Nshan Kazaryan, the NASA engineer responsible for communicating with the Voyager 1 and Voyager 2 spacecraft, is actually younger than the probes he commands.
At 25 years old, Mr. Kazaryan belongs to a new generation of engineers at NASA’s Jet Propulsion Laboratory in California who are dedicated to keeping these aging but resilient spacecraft operational.
“Whenever I discuss Voyager, I tend to think of it like my parents,” he remarked. “As humans age, they develop various issues. A spacecraft is similar; the older it gets, the more problems arise.” (Notably, Mr. Kazaryan’s parents were not even born when the Voyagers were launched in 1977.)
Managing these aging spacecraft demands ingenuity, persistence, and a great deal of patience.
Each time Mr. Kazaryan transmits a command to one of the Voyagers, he must wait a couple of days to receive a response.
This delay represents the time required for a radio signal to complete the round trip. Voyager 1 is currently nearly 16 billion miles away, while Voyager 2 is slightly closer at roughly 13.3 billion miles—still more than four times the distance to Pluto.
It has been decades since the Voyagers’ peak, during which they flew past the giant planets and transmitted breathtaking photographs, including the reddish clouds circling Jupiter’s Great Red Spot and the delicate, shimmering rings of Saturn.
Today, hurtling away at over 30,000 miles per hour, the twin spacecraft have traveled farther than any other human-made object. Voyager 1 entered interstellar space in 2012, followed by Voyager 2 six years later.
Space scientists are eager for them to keep gathering unique data about the space between stars for as long as possible. It will be some time before another spacecraft ventures that far out.
However, this endeavor is growing increasingly difficult and will become impossible within a few years as the energy from the spacecraft’s plutonium batteries dwindles. To keep the probes functioning, engineers must take risks that other missions would not attempt.
“We operate like pirates,” said Kareem Badaruddin, the Voyager mission manager. “Nobody enjoys operating this close to the edge, but we have grown comfortable with it because it is our only option.”
In a notable success last month, the team executed what they call the “Big Bang” on Voyager 2—a strategic reconfiguration of the electrical systems that saved approximately 10 watts of power. This modest increase, sufficient to power a lightbulb or two, could extend the mission by about two years, pushing it well into 2031.
In the coming weeks, engineers will complete the rejuvenation process on Voyager 1, aiming to keep it operational until 2030.
A few additional years may not seem significant, but each day presents the potential for new discoveries. Compared to the particles emitted by the sun within our solar system, interstellar space contains “a different mixture of gas and different behavior,” explained Jamie Rankin, a space scientist at Princeton University and the mission’s deputy project scientist.
The engineers are aware they can only delay the inevitable demise of the Voyagers, yet they remain optimistic and resourceful.
“Who knows?” Mr. Badaruddin added. “Perhaps we will devise another solution.”
“However,” he continued, “this is, I believe, the best we can achieve.”
The Ailments of Old Age
Three chronic conditions are gradually deteriorating the Voyagers.
First, the fuel lines are becoming obstructed with residue dissolved from a silicone bladder that propels hydrazine—a liquid propellant—from the tank to the spacecraft thrusters.
This can be likened to cholesterol-clogged arteries in a spacecraft.
If too many thrusters on a Voyager fail, it would be unable to maintain its antenna’s alignment with Earth. Severed communications would result in the spacecraft being lost.
To mitigate the silicone buildup, the thrusters have been fired less frequently in recent years. The antenna is now permitted to drift further out of alignment before being gently redirected back toward Earth, and the lines through which the propellant flows are periodically alternated.
A second challenge is maintaining sufficient warmth in the fuel lines. Frozen hydrazine would also obstruct the propellant lines and damage the thrusters. Heaters installed on the spacecraft are designed to prevent this, but they consume electrical power.
This leads to the Voyagers’ third chronic condition: a dangerously low power supply. The plutonium batteries—officially known as radioisotope thermoelectric generators, or R.T.G.s—generate the Voyagers’ power by converting heat from the radioactive decay of plutonium into electricity.
The R.T.G.s initially generated about 470 watts for each Voyager. As the plutonium decayed and power diminished over the decades, scientific instruments were progressively shut down on the probes. Voyager 2, now operating on 216 watts, has only three of its 10 instruments still collecting data. Voyager 1, subsisting on slightly less power, has just two.
