JWST's Near Infrared Imager and Slitless Spectrograph (NIRISS) has observing modes for imaging, low-resolution wide field grism spectroscopy, single object grism spectroscopy, and high spatial resolution imaging using aperture masking interferometry.

NIRISS has 4 observing modes with unique capabilities for imaging and spectroscopy that correspond to templates in the Astronomer's Proposal Tool (APT):

• Wide field slitless spectroscopy (0.8–2.2μm) over a 2.2' × 2.2' field of view using 2 identical orthogonal grisms with R = λ/Δλ = 150;
• Single object slitless spectroscopy (0.6–2.8μm) for bright targets in 2 cross-dispersed orders using the R = λ/Δλ = 700 grism, optimized for time-series observations (TSOs);
• Aperture masking interferometry which offers the highest spatial resolution imaging on JWST, using a non-redundant mask (NRM), reaching a contrast of 10^-4  for separations of 70–400 mas;
• Imaging (0.8–5.0μm) over a 2.2' × 2.2' field of view with pixel scale ~0.066"/pixel.

Table 1. Details about the NIRISS observing modes