This animation illustrates the path the Cassini spacecraft will take during its four year mission at Saturn. The viewpoint is far from Saturn looking down on Saturn's ring plane. The Cassini spacecraft is depicted by a white sphere and the path Cassini takes about Saturn (depicted by the yellow sphere in the middle of the frame) is shown by the white line. The white line traces the path of the spacecraft about Saturn much like tracing a path in wet sand with a stick. The animation moves rather fast so you may wish to manually move through time using the slider button at the bottom of the frame. The date corresponding to the image is shown in the left hand corner in year/month/day format.
Saturn's largest moon Titan is depicted by the orange sphere and its circular path about Saturn is depicted by the orange line. Titan is shown since it acts as the cosmic fuel tank for Cassini. Each close flyby of Titan alters the path of the spacecraft due to the gravitational pull by the Moon. By clever use of these "gravity assists", the path of Cassini can be changed to cover the wide range of viewpoints needed to fully study the Saturnian system with Cassini's large suite of instruments. Using gravity instead of rocket fuel enables such a wide diversity of orbits.
Why does Cassini follow this particular path? An apt analogy would be a family car trip to an exciting new country. The passengers in the car all want to go to a different destinations during their tour. The driver plans the path the car will follow by attempting to meet everyone's desires but is limited by how much time they have, how much gas is in the car, how fast they can drive, etc.. The Cassini tour about Saturn was designed in much the same way. Like the passengers in the car, the various instruments on Cassini often want to go to very different destinations within the Saturnian system. The tour was designed to please each instrument team just as the driver attempts to please his passengers. Compromise is involved since no one instrument,or passenger, rules the road!