SSB Download Server

Space Telescope Science Institute

Science Software Branch Download Server

SSB IRAF + Python Software Distributions


Ureka has been deprecated as of 04/26/2016. Please consider switching to STScI's Conda-based solution, AstroConda. Current and previous versions of Ureka will remain available for download and installation, but will no longer receive updates.

The Science Software Branch (SSB) distributes three software bundles that contain many useful astronomy packages, including:

There are three different distributions because of ranging user needs: some want the bleeding-edge development software (SSBDEV and SSBX), while others need a more stable environment (SSBREL).


Release Schedule

SSBREL As of 04/26/2016:

No futher updates will be applied to SSBREL.

This is the final public release.

A full list of included package versions can be found here.
SSBX As of 04/26/2016:

The SSBX distribution is no longer functional due to recent changes in our build infrastructure. Please use SSBDEV instead.

This is the testing environment. It is updated weekly, broken occasionally, but has the most recent bug fixes. You should use this if you need some bug fix or new feature now, and can't wait for the next public release.

This package contains everything in SSBREL, except that it has current versions of SSB development software (including JWST pipeline, STScI Python, CRDS, and HSTCAL packages)

A full list of included package versions can be found here. Documentation for STScI Python in SSBX can be found here.

We update SSBX on Sundays between 9 PM and 3 AM.
SSBDEV As of 06/22/2016:

The SSBDEV distribution is no longer rebuilt nightly. The final build will remain available.

SSBDEV is built nightly with all the latest development code. We run our regression tests against this build, so it it should be considered untested and unstable. Only use SSBDEV if there is a specific need to do so, and only use it for as long as necessary.

We update SSBDEV every night between 9 PM and 3 AM.

Using PyRAF

PyRAF is a Python replacement for the IRAF CL. There is a description at, including a tutorial.

We are no longer developing PyRAF and we only have the resources to provide minimal support for it.

You can find some information about configuring PyRAF here.

Legacy Information

You can find some outdated notes for Mac users here. Topics include how to install CDBS from a DMG file and how to remove obsolete files in /usr/stsci.


If you have any questions or problems, please send mail to Be sure to include "SSBREL", "SSBX", or "SSBDEV" (as appropriate) in the subject line.