Cassini Mission to Saturn Lifts Off Amid Cloud of Controversy

Loaded with 72 pounds of radioactive plutonium and freighted with controversy, the Cassini spacecraft rocketed safely away from Earth early Wednesday on the start of an ambitious seven-year scientific mission to Saturn.

The predawn liftoff was both spectacular and routine, and came 48 hours after the originally scheduled launch was scuttled by high winds and computer failure.

Flames shot out from the base of the Titan IV / Centaur rocket, the darkness parted, and the 6-ton spacecraft made a stately, roaring ascension into the starry night--lighting the sky with a brilliance that made the full moon look pale.

“This is special,” exclaimed physicist Hunter Waite, one of dozens of scientists involved in the 15-year project who were on hand to witness the start of the Cassini’s 2.2-billion-mile journey.

The $3.4-billion mission to explore the planet Saturn is the most complex and expensive unmanned space probe ever launched and the last of NASA’s big-ticket interplanetary voyages.

Packed with sophisticated monitoring gear, computers and a huge amount of fuel, the Cassini orbiter is designed to plumb the mysteries of Saturn and its intriguing, colorful rings, and then parachute a smaller probe, called Huygens, onto the surface of Titan, one of the planet’s 18 known moons.

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Scientists expect the mission to provide insights into the origin of the solar system and even the beginnings of life. “It will take about seven years for the public to see the benefits of this mission, but they will see,” said Waite, who works for a San Antonio firm subcontracted by Pasadena’s Jet Propulsion Laboratory. Waite will monitor instruments designed to read the chemical makeup of Saturn’s rings and the Titan atmosphere.

The Cassini mission is one of the most controversial ever undertaken by NASA. Critics contend that the 72 pounds of plutonium on board--the most ever sent into space and a necessary fuel, say scientists, for batteries that power the 11-year mission (Cassini will orbit Saturn for four years)--pose an unacceptable risk to human life. An explosion at launch, opponents charged, could have released radioactive dust affecting a wide swath of the Central Florida population, leading to a surge in cancer deaths.

Although no explosion occurred Wednesday, critics say humans will be imperiled again in August 1999, when the spacecraft passes within 500 miles of Earth on a fly-by maneuver designed to slingshot Cassini toward Jupiter before heading to Saturn.

Only a handful of protesters showed up outside the gates of the Cape Canaveral Air Station before dawn Wednesday, but security was tight. Those credentialed to pass through the guarded gates of the Kennedy Space Center were asked not only to show identification but also to open the trunks of their cars for inspection.

Compared to the crowds that normally gather to watch daytime shuttle launches here, spectators were few. Among the scientists and contractors who worked on the Cassini probe were many European visitors and journalists, reflecting worldwide interest in the mission, a joint project of NASA, the European Space Agency and the Italian Space Agency. The mission is managed by JPL.

“We’re all very excited. We knew there wouldn’t be a problem,” said Beverly Cook, an Energy Department physicist in charge of testing the plutonium fuel generators.

In town meetings and in interviews spread around the world, Cook, NASA officials, Cassini project manager Richard Spehalski and others have insisted that the plutonium--encased in several layers of protective materials--is safe. Spehalski, among others, made a point of inviting his relatives to watch the launching.

After a review, the White House Office of Science and Technology Policy declared that “the important benefits of this scientific mission outweigh the potential risks.”

Still, many people, including some scientists and a retired NASA safety director, remained unpersuaded. Foes tried unsuccessfully to block the launching in federal court and by climbing over barbed wired fences around the Cape Canaveral Air Station, where 27 people were arrested for trespassing on Oct. 4. Some area residents, fearing the longshot chance of a launch-pad ccident, packed up their families and left the area before Monday’s scheduled liftoff. And some fled again two days later.

Cassini, named for 17th century Italian-French astronomer Jean-Dominique Cassini, will swing by Venus twice and Earth once to make use of gravity assists that will help propel the spacecraft to Saturn. On the trip itself, Cassini is kept on course by sensors that recognize reference stars and the sun.

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Once in orbit around Saturn in 2004, Cassini is to send back more than 300,000 color pictures of the planet and its rings, which are made up of sand, ice crystals and rock that range in size from a tiny fragment to a train car.

Four months after starting to orbit Saturn, on-board computers will awaken the Huygens Titan Probe, which will be released in a 22-day descent through the moon’s gaseous atmosphere. Data collected by the Huygens, named for the Dutch scientist Christiaan Huygens, who discovered Titan in 1655, will be relayed to Cassini and stored for transmission to Earth.

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MISSION TO SATURN

Bound for a seven-year journey to the ringed planet Saturn, the Cassini spacecraft was launched aboard a Titan IV rocket Wednesday from Cape Canaveral, Fla. Cassini will explore Saturn’s gossamer rings, twisted and braided by the action of the giant planet’s 18 moons, as well as the planet itself--the second largest in the solar system. The spacecraft’s four-year tour will include several close passes by Saturn’s mysterious orange moon, Titan.

HUYGENS PROBE

The 9-foot probe will enter the atmosphere of Saturn’s largest moon, Titan, at over 13,000 miles per hour. A heat shield will protect it. A series of parachutes will deploy 105 miles from the planet, setting the probe on the surface.

PROBE FACTS

* Cassini is two stories tall, 13 feet wide, with a mass of 5,510 pounds and 6,615 pounds of propellant.

* It requires 20 watts of power to send a radio signal from Saturn to Earth. The signal typically takes at least an hour to reach the Earth from Saturn.

* Cassini uses 40,000 feet of cabling.

* Cassini is designed to withstand the heat of 2.7 Suns.

* Well over 99% of Cassini’s trip will be an unpowered coast through space.

* Cassini will travel 2 billion miles to reach Saturn, traveling at 18,720 mph in the approach.

* Cassini could transmit up to 4 gigabits of information per day. Over 300,000 color images will be returned, including 1,100 pictures of Titan taken by the Huygens Probe.

CASSINI TRAJECTORY

Saturn is almost a billion miles away, so distant that even an enormous Titan IV rocket lacks the power to get a spacecraft there in one shot. So NASA engineers will make use of the gravitational pulls of Venus, Earth and Jupiter to slingshot the Cassini spacecraft to the ringed planet.