Some five months before its demise, the Cassini spacecraft, which is managed for NASA by the Caltech-run Jet Propulsion Laboratory in Pasadena, sent data back to Earth Thursday following its first-ever dive through the narrow gap between the planet Saturn and its rings.
Science and engineering data collected during the spacecraft’s passage is being beamed back via NASA’s Deep Space Network Goldstone Complex in California’s Mojave Desert, JPL reported. The DSN acquired Cassini’s signal at 11:56 p.m. PDT Wednesday and data began flowing at 12:01 a.m. Thursday, JPL said in a statement.
More than 100 members of the Cassini team and their families were assembled in JPL’s Von Karman Auditorium to await the data and received it exultantly when it arrived from more than 750 million miles away.
“No spacecraft has ever been this close to Saturn before. 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,” said Cassini Project Manager Earl Maize.
“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.”
As it dove through the gap, Cassini came within about 1,900 miles of Saturn’s cloud tops, where the air pressure is 1 bar — a little less than the average atmospheric pressure on Earth at sea level — and within about 200 miles of the innermost visible edge of the rings, the statement said. Never before had the region been explored.
The gap between the rings and the top of Saturn’s atmosphere is about 1,500 miles wide. The best models for the region had suggested that if there were ring particles in the area where Cassini crossed the ring plane, they would be tiny, on the scale of smoke particles.
The spacecraft zipped through this region at speeds of about 77,000 mph so small particles hitting a sensitive area could potentially have disabled the spacecraft, the statement said.
To protect itself, the spacecraft used its large, dish-shaped high-gain antenna, which has a diameter of 13 feet, as a shield, orienting it in the direction of oncoming ring particles, it said. This meant that the spacecraft was out of contact with Earth during the ring-plane crossing, which took place at 2 a.m. PDT Wednesday.
Cassini was programmed to collect science data while close to the planet and turn toward Earth to make contact about 20 hours after the crossing, the statement said, adding that Cassini’s next dive through the gap is scheduled for Tuesday.
“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,” said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington.
Cassini was launched in 1997 and arrived at Saturn in 2004. Following its last close flyby of the large moon Titan on April 21, Cassini began what mission planners call its “Grand Finale.”
During this final chapter, Cassini loops Saturn approximately once per week, making a total of 22 dives between the rings and the planet, according to JPL’s statement. Data from this first dive will help engineers understand if and how they will need to protect the spacecraft on its future ring-plane crossings.
The spacecraft is on a trajectory that will cause it to plunge into Saturn’s atmosphere — ending Cassini’s mission — on Sept. 15, 2017, the statement said.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech in Pasadena, designed, developed and assembled the Cassini orbiter in addition to managing the mission.
—City News Service