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The Pandeia engine of the Exposure Time Calculator is released to the community to support users who wish to script their calculations, run more extensive parameter space studies, and have more direct control of their scenes. We also recognize that the community has developed more extensive wrappers and public tools that depend on the Pandeia engine.
This page is intended to facilitate communication with developers in the community with Pandeia engine Engine dependencies.
The latest Pandeia engine Engine release is is 2026.27 (JWST 5.1Cycle 6), 2026.1 (Roman R2026.1, Cycle 1 GI).
- Get the latest engine release software, installable with pip
- See the installation instructions
- Get the Synphot data files that support certain target spectra manipulations
- Get the required mission-specific items:
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- View usage instructions (Webb-specific)
- View usage instructions (Roman-specific)
- View the Input API documentation
- View the Output API documentation
Next Planned Release
The next planned release is in Summer 2026, for JWST Cycle 62027
| Key | Mission | Engine Release Note |
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| JETC-6016 | JWST | The Uranus and Neptune template spectra have been updated |
| JETC-468 | JWST | All NIRISS soss calculations now contain background contributions from orders 0, 1, 2, and 3. |
| JETC-6464 | JWST | MIRI target_acq with coronagraphic filters now contain the correct filter transmissions |
| JETC-6396 | JWST | Frame time updated for NIRISS SOSS sub17stripe_soss.|
| JETC- | JWST | PSFs for all missions have been regenerated with an updated JWST wavefront file, and STPSF 2.2.0 |
| JETC-6369 | JWST, Roman | Encircled Energy behavior has been improved. |
| JETC-6274 | JWST | New multistripe specific exposure times. |
| JETC-5309 | JWST | New NIRcam superstripe subarrays, available for sw_imaging, lw_imaging, sw_ts, lw_ts: fullms510 fullms120 fullms024 fullms008 sub64ms02p sub64sp08p sub64sp32p |
| JETC-6126 | JWST | Multistripe added for NIRSpec BOTS Prism. New subarrays are: S256M2_PRM S128M4_PRM S64M8_PRM S32M16_PRM These new subarrays are only available for nirspec bots with the prism disperser. |
| JETC-5256 | JWST | The fastgrpavg8 readout pattern is now available for all MIRI modes where slowr1 was also available. The number of reset frames for the fastgrpavg* readout patterns is now 1. |
| JETC-6198 | JWST | Added slitlessprism_ip and slitlessprism_ips subarrays to MIRI Imaging. |
| JETC-6015 | JWST, Roman | The engine configuration toggle keywords have changed: "crs" is now "cosmic_rays_on" "dark" is now "dark_current_on" "excess" is now "readnoise_excess_additive_on" "ffnoise" is now "flat_field_noise_on" "readnoise" is now "readnoise_on" "scatter" is now "scattering_on" The old toggle names are now deprecated and will be removed in a future update. There are no changes to the behavior of these toggles; if set to None they use the default settings chosen by our instrument specialists. |
| JETC-6125 | JWST, Roman | Encircled Energy accuracy has been improved. |
What support is available?
Questions about the Pandeia engine for Webb may be directed to the JWST help desk; for Roman, the Roman help desk. However, due to the complexity of the engine, support will be limited and response times may be longer than for other tools.
We welcome comments and feature requests, and these will be considered along with other ETC work.
What is the Pandeia Engine?
The Pandeia engine uses a pixel-based 3-dimensional approach to perform calculations on small (typically a few arcseconds) 2-dimensional user-created astronomical scenes. It models both the spatial and the wavelength dimensions, using realistic point spread functions (produced using WebbPSF) for each instrument mode. It natively handles correlated read noise, inter-pixel capacitance, and saturation. Since the signal and noise are modeled for individual detector pixels, the ETC is able to replicate many of the steps that observers will perform when calibrating and reducing their JWST or Roman data. This simplifies interpretation of the extracted signal-to-noise ratio (SNR) calculated by the ETC.
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| While the Pandeia engine includes many effects not typically included in other ETCs, it is not an observation simulator. It does not simulate the full detector, nor does it include 2-dimensional effects such as distortion. |
Details on the algorithms used to compute signal and noise on the detector and the strategies used to compute the extracted products can be found in Pontoppidan et al. 2016.
