Release Notes CASA 4.2.0

CASA 4.2.0 is now available and the main feature improvements are listed below. In addition to the new features, many bugs were addressed and fixed.

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Note that in its current incarnation CASA is designed to support ALMA, and VLA data, as well as single dish data from ALMA and Nobeyama. Data from other telescopes, be it single dish or interferometers can be imported from uvfits, FITS-IDI , or sdfits formats into measurements sets (ms) or scantables in CASA. Given the variety of non-standard fits formats, we cannot guarantee that CASA will fully support data from all telescopes. However, efforts are made to support data formats from other facilities.

Obtaining the CASA Release

This version of CASA is available from our Download page. There, we also list the supported operating systems.

CASA Release Notes:

Valid for CASA Release 4.2.0 and later: Major improvements over the previous version of CASA include:

  • Imaging
    • outlier fields can now be used for all supported imaging modes
    • option for clean to obtain a cube with the smallest common synthesized beam
    • mosaicking in clean now uses frequency dependent primary beams
  • Data examination/editing/import/export
    • flagdata modes tfcrop and rflag now contain an extendflags parameter to extend flags along correlatiom, time, and frequency in a single pass
    • 'clip' flagging based on data weights
    • improvements in casafeather to display data as a function of radial uv-distance, use logarithmic axes, use a dirty cube for visualization, compute convolved data products, and display the output function
    • imregrid improvements to better conform to the template
    • The action='unapply' in task flagcmd has been modified so that it ONLY unapply the requested command without re-applying the others.
  • Calibration
    • setjy: Support for time-variable standard sources in 'Perley-Butler 2013'
    • Support for low frequency Heald and Scaife standards
    • Support for ephemeris objects
    • experimental CalLibrary option in calibration tasks to allow for more flexible mapping of calibration solutions
    • multi-band delay solution
    • support of full path for calibration against bandpass calibrators with spectral slope
    • introduction of a SOURCE frame for moving targets
    • gaincurve and opacity parameters are now removed from the calibration tasks. gencal will create corresponding tables
    • calwt in applycal is now a vector to apply or ignore individual calibration tables
    • calwt=False now resets the weights from the Sigma column
  • Simulation
    • improved algorithm for simalma
  • Data and Image Manipulation
    • New experimental task mstransform, which can do the same functionalities available in cvel, partition, hanningsmooth and split without the need to read and write to disk multiple times. All the transformations can be applied in combination or independently, controlled by Boolean parameters.
    • Baseline-dependent time averaging is available in task mstransform
    • Task mstransform is able to handle Measurement Sets that contain spectral windows with different polarization shapes as opposed to task split.
  • Data analysis
    • new task spxfit to compute the spectral index for single or multiple data cubes
    • rotation measure calculation in new task rmfit
  • Viewer
    • new image stacking display for more flexible changes in image ordering, and master image assignments
    • an image can now be changed between raster and contour without re-loading
    • a master image is not necessary anymore and images can be displayed in their individual coordinate systems
    • on the fly spectral smoothing
  • Single Dish
    • sdimaging
      • the task accepts more than one input MSes. The parameter name to specify input files is changed to infiles.
      • the task accepts more than one spectral windows in spw parameter.
      • auto calculation of the number of pixels (imsize) and pixel size (cell) of the image by default.
      • a new parameter outframe to specify the frequency frame of the image.
      • the task sets mask to the image. A new parameter minweight is available to define a threshold of weight to mask. Pixels in the image whose weight values are smaller than M*minweight are masked out, where M is the median of weight. The task also creates weight image for future reference and modification of mask.
      • the brightness unit of the image is set to 'K' when input MSes are in the unit.
    • sdflag2
      • a new task sdflag2 is available to flag scantable. This is an experimental task. It only modifies flag information in scantable, but does not filter rows in scantable as the older task, sdflag does.
      • the parameter timerange is available to select data to flag by time ranges.
    • sd.sbseparator module properly handles flag information in scantables.
    • sdcal2 The following bugs in sdcal2 have been fixed.
      • calmode='otf' and 'otfraster' will not work properly if any data selection parameters (iflist, scanlist, pollist, etc.) are specified.
      • calmode='tsys' has a bug that frequency labeling is not properly handled when multiple spectral windows are defined for Tsys measurement.
    • new PGPLOT-based, light-weight generic plotter sd.plotter2 is available
  • Performance
  • Other
    • updated third party packages
    • selectdata=True is the new default

    For more information, see the Known Issues page, and for general reference see the Using CASA help and documentation page.

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