The Focal Plane Modules, Harnesses and Electronics (FPS)
Provided by NASA JPL. This is the system that consists of the detectors and the electrical cables and electronics necessary to operate them. These are the ultra-sensitive eyes of MIRI which produce the data which is then beamed to the ground for the science team to study and turn into images.
The Primary Structure
Consisting of a CFRP Hexapod (provided by the Danish National Space Centre) and an Aluminium alloy structural Deck (provided by the University of Leicester). This subsystem supports all of the others in the correct position relative to one another (accurate to approximately 1/50th of a millimetre), and relative to the telescope. It must be strong and stiff enough to support the 100kg instrument through the vibration of launch, but also thermally isolate the cold instrument from it s warmer surroundings.
The Instrument Control Electronics (ICE)
Provided by CSL, Belgium. This electronics box controls all of the instrument mechanisms and temperature sensors, and provides housekeeping data necessary to operate and monitor the instrument.
The instrument control harnesses
Provided by PSI, Switzerland. These electrical cables connect the room temperature ICE to the cryogenic temperature mechanisms and sensors in the instrument while limiting the amount of heat energy conducted to the cold instrument.
The Thermal Control Hardware (THW)
Provided by RAL, UK. The thermal control hardware consists of the cryogenic multilayer insulation (MLI) blankets which insulate the cold instrument from its warmer environment, plus the thermal straps which link the detectors to the dedicated Cryocooler (provided by Northrop Grummen Space Technology, Redondo Beach, California).
After MIRI has been built here at RAL it has to be tested to make sure it can survive the vibrations of the rocket launch and operate successfully in the cold vacuum of space. These tests require a whole series of dedicated and bespoke test facilities to be built for it. To do this we’ve constructed a specific test facility that will operate inside of our main thermal vacuum chamber. This test facility can be cooled, by a set of mechanical cryo-coolers, down to 40 Kelvin to simulate the environment that the instrument will see once in space. These coolers will also cool MIRI itself down even further to its 6.7K (-266.5ºC) operating temperature.
MIRI operates at this temperature because infra-red radiation is equivalent to heat therefore any objects warmer than 15.5K (-258ºC) in or around the instrument would give off an infra-red glow that could be detected by the instrument and interpreted as a light signal.
In orbit the JWST is required to have all of the primary mirror and all four instrument at a temperature below 40K (MIRI is even colder than this). To get the temperature to be so cold, JWST has a large, many-layered sun shield that is perhaps the most striking feature of its appearance – it is the size of a tennis court!
For more information please contact: RAL Space Enquiries
