Voyager 1 doesn’t die because nothing fails, with nearly 50 years of interstellar travel and every original system still working. The job ends because a plutonium battery that loses 4 watts per year eventually runs out of watts

Voyager 1 remains operational, and the expected decline in its supply of nuclear power is the mission’s central limiting resource. This is very true.

The rest of the title needs qualification. Voyager 1 has been flying for nearly 49 years, but it entered interstellar space in 2012. Many of the original instruments and components have failed or been decommissioned. Its power source is not a rechargeable battery, but three radioisotope-powered thermoelectric generators.

The achievement is no smaller when those differences are restored. The spacecraft that will still be alive in 2026 is a miniature, frequently repaired version of the machine that launched in 1977, and maintaining its usefulness has become its own engineering system.

Two scientific instruments remain active

NASA Current tool status page Lists two scientific instruments active on Voyager 1: the magnetometer and the plasma wave subsystem.

A magnetometer measures magnetic fields. The plasma wave instrument detects oscillations in the thin charged material surrounding the spacecraft. Both return measurements from beyond the edge of the heliosphere, a boundary that Voyager 1 crossed on August 25, 2012.

Communications, command, data processing, thermal control and attitude control must also continue to function. The high-gain antenna must remain pointed at Earth while the radio link carries data over more than 25 billion kilometers.

This is an effective mission, but it is no longer the full planetary observatory that was sent across Jupiter and Saturn.

Not all the original system still works

Some retired systems are healthy but no longer powered. Others deteriorated or failed.

Cameras are turned off after planetary encounters. The plasma instrument was discontinued in 2007 due to deteriorating performance. The photopolarimeter had failed much earlier. The cosmic ray subsystem and low-energy charged particle instrument were shut down in 2025 and 2026 to conserve energy.

In November 2023, Voyager 1 stopped transmitting readable engineering and scientific data. Engineers traced the problem back to Failed memory chip in the flight data subsystem. They partitioned the affected software among other memory locations and restored useful telemetry in 2024.

Thrust devices have also gotten older. The propulsion pipes became clogged with debris, forcing the team to switch between different branches. In 2025, even engineers The rotary impellers, considered unusable since 2004, were revived After returning electricity to their heaters.

Calling all of this a failure would result in missing out on the amount of recovery work. To say nothing failed would be to miss evidence.

A drop of four watts is real

Voyager 1 carries three RTGs. It converts the heat generated by the radioactive decay of plutonium-238 into electricity through thermoelectric couples, without the need for a turbine or a moving generator.

NASA says available production is almost down Four watts every year. Plutonium produces less heat slowly, and the thermoelectric material becomes less efficient as it ages.

The three generators provided approximately 470 watts at launch. This margin allowed Voyager to operate ten scientific instruments, heaters, computers, radios, and spacecraft systems during its encounters with Jupiter and Saturn.

The Department of Energy is now working through the rollout. Heaters, instruments and other loads are turned off so that the remaining systems can remain above the voltage required for reliable operation. Four watts seems trivial until four watts is almost the annual budget for another year’s purchase.

The familiar phrase “plutonium battery” is an understandable abbreviation. Technically, an RTG is a generator that continuously converts decomposed heat, not a battery that stores a limited electrical charge.

A shutdown can be a success rather than a failure

On April 17, 2026 Engineers The low-energy charged particle experiment aboard Voyager 1 has been discontinued. It has worked almost continuously since its launch.

The tool was not sacrificed because it suddenly broke. It is turned off to protect power to the magnetometer, the plasma wave instrument, and the engineering systems that allow them to return data.

This decision makes the meaning of failure less clear. Losing an instrument ends one line of science, but doing so intentionally may extend the rest of the mission. NASA said the remaining two instruments are still working well and returning data from an area no other operational spacecraft has reached.

This is what Voyager’s planned ending looks like in practice. It is not a single moment when an entire spacecraft battery suddenly depletes. Capacity is traded for time, one load at a time.

Power is the planned limit, not the only possible end

Low RTG production is the limitation that engineers can predict. It does not guarantee that the energy is the direct cause of the final signal. A memory failure, payment device failure, radio problem, or fault protection event may cause communications to end sooner.

The spacecraft also doesn’t have a single clean expiration date. Scientific operations can end before engineering telemetry. The transmitter could go silent while Voyager 1 continues to fly through interstellar space for thousands of years.

Our previous account for The small plutonium supply that powers Voyager Explains why generators have lasted so long. The current story is about what longevity looks like toward the end: less energy, fewer tools, and increasingly careful choices.

Voyager 1 is not a machine untouched in 1977, nor has it spent nearly 50 years in interstellar space. It’s an ancient spacecraft that survives through iteration, software fixes, and planned sacrifices. A 4-watt drop is real, but so is everything the engineers have actually worked on.