The little probe that could: Why JPL just switched off part of Voyager 1

Nearly half a century ago, a spacecraft roughly the size of a small car set off from the Florida coast atop a rocket to begin what was supposed to be a five-year journey. This week, NASA announced it had shut down one of that spacecraft's remaining science instruments — not because the mission has failed, but to keep it alive a little longer.

Voyager 1, the most distant human-made object ever built, is running out of power. And the engineers who tend to it, from the Jet Propulsion Laboratory (JPL) in Southern California, are doing everything they can to delay the inevitable.

A spacecraft built for five years that has lasted nearly 50

Voyager 1 is a robotic space probe, launched on September 5, 1977, from Cape Canaveral aboard a Titan-Centaur rocket. It weighs about 1,797 pounds — roughly the mass of a mid-size sedan — and carries a 12-foot-wide dish antenna that it keeps pointed toward Earth so it can send and receive signals. It was built at JPL, a federally funded research center managed by the California Institute of Technology. And it has been operating ever since, almost without interruption, for nearly 49 years.

Its mission's origins lie in an astronomical coincidence: In the late 1960s, engineers and scientists recognized that the outer planets — Jupiter, Saturn, Uranus, and Neptune — were drifting into a rare alignment that would not repeat for roughly 175 years. That configuration made it possible for a spacecraft to use each planet's gravity as a kind of slingshot, gaining speed and redirecting course without burning extra fuel, in a technique known as gravity assist.

NASA originally envisioned an ambitious exploration of all the outer planets known as the "Grand Tour," though budget constraints eventually scaled that back. The renamed Voyager program was ultimately funded for a simpler, intensive fly-by of just Jupiter and Saturn, with the two spacecraft involved designed to last five years. They have now lasted nearly 10 times that.

Voyager 1 swung past Jupiter in March 1979, revealing active volcanoes on the moon Io, which was the first time volcanic activity had been observed anywhere beyond Earth. It then reached Saturn in November 1980, offering up-close studies of the planet's rings and its giant moon Titan in unprecedented detail. That close Titan encounter tilted Voyager 1's trajectory upward, out of the plane of the solar system, ending its planetary tour but sending it on a path toward the stars.

In 1990, NASA extended the spacecraft's effort under the Voyager Interstellar Mission banner, with a new objective: reach and study the very edge of the Sun's influence, and the space beyond it. On August 25, 2012, Voyager 1 crossed the heliopause — the boundary where the Sun's charged-particle wind gives way to interstellar space — becoming the first human-made object to enter the space between the stars. Its twin, Voyager 2, followed in 2018.

Workers near the top of the 526 ft. Vehicle Assembly Building at the Kennedy Space Center spruce up the NASA logo standing on scaffolds in Cape Canaveral, Fla., Wednesday, May 20, 2020.

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More than 15 billion miles away, on borrowed power

As of this spring, Voyager 1 is more than 15 billion miles from Earth. At that distance, a radio signal traveling at the speed of light takes more than 23 hours to reach the probe. Every command engineers send, every piece of data they receive, crosses that vast gulf.

The spacecraft runs on a radioisotope thermoelectric generator — a device that converts heat from decaying plutonium into electricity. It carries no solar panels, no rechargeable batteries. Just the slow, steady release of nuclear warmth, which diminishes by about four watts each year. After nearly five decades, that decline has become critical.

During a routine maneuver in late February, Voyager 1's power levels fell unexpectedly, bringing the probe dangerously close to triggering an automatic fault-protection shutdown — a self-preservation response that would have forced engineers into a lengthy and risky recovery process. The team needed to act first.

Switching off a piece of history to preserve the whole

On April 17, mission engineers sent a sequence of commands to deactivate the Low-energy Charged Particles experiment, known as the LECP, which is one of Voyager 1's remaining science instruments. The LECP has measured ions, electrons and cosmic rays originating from both our solar system and the galaxy beyond it, helping scientists map the structure of interstellar space in a way no other instrument could. Its counterpart on Voyager 2 was turned off in March 2025.

Years ago, the Voyager science and engineering teams jointly agreed on the order in which instruments would be switched off, to conserve power while preserving the most scientifically valuable capabilities. The LECP was next on that list. "While shutting down a science instrument is not anybody's preference, it is the best option available," said Kareem Badaruddin, Voyager mission manager at JPL, in a blog entry published by NASA Friday.

Voyager 1 now carries two operational science instruments: one that listens for plasma waves, and one that measures magnetic fields. Engineers believe the latest shutdown could buy the mission roughly another year of breathing room.

The team is also developing a more sweeping power-conservation plan they informally call "the Big Bang" — a coordinated swap of several powered components all at once, trading older systems for lower-power alternatives. If testing on Voyager 2, planned for May and June 2026, goes well, the same procedure will be attempted on Voyager 1 no sooner than July. If it works, there is even a slim chance the LECP could once more continue to work.

The engineers say they hope to keep at least one instrument operating on each spacecraft into the 2030s. It would leave both still reporting from places no machine has ever gone before.
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