Ed Stone, former JPL director and Voyager mission project scientist, in front of a model of one of the Voyager spacecraft. The gold plaque can be seen over his left shoulder. Credit – NASA/JPL Caltech
STeve Synnott never forgot the day he let Ed Stone name the moon. The year was 1980, and Synnott was a member of the navigation team of the Voyager 1 and Voyager 2 spacecraft that had just explored Jupiter. Stone was the scientist for the Voyager project: the head of the program, as NASA calls it. During the Voyagers’ flyby of the Jovian system, one of the ships captured an image – and then several images – of a small object orbiting the giant planet at a speed that completed more than one revolution every Earth day. Its size, speed, and altitude could mean it was only a moon.
Even a discovery this important didn’t mean that people like Synnott had left for Stone’s office; so the young engineer waited until the project chief was making one of his frequent walking tours of the Voyager bullpen, then approached him and showed it to him. It’s a letter he plans to send to the International Astronomical Union (IAU), which catalogs new space objects and approves the name an object will bear. Synnott handed Stone the one-paragraph correspondence and waited for the senior scientist to read it.
“Do you know the orbital period?” According to a conversation I had with Synnott while writing the book, Stone asked when he was done. Journey Beyond Selene.
“About 18 hours,” Synnott replied and handed Stone a sheet of calculations.
“His body?”
“About 60 miles.”
“Height?”
“One hundred and thirty-eight thousand miles.”
Stone reread the letter and then scanned the calculations again. “Well,” he said, smiling at last, “looks like you found yourself a month.”
Synnott smiled, sent his letter to the IAU, and eventually received a response with a list of mythological names he could choose for the moon. The nymph of the Greek god Zeus and the Roman god Jupiter settled in Thebe, and with that the solar system grew a little bigger.
Stone, who died of undisclosed causes on June 9, 2024, at the age of 88, after half a century at the helm of the Voyager program, could afford to be so generous with his time. Their Voyagers would ultimately discover 48 of them orbiting the four gas giants (Jupiter, Saturn, Uranus, and Neptune), as well as previously unknown rings or partial rings around Jupiter, Uranus, and Neptune, and volcanoes on the Jovian moon Io. The Voyagers were launched in 1977 and are currently traveling through interstellar space, beyond the boundaries of the solar system; still doing science, still beaming data back, outliving the man who midwifed them, flew them, and saw them through most of their lives. Great campaign until he retires in 2022.
“Ed Stone was a pioneer who dared to do great things in space. He was a dear friend to all who knew him, and a valuable mentor to me personally,” said Nicola Fox, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington, in an official statement. “Ed took humanity on a planetary tour of our solar system and beyond, and “It sent NASA where no spacecraft had gone before.”
Studying the orbits of the four outer planets, NASA astronomers discovered in 1966 that 13 years later, in 1979, the worlds would form a regular alignment and fall into a parade, allowing for a single transit every 176 years. one ship – or better yet, a pair of ships – to visit them all in one go. This gave the space agency 11 years to invent, build and launch the ships; let alone getting approval and funding for them in the first place. Things progressed fitfully during the project’s first six years, and so in 1972 NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, which was overseeing the mission, handed the reins of Voyager over to Stone, then a 36-year-old physicist. This was both a wise choice and a calculated gamble.
Read more: Starliner Takeoff is a Big Win for NASA
Stone had joined Caltech, which co-manages JPL with NASA, in 1964 to focus on space radiation. He has worked on several NASA satellite missions but has not yet held a leadership role. But NASA managers recognized his innate intelligence; Even before joining Caltech, he collaborated with the Department of Defense to design a spy satellite that both photographed the Earth and measured the solar wind (the flow of charged particles emerging from the sun) as a research bonus. The film on the spacecraft was forever fogged up by energetic storms. This kind of talent was exactly what was needed for Voyager, but it was unknown whether Stone had the leadership skills to run the program. It turned out that it was.
