Image: Monitoring Cassini
Armando Arorizo  /  Sipa Press
Workers at NASA's Jet Propulsion Laboratory monitor the progress of the Cassini spacecraft. After a seven-year journey, Cassini began orbiting Saturn late Wednesday and sent images of the planet's rings. staff and news service reports
updated 7/1/2004 7:13:10 PM ET 2004-07-01T23:13:10

Hours after settling into orbit around Saturn, the international Cassini spacecraft on Thursday sent back unprecedented glimpses of the planet's rings, revealing patterned waves that looked like ripples in a pond.

The pictures, which imaging team leader Carolyn Porco called "absolutely mind-blowing," capped a dramatic night for the mission's U.S.-European team.

Scientists and engineers breathed a sigh of relief late Wednesday at NASA’s Jet Propulsion Laboratory as a signal indicated first that Cassini — launched nearly seven years ago — safely passed through the ring plane and then performed a crucial engine firing. It squeezed through a gap in Saturn’s shimmering rings, fired its brakes and settled into a near-perfect orbit around the giant planet.

“I can tell you it feels awfully good to be in orbit around the lord of the rings,” said Charles Elachi, JPL's director and a member of Cassini's radar science team.

Images from 900 million miles away
Early Thursday, mission officials once again huddled in front of their screens as the first raw images came in from more than 900 million miles (1.4 billion kilometers) away.

“Wow, look at that scallop on the inner edge. That’s a beauty,” said imaging scientist Jeff Cuzzi as a picture from the sunlit side of the rings was displayed.

Video: Guided tour

Black-and-white images of the A ring, the outermost of Saturn's two brightest rings, showed patterns of ripples that scientists said were density waves, caused by the gravitational influences of the planet's moons.

Although the rings look like solid, flat doughnuts from Earth, they actually behave more like rivers of ice and rock, with particles ranging in size from dust specks to mountains.

"These density waves are like books, just waiting to be read," Porco said.

She estimated that some of the waves might measure as little as a quarter of a mile (half a kilometer) across. Earlier NASA probes had taken pictures of the rings as they flew by, but with nowhere near the resolution seen in the Cassini images. Some of the pictures had a resolution of 164 feet (50 meters) per pixel, Porco said.

“I'm surprised at how surprised I am at the beauty and the clarity of these images,” she told journalists. “They are shocking to me. ... They were so shocking I thought that my team was playing tricks on me and showing me a simulation of the rings and not the rings itself.”

'Amazing victory'
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.

In a telephone call from Washington, NASA Administrator Sean O’Keefe called the reaching of orbit around Saturn an “amazing victory” and part of a “doubleheader,” following a successful spacewalk by the international space station crew earlier Wednesday.

Image: Keeler Gap
An image of Saturn's rings, taken by the Cassini spacecraft and sent back Thursday, shows the Keeler Gap, close to the edge of Saturn's A ring. The ripples are density waves caused by the gravitational influence of Saturn's moons, scientists say.
A carefully choreographed maneuver allowed Cassini to be captured by Saturn’s gravity as it arced within 12,500 miles (20,000 kilometers) 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 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.

Two decades of work
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 will now go on at least a four-year tour of Saturn and some of its 31 known moons. Cassini was scheduled to make 76 orbits and repeated fly-bys of the moons.

Scientists hope the mission will provide important clues about how the planets formed. Saturn, the sixth planet from the sun and the second-largest, intrigues scientists because it is like a model of the early solar system, when the sun was surrounded by a disk of gas and dust.

For any astronomer who wants to study how planetary disk systems work, "this is the best place to go," Porco told journalists.

Cassini and the Huygens probe it carries are named for 17th-century astronomers Giovanni Cassini and Christiaan Huygens. Cassini discovered several of Saturn's moons, as well as a gap between Saturn's rings that now bears his name: the Cassini Division. Huygens discovered Titan, Saturn's largest moon.

The piggyback Huygens probe will be sent through Titan's atmosphere in January. The moon, blanketed by a thick atmosphere of nitrogen and methane, is believed to have organic compounds resembling those on Earth billions of years before life appeared. Scientists speculate that Huygens could well splash down into a lake or ocean of methane and ethane.

Controversial beginnings
Cassini was launched on Oct. 15, 1997, from Cape Canaveral, Fla., over the objections of anti-nuclear protesters who feared what might happen if the rocket exploded while carrying Cassini and its 72 pounds (33 kilograms) of plutonium, which powers the spacecraft. NASA insisted that the launch would be safe because of the numerous precautions taken with the poisonous substance.

Cassini has traveled 2.2 billion miles (3.5 billion kilometers), getting gravitational assists from Earth, Venus and Jupiter as it caromed around the solar system. The spacecraft took the roundabout route because it was too massive to be launched on a direct trajectory to Saturn.

