Cassini returns images from first dive between Saturn and its rings
NASA’s Cassini spacecraft has successfully completed the first of its 22 Grand Finale dives between Saturn and its rings, sending back images and data after more than 20 hours of being out of contact with Earth.
The lack of contact was due to the spacecraft positioning its 13-foot (four-meter) dish-shaped high-gain antenna as a shield in the direction of tiny particles from the ring plane, which could disable the probe on impact as it sped by at 77,000 mph (124,000 km/h).
At 5 a.m. EDT (2 a.m. PDT) on Wednesday, April 26, Cassini began its plunge between the rings and Saturn, marking the first time any spacecraft has flown this close to the giant planet. Though confident the maneuver would succeed, mission engineers took special precautions to avoid possible risks. Computer models indicated particles in this region would be tiny.
Contact with Earth resumed at 2:56 a.m. on Thursday, April 27 (11:56 p.m. on Wednesday, April 26), when the spacecraft’s signals were picked up by NASA’s Deep Space Network Goldstone Complex in the Mojave Desert in California. Minutes after contact was re-established, Cassini began returning unprocessed images along with science and engineering data.
“In the grandest tradition of exploration, NASA’s Cassini spacecraft has once again blazed a trail, showing us new wonders and demonstrating where our curiosity can take us if we dare,” commented Jim Green, director of the agency’s Planetary Science Division.
Flying through the 1,500-mile (2,000-kilometer) gap between Saturn’s innermost rings and the top of its atmosphere (where the atmospheric pressure is about the same as it is at sea level on Earth: one bar), Cassini came within 200 miles (300 kilometers) of the rings’ innermost border and within 1,900 miles (3,000 kilometers) of the planet’s cloud tops.
Mission scientists and engineers will use data from this first dive through Saturn’s rings to gain a better understanding of how to protect Cassini during its future dives between the rings and Saturn, which will be conducted about once a week through September 15, starting with the second dive on Tuesday, May 2.
Close-up measurements made during these dives will yield data that will provide scientists with insight into Saturn’s mass and internal structure.
The probe’s last close flyby of Titan on Saturday, April 22, altered its trajectory, putting it on a collision course with Saturn’s atmosphere, which it will enter on September 15 as a means of avoiding potential contamination of moons Titan and Enceladus, which may be habitable, with bacteria from Earth inadvertently brought by the spacecraft.
“No spacecraft has ever been this close to Saturn before,” explained Cassini project manager Earl Maize of NASA’s Jet Propulsion Laboratory in Pasadena, California. “We could only rely on predictions, based on our experience with Saturn’s other rings, of what we thought this gap between the rings and Saturn would be like. I am delighted to report that Cassini shot through the gap just as we planned and has come out the other side in excellent shape.”
Raw images from the flyby are available here.
Video courtesy of NASA Jet Propulsion Laboratory
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.