NASA's Voyager 1 Sends Readable Data Again

For five nerve-wracking months, the most distant human-made object in history spoke only in gibberish. NASA’s Voyager 1, currently sailing through interstellar space, stopped sending readable science and engineering data back in November 2023. However, thanks to a creative and high-stakes repair by engineers at the Jet Propulsion Laboratory (JPL), the spacecraft is once again communicating clearly with Earth.

The Silence from 15 Billion Miles Away

The trouble began on November 14, 2023. While Voyager 1 continued to phone home, the signal it sent contained no usable data. Instead of binary code representing discoveries about interstellar space or the health of the ship, the readout was a repeating pattern of ones and zeros. It was essentially a dial tone without a voice.

The mission team at NASA’s JPL in Southern California traced the issue to the flight data subsystem (FDS). This is one of the probe’s three onboard computers. The FDS is responsible for packaging data from the science instruments, as well as engineering data about the health of the spacecraft, before transmitting it to Earth.

Engineers discovered that a single chip responsible for storing a portion of the FDS memory had failed. Without that chip, the computer could not execute its software properly. This resulted in the unintelligible data stream.

A High-Stakes Remote Repair

Fixing a computer glitch is frustrating enough on Earth. Fixing one on a spacecraft built in the 1970s that is over 15 billion miles (24 billion kilometers) away presents a unique set of challenges.

The Time Delay

Radio signals travel at the speed of light. However, given the immense distance, it takes approximately 22.5 hours for a command to travel from Earth to Voyager 1. It takes another 22.5 hours to hear back. This means the engineering team had to wait nearly two days to see if any attempt they made was successful.

The Code Solution

Since the engineers could not physically replace the broken chip, they had to find a software workaround. The team decided to place the affected code elsewhere in the FDS memory. However, no single location was large enough to hold the entire section of code.

The solution required a complex digital surgery. The team devised a plan to slice the code into sections and store those chunks in different places within the FDS. This was not as simple as copy-and-pasting. The engineers also had to adjust those code sections to ensure they still functioned as a whole. They updated references to the code’s location so the other parts of the FDS memory would know where to look for the data.

On April 18, 2024, the team sent the command to move the code responsible for packaging the spacecraft’s engineering data. On April 20, after the 45-hour round-trip wait, the team received a clear signal. For the first time in five months, they could check the health and status of the spacecraft.

Resuming Scientific Discovery

Restoring the engineering data was only the first step. The ultimate goal was to get Voyager 1 back to doing what it does best: studying the cosmos.

On May 19, 2024, the mission team executed the second phase of the repair. They sent commands to beam back data from two of the four science instruments: the plasma wave subsystem and the magnetometer. These instruments are critical for detecting plasma waves and magnetic fields in the space between stars.

As of mid-2024, all four remaining operational instruments are returning usable data. This includes:

• The Cosmic Ray Subsystem: This measures high-energy particles.
• The Low-Energy Charged Particle Instrument: This studies the intensity of particles in the solar wind and interstellar medium.
• The Magnetometer: This provides data on the magnetic environment.
• The Plasma Wave Subsystem: This analyzes plasma density.

Why Voyager 1 Is Irreplaceable

The successful repair is a massive relief for the scientific community because Voyager 1 occupies a unique position in history and space. Launched in 1977, it entered interstellar space in August 2012. It is the only spacecraft currently sending data from outside the heliosphere (the protective bubble of particles and magnetic fields created by our Sun).

Voyager 2, its twin, is also in interstellar space but travels on a different trajectory and is functioning normally. Together, they provide the only direct sampling of the local interstellar environment.

Managing an Aging Spacecraft

The fact that Voyager 1 is working at all is a testament to its engineering. The probe was originally built for a five-year mission to study Jupiter and Saturn. It has now been operating for nearly 47 years.

Keeping it alive requires sacrifice. The spacecraft is powered by a radioisotope thermoelectric generator (RTG), which converts heat from decaying plutonium into electricity. This power source generates about 4 watts less per year.

To deal with the shrinking power supply, mission managers have had to turn off heaters and non-essential systems to keep the science instruments running. The recent memory failure highlights the vulnerability of the aging hardware, but the successful fix demonstrates that the team at JPL still has tricks up their sleeves to extend the mission.

Frequently Asked Questions

How long will Voyager 1 last? NASA expects Voyager 1 to continue collecting data until at least 2025. After that, the power levels may drop too low to operate the science instruments. However, the Deep Space Network may still be able to track its engineering signal until 2036.

Where is Voyager 1 going? Voyager 1 is not headed toward a specific star. It is drifting through the Milky Way galaxy. In about 40,000 years, it will pass within 1.6 light-years of the star Gliese 445, located in the constellation Camelopardalis.

What happens if another part breaks? The engineering team has redundant systems for many functions, but as the FDS issue showed, not everything has a backup. If a critical hardware component fails completely, the mission could end. However, the team has successfully managed “impossible” fixes before by rewriting software and bypassing damaged sectors.

Can Voyager 1 return to Earth? No. Voyager 1 is traveling at approximately 38,000 miles per hour (61,000 kph) away from the Sun. It has achieved escape velocity and will wander the galaxy forever, carrying the Golden Record as a message from humanity.