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 1.6.2.
- Get the latest engine release software, installable with pip
- See the installation instructions (or these Webb-specific ones)
- Get the Synphot data files that support certain target spectra manipulations
- Get the required mission-specific items:
| Webb | Roman |
|---|---|
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JWST
JWST users must continue to use v1.6.1; there is no v1.6.2 release for JWST.
Next Planned Release
The next release of the Pandeia Engine will be after JWST launch and commissioning.
In the next release:
New Features:
| Key | Mission | Release note |
|---|---|---|
| JETC-1179 | JWST Roman | New normalization bandpasses: Midcourse Space Experiment (msx) bands: a, b1, b2, c, d, e |
| JETC-1149 | JWST Roman | New: Additional filter bandpasses are available: 2mass j, h, ks; wise w1, w2, w3, w4; gaia g (EDR3) |
Backwards Incompatible:
| Key | Mission | Release note |
|---|---|---|
| JETC-1750 | JWST Roman | Refactor: The DetectorSignal, CombinedSignal, and CalculationConfig classes are now defined in signal.py; the DetectorNoise class is defined in noise.py; etc3d.py now contains only calculate_sn, calculate_contrast, and calculate_time. |
| JETC-418 | JWST | Creating a calculation with pandeia.engine.calc_utils.build_default_calc() will now produce an identical calculation (except for Background flux) to the webapp. The API for describing the default calculations has changed to make that possible. |
| JETC-1837 | JWST Roman | The det_pars section of the configuration file is now 'detector', and has entries for the distinct different types of detector (for instance, NIRCam sw and lw; where sw corresponds to NRCA1-A4, and lw to NRCA5). The 'aperture_config' configuration now contains a detector keyword to indicate which detector each aperture belongs to. |
| JETC-1663 | JWST Roman | Refactor: ExposureSpec now contains only the functions necessary to compute MultiAccum exposure times; it has child classes for H2RG, H4RG, and SiAs. The noise-computing methods previously in ExposureSpec have been moved to a new class, Detector (with child classes for H2RG, H4RG, and SiAs detectors) along with the calc_cr_loss method previously in DetectorNoise. The Detector instance for a calculation can be accessed from a DetectorSignal as DetectorSignal.the_detector; exposure parameters in ExposureSpec can now be accessed from DetectorSignal as DetectorSignal.the_detector.exposure_spec The Roman WFI is now properly identified as an H4RG detector, rather than an H2RG. At present, H4RG is identical to H2RG. |
Reference Updates:
| Key | Mission | Release note |
|---|---|---|
| JETC-1145 | JWST Roman | Reference Update: The Spitzer IRAC bandpasses have been updated with new reference values. All normalization bandpasses now require the TRDS supplementary data. |
| JETC-1700 | JWST Roman | Update: New exposure time calculation equations: A reset time has been removed from the saturation calculations, and exposures will take longer to saturate. |
| JETC-1821 | JWST Roman | Answers using analytic spectra may change at below the 1% level, because the exact wavelength values used have changed. |
Other Changes:
| Key | Mission | Release note |
|---|---|---|
| JETC-1758 | Roman | Fix: A bug that affected the brightness of the Roman F062, F087, and F158 filters has been corrected. |
| JETC-1866 | JWST Roman | Bug: A bug in wavelength interpolation that could cause abnormally bright fluxes has been fixed. This primarily affected the Roman WFI f062 filter |
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.
