eSASS4DR1 (eROSITA Science Analysis Software System for Data Release 1) is distributed as a .tgz archive for Ubuntu and macOS. Previous versions were also available in a Docker container for Windows and other Linux systems. However, Docker support is discontinued from patch no. 1 onward. Instructions on how to download, install and use eSASS4DR1 can be found in the following.
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erolib library from version 2.70.3 to 2.70.4. The previous version, erolib v2.70.3, caused a memory leak that prevented users from performing certain tasks - such as using evtool to create images.Thanks to valuable feedback from the user community, the eSASS4DR1 software is being actively updated and patched. Below is a chronological list of changes; however, users are strongly encouraged to install the latest release for the most up-to-date features and fixes:
erolib library from version 2.70.3 to 2.70.4. The previous version, erolib v2.70.3, caused a memory leak that prevented users from performing certain tasks - such as using evtool to create images.erolib library from version 2.70.4 to 2.70.5. The previous version, erolib v2.70.4, continued with a memory leak that prevented users from creating images of large areas in the skyThe following table shows the operative systems were the eSASS4DR1 release was tested:
| OS family | Name | Version | CPU architecture | native compilation |
|---|---|---|---|---|
| macOS | Catalina | 10.15.7 | X86_64 | OK |
| macOS | Big Sur | 11.7.10 | X86_64 | OK |
| macOS | Monterey | 12.6.8 | X86_64 | OK |
| macOS | Ventura | 13.6 | ARM64 | OK |
| macOS | Sequoia | 15.4.1 | ARM64 | OK |
| Linux | Ubuntu bionic | 18.04 LTS | X86_64 | OK |
| Linux | Ubuntu Focal | 20.04 LTS | X86_64 | OK |
| Linux | Ubuntu Jammy | 22.04 LTS | X86_64 | OK |
| Linux | Ubuntu Noble | 24.04.2 LTS | X86_64 | OK |
Minimum requirements:
The eSASS4DR1 package can be downloaded as a unique archive tarball from the following link:
eSASS4DR1 (including patch no. 2)
The package already includes a library patch released in October 2025 (eSASS4DR1 patch No. 2). If you have an existing eSASS4DR1 installation and want to apply the patch, please refer Section 4.
The CALDB is also available as a separate tarball. You can download it via the following link:
Note: The size of the CALDB is roughly 2 GB. Please make sure that you have enough space before downloading it.
After downloading the eSASS4DR1 package, you must move the file to an installation folder (/<my eSASS path>/) and extract the content. Extract it using the following command:
$ tar zxf eSASS4DR1.0.1.tgz
The eSASS4DR1 contains two subfolders: eSASS and external.
Similarly, the CALDB4DR1 can be extracted in a location of your preference. This exact CALDB path must be specified as a parameter during the installation process (see below).
The eSASS4DR1 software depends on several external libraries (e.g., HEALPix) to function properly. While these libraries are included in the eSASS4DR1 package, you may also use existing installations, provided they are compatible.
Careful configuration is required for the following external libraries.
Note: All other software packages in the external directory will be built automatically during installation.
There are two possibilities to configure HEALPix:
$ cd /<my eSASS path>/external/Healpix_3.50
and launch the configure script there:
gfortran). gcc, or gcc-** for macOS, i.e., specifying the version).libcfitsio.a library.locate can be used to find the directory ~/lib/ where libcfitsio.a is placed, which comes with the HEASOFT installation.echo $HEADAS/lib may give the location of libcfitsio.a). It is advisable to give the full path. Finally, execute: make.
The eSASS software also requires the fftw library installed in your system. In Ubuntu systems, it can be installed by typing sudo apt install libfftw3-double3 libfftw3-single3 libfftw3-long3 libfftw3-dev in a terminal. Note: This requires administrator privileges (i.e., your sudo password). In macOS systems, please install the fftw-3, fftw-3-long, and fftw-3-single, either using MacPorts or Brew.
macOS systems also require: autoconf, automake, coreutils, libtool, ncurses, readline, realpath, libpng, and perl.
From this point on, it is assumed that:
HEADAS.fftw library installed on your computer.You can proceed with the eSASS installation as described below.
