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Proceedings Paper

Gain sag in the FUV detector of the Cosmic Origins Spectrograph
Author(s): David J. Sahnow; Cristina Oliveira; Alessandra Aloisi; Philip E. Hodge; Derck Massa; Rachel Osten; Charles Proffitt; Azalee Bostroem; Jason B. McPhate; Stéphane Béland; Steven N. Osterman; Steven V. Penton
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Paper Abstract

The Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) uses a large-format cross delay line (XDL) detector in its Far Ultraviolet (FUV) channel. While obtaining spectra, light falls non-uniformly on the detector due to the optical design and the spectral properties of the object being observed; in particular, bright emission lines from geocoronal Lyman-alpha can fall on the detector in more than 20 locations. As a result, some areas of the detector have received a much greater exposure than others. This non-uniform illumination has led to a time- and position-dependent change in the gain of the microchannel plates, which causes variations in the overall detector performance. We will discuss the effects of this gain sag on the science data, and discuss mitigation strategies which are being implemented in order to maximize the detector lifetime.

Paper Details

Date Published: 13 September 2011
PDF: 11 pages
Proc. SPIE 8145, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVII, 81450Q (13 September 2011); doi: 10.1117/12.893989
Show Author Affiliations
David J. Sahnow, The Johns Hopkins Univ. (United States)
Cristina Oliveira, Space Telescope Science Institute (United States)
Alessandra Aloisi, Space Telescope Science Institute (United States)
Philip E. Hodge, Space Telescope Science Institute (United States)
Derck Massa, Space Telescope Science Institute (United States)
Rachel Osten, Space Telescope Science Institute (United States)
Charles Proffitt, Space Telescope Science Institute (United States)
Azalee Bostroem, Space Telescope Science Institute (United States)
Jason B. McPhate, Univ. of California, Berkeley (United States)
Stéphane Béland, Univ. of Colorado at Boulder (United States)
Steven N. Osterman, Univ. of Colorado at Boulder (United States)
Steven V. Penton, Univ. of Colorado at Boulder (United States)


Published in SPIE Proceedings Vol. 8145:
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVII
Oswald H. Siegmund, Editor(s)

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