Previous expeditions to Saturn have been brief: There were fly-bys by Pioneer 11 in 1979 and the Voyager 1 and 2 spacecraft in 1980 and 1981.

This report includes information from MSNBC's Alan Boyle and The Associated Press.

Photos: Best of Cassini

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  1. Starring Saturn

    This backlit view of Saturn was voted the favorite image to come from the Cassini orbiter - and it has been described as "perhaps the most stunning photograph ever taken." The image, captured on Sept. 15, 2006, shows two faint rings that were discovered by the Cassini team. And at the highest resolution, Earth itself appears as a pale blue dot just to the left of the brightest rings, at about the 10 o'clock position. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  2. Dark rings

    An infrared image from the Cassini orbiter, acquired May 24, 2007, reveals clouds beneath the hazes in Saturn's atmosphere, as well as the unilluminated side of the giant planet's rings. The shadows of the rings fall upon the planet's cloud layer. This image shares the honors as the favorite black-and-white picture from Cassini. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  3. Abstract art

    A Cassini image from May 10, 2006, shows the shaded edge of Saturn's disk, rounded by dark rings seen nearly edge-on. The crescent disk of Titan, Saturn's largest moon, can be seen in the background beyond the rings. This image shares the honors as the favorite black-and-white image from Cassini. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  4. Pearly moons

    Two of Saturn's moons - Tethys and Enceladus - look like pearls backdropped by the planet's disk in this image, captured on July 24, 2007. The thin "string" connecting the pearls is actually the plane of the planet's rings, seen edge-on. The rings cast a dark shadow on Saturn's disk. Two other moons appear in this image, although they can barely be made out at the highest resolution: Hyperion is near the lower left corner of the image, and Epimetheus is the slightest of specks between Tethys and Enceladus. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  5. Saturn from on high

    The Cassini spacecraft provides a high-contrast view of Saturn and its rings, as seen from above. This portrait is actually a mosaic of 36 images taken on Jan. 19, 2007, from about 40 degrees above the plane of the rings. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  6. Shadows on clouds

    Saturn's darkened rings cast shadows on the planet's blue and gold cloud tops, while the moon Dione hangs like a dot in the black sky beyond. This image was taken by the Cassini spacecraft on Feb. 4, 2007, from a distance of about 800,000 miles. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  7. View from below

    Cassini coasts beneath giant Saturn, staring upward at its gleaming crescent and icy rings. A great bull's-eye pattern is centered on the south pole, where a vast, hurricane-like storm spins. This view, obtained on Jan. 30, 2007, looks toward the lit side of the rings from about 26 degrees below the ring plane. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  8. Pastel planet

    Dark and sharply defined ring shadows appear to constrict the flow of color from Saturn's warmly hued south to the bluish northern latitudes. Scientists studying Saturn are not yet sure about the precise cause of the color change from north to south. The different colors may be due to seasonal effects on the atmosphere. The images that went into this mosaic were obtained by the Cassini spacecraft on Feb. 4, 2007. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  9. Ringing success

    This ultraviolet image from the Cassini spacecraft shows the detailed composition of Saturn's outer C and inner B rings from left to right, with the inner B ring beginning a little more than halfway across the image. The general pattern is from "dirty" red particles to the denser ice shown in turquoise as the ringlets spread outward. (University Of Colorado, LASP / AP) Back to slideshow navigation
  10. A is for amazing

    This ultraviolet image shows the A ring, beginning with a 'dirty' interior of red followed by a general pattern of more turquoise as it spreads away from the planet, indicating a denser material made up of ice. The red band roughly three-fourths of the way outward in the A ring is known as the Encke gap. (University Of Colorado, LASP - NASA / Reuters) Back to slideshow navigation
  11. Casting a shadow

    This image taken by Cassini shows the planet Saturn casting a shadow over its rings. (NASA - JPL - Caltech / Reuters) Back to slideshow navigation
  12. Titan revealed

    This is an infrared image of Titan, one of Saturn's moons, mapping the surface hidden beneath the moon's opaque atmosphere. Green areas represent water ice, while yellow areas have higher concentrations of hydrocarbons. The white spot is a methane cloud. (NASA) Back to slideshow navigation
  13. Ripples in the ring

    Scallops in the ring on the left side of this image were likely caused by a Saturnian moon rolling along the edge. One bright ringlet is visible within the gap, and at least one other faint ringlet can be made out. "This is textbook ring physics, right there, in one image," says Cassini imaging team leader Carolyn Porco. (NASA - SSI) Back to slideshow navigation
  14. Wisps in space

    A close-up of one of Saturn's rings shows a wispy pattern of ripples that may have been stirred up by a moonlet's orbit. Such unprecedented views of ring details are possible because of the Cassini camera's resolution. (NASA TV) Back to slideshow navigation
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