Mission controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif. this morning successfully completed the final firing of the Cassini spacecraft's rocket engine before the craft zings past Earth next week. The trajectory-correction maneuver lasted just over two minutes, and set the spacecraft on a path that will bring it within 725 miles of Earth Tuesday night. NASA reports that the maneuver went exactly as planned.

NASA engineers are using the swing past Earth to slingshot Cassini on its way toward Saturn. Cassini is scheduled to reach the ringed planet in 2004 after almost seven years in transit. The spacecraft is scheduled to orbit Saturn for four years to provide detailed studies of the planet's atmosphere, magnetic field, rings and moons.

The flyby, also called a gravity assist, will increase Cassini's speed away from the sun by roughly 12,000 mph, said Bob Mitchell, program manager for the Cassini mission. Coaxing the same boost from chemical propellant would require at least ten tons of additional fuel, he calculated. The craft has already benefited from two flybys of Venus, and it will also use Jupiter's gravity to throw it toward Saturn.

Cassini is now within 10 million miles of Earth, approaching from the direction of the sun, Mitchel said. "In fact if you were out early enough in the evening to see Venus, it's a little below Venus, between Venus and the Sun."

The flyby has attracted protest from people who fear an accident could send Cassini into a collision course with Earth. The spacecraft's electric generators are powered by 72 pounds of radioactive plutonium oxide, which some fear could increase the odds of contracting cancer on Earth if the spacecraft were to burn up in the atmosphere.

Cassini scientists said the odds of such an accident are now less than infinitesimal.