VLA: Filling data from archive format (importvla)

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2.2.3 VLA: Filling data from archive format (importvla)

VLA data in archive format (i.e., as downloaded from the VLA data archive) are read into CASA from disk using the importvla task. The inputs are:

#  importvla :: import VLA archive file(s) to a measurement set:

archivefiles  =         ’’   #  Name of input VLA archive file(s)
vis           =         ’’   #  Name of output visibility file
bandname      =         ’’   #  VLA frequency band name:’’=>obtain all bands in archive files
frequencytol  =   150000.0   #  Frequency shift to define a unique spectral window (Hz)
project       =         ’’   #  Project name:  ’’ => all projects in file
starttime     =         ’’   #  start time to search for data
stoptime      =         ’’   #  end time to search for data
applytsys     =       True   #  apply nominal sensitivity scaling to data & weights
autocorr      =      False   #  import autocorrelations to ms, if set to True
antnamescheme =      ’new’   #   ’old’ or ’new’; ’VA04’ or ’4’ for ant 4
keepblanks    =      False   #  Fill scans with empty source names (e.g. tipping scans)?
evlabands     =      False   #  Use updated eVLA frequencies and bandwidths
async         =      False

The main parameters are archivefiles to specify the input VLA Archive format file names, and vis to specify the output MS name.

ALERT: The scaling of VLA data both before and after the June 2007 Modcomp-turnoff is fully supported, based on the value of applytsys.

The NRAO Archive is located at:

https://archive.nrao.edu

Note that archivefiles takes a string or list of strings, as there are often multiple files for a project in the archive.

For example:

archivefiles = [’AP314_A950519.xp1’,’AP314_A950519.xp2’]
vis = ’NGC7538.ms’

The importvla task allows selection on the frequency band. Suppose that you have 1.3 cm line observations in K-band and you have copied the archive data files AP314_A95019.xp* to your working directory and started casapy. Then,

   default(’importvla’)
   archivefiles = [’AP314_A950519.xp1’,’AP314_A950519.xp2’,’AP314_A950519.xp3’]
   vis = ’ngc7538.ms’
   bandname = ’K’
   frequencytol = 10e6
   importvla()

If the data is located in a different directory on disk, then use the full path name to specify each archive file, e.g.:

archivefiles=[’/home/rohir2/jmcmulli/ALMATST1/Data/N7538/AP314_A950519.xp1’,\
’/home/rohir2/jmcmulli/ALMATST1/Data/N7538/AP314_A950519.xp2’,\
’/home/rohir2/jmcmulli/ALMATST1/Data/N7538/AP314_A950519.xp3’]

Important Note: importvla will import the on-line flags (from the VLA system) along with the data. Shadowed antennas will also be flagged. The flags will be put in the MAIN table and thus available to subsequent tasks and tools. If you wish to revert to unflagged data, use flagmanager (§ 3.2) to save the flags (if you wish), and then use flagdata (§ 3.6) with mode=’manualflag’ and unflag=True to toggle off the flags.

The other parameters are:

   2.2.3.1 Parameter applytsys
   2.2.3.2 Parameter bandname
   2.2.3.3 Parameter frequencytol
   2.2.3.4 Parameter project
   2.2.3.5 Parameters starttime and stoptime
   2.2.3.6 Parameter autocorr
   2.2.3.7 Parameter antnamescheme
   2.2.3.8 Parameter evlabands

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