JWST NIRISS operations include telescope pointing maneuvers (dithers and target acquisitions) using targetable areas called apertures.

NIRISS operations are observatory-level capabilities applied for science observations with NIRISS. These operations include pointing maneuvers such as dithers and target acquisitions.

• Dithers are performed between exposures to improve sky coverage and image quality. 
  • Dithers are required for the wide field slitless spectroscopy (WFSS) and imaging modes to mitigate the poor sampling of the point spread function and remove detector artifacts. 
  • Dithering is also supported for the aperture masking interferometry (AMI) mode, where the 5-point subpixel dither pattern is recommended. 
  • Dithering is not supported for the single object slitless spectroscopy (SOSS) mode.
• Target acquisition (TA) is required when using a subarray in SOSS and AMI observing modes, and it is strongly encouraged in those modes even when using full frame readout. TA is not implemented for WFSS and imaging.
• All targeting is performed using apertures, which define the target's position and extent in the field of view of the detector. 
• Mosaics can be used in the WFSS and imaging modes to cover an area larger than the 2.2' x 2.2' NIRISS field of view.

Detector operations such as readout patterns are covered in the articles under NIRISS detector.

The full list of NIRISS operations articles: