Spacecraft Flies by Moon of Saturn

The internationally built Cassini spacecraft (search) completed a flyby of Saturn's largest outer moon as it prepared to enter a four-year orbit to study the ringed planet, NASA officials said Saturday.

The plutonium-powered spacecraft, which is carrying 12 science instruments and a probe, came within about 1,285 miles of the dark moon Phoebe on Friday, officials at the Jet Propulsion Laboratory (search) said.

The $3.3 billion spacecraft pointed its instruments at the moon, then turned to point its antenna toward Earth. Its data reached NASA's (search) Deep Space Network on Saturday morning.

Officials said the spacecraft was operating normally and was in excellent condition.

"Although this is the first flyby in the Saturn tour, it is the only opportunity to see Phoebe," said Dennis Watson, project scientist for the mission. "This flyby is key to knowing more about the mysterious oddball, which has been the object of interest of many scientists."

A crisp black-and-white photo of Phoebe released Saturday looked somewhat like a skull with its overlapping shadows and craters. Higher-resolution photos of the moon, which is just 137 miles across, were to be released later.

The spacecraft also transmitted data that scientists will examine to answer questions about Phoebe's mass and composition, said Torrence Johnson, a member of Cassini's science team.

"This is an extremely battered, old surface we're looking at," Johnson said about early images from the spacecraft. "There are deep craters from other space debris that over eons have pockmarked the surface. It's roughly round, but it's really chipped away."

Scientist believe Phoebe originated in the outer reaches of the solar system but later hurtled toward Saturn, where it was captured by the planet's gravity.

With the flyby of Phoebe behind it, Cassini's next key maneuver is a trajectory correction scheduled for Wednesday to position the spacecraft to become a satellite.

The U.S.-European spacecraft is expected to enter Saturn's orbit on June 30 after it dashes through a gap in Saturn's rings.

Cassini will study Saturn, its rings and 31 known moons during its four-year orbit. Its two cameras could take as many as 500,000 pictures.

Other probes have flown by the planet, but none have entered Saturn's orbit.

Cassini also carries the Huygens probe, which is supplied by the European Space Agency and carries six instruments. The probe, set to be released in December, is expected to land on Titan, Saturn's largest moon.