Before its destruction, the bus-sized Cassini spacecraft fought Saturn’s buffeting atmosphere to send back scientific data for even longer than NASA thought it would.
But the end was inevitable: Twenty years after its launch, and 13 years after its arrival at the ringed planet, the final signals from Cassini were received at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., at 4:55:46 a.m. PT today.
“I’m going to call this the end of mission,” Cassini project manager Earl Maize declared, during an early-morning webcast that was watched by tens of thousands. “Project manager, off the net.”
The end was pre-ordained days earlier, when a final maneuver put the spacecraft on a course to dive into Saturn’s upper atmosphere. NASA meticulously planned out the controlled descent to make sure there was no chance that Cassini could crash into one of Saturn’s moons, which are certain to be targets for future missions.
During the hours before the end, Cassini sent its last batch of images showing Saturn and its moons, and then it streamed back data from instruments that sampled Saturn’s atmosphere and its magnetic field.
Cassini’s engineers determined that the spacecraft would encounter so much aerodynamic stress during its 76,000-mph dive that it would break up and vaporize even before hitting Saturn’s cloud tops. NASA expected the final signal to be received back on Earth at 4:55:16 a.m. ET.
Telemetry indicated that the spacecraft put up a noble fight. During the webcast, one team member in JPL’s mission control room could be heard saying “Cassini is still there!”
The end came about half a minute later than NASA had anticipated.
After Maize declared the operational phase of the $3.3 billion mission to be finished, the room melted into hugs, applause, cheers and more than a few tears.
“The lucky peanuts were there,” NASA’s associate administrator for science, Thomas Zurbuchen, said later in reference to the traditional snacks laid out for key mission moments at JPL. “But there was a lot of Kleenex.”
Earth received @CassiniSaturn’s final signal at 7:55am ET. Cassini is now part of the planet it studied. Thanks for the science #GrandFinale pic.twitter.com/YfSTeeqbz1
— NASA (@NASA) September 15, 2017
“The spacecraft is gone,” Maize said at a post-mission news conference. “Thanks, and farewell, faithful explorer. But the legacy of Cassini has just begun. … Long live Cassini.”
Although Cassini is kaput, the mission is far from over for hundreds of scientists back on Earth. In the months ahead, the Cassini science team will pore over hundreds of gigabytes of data sent back by the spacecraft – images and readings that are likely to generate research papers for decades to come.
The readings are sure to include the atmospheric data from Cassini’s final minutes.
“Even in those last few seconds, Cassini managed to continue its rewriting of the textbooks and its legend,” JPL Director Michael Watkins said.
NASA’s next grand odyssey to the giant planets and their moons won’t get off the ground until the 2020s, when it’s due to launch a spacecraft to Europa, an ice-covered moon of Jupiter that’s thought to harbor a hidden ocean and perhaps even life.
But two of Saturn’s moons, ice-covered Enceladus and smog-covered Titan, are high on NASA’s list for future exploration because of their potential for undersea life and prebiotic chemistry.
“In the words of our former governor here, ‘We will be back,’” Zurbuchen said in Pasadena.
During today’s news conference, Maize provided a corrected figure for the expected loss of signal from Cassini, and this report has been revised to reflect that figure.
