Voyager 1 set to become first human-made object one light-day from Earth on 18 November

A distance milestone on 18 November

NASA expects Voyager 1 to reach one light-day from Earth at 10:16 GMT on Wednesday, 18 November. A light-day is the distance light covers in 24 hours, so a radio signal sent from Earth would need a full day to reach the probe at that point. NASA puts that distance at roughly 26 billion kilometers, or more than 16 billion miles. Voyager 1 would be the first human-made object to stand at that range, and it has already travelled farther from Earth than any other spacecraft since its launch. The probe moves at about 61,000 kilometers per hour through interstellar space, the region between star systems. NASA estimates it would need another 18,000 years to cover a full light-year.

From the 1977 launch to interstellar space

Voyager 1 lifted off on 5 September 1977 from Cape Canaveral, Florida, 16 days after its twin, Voyager 2, and later overtook it within months. It swept past Jupiter in 1979 and Saturn in 1980 before leaving the solar system, and it reached what NASA defines as interstellar space in 2012. Voyager 2 also visited Uranus and Neptune and entered interstellar space in 2018, but it is not expected to reach the one light-day mark until 2035. Voyager 1 also took the Pale Blue Dot photo of Earth in 1990.

How people can take part

NASA's Shine Bright for Voyager's Light-Day campaign asks people to point a light at the sky after sunset on Tuesday, 17 November, and flash the letters V-G-R, the probe's call sign, in Morse code. Participants can open a NASA web tool on a phone or tablet, which makes the screen blink the letters automatically, or flash a flashlight, phone light, glow stick, solar lantern or bicycle light themselves. In Morse code, V is three short flashes and one long, G is two long and one short, and R is short, long, short. Participants are asked to repeat the sequence for about a minute, pausing at least one second between letters. NASA also invites people to share photos and videos on social media. The flashes carry no real message to the probe, since communication runs by radio, and antennas such as the Madrid Deep Space Communications Complex in Robledo de Chavela are part of that network.

Operating an aging probe

Voyager 1 and Voyager 2 still send back data almost every day on the strength and direction of the magnetic field, the surrounding pressure, dust and galactic cosmic rays. A skeleton team at NASA's Jet Propulsion Laboratory in Pasadena, California, sends commands about once a week, and more often when problems arise. In September, controllers completed the latest power-conserving effort for the plutonium-powered probe. In October, the team briefly lost communication with Voyager 1, and it has not yet worked out why. Project manager Suzanne Dodd, who has worked with the Voyagers since 1984, described the probe in comments to The Associated Press.

“It's a national treasure.”

Because of the distance, a command and its reply can take about 48 hours, even when the probe answers immediately. Bill Nye of the Planetary Society said in a statement that everyone on Earth has been touched by these missions.