Voyager 1’s Glitch: Can NASA Fix the FDS?

In late 2023, the most distant human-made object in history stopped making sense. Voyager 1, currently over 15 billion miles from Earth, began sending a repeating pattern of ones and zeros that carried no usable data. For months, engineers at NASA’s Jet Propulsion Laboratory (JPL) scrambled to diagnose a critical failure in the probe’s Flight Data System (FDS). This article details specifically what went wrong, the ingenious coding surgery required to fix it, and the current status of this legendary spacecraft.

The Crisis: When Voyager Went Silent

The trouble began in November 2023. While Voyager 1 continued to broadcast a steady radio signal back to the Deep Space Network on Earth, the information within that signal was corrupted. The spacecraft was effectively suffering from electronic aphasia. It could “speak,” but it could not form words.

The culprit was identified as the Flight Data System (FDS). This is one of three onboard computers. Its primary job is to collect data from the science instruments and engineering telemetry (health and status data) and package it for the Telemetry Modulation Unit (TMU) to transmit back to Earth.

Because the FDS was stuck in a loop, mission controllers lost visibility into the spacecraft’s health. They did not know if the propulsion systems were working, if the temperature was stable, or if the science instruments were still collecting data about interstellar space.

The Diagnosis

Diagnosing a computer problem is difficult enough when the machine is on your desk. It is exponentially harder when the machine is 46 years old, runs on outdated code, and is 15 billion miles away.

Communication with Voyager 1 requires immense patience. Radio signals travel at the speed of light, yet they still take roughly 22.5 hours to reach the probe. A response takes another 22.5 hours to return. This means every troubleshooting command has a 45-hour round-trip wait time.

In March 2024, the JPL team sent a “poke” command. This command was designed to prompt the FDS to try different software sequences in case a specific section of memory was corrupted. The strategy worked. One of the responses contained a readout of the FDS memory. By comparing this readout to the code that should have been there, engineers pinpointed the exact issue. A single chip responsible for storing a portion of the FDS memory had failed. This chip contained vital code used for packaging the spacecraft’s engineering data.

The Solution: A Long-Distance Code Transplant

Since engineers cannot fly to interstellar space to solder a new chip onto the circuit board, the only solution was software-based. The team had to isolate the corrupted code and move it to a different location in the FDS memory.

However, there was a significant catch. The code section on the failed chip was too large to fit into any single block of available free memory elsewhere in the system. Voyager 1 operates with roughly 69 kilobytes of memory (less than a modern car key fob). Every byte is precious, and there are no large empty spaces.

The “Sliced” Code Strategy

The JPL engineers devised a risky and complex plan. They decided to slice the affected code into smaller chunks. They would then stash these chunks in various small, unused sections of memory scattered throughout the FDS.

This required a massive rewrite of the code. The team had to update every reference and pointer to ensure the instructions knew where to find the next chunk of code. If a single reference pointed to the wrong memory address, the entire system could crash permanently.

Execution and Success

On April 18, 2024, NASA sent the new code to Voyager 1. After a tense two-day wait, the Deep Space Network picked up a signal on April 20. The fix worked.

1. Engineering Data Restored: The first stream of readable data confirmed the spacecraft was healthy. The temperature, power levels, and propulsion status were all within nominal ranges.
2. Science Data Recovery: Once the engineering data was stable, the team began the process of bringing the science instruments back online. By May 2024, two of the four operational instruments began returning data.
3. Full Operations: By mid-June 2024, NASA confirmed that all four remaining science instruments (including the magnetometer and plasma wave subsystem) were successfully returning readable data.

The Future of Voyager 1

Voyager 1 is operating on borrowed time. While the FDS glitch has been resolved, the spacecraft faces an unavoidable energy crisis. The probe is powered by a Radioisotope Thermoelectric Generator (RTG), which converts heat from decaying plutonium-238 into electricity.

The generator produces about 4 watts less power every year. To keep the spacecraft alive, mission controllers have been systematically turning off non-essential systems, including heaters that keep instruments warm. Surprisingly, many instruments have continued to function despite freezing temperatures far below their tested limits.

Current estimates suggest Voyager 1 has enough power to continue returning at least some science data until 2025. After that, engineers may have to turn off science instruments one by one to keep the transmitter alive. By the 2030s, the probe will likely go silent, continuing its drift through the Milky Way as a silent ambassador of Earth.

Frequently Asked Questions

What caused the memory chip to fail? NASA engineers believe the chip failed due to one of two reasons. It may have been hit by an energetic particle from space (cosmic ray), or it may have simply worn out after 46 years of operation in the harsh radiation environment of interstellar space.

How far away is Voyager 1 right now? As of mid-2024, Voyager 1 is over 15.1 billion miles (24.3 billion kilometers) from Earth. It is the only spacecraft to have crossed the heliopause and entered interstellar space.

Why is the computer memory so small? Voyager 1 was launched in 1977. At that time, computing technology was in its infancy compared to today. The computers onboard use magnetic tape recorders and have less processing power than a modern musical greeting card.

Can Voyager 1 be fixed again if another chip fails? It depends on the location of the failure. The engineers at JPL have proven they can perform miracles with code updates, but eventually, the hardware degradation or power loss will become too severe to overcome.