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NICMOS STScI Analysis Newsletter 37

| STScI Analysis Newsletter
| 16 May 2007
Visit the NICMOS web site
"New in the Last 45 Days" for all new information about NICMOS.


-NICMOS Data Handbook Version 7.0 Release
-A new Instrument Science Report regarding the new SAAclean
	PyRAF Task Instrument Science Report
-Extended NICMOS Calibration Plans


NICMOS Data Handbook Version 7.0 Release

The latest version of the NICMOS Data Handbook has been released  
forgeneral distribution.  It can be found on the NICMOS web site at

The changes include updates to the ESA NICMOSlook and aXe  
development and their use.  Significant updates have been made to  
the SAAclean and StayPuft explanations and implementations.  The  
new Count-Rate Non-linearity section introduces a new STSDAS task  
rnlincor, which we expect to be delivered in the next STSDAS  
release.  Minor updates have been made to the NICMOS Dark Current  
and Bias, Dark Current, Amplifier Glow, Bias, Shading, and  
"Pedestal", Random Uncertainties (i.e., noise) in the Temperature- 
Dependent Darks, and Systematic Uncertainties in the Temperature- 
Dependent Darks.


NICMOS ISR 2007-001:  Removing Post-SAA Persistence in NICMOS Data

A general concern with NICMOS images is the issue of persistence,  
or residual charge from bright sources and cosmic rays that remains  
trapped in pixels and is gradually released during subsequent  
exposures. This is particularly noticeable after HST transits of  
the South Atlantic Anomaly (SAA), where the cosmic ray rate is so  
high that their residual flux contributes a significant noise  
component to many subsequent exposures. We describe the SAAclean  
task which can be run on post-SAA NICMOS images to identify the  
amount of charge in each pixel that can be attributed to persistent  
flux from SAA cosmic rays, and apply a correction based on an SAA  
persistence model to remove this flux from the data. This task has  
so far been tested on a variety of NICMOS data, and this represents  
the most recent update of this task in the PyRAF/STSDAS environment  
to the HST observer community. The NICMOS team would welcome  
feedback from the community on the use of this task or any  
suggestions for !
inclusion in future releases.


Extended NICMOS Calibration Plans

The NICMOS Cycle 15 calibration plans are being extended up to the  
upcoming servicing mission in 2008 (SM4). It is planned that  
several monitoring calibration proposals from the Baseline Cycle 15  
calibration plans, which are currently underway, will simply be  
extended as-is. Such programs are the dark stability, the flat- 
field stability, the photometric stability, and the focus stability  
programs. The Cycle 15 non-linearity program will also be extended  
in order to cover a longer time baseline. Additional observations  
of infrared spectrophotometric standards will be undertaken using  
both imaging and grism observations. This will both improve the  
accuracy of the infrared flux measurements of these objects as well  
as detect any light variability in these objects. We are also  
planning for the addition of several new calibration programs: A  
grism calibration program will aim at determining the dispersion  
solution of the NICMOS grism modes in different positions on the  
detectors. M!
oreover, we are aiming at using available pure parallels, periods  
when another instrument is the prime HST instrument, to obtain an  
extensive set of MULTIACCUM dark observations using all the modes  
used during past GO proposals. Parallel observations will also be  
used to obtain additional flat-field observations, thereby   
ignificantly increasing the pool of available flat-fields for  
NICMOS over a larger period of time. These plans are currently  
being finalized; we would welcome input from the community on any  
specific aspects of NICMOS operation that could be  addressed in  
this extended calibration plan.


For more detailed information and updates, please consult the
NICMOS webpages:

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