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XMM-Newton Science Analysis System Page: 1
om ateld
November 22, 2004
Abstract
Creates a tracking shifted ateld and applies it to an OM OSW image.
1 Instruments/Modes
Instrument Mode
OM FAST
OM IMAGING
2 Use
pipeline processing yes
interactive analysis yes
3 Description
This task creates a tracking shifted ateld and applies it to an OM OSW Image.
The tracking shifted ateld is created by extracting a window from the OM In Orbit Flateld. This
window is made slightly bigger than the OM OSW Image to accomodate the tracking shifts of pixels
within the In Orbit Flateld. The window is also oversampled so that incremental tracking shifts may be
applied. The resulting oversampled tracking shifted ateld is rebinned and resized before it is divided
into the OM OSW Image and output as a PPS product. The atelded OM OSW Image is also output
for use in subsequent pipeline tasks.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
samplefactor no integer 1 1-10
Spatial sampling factor for tracking shifts
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set yes string none
OM Image lename
thxset yes string none
OM Tracking History Data Auxiliary lename
inorbit atset yes string none
OM In Orbit Flateld lename
ts atset no string none
OM Flateld lename
outset yes string none
OM Flatelded Image 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.
allocError (fatal)
Can't allocate memory for internal array
badFileMode (fatal)
Invalid datamode in set
ZERODRIFT (warning)
OM tracking history is not present for this exposure so no tracking shifts can be applied
corrective action: No tracking correction will be applied
deAllocError (warning)
Failed to release memory for
corrective action:
zeroValuedFlat (warning)
One or more elements of the tracking-shifted at eld (usually at the edge) were unexpectedly
found to be zero. This is likely to be a sampling eect.
corrective action: Resets zero valued pixels to unity and sets a non-zero value in the quality
array
Uniform ateld (warning)
No ateld correction will be applied to the image
corrective action: The OM ateld is currently set to unity (see om atgen task documenta-
tion) so this warning always appears. This may change in the future. The use of a uniform
ateld is `unconventional`, hence the warning (notication) to the user.
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6 Input Files
1. Intermediate OM Image le (taken from omcosflag).
2. Intermediate OM Tracking History Data Auxiliary le (taken from omprep).
3. Intermediate OM In Orbit Flateld le.
7 Output Files
1. OM PPS Flateld le.
2. OM Flatelded Image le (for input in to ommodmap).
8 Algorithm
subroutine omflatfield
read in task parameters
open OM OSW Image file
determine file type from datamode in primary header
read in the science window keywords from the primary header
calculate image binning
extract window data from MODES binary table extension
extract OM OSW Image
open OM Tracking History Data Auxiliary file
determine file type from datamode in primary header
extract tracking history data from OMTHX1 binary table extension
check for poor tracking solution and warn
extract OM In Orbit Flatfield file
calculate maximum drift in x and y
extract localised in orbit flatfield
oversample localised in orbit flatfield
loop over tracking frames to construct oversampled tracking shifted flatfield
loop over discretised tracking steps
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add shifted oversampled localised in orbit flatfield to oversampled tracking shifted flatfield
end loop
end loop
normalise the summed flatfield
resize oversampled tracking shifted flatfield
divide OM OSW Image by tracking shifted flatfield
resize and rebin OM OSW Image with appropriate binning factors
create output OM OSW Image file
create output OM PPS flatfield
end subroutine omflatfield
9 Comments
Since no proper atelds have been made so far, a check is made to see if all the ateld pixels are
unity- if so the input image is not corrected but a warning issued. This saves a considerable amount of
computing time.
10 Future developments
References
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