Applying EVLA on-line flags

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Currently, the EVLA does not apply on-line flags. This includes time when the telescope was not on source and the time needed for the subreflector to come to its final position.

Two tools can be used to apply these flags after the observation:

1) using the script flagant.py, which applies information stored in the ASDM raw data file to your measurement set.

2) importing data with the newly developed importevla task


Note that the importevla task is not available in the official release (yet) and has not been extensively tested. Thus we will concentrate here on how to use the flagant.py script. The following steps are needed:

1) Download the flagant.py script. It is available here File:Flagant.py

2) Download your data from the archive in the ASDM format

3) Convert your ASDM into an MS file format but do not delete the ASDM just yet. The task to do so is importasdm. Typical inputs are:

#  importasdm :: Convert an ALMA Science Data Model observation into a CASA visibility file
asdm                = 'leo2pt.asdm'     #  Name of input asdm directory (on disk)
vis                 = 'leotest.ms'      #  Root name of the ms to be created. Note the .ms is NOT added
singledish          =      False        #  Set true to output single-dish data format
corr_mode           =      'all'        #  specifies the correlation mode to be considered on input. A quoted string containing a sequence of ao, co, ac,or
                                        #   all separated by whitespaces is expected
srt                 =      'all'        #  specifies the spectral resolution type to be considered on input. A quoted string containing a sequence of fr,
                                        #   ca, bw, or all separated by whitespaces is expected
time_sampling       =      'all'        #  specifies the time sampling (INTEGRATION and/or SUBINTEGRATION)  to be considered on input. A quoted string
                                        #   containing a sequence of i, si, or all separated by whitespaces is expected
ocorr_mode          =       'co'        #  output data for correlation mode AUTO_ONLY (ao) or CROSS_ONLY (co) or CROSS_AND_AUTO (ca)
compression         =      False        #  Flag for turning on data compression
asis                =         ''        #  Creates verbatim copies of the ASDMtables in the ouput measurement set.  Value given must be a string of table
                                        #   names separated by spaces; A * wildcard is allowed.
wvr_corrected_data  =       'no'        #   Specifies which values are considerd in the SDM binary data to fill the DATA column in the MAIN table of the
                                        #   MS. Expected values for this option are: no, for uncorrected data (default), yes, for the corrected data, and
                                        #   both, for for corrected and uncorrected data. Note if both is selected two measurement sets are created, one
                                        #   with uncorrected data and the other with corrected data.
verbose             =      False        #  Output lots of information while the filler is working
overwrite           =      False        #  Over write an existing MS
showversion         =      False        #  Report the version of asdm2MS being used
async               =      False        #  If true the taskname must be started using importasdm(...)

4) run the flagant.py script using both, the MS and the ASDM files.

execfile('flagant.py')
flagant=flagxml('leo2pt.asdm','leotest.ms')

5) enjoy your newly flagged data!! You can feel free to delete the ASDM file now, if you like.


--Jott 00:44, 25 March 2010 (UTC)