SiC is an exceptional material whose mecathermal properties allow the manufacture of ultra lightweight but very large instruments: the Astrium mirror, at 3.5 m, will be the largest imaging telescope ever launched, weighing just 350 kg, as opposed to the 1.5 tons required with standard technology.
Under a second contract, Astrium is responsible for the fully integrated payload module, consisting of the cyostat, optical bench, scientific instrument harness, solar array and sun shield, telescope and SVM interface structure, and execution of the satellite assembly, integration and test (AIT) programme.
In order to prevent the instruments' own infrared radiation from drowning out the received signal, they must be cooled inside a cryogenic unit – the cryostat – down to minus 271 degrees Celsius (about two degrees above absolute zero). At this temperature the sensitive science instruments will have the potential to penetrate the unknown areas of the cold, early universe.
The cryostat is the central unit of the payload module and is being built under the leadership of Astrium. The low temperature is achieved using superfluid helium.
For the construction of cryostat, Astrium was able to draw on the experience it gained from Herschel's precursor, the European Infrared Space Observatory (ISO) which was successfully operated from 1996 to 1998.
In the course of the satellite AIT programme Astrium will demonstrate the spacecraft's flight readiness. One particular challenge is that while handling the spacecraft, the cryostat tank is filled with superfluid helium during the entire acceptance test campaign up to launch and flight.
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