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Hubble Space Telescope
June 2012 STAN

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| STScI Analysis Newsletter (STAN) 
| Cosmic Origins Spectrograph (COS)
| Space Telescope Imaging Spectrograph (STIS) 
| June 2012
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In this Newsletter we provide some updates of interest to 
COS and STIS users who will be drafting and submitting Phase 2 
HST programs over the next several weeks.  

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Using multiple FP-POS positions at new COS Lifetime Location. 

In Cycle 20, the use of multiple FP-POS positions for any given 
Cenwave is recommended for all COS spectroscopic observations, 
especially in the FUV.


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New ETC Release (20.2): New dark current rates, throughput 
and sensitivity curves

In preparation for Cycle 20 Phase II proposal submission, 
a new version of the ETC (20.2) has been released. As part of this 
new ETC release, the COS/STIS instrument team has updated some 
of the included instrument data. These updates include revised 
throughput and sensitivity values, as well as dark rates for each 
detector, based on calibration measurements made during the 
previous year. 


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Summary of the new COS Lifetime Position Characteristics

To overcome the effects of gain sag, the position of spectra on 
the COS FUV detector will be moved to a new lifetime position in 
late July 2012. This new lifetime position is displaced in the 
cross-dispersion direction by 3.5", corresponding to ~41 
pixels. This change, affecting both COS FUV science and COS 
FUV target acquisitions, will be transparent to users 
preparing their Phase II with APT. No changes will be made to 
the location of the COS NUV spectra.

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A Reminder about CCD Charge Transfer Efficiency Changes

The STIS CCD is a 1024 X 1024 pixel, thinned, backside illuminated
SITe CCD, with sensitivity from below 2000  up to about 11000 . 
In a space environment, CCD detectors accumulate radiation
damage, which over time leads to increasing dark current, more
hot pixels, and reduced charge transfer efficiency. After fifteen 
years on orbit, the effects of such radiation damage on the STIS 
CCD have become substantial. 


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