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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.

Summary

The JWST Near Infrared Imager and Slitless Spectrograph (NIRISS) has 4 observing modes with unique capabilities for imaging and spectroscopy.

  • Wide field slitless spectroscopy (0.8–2.2μm) over a 2.2' × 2.2' field of view using two identical orthogonal grisms with R = λ/Δλ = 150.
  • Single object slitless spectroscopy (0.6–2.8μm) for bright targets in two cross-dispersed orders using the R = λ/Δλ = 700 grism.
  • Aperture masking interferometry which offers the highest spatial resolution imaging on the 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 ≈ 0.065"/pixel.

 

Table 1. Specific properties of NIRISS observing modes

Observing
mode

Wavelength
coverage (μm)

Field of
view
(arcsec)

Pixel scale
(arcsec/
pixel)

Resolving power
R = \lambda / \Delta\lambda

FWHMComment

Wide field
slitless spectroscopy 
(WFSS)
 

0.8–2.2133 × 1330.065150 @ 1.4 μm
...

Orthogonal dispersion
orientations available

Single object
slitless
spectroscopy
(SOSS)

0.6–2.8

...0.065700 @ 1.4 μm...Subarrays are standard;
full-frame allowed
Aperture masking
interferometry 
(AMI)

2.8–4.8

5.2 × 5.20.065......Subarray is standard;
full-frame allowed
Imaging0.8–5.0133 × 1330.0654–102 pix @3.4  μm

Full-frame standard; only used in parallel mode

 

Near Infrared Imager and Slitless Spectrograph, NIRISS
NIRISS Overview

Last updated

Published November 16, 2016