Before reading further, if you do not wish to install PandExo,there is an online version of the code here at STScI’s ExoCTK.

Pre-installation Data Download

PandExo requires downloading three folders: 1) JWST instrument info, 2) stellar SEDs, and 3) normalization bandasses. It also requires setting up two environment variables.

JWST Reference Data

JWST Reference data has been updated to 3.0!


Reference data must match the software version. For example Pandeia reference data 3.0 should match Pandeia verions software release 3.0, and that should match PandExo 3.0)

The new reference data is located here for v3p0. More information on pandeia installation can be found here

After you have downloaded the reference data, create environment variable (more resources on how to create environment variables are located here).

You can verify your installation by opening up a terminal with access to the conda installation, and type

python -c "import pandeia.engine; pandeia.engine.pandeia_version()"

If properly installed and configured, it should show the refdata version and synphot data directory, like this:

Pandeia Engine version:  3.0
Pandeia RefData version:  3.0
Pysynphot Data:  /your/data/directory/synphot
echo 'export pandeia_refdata="$USRDIR/pandeia_data"' >>~/.bash_profile

Stellar SEDs

PandExo uses Pysynphot’s Phoenix stellar atlas, which can be downloaded here.

Once untarred, the files will produce a directory tree of grp/redcat/trds. The pandeia.engine uses the contents of the trds directory.

Environment variable: $PYSYN_CDBS must point to the trds directory (NOT grp)

Create your environment variable:

echo 'export PYSYN_CDBS="$USRDIR/grp/redcat/trds"' >>~/.bash_profile

Normalization Files

New to PandExo >2.0, users now have to download the master table of all pysynphot throughput tables.

Download the file here

Once untarred this will also produce a directory tree of grp/redcat/trds with two folders comp and mtab. Place these folders into the folder you created above $USRDIR/grp/redcat/trds

>> ls $USRDIR/grp/redcat/trds
comp grid mtab

Now you should have three folders in your trds folder.

Fortney+ 20210 Planet Grid (Optional)

A user may want to install a grid of atmospheric models to simulate planet atmospheres. Some of the example notebooks use an atmospheric model grid. This grid can be obtained from:

After downloading the Fortney files, create an environmental variable to point to them.

echo 'export FORTGRID_DIR="$USRDIR/fortney_models.db"' >>~/.bash_profile

Installation with Pip or Git

Install with pip:

pip install pandexo.engine

OR Download PandExo’s repository via Github. The Github also has helpful notebooks for getting started!

git clone --recursive
cd pandexo
pip install .

Final Test for Success

There is a in the github. Test that you’re code is working:

Starting TEST run
Running Single Case for: NIRSpec G140H
Optimization Reqested: Computing Duty Cycle
Finished Duty Cycle Calc
Starting Out of Transit Simulation
End out of Transit
Starting In Transit Simulation
End In Transit

Troubleshooting-Common Errors

The Importance of Upgrading PandExo

It is crucial that your verison of PandExo is up to date. There were many critical updates in the reference files after launch, and as a result of the commissioning work. Updating PandExo requires three crucial steps:

1) Verify pandexo.engine is Current

pip install pandexo.engine --upgrade

2) Verify pandeia.engine version compatible

Currently PandExo requires pandeia.engine==2.0

pip install pandeia.engine==2.0

3) Grab pandeia.engine data 2.0

The reference data is located here for v2p0.