Correcting Responses for ACIS Contamination
[CIAO 3.4 Science Threads]
OverviewLast Update: 1 Dec 2006 - reviewed for CIAO 3.4: no changes Synopsis: The CIAO response tools are designed to incorporate corrections for ACIS contamination via ARDLIB and a CALDB contamination file. The necessary calibration file was first made available in CALDB 2.26, and was updated in CALDB 3.0.0. Purpose:
To explain the choices that are currently available to account
for the ACIS QE degradation.
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Contents
- Imaging and Grating ARFs
- Instrument and Exposure Maps
- ACIS Contamination File Parameter (ardlib.par)
- Turning Off the Correction
- History
Imaging and Grating ARFs
Create a new ARF
The tools used to create ARFs for imaging data:
- mkarf
- mkwarf
- specextract (calls mkwarf)
- psextract (calls mkarf)
- acisspec (calls mkwarf)
and for grating data:
will now automatically pick up the contamination file from the CALDB. Before beginning the analysis, be sure to follow the steps in the ACIS Contamination File Parameter section.
Correct an existing ARF
All previous contamination corrections are deprecated as of CALDB 2.26. We no longer recommend using either ACISABS or contamarf to correct existing ARFs.
The official recommendation of the "ACIS Modeling and Analysis Team" is that creating a new ARF with the new calibration is the best way to correct for the QE degradation issue.
What if I applied a correction before CALDB 2.26?
If you have already corrected your ARF - either with ACISABS or with contamarf and the draft contamination file (version N0001) - it recommended that you create a new ARF with the most recent calibration.
Instrument and Exposure Maps
Prior to the CALDB 2.26 release, there was no method to account for the continuous degradation in the ACIS QE when creating an instrument map. Now mkinstmap will automatically pick up the file from the CALDB; this also applies to the merge_all script, which calls that tool.
Before running either, be sure to follow the steps in the ACIS Contamination File Parameter section.
Note that if you re-run mkinstmap to pick up the correction, you will also need to create a new exposure map with mkexpmap, as it takes the intrument map as one of the inputs. More information may be found in the "Exposure Maps" section of the Imaging threads.
ACIS Contamination File Parameter (ardlib.par)
Each of the tools which uses the new calibration file (listed in the Create a new ARF section) contains an ardlibparfile parameter with the value"ardlib.par."
The location of the calibration file is specified in the ardlib.par file by a set of 10 parameters (one per CCD):
unix% plist ardlib | grep CONTAM AXAF_ACIS0_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS1_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS2_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS3_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS4_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS5_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS6_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS7_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS8_CONTAM_FILE = CALDB Enter ACIS Contamination File AXAF_ACIS9_CONTAM_FILE = CALDB Enter ACIS Contamination File
If anything other than "CALDB" is returned, issue the following command so that the tool will be able to find the correct file:
unix% foreach d ( 0 1 2 3 4 5 6 7 8 9 ) foreach? pset ardlib AXAF_ACIS${d}_CONTAM_FILE="CALDB" foreach? end
You may also use "punlearn ardlib" to reset all the ardlib parameters to the default values. This will also clear out any other information that has been set, however, such as bad pixel filenames.
Turning Off the Correction
It is possible to "turn off" the contamination correction, e.g. if you would like to compare results with and without it applied. To do so, the ARDLIB qualifier "CONTAM=NO" must be specified in the appropriate parameter, as given in the following table:
Tool | Parameter |
---|---|
mkarf | detsubsys |
mkgarf | detsubsys |
mkwarf | detsubsysmod |
mkinstmap | detsubsys |
There are examples in the help files on how to use the qualifier with each tool. For example, when running mkarf on an ACIS-S3 observation:
unix% pset mkarf detsubsys="ACIS-S3;CONTAM=NO"
History
03 Jan 2005 | updated for CIAO 3.2: new calibration file |
12 Dec 2005 | reviewed for CIAO 3.3: no changes |
16 Feb 2006 | added specextract to list of response tools |
01 Dec 2006 | reviewed for CIAO 3.4: no changes |