MIRI

Currently, sci.esa.int is under review and not being updated. For the latest information and news from ESA science missions and scientific results, please visit esa.int . For a comprehensive overview of ESA’s Science Programme and its missions, please refer to science.esa.int . For in-depth technical information aimed at ESA's scientific communities, you may also wish to consult cosmos.esa.int . MIRI is the mid-infrared instrument for the James Webb Space Telescope and provides imaging, coronagraphy and integral field spectroscopy over the 5-28 micron wavelength range. MIRI is one of four instruments being built for JWST. It is being developed as a partnership between Europe and the USA - the main partners are ESA, a consortium of nationally funded European institutes, the Jet Propulsion Laboratory (JPL) and NASA's Goddard Space Flight Center (GSFC). MIRI has capabilities needed for the whole range of JWST science, covering every phase of cosmic history from the high-redshift Universe through the formation of planetary systems to our own Solar System. MIRI (wrapped in its aluminized thermal shield) integrated into the JWST Integrated Science Instrument Module (ISIM). Credit: NASA/Goddard Space Flight Center/Chris Gunn Schematic diagram of the MIRI instrument. Credit: University of Arizona The science goals of JWST require a versatile mid-infrared instrument covering the 5-28.5 μm wavelength range with a wide field of view for imaging through broad and narrow band filters, low resolution spectroscopy from 5-10 μm, moderate resolution spectroscopy with R ~ 3000, and high dynamic range coronography. MIRI is designed to provide all of these functions in a single instrument. The MIRI coronagraphy mode has four coronagraphs operating at wavelengths selected for the optimal study of exoplanets. (The coronagraph filter bands are given in Table 1 of Wright et al., 2008.) The MIRI optical system includes the opto-mechanical system known as the optical bench assembly (OBA); the instrument control electronics (ICE) to drive the mechanisms, read temperature sensors and similar tasks; the focal plane control electronics (FPE) to drive the detectors; and the MIRI flight software which configures and controls the instrument and handles the data flow between the hardware and the JWST Integrated Science Instrument Module (ISIM) flight software. MIRI optical bench assembly and key subsystems. Credit: University of Leicester, UK The instrument has a modular optical design and is an isothermal all-aluminium construction. The sub-assemblies have been designed to be testable in isolation. The optical bench assembly is both supported on, and thermally isolated from, the ISIM structure by a Carbon Fibre Reinforced Plastic (CFRP) hexapod. Isolation from the ISIM thermal environment is provided by custom designed Multi-Layer Insulation (MLI) blankets. Optically, the instrument is divided into two channels - an imager channel, with one detector array and a spectrometer channel, which is further subdivided into long and short-wavelength modules - each having its own detector array. Both the imager and spectrometer channels are fed by common optics from a single pick-off mirror placed close to the JWST's focal plane. A pick-off mirror in front of the JWST's optical telescope assembly focal plane directs the MIRI field-of-view towards the imager. A small fold mirror adjacent to the imager light path picks off the small (up to 8 × 8 arcsec) field-of-view of the spectrometer. A second fold in the spectrometer optical path is used to select either light from the telescope or from the MIRI calibration system. The imager module has a combined field of view for the imager, coronagraph and low-resolution spectrometer modes. Coronagraph masks are placed at a fixed location on one edge of the imager field. The light is collimated and, at the pupil image formed by the collimator, a filter wheel holds the imaging filters, Lyot stops and filters for the coro