PSF Simulation Tool

Simulated point spread functions for JWST can be produced using the WebbPSF package. PSFs are computed based on a supplied library of optical path difference (OPD) files consistent with the JWST optical error budget, including wavefront errors in the Optical Telescope Element (OTE) and in each instrument. Ten independent statistical realizations are provided for each. Using these, WebbPSF computes observed PSFs assuming Fraunhofer (far-field) propagation.

WebbPSF provides:

Screenshot from WebbPSF Tool

  • Support for all of JWST's instruments.
  • PSF simulations for direct imaging and coronagraphic modes, and for non-redundant aperture masking mode on NIRISS.
  • Improved instrument properties such as normalized filter throughputs for NIRCam, NIRspec, and NIRISS, and detector pixel scales and orientations for all instruments.
  • Arbitrary oversampling of output PSFs
  • Quick calculations using optimized matrix Fourier transforms, the fast semi-analytic coronagraphy algorithm, and the FFTW3 library (optional).
  • Built-in functions for PSF evaluation such as producing radial profile plots, measuring encircled energy curves, FWHMs, etc.
  • A greatly improved graphical user interface.
  • An easy-to-use scripting interface for integration with other tools.

Limitations: The spectroscopy modes of NIRSpec and MIRI are not yet supported. Detector imperfections are likewise not included. The current OPD models do not support field-dependent wavefront error across the instrument FOVs. Future versions of WebbPSF and related software packages will address these issues.

You can access a pre-made set of simulated point spread functions for JWST, generated with WebbPSF and using JWST's predicted optical performance.


Obtaining WebbPSF

WebbPSF is written in Python and should run on any platform that supports numpy/scipy/matplotlib. About 900 MB disk space is required, mostly for the simulated OPD map library.

Installation Instructions       Release Notes


Software Documentation

Additional documentation and examples for WebbPSF are also available.

WebbPSF Documentation       Quick Start       Scripting Interface Examples


WebbPSF Feedback

WebbPSF was developed by Marshall Perrin, with contributions from other members of the Telescopes group at STScI. Please send any comments or suggestions to the JWST Help Desk.


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For technical assistance, please contact the JWST Help Desk.


The NASA James Webb Space Telescope, developed in partnership with ESA and CSA, is operated by AURA’s Space Telescope Science Institute.