Friedrichshafen, 19
September
2007
The integration of Europe’s Herschel Space Observatory is almost complete. All three scientific instruments have been integrated into the payload module at the Astrium facility in Friedrichshafen. In the last few days the payload and service modules have been connected. These activities will be followed by extensive functional, performance, compatibility and environmental tests. In November 2007, the satellite will be shipped to the European Research and Technology Centre (ESTEC) in Noordwijk, the Netherlands, for acceptance tests. It is scheduled for launch from the European Space Port at Kourou in French Guiana on 31 July 2008, on an Ariane 5 ECA launch vehicle together with the Planck satellite.
With ESA’s Herschel at their disposal astronomers will be able to see billions of light years into the universe, peeking into the “cradles” of the stars. Herschel will enable astronomers to observe the evolution of stars and galaxies in the infrared spectrum with unprecedented resolution. Astrium has developed, assembled and tested the satellite's central element, the payload module with its superfluid helium cryostat, on behalf of ESA. Having a silicon carbide (SiC) telescope, with a 3.5m diameter primary mirror, manufactured by Astrium in Toulouse, Herschel will be the largest imaging space telescope ever built.
Herschel will be able to detect even the faintest of heat emissions from stars and galaxies. In order to prevent the sensitive instruments from being ‘dazzled’ by the thermal radiation generated during operation of the satellite, their detectors must be cooled inside the cryostat – a cryogenic unit – down to minus 273 degrees Celsius (about 0.3 degrees above absolute zero). This low temperature will be achieved by using 2,300 litres of superfluid helium at minus 271 degrees Celsius and an additional cooling stage inside the focal plane units. The service life of the cryostat will be at least three and a half years in space.
With a height of 7.5m and a diameter of 4.5m, Herschel is impressive in size. It has a launch mass of approximately 3.35 tons. Its three highly sensitive instruments, which include cameras, photometers and spectrometers, will operate at far-infrared and sub-millimitre wavelengths.
In the infrared spectral range, the universe appears completely different to astronomers than in the visible light range. Herschel will therefore be an all-purpose facility with almost inexhaustible fields of application. One central field of research will be the study of the early and late phases of stellar evolution, in other words, the birth and death of stars..
Huge cold clouds of gas and dust are scattered all over the Milky Way. Under specific conditions and the pull of gravitational forces, individual areas inside these clouds collapse more and more eventually forming new stars. Our sun was created in the same way. Not until the stars begin to shine brightly do they clear the environment of the remaining dust and become visible over great distances.
In the visible light range, it is not possible to witness these early stages in the birth of a star because they take place deep inside these cold clouds. Infrared radiation, by contrast, makes this possible. The emission from the dust clouds is in the infrared, yielding new insights into the formation of stars and their associated planetary systems
A second central field of research concerns the formation and evolution of galaxies. Astronomers have learned that in some young galaxies, that existed for a few billion years after the big bang, up to one hundred times more stars per year were formed than in our galaxy today today. The hot nascent stars heated the dust around them to extreme temperatures, causing it to emit intensive heat radiation in the infrared range.
These young galaxies are many billions of light years away. Because of the expansion of the Universe, their light is displaced towards longer wavelengths. Astronomers call this phenomenon “cosmological redshift”. As a result, the infrared radiation emitted by the dust at, say, 100 microns, could be reaching us at a wavelength more than double that. Herschel will be the first space telescope ever to be sensitive to this range, which is inaccessible from the Earth’s surface because of the absorbing atmosphere.
Astrium, a wholly owned subsidiary of EADS, is dedicated to providing civil and defence space systems and services. In 2006, Astrium had a turnover of €3.2 billion and 11,000 employees in France, Germany, the United Kingdom, Spain and the Netherlands. Its three main areas of activity are: the business units Astrium Space Transportation for launchers and orbital infrastructure, and Astrium Satellites for spacecraft and ground segment, and its wholly owned subsidiary Astrium Services for the development and delivery of satellite services. EADS is a global leader in aerospace, defence and related services. In 2006, EADS generated revenues of €39.4 billion and employed a workforce of more than 116, 000.
