Voyager 1 Back Online: How NASA Fixed the Interstellar Probe

For five tense months, the most distant human-made object in existence stopped making sense. Voyager 1, currently sailing through interstellar space over 15 billion miles from Earth, began sending back a repeating pattern of unintelligible binary code in November 2023. This left engineers at NASA’s Jet Propulsion Laboratory (JPL) blind to the spacecraft’s health and science data.

However, in a stunning display of remote engineering, the team successfully “hacked” the 46-year-old probe to bypass a fried memory chip. Here is the technical breakdown of how NASA resurrected Voyager 1 and restored data flow from the void between stars.

The Glitch: A Computer Stuck in a Loop

The trouble began on November 14, 2023. While Voyager 1 continued to receive commands from Earth and operate normally, its telecommunications unit began streaming back gibberish. The issue was traced to the Flight Data System (FDS). This is one of the probe’s three onboard computers. The FDS is responsible for packaging engineering data (about the ship’s health) and science data (from instruments measuring cosmic rays and magnetic fields) before sending it to the Telemetry Modulation Unit to be beamed back to Earth.

Instead of useful data, the FDS was stuck in a loop. It was repeating the same pattern of ones and zeros. The team at JPL spent months analyzing the readout. In March 2024, an engineer at the Deep Space Network managed to decode a specific section of the “gibberish” signal. It contained a readout of the FDS memory.

By comparing this readout to the code Voyager 1 was supposed to be running, the team identified the culprit: a single chip responsible for storing a portion of the FDS memory had failed. This corruption affected about 3% of the computer’s memory. This specific section contained the code crucial for packaging the spacecraft’s data.

The Diagnosis: Hardware Failure in Deep Space

NASA engineers suspect the chip failed due to one of two reasons:

1. Cosmic Rays: A high-energy particle from space may have struck the chip, permanently damaging it.
2. Age: The hardware is simply wearing out after 46 years of operation in the harsh environment of deep space.

Because the team cannot physically replace a chip on a spacecraft located 15 billion miles away, they had to find a software solution. The goal was to isolate the corrupted chip and tell the computer to ignore it completely.

The Fix: A High-Stakes Code Migration

The solution sounds simple in theory but was incredibly risky in practice. The engineers decided to move the affected code to a different location in the FDS memory. However, there was a major catch. No single section of the remaining memory was large enough to hold the entire block of code that needed to be moved.

The team had to improvise. They devised a plan to slice the code into sections and store those chunks in different places within the FDS memory. This was not just a copy-paste job.

Adjusting the Pointers

When code is moved to a new memory location, all references to that code must be updated. Imagine moving a book in a library; you also have to update the card catalog so people know where to find it.

The engineers had to update “pointers” throughout the system to ensure the computer knew exactly where each chunk of the split-up code was located. If they missed a single reference, the computer could crash or execute the wrong command, potentially ending the mission permanently.

The 45-Hour Wait

Adding to the difficulty was the immense distance. Radio signals travel at the speed of light, but Voyager 1 is so far away that it takes 22.5 hours for a command to reach the probe. It takes another 22.5 hours for the response to return to Earth.

Every time the team sent a command, they had to wait nearly two days to see if it worked.

Execution and Success

On April 18, 2024, the team sent the code to move the specific section responsible for packaging the engineering data. After a tense two-day wait, the radio signal returned on April 20. The fix worked. For the first time in five months, Voyager 1 sent back readable data regarding its health and status.

Following this initial success, the team began the process of relocating the rest of the affected code, specifically the portions that handle scientific data. By late May 2024, NASA announced that two of the four active science instruments were sending back usable data. As of June 2024, all four instruments—including the plasma wave subsystem and magnetometer—are fully operational and returning science data.

Why Voyager 1 is Irreplaceable

The effort to save Voyager 1 was critical because it provides data that no other spacecraft can. Launched in 1977, it is the only human-made object to cross the heliopause, the boundary where the sun’s influence fades and interstellar space begins.

Voyager 1 is currently sampling the interstellar medium. It measures the density of plasma and the intensity of cosmic rays outside our solar bubble. This data helps scientists understand the shape of the heliosphere and how it protects our solar system from high-energy galactic radiation. Losing Voyager 1 would have meant losing our only direct line of communication with the galaxy beyond our sun.

What Comes Next?

With the FDS fixed, the team is now working to resynchronize the timekeeping software on the spacecraft’s three onboard computers. They are also performing maintenance on the digital tape recorder, which records plasma wave data.

While the probe is back online, it is operating on a limited power budget. The radioisotope thermoelectric generators (RTGs) that power the ship lose about 4 watts of power per year. Engineers have already turned off all non-essential systems, including heaters and cameras, to conserve energy. The team estimates that Voyager 1 has enough power to continue sending science data until at least 2025, and potentially slightly longer if they continue to manage the power budget aggressively.

Frequently Asked Questions

How far away is Voyager 1? As of mid-2024, Voyager 1 is approximately 15.1 billion miles (24.3 billion kilometers) from Earth. It is the most distant human-made object in the universe.

How long does it take to send a message to Voyager 1? It currently takes about 22.5 hours for a radio signal to travel one way. This means a round-trip communication takes roughly 45 hours.

What computer language does Voyager 1 use? Voyager 1 uses a combination of assembly language and Fortran. The computers on board have less processing power than a modern key fob or a musical greeting card.

Will Voyager 1 ever return to Earth? No. It is on a trajectory that will take it out of the solar system forever. In about 40,000 years, it will pass within 1.6 light-years of the star Gliese 445, but it will no longer be operational at that time.

Why are the cameras turned off? The cameras were turned off in 1990 after taking the famous “Pale Blue Dot” image to save power and computer memory for the instruments that measure fields and particles, which are more valuable for interstellar science.