Herschel's heart and brain mated
Herschel, the European Space Agency's (ESA's) infrared space observatory was unveiled yesterday, following the linking of its 'heart' and 'brain' modules. The Herschel satellite is ESA's latest mission, designed to study the formation of galaxies and stars. Due for launch in 2008, Herschel will carry the largest telescope ever flown in space, giving astronomers their best view yet of the 'cold' and most distant objects in the universe. It will collect very long infrared wavelengths, peeking into star-forming regions, galactic centres and planetary systems. In order to achieve its objectives and to detect the faint radiation coming from the coolest objects in the cosmos, which are otherwise 'invisible', Herschel's detectors must operate at very low and stable temperatures. The spacecraft's brain - or its payload module - therefore hosts a cryostat, a cryogenic module inside which the cold components of the scientific instruments are mounted. Inside the cryostat the sensitive instrument detectors are cooled down to about -273°C (0.3 degrees above absolute zero). This low temperature is achieved using superfluid helium (at about -271°C) and an additional cooling stage inside the focal plane units. The service module is the spacecraft's heart, which keeps the spacecraft going by caring for all its vital functions. It also carries the 'warm' components of the instruments - those that do not require cooling with the cryostat. To have achieved these particular features alone is already a remarkable accomplishment for European industry and science. Herschel will be launched into space on an Ariane 5 ECA rocket in 2008. The launch will be shared with Planck, ESA's mission to study relic radiation from the Big Bang.