CASA 5.6

Warning to all VLA users, 11 Feb 2020: A bug was found in the version of the pipeline that was packaged with CASA 5.6.2-2 (the initial CASA 5.6.2 version for VLA). This bug impacts the restoration of calibrated MSs, and affects all VLA projects that restored pipeline calibration after October 21, 2019. If an existing calibration was restored using the new interface to the NRAO archive or following the instructions on the pipeline web-pages, you will obtain incorrect results. The output from a full calibration run of the pipeline is not affected by this bug, nor is data restored prior to October 21 2019, or data restored with a different version of CASA. As per Feb 19, a new CASA 5.6.2-3 version is available in which the problem has been fixed. The pipeline team will update affected users.

CASA, the Common Astronomy Software Applications, is the primary data processing software for the Atacama Large Millimeter/submillimeter Array (ALMA) and Karl G. Jansky Very Large Array (VLA), and is often used also for other radio telescopes.

The CASA 5.6 series includes three official CASA releases to date, CASA 5.6.0, 5.6.1, and 5.6.2, which can be downloaded here. All three 5.6 versions are suited for manual data processing. CASA 5.6.1 has also been scientifically validated for ALMA and includes the ALMA Cycle 7 pipeline, while CASA 5.6.2 includes the latest version of the pipeline that has been scientifically validated for the VLA.

The CASA 5.6 releases build on CASA 5.5, but have the following main new features:

New Features

  • Task bandpass now supports relative frequency-dependent interpolation when applying bandpass tables.
  • For fringefit, a new keyword niter determines a maximum number of iterations for the global least squares solver.
  • In tclean, a new parameter ‘smallscalebias’ for deconvolver = ‘mtmfs’ more efficiently cleans signal on different spatial scales.
  • plotms can show atmospheric and sky temperature curves, enhanced pointing plots and more accurate axis labels.
  • In tclean, the auto-multithresh now functions with polarization data.
  • A new task nrobeamaverage is available Nobeyama data, to average on-source data over different beams.
  • tsdimaging has new modes to track ephemeris objects.
  • In sdcal, the 'otf' calibration mode has improved.
  • simobserve can create multi-channel MeasurementSets from a component list. ALMA receiver temperatures were updated. 
  • The statwt task log has been updated to provide explicitly the channels used in the statwt calculations.
  • The ATM library of atmospheric models has been updated in CASA.
  • A bug was fixed in tclean where explicitly setting the restoringbeam parameters produced a wrong flux scaling of the residuals.
  • Improvements have been added to the 'mosaic' and 'awproject' gridders in tclean, and a new suite of verification tests were written to evaluate joint mosaicing and wideband imaging.
  • A large number of memory leaks have been addressed in the code.

For more details and other implementations, please see the CASA 5.6 Release Notes.


CASA is developed by an international consortium of scientists based at the National Radio Astronomical Observatory (NRAO), the European Southern Observatory (ESO), the National Astronomical Observatory of Japan (NAOJ), the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), CSIRO Astronomy and Space Science (CSIRO/CASS), and the Netherlands Institute for Radio Astronomy (ASTRON), under the guidance of NRAO.