The JWST Exposure Time Calculator (ETC) version 4.0 is now live. This release includes useful new capabilities and features:

• Extraction and background apertures are now plotted in all output images for the majority of observing modes and can be toggled on and off by clicking on the corresponding entry in the legend.
• Support is now provided for single-group integrations for all near-infrared instruments (NIRCam, NIRISS, and NIRSpec).
• The NIRCam Short-wavelength Grism Time Series mode is now available in the ETC.
• The existing NIRCam Long-wavelength Grism Time Series mode was updated to include the options available when it is used in conjunction with the new Short-wavelength Grism Time Series mode.
• A new extraction strategy is available for the NIRSpec IFU, the On-Target N-Point Nod, which corresponds to the 4-POINT-NOD in APT.
• The SLITLESSPRISM subarray is now available in MIRI imaging to support LRS Slitless verification imaging calculations.
• The point spread functions (PSFs) for all instruments and modes were updated using the latest version of WebbPSF.
• The thermal background model was updated based on on-sky observations. This primarily affects MIRI calculations, but also has small effects on near-infrared calculations longward of ~3 microns.
• The MIRI imaging and MRS throughputs were updated to account for the count-rate loss. The MRS now provides results baselined to June 30, 2026 (the final day of Cycle 4), and the imaging calculations are baselined to the JWST end-of-mission, due to the negligible rate of change in sensitivity for the imager.
• Saturation limits were updated for the NIRISS AMI, imaging, and WFSS modes.
• The NIRCam filter throughputs were updated based on on-sky observations.

See the release notes for details, and be sure to review the known issues for this release. Instructions for downloading the new version of the Pandeia engine and the associated data are found in the JWST Documentation and the Pandeia Engine News page.

If you have any questions about this release, please let us know via the JWST Help Desk.