The NIRSpec and MIRI integral field spectrometers on JWST spatially undersample the PSF delivered by the JWST optics. As a result, the reconstructed data cubes produced by the JWST Science Calibration Pipeline exhibit significant resampling artifacts near unresolved point sources. While these periodic artifacts are not present in aperture-summed spectra, their large amplitudes pose significant challenges for science cases relying on analysis of single-spaxel spectra.

Build 12.3 of the JWST Science Calibration Pipeline (operational on May 26, 2026) introduces an optional method to correct for these artifacts by adding the adaptive_trace_model step into the calwebb_spec3 pipeline. An example of the performance of this new algorithm for NIRSpec IFU observations of a spectrophotometric standard star is shown in Figure 1. This correction is not used by default to produce the data products available in the MAST Archive, as it is unnecessary for extended sources or isolated point sources using standard aperture extraction.

An overview of this algorithm and its use can be found on the Resampling Artifacts page on JDox. An example of how to enable this correction in the JWST Science Calibration Pipeline for offline reductions of data is provided by the latest NIRSpec IFU and MIRI MRS pipeline notebooks. Observers are encouraged to contact the JWST Help Desk with any questions.