40 Years of Voyager: A Q&A With Dr. Ed Stone at NASA JPL

On Baronial xx, 1977, at Cape Canaveral, Dr. Edward C. Rock, in his role every bit chief scientist on the NASA Voyager mission, carried out final checks on Voyager 2 before the Titan-Centaur rocket blast it into space. Days later, on Sept. 5, Voyager 1 joined its twin spacecraft and headed out into the dark beyond.

Nigh 40 years later, later on its flyby of Jupiter and Saturn, Voyager i is now in interstellar space, 20.6 billion kilometers, or 137 Astronomical Units (AU), from Earth. Some 17 billion kilometers from World, Voyager 2 took a slightly different route, going by Uranus and Neptune, and is currently in the heliosheath, the outermost layer of the heliosphere where solar wind is slowed past the pressure of interstellar gas. Simply put, both spacecraft take traveled farther than whatever spacecraft has boldly gone before.

Artist's Concept of Voyager

Remarkably, Dr. Stone is even so in his role as chief scientist, despite having but historic his 81st birthday. He has been principal investigator on nine NASA spacecraft missions, co-investigator on five other NASA missions, director of NASA'south Jet Propulsion Laboratory (JPL) itself from 1991 to 2001, and received many honors, including the NASA Distinguished Service Medal and National Medal of Science. He's also a full-fourth dimension professor at the California Institute of Technology (Caltech), which manages JPL for NASA.

After a brief stop at NASA JPL Mission Control, where all signals from missions are monitored 24/vii past the Deep Space Network—a geek's thrill indeed—PCMag met upward with Dr. Stone, who talked us through a full-size replica of Voyager 1.

Earlier sitting downwards to talk, he pointed out the instruments onboard, which include a Magnetic field instrument, Low energy charged particle instrument, Cosmic ray instrument, Plasma instrument, and Plasma moving ridge instrument (Voyager 1 also has an Ultraviolet spectrometer subsystem). They directly back up the five scientific investigation teams participating in the Interstellar Mission: Magnetic field investigation, Low energy charged particle investigation, Plasma Investigation (Voyager 2 simply), Plasma wave investigation, and Catholic ray investigation.

Tin can you take us back and describe the temper at Cape Canaveral on August twenty, 1977?
It was a very intense menses. Thousands of things accept to happen at the right time. Yous've invested five years in the project, and at present, on that twenty-four hour period, it'south all sitting on top of a large Titan-Centaur rocket. Both of the twin spacecraft were congenital here, at NASA JPL, then trucked to Florida, roughly three months before launch. That's when I went downward there too, and where we put information technology all back together.

Voyager Team

That's also where the squad installed the radioisotope thermoelectric generators (RTGs) that convert the heat produced from the natural radioactive disuse of plutonium into electricity to ability the spacecraft, instruments, radio and on-board computers. The spacecraft fly too far from the dominicus to utilize solar panels. So, during that menstruation, the entire team moved to Florida, some stayed here at JPL in Operations, but about of us were in that location in the summer of 1977. It was an amazing time.

What inspired you to study astrophysics and infinite science in the first identify?
I went to the Academy of Chicago in 1956, in the graduate program for physics. I wanted to study nuclear physics as that was the frontier back then. 1 year later, Sputnik was launched and heralded a new era of exploration—and the first major discovery of the Space Age—the Van Allen radiation belts around the World. Information technology became apparent in that location was a lot to learn, if you could build the instruments and become them into infinite. As office of my work, I had the opportunity to launch scientific instruments looking at cosmic rays on a polar orbiting spacecraft.

Then, afterward your Ph.D., you came to join Caltech in early 1960s, became primary scientist on the Voyager and and then director. Did yous ever know you wanted to return to Voyager after finishing your time equally managing director?
I never left the Voyager mission, continued on correct through, every bit master scientist, while I was manager. It was several years after that Voyager 1 reached the first milestone in the Voyager Interstellar Mission: the termination daze of the supersonic air current. Voyager 1 crossed the termination shock in Dec 2004 at most 94 AU from the Sun while Voyager 2 crossed it in August 2007 at about 84 AU. And then in August 2022, Voyager 1 finally entered Interstellar space.

Voyager 1 Entering Interstellar Space (Artist Concept)

And they're nonetheless out there.
It'due south a long journey. Yes, they're notwithstanding sending back signals. When Voyager launched, the Space Historic period was but 20 years old and at that place was no empirical prove that spacecraft could final more a few years. Voyager 1 and 2 accept been up there for 40 years at present, and nosotros expect they'll deliver us valuable information until ~2030 when their nuclear power sources will no longer supply enough electrical energy to ability critical subsystems.

What are the 2 main questions about the universe that the mission has answered thus far?
Before Voyager, nosotros thought the only agile volcanoes were on Globe. Suddenly, on Jupiter's moon Io, nosotros found 10 times more volcanic activity, and that's but on a moon. We're no longer as "terracentric" in our view of the bodies in the solar system. Fourth dimension after time we were surprised past what nosotros discovered. On Triton, a moon of Neptune, where the nitrogen is frozen, we found geysers erupting—at 40 degrees higher up absolute zero! We know that on Earth, water is present in three dissimilar states—frozen, liquid, and gas—and we've now found moons where other substances, like nitrogen and methyl hydride, possess similar states. Suddenly, because of Voyager, nosotros realize how complex and interesting the planetary system is.

Is Voyager 2 yet on course to go interstellar soon?
We don't know exactly when, but the number I keep using is "a few years." Simply this is space exploration—it could be another surprise.

Talking of surprises, both Voyager spacecraft comport the 12-inch golden-plated copper disk which Carl Sagan and his committee put together equally a greeting for other life forms.
It was really astrophysicist Frank Drake, on Carl Sagan's committee, that suggested the phonograph record for the Voyager mission, instead of a plaque which was onboard earlier missions: Pioneer 10 and 11.

Voyager's Special Cargo: The Golden Record (NASA/JPL-Caltech)

Have you been disappointed that Voyager hasn't received a response from other interplanetary spacecraft?
(Pauses) You mean Search for Extraterrestrial Intelligence?

Yes
Information technology will be xl,000 years before the Voyagers pass by other stars, so information technology was never expected at that place would be a response to the golden record during their operational lifetimes.

Perhaps nosotros've been a bit dull as a prospect to anyone/matter out there?
(Laughs) Maybe! [Only] intelligent life is actually very rare. In that location are now searches for microbial life, and that'south to find the beginning of life. If a planet—or exoplanet—has the correct thermal and geophysical weather, with the development of scientific instruments it will exist possible to written report planets and exoplanets for testify of microbial life, which is the initial step leading to intelligent life.

Back on firmer scientific footing for the final question: The Voyager spacecraft won't always return to Earth, volition they?
No, in fact both spacecraft are escaping the solar organization at a speed of about 3.six AU per year. They'll continue communicating to Earth until the power runs out. The radioisotope thermoelectric generators (RTGs) accept a radiation one-half-life of 88 years, and the spacecraft could keep going until ~2030.

What will happen then?
Then Voyager one and 2 will both speed in their orbit around the center of the Milky Mode Galaxy every 225 million years—until the Milky way collides with another galaxy.