A follow up.
Images back from Saturn
By John Antczak in California
July 2, 2004
Revealed ... a narrow angle camera image of Saturn's rings / AP
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 today.
The first shadowy close-ups of ring segments were taken from the US-European craft as it entered orbit late on Wednesday. As more and more pictures came in today, the images from the dark side of the rings gradually gave way to increasingly clear pictures.
Mission scientists and engineers at NASA's Jet Propulsion Laboratory had watched tensely late Wednesday as a signal indicated first that Cassini — launched nearly seven years ago — had 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," JPL Director and Cassini radar team member Charles Elachi said.
Mission officials huddled before a control room screen as the raw images came in today.
Some ring segments appeared as a bland haze. Others resembled ripples in water or crisp bands of light and dark.
"Absolutely mind-blowing," imaging team leader Carolyn Porco said as an image resembling tight-grained wood popped up.
"Look at that sharp edge. That brings tears to my eyes," Porco said. "Most of the structures we see, we don't know the cause of it. That's why we've gone back to Saturn."
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., on Wednesday, 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 on Wednesday evening.
A carefully choreographed maneuver allowed Cassini to be captured by Saturn's gravity as it arced close to 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.
The orbital insertion came after two decades of work by scientists in the United States and 17 nations. The $US3.3 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.
Cassini and the Huygens probe it carries are named for 17th century astronomers Jean Dominique Cassini and Christiaan Huygens.
The probe will be sent into the atmosphere of Saturn's big moon Titan 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.
Cassini was launched on October 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 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, getting gravitational assists from Earth and Venus 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.
On the Net: JPL:
http://www.jpl.nasa.gov
The Associated Press