Feb 19, 2020: A new CASA 5.6.2-3 patch is available for use with the VLA pipeline. The previous version CASA 5.6.2-2 contained a bug in the VLA pipeline, where restoration of MSs (e.g., when restored through the new interface to the NRAO archive) produced incorrect results between Oct 21 2019 and Feb 2020. All CASA functionality in CASA 5.6.2-3 is equivalent to that in CASA 5.6.2-2 and CASA 5.6.1-8. See CASA Docs for more information.

Dec 17, 2019: CASA 6 is now available for developers and power users. This CASA 6 version offers the CASA tools and tasks as modules for pip-wheel installation in Python 3. The tools and tasks in CASA 6 are in content the same as those in CASA 5.6.1. Not all GUIs are included in this first version of CASA 6. See the Section "CASA 6" below for details.

Dec 3, 2019: Catalina OSX 10.15 version of CASA 5.6.1 is now available. This 10.15 version is not officially supported by the CASA team, but it passed the standard tests, so it should work the same way as the OSX 10.14 version. This 10.15 version can be downloaded here. More details are given in the section below on Supported Operating Systems.

Obtaining the CASA Release

Supported Operating Systems

The latest CASA release 5.6.1 is available for the following operating systems:

  • Linux
    • Red Hat 7
    • Red Hat 6
  • Mac OS X
    • macOS 10.14 (Mojave)
    • macOS 10.13 (High Sierra)
CASA may also work on other flavors of Linux, but only the operating systems listed above are officially supported by CASA, because these we run regular tests on.

Catalina OSX 10.15 users: we now have a version of CASA 5.6.1 that works on OSX 10.15. You can download it here. This version is not officially supported, but it passed the standard tests, so it should work the same way as the OSX 10.14 version.

Please note that when you try to open this OSX 10.15 version of CASA, there will be an Apple security warning that we cannot get around at the moment: “CASA” can’t be opened because Apple canot check it for malicious software. To get around this, you will have to click ‘ok’ and then go to System Preference —> Security & Privacy to “Open Anyway”.

The CASA team welcomes feedback on this unsupported OSX 10.15 version:

OS X users should be aware that it may be necessary to temporarily bypass Apple's Gatekeeper security system to run CASA for the first time after downloading it. This can be done by using "Ctrl+click" on the downloaded application file and selecting "Open" from the contextual menu. Details can be found here.


Please follow these links for downloading the current release of the code for your specific operating system. Installation instructions are provided, too. Links to previous releases are given at the bottom of this page.
CASA Pre-releases are code under development. Use with caution as the code is still undergoing changes, is less tested and not well documented.

Alert for pipeline use: The ALMA and VLA pipelines are included only in certain versions of CASA. Please ensure to download the correct CASA pipeline version for your data. The latest versions of CASA with a pipeline that has been scientifically validated for ALMA or VLA are given below.

CASA Pipelines
CASA Release
CASA Pre-releases
CASA containing ALMA pipeline
CASA containing VLA pipeline
Linux Packages Installation
Red Hat 7
Red Hat 6
Mac OS X Packages Installation
OS X 10.14 (Mojave)
OS X 10.13 (High Sierra)
* The CASA 5.6.1-8 version for general use is identical to the CASA 5.6.1-8 pipeline version that is used by the ALMA pipeline. Both links therefore point to the same casa-pipeline-release-5.6.1-8.x file, which has the ALMA pipeline included. The CASA 5.6.1-8 version is also functionally equivalent to CASA 5.6.2-3, which contains two bug fixes relevant to the VLA pipeline.
** Pipeline version number 42866.
*** Not available for OSX 10.13. For manual processing, please use CASA 5.6.1-8.


CASA now collects usage statistics including task execution timings and crash reports. This data will be periodically sent back to NRAO to guide future priorities and decision making. All collection is anonymous and contains no scientific or personal data.

You can disable telemetry by adding the following line in your ~/.casarc file: EnableTelemetry: False
For more information, see CASA Docs


CASA 6.0 has been reorganized to offer a modular approach, where users have the flexibility to build CASA tools and tasks in their Python environment with the use of pip-wheels. CASA 6.0 includes the casatools, casatasks, and casampi modules, which are scientifically equivalent to those in CASA 5.6.1.

Instructions on how to install CASA 6.0 can be found in CASA Docs:
CASA 6 Installation and Usage

This first 6.0 release is targeted at developers and power users who build CASA into their own software applications and pipelines. The CASA 6.0 release is scientifically equivalent to the tools, tasks, and mpi capabilities available in CASA 5.6.1; the modules pass the same verification and unit testing required from CASA 5.6, and no new features are available in this first release of CASA 6.0 relative to CASA 5.6.1. Consequently, they share the same documentation as CASA 5.6, with the addition of the above CASA 6.0 specific page with installation instructions.

The initial CASA 6.0 Release is not intended for general users doing manual data reduction. It lacks much of the custom interactive shortcuts present in CASA 5 and many of the graphical user interfaces. Development continues on the data visualization packages, including casaplotms, casaviewer, and CARTA, as these involve external applications executing outside the python environment.

An upcoming 6.1 release scheduled for the spring of 2020 will contain a complete replacement for all CASA 5 components, including a single tar file distribution for those wishing to continue to install CASA in that manner. This monolithic package will be built from the same modular pip wheels, but adds a CASA-shell component to replicate the appearance of previous CASA versions.

Supported Operating Systems CASA 6.0

Initially, we are targeting Python 3.6 as provided by RedHat for our wheel production, with RH6 and RH7 as official supported platforms for CASA 6.0. We have had some success on other Linux-based platforms as well.

Release Information

The Release Notes and Known Issues of the 5.6 releases, as well as previous releases, are available in CASAdocs

Hardware Requirements

The reduction of radio data in CASA can be demanding in terms of hardware, and a balanced configuration regarding memory, processing power and file I/O may be required to efficiently run CASA.

Recommendations on the CASA hardware requirements for VLA and ALMA data can be found on the 'Hardware Requirements' pages of CASA Docs.

Open-file errors: For mosaic imaging in tclean, it may be necessary to raise the ulimit to avoid and error “too many open files”, e.g. by setting ulimit -n 16384. In some cases, it is not sufficient to only raise the soft limit, but also the hard-limit, which requires admin/root permissions. ALMA strongly recommends users to set ulimit to at least 16384 for both the soft and hard limit to avoid potential open-file errors with mosaic imaging in tclean.

Older Releases

CASA 5.6.1 (Redhat 7 - Redhat 6 - MacOS 10.14 - MacOS 10.13)

RedHat 7 (CASA 4.7-5.6.0)
RedHat 6 (CASA 4.3-5.6.0)
RedHat 5 (CASA 4.3 - 4.6)
RedHat (CASA <=4.2.2)

MacOS 10.14 (CASA 5.5-5.6.0)
MacOS 10.13 (CASA 5.3-5.6.0)
MacOS 10.12 (CASA 5.0-5.4.2)
MacOS 10.11 (CASA 4.6-5.1.2)
MacOS 10.10 (CASA 4.4 - 4.7)
MacOS 10.9 (CASA 4.4 - 4.5)
MacOS 10.8 (4.3); OSX 10.8 (<=4.2.2)
MacOS 10.7
MacOS 10.6
MacOS 10.5

Other Links

CASA Source Code -- (Notes).

Contributed CASA scripts

If you need additional help, please consult our NRAO helpdesk or ALMA helpdesk

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