A spacecraft built in the 1970s does not get spare parts. When Voyager 1 runs short of electricity, its engineers can only rearrange what it already carries, and in September they did exactly that. The Voyager 1 power swap, which NASA’s Jet Propulsion Laboratory (JPL) described on 29 October 2026, has bought the probe more working time just weeks before it becomes the first human-made object to sit one light-day from Earth.
The team switched off three onboard devices and turned on three lower-power substitutes in a single coordinated move, nicknamed the “Big Bang”. All six help keep the spacecraft warm, so the change had to happen at once: power use had to fall without leaving any part of the probe too cold to work. Engineers had already carried out the same manoeuvre on the twin spacecraft, finishing it on Voyager 2 about six weeks earlier.
Both probes run on radioisotope thermoelectric generators, which turn heat from decaying plutonium into electricity. Their output drops by about 4 watts a year, and nothing can top it up. In April the team had already shut down Voyager 1’s Low-energy Charged Particles experiment, which measured ions, electrons and cosmic rays. Without the September swap, another instrument would have had to go as early as summer 2027.
Old hardware still finds new ways to worry its operators. On 18 and 19 October, NASA’s Deep Space Network listened for Voyager 1 twice, 24 hours apart, and heard nothing. The signal came back on 20 October. One group of thrusters had gone offline, and the spacecraft’s fault protection had switched to backups and paused normal operations, exactly as programmed. “This is the first time we’ve seen the spacecraft do something like this,” said mission manager Kareem Badaruddin. The root cause is still under investigation.
Distance makes every fault slow to diagnose. Voyager 1 has been in interstellar space since August 2012 and travels at about 61,000 km/h (38,000 mph). On 18 November it will be 25.89 billion km from Earth, the distance light covers in a day and, as NASA’s Night Sky Network points out, the farthest humanity has ever explored. A command sent from Earth will then take 24 hours to arrive, and the reply another 24.
The milestone changes nothing around the spacecraft itself. What matters more is that a few watts saved this autumn should still be paying for science in 2027. As project manager Suzanne Dodd has put it, saying hello to Voyager now means sending a message, going home, and checking back in two days.
