Cassini is one of NASA’s biggest success stories to date. After nearly 20 years of hurtling through space to study Saturn and its moons in more detail than humans ever thought possible, the little spacecraft that could will finally come to the end of its mission on Friday in the most spectacular fashion possible: a bittersweet plunge into the depths of Saturn’s atmosphere, collecting unparalleled data about Saturn’s physical and chemical makeup as it rapidly disintegrates bit by bit into dust.

“It’s just been almost flawless,” said Earl Maize, the program manager for the Cassini mission, told reporters Wednesday. “This spacecraft … I couldn’t have asked for anything more.”

The little bugger is less than 48 hours away from its last operation, “about to come to a fiery and high-above-the-clouds end,” says Maize. “We’ll be saddened, there’s no doubt about it. But all of us are going to have a great sense of pride. We did it, and we did it extremely well.”

There is really no overstating just how consequential Cassini has been for space exploration. The spacecraft has snapped up over half a million images of Saturn and its moons. Its most famous is “The Day the Earth Smiled,” a July 19, 2013 photograph of a dotty little Earth sitting in the background of Saturn and its massive rings:

The Day the Earth Smiled
Earth can be seen as a blue dot underneath the rings of Saturn in "The Day the Earth Smiled," taken by the Cassini spacecraft on July 19, 2013.

Part of its work has also been opening up NASA’s eyes to the incredibly vibrant Saturnian moons of Enceladus and Titan — both of which have piqued the interest of the world’s astrobiologists and raised hopes that there many be alien life here within the solar system itself.

As a result, NASA is very eager to quickly follow this project with bigger investigations of Saturn and its moons.

“We gotta go back.”

“We left the world informed but still wondering. We gotta go back, and we know it,” Maize said today.

The suicidal end for Cassini isn’t simply to collect as much direct data as possible about Saturn’s atmosphere, but also to ensure sterility of the solar system. Cassini, as a human-built spacecraft, could be carrying any number of microbes or organic particles endemic to Earth, and those things could have survived through the deep freeze and vacuum of space. By sending Cassini toward a fiery death, NASA is ensuring that there is no possibility — however small it might be — the spacecraft could contaminate other celestial bodies in the solar system or elsewhere, as part of its planetary protection directive.

“Because of planetary protection,” said Jim Green, NASA’s Planetary Science Division director, “and our desire to go back to Enceladus, and back to Titan, and back to the Saturn system, we must protect those bodies for the purpose of future exploration.”

cassini last operation
The end of times for Cassini.

The 13-year tour of the Saturnian system ends in six steps on Friday:

  • 4:37 a.m. Eastern: The spacecraft initiates the beginning of its swan dive into Saturn, kicking off with a five-minute roll to optimally calibrate its instruments for the atmosphere. In particular, the Ion and Neutral Mass Spectrometer (INMS) instrument will make sure it’s focused directly ahead, towards the atmosphere.
  • 7:53 a.m.: About 1,190 miles above the planet’s cloud tops, Cassini trudges head first into Saturn’s atmosphere at about 10 degrees north latitude, with thrusters firing off at 10 percent capacity. The spacecraft’s high-gain antenna continues to point towards Earth transmit data.
  • 7:54 a.m.: Cassini’s thrusters dial up to 100 percent capacity, and the atmospheric forces of Saturn start to mess up the spacecraft’s orientation and direction — which is traveling about 76,000 mph at this point.
  • 7:55:06 a.m.: The mission will finally come to an end when the high-gain antenna will lose its lock on Earth. About 940 miles above Saturn’s cloud tops, communication with Cassini will terminate.
  • 7:55:36 a.m.: The spacecraft will start to come apart piece by piece, burning up the same way a meteor might as it dives into Earth’s atmosphere.
  • 7:57 a.m.: Cassini will be no more. “It will be completely vaporized,” said Maize.

Gone, but not forgotten. “Thank you, Cassini,” said Maize near the end of the conference. “And farewell.”


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