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XMM-Newton Science Analysis System Page: 1
ommosaic
January 10, 2003
Abstract
Mosaics OM images (Derived from emosaic written by Richard West- SSC Leices-
ter)
1 Instruments/Modes
Instrument Mode
OM IMAGING
2 Use
pipeline processing yes
interactive analysis yes
3 Description
This task accepts an arbitrary number of PPS OSW rotated image les and produces a mosaiced image.
The task description is basically the same as that for emosaic, from which it has been derived, with the
important dierence that it does not need an exposure image. The mosaiced image is not intended to
be used for photometry or astrometry. The task can process a mixture of both low and high-resolution
images- in such case a warning is issued and the pixel-size of the mosiaced image is that of the low-
resolution images. The program is mainly intended to combine the ve separate images (The Rudi-ve)
that make up a full-frame image for a given lter. It can also be used to mosaic images from dierent
lters, in which case a warning will be issued.
The output pixel size (in degrees) and world-coordinate system (WCS) reference coordinate for the output
image are set to those of the rst image with the largest pixel size. The task can read 16-bit, 32-bit or
64-bit input images, the output image is (currently) always of 32-bit real type.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
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imagesets yes string none
List of input image datasets to be mosaiced
mosaicedset yes string none
Name of output mosaiced image dataset
exposure no real 1000
Exposure time (secs) for mosaiced image
exposuremap no boolean F
is the exposure map required to be saved in the output le
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.
badDims (fatal)
Only 2-D images are supported
badType (fatal)
Image is of unsupported data type
You are combining identical images! (warning)
corrective action: le name
You are combining images from dierent lters! (warning)
(warning)
corrective action:
corrective action: List of lters foundYou are combining images from the same exposure!List
of overlapping les found
6 Input Files
1. List of image les (image in primary header)
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7 Output Files
1. Mosaiced image
8 Algorithm
Read parameters
Read each input image
If the input images contain a mixture of low and high resolution windows,
convert the high-resolution windows to low resolution ones.
Check that the filters for each file are identical- if not issue a warning.
Set output projection (reference coordinate, pixel size) from the
first input image
Project corners of each input image into output frame to find the
bounds of the output image
Calculate size of output image in pixels from bounds and pixel size
Create output image
Loop over input images
Normalize each one by its exposure time.
Loop over pixels in output image
Project coordinate of output pixel into frame of input image
Sample input pixel, add sample to output image
Increment each weighting pixel by one if the corresponding input image
pixel is to be coadded to the corresponding mosaiced image pixel.
Increment the corresponding exposure image pixel by the exposure time
for that image.
End loop
End loop
Divide the mosaiced image by the exposure image.
Multiply the image by the exposure time (default 1000 secs).
Write output image
If required, write output exposure map image.
9 Comments
 none
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9.1 Future developments
 none
References
xmmsas 20030110 1802-5.4.1