The probe was launched in 1977 but it continues to relay space-related data back to a team of NASA scientists daily.

NASA has announced that its Voyager 1 probe will soon become humanity’s first object to travel one light-day from Earth.

On Wednesday, the robotic space probe will hit the milestone of travelling at least 16 billion miles since its launch in 1977, a distance equal to one light-day, or how far light can travel in 24 hours.

The probe completed its Saturn flyby in 1980, the end of its primary planetary mission, and is currently travelling at roughly 36,000 miles per hour (58km/h) in interstellar space, the vast gap between stars.

NASA expects it to take 18,000 years to travel a full light-year, and double that before it nears another star.

Plutonium-powered Voyager 1 was launched shortly before another probe, Voyager 2. Both continue to relay data back to Earth daily, including readings on the strength and direction of the magnetic field as well as on the surrounding pressure, dust and galactic cosmic rays.

Voyager 2 is expected to hit one light-day from Earth in 2035.

Both are kept active by a skeleton team of NASA engineers who send commands roughly once a week, and more if the probe gets into trouble.

In October, the team briefly lost communication with Voyager 1, and they have not yet figured out why.

Voyager 1 project manager Suzanne Dodd described Voyager 1 as “a national treasure” and told The Associated Press news agency that the two probes’ activities are akin to that of weather satellites.

The probe’s cultural impact has been significant. The famous “Pale Blue Dot” photo of Earth was taken by Voyager 1 in 1990.

“All of us — everyone on Earth — have been touched by these missions,” the Planetary Society’s Bill Nye said in a statement.