Saturn probe Cassini is ready for its last hurrah

Space workhorse will send data right up to its fiery end

A long and illustrious career is about to come to a violent end for the Cassini spacecraft, which opened scientists’ eyes to some of the most life-friendly places in the solar system.

On Sept. 15, Cassini will dive into Saturn’s atmosphere, where the craft will disintegrate and melt in less than two minutes. A true professional, it will send information to Earth until the end, and researchers expect some of the most valuable data of the entire mission to emerge from the spaceship’s demise.

“The spacecraft has been used to its fullest,” Cassini program manager Earl Maize of NASA’s Jet Propulsion Laboratory said at a news conference Tuesday. “We will have it broadcast data back down to the very, very last minute.”

The $3.3 billion mission — paid for by NASA and European partners — launched from Earth in 1997. After a long journey though the solar system, Cassini spent a remarkable 13 years circling Saturn. Only NASA’s Voyagers probes have a longer track record among the spacecraft exploring the solar system beyond Mars, the Cassini team says.

Now Cassini is running low on fuel, so managers decided to have it self-destruct on Saturn rather than risk collision with its moons.

Since late April, Cassini has been enjoying a strenuous farewell tour of Saturn that saw the spacecraft dip repeatedly into the unexplored territory between the planet and its nested halos. On this “grand finale,” as NASA calls it, the ship has zipped through the gap between planet and rings 20 times, taking the first samples of both the rings and Saturn’s outer atmosphere. The craft also discovered that the planet’s atmosphere and rings are entangled in a complex relationship beyond what researchers had expected.

“Scientists love mysteries, and the grand finale is providing mysteries for everyone,” Cassini project scientist Linda Spilker, also of the Jet Propulsion Laboratory, said Tuesday.

The stream of scientific mysteries will begin drawing to a close Sept. 14, when Cassini sends its last images to Earth. At 4:37 a.m. ET on Sept. 15, the ship will begin what NASA calls “the final plunge.” It will swivel to give one of its instruments the best possible view of the atmosphere on the way down. A little more than three hours later, it will enter Saturn’s atmosphere.

The spacecraft will hit more than 400 degrees within seconds. In short order it will lose control,

“Scientists love mysteries, and the grand finale is providing mysteries for everyone.”

Project scientist Linda Spilker

lose contact with Earth, and begin to melt. First the outer shield, then the aluminum components and finally the parts made of iridium will burn away, vaporizing in perhaps a minute.

Scientists would love to have Cassini around for another decade. The hard-working ship has yielded hints of the rings’ age – preliminary data indicate they’re young — and helped reveal that Saturn’s tiny moon Enceladus has a subsurface ocean that appears hospitable to living organisms. After such a bounty of results, scientists are loath to say goodbye.

“This is in many ways a tough time,” said Spilker, who has worked on Cassini since 1988. On the other hand, “who knows what new mysteries the next two weeks will bring?”