Earth Encounter Propels Cassini Toward Saturn

A plutonium-powered spacecraft swung by its home planet late Tuesday, successfully flying within 727 miles of Earth to gain enough momentum for the final leg of its seven-year journey to Saturn.

The $3.4-billion Cassini probe, NASA’s largest and most expensive ever, reached its closest point over the southeastern Pacific Ocean as expected at 8:28 p.m. Using Earth’s gravity, it then shot toward the ringed planet for its July 2004 arrival.

“It’s on its way out,” said Mary Beth Murrill, spokeswoman for the Jet Propulsion Laboratory in Pasadena.

Anti-nuclear activists had feared that human error or some other accident could fling the spacecraft and its 72 pounds of plutonium into the Earth’s atmosphere and shower the planet with deadly radioactive debris.

But NASA said there was only a 1-in-1.2 million chance of accidental reentry.