MIRI, the Mid-Infrared Instrument, observes mid-infrared wavelengths on the James Webb Space Telescope. It combines a camera with spectrographs and covers approximately 5 to 28 micrometres, the longest-wavelength range among Webb’s four science instruments.
Mid-infrared observations can reveal cool dust, molecules, young stars hidden inside dense clouds, and thermal emission from planets and other objects. MIRI is also used to study galaxies, circumstellar disks, and exoplanets, including through coronagraphic observations that block some of a star’s light.
Because mid-infrared detectors are especially sensitive to heat, MIRI must be colder than Webb’s other instruments. It uses a dedicated cryocooler that brings the instrument down to roughly 7 kelvins during operations. The telescope’s large sunshield provides passive cooling, but that alone is not sufficient for MIRI’s longest wavelengths.
The other listed names are different Webb instruments or components. NIRCam is the Near Infrared Camera, NIRSpec is the Near Infrared Spectrograph, and FGS is the Fine Guidance Sensor. MIRI’s name directly identifies its mid-infrared mission.