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Release Notes CASA 5.4.0

Release Notes CASA 5.4.0

by Jared Anand Crossley last modified 2018-10-11T22:54:10-04:00
Summary of new features in this release of CASA

The CASA 5.4 release builds on CASA 5.3. Changes compared to the CASA 5.3 release are listed below. The CASA 5.4.0 release includes usage of the ALMA pipeline (the VLA pipeline will be accommodated in a subsequent CASA 5.4.1 release).

 

General

  • At the time of the CASA 5.4.0 release, several issues involving mosaicing in versions 4.7.2 and 5.1.1 tclean were under investigation, focusing specifically on ALMA mosaics. Timely updates will be provided in the online copy of these CASA Docs: https://casa.nrao.edu/casadocs.  All known issues have been fixed in CASA 5.4.0.
  • A number of tasks have been deprecated in CASA 5.4: autoclean, boxit, clearplot, csvclean, importevla (use importasdm instead), mosaic, oldhanningsmooth, oldpartition, oldplotants, plotuv (capabilities transferred to plotms), plotxy (capabilities transferred to plotms), ssoflux, widefield, visstatold and visstat2.
  • The deprecated task importevla is now replaced by importasdm, but several additional step in parameters specification and flagging of zero and shadowed data are required to replicate the functionality of importevla, as described in the CASA Docs task pages of importasdm.
  • The task statwt2 is now statwt (the previous startwt is now oldstatwt)
  • statwt has changed its syntax for choosing which channels to take into account regarding the weights calculation. It now uses the parameter excludechannels to exclude channels from the weights calculation.
  • Starting CASA 5.4, telemetry data is by default generated for each CASA run and sent anonymously to NRAO to measure statistics on CASA task useage. This feature can be disabled by setting the CASA_ENABLE_TELEMETRY environment variable to "false".

Documentation

  • We continue to update CASA Docs, but are still in a transitioning phase of making CASA Docs the main source of information on CASA. All task descriptions are now in CASA Docs, and we will gradually phase out the inline help descriptions. We are slowly rolling out additional documentation on remaining areas of CASA as we are able to test and verify the functionality matches the description.

Data Import/Export

  • Ephemeris data for the Moon, based on JPL-Horizons with a cadence of 1hour, has been added as a standard DE200 ephemeris table.
  • importnro now imports Nobeyama data with data stored in UTC, rather than JST (UTC+9).

MS Viewing, Editing, Manipulation

  • flagmanager now returns a dictionary for mode='list', returning the flag version names and comments. 

Calibration

  • plotms inherited the functionality of plotcal and now supports all calibration tables. plotms now also offers plotting scalar residuals. In addition, plotms supports simple text export, which just exports X and Y values, in addition to the default verbose export.

Imaging

  • Automasking has been finalized, with refined performance and improved noise calculations.
  • tclean now fully supports mosaics of ephemeris objects spanning one or more execution blocks through the new parameter phasecenter. For ALMA data, phasecenter='TRACKFIELD' uses the ephemeric tables attached to each MS. For the latest ephemeric information, or for non-ALMA data, one may set phasecenter to the name of the ephemeris file, or a body for which a DE200 ephemeris table is distributed with CASA ('MERCURY', 'VENUS', 'MARS', 'JUPITER', 'SATURN', 'URANUS', 'NEPTUNE', 'PLUTO', 'SUN', 'MOON')
  • For mosaic imaging with Briggs/uniform weighting in tclean, the mosweight sub-parameter of gridder='mosaic' has been added to tclean with default setting mosweight = True (compared to the old mosweight = False default in clean). The default mosweight = True optimizes noise characteristics for ALMA mosaics, but (1) does not yet work for parallel processing of continuum images (specmode = 'mfs' or 'mtmfs'); (2) may potentially cause memory issues for large VLA mosaics; (3) may cause the major and minor axis of the synthesized beam to be up to ~10% larger than with mosweight=False. Please change to mosweight=False to get around these issues.

Analysis

  • To calculate robust statistics in imstat, an algorith = 'biweight' option has been added to determine the center and width of a distribution while downweighting points that are far off, e.g. due to the presence of significant, wide spread signal.
  • CASA can now handle Double and Complex-Double images.

Bug-fixes (selected)

  • In imregrid, the conversion between galactic and J2000 coordinates that previously caused a wrong tilt to high declination targets has been fixed
  • In simobserve and  the underlying tool ia.modify, point-sources from a component-list were assigned the wrong WCS coordinates in CASA 5.3, because the x and y pixel positions were swapped. This issue has been fixed for CASA 5.4, and only affected CASA version 5.3.
  • A bug was fixed where multi-EB ephemeris data sets produced a wrong image with tclean parameter settings deconolver='mtmfs' and nterms=2
  • In rflag, the parameters 'timedevscale' and 'freqdevscale' now operate in the 'apply' mode, whereas previously the values were written to the flag file during the 'calculate' mode only, and any settings during the 'apply' stage were silently ignored.
  • In split, specifying a spw selection with multiple channel ranges within a single spw (e.g., spw='1:2~6;10~12') now creates the correct DATA_DESCRIPTION subtables
  • In sdimaging, a bug was fixed that caused wrong computation of pointing directions when multiple fast-scan MS files are given as input.
  • In importnro, several bugs that causes data inconsistency in output MS have been fixed

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