Source your HEASOFT installation:
if you are using bash,
$ source $HEADAS/headas-init.sh
if you are using csh,
$ source $HEADAS/headas-init.csh
Go to the directory:
$ cd /<my eSASS path>/eSASS4DR1/eSASS/autoconf
The autoconf/automake needs to know the path to the various compilers. This can be done either by setting some environment variables before starting. To set up the required variables before starting:
in bash:
$ export CC=/<my path to gcc>/gcc $ export CXX=/<my path to g++>/g++ $ export FC=/<my path to gfortran>/gfortran $ export F77=/<my path to gfortran>/gfortran
in csh
% setenv CC /<my path to gcc>/gcc % setenv CXX /<my path to g++>/g++ % setenv FC /<my path to gfortran>/gfortran % setenv F77 /<my path to gfortran>/gfortran
The eSASS4DR1 configuration of the installation is achieved by:
$ aclocal $ autoreconf -fi -v $ ./configure --with-caldb=/<my CALDB path>/ --with-healpix=/<my HEALPix path>/ \ --with-headas=$HEADAS --with-gsl=compile --with-lapack=system
It is recommended to give the absolute path to the CALDB and HEALPix directories.
To verify successful configuration, the output should end with:
### CALDB SETUP ### configure: Using caldb directory /<full path to caldb> as you provided for setup ### Installation location: /<my eSASS path>/eSASS4DR1/eSASS ###
Continue the eSASS build by executing:
$ make $ make install
If you do not get any error messages, congratulations! Your eSASS build should now be complete.
Finally, run the command
$ make clean
to optionally remove files that are no longer needed after the completion of the build.
To enable the eSASS environment, execute the following command (either sh or csh version):
$ source /<my eSASS path>/eSASS4DR1/eSASS/bin/esass-init.[c][z]sh
For users that have installed eSASS4DR1 before October 2025, a patch to one eSASS4DR1 library is available. You can either reinstall eSASS4DR1 from scratch or patch your existing installation. If the first option is chosen, please make sure to rename or delete your current eSASS4DR1 folder and replace it with the one available above and install eSASS4DR1 as instructed in Section 3. If you want to patch your installation, please follow the instructions below.
Download the following file:
erolib-2.70.5.tgz: erolib v2.70.4, caused a memory leak that prevented users from performing certain tasks - such as using evtool to create images.
After downloading the erolib patch, you must move the file to your eSASS4DR1 installation and extract the content there:
$ mv /<my download area>/erolib-2.70.5.tgz /<my eSASS path>/eSASS4DR1/eSASS/erosita/task/ $ cd /<my eSASS path>/eSASS4DR1/eSASS/erosita/task/ $ tar zxvf erolib-2.70.4.tgz
Then, go to the directory /<my eSASS path>/eSASS4DR1/eSASS/autoconf/libraries/erolib/ and open the file called Makefile.am and move the line containing the module erolib_linklist2_mod.f90 just below the module erolib_linklist_mod.f90. Save and close the file.
Finally, go to the directory /<my eSASS path>/eSASS4DR1/eSASS/autoconf/ and execute:
$ make clean $ make $ make install
Make sure that you have sourced HEASOFT previously, and if possibly, the same version you used to install eSASS4DR1.
The eSASS team provides a script to test your eSASS4DR1 installation. This script can also help you learn to call the different eSASS tasks and code in python3 for exhaustive works with eROSITA data.
In the subfolder /<my eSASS path>/eSASS4DR1/eSASS/scripts/, you can find a python3 script named demoscript_DR1.py. This script calls all the eSASS tasks with some predefined parameters. demoscript_DR1.py takes two parameters as input: an event file name and an output folder name. You can give the relative or absolute path for both files. You can call the script's help by running:
python3 $SASS_ROOT/scripts/demoscript_DR1.py -h
As mentioned in the introduction, starting in May 2025, eSASS4DR1 includes a patch. The previous version of eSASS4DR1 was also available as a Docker container for users without access to Ubuntu or macOS. The patched version is no longer available via Docker. If you wish to use the unpatched Docker version, please refer to this page. Note, however, that some eROSITA tasks may not be fully functional.