Characterizing, controlling, and correcting distortions in the COS FUV detector

David J. Sahnow; George D. Becker; John H. Debes; Justin Ely; Sean A. Lockwood; Derck Massa; Cristina M. Oliveira; Steven V. Penton; Charles Proffitt; Julia Roman-Duval; Hugues Sana; Paule Sonnentrucker; Joanna Taylor

doi:10.1117/12.2188529

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18 September 2015 Characterizing, controlling, and correcting distortions in the COS FUV detector

David J. Sahnow, George D. Becker, John H. Debes, Justin Ely, Sean A. Lockwood, Derck Massa, Cristina M. Oliveira, Steven V. Penton, Charles Proffitt, Julia Roman-Duval, Hugues Sana, Paule Sonnentrucker, Joanna Taylor

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Proceedings Volume 9601, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIX; 96010Q (2015) https://doi.org/10.1117/12.2188529
Event: SPIE Optical Engineering + Applications, 2015, San Diego, California, United States

Abstract

The Far Ultraviolet (FUV) detector on the Cosmic Origins Spectrograph (COS) of the Hubble Space Telescope (HST) is subject to a variety of distortions due to its analog nature. Thermal variations of the detector and electronics stretch and shift the active area. Geometric distortions on a range of spatial scales warp the two-dimensional spectral image. Changes due to detector walk – the dependence of detected position on pulse height – add distortions that change as a function of time. The calcos calibration pipeline includes corrections for each of these effects in the calibrated spectra, but these are imperfect, and they do not help with the target acquisition process, which uses raw detector coordinates. We discuss these distortions and their effect on the data, our attempts to mitigate them, the current pipeline corrections and their success at removing the effects, and possible modifications to improve the data quality in the future.

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David J. Sahnow, George D. Becker, John H. Debes, Justin Ely, Sean A. Lockwood, Derck Massa, Cristina M. Oliveira, Steven V. Penton, Charles Proffitt, Julia Roman-Duval, Hugues Sana, Paule Sonnentrucker, and Joanna Taylor "Characterizing, controlling, and correcting distortions in the COS FUV detector", Proc. SPIE 9601, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIX, 96010Q (18 September 2015); https://doi.org/10.1117/12.2188529

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