Row and column artifacts in JWST MIRI's Si:As blocked impurity band detectors

Abstract

The JWST Mid-Infrared Instrument (MIRI) detector arrays are Si:As blocked impurity band devices, direct descendants of the Spitzer/IRAC long wavelength arrays. Similarly to the IRAC row-column effect, analysis of flight-like MIRI detector data has shown that columns and rows in which source signals are located can suffer from pull up (brightness increase) or pull down (brightness decrease) in the flux image. Here we present results from the JPL MIRI detector characterisation campaigns dedicated to understanding this row-column effect as well as the first results showing the effect in the flight detectors for MIRI. We show the effect is flux dependent and confirm that the effect manifests differently for rows versus columns. We discuss the origin of the flux offset, which is related to a change in the signal output in time that distorts the input ramp as a function of the saturation level of illuminated pixels. We conclude by discussing the row-column effect in the context of different MIRI instrument modes and present preliminary proposals to mitigate and/or correct the effect in MIRI data. © 2022 SPIE.