RING AROUND SATURN
What’s Next for NASA’s Cassini Mission Space Explorers?
David Doody went from dreaming his rocket ship in his backyard was going to Saturn to actually directing Cassini toward the ringed planet. The mission is over. What happens now?
In 1997, we knew next to nothing about Saturn. Flybys by the spacecraft Voyager almost two decades earlier hinted at watery moons. Saturn’s largest moon, Titan, was covered in a thick atmosphere, unlike any other moon in our solar system.
But all that changed in 1997, when NASA launched the Cassini spacecraft from Earth. It loop-dee-looped around Venus twice, then past Earth one last time. With each planetary flyby it stole a little gravity, enough to increase its speed, getting it to Jupiter where it would do one final accelerated shot outwards to Saturn.
For the next 13 years, Cassini swooped through rings and swung past moons, giving us a profound view of the planet we had only seen as a tiny speck in the sky.
And none of that would have been possible without David Doody.
David Doody had been dreaming of going to space since he was a little boy in Teaneck, New Jersey. When he was 6 years old, Doody was gifted a two-story rocket ship that his father and grandfather built out of plywood. That rocket ship towered over their backyard fence and became a neighborhood spectacle: Drivers stopped and got out of their cars, lines of onlookers formed, neighbors gawked as they walked their dogs. After school, he and his friends would climb inside the spacecraft, turn the dials, fire the engines, and (coincidentally) head out to Saturn.
By the time he was 17, Doody had a plane and a pilot’s license. The sky was his, and he took to it like a natural, eventually joining the Air Force. After his service, Doody became a flight instructor for Japan Airlines for a decade, before he and his partner decided to sell everything they owned to live on a sailboat on Santa Catalina Island off the coast of Southern California.
But Doody was restless. It was 1983 and between snorkeling shifts and some odd computer jobs, Doody came upon a newspaper ad looking for a deep space network instructor (“I had no idea what the job was,” he recalled, “but it had the word space in it”). He applied—and got the job. For the next two years, Doody helped build simulations for Voyager’s visits to the outer planets using a system of large antennas around the world responsible for communicating with all spacecraft in deep space called the Deep Space Network, or DSN.
After his DSN contract was completed, Doody was hired as a contractor to help command the spacecraft on its first outer planet visit: the Uranus encounter, which started on Jan. 24, 1986. It swooped by, skimming the cloud tops at just 50,000 miles above the surface. It was a huge moment for both Doody and Voyager: No spacecraft had ever been this far out in our solar system before. Doody—and Voyager—had passed the first outer planets test.
In 1987, after the success of the Uranus flyby, NASA posted a job opening for “real time operations” for the Voyager mission. The agency needed someone to command Voyager and to manage the data coming down during its final and most risky planetary encounter—the flyby of Neptune.
When Doody went in for his interview at NASA’s Jet Propulsion Laboratory, he told them he was perfect for the job. “I would not rest until they hired me,” he told The Daily Beast.
And he was perfect for the job. They thought so too, so they hired him. He would now command Voyager full time—and along with that job came the coveted title of ACE.
For the uninitiated, a spacecraft ACE is the messenger for a mission. Think of an ACE like the Greek god Hermes. In ancient Greece, when a god needed a message delivered quickly, Hermes was called. His job was to not only send and receive messages; he was a bringer of dreams. In this way, a spacecraft ACE is no different. Voyager was crossing billions of miles of cold, vast expanses of space. Our dreams were tied to Voyager, so we traveled alongside it watching and waiting.
Around the same time that David Doody became an official NASA employee, Richard Stevenson began working as a DSN operator at the Canberra center in Australia, using the simulations that Doody created in preparation for the Uranus and Neptune encounters. (Doody and Stevenson both realized after this interview that they’d probably spent more time on the phone with each other over their lifetimes than they have with their own families, but they didn’t know each other’s names until this piece. Over the last 30 years and three missions they’ve shared, they’ve simply been ACE and the DSN.)
“Imagine every team member standing behind the console in mission control,” Stevenson said about how vital the ACE is to a mission. “They’ve all worked for weeks or months on building commands for the spacecraft, they pass that information to the ACE. The ACE then presses that button that sends it straight to the Deep Space Network and right on up to the spacecraft. No matter how many people are behind a mission, there is only one person who ever talks to the spacecraft, and that is their ACE.”
Doody had aced Uranus, but a daunting challenge lay ahead: Voyager’s final planetary flyby of Neptune in August 1989. NASA had one chance to get this flyby right: The spacecraft had traveled for 12 years and billions of miles for the few hours it would take to get as much information about this planet as we could.
On Aug. 25, 1989, Voyager successfully flew past Neptune, completing the journey of the Voyagers and their tour of every planet in the solar system.
The mission was over, but Doody had just begun his planetary journey. In 1990, the Magellan mission was ready to launch to Venus and in need of a seasoned ACE. Magellan was a complicated mission with communication system kinks. Doody was the guy.
