NIRISS Observing Modes
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
Observing | Wavelength | Field of | Pixel scale | Resolving power | FWHM | Comment |
---|---|---|---|---|---|---|
0.8–2.2 | 133 × 133 | 0.066"/pixel | 150 @ 1.4 μm | ... | Orthogonal dispersion | |
0.6–2.8 | ... | 0.066"/pixel | 700 @ 1.4 μm | ... | Subarrays are standard; full frame allowed | |
Aperture masking interferometry (AMI) | 2.8–4.8 | 5.2 × 5.2 | 0.066"/pixel | ... | ... | Subarray is standard; full frame allowed |
Imaging | 0.8–5.0 | 133 × 133 | 0.066"/pixel | 4–10 | F380M filter and longer wavelength filters are Nyquist sampled | Full frame standard |