Summary
NASA’s Voyager 1 is due to reach a distance of one light-day from Earth on Nov. 18, 2026. A recent power-saving change is intended to keep its remaining science instruments operating longer.
NASA’s Jet Propulsion Laboratory said on Oct. 29, 2026, that Voyager 1 is due to reach 16.09 billion miles (25.89 billion kilometres) from Earth on Nov. 18—the distance light travels in one day. The milestone comes as engineers work to extend the spacecraft’s science operations and investigate a brief loss of contact that resolved on Oct. 20.
Power-saving changes to extend science operations
Voyager 1’s electricity comes from radioisotope thermoelectric generators, which convert heat from decaying plutonium into power. As the plutonium supply declines, each Voyager spacecraft loses about 4 watts of power per year. Engineers have responded by switching off nonessential equipment and conserving energy wherever possible.
In early September, the team completed a change it calls the “Big Bang”: three devices on Voyager 1 were turned off and replaced with three lower-power alternatives. The devices help keep the spacecraft warm. The change had to be made as a coordinated swap so engineers could reduce power use while maintaining the distribution of heat across the spacecraft. The team had completed the same change on Voyager 2 about six weeks earlier.
Power limits had already led to two science instruments being turned off in recent years. Voyager 1 launched in 1977 with 10 science instruments; some were switched off after the spacecraft’s encounters with planets. Instruments left operating have studied the outer heliosphere, the region shaped by particles and magnetic fields from the Sun. Voyager 1 is now travelling through interstellar space, beyond that region, where the Voyagers are the only spacecraft to have made direct measurements.
JPL says the power-saving work will allow Voyager 1’s remaining science instruments to operate longer than previously anticipated. Without the change, the mission would have needed to switch off another instrument as early as summer 2027.
A brief communications pause, then a long wait for replies
NASA’s Deep Space Network failed to detect Voyager 1’s radio signal during two scheduled communication attempts on Oct. 18 and 19, which were 24 hours apart. The probe’s signal returned on Oct. 20, and the team has maintained contact since. JPL reported that one group of thrusters had gone offline and its backups had switched on. That transition is programmed to happen automatically if onboard computers detect a problem with the active thrusters; the spacecraft then enters a stable configuration and pauses normal operations while engineers investigate.
At the one-light-day distance, radio signals will take about 24 hours to travel from Earth to Voyager 1, and another 24 hours for a reply to travel back. In practical terms, a message and its response will take roughly two days to complete the journey. Voyager 1 is travelling at 38,000 mph (61,155 km/h), according to JPL.
The crossing is a marker of distance and communication delay, not a change in the spacecraft’s surroundings: JPL says Voyager 1 will detect no environmental change when it passes the milestone, and nothing aboard the spacecraft will change.