Voyager 1 is about to be one light-day from home
On November 18, 2026, a radio signal from the most distant spacecraft ever built will need a full day to reach us.
Light is the fastest thing in the universe. It crosses the gap between Earth and the Moon in a little over a second and reaches us from the Sun in about eight minutes. This November, for the first time, a machine built by people will be so far away that its light, and its radio signal, will need an entire day to get home.
That machine is Voyager 1. NASA expects it to pass the one light-day mark, about 25.9 billion kilometers from Earth, early on November 18, 2026, measured in universal time.
Forty-nine years on the road
Voyager 1 left Florida on September 5, 1977, about two weeks after its twin, Voyager 2. It flew past Jupiter in 1979 and Saturn in 1980, then turned its back on the planets for good. It has been the most distant human-made object since February 1998, and in August 2012 it became the first spacecraft to cross the heliopause into interstellar space.
Since that Saturn flyby it has been coasting at roughly 61,000 kilometers per hour. No spacecraft has ever been this far away, and it is still pulling away.
What a light-day actually means
A light-day is the distance light travels in 24 hours. Once Voyager 1 is that far out, every command the mission team sends will take a day to arrive, and the reply will take another day to come back. As Voyager project manager Suzy Dodd has explained, a “good morning” sent at 8 a.m. on a Monday would get its answer around 8 a.m. on Wednesday.
The signal itself is astonishingly faint. Voyager talks to Earth at about 160 bits per second, slower than an old dial-up modem, and it takes some of the largest radio dishes on the planet to hear it.
Running low, still listening
Voyager runs on radioisotope generators that turn the heat of decaying plutonium into electricity, and they lose a few watts of power every year. To keep it going, engineers have been switching off heaters and science instruments one by one. The power is expected to run out sometime in the 2030s.
Even then, Voyager 1 will keep sailing. Bolted to its side is the Golden Record, a gold-plated disc of sounds, music and greetings from Earth, carried for anyone who might one day find it. It is a message in a bottle on the widest ocean there is.
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