CASA

Release Notes CASA 3.3.0

CASA 3.3.0 is now available and the main feature improvements are listed below. In addition to the new features, many bugs were addressed and fixed.

We occasionally issue patches and 'stable' versions of CASA. To get notified, please subscribe to the 'casa-users' mailing list. 'Stable' as well as CASA releases are available at Obtaining CASA. Releases will be announced via the 'casa-announce' mailing list. To subscribe, please visit the mailing lists webpage. For feedback, and help please go to the NRAO helpdesk; for ALMA questions please use the ALMA helpdesk

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 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. Note that for CASA 3.3. we dropped support for MacOS 10.5 (Leopard) but are now supporting both, 10.6 (Snow Leopard) and 10.7 (Lion).

CASA Release Notes:

Valid for CASA Release 3.3.0 and later:

Major improvements over the previous version of CASA include:

Flagging

testautoflag: new, experimental task for autoflagging data based on piecewise fitting of the bandpass in the time and frequency domains

Imaging

clean masks for main and outlier fields in clean now use the same format please use the new CASA region format (see below), boxfile format support etc. will be removed in upcoming CASA releases

Data examination/editing

plotms: also displays the antenna station name
plotuv: new task to plot the visibilities in the uv-plane
listvis: now labels all entries with their units
ms.select() is a new method to select visibilities on the tool level with a selection syntax similar to that in CASA tasks
listobs: can now write the output to a text file

Calibration

setjy: A spectral index is now supported as input for flux calibration
setjy: Arbitrary fluxes, and spectral index can be applied to model images
setjy: The parameter listmodimages will list all available calibrator models. Standard calibrator models don't need their full paths anymore
bandpass, gaincal, applycal: The opacity parameter can now be a list of opacities, one entry for each spectral window
gaincal: gaintype='K' is implemented to solve for antenna based delays
data selection based on scan intents and observation id is now supported in most calibration tasks
EVLA switched power calibration available in gencal (caltype='evlagain')
ALMA Tsys calibration available in gencal (caltype='tsys')
previous uvcontsub2 has been renamed and is now replacing uvcontsub
the reference antenna in calibration tasks can now be a list of antennas. If the first antenna is not available, the second entry will be used etc.
calibration tasks now use minsnr=3 as default for the minimum signal-to-noise ration of data to be included in the solutions
Model for the EVLA calibrator 3C147 in L-band is now available

Simulation

The simdata task has been split into two tasks, sim_observe and sim_analyze, to reduce the complexity for new users, and facilitate the combination of multiple arrays. sim_observe is used to create measurement sets from model images and component lists, and optionally add thermal noise and cross-polarization. sim_analyze is used to image datasets and graphically assess their fidelity. The original task simdata is retained in CASA 3.3 but will be removed in the future.
better handling of simulation from components and clarification of the units for reported statistics.
More flexibility in simulating sources around transit
a thermalnoise seed parameter will now ensure randomness of noise
the default velocity frame for simulated data is now LSRK rather than TOPO

Data and Image Manipulation

fixvis: new parameter phasecenter to change the direction of the phase center of the visibilities. Changes can be absolute or relative
concat can now optionally omit copying (and concatenating) the POINTING table
impbcor, ia.pbcor() new task and tool method for primary beam correction of images
immath: a stretch parameter in the mask selection will extend a smaller mask to the full size of the data cube (e.g. a moment0 mask to all channels)
the default for channel interpolation during regridding processes is now 'linear' in most tasks

Data im/export

full ICRS coordinate support
upgrades to importasdm and exportasdm to support ASDM v1.3
importasdm can now optionally omit importing the POINTING table
importevla: EVLA switched power can now be filled from an SDM into an MS

Data analysis

imfit: now optionally performs fits on a plane-by-plane basis if given multiple channels
imfit: now derives the integrals and associated errors of the fitted Gaussians
imspec: accepts initial values for Gaussian fitting
imstat: now derives statistics in slices of data, e.g. across RA/DEC per channel map

Viewer

A distance measurement tool has been added
the spectral line tool can now plot errorbars on the spectrum
support of error cubes in viewer
the spectrum of a cube can be derived as an average, sum, median, and weighted average of a selected region
better support of spectral units
elliptical region tool added

Single Dish

sdbaseline: Automated sinusoidal fitting based on FFTs
more uniformity in infile/outfile parameter naming throughout the single dish package

Performance

Copying the POINTING subtables is now 75-300 times faster
partition: new task to split a MS into a multi-MS that is optimized for parallelized processing
tasks flagdata, clearcal, applycal now work in parallelized mode, ie. they make use of multi-core multi-node processing
pcont tool method for parallelized imaging and deconvolution of continuum data

Other

New format for CASA regions. The new ascii format supports a large variety of shapes, offers flexibility for different coordinate systems and can be used as regions and annotations. See the reference manual for details (or the description on CASAguides). The new region format can be used in almost all tasks and we offer limited support to write out the new format in the current CASA viewer. Full support will be available in the next release.

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