Voyager 1 Reaches One Light-Day Distance From Earth in Milestone

NASA’s historic Voyager 1 spacecraft is on track to set another major record as its mission approaches the half-century mark. On Nov. 18 at 5:16 a.m. ET, the probe will reach a distance of one light-day from Earth, completing a journey of nearly five decades that places it farther from our planet than any human-made object in history.

One light-day represents the distance that light travels in a single day at the speed of light, which is approximately 186,282 miles per second. That translates to 25.9 billion kilometers or about 16.1 billion miles. At an average human walking speed of 3 mph, it would take a human 612,015 years to walk that distance. Fortunately, Voyager 1 has been traveling considerably faster, zipping through the cosmos at a steady 37,763 mph since a gravity-assisted Saturn flyby in 1980.

This milestone arrives 14 years after the spacecraft crossed the heliopause and entered interstellar space, and 28 years after passing Pioneer 10 to become the human-made object that has traveled the farthest into space.

Power Conservation and Mission Timeline

Reaching this historic milestone has not been without operational drama. NASA’s Jet Propulsion Laboratory has continually worked to extend the life of the spacecraft by troubleshooting issues, performing maintenance, and shutting down various systems to save power. Several of those efforts took place in 2026, when the team spent weeks shutting down three devices and powering on three low-power alternatives in an initiative internally called The Big Bang.

The spacecraft is powered by three radioisotope thermoelectric generators, which are nuclear-powered batteries that generate energy by converting heat from decaying plutonium-238. When it first launched, these generators produced about 470 watts of power. After 50 years in space, they now produce about 215 watts, experiencing an average loss of about 4 watts per year. NASA has already shut down eight of the 10 instruments that the probe carried at launch, leaving only two instruments still in operation following a sudden drop in power earlier.

At its current rate of usage and decay, Voyager 1 is expected to shut down its final science instrument in the 2030s and will eventually lose communication with Earth in 2036 due to insufficient power. While its twin, Voyager 2, has spent a nearly identical amount of time traversing space, it likely will not reach the one light-day distance before its instruments shut down due to a slower speed and trajectory.