widebandpbcor.py

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#
# This file was generated using xslt from its XML file
#
# Copyright 2009, Associated Universities Inc., Washington DC
#
import sys
import os
from  casac import *
import string
from taskinit import casalog
#from taskmanager import tm
import task_widebandpbcor
def widebandpbcor(vis='', imagename='', nterms=2, threshold='', action='pbcor', reffreq='', pbmin=0.2, field='', spwlist=[], chanlist=[], weightlist=[]):

        """Wideband PB-correction on the output of the MS-MFS algorithm

   Wide-band Primary-beam correction

    (1) Compute a set of Primary Beams at the specified frequencies
    (2) Calculate Taylor-coefficient images that represent the PB spectrum
    (3) Perform a polynomial division to PB-correct the output Taylor-coefficient
          images from the MS-MFS algorithm ( clean(nterms>1) )
    (4) Recompute spectral index (and curvature) using the corrected Taylor-coefficient images.

   [ Optionally, skip PB-correction, and only recalculate spectral index
      with a different threshold ]

   This is a temporary task, meant for use until projection-based gridding algorithms
   are available via the 'clean' task.

   An output directory named imagename.pbcor.workdirectory is created, and filled with
   an image-cube of the evaluated primary beams at all specified frequencies,
   Taylor-coefficients, and a 'spectral index' due to the primary beam.  
   Note that for the actual pb-correction, only the Taylor-coefficient images are used.
 
   Task parameters :

   vis -- Name of input visibility file
           example : vis = 'ngc5921.ms'
              Only one MS can be specified here, and it must contain at-least one
               timestep of data at all frequencies required to calculate the PB spectrum. 
              ( In case of multiple MSs with different spectral windows, for now, 
                please split/concat a small fraction of the data to form such an MS )

   imagename -- Pre-name of input and output images. Same as in the clean task.           
           example : imagename = 'run1'
              Restored-images ( run1.image.tt0,etc) and residual images ( run1.residual.tt0, etc.. )
              must be available on disk. 

   nterms -- Number of Taylor terms to be used to model the frequency-dependence 
                 of the primary beam.
           example : nterms = 2
                nterms must be less than or equal to the number of frequencies specified via
                spwlist, chanlist and weightlist.
                nterms=1 will do a standard division by the average PB computed over all
                specified frequencies.

   threshold -- Flux level in the restored intensity map, below which to not 
                     recalculate spectral index. 
           example : threshold = '0.1Jy'

   action -- Choice of PB-correction with spectral-index recalculation
                or only spectral-index recalculation (using the specified threshold)
           example : action='pbcor'  or action='calcalpha'
               
           With action='pbcor', the following output images are created/overwritten.

              - imagename.pbcor.workdirectory  :  This directory contains an image cube with
                PBs at the list of specified frequencies, and Taylor-coefficient images that
                describe the PB spectrum.
                   -  imagename.pb.cube : Concatenated cube of PBs 
                   -  imagename.pb.tt0, tt1, ... : Taylor coefficients describing the PB spectrum
                   -  imagename.pb.alpha : Spectral index of the PB (for information only)
              - imagename.image.pbcor.tt0,tt1,... : Corrected Taylor coefficients
              - imagename.pbcor.image.alpha : Corrected Spectral Index
              - imagename.pbcor.image.alpha.error : New error map.

            With action='calcalpha', the following output images are created/overwritten
              - imagename.image.alpha : Corrected Spectral Index
              - imagename.image.alpha.error : New error map.

   reffreq -- Reference frequency about which the Taylor-expansion is defined.
            example : reffreq = '1.5GHz'
                 If left unspecified, it is picked from the input restored image.
                 Note : If reffreq was specified during task clean to produce the images
                           it must be specified here. 

   pbmin -- PB gain level below which to not compute Taylor-coefficients or
                apply PB-corrections.
            example : pbmin = 0.1

   field -- Field selection for the Primary Beam calculation. 
            example : field = '3C291'
                This field selection must be identical to that used in 'clean'

   spwlist -- List of SPW ids for which to make separate Primary Beams
   chanlist -- List of channel ids, within the above SPW ids, at which to make PBs.

             example :  spwlist=[0,1,2], chanlist=[32,32,32] 
                          Make PBs at frequencies corresponding to channel 32 of
                          spws 0,1 and 2.
             example :  spwlist=[0,0,0], chanlist=[0,10,20]
                           Make PBs at frequencies corresponding to channels 0,10,20
                           of spw 0
 
                   Primary beams are computed at these specified frequencies and 
                   for pointings selected by 'field'.  Taylor-coefficients that represent
                   the PB spectrum are computed from these images.

   weightlist -- List of relative weights to apply to the PBs selected via the
                     spwlist,chanlist parameters. Weights should approximately represent the
                     sum-of-weights applicable during imaging each of these frequencies.
              example : weightlist=[0.5,1.0,1.0] 
                                 The first frequency had less usable data due to flagged RFI,
                                 but the other two had relatively equal weight.
                     These weights are applied to the PB spectrum while computing
                     PB Taylor-coefficients. Setting weights to anything other than 1.0
                     makes a difference only with very lop-sided weights. 

  
        """
        if type(spwlist)==int: spwlist=[spwlist]
        if type(chanlist)==int: chanlist=[chanlist]
        if type(weightlist)==float: weightlist=[weightlist]

#
#    The following is work around to avoid a bug with current python translation
#
        mytmp = {}

        mytmp['vis'] = vis
        mytmp['imagename'] = imagename
        mytmp['nterms'] = nterms
        mytmp['threshold'] = threshold
        mytmp['action'] = action
        mytmp['reffreq'] = reffreq
        mytmp['pbmin'] = pbmin
        mytmp['field'] = field
        mytmp['spwlist'] = spwlist
        mytmp['chanlist'] = chanlist
        mytmp['weightlist'] = weightlist
        pathname='file:///'+os.environ.get('CASAPATH').split()[0]+'/share/xml/'
        trec = casac.utils().torecord(pathname+'widebandpbcor.xml')

        casalog.origin('widebandpbcor')
        if trec.has_key('widebandpbcor') and casac.utils().verify(mytmp, trec['widebandpbcor']) :
            result = task_widebandpbcor.widebandpbcor(vis, imagename, nterms, threshold, action, reffreq, pbmin, field, spwlist, chanlist, weightlist)

        else :
          result = False
        return result