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Snapshots From Saturn

Just hours after swooping into orbit around Saturn, the Cassini spacecraft sent "absolutely mind-blowing" images of the giant planet's rings back to Earth early Thursday.

Scientists were elated at the initial results, reports CBS News Space Consultant Bill Harwood.

"I can tell you it feels awfully good to be in orbit around the lord of the rings," Jet Propulsion Laboratory Director and Cassini radar team member Charles Elachi said.

A carefully choreographed maneuver allowed Cassini to be captured by Saturn's gravity as it arced within 12,500 miles of the giant planet's cloud tops.

Using its big radio dish as a shield against small particles, the spacecraft ascended through a gap between two of the rings, then spun around and fired its engine for more than 1½ hours to slow its acceleration.

The craft then rotated again to place its shielding antenna in front as it descended back through the gap.

The orbital insertion came after two decades of work by scientists in the United States and 17 nations. The $3.3 billion mission was funded by NASA, the European Space Agency and the Italian Space Agency.

David Southwood, director of space science for the European Space Agency, called it a "world mission" but said the orbital insertion was "America doing it right."

Cassini could have simply flown past Saturn if the burn failed to brake its acceleration properly.

"If you miss that operation the mission is lost — there was no alternative objective — it had to be successful," said Gaele Winters, the ESA's director of operations.

The maneuver had to be carried out automatically because Earth and Saturn are currently more than 900 million miles apart and radio signals take more than 80 minutes to travel each way.

Navigation team chief Jeremy Jones said initial analysis showed the orbit to be so good that a "cleanup" maneuver planned for Saturday would be very small.

"Look at that structure, it's so regular!" marveled imaging team leader Carolyn Porco as a picture came in showing well-defined bands of brightness and darkness. "I'm wondering if we're looking at a density wave. This looks like it might be a density wave, but I'm not quite sure."

Density waves, caused by gravitational interactions with nearby moons, are thought to be "kissing cousins" of the waves that produce the spiral structure seen in galaxies like Earth's Milky Way.

"These are regions where the rings are communicating gravitationally with the moons exterior to them," Porco explained.

Putting the first spacecraft into orbit around Saturn marked another major success this year for NASA, which has had two rovers operating on Mars since January and has a spacecraft heading home with samples from a comet encounter.

NASA Administrator Sean O'Keefe, in a call from Washington, D.C., Wednesday, called the orbit insertion an "amazing victory" and part of a "double header," following a successful spacewalk by the international space station crew earlier Wednesday evening.

One of the objectives of Cassini's ring research is to study density waves in unprecedented detail and based on the first set of images, scientists will not be disappointed.

"With these kinds of images and with the data we're going to return from Cassini with stellar occulation observations, radio occulation observations, we are going to nail density waves, we are going to understand these critters," Porco said. "This is really a new era in the study of outer planet systems."

A few moments later: "There goes another one, which is mind blowing, absolutely mind blowing," Porco exclaimed. "Look at that! Ooh... It's almost everywhere you look here, you can't miss one. They're just all over the place."

A few moments later: "Oh my God, look at that! ... These density waves are like books, just waiting to be read."

But as raw, unprocessed images flowed in, science wasn't the immediate objective. It was enough just to know Cassini's camera and other systems had worked as planned during close approach to Saturn.

The photo sequence began around 12:30 a.m. EDT, 18 minutes or so after Cassini finished a 96-minute rocket firing to brake into orbit around Saturn. Streaking just above the rings at speeds greater than 50,000 mph, Cassini's narrow-angle camera took a series of snapshots, opening its shutter for just five milliseconds per picture to avoid blurring.

Each picture was separated from those on either side by about 600 miles because of Cassini's extreme velocity.

"We couldn't take a contiguous ring scan with images overlapping other images because we are speeding across the rings very fast," Porco said. "It takes us about a minute to take a picture and so in the time we shutter the exposure, read out the camera and get ready to take a picture again, we have crossed a thousand kilometers. Our field of view is only about, let's say, 100 to 200 kilometers. So never do we have overlapping images. Never will we be able to put this all together in a nice mosaic."

One of the world's leading ring experts, even Porco was surprised by the level of detail apparent in the first unprocessed pictures.

"I shouldn't be, I suppose, but I am surprised," she reflected. "You can think about this like we have done for 14 years and you know, well, we'll get density waves there and we'll take pictures. But it's remarkable to me at how startling it is to see these images for the first time. ... They're just beautiful, they're very sharp."

CBS News Space Consultant William Harwood has covered America's space program full time for nearly 20 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.
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