Logged on 06/29/2009 12:21:28 PM
For MeqTrees to perform a simulation it needs an empty Measurement Set. This consists of antenna information, a central pointing direction, frequency channel information and the empty UVW points. MeqTrees will generate (corrupted) visibilities based on your sky model and fill up one or more of the data columns of the MS.
An empty MS can be generated in several ways. My old method of choice was to use the AIPS++ simulator to observe a blank sky, but the MakeMS tool is much faster.
The only catch is that MakeMS needs an ANTENNA table from an existing MS. For this first example simulation I took the antenna table from the MS of a genuine Westerbork observation. This is attached below. I've got lots of different ANTENNA tables lying around so get in touch if you need one.
MakeMS also needs a config file which describes the observation (pointing direction, duration, integration, channel info etc.). This is also provided below.
As you can see from the config file we're simulating a 12 hour observation with 3 minutes of integration per visibility. This integration time is probably a bit high but we can keep the file sizes manageable this way and still make a point.
This is a 64 channel L-band observation, looking at RA = 0 and Dec = 60.
A quirk exhibited by MakeMS is that by default it labels all the stations 'LOFAR' and gives them a diameter of 150 m. This won't really affect things as dish sizes are generally wired into the E-Jones modules and the station names are cosmetic.
I've hacked the relevant table using Pyrap Tables (you can also use glish) for this example however, in case you want to write your own super E-Jones module which pulls the relevant info out of the table.
But I'm getting ahead of myself here...