Stone took the lead in tailoring the peer-review process to the faster pace of the mission’s planetary encounters: In the early afternoon, after the data was collected, teams of scientists decided what they thought would be their best results for that day they were and held firm. their conclusions for feedback to the entire science steering group.
Based on that discussion, Stone would choose the most interesting results to present to the media and public the next morning. Then the scientists honed their presentations that evening and even overnight—with Stone often pressing them to come up with analogies that would make the material more accessible to a lay audience—while a graphics team worked to put together supporting images. After the press conference the next morning, the trial 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 been the principal investigator of Voyager’s 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 resulted in better science. You need more than one piece of information to get a picture, and hearing the data from other scientists 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 feature – the direction of the magnetic field lines around Voyager – had not changed as significantly as scientists had expected.
The team remained confused for months until Voyager 1’s plasma wave instrument detected a significantly denser plasma environment around the spacecraft – the result of an accidental eruption of material from the Sun that set the plasma around Voyager 1 ringing like a bell. Stone gathered the team.
“No one could wait to enter interstellar space, but we wanted to do it right,” says Suzanne Dodd, who has overseen the engineering team at JPL as Voyager project manager since 2010. “We knew there would be people who would disagree. . So Ed wanted to understand the full story and the assumptions people were making. He listened carefully to everyone and allowed them to participate in the dialogue, without anyone monopolizing. Then he made a decision.”
Stone realized that the scientists did not have to fixate on the direction of the magnetic field lines. They were a proxy for the plasma environment. The team concluded that the detection of the plasma wave science instrument provided a better analysis of the current plasma environment and was evidence of humanity’s arrival in interstellar space.
Leading JPL
Voyager’s high profile also raised Stone’s profile. In 1991, about two years after the mission completed its planetary flybys, Stone became director of JPL, where he served until 2001. Under his leadership, JPL was responsible for more than twenty missions and instruments. Highlights during 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 outgrowth of the scientific questions raised by Voyager’s two flybys, and it carried the only probe ever to land in the outer solar system (near Titan).
The post-Cold War 1990s were an era of changing national priorities, with significant cuts in NASA and defense budgets. Stone 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 was more cost-effective and could still deliver high-impact science and stunning infrared images of the universe.
Travel to 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, he grew up in the nearby commercial center of Burlington.
Edward Stone Sr. was a building inspector who enjoyed 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 soon followed up with a request to let him use the school’s reel-to-reel tape recorder to work.
“I was always interested in learning why something is that way and not that way,” Stone said in an interview about this career in 2018. “I wanted to understand, measure and observe.”
His first job was at a JC Penney department store, where he worked his way up from warehouse to store clerk. He also made money playing the French horn in the Burlington Municipal Band.
After high school, Stone enrolled at Burlington Junior College to study physics, then attended the University of Chicago for graduate school. Shortly after he was hired, the Soviet Union launched Sputnik and the Space Age began.
“Space travel was a brand new field waiting to be discovered,” Stone recalled in 2018.
He joined a team at university that built scientific instruments for launch into space. The first one he designed rode aboard Discoverer 36, a 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 fogged 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 researcher and, along with Robbie Vogt, a colleague in Chicago, headed the university’s Space Radiation Lab. They worked closely on a number of NASA satellite missions, studying galactic cosmic rays and solar energetic particles. In 1972, Vogt recommended Stone to JPL leadership for the position of Voyager project scientist, which he held for 50 years.
Of Stone’s many awards, the most prominent is the National Medal of Science from President George HW Bush. In 2019, he won the $1.2 million Shaw Prize in Astronomy for his leadership of the Voyager project, which, as the citation noted, has “expanded our understanding of the four giant planets and the outer solar system over the past forty years.” , and has now begun exploring interstellar space.” He was also proud to have a high school named after him in Burlington, Iowa, as an inspiration to young students.