The commands went out on April 17. Engineers at NASA’s Jet Propulsion Laboratory in Southern California told Voyager 1 to switch off the Low-energy Charged Particles experiment, known as LECP. The spacecraft is running short of power, and the team judged this the best way to keep it going.
The instrument had run almost without a break since the 1977 launch, nearly 49 years. It measures low-energy charged particles, including ions, electrons and cosmic rays from the solar system and the galaxy, and it has provided data on the structure of the interstellar medium, such as pressure fronts and regions where particle density changes. Only the two Voyagers are far enough out to supply that information.
Running out of margin
Voyager 1 and Voyager 2 both draw electricity from a radioisotope thermoelectric generator, which turns the heat of decaying plutonium into power. Each probe loses about 4 watts a year. The margins are now thin enough that the team has been shutting off heaters and instruments, while taking care that the spacecraft do not get cold enough to freeze their fuel lines.
The trouble sharpened on Feb. 27. During a routine, planned roll maneuver, Voyager 1’s power fell unexpectedly. Another drop could have triggered the undervoltage fault protection system, which shuts down components on its own and leaves the flight team with a long, risky recovery.
“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. He said the two instruments still running, one that listens to plasma waves and one that measures magnetic fields, are “still working great.”
Decided years ago
The choice was not made in a hurry. Years ago the science and engineering teams agreed on the order in which parts of the spacecraft would go dark. Each Voyager carries 10 identical sets of instruments, and seven have now been shut off. For Voyager 1 the LECP was next. The same instrument on Voyager 2 was turned off in March 2025.
Voyager 1 is more than 15 billion miles (25 billion kilometers) from Earth, so the command sequence needed about 23 hours to arrive. The shutdown itself takes about three hours and 15 minutes. A small motor that spins the sensor to scan in every direction stays on, using 0.5 watts, to give the team a chance of reviving the instrument if more power turns up.
Engineers expect the move to buy Voyager 1 about a year. They plan to use it to finish a more ambitious fix for both probes, nicknamed “the Big Bang,” which swaps a group of powered devices for lower-power alternatives all at once. Voyager 2 gets it first, since it has a little more power and sits closer to Earth. Tests are planned for May and June 2026. If they go well, the team will try Voyager 1 no sooner than July, and the LECP could even come back on.
