Near Infrared Imager and Slitless Spectrograph

The JWST Near Infrared Imager and Slitless Spectrograph (NIRISS) provides observing modes for slitless spectroscopy, high-contrast interferometric imaging, and imaging, over wavelengths between 0.6 and 5.0 μm over a 2.2' x 2.2' FOV. Although NIRISS is packaged with the Fine Guidance Sensor (FGS), the two instruments are functionally independent of each other.

When used in specific combinations, optical elements in the NIRISS pupil and filter wheel enable four observing modes:

  • Wide field slitless spectroscopy (WFSS) over the entire field of view, using one or both of a pair of identical grisms and a selection of blocking filters to isolate specific wavelength intervals between 0.8 and 2.2 μm. The grisms are mounted to disperse light in orthogonal directions on the detector.

  • Single object slitless spectroscopy (SOSS) with a cross-dispersed grism designed to deliver broad wavelength coverage and spectro-photometric stability, optimized for time-series observations (TSOs).
  • Aperture masking interferometry (AMI) through specific filters that is enabled by a mask with seven sub-apertures.
  • Imaging in seven wide- and five medium-band filters that are closely matched to the NIRCam filter set between 0.9 and 5.0 μm.

More about NIRISS

See also ...

External NIRISS links and documents

STScI NIRISS website

CSA NIRISS website



JWST Community Lecture Series - NIRISS Overview (R. Doyon)

Other documents

JWST Pocket Guide

JWST technical documents



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