Stone took the lead in adapting the peer-review process to the faster pace of the mission’s planetary meetings: In the early afternoon, after the data came in, teams of scientists decided what their best results were for the day and hung on. their conclusions for feedback in front of the entire scientific steering group.
Based on this discussion, Stone would select the most interesting results to present to the media and public the next morning. The scientists then refined their presentations that evening and even overnight—Stone often pressed them to come up with analogies that would make the material more accessible to a lay audience—while the graphics team worked to assemble supporting images. After the press conference the next morning, the process would start again. This cycle could continue daily for the duration of each planetary encounter.
“It was a very exciting time and everyone was making discoveries,” said Stamatios “Tom” Krimigis of the Johns Hopkins Applied Physics Laboratory, who has served as Voyager’s principal investigator for the Low Energy Charged Particle Instrument since the mission’s launch. “Ed’s approach showed us how much public interest there really was in what Voyager was doing, but it also led to better science. You need more than one piece of information to get a picture, and hearing about other scientists’ data helped us interpret our own.”
It was a process that continued to serve the Voyager team well in 2012 and 2013 as they debated whether Voyager 1 had left the heliosphere and entered interstellar space. Some signs pointed to a new environment, but one key indicator—the direction of the magnetic field lines around Voyager—didn’t change as much as scientists expected.
The team remained puzzled for months until Voyager 1’s plasma wave instrument picked up a significantly denser plasma environment around the spacecraft—the result of an accidental outburst of material from the Sun that set the plasma around Voyager 1 ringing like a bell. Stone assembled the team.
“No one could wait to get into interstellar space, but we wanted to do it right,” said Suzanne Dodd, who has served as Voyager’s project manager since 2010 and oversaw the engineering team at JPL. “We knew there would be people who would disagree. . So Ed wanted to understand the whole story and the assumptions that people were making. He did a good job of listening to everyone and letting them participate in the dialogue without monopolizing. Then he made up his mind.”
Stone realized that scientists did not need to fix the direction of magnetic field lines. They were representative of the plasma environment. The team concluded that the plasma wave science instrument’s detection provided a better analysis of the current plasma environment and was evidence of humanity’s arrival in interstellar space.
Front JPL
Voyager’s high profile raised Stone’s profile as well. In 1991, about two years after the mission completed its planetary flybys, Stone became director of JPL and served until 2001. Under his leadership, JPL was responsible for more than two dozen missions and instruments. Highlights of Stone’s tenure included the landing of NASA’s Pathfinder mission with the first Mars rover, Sojourner, in 1996 and the launch of the NASA-ESA (European Space Agency) Cassini/Huygens mission in 1997. The first Saturn orbiter, Cassini, was a direct result of the scientific question that arose of Voyager’s two flybys, and carried the only probe ever to land in the outer solar system (on Titan).
The 1990s was a period of change in national priorities after the Cold War, with significant spending cuts in NASA and defense budgets. Stone has restructured several missions to fly under these tighter cost constraints, including overseeing a redesign of the Spitzer Space Telescope’s cooling system so that it is more cost-effective and can still deliver high-impact science and stunning infrared images of space.
Journey into space
Edward Carroll Stone Jr. was born on January 23, 1936 in Knoxville, Iowa. The eldest of two sons of Edward Carroll Stone Sr. and Ferne Elizabeth Stone grew up in the nearby Burlington Mall.
Edward Stone Sr. was a construction supervisor who delighted in showing his son how to take things apart and put them back together—cars, radios, hi-fi stereos. When the younger Stone was in high school, the principal asked him to learn how to operate the school’s 16mm film projector, and a request to operate the school’s reel-to-reel tape recorder soon followed.
“I’ve always been interested in why something is the way it is and not the other way,” Stone said in an interview about that career in 2018. “I wanted to understand it and measure it and observe it.”
His first job was at JC Penney where he worked his way up from warehouse to sales clerk. He also made a living playing French horn in the Burlington Municipal Band.
After high school, Stone enrolled at Burlington Junior College to study physics and went on to the University of Chicago for graduate school. Shortly after it was accepted, the Soviet Union launched Sputnik and the space age began.
“Space was a whole new field waiting to be discovered,” Stone recalled in 2018.
He joined a team at the university that was building scientific instruments for launch into space. The first he designed was aboard Discoverer 36, the since-declassified spy satellite that launched in 1961 and took pictures of Earth from space as part of the Corona program. Stone’s instrument, which measured the Sun’s energetic particles, helped scientists figure out why solar radiation fogs the film and ultimately improved their understanding of the Van Allen Belts, energetic particles trapped in Earth’s magnetic field.
In 1964, Stone joined Caltech as a postdoctoral fellow and headed the university’s Space Radiation Laboratory with Robbie Vogt, who was a colleague in Chicago. They worked closely together on a number of NASA satellite missions, studying galactic cosmic rays and solar energetic particles. In 1972, Vogt recommended Stone to JPL management for the Voyager project scientist position, a position he held for 50 years.
Among Stone’s many awards, the National Medal of Science from President George HW Bush stands out as the most significant. In 2019, he won the $1.2 million Shaw Prize in Astronomy for his leadership of the Voyager project, which, as the citation noted, “over the past four decades has transformed our understanding of the four giant planets and the outer solar system, and has now begun to explore interstellar space.” He was also proud to have a high school in Burlington, Iowa named after him as an inspiration to young students.