11258(  1) - 03/30/07 11:12  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11258

Version: 1    Check-in Time: 30-Mar-2007 15:12:15       STScI Edit Number: 0

Title
Removing the herring-bone pattern-noise from *all* STIS Side-2 CCD data: a factor ~3
enhancement in sensitivity
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Type             Cycle     Parallel Pointing Tolerance
AR               16        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Rolf A. Jansen                Arizona State University
   CoI: Mr. Nimish P. Hathi               Arizona State University                      N
   CoI: Dr. Rogier A. Windhorst           Arizona State University                      N
   CoI: Dr. Paul Goudfrooij               Space Telescope Science Institute             N

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Abstract

When STIS resumed operations in July 2001 using the redundant "Side-2" electronics,
the read-noise of the CCD detector appeared to have increased by ~1 e- due to a
superimposed and highly variable "herring-bone" pattern-noise. For the majority of
programs aiming to detect signals near the STIS design limits, the impact of this
noise is far more serious than implied by a mere 1 e- increase in the amplitude of
the read-noise, as it is of a systematic nature. We have perfected a method to
cleanly remove this pattern-noise from raw STIS CCD frames. It is robust, but too
costly in terms of CPU time and overhead to incorporate into the regular HST/STIS
OTFR-pipeline. Systematic application therefore demands a one-time dedicated off-
line effort beyond the scope of the work outlined in the STIS close-out calibration
plan. As a service to the STIS user community, we propose to fully remove this
excess noise from *all* raw, un-binned, "Side-2" STIS/CCD frames, and so
significantly augment the potential of the STIS data base for future NUV--NIR
archival research. The noise characteristics and effective sensitivity of the
resulting cleaned data, to be delivered back to the HST Archive, will closely match
those of CCD data taken during operations with the primary electronics ---
representing a gain of a factor ~3 in sensitivity at faint flux levels, at low
surface-brightness levels, as well as at small spatial scales. All software will be
documented and made available to the community. This archival calibration legacy
program requests a modest, but necessary, investment of resources to assure a long-
lasting STIS legacy. Science programs that will benefit include: (1) *all* STIS/CCD
spectroscopy of faint point- or extended sources; (2) *all* STIS/CCD imaging of
faint point sources or low surface-brightness extended sources; and (3) *all*
STIS/CCD programs that combine data obtained with both primary and redundant
electronics.
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