17 September 2012 The COS FUV channel: on-orbit performance trends and early characterization of a new detector lifetime position
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The Cosmic Origins Spectrograph (COS) was installed into the Hubble Space Telescope in May 2009, and has been collecting ultraviolet spectra since then. The Far Ultraviolet channel of COS uses an efficient optical design and a two-segment, large-format Cross Delay Line microchannel plate detector to obtain spectra at medium and low resolution in the far ultraviolet. While the overall instrument performance has been excellent, several long-term trends in performance have been noted and are being addressed. These include a slow decrease in overall sensitivity, which is independent of the illumination and may be due to a degradation of the photocathode with time. In addition, the detector microchannel plates are showing severe gain sag in the regions where the most photons have fallen. As a result, we are in the process of moving the spectra to a new, nearly pristine, location on the detector. This will be the first of several additional lifetime positions which will allow us to collect high-quality spectra for many years to come. We will discuss the factors that led to our decision on where to move next and our progress in moving there, including details of the enabling and calibration activities which are being performed at the new location, and the anticipated performance. We will also address strategies that will be implemented in order to prolong the life at this and subsequent positions.
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David J. Sahnow, David J. Sahnow, Alessandra Aloisi, Alessandra Aloisi, K. Azalee Bostroem, K. Azalee Bostroem, John Debes, John Debes, Julia Duval, Julia Duval, Justin Ely, Justin Ely, Philip E. Hodge, Philip E. Hodge, Gerard Kriss, Gerard Kriss, Kevin Lindsay, Kevin Lindsay, Derck Massa, Derck Massa, Cristina Oliveira, Cristina Oliveira, Rachel Osten, Rachel Osten, Steven N. Osterman, Steven N. Osterman, Steven V. Penton, Steven V. Penton, Charles Proffitt, Charles Proffitt, Paule Sonnentrucker, Paule Sonnentrucker, Brian York, Brian York, } "The COS FUV channel: on-orbit performance trends and early characterization of a new detector lifetime position", Proc. SPIE 8443, Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, 84434C (17 September 2012); doi: 10.1117/12.926487; https://doi.org/10.1117/12.926487

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