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.

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.

IssueMissionRelease Note

The aperture used by NIRSpec mos_ver, mos_conf, and target_acq (when used for MSATA) is now called shutter__ta.

JETC-3129JWST 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-3221JWST RomanAdding 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-3099JWST RomanSetting 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-3130JWST Roman*_resel products (which were identical to non-resel products) have been removed from the Report class and its output dictionaries. 

JWST Roman

JWST and Roman will no longer issue filter leak warnings.

What support is available?

Questions about the Pandeia engine for Webb may be directed to the JWST help desk; for Roman, email 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.  

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.

  • No labels