Cassini a ringing success

By Guy Gugliotta
The Washington Post

AP This image released yesterday shows an area of Saturn's A Ring taken by the Cassini spacecraft.

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Related stories Cassini spacecraft orbiting Saturn Other links Cassini-Huygens: Mission to Saturn & Titan AP video report: Cassini orbits Saturn

"I don't think you have to be a ring scientist to understand what this was for us," said Porco, the imaging team leader for the Cassini-Huygens mission to Saturn. She blinked: "It's just beyond description."

Benumbed from lack of sleep and the tensions of shepherding a $3.3 billion spacecraft into orbit around the solar system's sixth planet, scientists at California's Jet Propulsion Laboratory studied ring photographs yesterday, listened to sonic booms from the solar wind and marveled at how the most ambitious space science mission in history was unfolding — just about perfectly.

"I feel humbled, because nothing ever happens this way," said David Southwood, director of scientific programs for the European Space Agency, which teamed with NASA and the Italian Space Agency to send Cassini-Huygens aloft. "You do the best you can, but the thing about being in space is you can't go up and fix it."

In a spectacular finale to a seven-year voyage from Earth, Cassini-Huygens soared up through Saturn's rings late Wednesday night, settled into orbit and, by dawn yesterday, had swooped back down through the rings, outward bound on the first of 76 circuits of Saturn, along the way transmitting data and photographs from the closest encounter that any human-made object had ever had with the planet.

Cassini took 61 pictures of the rings, some from the "dark" side away from the sun, showing them backlit, others from the sunlit side, illuminated directly.

Scientists at a news conference yesterday played the sound generated by the solar wind hitting Saturn's magnetic field. This "wind" is made up of streams of particles that shoot out from the sun and travel more than 1 million mph, creating a sonic boom when they encounter the magnetic field around Saturn.

The boom, recorded Saturday, occurred much earlier and farther away than expected, suggesting the planet's magnetic field has moved since the last spacecraft flew by a quarter-century ago.

The spacecraft will tour Saturn and its environs for four years, and perhaps much longer, depending on when its fuel runs out, studying a planetary neighborhood that mimics the solar system in many respects and that should provide clues to its formation more than 4 billion years ago, and, perhaps, the origins of life.

By late December, the craft will drop a probe onto the surface of Saturn's largest moon, Titan, which has an atmosphere and possibly oceans of liquid methane.

"It's like having a library in the solar system," said the University of Iowa's William Kurth, who is studying Saturn's magnetic field as part of the project. "We can explore all kinds of things that we can't explore on Earth."

Following the perfectly executed 96-minute rocket "burn" that put the spacecraft into orbit, ground controllers ran checks on all its operating systems as well as the 18 instruments it is carrying: "Every subsystem is completely flawless," project manager Robert Mitchell said. "The spacecraft status is just about perfect."

Mitchell said Wednesday's burn had transpired so successfully that navigators predicted the first orbit of Saturn would finish "within a day" of the planned 116 days, and controllers were trying to decide whether to bother with a "trajectory clean-up maneuver."

Today Cassini-Huygens will have the first of 45 close encounters with Titan, the object that the spacecraft will use for the gravity boosts it needs to change the length and direction of its orbits as it travels the Saturnian system.

Information from The Philadelphia Inquirer is included in this report.

Copyright © 2004 The Seattle Times Company

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