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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 dependencies.
The latest release of the Pandeia engine is 1.5.2 3.2 (JWST), 3.1 (Roman).
- Get the latest engine release software, installable with pip
- See the installation instructions (or these Webb-specific ones)
- Get the optional 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 the Input API documentation
- View the Output API documentation
Next Planned Release
The next planned release is 1.6, expected in March 2021.
The following changes are expected to be included:
release of the Pandeia Engine will be for the JWST Cycle 4 call for proposals.
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:
| Key | Mission | Description |
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| JETC-2897 | JWST | The NIRSpec "msa" mode ("mos" in the webapp) has been renamed to "mos", internally. The NIRCam "ssgrism" mode ("lw_tsgrism" in the webapp) has been renamed to "lw_tsgrism". Though old input dictionaries will continue to function until ETC 5.0, anything using build_default_calc() will need to update to use the new names. |
| JETC-3058 | JWST, Roman | The "total_exposure_time" in the "information" report dictionary now takes into account the number of on-source dithers. |
| JETC-3056 | JWST | Duty cycle is now an accurate representation of the fraction of exposure time spent collecting photons. |
| JETC-4374 | JWST | NIRCam reference data has been updated based on recent calibrations |
| JETC-4387 | JWST, Roman | A warning will be triggered if the aperture or sky region/annulus is smaller than a pixel. |
| JETC-330 | JWST | New mode: nircam sw_tsgrism. This is the Dispersed Hartmann Sensor (DHS) spectroscopic mode. There is one available disperser: dhs0; and four apertures corresponding to the number of DHS stripes coadded into the final image: dhs0spec2 uses stripes 4 and 7 and must be paired with subarray sub40stripe1_dhs, dhs0spec4 uses stripes 2, 4, 7, and 8 and must be paired with subarray sub80stripe2_dhs; dhs0spec8 uses stripes 2, 3, 4, 5, 7, 8, 9, 10 and must be paired with either subarray sub160stripe4_dhs or sub256stripe4_dhs. For estimations of saturation, use the dhs0bright aperture (stripe 7) and any of the above subarrays. All wide-band sw filters can be used with sw_tsgrism. lw_tsgrism now allows the new DHS subarrays (sub40stripe1_dhs, sub80stripe2_dhs, sub160stripe4_dhs, sub256stripe4_dhs) for observations meant to be taken in parallel with sw_tsgrism. |
| JETC-4273 | JWST | Reference data files for MIRI, NIRCam, NIRISS, and NIRSpec have been updated to the latest on-orbit measurements. |
| JETC-4162 | JWST | nirspec ifu now supports the 4 point nod strategy. With this new strategy, "ifunpointnod", the "strategy" "dither" entry of the input dictionary is now a keyword (with "nod4" as the only option) rather than a list of dither positions. However, only nod 1 of the 4-point nod is actually visible in the output 2D images. |
| JETC-4278 | JWST | The entire PSF library has been regenerated with WebbPSF 1.3 and POPPY 1.1.1, with the latest distortion and other detector effects included. |
| JETC-4387 | JWST, Roman | A warning will be triggered if the aperture or sky region/annulus is smaller than a pixel. |
| JETC-4416 | JWST, Roman | The minimum supported Python version is now 3.9 |
| JETC-3759 | JWST, Roman | The Pandeia Engine is compatible with numpy 2.0 |
Version 4 will be released for JWST only.
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.
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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.
