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Hubble Space Telescope
April 2016 STAN

| STScI Analysis Newsletter (STAN) 
| Cosmic Origins Spectrograph (COS)
| April 2016

In this Newsletter we provide updates of interest to 
COS users:



Update to the COS FUV Dark Rates and Impact on ETC Calculations
for Background Limited Observations
The COS/FUV dark currently used by the ETC (4.0x10-6 counts/s/pixel) is based on monitoring data obtained up to the summer of 2015, where the large scatter seen in the dark rate contributed to the large dark rate adopted. The scatter has now decreased substantially, leading to dark rates that are ~ a factor of 2 lower than the value adopted by the ETC. While there is no guarantee that the dark rate will remain at this low level when the Cycle 24 programs execute, PIs considering COS observations of faint, background-limited targets are advised to consider updating their exposure times with this lower background when designing their Phase I observations. +----------------------------------------------------------+ | Need help? | +----------------------------------------------------------+ | To subscribe or unsubscribe to the STAN, send a message | to with a blank subject line and | the following in the body: [un]subscribe cos_news | or [un]subscribe stis_news +----------------------------------------------------------+ | The Space Telescope Science Institute is operated by the | Association of Universities for Research in Astronomy, | Inc., under NASA contract NAS5-26555. +----------------------------------------------------------+