On April 17, NASA engineers sent a command to Voyager 1, now over 24 billion kilometers from Earth, to shut down its Low-Energy Charged Particles experiment, one of the last active instruments probing the interstellar medium.
The decision came not from choice but necessity. The probe’s radioisotope thermoelectric generator, fueled by decaying plutonium, has been losing roughly 4 watts of power per year since launch in 1977. After a routine roll maneuver on February 27 triggered an unexpected power dip, margins grew so thin that engineers had to choose between letting the spacecraft freeze or sacrificing another sensor.
With LECP offline, only two of Voyager 1’s original ten science instruments remain powered: the magnetometer and the plasma wave subsystem. These still measure magnetic fields and plasma waves in the space beyond the heliosphere, but even they are living on borrowed time.
NASA acknowledged the loss is significant. “The twin Voyagers are the only spacecraft that are far enough from Earth to provide this information,” the agency said in a statement, referring to the unique data LECP gathered on ion and electron flows, pressure fronts, and particle density in interstellar space.
Yet there is a sliver of hope. The instrument’s small scanning motor — which uses minimal power — was left running. Engineers hope that if a way to boost power emerges, they could restart LECP by reactivating its sensor while keeping the motor alive.
That hope hinges on a contingency plan nicknamed “the Big Bang.” Rather than incremental shutdowns, JPL proposes simultaneously switching off several current systems and replacing them with lower-power alternatives. The goal is not to generate more power, but to redistribute dwindling reserves efficiently enough to maintain critical components warm and prevent fuel lines from freezing.
The plan remains untested. NASA admits it isn’t sure if it will work. But without it, Voyager 1 may have only about a year of operational life left before even its last instruments fall silent.
Voyager 2, its twin, faces a similar fate. Its LECP instrument was shut down in March 2025. Both probes now operate in a careful dance of conservation, each command delayed by the 24-hour light-time delay to the spacecraft — meaning engineers won’t know if a command succeeded for another 48 hours.
Still, the fact that either spacecraft is still transmitting at all, nearly 50 years after launch, is a testament to engineering endurance. They have traveled farther than any human-made object, crossed into interstellar space, and continue to send back data from the dark between stars.
For more on this story, see Voyager 1: The Loneliest 23 Hours & Our Cosmic Isolation.
What the Big Bang plan actually involves
The Big Bang procedure is not a power boost but a strategic swap. Engineers would turn off multiple existing systems at once and replace them with lower-power alternatives designed to perform similar functions with less draw. The aim is to maintain enough heat to prevent the hydrazine fuel lines from freezing, which would end the mission instantly.
This approach differs from past shutdowns, which were reactive and piecemeal. By acting in concert, JPL hopes to stabilize the power budget long enough to potentially reactivate some instruments later — including, possibly, LECP — if the recent configuration proves stable.
The plan applies to both Voyagers. Success would extend the mission not just for Voyager 1, but for its twin as well, preserving the last active human senses in interstellar space.
Why this moment feels different
Previous instrument shutdowns were losses, but not existential. The cosmic ray system turned off in 2025, while significant, did not leave the probe so close to silence. Now, with only two instruments left, every watt is a tactical decision.
The timing likewise underscores the fragility of the achievement. Voyager 1 entered interstellar space in 2012. For over a decade, it has been humanity’s only direct sensor in that realm. Losing LECP narrows that window further — and there is no successor mission planned to replace it.
There is irony in the fact that the very longevity of the RTG, designed for decades of operation, now constrains the mission through its predictable decline. The plutonium-238 decay curve is known; the end is not a surprise, but its arrival still demands difficult choices.
What happens if the Big Bang fails
If the power redistribution does not work, the spacecraft will gradually cool. Without enough heat, the fuel lines could freeze, making trajectory adjustments impossible. Even if the instruments could still function, the probe would lose the ability to point its antenna toward Earth.
At that point, contact would be lost not due to the fact that the instruments died, but because the spacecraft could no longer aim its voice home. The data would stop flowing long before the last electron was drained from the RTG.
Even then, Voyager 1 would continue its silent journey, carrying the golden record into the unknown — a artifact of a species that once reached out, and kept listening, far longer than anyone expected.
Will Voyager 1 stop working completely after the Big Bang?
No. Even if the Big Bang fails, the spacecraft may still transmit for some time, but it will lose the ability to maneuver or point its antenna accurately, ending meaningful communication.
Can the LECP instrument be turned back on?
Possibly. Its scanning motor remains powered, preserving the chance to restart the sensor if extra power becomes available through the Big Bang or another solution.
Why not just wait for a power boost from the Sun?
Voyager 1 is too far — over 24 billion kilometers out — for solar panels to be effective. At that distance, sunlight is too faint to generate meaningful power; the RTG is the only viable source.
Is there a follow-up mission to replace Voyager 1?
No. No current or planned spacecraft is designed to reach interstellar space with the same instrument suite, making the Voyagers irreplaceable for now.