As its mission nears the half-century milestone, NASA’s Voyager 1 probe is set to achieve another major milestone by hitting a distance of one light-day from Earth on November 18 at 5:16 a.m. ET, according to NASA.
At that distance, radio signals sent from Earth take 24 hours to reach the probe, and a reply takes another 24 hours to return, creating a minimum round-trip communication delay of 48 hours.
“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,” Suzanne Dodd, Voyager project manager at the Jet Propulsion Laboratory, said in a statement.
Cruising through space at nearly 37,763 mph, Voyager 1 is about 16.1 billion miles from our planet after traveling for nearly five decades.
Crossing the Interstellar Frontier
Launched on September 5, 1977, the twin Voyager probes were originally designed to explore Jupiter and Saturn before continuing their journey toward interstellar space. Voyager 1 became the most distant human-made object in February 1998 and crossed into interstellar space in August 2012, becoming the first spacecraft to do so.
Pascal Lee, a planetary scientist at the SETI Institute who served on the Voyager 2 team at NASA’s Jet Propulsion Laboratory during the 1989 Neptune flyby, remarked to Live Science that the probes are “transcending generations.”
“Not only is their data relevant, but they themselves are still out there, moving into the unknown,” Lee told Live Science.
The twin probes utilized a planetary alignment occurring once every 176 years, using the gravity of giant planets to slingshot themselves onward.
They discovered 23 moons across the outer solar system, revealed faint rings around Jupiter, and captured detailed atmospheric profiles of Saturn, Uranus, and Neptune. Voyager 1 also spotted active volcanoes on Jupiter's moon Io in 1979, the first observation of active volcanism on a world other than Earth.
Managing Dwindling Power Reserves
Fifty years of traversing the solar system and increasing distance from the sun have taken a toll on the spacecraft. Since solar energy is insufficient in the deep reaches of space, Voyager 1 utilizes nuclear batteries that generate electricity by converting heat from decaying plutonium.
That supply is gradually dwindling, prompting NASA to shut down nonessential instruments to conserve energy. The team recently completed an internal initiative called “The Big Bang” on both Voyager 1 and Voyager 2, shutting down specific high-power subsystems and powering on lower-power alternatives.
JPL data systems engineer Kelly Perry, who works on the Voyager program, noted to Live Science in an email that the changes “bought us almost two more years during which we will not need to turn any instrument off.”
Today, only two science instruments remain active on Voyager 1 and three on Voyager 2, measuring magnetic fields, plasma, and cosmic rays. Perry said that the science team decided the last remaining instrument will be the magnetometer, stating, “We will never intentionally power off this instrument.”
Carrying Music Into the Cosmos
Both Voyager probes carry an identical Golden Record, a gold-plated disc curated by a committee chaired by astronomer Carl Sagan to represent life on Earth. The contents include sounds of wind and animal calls, greetings in 55 languages, images of our planet, and musical selections ranging from Chuck Berry’s Johnny B. Goode to classical and traditional global tracks.
Deana Weibel, an anthropologist at Grand Valley State University in Michigan who co-authored an upcoming book about the Golden Record, told Live Science that because Voyager is a science mission, it will be considered finished when no science instruments remain operational.
“Knowing that Voyager will continue its mission long past my lifetime actually gives me comfort,” Perry told Live Science. “Although I won’t be able to speak to the Voyager spacecraft any more, I love knowing that I’ll always be able to look to the stars and know they’re still on their way.”
To celebrate the milestone, NASA invited people worldwide to participate in a Shine Bright for Voyager’s Light-Day event on November 17 by flashing lights toward the sky after sunset, while also uploading the recordings from the Golden Record to SoundCloud for public listening.
Earlier coverage: NASA's Voyager 1 to Become First Human-Made Object to Reach One Light-Day from Earth