After nearly four-and-a-half years in orbit, Magellan was sent to crash into Venus. It was the first spacecraft Doody lost to deorbiting (or sending the ship to impact the host planet, exploding it into a thousand pieces), but it wouldn’t be the last. He didn’t have long to grieve, though. There was a new big shot mission in town: Cassini.
Cassini was the ultimate planetary mission, sent to Saturn to find answers. Previously, our knowledge of this ringed gas giant and its mysterious moons were limited to data only acquired during the brief Voyager flybys in the late 1970s and ground-based observations.
When it finally arrived at Saturn on June 30, 2004, it needed to begin the maneuver to enter into orbit. Doody recalls what a nervous wreck he was.
“My team had sent the commands to the spacecraft,” he recalled. “They were on the spacecraft ready for arrival. But then we had to turn the spacecraft to the attitude that it needed to fire the engines, so you lose the constant downlink of all the measurements, and you’re left with only one thing and that is a weak signal from a small antenna.”
The mission and its team of ACEs lived and worked at a single desk lined with seven computer screens and glowing blue and purple lights, with a bright blue neon sign that read “CASSINI MISSION ACE.” There were no joysticks or knobs, just stacks of papers, clipboards, headsets and manuals (including one titled Flying Spacecraft for Dummies).
For 20 years, every time the spacecraft called home or uploaded new commands there was at least one ACE running the console and present. Cassini continuously sent back 13,000 engineering measurements daily. The ACE knew what the temperature was on the left side of the spacecraft and the right side, how its computers were functioning, if the camera had a movement issue.
After 13 flawless years in orbit, Cassini was low on fuel and getting worryingly old. There was a chance microbes from Earth were still present on the spacecraft, which put Saturn’s possibly habitable moons, Enceladus and Titan, at risk. The team had no other choice to but give Cassini a send-off worthy of a mission of this caliber. On Sept. 13, 2017, at 3:53 a.m. PST, after half a million images, 13 years of precise measurements, and 20 years after its mission first began, one of Doody’s fellow Cassini ACEs, Michael Staab, uploaded the very last command Cassini would ever receive—a command that would trigger the spacecraft to fire its thrusters, setting it on an irreversible collision course with Saturn.
But it would take two more days to watch Cassini die.
Cassini’s last moments were extraordinary. On the evening of Sept. 14, the spacecraft sent back its last series of images, a grand family portrait of Titan, Enceladus, and a close up of Saturn's rings.
Early on the morning of Sept. 15, the signal jumped up and down, then up and up and down again, until finally the confirmation of Cassini’s death came when the S-band from the DSN center in Canberra fell flat. Time of death was called on Sept. 15 at 4:55 a.m. Pacific time.
Doody was right there watching. “I don’t know how to describe it,” he said. “It was certainly a clear-cut ending… with no more flight. I was right there until the very moment. I don’t really have any words for it. It's satisfaction, to have contributed a bit to a very successful project, and gratitude that team members and management trusted me enough to have me participate.”
It’s been 11 months since Cassini ended. What happens to the five Cassini ACEs? What happens to their desks? Where do all the people go when they’ve spent 20 years all orbiting the same planet only to have their jobs completed? Since September 2017 two of the mission’s ACEs have “gone to [work at] Mars,”two team members have retired, one went to work for the Deep Space Network, and another is helping Doody catalog the spacecraft data and finish documenting everything that happened before the binders are closed and placed on the shelves alongside every other mission that has launched and ended.
Doody now serves as a sort of documentarian for the mission, spending his days organizing the notes from the last 20 years, making sure the legacy of Cassini is accurate.
“One of the first things that I had to do was to make sure that the ACE’s logs were edited and stored and archived in a way that’s readable,” Doody said. “We had 8,700 DSN passes (or, 8,700 phone calls with the spacecraft), and during each pass there was an ACE taking notes like ‘OK, there was a signal acquired’ constantly, hour after hour throughout the whole flight.’”
The Cassini console in mission control is empty now. “The computers I left on for as long as it made any sense,” he said. “We had the screens up that showed the last data coming in from Cassini just before it turned away and burned up, that was sitting there for weeks and weeks and then it made sense. Somebody needed this computer and someone needed that computer so it has been almost completely dismantled.”
The empty desk is a reminder for Doody and the many people who work inside mission control, that the spacecraft they worked with for 20 years is gone. And while Doody doesn’t have a mission flying right now, he still oversees the ACEs and real-time operations inside Mission Control for our other robotic explorers. It’s been a good 31 years in the Center of the Universe, but Doody isn’t quite done.
“I do not want to retire,” he said. “When I first joined Cassini, I learned enough to realize that the real time team is exactly where I wanted to be.”
In the evenings, when the southern California skies are clear, Doody takes his Dobsonian telescope onto the streets of old town Pasadena not far from JPL, along with a whiteboard with the viewing menu du jour. “For a while we were looking at Saturn,” he says. But lately the whiteboard has read: “Today we are looking at Europa.”