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 dependencies.
The latest Pandeia engine release is 4.0 (JWST 4.0), 2024.12 (Roman R2024.12).
- 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:
| Webb | Roman |
|---|---|
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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 will be in Spring 2025, for JWST.
| Ticket | Mission | Release Note | |
|---|---|---|---|
| JETC-4482 | JWST, Roman | API strictness has been tightened; it is no longer possible to run a calculation with a normalization that requires a bandpass without providing a bandpass. Malformed input dictionaries that result in default values being used are now elevated as Python warnings, in addition to the result["warnings"] dictionary in the result. | |
| JETC-4820 | JWST, Roman | Engine scripters can now change the random seed value used to add noise to the 2D detector image. In the input dictionary's "calculation" sub-dictionary, under "effects", "random_seed" can be set to None for the current fixed behavior, to any positive 32-bit unsigned integer to seed the random number generator with that value, or to a negative number to have an unseeded random value that changes every time. | |
| JETC-4815 | JWST, Roman | It is no longer necessary (or recommended) to download the JWST data to normalize by JWST bandpasses It is no longer necessary (or recommended) to download the Roman data to normalize by Roman bandpasses | |
| JETC-4766 | JWST | The available readout pattern choices for the NIRCam sw_tsgrism and lw_tsgrism modes have been changed to include dhs3 through dhs7 |
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.
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.
