Release Notes CASA 5.3.0

Summary of new features in this release of CASA

 The CASA 5.3 release builds on CASA 5.1. Changes compared to the CASA 5.1 release are listed below.



  •  We continue to update CASA Docs but are still in a transitioning phase, where in particular the description of the tools is not yet complete. Please use the old CASA Toolkit Manual if the tool description is not yet available on CASA Docs. All task descriptions are now in CASA Docs, and we will gradually phase out the inline help descriptions.


Data Import/Export

  • The tasks importfits now have a feature enabled that writes a history to the image it creates
  • The task importmiriad has a built in limit of 64 antennas; when more than 64 antennas are present, an exception is now thrown instead of crashing. There has also been a fix to the indexing so that importmiriad can now deal with data that contains 'wide' channels (spectral averages) for each spectrum.
  • importasdm now checks and eliminates duplicate data rows. 
  • importfitsidi now (1) has the added parameter "specframe", with default value "geo", to indicate the spectral reference frame; (2) works with specifying full paths; (3) has the scanreindexgap_s parameter defined on a per-antenna basis, effectively enabling subarraying in the decision regarding when to start a new scan.


MS Viewing, Editing, Manipulation

  • The task plotants has been rewritten to remove unwanted dependencies and add requested features for plotting antenna positions. New parameters allow the user to:

    • display antenna ID in addition to name;

    • plot the logarithmic positions;

    • exclude antennas from the plot or plot only those in the MeasurementSet main table (e.g. after a split);

    • set the title for the plot.

The old plotants task has been renamed oldplotants and will be deprecated.


  • The task plotms has been given the following features:
    • ability to compute and overlay an atmospheric transmission curve or a sky temperature curve, as available in plotbandpass. The parameters showatm (default 'False') and showtsky (default 'False') have been added to plotms for this feature. It can also be enabled in the plotms GUI by selecting the desired Overlay on the Plot > Axes tab (default 'None').

    • ability to provide information about calibration tables by clicking on the Summary menu in the top menu bar. If All is chosen from the pull-down menu next to Type, listobs-style output about scans, correlator configurations, and antennae will be written to the console or log.  Other options for a subset of the MeasurementSet include Where, What, How, Main, Tables, Antenna, Feed, Field, Observation, History, Polarization, Source, Spectral Window, Spectral Window and Polarization, SysCal, and Weather. For calibration tables, options in the Summary menu include All, Where, What, How, Main, Tables, Antenna, Field, Observation, History, and Spectral Window. See chapter page about the use of plotms.
    • ability to display a header above the plots. The contents of the header can be edited interactively from the GUI, or specified from the CLI using the new "headeritems" parameter.
    • all remaining functionality of plotcal has been implemented in plotms, pending the deprecation of plotcal. This includes the option to provide values in the parameter plotrange with numpy types, e.g., plotrange=[0,0,0,np.max([0.0,10.0])]. Only things not implemented in plotms compared to plotcal are support of baseline-based tables and connecting the dots in the plot.
    • A bug has been solved in plotms that affected delay tables: when an antenna has been completely flagged, plotms now produces a blank plot instead of skipping the plot for that antenna.



  • The calibration library has been updated and supports the CASA calibration tables that are used in standard calibration. The calibration library is a file that can be used in applycal to calibrate all fields in a single execution, or in plotms to calibrate data on-the fly without an execution of applycal
  • gaincal can now perform multi-band cross-hand delays
  • A new flux standard 'Perley-Butler 2017' is now available in setjy. It is also the new default.
  • The task plotbandpass now correctly handles data from the Nobeyama Radio Observatory, following an update of the getWeather function in the analysisUtils that are called by plotbandpass 
  • The experimental tasks accor and fringefit have been added to CASA for the reduction of VLBI data. The task accor determines the amplitude corrections needed due to errors in sampler thresholds using measurements of auto-correlations spectra (typically required for data correlated with a DiFX correlator, such as VLBA, and not for data from a SFXC correlator like the EVN). The task fringefit determines phase offsets, group delays and delay rates with respect to a specified reference antenna by a two-dimensional fast Fourier-transform and subsequent last-squares optimization.



