Cassini-Huygens Overview - Huygens
The Cassini-Huygens mission is designed to explore the Saturnian system and all its elements: the planet and its atmosphere, its rings, its magnetosphere and a large number of its moons, namely Titan and the icy satellites. The mission will emphasize Titan, Saturn's largest moon, and the only satellite with a thick atmosphere.
The Cassini/Huygens spacecraft was launched on 15 October 1997 by a Titan 4B/Centaur rocket from Cape Canaveral. With a launch mass of 5650 kg, it was too heavy for a direct injection to Saturn. The flight requires gravity assists from Venus (April 1998 and June 1999), Earth (August 1999) and Jupiter (December 2000). Along this trajectory, the flight time to Saturn is slightly less than 7 years.
The spacecraft will arrive at Saturn on 1 July 2004. The Saturn Orbit Insertion (SOI) will take place on that day. Not only is it a crucial manoeuvre, but it is also a period of unique Orbiter science activity as, at that time, the spacecraft with as close as it ever will be to the planet: 0.3 Saturn Radius. Ring plane crossing occur in the gap between the F and G rings at a distance of about 2.66 Saturn Radius. The SOI will provide a unique observation geometry for the rings and a unique opportunity to study the magnetism of Saturn.
The Huygens Probe is carried to Titan attached to the Cassini Orbiter. After SOI, the Orbiter will be placed on an initial orbit that encounters Titan in late October 2004. On the subsequent orbit, 48 days later, another targeted encounter of Titan occurs. The details of the first two Titan encounters have been worked such that the Orbiter will be placed on the appropriate trajectory for the Huygens mission during the third orbit targeted encounter. The Probe will be released about 22 days before Titan encounter. Shortly after release, the Orbiter will perform a deflection manoeuvre and place itself on the required trajectory for the optimum radio link geometry during the Huygens descent and the surface phase. The Orbiter will be about 60000 km above Titan at closest approach. The communication window is required to last at least 3 hours, but it may last longer. A descent time of between 2 and 2h30 and 3 min on the surface are expected. The communication window is therefore optimised for the first 153 min of data transmission.