We've celebrated NASA's Voyager probes quite a bit on this site and with good reason. Voyager 1 and Voyager 2 are some of the most impressive feats of engineering ever developed. Since their launch in 1977, they've embodied a spirit of exploration and the thrill of 'going where no man has ever gone before.' Few people expected that 40 years after their launch, the Voyager missions would be as revolutionary as they've been. So, to better grasp the scope of what these incredible machines have done, let's take a look at some of Voyager 1 and Voyager 2's greatest accomplishments.
They're the only probes to explore Uranus and Neptune
And that's just the beginning of the Voyager probes' findings. They found the first active volcanoes beyond earth -- Jupiter's moon Io. Voyager 2 is the only spacecraft to ever fly by all four outer planets -- Jupiter, Saturn, Uranus, and Neptune (sorry, Pluto). Most of the phenomenal images we have of those planets come from Voyager 2.
This image from Voyager 2 was one of the first clear pictures scientists had of Neptune's Great Dark Spot. [Image Source: NASA JPL]
Voyager 1 became the first (and only) craft to ever go into interstellar space. Voyager 2 also discovered a possible subsurface ocean on Europa, and it analyzed a near-Earth-like atmosphere on Titan.
The probes challenge their engineers to problem solve like no other program before
The Voyager mission's biggest successes come from the team of engineers and designers. In the 1970s, they prepared for problems that were only theoretical and not confirmed until decades later. These engineers braced for the radiation of Jupiter and made sure both Voyager 1 and Voyager 2 could handle the toughest planet in the solar system. The engineers put in redundant systems to conserve power and thermoelectric generators running off of plutonium-238 decay.
This archive photo from NASA shows the preparations on Voyager 2, circa March 23, 1977. [Image Source NASA JPL-Caltech]
However, engineers are now having to figure out how to run the spacecrafts with dwindling power supply.
"The technology is many generations old, and it takes someone with 1970s design experience to understand how the spacecraft operate and what updates can be made to permit them to continue operating today and into the future," said Suzanne Dodd, Voyager project manager based at NASA's Jet Propulsion Laboratory in Pasadena. The Jet Propulsion Laboratory (JPL) still runs and maintains the Voyager missions.
There's also the lessons in patience for those engineers working with Voyagers. The spacecrafts won't get to another star for 40,000 years. They're both over 11 billion miles from Earth, and have a long way to go. For any researcher wanting to get quick results, the Voyager missions would be emotionally draining. However, both the northbound Voyager 1 and the southbound Voyager 2 send observations of interstellar space back to NASA whenever they can.
The Voyagers paved the way for other revolutionary probes
Thomas Zubuchen serves as the associate administrator for NASA's Science Mission Directorate at NASA Headquarters. He noted that no missions will truly match up to the Voyagers, however, future probes will certainly try.
"I believe that few missions can ever match the achievements of the Voyager spacecraft during their four decades of exploration," he said. "They have educated us to the unknown wonders of the universe and truly inspired humanity to continue to explore our solar system and beyond."
They're still active
With both probes turning 40, it also makes the Voyager missions the longest-running missions in the history of any space program. Voyager 2 turned the big 4-0 on August 20. Voyager 1 will hit that milestone on September 5.
None of the original team that launched the Voyager probes believed it would last this long. Edward Stone served as a Voyager project scientist and was the VP and Director of NASA's Jet Propulsion Laboratory. He said, "None of us knew, when we launched 40 years ago, that anything would still be working, and continuing on this pioneering journey. The most exciting thing they find in the next five years is likely to be something that we didn't know was out there to be discovered."
They carry our history with them wherever they go
The probes carry with them the Golden Records -- a collection of human voices, sounds, messages, and images that tell our story as the human race. Former U.S. president Jimmy Carter said of the Golden Records, "This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings. We are attempting to survive our time so we may live into yours."