Generating a UVTable from an MSTable for input to frank

As noted in the Quickstart, frank takes as input a UVTable with columns of u [lambda]     v [lambda]      Re(V) [Jy]     Im(V) [Jy]     Weight [Jy^-2].

A UVTable is just the ASCII form of an MSTable (measurement set), which is the default data format internal to CASA. In many cases we must thus convert the MSTable internally in CASA to a UVTable. To do this, the uvplot package is a good option. You can install it inside CASA with casa-pip install uvplot (see the uvplot repo). Then use it to extract a UVTable by following these simple steps.

As noted there, we recommend performing a CASA split command with keepflags=False before exporting the UVTable, as this ensures that only valid visibilities are exported.

It’s worth performing a fit for a given dataset with a UVTable extracted from an MSTable in which no or minimal time averaging and channel averaging have been applied. In some cases the increased density of (u, v) points can improve the data’s SNR at long baselines enough that frank fits the visibilities in this region more closely.