Voyager Probes Defy Age, Spark Ingenious NASA Revival

Launched in 1977 with a five-year mission, the two Voyager probes continue their work nearly half a century later, thanks to a dedicated team of NASA engineers finding innovative solutions to keep them operational far beyond their expected lifespan.

Battling the Elements: Fuel vs. Power

Although the probes have enough hydrazine fuel to potentially last another 10 to 15 years, the decaying plutonium that powers their electrical systems is running out faster. Kareem Badaruddin, technical manager of the Voyager mission at NASA, sees this as a sign of success. “If we arrive at the point where there is no longer enough plutonium, it will be a victory,” he stated, “It will mean that we have resolved all the other problems of spaceship much older than the expected duration of their mission.”

Decoding Voyager 1’s Communication Blackout

Voyager 1 faced communication breakdowns between December 2023 and April 2024, which required a team of experts to solve. According to Badaruddin, “We have summoned a dozen NASA experts on the antennas, software, memory and electronic hardware… Finally, we understood by elimination that it was a problem of corruption of a memory unit of the central computer.” The breakthrough came with the observation of a repetitive message, “333b,” hidden within incomprehensible data.

Testing Limits in Deep Space

NASA engineers usually prioritize thorough testing before implementing new software. However, the Voyager missions present unique challenges. “At NASA, we are champions of doubt, we are still testing software changes to avoid unpleasant surprises in space. But with the Voyager we cannot test. We must trust our analyzes. It is difficult for most of us,” explains Badaruddin. Changes can sometimes be tested on Voyager 2, which is closer to Earth.

Managing Power Loss

The probes lose approximately 4.5 watts of power annually due to plutonium degradation. To compensate, non-essential instruments have been powered down. “Until now, we have been able to remove the supply to the not necessary instruments, such as the high -speed transmission antenna… and the cameras which, in any case, are useless because there is not enough light,” says Badaruddin. An overvoltage protection system has also been deactivated.

Extending Lifespan Through Innovation

In an effort to prolong the mission, an engine unused since 2004 was revived. Ten years ago, NASA discovered that silicone from the hydrazine tanks was dissolving into the fuel, leading to deposits that clogged the engines. As Badaruddin noted, “It contaminates the fuel and it leaves deposits that enlighten the engines… Some are more than 90 % blocked.”

Solving the Byte Inversion Mystery

The resurrected engine faced a heating issue, with the temperature incorrectly registering as zero. Suspecting a computer bug, the team identified a potential “byte inversion” in the heating software. At the time, we thought that probes had only a few years of useful life, so we had not investigated this heating problem, explained Badaruddin.

A precise maneuver was performed to close the current engine for 45 minutes to confirm the diagnosis. Now, Voyager 1 has a spare engine, contributing to the sixteen engines each probe uses for orientation.

Unexplained Phenomena at the Edge of the Solar System

Since 2020, an increasing magnetic field and plasma density around Voyager 1 has puzzled scientists. It is speculated that this zone is linked to an irregular heliopause, the boundary where solar and interstellar winds meet. This suggests that Voyager 1 may not reach the “pure interstellar wind” area for another five years, challenging previous assumptions about the heliopause’s precise location.

Legacy and Future Leadership

Ed Stone, the program’s first scientific manager, retired in 2022 at age 84 after dedicating 50 years to the probes. Scientific manager Linda Spilker, who also worked on the Cassini mission for 30 years, is considering her own retirement at 70. “Certainly until 2027, for 50 years. Then we will see,” she stated, acknowledging her capable successor, Jamie Rankin, and her desire to spend more time with her ten grandchildren.

Voyager’s Discoveries

Originally tasked with exploring Jupiter and Saturn, Voyager 2 extended its mission to Uranus in 1986 and Neptune in 1989, providing the only close-up observations of these distant planets. Both probes crossed the heliopause, with Voyager 1 doing so in 2012 and its twin in 2018. Among the many findings, the probes revealed volcanism on Jupiter’s moon Io, rings around Uranus and Neptune, lightning activity on Jupiter, subsurface oceans on Europa and Enceladus, and methane geysers on Triton.

Continuing Impact

Despite their age, the Voyager probes continue to transmit valuable data from the outer reaches of our solar system. According to NASA, as of June 2024, Voyager 1 is approximately 15.5 billion miles (25 billion kilometers) from Earth, while Voyager 2 is about 13 billion miles (21 billion kilometers) away (NASA). As technology advances, these probes persist in pushing the boundaries of space exploration.