The JWST Near Infrared Imager and Slitless Spectrograph (NIRISS) instrumentation includes internal optical components, filters, grisms, and an aperture mask to support its four observing modes.
Overview of NIRISS instrument components
- Transfer optics:
- a pick-off mirror (POM), which also includes the focus mechanism,
- a three-mirror assembly (TMA) to collimate the incoming beam, and
- a camera TMA to focus light on the detector.
- Pupil and filter wheels as a dual-wheel assembly:
- filters—12 bandpass filters (seven wideband and five medium-band) distributed equally between the pupil and filter wheel;
- in the filter wheel that operate between 0.8 and 2.2 μm with R ≈ 150. These grisms are identical but oriented to disperse in orthogonal directions on the detector;
- GR700XD—a grism in the pupil wheel that operates between 0.6 and 2.8 μm with R ≈ 700, which is optimized for applications that require high spectro-photometric precision; and
- a non-redundant aperture mask (NRM) in the pupil wheel that enables high spatial resolution imaging with medium contrast.
- Detector: a single Hawaii 2RG sensor chip array with 2048 × 2048 pixels. Each pixel is 18 × 18 μm and provides a plate scale of 0.0654 × 0.0658 "/pixel.
Science use cases
Exposure Time Calculator
Astronomer's Proposal Tool