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Proceedings Paper

Correcting for errors due to walk and geometric distortion in the COS FUV detector
Author(s): David J. Sahnow; Steven Penton; Thomas Ake; Gisella DeRosa; Justin Ely; Sean Lockwood; Cristina Oliveira; Rachel Plesha; Charles Proffitt; Julia Roman-Duval; Paule Sonnentrucker; Joanna Taylor; James White
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Paper Abstract

The Far Ultraviolet detector of the Cosmic Origin Spectrograph (COS) on the Hubble Space Telescope (HST) is subject to distortions on a range of spatial scales in its two-dimensional format due to its analog nature. Incomplete correction of these effects can lead to errors in wavelength scales and flux measurements in the calibrated spectra. Two of the largest sources of error are geometric distortion and walk. Although they are accounted for separately in the CalCOS calibration pipeline, they are highly coupled and can be considered as manifestations of the same effect.

The current calibration pipeline does not apply any walk correction in the dispersion direction even though walk-induced errors can be more than a resolution element in some cases. The current geometric correction, which was derived without considering walk effects, is also known to have inaccuracies. As part of our efforts to improve the wavelength calibration of COS, we have revisited the existing walk and geometric correction using both prelaunch and on-orbit data.

Paper Details

Date Published: 18 July 2016
PDF: 6 pages
Proc. SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray, 99052T (18 July 2016); doi: 10.1117/12.2233091
Show Author Affiliations
David J. Sahnow, Space Telescope Science Institute (United States)
Steven Penton, Space Telescope Science Institute (United States)
Thomas Ake, Space Telescope Science Institute (United States)
Gisella DeRosa, Space Telescope Science Institute (United States)
Justin Ely, Space Telescope Science Institute (United States)
Sean Lockwood, Space Telescope Science Institute (United States)
Cristina Oliveira, Space Telescope Science Institute (United States)
Rachel Plesha, Space Telescope Science Institute (United States)
Charles Proffitt, Space Telescope Science Institute (United States)
Julia Roman-Duval, Space Telescope Science Institute (United States)
Paule Sonnentrucker, Space Telescope Science Institute (United States)
European Space Agency (United States)
Joanna Taylor, Space Telescope Science Institute (United States)
James White, Space Telescope Science Institute (United States)


Published in SPIE Proceedings Vol. 9905:
Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray
Jan-Willem A. den Herder; Tadayuki Takahashi; Marshall Bautz, Editor(s)

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