13.3 Processing data: using the PIPELINE

Some imaging strategies cannot be used directly on polarized data. Also, the automatic definition of supports ( MASK /THRESHOLD) only makes sense on Stokes I or parallel hand polarization states, not on Stokes Q,U,V or cross-hand states. The same applies to spectral line identifications.

PIPELINE processing:

The PIPELINE command does not automatically handle polarization data. However, through judicious use of the PIPELINE SELECT and PIPELINE FIND commands with ad-hoc filters, imaging, including self-calibration, is possible through custom (though simple) scripts.

The script self-polar.ima just does that, and follows the naming conventions used by the MAP_POLAR command. Schematically, this script would contain the following commands to treat all spectral windows:

  CATALOG               ! No catalog, no Line emission
  ! "Split the X+Y (XX,YY,XY,YX) UVFITS file into I,Q,U,V Stokes UV tables"
  @ stokes-split &1     !
  ! Setup the pipeline
  IMAGER\PIPELINE ?
  IMAGER\PIPELINE organize        !  " Move UV tables to RAW/"
  sic mkdir UVFITS
  SIC\SYSTEM " mv *.uvfits UVFITS/"
  SIC\SYSTEM " mv RAW/&1.uvt .."  !   "Remove the X+Y UV table from RAW/"
  !
  ! Select the I image for self-calibration
  let all%filter *-I
  IMAGER\PIPELINE select
  IMAGER\PIPELINE compute
  !
  ! Apply self-calibration solution to I,Q,U,V data
  let all%filter *
  IMAGER\PIPELINE find
  IMAGER\PIPELINE select
  IMAGER\PIPELINE collect
  IMAGER\PIPELINE apply
  ! Image every thing consistently
  IMAGER\PIPELINE image
  PIPELINE SAVE

The actual script (use type split-polar to list it) is a bit more complex, to avoid repeating steps already performed, to allow treating only specific windows, carry on noise information, and in the end process the continuum images.