Dr. Edward (Ed) Stone. Credit: Caltech
Edward C. Stone, renowned for his leadership of the Voyager spacecraft missions and his role in advancing space and planetary astronomy at Caltech and W. M. Keck Observatory, establishing the Institute’s Space Radiation Lab, serving in distinguished leadership roles, and paving the way for the next generation of giant telescopes.
Dr. Stone in his office. Credit: Caltech
Legacy in Space Exploration
Stone was perhaps best known for his role as project scientist for 
Dr. Stone in a classroom. Credit: Caltech Archives
Leadership at JPL and Beyond
In 1991, Stone was named director of the Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA. He remained in that role until May 2001, during which time he oversaw 21 different missions and instruments, including the 
Dr. Stone with the Voyager scale model. Credit: Mario de Lopez for Caltech
Pioneering Ground-Based Astronomy
Stone’s work to open the farthest reaches of space to exploration went beyond space missions. From 1983 to 1988, he served as chair of the Division of Physics, Mathematics and Astronomy at Caltech. While in that role, he oversaw the establishment of the Laser-Interferometer Gravitational-wave Observatory (Thirty Meter Telescope (TMT), a giant telescope proposed to reside, like Keck, atop Maunakea in Hawai’i. Stone joined the TMT Corporation in 2004, and became the founding executive director of the TMT International Observatory LLC in 2014, a role he remained in until 2022.
“It is hard for me to think of any scientist today with a scientific legacy as broad and multifaceted as Ed’s,” says Fiona A. Harrison, the Kent and Joyce Kresa Leadership Chair for the Division of Physics, Mathematics and Astronomy, and Harold A. Rosen Professor of Physics. “He made major contributions to cosmic ray and space physics, planetary exploration, solar physics and ground-based astronomy. His knowledge was encyclopedic and his enthusiasm for exploring the cosmos unbounded. Personally, he influenced me profoundly as a mentor, colleague, and co-leader of the Space Radiation Lab and I already miss his advice and friendship tremendously.”
Early Life and Education
Born in Knoxville, Iowa, on January 23, 1936, Stone grew up on the banks of the Mississippi River in nearby Burlington, Iowa, and received his undergraduate education at Burlington Junior College (now Southeastern Community College). “Our father was a construction superintendent who enjoyed learning new things and explaining how they worked,” he wrote in an autobiography upon being awarded the 2019 Shaw Prize in Astronomy, a prestigious honor bestowed for his leadership in the Voyager project.
“As a homemaker, our mother created a warm, welcoming, and nurturing space for our family,” Stone wrote. “Both parents had a strong work ethic… They encouraged my pursuit of scientific and technical activities such as building radios and other electronics. My physics teacher further advanced my scientific and laboratory experience and it was due to his urging that I enrolled at the Space Radiation Lab at Caltech, which continues to play a key role in many astrophysics space missions.
In 1972, managers at JPL offered Stone the position of project scientist of the Voyager mission.
“I have known Ed Stone for 57 years and I worked closely with him on almost a daily basis for the last 51 years. I feel he is the smartest man I ever met,” says Alan Cummings, senior research scientist for the Space Radiation Lab. Cummings began working alongside Stone as a graduate student in the 1960s. “He was a tremendous scientist, as evidenced by him winning the Shaw Prize, among other awards and honors. He was a great multi-tasker, for example, being JPL director for 10 years while at the same time working with me on a daily—well, mostly nightly—basis on our Voyager data. He was my boss, my colleague, and my friend, and I will miss him tremendously.”
A Grand Tour
The Voyager mission was designed to take advantage of a rare alignment of video commemorating the 40th anniversary of Voyager. “Time after time, we just found that nature was much more inventive than our models.”
Master of Space Missions
In addition to managing many missions while director of JPL, Stone also helped restructure several projects to keep them afloat in the midst of funding cuts. In the 1990s, after the Cold War, NASA and defense budgets were significantly cut. During this time, Stone oversaw the redesign of the cooling system on NASA’s infrared observatory, the Spitzer Space Telescope, making it more cost effective. As a result, Spitzer operated from 2003 to 2020, and made countless discoveries, such as revealing that the TRAPPIST-1 system contains seven Earth-size planets.
Beyond his administrative duties at JPL, Stone served as either a principal investigator or science instrument lead on nine NASA missions and as a co-investigator (a significant science instrument team member) on five others. One of these missions, the Parker Solar Probe, which launched in 2018, continues to whip around the Sun to study the source of its solar wind—the same wind that carves a bubble, called the heliosphere, around the Sun, from which Voyager 1 and 2 escaped. “In 2012, Voyager 1 finally left the bubble first predicted by Parker, entering interstellar space,” Stone said in a Caltech feature story about the mission, which is named after Caltech alumnus Eugene Parker (PhD ’51).
Suzanne Dodd, who has served as Voyager project manager since 2010, recalls Stone’s calm and collected management approach, in particular during a time when data from Voyager 1 indicated that the spacecraft had indeed crossed into interstellar space.
“Nobody could wait to get to interstellar space, but we wanted to get it right,” Dodd recalled. “We knew there would be people who disagreed. So Ed wanted to understand the full story and the assumptions people were making. He did a good job listening to everybody and letting them participate in the dialogue without anyone monopolizing.”
Stone has received numerous awards, including the National Medal of Science (1991), the Magellanic Premium (1992), the Carl Sagan Memorial Award (1999), the Philip J. Klass Lifetime Achievement Award (2007), and the Howard Hughes Memorial Award (2014). In 2013, on the show “The Colbert Report,” late-night TV host Stephen Colbert presented Stone with the NASA Distinguished Public Service Medal, the agency’s highest honor for a nongovernment individual. Stone was a member of the National Academy of Sciences.
Stone was predeceased by his wife, Alice, and is survived by his daughters Susan and Janet, son-in-law Tom, grandsons Michael and Ryan, and granddaughter-in-law Lauren. A memorial service will be held at a later date. In the meantime, Stone’s family suggests those wishing to celebrate his life might “explore an unfamiliar realm of science, enjoy an opera, hike with family and friends, share a stovetop pan of fresh popcorn, or adventure along a new route home.” In lieu of flowers, the family suggests donations to Caltech’s Summer Undergraduate Research Fellowships (SURF) program, the Planetary Society, or the Los Angeles Opera.
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