The mission team explored methods to conserve power. For instance, the digital tape recorder on Voyager 1 broke decades ago, but engineers kept it operational because it coincidentally warmed nearby propellant lines.
The designers of the Voyagers had included a heater to keep the recorder warm in the event it needed to be turned off. The engineers wondered why they couldn’t turn off the broken tape recorder and activate the heater, which consumes fewer watts.
This approach carried certain risks. The tape recorder had never been turned off, and the heater had never been turned on. More importantly, the heater generated less heat than the tape recorder. Analysis revealed that a thruster might become too cold for the hydrazine to flow. “It would not actually help us,” Mr. Badaruddin noted.
Conceiving the Big Bang
Out of necessity, the Voyager team had to consider a far more ambitious approach.
Engineer David Woerner proposed that while incremental changes would fail, implementing a series of changes simultaneously could maintain a balance between heat and power requirements while reducing the spacecraft’s overall power consumption.
This initiative became known as the Big Bang, and after nine months of analysis, Voyager engineers were convinced it could succeed. They concluded that the benefits outweighed the potential risks.
“Voyager is essentially the path of least regret,” stated Bruce Waggoner, the mission assurance manager. “There is no definitively right answer.”
They initiated the process with Voyager 2, as it was healthier in terms of power. The operation was executed in three stages to minimize the risk of losing the spacecraft.
“There is always a concern that it might not proceed correctly,” said Suzanne Dodd, who has served as the project manager for Voyager since 2010.
Initially, in May, the spacecraft was instructed to switch to the new configuration for 40 minutes. This was to verify that systems like the heater near the tape recorder, which had never been activated before, functioned properly.
A month later, Voyager 2 maintained the new configuration for six hours to confirm that temperature predictions were accurate. Finally, last month, the change was made permanent.
The 50th anniversary of their launches is just over a year away. “I am fairly confident that both will make it,” Ms. Dodd stated.
However, there are no guarantees. It would not be surprising if a critical system unexpectedly failed on one of the increasingly fragile Voyagers.
This occurred four years ago when Voyager 1 began transmitting gibberish to Earth instead of scientific and telemetry data. It effectively became mute, unable to inform engineers about the malfunction.
“We were essentially shooting in the dark,” said Sun Matsumoto, one of the engineers. “We simply had no idea.”
The issue was eventually traced to a failed memory chip that engineers were able to bypass, but Voyager 1 was out of commission for the better part of a year.
‘I Want to Be There’
While the Voyagers no longer capture the vibrant photographs they did while flying past the planets—the last images were taken by Voyager 1 in 1990, featuring a “family portrait” of the solar system—they continue to make discoveries in the uncharted territory of interstellar space.
In mid-2020, Voyager 1 detected a significant change in the magnetic field within that region of interstellar space, accompanied by a substantial shift in the density of the surrounding charged plasma. This alteration has persisted ever since. “We do not understand why,” Dr. Rankin stated. “It is quite a peculiar phenomenon.”
This is just one of the mysteries that the additional years of exploration could help solve.
Empowered by the energy saved from the Big Bang, engineers and scientists are considering reactivating some of the spacecraft’s dormant scientific instruments to gather additional insights, even if only briefly.
However, as with all their actions, this could jeopardize the spacecraft. One option is to wait until after the 50th anniversary.
“We have not made a decision yet,” said Dr. Linda J. Spilker, a planetary scientist at NASA’s Jet Propulsion Laboratory. “You could potentially lose the mission.”
Dr. Spilker was part of the mission when it launched, having joined as her first job out of college. She later transitioned to NASA’s Cassini mission, which orbited Saturn for 13 years, before returning to Voyager.
When asked about her plans following the 50th anniversary, she stated she was undecided. “I have about 10 wonderful grandchildren and other interests, such as travel,” she explained.
She has already reduced her schedule to part-time, which helps keep the ongoing operations for the Voyagers within a $5 million annual budget—a modest sum compared to many other NASA missions.
The following day, Dr. Spilker sent an email clarifying that the question had caught her off guard.
“After reflecting on it, I realized that I want to be there when each Voyager goes silent, so we can say our goodbyes as a team,” she wrote. “Following up on Voyager’s scientific discoveries has been a part of my life throughout my entire J.P.L. career, and I would not be satisfied if I left before their final moments.”