After working for five months to restore communication with the furthest launched human-made object in existence, NASA announced this week that the Voyager 1 probe has finally called home.
For the engineers and scientists working on NASA’s longest-duration mission in space, it was a moment of joy and intense relief.
“We all went in that Saturday morning, sitting around the donut boxes, waiting for the data to come back from Voyager,” said Linda Spilker, project scientist for the Voyager 1 mission at NASA’s Jet Propulsion Laboratory in Pasadena. California. “We knew exactly when it was going to happen and it got really quiet and everyone just sat there looking at the screen.”
When the spacecraft finally answered the agency’s call, Spilker said the chamber exploded in celebration.
“There was cheering, people were raising their hands,” he said. “And there’s a sense of relief, too, which is okay, to get back to communicating after all that hard work and barely getting a signal from Voyager, it was a tremendous relief and a great feeling.”
The problem with Voyager 1 was first detected in November. At the time, NASA said it was still in contact with the spacecraft and could see it was receiving signals from Earth. However, the information transmitted to mission controllers—including scientific data and information regarding the health of the probe and its various systems—was garbled and unreadable.
This began a months-long effort to determine what went wrong and try to save the Voyager 1 mission.
Spilker said he and his colleagues remain hopeful and optimistic, but the team faces enormous challenges. First, engineers were trying to troubleshoot a spacecraft traveling more than 15 billion miles away in interstellar space; this was the pinnacle of long-distance calling.
“On Voyager 1, it takes 22 1/2 hours to get the signal and 22 1/2 hours to get the signal back, so we prepare the commands and send them, and as soon as two days later, Spilker would have the answer to whether it worked or not,” he said.
The team eventually determined that the problem was caused by one of the spacecraft’s three onboard computers. A hardware failure, perhaps as a result of aging or exposure to radiation, likely corrupted a small portion of the code in the computer’s memory, Spilker said. This glitch meant that Voyager 1 was unable to send consistent updates about its health and scientific observations.
NASA engineers determined that they could not repair the chip where the corrupted software was stored. Additionally, the faulty code was so large that Voyager 1’s computer could not store both it and the newly loaded instructions. Because Voyager 1’s technology dates back to the 1960s and 1970s, the computer’s memory pales in comparison to any modern smartphone. That’s roughly equivalent to the amount of memory in an electronic car key, Spilker said.
But the team found a workaround: They could split the code into smaller pieces and store them in different areas of the computer’s memory. They can then reprogram the section that needs fixing while making sure the entire system is still working harmoniously.
This was a success because the longevity of the Voyager mission meant that there was no working test bed or simulator on Earth to test new pieces of code before they were sent to the spacecraft.
“We had three different people go through the code patch we were going to ship, line by line, looking for anything they missed,” Spilker said. “And it was kind of just a visual check of the software that we were shipping.”
The hard work paid off.
NASA announced the happy development in a post on X on Monday: “Sounds a little more like #Voyager1.” The spacecraft’s own social media account replied, “Hello, it’s me.”
So far, the team has determined that Voyager 1 is healthy and operating normally. Spilker said the probe’s scientific instruments are turned on and appear to be working, but it will be some time before Voyager 1 can continue sending back scientific data.
Voyager 1 and its twin probe, Voyager 2, were each launched in 1977 on missions to study the outer solar system. Voyager 1 flew past Jupiter and Saturn as it hurtled through the cosmos, closely examining the planets’ moons and snapping images along the way.
Located 7.6 billion miles away, Voyager 2 has made close encounters with Jupiter, Saturn, Uranus and Neptune and continues to operate normally.
In 2012, Voyager 1 became the first human-made object to go beyond the solar system and enter interstellar space, or the space between stars. Voyager 2 did the same thing in 2018.
Spilker, who first started working on Voyager missions when he graduated from university in 1977, said the missions could last until the 2030s. But eventually the probes will run out of power or their components will become too worn out to continue working.
Spilker said it will be difficult to one day finally end the missions, but Voyager 1 and 2 will live on as “our silent ambassadors.”
Both probes carry time capsules with them; these are messages on gold-plated copper discs, collectively known as the Golden Record. The discs contain images and sounds that represent life on Earth and humanity’s culture, including musical pieces, animal sounds, laughter, and greetings recorded in different languages. The idea is that the probes carry messages until they are presumably found by space travelers in the distant future.
“Maybe in 40,000 years or so they will come relatively close to another star and could be found at that point,” Spilker said.
This article first appeared on NBCNews.com.