Thermal Design Overview
One of the key design drives for the MIRI is the requirement to cool the Optics Module to below the ISIM temperature during operations. This is achieved through thermal isolation of the OM from the ISIM, and the provision of a MIRI-dedicated cooling system, a cryo cooler (using liquid Helium) which is in region 3 of JWST. The Cryostat and OM are separate units which will be installed approximately 1.3 metres apart on the ISIM structure.
MLI Blanket
Isolation of the MIRI OM from the radiative environment of the ISIM is achieved through the use of multi-layer insulation blankets. At operational temperatures, conductance is a significant method of heat transfer through MLI. As a result the performance will be highly dependant on the geometry and resulting edge and corner effects. In order to minimize heat transfer it is therefore essential that a simple geometry is implemented, the area is minimised and an effective method of conduective isolation is implemented between the radiation shields.
