+--------------------------------------------------------+ | STScI Analysis Newsletter (STAN) | Cosmic Origins Spectrograph (COS) | Space Telescope Imaging Spectrograph (STIS) | December 2010 +--------------------------------------------------------+ In this Newsletter we provide information on the changes to the COS pulse height filtering, the effects of gain sag on dispersed light target acquisitions for COS, COS airglow Observations, Reference file updates mailing lists for both COS and STIS, and the delivery of a new FUV bad pixel table for STIS. -------------------------------------------------------------- Change to Pulse Height Filtering to Mitigate Effects of Gain Sag in the COS FUV Detector The gain sag experienced by the COS FUV detector in the regions illuminated by bright airglow lines leads to artifacts (absorption-like features) in the extracted spectra. In order to mitigate this effect we are lowering the minimum threshold used for pulse height screening during calibration. This change to the pulse height screening leads to an increase of ~7% in the average value of the dark count rate and to a 5% overestimation of the calibrated flux. -------------------------------------------------------------- Effect of COS FUV Gain Sag on FUV Dispersed Light Target Acquisitions The gain sag of the COS FUV detector produces also mis-registration of events along the cross-dispersion direction, leading to a "walk" of the spectrum on the detector toward lower values of the cross-dispersion direction. While this walk has no effect in extracted spectra it can potentially alter the accuracy of target acquisitions using FUV dispersed light. -------------------------------------------------------------- COS Airglow Observations A list of non-proprietary COS observations that provide good examples of uncontaminated geo-coronal airglow lines has been posted on the COS web site at http://www.stsci.edu/hst/cos/calibration/airglow.html. -------------------------------------------------------------- COS and STIS Reference File Updates Mailing Lists Every time a new COS or STIS reference file is delivered and the database updated, an email is sent to the mailing lists cos_reffiles_upd@stsci.edu and stis_reffiles_upd@stsci.edu, respectively. For example, to subscribe to the STIS list, send an e-mail to MajorDomo@stsci.edu with the following in the body of the message: subscribe stis_reffiles_upd your_address . -------------------------------------------------------------- New STIS FUV Bad Pixel Table On December 14, 2010, a new FUV bad pixel table for STIS (uce15153o_bpx.fits) was delivered to CDBS. This table adds an optical element column, enabling the correct marking of the repeller wire shadow for all FUV modes. +----------------------------------------------------------+ | Need help? http://www.stsci.edu/hst/cos/help.html +----------------------------------------------------------+ | To subscribe or unsubscribe to the STAN, send a message | to majordomo@stsci.edu 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. +----------------------------------------------------------+
