NIRCam — the Near-InfraRed Camera

Webb’s NIRCam is the observatory’s primary camera, and will simultaneously image the cosmos in two different infrared ranges. Taking advantage of Webb’s exquisite image quality and large primary mirror, the instrument will acquire some of the deepest (i.e. farthest away) near-infrared images ever obtained, detecting light from the first stars and galaxies. NIRCam also has coronagraphic and spectroscopic capabilities, which will, for example, be used to characterise exoplanets. NIRCam will also be the primary tool for alignment of the telescope. It was provided by the University of Arizona.

NIRISS — the Near-InfraRed Imager and Slitless Spectrograph

NIRISS is an innovative instrument that will support operations in three observing modes. It has a camera that will be usable in parallel with the NIRCam camera to provide additional imaging capabilities for Webb. It 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 will allow 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 will 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