"It's beautiful. It's beautiful," murmured Charles Kohlhase, Cassini's science and mission design manager. "We've been waiting a long time for this."
The mammoth Titan 4-B rocket carrying Cassini blasted through clouds into a moonlit sky well before dawn. Everything went fine on this second launch attempt; high wind and computer problems scuttled Monday's effort.
With 72 pounds of plutonium aboard Cassini _ the most ever flown in space _ anti-nuclear activists feared a radioactive shower in the event of a rocket explosion. NASA insisted all along, however, that the launch would be safe because of the numerous precautions taken with the poisonous substance, shielded several times over.
"We're all very excited. We knew there wouldn't be a problem," said the Energy Department's Beverly Cook, who's in charge of Cassini's nuclear power load. "But we were prepared _ it's designed for accidents. I'd hate to have lost this mission, but there wasn't going to be a safety problem."
The plutonium is needed to power Cassini, the largest, most expensive interplanetary probe ever assembled by NASA. Saturn is so far from the sun that traditional solar panels would be useless unless they were the size of a couple tennis courts, and then they would be too big to launch.
Cassini's $3.4 billion mission won't begin, scientifically, until the spacecraft reaches Saturn in 2004. The route to get there is circuitous to say the least: The first stop, so to speak, is Venus in 1998 and again in 1999 for gravity-assisted speed.
The spacecraft also will sweep within 500 miles of Earth in 1999 _ which has Cassini opponents more terrified than did the launch _ and by Jupiter in 2000. Cook said there is a less than 1-in-1 million chance that the probe would re-enter Earth's atmosphere in 1999 and spread plutonium.
"If there is a problem, I still believe it's very safe," she said this morning.
If all goes well, the two-story robotic explorer will be the first probe to orbit Saturn, doing so 74 times. It also will sweep 45 times past Titan, Saturn's largest moon and the second-largest moon in the solar system.
Perhaps most spectacularly, Cassini will release a European-built probe to land on the frigid Titan. Scientists say its cold, preserved state could provide clues as to how life evolved on Earth.
Cassini is the last of NASA's big-ticket interplanetary spacecraft. Development began in 1989, well before the space agency was forced to shrink its workforce and budget.
Future probes will be a mere 10 percent to 15 percent the size and cost of Cassini, said Wesley Huntress Jr., NASA's space science chief. As a result, they will need far less plutonium for power, he said.
Anti-nuclear activists promised to continue their fight.
"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 its court attempt to stop Cassini. "We just keep