NIRISS — the Near-InfraRed Imager and Slitless Spectrograph

NIRISS is an innovative instrument that supports operations in three observing modes.

NIRISS has a camera that can be used in parallel with the NIRCam camera to provide additional imaging capabilities for Webb. It also features a slitless spectrograph, where all the light falling on the camera will be dispersed into its spectrum. Unlike in an ordinary spectrograph, the light source in a slitless spectrograph is not a narrow slit. NIRISS also offers a spectroscopic mode that is specially designed for exoplanet characterisation using transit spectroscopy, a technique that allows Webb to study the chemical composition of an exoplanet’s atmosphere when it passes in front of its host star.

The instrument’s accompanying fine guidance sensor allows Webb to remain steadily locked on or pointed, with very high precision, at a specific celestial target – even a moving one. This high precision means that it can obtain high-resolution images and spectra.

With NIRISS, astronomers study whether or not the spectra of distant planets show lines characteristic of molecules such as water, carbon dioxide, methane and oxygen in their atmospheres – key to the search for life-friendly conditions. NIRISS was provided by the Canadian Space Agency.

View the collection of images and data taken by the NIRISS instrument here.