Voyager 1 Sends Readable Data Again

For the first time in five months, NASA is once again receiving usable engineering updates from the most distant human-made object in existence. After a critical computer failure in November 2023 left Voyager 1 sending back nothing but unintelligible data, engineers at the Jet Propulsion Laboratory (JPL) have successfully executed a remote repair from over 15 billion miles away. This triumph marks a new lease on life for the 46-year-old probe as it continues its journey through interstellar space.

The Silence from the Edge of the Solar System

The trouble began on November 14, 2023. While Voyager 1 continued to broadcast a steady radio signal to Earth, the data contained within that signal became a repeating, nonsensical pattern of ones and zeros. The spacecraft was essentially alive, but it had lost its ability to speak coherently.

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 health of the spacecraft) and scientific data (from its instruments) before sending it to the telemetry modulation unit (TMU) for transmission to Earth.

For months, the team at JPL faced a daunting troubleshooting process. The primary challenge was the extreme distance. Voyager 1 is currently more than 15 billion miles (24 billion kilometers) from Earth. At that distance, radio signals traveling at the speed of light take 22.5 hours to reach the spacecraft. A response takes another 22.5 hours to return. This means every time the team sent a command to test a theory, they had to wait 45 hours—nearly two days—to see if it worked.

Identifying the "Single Chip" Failure

In March 2024, the team achieved a breakthrough. They sent a “poke” command to the spacecraft, instructing the FDS to try different sequences in its software package. One of the returning signals looked different from the rest of the garbled data.

An engineer with the Deep Space Network managed to decode this new signal. It turned out to be a readout of the FDS memory. By comparing this memory dump to the code Voyager 1 was supposed to be running, the team pinpointed the exact source of the problem.

A single chip responsible for storing a portion of the FDS memory had failed. This chip contained a critical segment of software code that the computer needed to function. Because that code was corrupted, the computer entered a loop, rendering the data transmission useless.

The Risky Remote Fix

Since engineers cannot physically replace a chip on a spacecraft located outside our solar system, they had to rewrite the software remotely. The solution involved moving the affected code to a different location in the FDS memory that was still functioning correctly.

However, there was a catch. No single section of memory was large enough to hold the entire block of code that needed to be moved. The team had to improvise by slicing the code into smaller chunks. They then stored these chunks in various available spots within the FDS memory.

This was not a simple copy-paste job. The engineers had to update the code to ensure that all the “pointers” (instructions that tell the computer where to look for data) referenced the new memory locations. If just one reference was off, the fix would fail, or worse, other systems could be corrupted.

A Successful Reboot

On April 18, 2024, the team sent the code to move the specific section responsible for packaging the spacecraft’s engineering data. After the agonizing 45-hour wait, the radio signal arrived at JPL in Southern California on April 20.

The fix worked. For the first time since November, the stream of data contained readable information about the health and status of the spacecraft. The engineering team confirmed that Voyager 1 is operating normally, maintaining its orientation, and communicating with Earth effectively.

What Happens Next for Voyager 1?

Now that the team has restored the flow of engineering data, the mission is not quite 100% complete. The next step involves relocating the remaining portions of the affected software. These sections are responsible for packaging the scientific data returned by the onboard instruments.

JPL expects to complete this work in the coming weeks. Once finished, Voyager 1 will resume sending vital information about plasma waves, magnetic fields, and particles in interstellar space.

This repair is a testament to the durability of 1970s technology and the ingenuity of modern engineers. Launched in 1977, Voyager 1 was originally built for a five-year mission to study Jupiter and Saturn. It is now approaching its 47th year of operation. While its power supply (radioisotope thermoelectric generators) is slowly degrading, this fix suggests the probe could continue collecting data until the late 2020s or even the 2030s.

Frequently Asked Questions

How far away is Voyager 1? Voyager 1 is over 15 billion miles (24 billion kilometers) away from Earth. It is the most distant human-made object in history and the first to cross the heliopause into interstellar space.

What caused the communication breakdown? The issue was caused by a corrupted memory chip in the Flight Data System (FDS). This computer formats data before sending it to Earth. The chip failure caused the data pattern to repeat in a loop of gibberish.

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.

Will Voyager 1 ever return to Earth? No. Voyager 1 is on a trajectory that will take it further out into the Milky Way galaxy. It will not return to our solar system.

What powers Voyager 1? The probe is powered by Radioisotope Thermoelectric Generators (RTGs). These devices convert the heat released by the decay of plutonium-238 into electricity. The power output decreases by about 4 watts per year.