NASA’s Voyager 1 to Reach Historic One Light-Day Distance From Earth

Voyager 1 will become humanity’s first object to reach one light-day from Earth on Wednesday, November 18, crossing a distance of more than 16 billion miles.

Radio signals traveling at the speed of light will take precisely 24 hours to bridge the gap between the spacecraft and Earth. NASA puts the crossing at 05:16:07 EST according to The Register.

The milestone arrives nearly 49 years after the probe launched from Cape Canaveral, Florida, in 1977. While traveling at approximately 38,000 mph, the veteran spacecraft continues to send back engineering and science data from interstellar space. Its twin, Voyager 2, launched two weeks earlier but took a different path past Uranus and Neptune, meaning it will not reach the one light-day mark until 2035, The Journal reported.

“It’s a national treasure,” Suzanne Dodd, Voyager project manager at JPL, told The Journal. “Really extraordinary.”

Celebrating in the Dark

To mark the anniversary, NASA invites participants to flash the mission designation VGR in Morse code using a flashlight or the space agency's website after sunset on Tuesday, November 17. The event aims to create a symbolic wave of golden light across the planet. Voyager 1 cannot see the flashes because its cameras were deactivated decades ago after capturing the iconic “Pale Blue Dot” image of Earth in 1990.

The spacecraft relies on a 23-watt radio transmitter, which produces about the same output as a small refrigerator lightbulb, according to Popular Science. Only massive antennas like the 70-meter-wide dishes in the NASA Deep Space Network can detect the extremely faint signal.

“It’s fun to see what sort of innovation people come up with to keep the spacecraft going,” said Jamie Rankin, a scientist quoted by Popular Science.

Managing Aging Technology

Operating a probe nearly 50 years into its mission brings persistent engineering challenges. Controllers at the Jet Propulsion Laboratory in Pasadena, California, communicate with the spacecraft about once a week, leaning on retired engineers when complex problems arise. In September, mission operators completed another power-conserving maneuver for the plutonium-powered probe, then briefly lost contact with it in October.

Engineers are still investigating the cause of that brief communication disruption. Despite such anomalies, the spacecraft continues to measure magnetic fields, plasma, and cosmic rays from about 11 billion miles away and beyond, operating without instrument heaters that were shut down years ago to conserve power.

Questions about Voyager 1 crossing the one light-day mark

What will happen to Voyager 1 when it crosses the one light-day mark?

Nothing special happens mechanically to the spacecraft at the boundary, as the milestone is purely symbolic. Mission scientists note that operations will continue normally as the probe coasts deeper into interstellar space.

How long does it take to communicate with the probe?

Because radio waves travel at the speed of light, a message sent from Earth takes 24 hours to reach Voyager 1, and another 24 hours for the reply to return. This creates a mandatory two-day waiting period for any command sequence.

When will NASA lose contact with Voyager 1?

Space agency estimates suggest the Deep Space Network will likely lose contact with the aging probe around 2036 as power reserves dwindle and the spacecraft eventually becomes unable to point its antenna toward Earth.

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