There was no dress rehearsal for this one. If the timing was off by even a little, the spacecraft’s fuel lines could freeze solid, ending the mission for good.
Voyager 2 has spent nearly half a century doing things nobody who built it in the 1970s could have reasonably planned for. It’s the only spacecraft humanity has ever flown past Uranus or Neptune up close, it’s been operating in interstellar space for roughly eight years, and it’s still reporting home using computers and instruments that predate the personal computer.
By 2026, though, the thing threatening to end all of that wasn’t a broken part or a lost signal. It was electricity, and there simply wasn’t enough of it left to go around.
Why Voyager 2 is slowly running out of power
Voyager 2 doesn’t use solar panels, since sunlight becomes essentially useless for power generation once a spacecraft gets far enough from the Sun. Instead, it runs on three radioisotope thermoelectric generators, or RTGs, which convert heat from the natural radioactive decay of plutonium-238 into usable electricity.
RTGs have no moving parts to wear out, and they’ve kept both Voyager probes running decades past their original planetary mission. But that same radioactive decay is also a one way clock: as the plutonium fuel decays, the generators’ output steadily drops, and NASA says each Voyager spacecraft now loses roughly four watts of available power every year, an amount comparable to a small night-light.
Four watts sounds trivial by any household standard. On a spacecraft with essentially no power margin left, it’s the difference between keeping an instrument running and shutting it off for good.
Voyager 2 originally carried instruments supporting ten separate investigations; its cameras finished their work decades ago, NASA turned off its plasma science instrument in September 2024, and its low energy charged particle instrument went dark in March 2025. Before this year’s fix, the cosmic ray subsystem was next in line to be switched off.
What the “Big Bang” actually did
Rather than accept another instrument shutdown, engineers at NASA’s Jet Propulsion Laboratory spent roughly a year designing an unusually aggressive fix, nicknamed the “Big Bang,” that NASA describes as simultaneously turning off certain powered devices and swapping them for lower-power alternatives while keeping the spacecraft warm enough to keep functioning.
According to CNN’s reporting, the actual swap, executed on July 9, 2026, involved turning off two dedicated heaters and an old digital tape recorder that was being kept on purely for its residual heat, while activating different heaters and other lower draw components in their place. The net effect freed up close to 10 watts, comfortably more than the four watts Voyager 2 loses in an average year.
The word “simultaneously” carries real weight here. Engineers couldn’t simply switch one component off, wait to see what happened, and then switch its replacement on.
Voyager 2 is operating so close to the cold edge of its thermal tolerance that a poorly timed gap between shutting something off and turning its replacement on risked letting propellant lines freeze solid.
If that happened, the spacecraft would lose the ability to fire its thrusters and keep its antenna pointed at Earth, which would effectively end the mission even if every instrument and the radio itself still had power.
Kareem Badaruddin, the mission’s project manager, described the stakes plainly: “We couldn’t afford to be wrong,” a rare admission of how little room for error the team actually had.
To manage that risk, the team ran dedicated power and thermal tests on the spacecraft in May and June 2026 before attempting the real thing, and the full sequence went ahead in July, completing by roughly the middle of the month with Voyager 2 stable and all three of its remaining science instruments still running.
Voyager 2 was chosen to go first, ahead of its twin Voyager 1, largely because it had slightly more available power to work with and sits somewhat closer to Earth. NASA has said the same maneuver is now being carried out on Voyager 1 as well, with completion expected in the following weeks.
Why three old instruments are worth this much trouble
What survived the reconfiguration is a narrow but genuinely irreplaceable set of tools: a magnetometer that tracks the strength and direction of the local magnetic field, a plasma wave subsystem that detects waves moving through ionized gas, and a cosmic ray subsystem that measures high energy particles arriving from the Sun, the Milky Way, and beyond.
None of these measurements can be recreated from a telescope near Earth, because Voyager 1 and Voyager 2 remain the only two spacecraft ever to operate beyond the heliosphere, sampling the actual interstellar medium directly from two different trajectories through space.
That’s also why the heliopause crossing matters as more than trivia. Voyager 2 crossed that boundary, where the outward push of the solar wind gives way entirely to interstellar plasma, on November 5, 2018, according to NASA’s own analysis of the instrument data at the time.
Crossing it didn’t mean Voyager 2 had left the solar system altogether in every sense; it’s still bound by the Sun’s gravity and nowhere near the far more distant Oort Cloud. But by the mission’s working definition, it had moved beyond the Sun’s protective bubble of plasma and magnetic influence, into genuinely new territory no other human-built object has sampled directly.
Running a spacecraft from 19 hours away
Every part of this operation had to be planned around a communication delay that makes ordinary troubleshooting almost impossible. As of 2025, NASA put Voyager 2’s one-way signal travel time at roughly 19 and a half hours, meaning a basic command sent to the spacecraft and its confirmation signal returning takes close to 39 hours round trip, before engineers have even had time to study the telemetry and decide what to do next.
There’s also no perfect backup to test against beforehand: no identical flight-spare Voyager exists that has spent the same 49 years being irradiated and frozen in deep space, so some of the temperature thresholds that matter most now were never expected to become mission-critical when the spacecraft launched, and can’t be measured directly even today.
Every command sent has to account for nearly five decades of component aging and the real possibility that something routine simply won’t behave routinely anymore.
A spacecraft doing a job it was never built for
Voyager 2 launched on August 20, 1977, and its original assignment was a tour of the outer planets: Jupiter in 1979, Saturn in 1981, then Uranus in 1986 and Neptune in 1989, the only spacecraft to have visited either of the latter two up close.
Everything since then, including the entire interstellar phase of the mission, is a bonus made possible by a fortunate planetary alignment, unusually durable hardware, and decades of exactly this kind of engineering improvisation.
The Big Bang fix doesn’t make the spacecraft young again, and it can’t protect it from every possible failure; an aging transmitter, thruster, or onboard computer could still end the mission before the power budget does.
What it accomplishes is narrower and more specific: it removed the next scheduled deadline, buying real scientific time rather than sacrificing another one of the spacecraft’s remaining senses to survive a little longer.
Time that can’t be recovered any other way
An extra year can sound modest tacked onto a 49-year mission, but there’s currently no other spacecraft anywhere near the heliopause, and NASA has no approved mission in development to replace what Voyager 1 and 2 are doing.
Every additional month of data extends a record that, for now, can’t be recreated by any other means. Voyager 2 will keep losing power regardless, more shutdown decisions are coming, and eventually both the instruments and the spacecraft itself will go silent for good.
The July maneuver doesn’t change that eventual outcome. It changes how much more interstellar space Voyager 2 gets to measure before it arrives, and for a mission now being managed four watts at a time, that turned out to be a real win.