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Hubble Space Telescope
June 2014 STAN

| STScI Analysis Newsletter (STAN) 
| Cosmic Origins Spectrograph (COS)
| Space Telescope Imaging Spectrograph (STIS)
| June 2014

In this Newsletter we provide some updates of interest to 
COS and STIS users who will be drafting and submitting Phase II 
HST programs over the next weeks



Updated Extraction Heights in the COS ETC

The just released ETC 22.2 includes updates to the COS 
ETC extraction heights for the COS FUV spectroscopic modes.   
The COS team has updated the extraction heights in the 
ETC to better reflect those used by the CalCOS pipeline.  
For most users, the difference will be negligible, but we 
detail what modes are affected and what this implies for 
calculations of faint sources. We also remind users that 
S/N calculations in the ETC assume purely Poissonian 
statistics, which over-estimates the uncertainties at 
low count rates.


Gauging the impact of executing science program across 
different COS/FUV lifetime positions lifetime positions
It is expected that the position of COS FUV spectra will be relocated on the detector from the 2nd to the 3rd lifetime position early in 2015. There will some changes in instrument performance as a result of this move, and observers should evaluate if their science goals might be adversely affected should different observations in their program be split across the two lifetime positions. -------------------------------------------------------------- Time resolved observations with STIS/MAMA (TIME-TAG mode) The TIME-TAG mode records the arrival time of each photon on the COS and STIS MAMA detectors. The TIME-TAG mode is the default observation mode for COS but requires an active choice for the STIS users and is often overlooked. We encourage PIs of STIS/MAMA Cycle 22 programs to use the TIME-TAG mode for their observations of sources with count rates less than 20,000 counts/sec as it opens the time-domain window and further increases the legacy value of their observations at little or no extra cost. -------------------------------------------------------------- Preliminary COS/FUV Pixel-to-Pixel flat field reference
file available
COS FUV spectra have multiple sources of fixed-patter noise, many of which are corrected in standard pipeline processing. Investigations are on-going to correct residual pixel-to-pixel variations, and while they are in-progress the COS team is making the preliminary calibration reference files available to all users, even if only high S/N observations will benefit from this calibration. +----------------------------------------------------------+ | 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. +----------------------------------------------------------+