MOPEX User's Guide - IRSA

MOPEX User’s Guide
The tile specification files corresponding to the other optional mosaics requested in the
Global Parameters section of the namelist (e.g. the outlier mosaic) are created by the next
module, Mosaic Combine, but are written to the output mosaic directories (e.g. Outliermosaic/).
DISCUSSION
The co-addition can be performed on Tiles (see §8.1), to address computer memory
considerations. The Mosaic CoAdder module performs the co-addition on the individual tiles,
and the Mosaic Combine module then combines the tiles into a single mosaic. Even if only a
single tile is used, Mosaic Combine still needs to be run, in order to produce the expected
products.
There are several weighting schemes available. The interpolated images are normally
combined using straight averaging. Exposure time weighting is also available. The co-added
uncertainty image is computed regardless of whether interpolated uncertainty images are used
for weighting, as long as the uncertainty images are given as an input to the program.
The coverage mosaic is always the number of good pixels in the final stack. The total
exposure time for a pixel (when time-weighting) is not available as a mosaic, but can be found
per tile in the output_dir/Coadd-mosaic directory. (If there's only one tile, it is like the final
mosaic.)
Straight Average: (default) If none of the weighting alternatives are selected, then the coadded
pixel value O is given by the following expression:
O =
∑
j
c j I j
Mosaicking (mosaic.pl) 87
Mosaic Modules
C
Equation 5.5
Here Ij is the value of the interpolated pixel in image j, and cj is the pixel value of the
corresponding coverage map. Co-added uncertainty U = W-1 is given by the following
expression: