NASA/Joel Kowsky
The Cassini spacecraft’s mission ended in seconds when its signal was lost after entering Saturn’s atmosphere in the early hours of 15 September. But saying goodbye has been a week-long process at Mission Control in Jet Propulsion Laboratories in Pasadena, California.
The beginning of the end started on 12 September with Titan’s “kiss goodbye.” Cassini made its last flyby of Saturn’s largest moon, using Titan’s gravity to steepen the spacecraft’s trajectory directly into Saturn’s maw.
Hours later, Cassini reached apoapse, the furthest point in its orbit before starting the 1.3 million-kilometer-long plunge into the gas giant. “It’s a roller coaster a million miles high. [Cassini]’s just falling, falling, falling with nothing in the way,” David Doody, Cassini real time operations engineer, explained to me when I arrived at JPL early the next morning.
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The sunny campus was bustling with visitors and media. Cassini team members gathered from all aspects of the mission, stopping to chat when they caught sight of a colleague. I sat with Julie Bellerose, the orbit determination lead on the Cassini mission, at a picnic table overlooking the busy courtyard. “It’s sad, but at the same time I’ll be able to breathe again when this is done,” she said.
But under the somber mood lay a twist of humour. When I stopped by Mission Control, I found a mockup of “Flying the Cassini Spacecraft for Dummies” on the desk of Cassini’s Mission Ace, the engineer who monitors the spacecraft in real time. When I visited again on Thursday, the room was fully-staffed with Cassini’s final team and the crew responded to our photos of them in their fishbowl by standing in unison to photograph us in return.
I found Bellerose on Cassini’s second-to-last shift, monitoring telemetry to ensure the spacecraft was still functioning perfectly. She waved at me through the glass, her earlier claims of needing a nap undercut by her cheerful enthusiasm. She was excited to actually see the thrusters fire in Saturn’s atmosphere, and to witness the force she’d used to guide Cassini through Saturn’s moons at work in the mission’s final minute.
I joined others to stand vigil for Cassini in the darkness of Friday morning at JPL while hundreds more of Cassini’s extended family gathered across town at Caltech. During NASA TV’s countdown to Saturn entry, scientists and engineers broke into cheers and applause each time one of their team appeared on the enormous screen dominating the auditorium.
Finally, it was time: Cassini’s radio heartbeat, its real-time scientific data streaming directly to the enormous Deep Space Network antenna in Canberra, Australia, jittered across the screen. The seconds ticked down to expected mission end, leaving a pregnant silence.
Then disbelieving, gasping whispers as the signal continued. A break, the signal was reacquired — was that Cassini’s thrusters fighting Saturn’s storms? — a break again, then it was lost forever.
Applause broke the silence, and quickly grew into a standing ovation in tribute to both the robot and human team that made it possible. So many who were so uncertain how they were going to feel found themselves overwhelmed with emotion. Proud, yet lost and saddened by the dissolution of not just the spacecraft, but their extended Cassini family.
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