Edward Stone, who piloted NASA's Voyager spacecraft to distant planets, has died at the age of 88.

And it was his death Announced before California Institute of Technology, where he was professor emeritus of physics, And by NASA's Jet Propulsion Laboratory, which he directed for 10 years starting in 1991. His daughter, Susan Stone, said he was in failing health but the cause of death was not yet known.

Dr. Stone began his career in physics at the dawn of the Space Age, turning his attention to the universe after the Soviet Union launched Sputnik — a shiny metal ball that became the world's first satellite — while he was a graduate student at the University of Chicago in 1957.

Over the next six decades, he designed some of the first scientific instruments for American satellites; He oversaw the construction of the W.M. Keck Observatory, which housed the world's two largest optical telescopes when it was completed in Hawaii in the mid-1990s; He led the creation of LIGO, a billion-dollar physics experiment that in 2015 provided the first direct observations of gravitational waves, ripples in space-time that had eluded scientists for years.

He remained known for his work as project scientist — and, less formally, keynote spokesman — for Voyager 1 and 2. Launched two weeks apart in 1977, five years after Dr. Stone was assigned to the mission, the two stunning probes returned images of giant exoplanets and their moons, as well as A wealth of data about the solar system.

“We were on a mission of discovery,” he told the New York Times. In 2002, looking back at the origins of the project. “But we did not estimate the scale of discovery that would occur.”

Both spacecraft visited Jupiter and Saturn, with Voyager 2 continuing to reach Uranus and Neptune, aided by a rare exoplanet alignment that occurs once every 176 years. The one-ton probes are now traveling further through interstellar space than any other man-made object in the universe. In addition to cameras and scientific instruments, each of them carries a heavenly message in a bottle: A Gold plated recordDesigned with the help of astronomer Carl Sagan, it carries sounds and images that would introduce would-be aliens to the diversity of life on Earth.

“It was a great idea,” Dr. Stone told the Los Angeles Times in 2011, contemplating the registry inclusion as Voyager 1 was preparing to enter interstellar space. “At the time, just getting to Saturn was what I was focused on.”

Beginning in 1979, probes took the first close-up images of Europa, one of Jupiter's moons, revealing the cracked, broken surface of a frozen world that “resembled an ice block,” as Dr. Stone put it. They studied Saturn's vast ring system. Evidence of a thick atmosphere rich in organic compounds found on Saturn's moon Titan; Track the 1,000 mph winds blowing on Neptune's surface; It discovered five-mile-long hot springs erupting from the icy surface of Neptune's largest moon, Triton.

Among the mission's most surprising early results was the detection of volcanic activity on Jupiter's moon Io. It was the first time active volcanoes spewing ash out of Earth had been discovered, and it surprised scientists who had assumed the Moon would be much like Earth — inert, cratered, cold, and dead.

“Time and time again, we discovered that nature was more innovative than our models,” Dr. Stone said in an interview with Caltech.

When Voyager passed the outer planets, Dr. Stone appeared on the evening news and gave frequent interviews. While supervising 11 investigation teams and about 200 researchers, he was credited with accelerating the pace at which the team's scientists reported their findings, leading daily meetings in which he sought to identify the group's most striking findings, and then working with the researchers to help reach a conclusion. The materials are accessible to the general public.

“He was such a machine,” his former boss Norman Haynes, who served for three years as general manager of the Voyager project, told the New York Times. In 1990. “You'll finish him off and make him bigger! He's been running around all day getting things done.

Astronomer Bradford A. said: Smith, who led the team that interpreted the Voyager images, told the newspaper In 2002 The deluge of images and data sent back by the probes made Voyager “NASA's most successful mission” — praise that has been echoed by many scientists over the years.

“What we know about exoplanets is a direct result of Ed Stone's contribution,” said A. Thomas Young, former director of NASA's Goddard Space Flight Center, He once said. “He was one of two or three people who made Voyager tick.”

Voyager's success helped launch Dr. Stone into wider prominence, leading to his appointment as head of the Jet Propulsion Laboratory, or JPL, the famed planetary science center run by the California Institute of Technology for NASA. The laboratory faced budget cuts in the wake of the Cold War, although Dr. Stone was still able to work on high-profile missions that included Mars Pathfinder, which landed the Sojourner rover on Mars in 1997; the Galileo spacecraft, which orbited Jupiter for eight years; And Cassini, which orbited Saturn for 13 years.

A tribute from the laboratory noted that Dr. Stone was the rare scientist involved in the mission that traveled furthest from the Sun – Voyager – as well as the mission that came closest to the Sun: the Parker Solar Probe, which flew through the corona and upper atmosphere of the Sun in 2021.

“I keep asking myself why there is so much public interest in space,” Dr. Stone told The New York Times before taking the JPL job. “It is, in the end, just basic science in the end. The answer is that it provides us with a sense of the future. When we stop discovering new things, the concept of the future will change. Space reminds us that something needs to be done, and that life will continue to evolve. It gives us direction, An arrow at the right time.

The eldest of two sons, Edward Carroll Stone Jr. was born in Knoxville, Iowa, on January 23, 1936. He grew up in Burlington, Iowa, where his father ran a small construction company that his mother helped run. His parents supported his early fascination with science, including his efforts to take apart his transistor radio and put it back together again.

“I was always interested in knowing why something was this way and not that way,” Dr. Stone recalls. “I wanted to understand, measure and observe.”

After graduating from Burlington Junior College (now Southeastern Community College) in 1956, he enrolled at the University of Chicago, earning a master's degree in 1959 and a doctorate in physics in 1964. By then he had married Alice Wickliffe, a fellow student at the University of Chicago. chicago. she He died in December. Survivors include their daughters, Susan and Janet Stone, and two grandchildren.

With his Ph.D., Dr. Stone joined forces with one of his former colleagues at the University of Chicago, Ruchus “Robbie” Vogt, to help launch the space physics program at Caltech. He was appointed professor in 1976 and chaired the university's Department of Physics, Mathematics, and Astronomy in the mid-1980s, around the same time he began work on Keck, a complex of twin 10-meter telescopes near the summit of Mauna Kea in 1976. Hawaii.

His work on the project led him to endorse the proposed Thirty Meter Telescope, a larger observatory that scientists hope to build nearby. Construction has been halted amid protests by Native Hawaiians and other critics who oppose development of the site.

Dr. Stone was described by his colleagues as shy and single-minded, with few interests outside of physics. “My job is to relax,” he liked to say. He continued to work on Voyager for decades, juggling teaching and research duties while earning honors that included National Medal of Science in 1991 And the Shaw Prize in Astronomy In 2019, before retiring from the mission in 2022.

By then, probes had traveled well beyond the orbits of Neptune and Pluto. Voyager 1, the farthest of the two, is now located more than 15 billion miles from Earth, and remains operational even as engineers have had to come up with workarounds for faulty computer chips and other communication problems. The spacecraft and its twin will eventually run out of power, though Dr. Stone proudly noted that the two probes “will keep moving forever,” drifting across the cosmos with their golden payload and silent instruments.

“As far as what happens to me, nature will have its way, and I understand that,” he told the Los Angeles Times in 2011. “And even if I'm not there, we'll keep exploring, keep discovering science. I'm optimistic about that.”