NASA’s Voyager 1 Will Become the First Spacecraft One Light-Day From Earth on Nov. 18

NASA’s Voyager 1 is about to reach a distance no human-made object has reached before.

On Wednesday, Nov. 18, at 5:16 a.m. EST, the probe will be one light-day from Earth: 16,094,799,096 miles (25,902,068,356 kilometers) away, according to NASA. That is how far light travels in 24 hours.

Key points:

• Voyager 1 launched on Sept. 5, 1977, and entered interstellar space in 2012.
• A radio message from Earth takes a full day to reach it, and the reply takes another day.
• Its twin, Voyager 2, is expected to reach the same mark in November 2035.

What Is a Light-Day?

A light-day is a measure of distance, not time. It is the distance light travels in one day. NASA says the probe itself will not notice anything when it crosses the mark.

But it does affect how the team talks to the spacecraft. “If you want to say ‘hello’ to Voyager, you send your message and then you go home and you wait two days before you finally get a response,” said Suzanne Dodd, the Voyager project manager at NASA’s Jet Propulsion Laboratory.

A 49-Year Journey

Voyager 1 flew past Jupiter and Saturn before leaving the planets behind. It now travels at nearly 38,000 mph (61,000 km/h), NASA says.

In 1990, it took the famous “Pale Blue Dot” photo, which shows Earth as a tiny speck from 3.7 billion miles away. It also carries the Golden Record, a gold-plated disk with sounds and images of life on Earth.

How Is It Still Working?

The probe runs on heat from decaying plutonium, and its power supply drops by about 4 watts a year. To save energy, the team has already turned off two science instruments. In September, engineers also swapped three devices for lower-power ones so the remaining instruments can run longer.

In October, NASA briefly lost contact with Voyager 1 for about two days after a group of thrusters went offline and backup thrusters took over. The cause is still under investigation. “This is the first time we’ve seen the spacecraft do something like this,” said Voyager mission manager Kareem Badaruddin.

What Happens Next?

NASA plans a “Shine Bright for Voyager’s Light-Day” event on Nov. 17 and a public discussion at JPL on Nov. 19. A NASA documentary about the mission is planned for 2027.

Voyager 1 will keep moving away from Earth. NASA expects it to take about 18,000 years to travel a full light-year, Al Jazeera reported.

Sources:

• NASA: What is a light-day? Voyager 1 will reach one on Nov. 18
• NASA: NASA invites media, public to join Voyager 1 one light-day activities
• NASA Voyager blog: Voyager 1 conserves power, resolves brief communications pause
• Al Jazeera: NASA’s Voyager 1 to hit new space distance record of one light-day

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