Why Voyager 1 Is Still Talking to Us

HOOK0:00 to 0:45

In November 2026, a spacecraft launched in 1977 reaches one full light-day from Earth. From then on, a message the team sends one morning won't reach it until the next morning, and the reply takes another full day. Nothing humans have built has ever been that far from home.

But it's only still talking because people keep rescuing it. Since late 2023, Voyager 1 has needed three rescues. Each was run blind across nearly a day of signal delay each way. Four things on board have to keep working. Engineers have brought back three. The fourth, nobody can fix.

1. THE COMPUTER THAT FORGOT0:45 to 3:00

In late 2023, Voyager 1 started sending home nonsense. The spacecraft was still taking commands and otherwise working normally. But the data it sent back, about itself and about interstellar space, was unreadable.

So where do you even start? The team traced it to one of three computers on board. Its job is to package the science and engineering data before it gets sent to Earth. Think of it as the part that packs the envelope. If the packing goes wrong, nothing inside is readable.

By April 2024 they'd found the cause. A single chip that held part of that computer's memory had stopped working, and some of the computer's own software was stored on it. That code was gone. And you can't swap a chip on a spacecraft more than 15 billion miles away.

So they decided to move the code. The catch was that no single free spot in the memory was big enough to hold it.

Instead, they cut the code into sections and stored each one somewhere different in the memory. Then they had to adjust those pieces so they'd still run together as one program, and update every other part of the software that pointed to the old location. And they'd only find out if it worked about two days after sending it.

They started with just the code that packages engineering data. It went up on April 18. The signal took about 22 and a half hours to reach Voyager 1, and just as long to come back.

Two days later, the team gathered in a conference room at NASA's JPL to find out. It had worked. For the first time in five months, they could read Voyager 1's health data. The plan was to move the rest of the affected code over the following weeks, including the parts that send back science.

So that's one system brought back. Six months later, a simple command nearly cost them the radio.

2. THE RADIO FROM 19813:00 to 4:30

That October, the team sent Voyager 1 a command to turn on one of its heaters. It should have had plenty of power for that. Instead, the command tripped the spacecraft's automatic safety system.

That system is basically Voyager's survival reflex. If the spacecraft draws more power than it has, it starts switching things off by itself. And by this point the probes had already turned off every nonessential system except the science instruments. So there wasn't much left for it to switch off.

What it shut down was the radio Voyager 1 normally uses to talk to Earth. It switched over to a second radio instead. That one uses less power, but its signal is a lot fainter, and Voyager 1 hadn't used it to talk to Earth since 1981. The team wasn't even sure the signal could be picked up from that distance. Engineers at NASA's network of tracking dishes found it.

Rather than turn the main radio back on before they knew what caused the trip, the team stayed on the second one and worked the problem. They switched back to the main radio in November, and science collection resumed later that month.

One heater command took the main radio offline. That's how thin the margins had gotten, and it's going to matter later.

Meanwhile, the thing that keeps Voyager pointed at Earth was slowly clogging up.

3. THE THRUSTERS THAT WERE "DEAD"4:30 to 7:15

Voyager's big dish antenna has to point at Earth, or nothing gets through in either direction. To hold that aim, the spacecraft uses thrusters, and some of them control roll. Seen from Earth, roll turns the antenna like a vinyl record, and it keeps Voyager locked onto a guide star it uses to orient itself.

Each Voyager has a primary set of roll thrusters and a backup set. On Voyager 1, the primaries stopped working in 2004, after two small heaters inside them lost power. The team at the time decided the heaters were probably unfixable and moved over to the backups. Kareem Badaruddin, the mission manager at JPL, was pretty frank about it later. Back then, he said, they probably didn't expect the Voyagers to keep going for another 20 years.

They did. And by 2025 the backup thrusters had a problem of their own. Residue was building up in their fuel tubes, and it could stop them working as early as that fall.

So the team went back to the 2004 failure. They started to suspect a different cause. Maybe a disturbance in the circuits that power those heaters had flipped a switch to the wrong position. If they could flip it back, the heaters might work again, and the dead thrusters might come back with them.

Testing that was risky, though. They'd have to turn the dormant thrusters on first, then try to restart the heaters. If the star tracker drifted too far from its guide star in the meantime, those thrusters would fire automatically. And if they fired while the heaters were still off, it could cause a small explosion.

There was a deadline too. In early May 2025, a dish in Canberra, Australia, was going offline for months of upgrades. It's the only dish with enough signal power to send commands to the Voyagers.

On March 20, the team watched the spacecraft carry out their commands. Except what they were watching had actually happened almost a day earlier. Within 20 minutes, they saw the heater temperatures rise sharply. It had worked.

Todd Barber, the mission's propulsion lead, put it simply: "These thrusters were considered dead." Twenty-one years after they quit, they're a working backup again.

That fix started with a second look at an old failure. If you want more of the engineering behind missions like this, subscribe. That's what this channel covers.

Now the fourth system. This is the one no clever fix can bring back.

4. THE ONE THING NOBODY CAN FIX7:15 to 10:00

Everything Voyager does runs on electricity from generators that turn the heat from decaying plutonium into power. As the plutonium runs down there's less heat, and both Voyagers lose about 4 watts a year.

Why does 4 watts matter? Because this far into the mission, it's the reason heaters and instruments keep getting switched off. Remember the heater that took out the main radio? That's the kind of thing that happens when the margin is this thin.

In February 2026, Voyager 1 did a routine roll maneuver, and its power dropped when it wasn't supposed to. Any further drop could have triggered a low-voltage safety response, which shuts down parts of the spacecraft on its own and then needs a long, risky recovery. The team decided to act first.

On April 17, they turned off an instrument that measures charged particles. It had been running almost without a break since 1977. That choice wasn't made on the spot. Years ago, the science and engineering teams agreed on the order things would go off. Voyager 1 launched with 10 science instruments. It's down to two, one that listens to plasma waves and one that measures magnetic fields.

They did leave one piece of the charged-particle instrument running, though. A small motor that spins the sensor in a circle, drawing half a watt. Keeping it on gives them the best chance of switching the instrument back on someday, if they find the power.

That's the idea behind what the team calls the Big Bang. You turn off a group of powered devices all at once and swap in lower-power alternatives, while keeping the spacecraft warm enough to keep working. They tried it on Voyager 2 first, since it's closer and has a little more power to spare. NASA said it should keep Voyager 2's remaining instruments running for at least an extra year. Voyager 1 was next in line.

Three times in under two years, people brought back a failing part of this spacecraft from more than 15 billion miles away: the computer that packages its data, the radio, and the thrusters that keep it pointed home. Power is the one they can't bring back. They can only spend it more carefully. If nothing else breaks first, the end comes when that budget runs out.

From November 2026 on, every signal from Voyager 1 needs a full day to reach us. It comes from a machine its team is switching off, piece by piece, so it can keep talking.