3.i: Subtracting a source

3.i: Subtracting a source

Logged on 07/10/2009 12:23:38 PM

Restart the MeqBrowser and load the Cattery/Calico/calico-wsrt.py TDL script. The compile time windows should pop up. There are a truck-load of options here, mainly for solving for different Jones matrices. We're working on a very simple simulated Measurement Set though, so we'll only use a couple of the options.

Please note that this document is a not an exhaustive description of this TSL script. A deeper explanation of the options available here can be found in the 3C147 calibration tutorial on the MeqWiki.

The first thing we'll do with this script is use it to subtract the source and then examine what's left.

If you have already selected the Measurement Set then expand the 'What we want to do' and the 'Sky model' menus, and set the options up as shown below.

The first three tick boxes tell us that we're not doing any calibration at this stage. We're going to subtract the source from the visibilities, and finally since no calibration has taken place there will be no need to correct the remaining residual visibilities.

As for the sky model: we know that this Measurement Set contains a central point source as this is all we included in the simulation. For the calibration of real data things obviously aren't this simple, and construction of a sky model is an iterative process that must be done with great care, even with prior knowledge of your targets.

We're just introducing concepts here though, so let's pretend we're omnipotent. Select the 'Use 'MeowLSM' module' option. LSM files come in many flavours but the one to use here is the same one we used to specify the simulation. This is included below, together with a diagram poached from another PURR log which explains the columns.

Obviously there's a tick missing from the screen grab below, and that's the one that activates PURR.

Once this is all set up then hit compile.

Data products

calico-wsrt-compile-time-1.png

calico-wsrt-compile-time-1.png

SSSC1_WSRT-1.lsm

LSM.png

LSM.png