Cassini Spacecraft Enters Saturn’s Orbit
PASADENA, Calif. – Just hours after swooping into orbit around Saturn, the Cassini spacecraft sent images of the giant planet’s rings back to Earth early Thursday.
The shadowy close-ups were taken as the U.S.-European craft looked down on ring segments as it entered orbit late Wednesday. The most detailed initial image showed a crisp group of more than a dozen tight bands.
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.
As the first images became available Thursday, imaging team leader Carolyn Porco said the pictures would become more dramatic as Cassini’s view changed to the side of the rings illuminated by the sun.
“It was an amazing opportunity to be this close,” Porco said.
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.
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 1 1/2 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 $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.
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 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 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 22-foot-long, 13-foot-wide spacecraft took the roundabout route because it was too massive to be launched on a direct trajectory to Saturn.
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