But it's not routine. At least not for the more than 5,000 people who, at one time or another, worked on the Cassini spacecraft mission. For them, it's a thrilling -- and perhaps traumatic -- end to a decades-long journey.
"I'm now carrying around an end-of-mission handkerchief to every interview," said Trina Ray, Cassini's Science Planning and Sequencing Team deputy. She joined the mission just before its launch in 1997. "It's part of being a part of an incredible thing, and of course, everybody is so proud of the team, of the spacecraft. There's a lot of pride in what we've done."
The fact that the Cassini mission lasted this long is a bit of a surprise in its own right.
"We should not forget that this is first and foremost an engineering marvel," said Jonathan Lunine, a professor at Cornell whose primary role with the mission is as interdisciplinary scientist for Titan's surface and atmosphere studies. He has been involved with Cassini since the 1980s. "I would never have expected that this would have lasted through to the late-middle part of my career."
The idea began in the mid-1980s, after the Voyager mission provided intriguing images from Saturn. It developed into a multinational endeavor that launched into space on October 15, 1997. It was supposed to last until only 2007, but two carefully planned extensions, and some impressive fuel management, allowed it to continue until September 15. Then, running on fumes, it will relay its final readings as it crashes through Saturn's atmosphere.
"You know, I'm starting to look at the fact we're vaporizing my beautiful spacecraft," said Todd Barber, lead propulsion engineer for the Cassini mission. He's been involved since 1997, six months before launch. "For the longest time, I was in stage 1 of grief: denial, a very beautiful comfortable place to be. But, you know, it's probably time to get through the other stages of grief and start planning for a future post-Cassini."
Shuttering a neighborhood
Cassini's final descent will bring a wealth of new data for scientists to push our understanding of our solar system, but September 15 also marks the end -- not just for a spacecraft launched 20 years ago but for many scientists and engineers who have dedicated decades to this project.
"That just really finally hit home that this is the end, and up to that point, there's always something look forward to," Lunine said. "But now we're really at the end, and I have mixed feelings. It has been a tremendous adventure. Cassini has accomplished enormous things. I've been privileged to be a part of that and to be able to do great science thanks to Cassini data, but it's tough now to think about the fact that it really is going to be over. For the first time really since I was a graduate student, there isn't another Cassini to look forward to."
Beyond the loss of the equipment and day-to-day tasks, staff members will have to say goodbye to each other.
"It's very much like a neighborhood, and here we are at the end of the mission, and the neighborhood is going to be dissolved, and that's a hard thing to think about," Ray said.
Working on the same project with the same people for such a long time naturally forms bonds. Birthdays are celebrated, weddings are marked, children are born, and deaths are mourned. The work begins to blend with the personal, and as the project ends, it's clear those involved are at a loss.
"I've not begun to process that part of the grief," Barber said. "I'm going to miss my Cassini coworkers terribly. They've been incredibly professional. It's a family away from home."
A unique work environment
The bonds created some unique memories -- including some impressive Halloween parties.
"We launched in October. Our official project color is orange, so Halloween is about the biggest holiday on Cassini," Barber said.
There's also a singing group who would make "Weird Al" Yankovic proud with their willingness to fit mission-related lyrics into popular songs.
"We've written over a hundred songs over the course of the 20 years, and it's always topical," Ray said.
But of course, the moments that stand out the most include the camaraderie forged as the mission revealed the unknown. Though it occurred nearly a dozen years ago, Lunine can still easily describe witnessing the first images the Huygens probe relayed after landing on Saturn's moon Titan.
"Being there with about 25 other people when these images suddenly started shooting across the computer screen -- no human being had ever seen this before, and the intensity of feeling and watching these images flash by as they were downloaded to us was the most memorable moment. It's burned into my memory."
Ray shares a similar moment from a 2004 flyby of Titan.
"They turned on the spigot, and image after image after image hit the screen, and nobody knew what we were looking at. Every expert in the world was in that room, and they were all pointing at the screen in stunned disbelief."
"I have never felt it was routine," Barber added. "I'm working my dream job since childhood. I can't believe there's not a hundred people lined up trying to steal this job from me. It's incredible."
A fitting end
"Cassini, to me, is the quintessential odyssey of discovery in it's very much like the voyage of Odysseus himself and his crew who could not have imagined that they would spend that much time at sea," Lunine said. "Cassini is the scientific real-life equivalent of that. We have spent 20 years in space, 13 of those years at Saturn discovering things about Saturn, its rings, its moons, its magnetosphere that we did not expect to see and did not expect to be able to follow up on."
Ray added, "I will miss Cassini telling me things about the Saturn system every day that we didn't know."
Despite her sadness, she is grateful for the journey.
"The focus really should be, I think, on how extraordinarily great this spacecraft has been and the people who built and operated her."
Barber agrees. For 20 years, Cassini was able to offer hope and wonder amid the bleak news on nightly newscasts.
"That just gives me tremendous pride to lift people up for that one minute and just show there's something beyond our petty problems on planet Earth, that there's this excitement and beauty in the cosmos."