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XMM-Newton Science Analysis System Page: 1
omfast at
January 10, 2003
Abstract
Applies in-orbit ateld and modulo-8 spatial xed-pattern noise calibrations to
an OM fast mode event list
1 Instruments/Modes
Instrument Mode
OM Fast
2 Use
pipeline processing yes
interactive analysis yes
3 Description
CCD Single Photon Counting Mode used at X-ray wavelengths is not applicable at optical wavelengths.
At optical wavelengths, each detected event corresponds to a 'fractional' photon count, dependent on
gain variations over the CCD and modulo-8 xed pattern noise (due to the OM centroiding algorithm).
In order to produce photometrically calibrated light-curves the OM FAST mode event-list must be cor-
rected for pixel-to-pixel gain variations and modulo-8 xed pattern noise. This task applies these cor-
rections using the OM in-orbit ateld (as produced by omflatgen) and the OM OSW modulo-8 map
(produced by ommodmap).
This task then calculates a photon-count correction factor for each event in the input event-list, (based on
the event RAWX,RAWY pixel co-ordinates), using the corresponding ateld and modulo-8 image values.
A new column containing this correction factor is added to the eventlist and is used when constructing
photometrically accurate light-curves or images from the OM FAST mode event list. An image is also
computed from the corrected eventlist, and a QUALITY array is attached. This image is suitable for
ommodmap.
Note: Modulo-8 spatial xed-pattern noise correction of the event list is currently not available and may
require a new task. The atelded image produced is currently corrected using the existing Image Mode
task ommodmap.
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4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
set yes string
OM ODF Fast Mode Event List lename
slew atset yes string
In-orbit at eld lename
fastimgset yes string
Output Fast Mode Image lename
osw atset yes string
PPS OSW Flat eld lename
5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
Wrong datamode for Event List (fatal)
The keyword DATAMODE in the input le should be FAST
Real array bounds error (fatal)
Inner problem of the task with real array data indexation or wrong coordinates in the event
list
Int16Array bounds error (fatal)
Inner problem of the task with integer array data indexation or wrong coordinates in the
event list
X/Y exceeds 2047 (warning)
corrective action: Issue a warning if the coordinates in the event list are wrong. Set current
index to the maximal value (2047)
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6 Input Files
1. Intermediate OM fast mode event list (output of omfastshift)
2. OM in-orbit ateld (output of omflatgen)
7 Output Files
1. Flateld corrected intermediate OM fast-mode event list
2. Flatelded fast-mode image suitable for input to ommodmap
3. OM OSW FITS Flateld Data Product
8 Algorithm
subroutine omfastflat
Get task parameters.
Check data types of ODF input files
Check if input is an Inorbit flatfield.
Get a handle on the Inorbit flat field File.
Get a handle on the ODF OM Fast Mode Event List File.
Determine file type from file name in primary header.
Determine if BPE binning is on/off
if (dataMode == "FAST") then
Get a handle on the tracking history data binary table extension.
Get handles and pointers on the event list binary table extension columns.
Get the number of rows in the event list binary table extension.
Get window information from modes extension.
else
Incompatible file.
call fatal("badFileMode","Value for keyword DATAMODE is incompatible")
end if
Open the CCF.
Set the state of the cal.
Get the bad pixel map.
Add factor and bad pixel columns to event list file.
Initialise pointer arrays to zero.
If BPE binning off then need to rebin flatfield.
Calculate factor and bad pixel flag.
factorP(i) = (slewFlat(windowX0P(0) + rawXP(i), windowY0P(0) + rawYP(i)))**(-1.0)
Release the cal memory.
Release handles on data.
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Create flatfielded fast mode image file.
Copy attributes.
Get image handle and pointer.
Get quality array handle and pointer.
Build image and quality array.
do i = 0 , nEvents - 1
fastImgP(corrXP(i), corrYP(i)) = fastImgP(corrXP(i), corrYP(i)) + factorP(i)
if badPixel then quality(corrXP(i), corrYP(i)) = 1
end do
Copy MODES extension
Create OM OSW flat field data product.
Copy Attributes
Add HDU keywords
Add Modes Extension
Free up memory and pointers.
end subroutine omfastflat
9 Comments
10 Future developments
The image must also be corrected for modulo-8 noise. The modulo-8 tile is to be computed from an image
mode OSW that encompasses the FAST mode region, taken during the same exposure. (see ommodmap)
References
xmmsas 20030110 1802-5.4.1