In the final two years before Saturn, science instruments will become more and more active as they perform calibrations, take long-range and test images, and prepare for the tour. In mid 2004, the Cruise period comes to an end and the Tour begins. Later, in November 2004, the Huygens probe will be released on its journey to Titan. It is the only satellite massive enough to provide any appreciable gravity assist. With repeated flybys of Titan, Cassini can travel around to any portion of the system - but it takes a lot of flybys, which means it takes time.
Titan is also interesting from a scientific standpoint.
The other moons are also important and there will be at least five close flybys of the icy satellites as well as those of Titan. The figures to the right show the trajectory to be taken by Cassini through the Tour as viewed from above Saturn and viewed from the side. Though small propulsive maneuvers are included to allow some flexibility, the number and size of these maneuvers must be minimized. In other words, raising inclination to high levels takes a great deal of time. Occultations happen when the Earth, the Sun, or stars cross behind Saturn, Titan, or the rings as viewed from the spacecraft.