The Huygens probe, supplied by the European Space Agency, carries a well-equipped robotic laboratory that it will use to scrutinize the clouds, atmosphere and surface of Saturn's moon Titan. Released by the orbiter in November of 2004, the Huygens probe will drop into Titan's atmosphere some three weeks later. As the 2.7 meter (8.9 foot) diameter probe enters the atmosphere it will begin taking measurements in the upper stratosphere. As it descends -- first on a main parachute and later on a drogue chute for stability -- various instruments will measure the temperature, pressure, density and energy balance in the atmosphere. (Image P-46508AC)
Did you know...? Over 300,000 color images of Saturn, the rings, Titan and the other moons will be returned including 1100 pictures of Titan taken by the Huygens Probe. (Image P-23929)
After the probe is released in early November, the orbiter performs a propulsive maneuver to target for the flyby and delay its arrival to Titan so that it can have the proper geometry to view the probe descent region. During the probe mission, the orbiter will fly above Titan and listen with its High Gain Antenna (HGA) for data transmitted by the probe. This data must be first stored on the orbiter's Solid State Recorder before it can be downlinked to Earth later. The project has a number of strategies, including downlinking the probe data multiple times, to ensure that the probe data gets to Earth with no problems.
As the Huygens probe breaks through the cloud deck, a camera will capture pictures of the Titan panorama. Other instruments will directly measure the organic chemistry in Titan's atmosphere -- providing the equivalent of a time machine to examine the chemistry of the early Earth. Instruments will also be used to study properties of Titan's surface remotely, and perhaps even directly after landing on the surface.
This is a depiction of the sequence of events during the Huygens probe mission. First, the probe enters the upper atmosphere and uses its heat shield to decelerate. At an altitude of about 175 kilometers (110 miles), the probe pops its main parachute, jettisons the heat shield, and begins its experiments. Fifteen minutes later, it jettisons its main chute, deploys a smaller parachute, and descends the last 140 kilometers (90 miles) or so to the surface, collecting data the whole way and relaying it to the orbiter above. (Image only available electronically)
After the probe mission is completed, the spacecraft will turn the HGA to Earth and begin transmitting the recorded probe data. The data will even be transmitted twice and be verified on the ground before it can be overwritten on the data recorders. Once the data is verified, the probe mission is considered to be complete.
A map of Titan's surface, as best determined by Earth-based observations. The image shows a flat projection of surface brightness. The bright areas may be highlands, lowlands, or oceans. Courtesy Peter Smith and Mark Lemmon et al. (Image only available electronically)
Many scientists theorize that Titan may be covered by lakes or oceans of methane or ethane. This remains a mystery; the laws of thermodynamics say such oceans should exist, while radar studies conducted from Earth have turned up no evidence of them. Theories from the study of tidal motions suggest that Titan should either be covered by all oceans or all land, but nothing in between. The resolution of this puzzle is up to Cassini.
