Instruments
The Integrated Science Instrument Module, or ISIM, is the heart of the JWST, what engineers call the main payload. This is the unit that will house the four main JWST instruments. The ISIM is like a chassis in a car providing support for the engine and other components.
The four instruments that attach to the ISIM are:
Mid-Infrared Instrument, or
MIRI - provided by the European Consortium with the European Space Agency
(ESA), and by the NASA Jet Propulsion Laboratory (JPL)
Near-Infrared Camera, or NIRCam - provided by the University of Arizona
Near-Infrared Spectrograph, or NIRSpec - provided by ESA
Fine Guidance Sensor, or FGS - provided by the Canadian Space Agency. The FGS contains a dedicated Guider and a Tunable Filter Camera.
Goddard Space Flight Center provides the ISIM infrastructure subsystems required for operation of these instruments. These include the ISIM Structure Subsystem; ISIM Thermal Control Subsystem; ISIM Control and Data Handling Subsystem; ISIM Flight Software; and ISIM Harness Assemblies.
As you can imagine, 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.
