Data Artifacts and Features

Different kinds of artifacts have been identified in data files from pre-launch testing as well as on-orbit operations. This article points you to the current support information to understand these effects.

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See also: A separate set of articles under JWST Calibration Pipeline Caveats

Ground testing and in-flight operations have identified a number of features that can appear in JWST data. The frequency with which each artifact appears depends on the instrument, observing mode, and random external factors such as the possible location and brightness of a spoiler star that may cause a glint of scattered light. Some types of artifacts can appear in multiple instruments while others are specific to a given instrument. The articles listed below provide access to more detailed information about each artifact type.

This article will be updated as new information becomes available.

Multi-instrument artifacts


Snowballs are attributed to particularly prominent cosmic ray impacts on the near IR detectors in various JWST instruments. A saturated core is surrounded by a multicomponent halo effect, as described in the article Snowball Artifact. Proper dithering may help minimize the impacts.

Scattered light

Testing on the ground and during commissioning has uncovered a number of ways that unwanted light can find its way onto the detectors as described in the Scattered Light Features article.

Instrument-specific features and caveats 

Each science instrument's documentation contains a "Features and Caveats" article for their particular instrument that provides information about which users should be aware. The full list can be found in the Instrument-Specific Features and Caveats article.

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