Stone helped secure financing and advance engineering for the Voyager project; especially by repeatedly emphasizing to both lawmakers and engineers that if NASA does not take advantage of planetary alignment now, it will have to wait until 2153 for the next project. shot. Ultimately, both spacecraft will lift off on time, with Voyager 2 leaving the Florida launch pad first on August 20, 1977, and Voyager 1 – flying slightly faster and in a slightly shorter orbit and thus being the first to reach Jupiter – on August 20, 1977. . September 5, 1977.
Even then, there was no guarantee that NASA’s budget would support a visit to all four planets over a 10-year period, and officially Jupiter and Saturn were the only worlds included in both spacecraft’s itineraries. This being the case, Stone decided to actually throw away one of his ships. When Voyager 1 reached Saturn, it changed its orbit to swing below the ringed planet and then fly upward; thus putting it on course for a flyby of Saturn’s giant moon Titan (a world covered in organic methane and a thick fog). Ethane has long fascinated scientists. Once on this route, however, the spacecraft would not have enough fuel to reverse course and would therefore fly out of the plane of the solar system.
Voyager 2, which also flew past Jupiter and Saturn, would have continued to fly level and could have made close approaches to Uranus and Neptune if it had the will and wallet to allow the missions. While Stone maintained the spacecraft, NASA brass managed their budgets and ultimately won the funding to enable Voyager 2 to fly. On January 28, 1986—poignantly, the same day the shuttle Challenger exploded—Voyager 2 passed by Uranus, surveyed the planet’s largest moons, discovered 11 new moons, and mapped its thin rings. As the ship passed by Neptune on August 25, 1989, it discovered two new moons, five thin rings, and an Earth-sized bruise in the atmosphere known as the Great Dark Spot, a giant storm with winds reaching 1,600 kilometers per hour. Icy geysers have also been discovered on Neptune’s moon Triton. Voyager 2 remains the only ship to visit these two worlds.
Even then, the Voyagers weren’t done, and neither was Stone. The spacecraft are powered by radiothermal generators that can provide energy for 50 years or more, and although they are transmitted back to Earth by a signal with less wattage than a refrigerator bulb, they can continue their operation by accelerating to the limit of solar energy. system and then exiting. Voyager 1 entered interstellar space on August 25, 2012 and has now reached a distance of more than 15 billion miles. (24 billion km) from Earth. Voyager 2 left the solar system on November 5, 2018 and is more than 12.5 billion miles away. (20 billion km) away. Both ships continue to whisper to us in low voices.
Read more: ‘Parade of Planets’ is Coming. Here’s How to Watch This Sky Show.
Stone would be distinguished by much more than just the Voyagers. He was director of JPL from 1991 to 2001 and was at the helm when the Sojourner spacecraft (the first Mars rover) touched down on the Red Planet in 1997. Overall, he served as principal investigator on nine NASA missions and co-investigator on five others. .
However, the group for which he is best known is the Voyagers. The ships are famous for carrying golden records created by another lost space legend, Carl Sagan. If an alien civilization found the spacecraft and played records on a simple turntable (the state of Earth art at the time of the ship launches), they would see 119 images of our planet and hear greetings in 55 languages. 27 musical selections including Javanese, Japanese, Chinese and Peruvian music; Examples from Bach, Mozart and Beethoven; also “Johnny B. Goode” by Chuck Berry and “Melancholy Blues” by Louie Armstrong and the Hot Seven Band.
In 1978, when Voyagers was still new and Stone was still relatively young, Saturday Night Live announced that an alien civilization had intercepted the ships, played the recordings, and sent back a four-word message. An image from that week’s TIME magazine cover, showcased by host Steve Martin. The four words were: “Send More Chuck Berry.”
History does not record whether Ed Stone watched that night, but it is likely that he saw the sketch in due course and laughed. And then he went back to work. The Voyagers were still flying, which meant it was still working. He continued this except for the last two years of his life. His ships, now interstellar ambassadors of the human species, sail without him. Ed Stone, for God’s sake.
Write to: Jeffrey Kluger at jeffrey.kluger@time.com.