Voyager 1 Breaks Its Silence With NASA via a Radio Transmitter Not Used Since 1981

In 1977, NASA launched Voyager 1 and 2: a pair of spacecraft tasked with touring Jupiter, Saturn, Uranus and Neptune by taking advantage of a rare alignment of the outer planets that only happens once every 175 years. The two probes had both completed their encounters with these worlds by 1989, and since then, they’ve traveled to the outer limits of our solar system and beyond, sending critical scientific data back to Earth.

Recently, however, Voyager 1 briefly fell silent. It broke communication with NASA in mid-October, then restored contact in an unexpected way: a backup radio transmitter that had been inactive since 1981.

“The spacecraft recently turned off one of its two radio transmitters, and the team is now working to determine what caused the issue,” according to a NASA blog post.

NASA’s twin Voyager probes have been flying for 47 years, which means the agency’s scientists and engineers back on Earth have increasingly had to deal with age-related maintenance issues, per Space.com’s Samantha Mathewson. Last December, for instance, Voyager 1 started sending nonsensical transmissions. Engineers solved the problem five months later, restoring the craft to its full abilities by this summer.

On October 16, Voyager 1 experienced another hiccup. Scientists sent the probe a command to turn on one of its heaters, but for some reason, the command triggered its fault protection system, which is built to respond autonomously to issues onboard. To preserve energy, the fault protection system occasionally turns off nonessential processes, but Voyager 1 should have had enough energy to run the heater.

Because the probe is currently more than 15 billion miles away—making it the farthest spacecraft from Earth—it takes almost 23 hours for a command to reach the craft and another 23 hours for its response to reach scientists. That means the NASA team only noticed something was wrong two days later, when they didn’t detect a response from the probe.

Scientists communicate with both Voyager probes by using a radio transmitter that operates on X-band frequencies, within a range of 8 to 12 gigahertz, via NASA’s Deep Space Network, a web of giant radio antennas that make up the world’s biggest and most sensitive scientific telecommunications system. NASA quickly realized, however, that to preserve energy, Voyager 1 had begun sending signals at a lower rate on the transmitter, and teams found the new signal successfully.

Then, on October 19, Voyager 1 fell silent again. The team speculated that the probe might have completely turned off its X-band transmitter in favor of a backup S-band radio transmitter, which operates at a much lower frequency of two to four gigahertz—an instrument it hadn’t used in 43 years. Communicating on the S-band uses less power, but its signal is also fainter, so if that was the case, NASA scientists weren’t sure whether they’d be able to detect it from Earth. Coupled with the fact that Voyager 1 is much farther away now than it was when it last used the S-band in the ’80s, finding the signal could have been a difficult task.

Luckily, the Deep Space Network was indeed able to pick up the new, weaker signal, and scientists are now working to understand what caused Voyager 1 to switch off its X-band transmitter.

The agency’s engineers will proceed with caution, since they don’t want to risk the spacecraft’s welfare by trying to turn the X-band back on prematurely, as Bruce Waggoner, the Voyager mission assurance manager, tells CNN’s Ashley Strickland. But if they can get the transmitter back online, it might tell them what went wrong.

“The S-band signal is too weak to use long term,” Waggoner tells CNN. “So far, the team has not been able to use it to get telemetry (information about the health and status of the spacecraft), let alone science data. But it allows us to at least send commands and make sure the spacecraft is still pointed at Earth.”

Despite how long ago the twin probes launched, the Voyager spacecraft were built to last. “A profound insight gleaned from Voyager 1’s odyssey is the significance of redundancy in mission-critical hardware,” Eric Ralls writes for Earth.com. “The foresight to incorporate a backup radio transmitter, decades ago, underscores the necessity of planning for the unforeseen in space exploration.”

“We didn’t design them to last 30 years or 40 years, we designed them not to fail,” John Casani, Voyager project manager from 1975 to 1977, says in a NASA statement.

In 2012, Voyager 1 became the first spacecraft to cross out of the heliosphere—a sort of bubble surrounding the solar system filled with the solar magnetic field and solar wind—making it the first spacecraft to enter interstellar space. Voyager 2 reached the cosmic milestone six years later.

Voyager 1 will likely have enough power to run its scientific instruments until 2025, per Newsweek’s Tom Howarth, but NASA should be able to maintain communication with the spacecraft into the 2030s.

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.