April 21, 2005

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!