As director of Pasadena's Jet Propulsion Laboratory, Edward Stone has overseen some of NASA's greatest successes and worst failures of the past decade

Edward Stone has been at the forefront of the American space program almost since its inception in 1958. A physicist by training, he came to the California Institute of Technology (which administrates NASA's Jet Propulsion Laboratory) in 1961, and has been the chief scientist on nine NASA spacecraft missions.

In 1991, Stone became director of JPL and ever since has been spearheading the institution's sometimes-rocky transition toward less expensive and more frequent planetary missions. These have included the successful Mars Pathfinder mission in 1997, which put a rover on the surface of Mars, but also the unsuccessful Mars Climate Orbiter and Polar Lander in 1999. He recently announced that he will resign as director next year, after his 65th birthday.

Since in the 1960s, JPL has been developing spacecraft and overseeing missions to explore other worlds, principally other planets in the solar system. One of the most successful of these missions was the Voyager project, twin spacecraft that were launched in 1977 and are still communicating their findings as they travel through space. Stone was the chief scientist on the Voyager project.

Besides heading JPL, Stone also serves as vice president of Caltech and as chairman of the board of directors of the California Association of Research in Astronomy, which is operating the two W.M. Keck Observatory telescopes on Mauna Kea, Hawaii.

He has received numerous honors and awards, including honorary degrees from Harvard University, Washington University in St. Louis, and the University of Chicago.

Question: What have been the most important changes in the type of space missions overseen by JPL under your watch?

Answer: The major change has been the transition from what I call the secondary era of exploration to the third era. In the first era, the main engineering and science challenge was just getting to another planet. That was in the 1960s. It established the capability to get there and set the stage for the second era, where the challenge was to find out what was actually out there. Those were global surveys of everything in the solar system, at least all the major planets and many of the moons. Since we knew so little, that meant that we wanted very large, comprehensive observatories with many instruments.

Q: How is the third era different from the second?

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