  • phase centers in tclean can now be moving objects such as planets or ephemeris files  
  • tclean has a new stopping criterion nsigma that end cleaning by given multiples of the MAD noise of the residual image
  • A tclean mask will now be extended to all Stokes parameters if it was only created for a single Stokes plane
  • A new stokes parameter 'pseudoI' has been added to allow imaging data with visibilities that are partially flagged in one polarization hand but not the other. 
  • For widefield imaging (wprojectft) in tclean, a bug that under some cases caused increased peak residuals and higher noise towards the edges of the image has been fixed.
  • For very large images and number of wprojection planes there was a big spike in memory usage when running tclean. This has been addressed, and CASA will now try to respect amount of memory available for calculating the convolution function from the start of tclean 
  • Performance improvements in the auoboxing 'auto-multithresh' algorithm; the older options (auto-thresh and auto-thresh2) will be deprecated in favor of the new algorithm
  • Improvements in memory usage for tclean single and parallel mode (including a memory resource predictor)



  • statwt2 is a new task that will replace current statwt in CASA 5.4. In addition to the statwt functionality, statwt2 displays the mean and variance of the computed weights (also in preview mode), and prints those in the logger. Also, the datacolumn selection now supports 'residual' and 'residual_data' options, which will compute weights based on DATA - MODEL_DATA and CORRECTED_DATA - MODEL_DATA, respectively. statwt2 also has options to use robust statistic methods and has better control of flagging data. field, spw, and states can be combined for computation. 
  • imstat has significantly improved its performance for many cases where the paramter algorithm is not equal to 'classic' and parameter axes is specified.
  • imfit had pixel coordinates (pixelperarcsec) added to each component subrecord, to facilitate using these values in scripts.
  • The tasks imrebin, imregrid, immoments, imfit, imcollapse, imcontsub, imhead, immath, and impv now have a feature enabled that writes a history to the image it creates
  • A bug in the task impv has been solved, in which impv failed in mode='length' for pa='90deg' or pa='270deg'
  • The task immath can create an image of the total polarized intensity using the parameter mode='poli', which now calls the po.totpolint() tool. For more detailed information, see the task description pages of immath.


Single Dish

  • A new task sdsidebandsplit was implemented to separate single-dish data observed by DSB receivers
  • The sdbaseline and sdsmooth tasks have new parameter, reindex, to control whether or not indices in MS subtables are re-indexed based on data selection.
  • The task sdcal has a new interpolation option available. It can be used for Lissajous-scanned Single Dish images to suppress large gradient pattern along elevation direction observed when setting interp='linear'. In addition, performance for sdcal has been improved, and a bug has been fixed so that sdcal no longer fails to generate a sky caltable if the input data is Multi-MS.
  • A new experimental task, tsdimaging, has been defined. It is supposed to be equivalent to sdimaging but is based on new imager framework.
  • Performance for total power (TP) calibration has improved, especially for Solar data (double-circle fast scan).



  • The "limb-darkened disk model" is not working in through the cl tool and any reference to this has been removed from the documentation
  • The utilstool.compare_version method has been changed to return a string instead of a list of numerals. 
  • Many ms tool functions been refactored to use newer infrastructure code for selection and iteration, but have the same arguments and functionality.  The exception is that all selection is now cumulative; conflicting selections will result in a null selection (a MeasurementSet with zero rows).  For example, when selecting different data description IDs with ms.selectinit, you must reset the selection (ms.reset() or ms.selectinit(reset=True)) between the calls to selectinit.



  • mstransform now resizes the ANTENNA subtable when selecting on antennas, thus correctly handling MeasurementSets that include different antenna designs (e.g., 7m and 12m antennas in ALMA).



  • When going from CASA 5.3 to CASA 5.4, there are a number of tasks that will be deprecated. The list of tasks that will still be in CASA 5.3, but no longer in CASA 5.4 is the following:
    • autoclean
    • boxit
    • clearplot
    • csvclean
    • importevla (functionality is now in importasdm)
    • mosaic
    • oldhanningsmooth (functionality is now in hanningsmooth)
    • oldplotants
    • plotuv (functionality is now in plotms)
    • plotxy (already deprecated in 5.3, functionality is captured in plotms)
    • ssoflux (functionality is now in setjy)
    • statwt2 (will revert back to statwt, as described earlier in these CASA 5.3 Release Notes)
    • visstatold / visstat2 (functionality is now in visstat)