Knowledgebase: Offline Data Reduction and/or CASA
Why are the fluxes in my CASA 5.1 simulated mosaic image incorrect, and how can I fix it?
Posted by Brian Mason, Last modified by Sarah Wood on 11 April 2018 05:33 PM
We have recently identified a bug in the CASA 5.1 releases which seriously affects mosaic imaging of simulated data. The simulated visibilities themselves are not adversely affected, nor is imaging a single field of a simulated mosaic in non-mosaic mode (gridder='standard' in |
This issue will be fixed in the upcoming CASA 5.3 release. In the meantime, two workarounds are as follows:
In order to use a 5.1 CASA version (the second workaround) the user should type
prior to starting CASA (if using BASH). If the shell is a CSH variant, the user should instead type
The value of VI1 does not matter, it only matters that the variable is defined at the time CASA starts up. To undefine VI1 the user can type
in either BASH or CSH. If you're not sure what shell you're using you can find out by typing "echo $0".
Detailed Information: the mosaic imaging bug is only triggered in the CASA 5.1.* releases, when the recently added internal VI2 framework is used, and when the cadence of updates in the pointing table identically matches the integration time of the data. For real ALMA data the cadence of pointing information (48 ms) is considerably higher than the shortest available integration times (~1 second), so the bug is not triggered.