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Last of the mega-missions
Cassini a holdover from the NASA of old
(CNN) -- In NASA's new "smaller, faster, cheaper" era, Cassini is a dinosaur.
The last of the big-budget, big-mission planetary probes, Cassini stands over two stories tall and weighs more than six tons. At $3.4 billion, its budget dwarfs the recent Mars Pathfinder and Mars Global Surveyor missions.
In the tradition of Viking, Voyager and Galileo, Cassini's mission is ambitious. If all goes according to plan, it will travel some 2.2 billion miles over more than a decade, carrying 18 complex science instruments and dispatching a probe dubbed Huygens to the surface of Titan, the largest of Saturn's 18 known moons.
Cassini likely would have fallen prey to budget cuts if not for the emphasis on space exploration as a venue for international cooperation. The Huygens probe was built by the European Space Agency, which also helped fund the project, and some of the experimental equipment was provided by ASI, the Italian space agency.
The sheer distance of the mission is perhaps the most daunting challenge Cassini's designers faced. More than half of Cassini's liftoff weight is fuel. It will be propelled into orbit by a Titan IVB/Centaur rocket, the largest expendable booster in the U.S. space fleet.
The ship will circle Venus twice, come back to orbit the Earth and then circle Jupiter, using the planets' gravity to "slingshot" it to Saturn at higher speeds than it could reach with its engines alone.
Facts about Saturn:
Size: Ten times the size of our planet, Saturn's mass is equal to 95 Earths.
Density: With a density 30 percent less than water, it would float in an ocean -- if there was one large enough.
Features: Has 18 confirmed moons, the largest number in the solar system. Scientists in 1995 sighted objects that might be four new moons. Its famed rings are some 450,000 miles in diameter, but only a couple of hundred miles thick.
Cassini is scheduled to arrive in orbit around Saturn in 2004 and will continue feeding back data until at least 2008.
Powering the ship, which will be too far from the sun -- 1 billion miles -- for solar panels to be effective, is another challenge. Power packs fueled by well-sealed but still potentially lethal plutonium will supply heat and electrical power. These power packs, which have been carried on 23 U.S. missions, including the Galileo probe now orbiting Jupiter, have drawn opposition from anti-nuclear activists. (For details, read Cassini: The Controversy)
NASA planners make no excuses about the cost and the risks associated with the mission.
If Cassini performs as planned, the mission is expected to reap a rich scientific harvest from one of the most diverse neighborhoods in our solar system.
Says NASA scientist Wesley T. Huntress: "This will be a very rare opportunity to gain insights into questions of the origin of the solar system and even the beginning of life."
M i s s i o n i n D e t a i l The Cassini Orbiter The Huygens probe
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