The Cassini mission is split into two major segments: Cruise and Tour. Cruise, as the name suggests, covers all the activities before we near Saturn. If you were taking a trip to the mountains, you'd call the driving, stopping for gas, checking the map, and thinking about what you'll do when you get there the "Cruise" segment. You might also check the tires and the oil to make sure everything works okay.

Once you arrived at your destination and parked the car, you'd have begun your "Tour" segment, when you'd explore the wilderness and learn about your new environment.

Getting to where we want to go

Did you know...? Cassini will travel 3.2 billion kilometers (2 billion miles) to reach Saturn and another 1.7 billion kilometers (1.1 billion miles) while in orbit around Saturn. (Image JPL-27089AC)

The spacecraft will stay pointed in one direction with the High Gain Antenna (the large dish used for communcations) facing the Sun. The antenna shields the spacecraft from the Sun's heat, which is especially important since the spacecraft will get up to 40% closer to the Sun than the Earth — equivalent to a heavy baking by Earth's — and Saturn's — standards. Turns during cruise will be done with the thrusters, or reaction control system. This strategy will save reaction wheel lifetime for the tour, and allow faster turns to minimize exposure of sensitive spacecraft components to heat from the Sun.

Did you know...? The spacecraft will reach relative speeds of 5.2 kilometers per second (11,634 mph) approaching Saturn, 19.0 kilometers per second (42,511 mph) flying by Earth and 13.6 kilometers per second (30,430 mph) flying by Venus - equivalent to flying from Los Angeles to Boston in under 5 minutes!

One main issue during Cruise is the low data rates we have to deal with. Even though the spacecraft is a lot closer to Earth than it is when it gets out to Saturn, the communication is much slower because we can't point the High Gain Antenna at Earth until a few years into cruise (it's shielding important hardware from the Sun's harmful radiation). Fortunately, the Deep Space Network can give us more coverage with their radio dishes near important events where we need more data. A few months after the Earth flyby in 1999, the spacecraft is far enough away that it can point the HGA off the Sun a few degrees to link with Earth and the problem goes away.

Did you know...? Gravity assists from two swingbys of Venus and one of Earth provide the equivalent of 68,040 kilograms (75 tons) of rocket fuel.

Each flyby will be done carefully, with small correction maneuvers to maintain the spacecraft on the pre-planned trajectory. The Earth flyby is especially important; we must make sure if something unexpected goes wrong the spacecraft doesn't hit the Earth by accident. The Cassini mission designers have spent a great deal of time and effort to ensure that the probability of hitting the Earth is less than one in a million.

After the Jupiter flyby, which is the most distant, there are several years to wait until we arrive at Saturn. During this time Cassini will help look for waves in the gravitational field of the Solar System. As the spacecraft approaches Saturn, science instruments will become more and more active as they perform calibrations, take long-range and test images, and gear up for the tour.

The following table shows some of the important events in the mission, from launch in 1997 until the end of mission in 2004. This table includes maneuvers, flybys, gravity wave experiment times, and information on other science and trajectory events.