The Cassini-Huygens mission, involving ESA, NASA and the Italian Space Agency, has changed many of our ideas about the Saturn system. Launched from Florida in October 1997, it took almost seven years to reach Saturn, travelling nearly 3.5 billion kilometres. The 5.6 tonne spacecraft was made up of two parts – the Cassini orbiter and the Huygens probe.
Cassini is the first spacecraft to orbit Saturn. It carries 12 experiments. Since arrival at Saturn on 1 July 2004, Cassini has been sending back huge amounts of new information about Saturn, its rings, moons and magnetic field.
Originally planned as a four-year mission, Cassini-Huygens has been so successful that it has been extended until at least 2017. It has flown past seven of the larger satellites, including giant Titan – which is larger than the planet Mercury. The orbiter has swept past Titan more than 70 times. Flying within 880 km of the moon, it has studied Titan’s orange clouds and nitrogen-rich atmosphere. It has also mapped its surface with an imaging radar. .
On Christmas Day 2004, Huygens separated from Cassini. Three weeks later, it slammed into Titan’s thick atmosphere, becoming the first probe to descend to the surface of a planetary satellite (other than our Moon). Protected by a heat shield, the probe slowed from 18,000 to 1,400 km per hour in just three minutes. Soon after, a large parachute opened out. At a height of about 160 km, the probe began to take pictures and study the atmosphere. For more than two hours, data from Huygens were received and stored on Cassini as it flew overhead.
The pictures and other information sent back by its six instruments told us for the first time what this orange moon is really like. Huygens touched down on a dry river bed covered in small icy boulders.