What's it for?
Hubble, Herschel… observers of elsewhere
Apart from probes, which are special sorts of satellites that go off on voyages across the solar system and sometimes beyond, some satellites’ job is to look out towards space and not towards Earth. Released from the “censorship” that our atmosphere practices on the electromagnetic spectrum, they can see much further and many more things than earthbound telescopes.
Hubble, a star photographer
Hubble is a true space telescope developed and operated in cooperation by NASA and the ESA, and is the best known of these explorers of elsewhere. Its photos are among the best and best known of our solar system. Mounted on a satellite in 1990 at 600 km altitude, it can photograph objects thirty times less well illuminated than those observable by the most powerful earth-bound cameras.
Europe in the lead
With the Herschel telescope, Europe has the largest mirror in orbit: a diameter of 3.5 m as compared with Hubble’s 2.6. It is important to know that the larger the diameter of the mirror, the more light there is and the better the resolution of the image. It took EADS Astrium several years to build this giant A silicon carbide ceramic was selected to make the renowned mirror. Herschel was launched in 2008 and specialises in taking measurements in infra-red at extreme range and of nano-objects.
Far is old
The further one looks in space, the more one goes back in time. Albert Einstein demonstrated the equivalence of distance and time: what unifies space and time in a single equation is that the measurement of time can be changed into a measurement of distance. As a result, the greater the telescope’s power, the further it can go back in the Universe’s history. So a satellite is also the guardian of the past.
