New empirical sky background images for the NIRISS Wide-Field Slitless Spectroscopy (WFSS) mode are now available. These images were created from carefully vetted calibration and science exposures and significantly improve the subtraction of the sky background in WFSS data. 

The new backgrounds correct the strong artifacts affecting the previous WFSS background models (up to 5% of the sky brightness).  Now, the median background residuals on science data reach well below 1% of the sky brightness. They are available for all wide-band filters crossed with both orthogonal grisms.

The backgrounds are automatically used in the spec2 pipeline processing of NIRISS WFSS data with the latest JWST Pipeline Build 12.0 (version 1.19.0). Read the full paper to get more details on the methodology used to create the WFSS backgrounds and their quality. Users who have questions or are seeking more information are encouraged to reach out to the NIRISS team via the JWST Help Desk.