Documentation for WebbPSF

WebbPSF is a Python package that computes simulated point spread functions (PSFs) for NASA’s James Webb Space Telescope (JWST) and Nancy Grace Roman Space Telescope. WebbPSF transforms models of telescope and instrument optical state into PSFs, taking into account detector pixel scales, rotations, filter profiles, and point source spectra. It is rather a tool for transforming optical path difference (OPD) maps, created with observatory systems engineering models, into the resulting PSFs as observed with JWST’s or Roman’s instruments.

Sample PSFs for JWST's instruments.

Sample PSFs for JWST’s instrument suite, all on the same angular scale and display stretch.

Sample PSFs for the filters in the Roman WFI.

Sample PSFs for the filters in the Roman WFI.

Contributors: WebbPSF has been developed by Marshall Perrin, Marcio Meléndez, Shannon Osborne, Robel Geda, Brad Sappington, Charles-Philippe Lajoie, Joseph Long, Justin Otor, Jarron Leisenring, Neil Zimmerman, Keira Brooks, and Anand Sivaramakrishnan, with contributions from Alden Jurling, Lauren Chambers, Ewan Douglas, and others.

Getting Started with WebbPSF

See Using WebbPSF.

Quickstart Jupyter Notebook

This documentation is complemented by an Jupyter Notebook format quickstart tutorial. Downloading and running that notebook is a great way to get started using WebbPSF.

Getting Help

For help using or installing webbpsf, you can contact the STScI JWST Help Desk at, category WebbPSF/JWST Telescope.

What’s new in the latest release?


Modeling Roman PSFs

How to cite WebbPSF

In addition to this documentation, WebbPSF is described in the following references. Users of WebbPSF are encouraged to cite one of these.

In particular, the 2012 SPIE paper gives a broad overview, the 2014 SPIE paper presents comparisons to instrument cryotest data, and the Technical Report document describes in more detail the relevant optical physics, explains design decisions and motivation for WebbPSF’s architecture, and presents extensive validation tests demonstrating consistency between WebbPSF and other PSF simulation packages used throughout the JWST project.

Mailing List

If you would like to receive email announcements of future versions, please contact Marshall Perrin, or visit to subscribe yourself to the “” list.