Voyager 1 Transmits Again: NASA Solves Interstellar Glitch
For nearly five months, the farthest human-made object in history drifted in silence. While Voyager 1 was still flying through interstellar space, it had stopped speaking a language NASA engineers could understand. That silence ended recently when the Jet Propulsion Laboratory (JPL) successfully hacked the aging probe from 15 billion miles away, restoring usable data transmission and saving one of humanity’s most important scientific missions.
The Day the Data Died
The trouble began on November 14, 2023. Voyager 1, which has been traveling away from Earth since 1977, started sending back a repeating pattern of ones and zeros that carried no meaning. While the spacecraft could still receive commands from Earth, its “voice” was broken.
The issue was located in the Flight Data Subsystem (FDS). This is one of the three onboard computers. The FDS is responsible for packaging engineering data (health and status of the probe) and science data (readings from instruments) before sending it to the telemetry modulation unit to be beamed back to Earth.
Because of the immense distance, communication is agonizingly slow. A radio signal takes about 22.5 hours to travel from Earth to Voyager 1. A response takes another 22.5 hours to return. This meant every time engineers sent a test command, they had to wait nearly two days to see if it worked.
Investigating a Memory Failure
For months, the team at NASA’s Jet Propulsion Laboratory in Southern California analyzed the gibberish signal. In March 2024, they attempted a “poke” command. This command was designed to prompt the FDS to try different software sequences in hopes of bypassing the corrupted section.
The strategy worked. One of the readouts from the poke command contained a memory dump of the FDS computer. By comparing this new data to the code Voyager 1 was supposed to be running, engineers pinpointed the exact problem.
A single chip responsible for storing a portion of the FDS memory had failed. This chip contained vital software code that the computer needed to package data. Without that code, the FDS could not process information. The cause of the failure remains unconfirmed, but engineers suspect the chip was either hit by an energetic cosmic particle or simply wore out after 46 years of operation in the harsh environment of space.
The "Impossible" Fix
Fixing a hardware failure on a spacecraft that is 15 billion miles away is impossible physically. You cannot swap out the chip. The only option was a software workaround. The team needed to move the affected code from the broken chip to a different location in the FDS memory.
However, there was a major complication. No single remaining block of memory was large enough to hold the entire section of code. The code was too big for the available slots.
The engineers devised a complex solution:
- They sliced the code into smaller chunks.
- They distributed these chunks across different available spots in the FDS memory.
- They rewrote the code to update “pointers” (instructions that tell the computer where to find data) so the system could jump between these scattered locations seamlessly.
This was a risky update. If the code references were off by even a single line, the computer could crash entirely, potentially ending the mission.
Restoring Contact and Science
On April 18, 2024, the team sent the code to move just the engineering data portion to its new memory location. It took 22.5 hours for the signal to arrive. On April 20, the team at JPL received the return signal.
The fix worked. For the first time in five months, Voyager 1 sent back readable engineering data. The team could finally see the health and status of the probe. They confirmed it was operating normally despite the months of silence.
Following this success, the team spent the next few weeks relocating the rest of the software, specifically the portions responsible for returning science data. By mid-May 2024, Voyager 1 resumed sending data from two of its four science instruments. As of late May and June, all four remaining science instruments were back online and returning usable data.
These instruments are:
- The Plasma Wave Subsystem
- The Magnetometer
- The Cosmic Ray Subsystem
- The Low Energy Charged Particle Instrument
Why Voyager 1 Matters
The stakes for fixing Voyager 1 were incredibly high because of its unique position. In 2012, it became the first spacecraft to cross the heliopause and enter interstellar space. This is the region where the sun’s flow of material and magnetic field stops affecting the environment.
Voyager 1 is currently sampling the plasma density and cosmic rays of the galaxy itself, rather than our solar system. No other spacecraft can provide this data. Its twin, Voyager 2, is also in interstellar space but travels on a different trajectory and functions more slowly. Losing Voyager 1 would have meant losing our only direct sensor reading of the space between stars.
The Road Ahead
While this victory is significant, Voyager 1 is operating on borrowed time. The spacecraft is powered by a radioisotope thermoelectric generator (RTG), which converts heat from decaying plutonium into electricity. The generator produces about 4 watts less power every year.
To keep the probe running this long, mission controllers have already turned off heaters and non-essential systems. Sometime around 2025 or 2027, the power output will likely drop too low to keep all science instruments running. NASA will have to start turning off instruments one by one to keep the transmitter alive.
Eventually, likely around 2036, Voyager 1 will fall out of range of the Deep Space Network’s antennas. However, thanks to this recent software rescue, the probe has a few more years to teach us about the cosmos.
Frequently Asked Questions
How far away is Voyager 1 right now? Voyager 1 is over 15 billion miles (24 billion kilometers) away from Earth. It is the most distant human-made object in existence.
How long does it take to send a message to Voyager 1? Because of the distance, light (radio signals) takes about 22.5 hours to reach the spacecraft. A round-trip communication takes roughly 45 hours.
What caused the communication breakdown? A single memory chip in the Flight Data Subsystem (FDS) failed. This corrupted the software code required to package and transmit data back to Earth.
Will Voyager 1 ever return to Earth? No. Voyager 1 is on a trajectory to leave the solar system forever. It will wander the Milky Way galaxy indefinitely. In about 40,000 years, it will pass within 1.6 light-years of the star Gliese 445.
What happens when the batteries die? Once the plutonium generator can no longer provide enough power, the probe will shut down. It will continue to drift through space as a silent ambassador, carrying the famous “Golden Record” containing sounds and images of Earth.