Origins of large-scale PFPC ripples

Determine the origins of the large-scale ripples that vary by dither position in JWST MIRI Medium Resolution Spectrometer Point Fixed Pattern Corrections at wavelengths including approximately 5.8, 6.8, 12.3, and 20.2 microns.

Background

The paper decomposes the fixed-pattern noise in JWST MIRI Medium Resolution Spectrometer spectra into contributions from residual fringes, sampling artifacts, flat-field noise, and interpolation artifacts. After applying the pipeline residual-fringe correction, substantial structure remains in the Point Fixed Pattern Corrections (PFPCs).

Among the remaining features are broad, large-scale ripples whose amplitudes or shapes often change with detector dither position. The paper identifies their wavelengths but does not establish their physical or instrumental origin, leaving their characterization and explanation unresolved.

References

Finally, there are large scale ripples that often vary by dither position at a number of wavelengths (e.g., 5.8, 6.8, 12.3, and 20.2~\micron) whose origins are not clear.

— JWST MIRI Medium Resolution Spectrometer Point Fixed Pattern Corrections: Cleaner and Higher Signal-to-Noise Spectra of Point Sources  (2608.13464 - Gordon et al., 13 Aug 2026) in Section 3, “Point Fixed Pattern Corrections”