ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

260 CHAPTER 20. ADVANCED DATA CALIBRATION
• Standard treatment (EXPOSURE pixels are weighted by CCIM.NPIX) to create the top
left MOSAIC of Figure 20.6:
CIA> raster_scan, raster_pds
• Projection using standard variation of each pixel held in CCIM.RMS to create the top
right MOSAIC of Figure 20.6:
CIA> raster_scan, raster_pds, /weight
• Projection using the flat-field error contained in flat-field library to create the lower left
MOSAIC of Figure 20.6:
CIA> raster_scan, raster_pds, /weight, /wcalg
• Projection using the flat-field error computed from the sky-flat (auto-flag) to create the
lower right MOSAIC of Figure 20.6:
CIA> raster_scan, raster_pds, /weight, /wauto
The resulting MOSAICs are shown below. The top left mosaic demonstrates clearly the
negative effects of an equal weighting of good and badly flat-fielded pixels. Additionally there
is the option wmap, which permits the user to supply his own weight error map.
20.15.3 Coadding images of different astrometry
A very useful function of the projection routines are their ability to combine or coadd images
that have different astrometry. This can be used to combine raster MOSAICs from different
observations of the same object. To take advantage of this functionality we need to go quite
low-level and use the C++ executable projection.
Here is an example on how to combine raster MOSAICs from different observations of the
same object. Note that the same could be done for MOSAICs from different AOTs. For example,
a raster MOSAIC and a beam-switch MOSAIC. Also, more than two MOSAICs can be used.
• Save both raster MOSAICs as FITS files, giving them each a name with an individual
sequence number. We use conv flux to make sure the data are calibrated to the same
units.
CIA> conv_flux, raster_pds1
CIA> conv_flux, raster_pds2
CIA> raster2fits, raster_pds1, name=’input1’
CIA> raster2fits, raster_pds2, name=’input2’
CIA> $ls input*.fits
input1.fits input2.fits