD detectors used in the Hubble Space TelescopeWide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) instruments is characterized by both large and fine-scale distortions. The large-scale distortion, due to the complexity of the HST optical assembly, can be modeled by a high-order polynomial. The majority of fine-distortion is inherent to the CCD detectors themselves, which manifests itself as fine-scale, correlated systematic offsets in the residuals from the best-fit polynomial solution. Such systematic offsets across the CCD chip introduce astrometric errors at the level of about 0.1 pix (up to 1.5 μm within the 15 μm pixels). These fine-scale and low-amplitude distortions apparently arise from the spatial irregularities in the pixel grid. For the WFC3/UVIS CCD chips, there is a clear pattern of periodic skew in the lithographic-mask stencil imprinted onto the detector. Similar irregularities in the pixel grid of ACS/WFC CCD chips are even more pronounced by the narrow (68×2048 pixel) lithographic-mask stencil. To remove these distortions, a 2-D correction in the form of a look-up table has been developed using HST images of very dense stellar fields. The post-correction of fine-scale astrometric errors can be removed down to the level of 0.01 pix (0.15 μm) or better.

Paper Details

Date Published: 29 July 2016
PDF: 7 pages
Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 99046I (29 July 2016); doi: 10.1117/12.2233793
Show Author Affiliations
Vera Kozhurina-Platais, Space Telescope Science Institute (United States)
John Mackenty, Space Telescope Science Institute (United States)
David Golimovski, Space Telescope Science Institute (United States)
Marco Sirianni, European Space Agency (Germany)
Space Telescope Science Institute (United States)
David Borncamp, Space Telescope Science Institute (United States)
Jay Anderson, Space Telescope Science Institute (United States)
Norman Grogin, 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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