Voyager 1 is about to reach one light-day from Earth
NASA expects the probe to cross the threshold on November 18. A radio signal will take a full day to reach it.
On November 18, NASA expects Voyager 1 to be about 25.9 billion kilometres from Earth. At that distance, a signal travelling at the speed of light takes 24 hours to reach the spacecraft. A reply sent immediately would take another day to come back.
Voyager 1 launched in 1977 and crossed into interstellar space in 2012. Its twin, Voyager 2, took a different route and reached interstellar space in 2018. Both continue to send observations from beyond the heliosphere, the region shaped by the solar wind. NASA uses its Deep Space Network to communicate with the probes.
NASA’s calculation places the milestone at 5:16 a.m. US Eastern time (10:16 UTC). The agency has invited people to mark the occasion on November 17 with a web tool that flashes the letters VGR in Morse code.
On November 19, the Jet Propulsion Laboratory plans a public discussion about the observations the probes still make and the work involved in keeping them operating so far from Earth.