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Hubble Space Telescope
STAN - May 2010

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| STScI Analysis Newsletter (STAN)  
| Cosmic Origins Spectrograph (COS) 
| May 2010
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Visit the "New in the Last 45 Days" section of the COS 
website at http://www.stsci.edu/hst/cos for new
information about COS.

This and previous issues of the STAN can be found at 
http://www.stsci.edu/hst/cos/documents/newsletters.



Contents:

  -Evolution of the COS Spectroscopic Throughputs over Time

  -Changes in the COS NUV Channel Dark Rate

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Evolution of  COS Spectroscopic Throughputs over Time
 
The throughput of a number of COS spectroscopic modes has
been declining more rapidly than had been anticipated at
the time of launch. Here we detail our current
understanding of these changes.

COS NUV MAMA Dark Count Rate
After COS installation during SM4, the COS NUV MAMA dark
count rate had been initially found to be substantially
lower than pre-launch estimates.  However, since that time,
the observed dark rate has been increasing


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