The ISIM is the heart of the James Webb Space Telescope, what engineers call the main payload. This is the unit that will will house the four main instruments that will detect light from distant stars and galaxies, and planets orbiting other stars. The structure (pictured left) is like a chassis in a car providing support for the engine and other components.
Go behind the scenes of the cryogenic testing of the ISIM structure:
Technical Details about the ISIM:
Integrating four major instruments and numerous subsystems into one payload, the ISIM, is a daunting endeavor. To simplify integration, engineers have divided the ISIM into three regions.
The "region 1" component is the cryogenic instrument
module. This chills the detectors down to 39 K, a necessary first-stage cooling
effort so that the spacecraft's own heat doesn't interfere with the infrared
light (a form of heat) detected from distant cosmic sources. The ISIM/OTE Thermal Management Subsystem provides passive cooling. Other devices will
get the detectors even colder.
The "region 2" component is the ISIM Electronics Compartment, which provides the mounting surfaces and ambient thermally controlled environment for the instrument control electronics.
The "region 3" component,
located within the Spacecraft Bus, is the ISIM Command and Data Handling
subsystem, with integral ISIM flight Software, and the MIRI cryocooler compressor
and control electronics.