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<i>Cassini</i> Spacecraft Enters Saturn's Orbit - 2004-07-01

An American-European spacecraft has entered orbit around the ringed planet Saturn - the first to do so. The maneuver ended a seven-year journey and began a four-year inspection of the giant gas planet and eight of its 31 moons.

The mood was jubilant in Mission Control at the Jet Propulsion Laboratory in Pasadena, California, as joyful as it was in January when twin U.S. rovers landed on Mars. The director of the laboratory is Charles Elachi.

"I can tell you, it feels awfully good to be in orbit around the Lord of the Rings," he said.

On schedule and as programmed, the U.S. Cassini spacecraft passed swiftly between Saturn's rings from below, avoiding potentially fatal collisions with ring rocks. Then it turned and fired braking rockets to slow its speed of more than 100,000 kilometers an hour, so Saturn's gravity could capture the probe and pull it into orbit.

The chief of space science at the U.S. National Aeronautics & Space Administration, Ed Weiler, notes the continuing success the United States has had in its solar system exploration, this year.

"Gee, here we are sitting on this little pale blue dot, third rock from the sun," he said. "We just landed on Mars twice. We flew by a comet and picked up some comet dust, and all within six months we're about to go into orbit around a planet that is a billion miles [about 1.5 billion kilometers] away. How do we get away with having so much fun?"

Soon after entering orbit around Saturn, Cassini began its scientific work. It photographed the dusty rings from above and below and began studying Saturn's magnetic field. The planet is mostly gas, but Cassini team member Michelle Dougherty, of London's Imperial College, says magnetic flux information can provide a better understanding of the what is going on inside the planet's solid core, where the field is generated.

"What that is going to allow us to do is to measure some of the fine detailed structure of the internal field, and that will be able to give us a better understanding of not only how the field is formed, but also hopefully give us a better understanding of about something of the internal structure of Saturn, too," she said.

Scientists are interested in Saturn because they consider it and its 31 moons a miniature planetary system that can provide clues to the origin and processes of the larger solar system.

The mission is a joint project of the American, European and Italian space agencies. Researchers from 17 nations are involved, prompting this comment from NASA's Ed Weiler.

"This wasn't NASA going into orbit around Saturn," he said. "It's the Earth going into orbit around Saturn."

In late December, the European Huygens probe will detach from the Cassini mothership to study the atmosphere of the big moon Titan, which researchers think is similar to that of Earth, before life appeared.