Data flagging with viewer

Your data will inevitably have some bad data. Perhaps a receiver on a given antenna is acting up, or perhaps the pointing on a given antenna is poor, and these problematic data will translate to (hopefully) obviously aberrant data in your measurement set. It's a good idea to inspect your data carefully before calibration and imaging, and CASA offers several tools to flag bad data interactively.

This tutorial illustrates how to use viewer to flag poor data. It will use the dataset AU079 from the VLA archive; this dataset is also used in the Imaging Flanking Fields tutorial. As described in that tutorial, the data may be loaded into CASA useing the importvla command.

# from loaddata.py
from glob import glob

# Define the list of files for reading. Use glob to perform wildcard matching with VLA archive filenames.
fileList = glob('AU079_*.xp?')

importvla(archivefiles=fileList,vis='au079.ms')
listobs('au079.ms')
vishead('au079.ms')