Last Updated Mar 24, 2017
The JWST Near Infrared Imager and Slitless Spectrograph (NIRISS) provides observing modes for grism spectroscopy, high-contrast interferometric imaging, and imaging, over wavelengths between 0.6 and 5.0 μm. 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 4 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 spectrophotometric stability.
- Aperture masking interferometry (AMI) through specific filters that is enabled by a mask with 7 sub-apertures.
- Imaging in 7 wide- and 5 medium-band filters that are closely matched to the NIRCam filter set between 0.9 and 5.0 μm.
External NIRISS links and documents