Thermal Design of the Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope

The Mid-Infrared Instrument (MIRI) is one of four scientific instruments on the James Webb Space Telescope (JWST) observatory, scheduled for launch in 2013. It will provide unique capabilities to probe the distant or deeply dust-enshrouded regions of the Universe, investigating the history of star formation both near and far.

The MIRI is the coldest instrument on the observatory. Its thermal design is driven by requirements to cool its Optics Module (OM) to below 15.5 K and detectors within this to below 6.7 K. The MIRI OM is accommodated within the JWST Integrated Science Instrument Module (ISIM) which is cooled passively to between 32 and 40 K. The instrument temperatures are achieved by a combination of thermal isolation of the OM from the ISIM supplemented with active cooling of the OM by a dedicated cryocooler.

This paper describes the detailed thermal design of the MIRI OM and the verification activities that have been undertaken by dedicated thermal tests on representative subsystem and instrument models.