The Huygens probe touched down on the surface of Titan this morning.
Following its release from the Cassini mothership on 25 December, Huygens reached Titan’s outer atmosphere after 20 days and a 4 million km cruise. The probe started its descent through Titan’s hazy cloud layers from an altitude of about 1270 km at 11:13 CET. During the following three minutes Huygens had to decelerate from 18 000 to 1400 km per hour.
A sequence of parachutes then slowed it down to less than 300 km per hour. At a height of about 160 km the probe’s scientific instruments were exposed to Titan’s atmosphere. At about 120 km, the main parachute was replaced by a smaller one to complete the descent, with an expected touchdown at 13:34 CET. Preliminary data indicate that the probe landed safely, likely on a solid surface.
The probe began transmitting data to Cassini four minutes into its descent and continued to transmit data after landing at least as long as Cassini was above Titan’s horizon. The certainty that Huygens was alive came already at 11:25 CET today, when the Green Bank radio telescope in West Virginia, USA, picked up a faint but unmistakable radio signal from the probe. Radio telescopes on Earth continued to receive this signal well past the expected lifetime of Huygens.
Huygens data, relayed by Cassini, were picked up by NASA’s Deep Space Network and delivered immediately to ESA’s European Space Operation Centre in Darmstadt, Germany, where the scientific analysis is currently taking place.
“Titan was always the target in the Saturn system where the need for ‘ground truth’ from a probe was critical. It is a fascinating world and we are now eagerly awaiting the scientific results,” says Professor David Southwood, Director of ESA’s scientific programmme.
“The Huygens scientists are all delighted. This was worth the long wait,” says Dr Jean-Pierre Lebreton, ESA Huygens Mission Manager. Huygens is expected to provide the first direct and detailed sampling of Titan’s atmospheric chemistry and the first photographs of its hidden surface, and will supply a detailed ‘weather report’.