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Cassini mission history
The Cassini Mission
The Cassini mission has two primary elements, consisting of the Huygens moon lander, and the Cassini planetary orbiter.
Launched on October 15, 1997 from the Kennedy Space Center in Florida, the Cassini-Huygens probe took a very long and indirect path to reach Saturn. This path was necessitated by the heavy weight of the probe - over six tons, including propellant. Lacking a strong enough booster, NASA devised a flight path that utilized the gravitational forces of Venus, Jupiter, and the Earth to create a slingshot effect to generate the necessary velocity to reach Saturn.
Four gravity assists were required to hurl the spacecraft to Saturn. Cassini used an interplanetary trajectory that took it by Venus twice, then past Earth and Jupiter. After flying past Venus twice, first at an altitude of 284 kilometers (176 miles) on April 26, 1998 and again on June 24, 1999 at 600 kilometers (370 miles), the spacecraft then swung past Earth at an altitude of 1,171 kilometers (727 miles) on August 18, 1999. Given these three gravity assists, Cassini finally had enough momentum to reach the outer solar system. The fourth and final gravity assist was from Jupiter on December 30, 2000, at an altitude of 9,723,890 million kilometers (6,042,145 million miles) boosting Cassini all the way to Saturn.
After a nearly seven-year journey covering 3.5 billion kilometers (2.2 billion miles), Cassini arrived at Saturn on July 1, 2004. The most critical phase of the mission after launch was Saturn orbit insertion. When Cassini arrived at Saturn, the spacecraft fired its main engine for 96 minutes to brake its speed and allow it to be captured as a manmade satellite of Saturn. Flight planners used the spacecraft's dish-shaped high-gain antenna as a shield to provide some protection against any small particles that were present during the ring crossing.
After dropping off the Huygens Titan lander on December 25, 2004, Cassini resumed its orbital exploration of Saturn. Mission plans called for at least 76 orbits around Saturn, including 52 close encounters with seven of Saturn's 31 known moons. Cassini's orbits around Saturn will be shaped by gravity-assist flybys of Titan. Close flybys of Titan will permit high-resolution mapping of Titan's surface with the Titan imaging radar instrument, which can see through the opaque haze covering that moon to hopefully produce vivid topographic maps of the surface.
Cassini will make at least six close targeted flybys of four icy moons of greatest interest -- Iapetus, Enceladus, Dione and Rhea. Images taken with Cassini's high-resolution telescopic cameras during these flybys will show surface features equivalent in size to a baseball diamond. At least two dozen more distant flybys at altitudes of up to 100,000 kilometers (60,000 miles) will be made of the major moons of Saturn other than Titan. The varying inclination angle of Cassini's orbits also will allow studies of Saturn's polar regions in addition to the planet's equatorial zone.
The prime mission tour concludes on June 30, 2008, four years after Saturn arrival and 33 days after the last Titan flyby, which occurs on May 28, 2008. The aim point of the final flyby is chosen to position Cassini for a Titan flyby on July 31, 2008 -- providing the opportunity to proceed with more flybys during an extended mission, if resources allow. Nothing in the design of the tour precludes an extended mission.
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