Voyager 1 Closes on One Light-Day From Earth

Voyager 1 is about to cross a distance no spacecraft has reached before. On November 18, 2026, NASA's most distant probe will sit roughly 25.9 billion kilometers from Earth — one light-day out, the distance light itself covers in 24 hours. NASA announced public events marking the approach in a November 10 advisory, updated on November 13, as the spacecraft closes on a point no human-made object has reached.

The crossing is set for 5:16 a.m. Eastern Standard Time on November 18, when the probe will be about 25.902 billion kilometers away. From that distance, a radio command traveling at light speed takes about 24 hours to arrive, and a reply takes another 24 hours to come back. That round trip is what makes troubleshooting the probe so demanding for its engineers.

NASA is asking the public to take part the night before. On November 17, after sunset in their local areas, the agency's "Shine Bright for Voyager's Light-Day" activity suggests flashing the letters VGR — the spacecraft's call sign — in Morse code with a light. On November 19, a discussion at the Jet Propulsion Laboratory will bring mission officials together to explain the twin spacecraft's scientific work and the challenge of keeping them running.

Voyager 1 launched in 1977, nearly half a century ago, and it has flown far beyond the planets it was built to study. It crossed into interstellar space in 2012, and Voyager 2 followed in 2018. Both probes still gather data beyond the Sun's heliosphere, the protective region shaped by solar particles and magnetic fields.

Keeping them alive takes active management. In an October update, NASA said engineers had put power-saving changes in place aboard Voyager 1 and had investigated a brief communications interruption that ended when the signal returned. The spacecraft runs on radioisotope power sources whose electrical output fades year by year, so every watt saved buys more observing time.

Nothing physical happens aboard Voyager 1 at the marker, and NASA doesn't claim otherwise. The distance between Earth and a moving probe changes constantly, and the crossing won't trigger any event on the spacecraft. What it measures is simpler: how far a working machine, launched when Jimmy Carter was president, has carried a signal — and how long that signal now takes to get home.