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Comment: Update for 2024.S11
Table of Contents

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 release of the Pandeia engine is 4.0 (JWST), 3.1 (Roman).



Next Planned Release

The next release of the Pandeia Engine will be for Roman

We will update this page with the list of new items for the next release as they are worked.

Tickets in the upcoming release include:

KeyMissionDescription
JETC-3058JWST, RomanThe "total_exposure_time" in the "information" report dictionary now takes into account the number of on-source dithers.
JETC-4387JWST, RomanA warning will be triggered if the aperture or sky region/annulus is smaller than a pixel.
JETC-4416JWST, RomanThe minimum supported Python version is now 3.9
JETC-3759JWST, RomanThe Pandeia Engine is compatible with numpy 2.0
JETC-4247RomanMA Tables have been updated to the latest version
JETC-4523RomanPSFs have been regenerated with WebbPSF 1.3, WebbPSF Data 1.3, and POPPY 1.1.1
JETC-4526RomanThe number of resultants before saturation is limited to the number of resultants in the specific MA table being used.
JETC-4602JWST, RomanPandeia Engine release versioning has changed, and now uses YYYY.M (by which the 4.0 release would have been 2024.7)

What support is available?

Questions about the Pandeia engine for Webb may be directed to the JWST help desk; for Roman, email help@stsci.edu with Roman and/or WFIRST in the subject line or body. 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 data. This simplifies interpretation of the extracted signal-to-noise ratio (SNR) calculated by the ETC.  

Info
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.