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 2.0.
- 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 the Input API documentation
- View the Output API documentation
Next Planned Release
The next release of the Pandeia Engine is expected to be for the Cycle 3 call for proposals.
We will update this page with the list of new items for the next release as they are worked.
Issue | Mission | Release Note |
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JETC-3064 | JWST | The aperture used by NIRSpec mos_ver, mos_conf, and target_acq (when used for MSATA) is now called shutter__ta. |
JETC-3129 | JWST Roman | New optional keyword for perform_calculation(): "validate" switches on (True) and off (False) the availability of various intermediate validation products. Depending on the mode and size of the input spectrum, setting validate=False may significantly reduce memory usage, though it may break third party applications that use or reuse the Engine. Setting validate=True will restore the previous default behavior. |
JETC-3221 | JWST Roman | Adding an "is_aperture_ee" = True keyword to an imagingapphot strategy will make the engine interpret "aperture_size" as a percentage of Encircled Energy. Values between 10 and 95 are generally valid for imaging modes, though this will vary depending on the size and shape of the PSF. |
JETC-3099 | JWST Roman | Setting the webapp=True keyword (the default) will no longer load configuration defaults. Malformed calculation inputs will fail, rather than silently having defaults applied. Also, the phoenix spectrum API has changed: if teff is present, Pandeia will look for teff, log_g, and metallicity keywords; if not, it will look for "key". |
JETC-3130 | JWST Roman | *_resel products (which were identical to non-resel products) have been removed from the Report class and its output dictionaries for all future calculations. |
JETC-3187 | JWST Roman | JWST and Roman will no longer issue filter leak warnings. |
JETC-3100 | JWST Roman | Pixels can now be used as the strategy unit; they apply to the size of the extraction aperture and annulus but not any spatial offset (target_xy, shutter_offset, and dithers are always arcseconds). Pixel extraction units are currently only allowed for SpecApPhot |
JETC-2808 | JWST | "full" aperture is now available for miri coronagraphy and miri coronagraphic target_acq |
JETC-3418 | JWST Roman | Pandeia now supports all the spectral templates the HST ETC did. New SED classes: bt_settl, bz77, ck04models, pickles, nonstellar |
JETC-3016 | JWST | The f150w2 filter is now available for NIRCam sw_ts calculations with the clear and wlp8 pupils. |
JETC-4 | JWST | Although the names of the IFU strategies have changed in the Web UI, the names have not changed in the Engine. "IFU On-Target 2-Point Nod" is still "ifunodinscene", and "IFU On-Target and Off-Target Pointing" is still "ifunodoffscene". The new "IFU Aperture Photometry" option is called "ifuapphot" in the Engine. |
JETC-2531 | JWST Roman | The warnings dict warnings now uniformly have actual names as keys. Some cases of duplicate warnings have been resolved. |
JETC-3188 | JWST | The new "total dithers" entry in the Web UI is available as the nexp property in configuration["detector"]["nexp"]. Its functionality has not changed. |
JETC-29 | JWST Roman | The imagingapphot and ifuapphot strategies now support specifying the extraction aperture (but not sky annuli) in percentages of encircled energy. A new required keyword in the strategy dict, "is_aperture_ee", must be set to True for the contents of "aperture_size" to be interpreted as an encircled energy percentage. All imagingapphot and ifuapphot calcs created with build_default_calc() will include the new "is_aperture_ee" keyword. It defaults to False for imagingapphot for JWST and Roman, and to True for ifuapphot. |
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.
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.