Image and Spectroscopy Simulator

The Space Telescope Image Product Simulator (STIPS) is a tool designed to help the astronomical community prepare for JWST observations. 

NOTE: In order to access STIPS JWST, you will need an STScI SSO Account.


Simulated image using STIPS
Pseudocolor image of the central region of a globular cluster viewed in the Z087, J129, and F184 filters of the WFIRST Wide Field Imager, as simulated using STIPS.

Introduction to STIPS for JWST

The STIPS (Space Telescope Image Product Simulator) software produces simulated imaging data for complex wide-area astronomical scenes, based on:

  • User inputs
  • Instrument models
  • Library catalogues for a range of stellar and/or galactic populations.

It was originally developed for the JWST mission, but now has been extended to include WFIRST functionality as well.

The current JWST version produces images covering the MIRI detector, either one or both NIRCam Long detectors, and either one, four, or all eight NIRCam Short detectors. STIPS includes the most current information about the telescope sensitivity, spectral elements, and detector properties; it uses the PSF model generated by WebbPSF for JWST, and it calls the appropriate Pandeia/JWST ETC modules to compute instrumental throughput and count rates.

STIPS is based on a Python module and a web interface that provides a straightforward way of creating observation simulations. In its current implementation, it runs server-side and allows users to submit simulations and view/retrieve the results. To gain access to the STIPS JWST Server, simply visit the linked webpage.



At the heart of STIPS is a multi-faceted scene generation that allows varying degrees of user control. STIPS can generate a randomized set of stars or (idealized) galaxies based on very concise user specifications, or it can generate point or extended sources based on a detailed input catalogue. In addition, an existing image can be used as background.



The STIPS central module is available as a private STScI github, as is the web server interface. In the future, a standalone desktop interface may also be created.

STIPS User Interface
Block diagram of the STIPS User Interface.


A detailed description of the format of STIPS input source catalogues is available. In addition, STIPS includes assorted documentation on the web server.

Assumptions and Caveats

STIPS is still in continued development. The present implementation is made available to the community as a beta version.

Exact data on JWST's sensitivity is not yet available, and as such STIPS may not reflect on-orbit performance.

STIPS throughputs are derived from and tested against Pandeia. The same source, specified in both STIPS and Pandeia, will differ by less than 15%.

STIPS makes several assumptions:

  • STIPS relies in part on calculations with WebbPSF and Pandeia/JWST ETC. Therefore, the same assumptions and caveats apply as listed for those tools.
  • Field-dependence of the PSF is not currently included in STIPS.
  • The Spectral Energy Distribution (SED) for stars and galaxies are obtained from the Phoenix models and a subset of Bruzual-Charlot models, as described above, and are subject to the same limitations as those models. SEDs for galaxies are assumed constant over their images.
  • Models for possible post-pipeline residuals from flat-fielding, dark-current subtraction, and imperfect cosmic ray correction are approximate guesses that are not unreasonable for the HST WFC3/IR instrument, but which may be different for the JWST instruments.

Future Improvements

Enhancements currently planned in the functionality and fidelity of STIPS include:

  • Field-dependent PSF
  • A more realistic treatment of readout modes and noise estimates
  • Saturation and sub-pixel effects
  • More customizable user input (e.g., per-source SED specification)


Credits, Acknowledgements, and Feedback

STIPS is developed by Brian York, with guidance and contributions from Klaus Pontoppidan, Jason Kalirai, Pey Lian Lim, and Stefano Casertano. STIPS makes use of open source astronomical software developed by Justin Bird, Ahmed Fasih, and Adam Ginsburg.

Users are encouraged to address questions, suggestions, and bug reports to the JWST Help Desk.

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.

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