As the visionary and scientific leader of the Voyager program, Edward Stone led the historic exploration of the outer planets—Jupiter, Saturn, Uranus, and Neptune. The two Voyager spacecraft conducted the first detailed examinations of Jupiter and Saturn, but also the only visits to date of Uranus and Neptune. The spacecraft are now the first explorers of interstellar space.
More than 14 billion miles from Earth, traveling towards the stars at about 11 miles per second, flies an ambassador of humanity, a delicate and spindly craft about the size of a subcompact car. Heading in a different direction at a slightly slower speed is its identical counterpart. These are the Voyager spacecraft, standard bearers of one of history’s greatest adventures of exploration and discovery, one that is still underway after 50 years. Both carry a cosmic message, a disc containing music, words, and images from Earth to any intelligent lifeforms that may recover them. From the beginning of their saga in 1972, Edward Stone has led the Voyager mission.
To shepherd the project, Stone led 11 teams of scientists, each responsible for a separate instrument. While handling the administrative and scientific demands of the first-ever detailed explorations of Jupiter, Saturn, Uranus, and Neptune, he also conducted his own research for the Voyager cosmic ray instruments. Their sensitivity was high enough to identify carbon and argon nuclei entering the solar system from the interstellar medium.
Raised in Burlington, Iowa, Stone grew up tinkering with radios and electronic gadgets, an interest that would serve him well later as a physics student at the University of Chicago.
When Sputnik shook the world in 1957, he was a graduate student just as the new field of space physics was blossoming. After earning his doctorate in 1964, he became a research fellow at Caltech and designed and built experiments to fly into space as part of America’s first generation of satellites. He became a full professor in 1976.
Voyager was often overshadowed by the accomplishments of crewed spaceflight, but uncrewed planetary exploration was entering its first golden age, dispatching probes to Mars and Venus. The more distant worlds of the solar system soon came into reach. In the early1970s, Pioneer 10 and 11 ventured beyond Mars to Jupiter and Saturn. It would be up to the Voyager missions to fulfill the discoveries at which Pioneer had only hinted.
NASA named Stone the Voyager project scientist in 1972. He found himself responsible for a complex scientific and exploratory endeavor. The Voyager probes launched in summer 1977, each reaching Jupiter in 1979. As the findings poured in, Stone became the public face of the project, patiently explaining the science and the workings of the spacecraft to the world at press conferences and media interviews. The spotlight returned in following years as the spacecraft flew by Saturn, Uranus, and Neptune.
When Voyager at last swung by Neptune, most assumed the historic mission had finally come to an end. Stone had other ideas. As NASA, congressional and public attention drifted to new missions and programs, Stone, now director of the Jet Propulsion Laboratory, became the driving advocate for keeping Voyager alive. Stone knew the spacecraft had more to give and more to discover, because they were heading where nothing had gone before: the true beginnings of interstellar space.
Stone’s tireless efforts succeeded in winning a new assignment (and funding) for Voyager, the Voyager Interstellar Mission (VIM). Still very much under way, VIM is providing observations of the heliosheath, where the sun’s influence ends and interstellar space begins. Both Voyager spacecraft remain in contact with their distant home and are expected to operate until sometime later this decade, by which time their remaining power will be too low and their distance from Earth too great to sustain communications.
In the future, spacecraft will venture even further than the Voyagers. They will owe an incalculable debt to the spindly and fragile Voyagers 1 and 2 for blazing the way.