CASSINI PROBE BEGINS 7-YEAR TRIP TO WORLD OF RINGS, MOONS.

Byline: Associated Press 

With its destination beckoning in a moonlit sky, NASA's plutonium-powered Cassini spacecraft rocketed flawlessly toward Saturn on Wednesday on a mission activists had tried to stop for fear an accident would shower Earth with radioactive fallout.

Saturn appeared as a yellowish speck above the nearly full moon as the monstrous Titan 4-B rocket carrying Cassini thundered away before daybreak. Forty minutes later, Cassini shot out of Earth orbit and was on its way to Saturn.

The journey to the ringed planet will take seven years and cover 2.2 billion miles. Once there, Cassini will spend four years exploring Saturn, its rings and its icy moons, especially the biggest, Titan.

The chairman of the Italian Space Agency's scientific committee pronounced it ``a historic moment.''

``It is the link that connects this millennium to the next,'' Giancarlo Setti said.

After a two-day delay caused by high wind and computer problems, the launch was perfect. Anti-nuclear activists, 22 of whom showed up at the last minute to protest, feared the worst if the rocket carrying Cassini and its 72 pounds of extremely poisonous plutonium exploded.

It is the most plutonium ever flown in space. It is also the biggest, most complex interplanetary probe and the most expensive, too - $3.4 billion for the whole mission.

There will be few if any probes like Cassini again as the National Aeronautics and Space Administration pushes a ``faster, better, cheaper'' agenda.

``The scale of this project kind of matches the majesty of the place where it's going,'' said NASA's chief space scientist, Wesley Huntress Jr. ``This is the second-largest planet in the solar system, and you put the rings around it and it's the biggest. It's also the most spectacular. It has a huge retinue of moons and this strange and enigmatic place called Titan that we don't know very much about.''

Cassini's mission won't begin, scientifically, until the spacecraft and its 18 instruments reach Saturn in July 2004.

The route is roundabout: The first stop, so to speak, is Venus in 1998 and again in 1999 to use the planet's gravity like a slingshot to speed Cassini on its way. The spacecraft also will sweep within 500 miles of Earth in 1999 - a prospect that terrifies Cassini opponents more than the launch did - and by Jupiter in 2000.

NASA said there is a less than 1-in-1 million chance that the probe will enter Earth's atmosphere in 1999 and spread plutonium.

Opponents said they would continue their fight. NASA plans to use plutonium - though less of it - on its smaller interplanetary missions.

``It's a bigger picture than even just Cassini. This is an icebreaker,'' said Carol Mosley of the Florida Coalition for Peace and Justice, which failed in a court attempt to stop Cassini. ``We just keep going.''

If all goes well over the next seven years, the two-story robotic explorer, named after Gian Domenico Cassini, the 17th-century Italian astronomer who discovered the largest gap in Saturn's rings, will be the first probe to orbit Saturn. Previously, three spacecraft - Pioneer 11 and Voyagers 1 and 2 - flew past Saturn in the late 1970s and early 1980s.

This is the busiest period in interplanetary exploration since then, with Pathfinder on Mars, Global Surveyor orbiting Mars, Galileo orbiting Jupiter and Cassini bound for Saturn.

Cassini will orbit Saturn 74 times and fly through some of its wispier rings. It will also sweep at least 45 times past Titan, the largest of Saturn's 18 known moons, venturing as close as 530 miles.

Perhaps most spectacularly, Cassini will release a European-built probe to land on Titan in 2004. Scientists say the moon's cold, preserved state could provide clues as to how life evolved on Earth. A microphone on the lander - another first - will beam back Titan's sounds.

Eventually, Cassini - and its attached digital disk containing more than 600,000 signatures from 81 countries - will crash onto Saturn or one of its moons.

But that could be centuries away; scientists Wednesday preferred to dwell on Cassini's beginning.