Installation

To install

pip install romanisim

and you should be largely set!

The most frequently encountered difficulty installing romanisim is when GalSim is unable to find FFTW. If your system does not have the FFTW library, these should be installed before romanisim and GalSim. Only python <= 3.13 is support at present due to the lack of a Python 3.14 wheel for galsim.

Another problematic dependency is STPSF, which requires data files to operate. See the docs for instructions on obtaining the relevant data files and pointing the STPSF_PATH environment variable to them. The simplest option for getting things to run is to use --psftype=galsim which relies on the GalSim PSF modeling.

Additionally, some synthetic scene generation tools use images of galaxies distributed separately from the main GalSim source. See here for information on obtaining the COSMOS galaxies for use with GalSim. The romanisim package also has a less sophisticated scene modeling toolkit, which just renders Sersic galaxies. The command line interface to romanisim presently uses Sersic galaxy rendering, and so many users may not need to download the COSMOS galaxies.

Finally, romanisim can work with the Roman CRDS system. Using CRDS requires specifying the CRDS_PATH and CRDS_SERVER_URL variables. Using CRDS brings in the latest reference files and its use is encouraged; specify the --usecrds argument to enable it.

In summary, the basic install process looks like this:

pip install romanisim
# to get a specific version, use instead
# pip install romanisim==0.1
# to be able to run the tests for a specific version, use instead
# pip install romanisim[test]==0.1

# get stpsf data and untar it
mkdir -p $HOME/data/stpsf-data
cd $HOME/data/stpsf-data
wget PATH_TO_STPSF_FILES -O stpsf-data.tar.gz
tar -xzf stpsf-data.tar.gz
export STPSF_PATH=$PWD/stpsf-data

# get galsim galaxy catalogs
# Note: ~5 GB each, takes a little while to download.
# Both are needed for tests.  Neither are needed if you are
# exclusively using analytic model galaxies.
galsim_download_cosmos -s 23.5
galsim_download_cosmos -s 25.2

The path to the STPSF data files may be found in their documentation.

You may wish to, for example, set up a new python virtual environment before running the above, or choose a different directory for STPSF’s data files.