Release Notes CASA 3.4.0

CASA 3.4.0 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 EVLA, ALMA, and VLA data, as well as single dish data from ALMA as well as 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 3.4.0 and later: Major improvements over the previous version of CASA include:

  • Flagging
    • New flagging infrastructure via new tasks tflagdata and flagcmd with substantially improved performance and extended capabilities (see below).
    • The previous version of the flagcmd task was renamed to oldflagcmd. The interface has been re-designed and several parameters have been renamed.
    • The tasks flagdata and flagdata2 are still available in CASA 3.4 but they will both be replaced by the new tflagdata task along with the CASA 3.5 release. Please consider this for scripting as some parameters have changed in tflagdata. All improvements below refer to the new tasks.
    • Time-baseline auto flagging algorithm (mode='tfcrop') in tflagdata with improved plotting capabilities to visualize flagged visibility points per baselines, and navigate through fields, spws and scans (formely part of testautoflag).
    • Threshold-based flagging (mode='rflag') in tflagdata (originally implemented by E.Greisen in AIPS Dec2011]).
    • Added mode='list' to tflagdata to combine any number of flag commands in one single run.
    • Support for water vapor radiometer (WVR)-based expressions (e.g. 'ABS_WVR') in auto-flagging algorithms (mode=clip,tfcrop,rflag).
    • Added flexible iteration capabilities for the time dimension in the auto-flagging algorithms (mode=tfcrop,rflag).
    • In mode='clip', automatically flag NaNs by default, and optionally exact zeros with the new sub-parameter clipzeros.
    • Shadowing can be calculated for antennas that are in the array but are not present in the MS.
    • Support at the tool level to handle flagging of the new CalTablecalibration table format (all modes except for elevation and shadow).
    • New cmdreason sub-parameter to allow saving reasons to the outfile (or to the FLAG_CMD table).
    • The task flagcmd now supports all modes that exist in tflagdata (except for mode=summary).
    • The flag commands are NOT automatically saved to the FLAG_CMD sub-table in the flagcmd task. The user needs to set savepars to True in order to achieve this.
    • New selection by reason from an input text file in both tasks.
    • Tasks importevla and importasdm now have flag-command-import options.
    • The flagversions names have changed. The backup names do not take a mode as part of their names anymore. They only take the task name along with an index. Example: flags.tflagdata_1 or flags.flagcmd_1.
    • The vector mode of the old flagdata is gone. The user can achieve the same results using the inpmode='cmd' of the flagcmd task. See the task inline help for more details.
  • Imaging
    • multi-field support for multi-term clean
    • clean with nterms>1 will output a spectral index error map
    • experimental parallelized clean task (pclean)
  • Data examination/editing
    • new imstat output formatting, including an output file option
    • listobs output can be written to a file
    • in concatenated data sets, it is possible that an antenna is on different antenna stations at different times. We introduced the "antenna@station" syntax for data selection to accommodate such situations
    • new task listfits to display fits headers (images and uv data)
    • data selection in listobs
    • plotms: UVW coordinates can now be displayed in units of wavelengths (enabling the full uv-coverage view of multi-frequency syntesis data)
    • new task asdmsummary displays a summary of the content of an ASDM.
  • Calibration
    • the creation of the MODEL column is now optional, calibrator models are computed on the fly when needed. This increases the performance of CASA and reduces disk space requirements. A consequence is that the calready parameter is obsolete in clean.
    • new calibration table format (not compatible with the old format)
    • calibration tables are now independent from the original MS
    • frequency interpolation of calibration tables
    • conversion script caltabconvert to convert old (CASA 3.3 and earlier) to new calibration tables (CASA 3.4 and later) - note: we recommend to regenerate the calibration tables with calibration tasks if possible as some information will be not availbale by simply converting old to new caltables.
    • improved solar system models in setjy
    • MS data selection fully supports observation ID
    • wvrgcal to generate a calibration table from water vapor radiometer ALMA data
    • automatic lookup of EVLA antenna position changes in gencal caltype=antpos
    • new task plotweather to display the weather conditions. plotweather also calculates the atmospheric opacities for each spw using actual and historical weather data for the EVLA
    • uvcontsub supports fitorders > 1 for continuum subtraction
  • Simulation
    • simulations are now in LSRK
    • ALMA cycle 1 array configurations are included
  • Data and Image Manipulation
    • improved feather task, including new parameters for weighting data, single dish amplitude scaling, and plotting
    • concat can now apply additional, user supplied weights to the input data sets
    • imtrans has a new option to invert image axes
    • new task statwt to derive visibility data weights based on their scatter
  • Data im/export
    • performance improvements in importasdm, incl. full support for large data files
    • ALMA ASDMv3 as default in importasdm
    • The ASDM Pointing table has a new optional column atmosphericCorrection to reflect resulting atmospheric refraction
  • Data analysis
    • zero level fitting in imfit
    • support for constrained Gaussian multiplet fitting in specfit (e.g. for hyperfine line fitting)
    • logfile support in specfit
    • Lorentzian profile fitting in specfit
    • imstat now includes a mask parameter
    • spectra line search tool can now return a python dictionary
    • support of masks with degenerate axes in all image analysis tasks
  • Viewer
    • new CASA region syntax is now partially supported in the viewer, incl. loading/saving regions, plotting, creation and modification of regions
    • image statistics within regions in the viewer are now displayed in a separate dock. The values are updated as the region is dragged across an image
    • Gaussian and polynomial fitting of spectra in the viewer spectral profile tool
    • plotting of errors in the spectral profile viewer
    • mean, median, and sum image construction across the spectral axis (imcollapse functionality) from within the viewer spectral profile tool
    • selecting a position in the spectral profile tool with CNTRL-click jumps to the corresponding plane in the cube
    • saving of images from within the viewer (in CASA or FITS format)
  • Single Dish
    • automatic import of single dish tasks at CASA startup
    • renamed sdcal to sdreduce and sdaverage to sdcal
    • new task sdgrid to convolve single dish map data onto a regularly spaced grid
    • channel binning in sdsmooth
  • Performance
    • unified, optimized visibility access for some tasks
    • substantial performance improvements in importasdm (including importevla), tflagdata, and flagcmd, experimental parallelized clean pclean
    • The new flagger has successfully deployed asynchronous-I/O for flagging modes that read visibility values.
  • Other
    • when installing Linux rpms, it is now possible to have more than a single version of CASA on disk. Versions can be invoked with like casapy --release 3.x.x
    • improved support for special characters in MS field names
    • MWA, EVN, LOFAR, Effelsberg are now recognized observatories
    • pyfits is now included in CASA

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

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