NASA’s Lucy begins long journey around solar system after launch
The first leg of Lucy’s wild, looping voyage is underway.
The NASA spacecraft launched Saturday at 4:34 a.m. from the Cape Canaveral Space Force Station in Florida. Its 12-year mission will visit asteroids that share Jupiter’s orbit around the sun and could unlock secrets to the formation of planets in our solar system.
Lucy will fly by one asteroid in the main asteroid belt, located between Mars and Jupiter; five Trojan asteroids that orbit ahead of Jupiter; and two Trojan asteroids that orbit behind Jupiter. These Trojan asteroids are remnants of the material that formed the outer planets.
To reach all eight asteroids — the most by a single spacecraft — Lucy will have a trajectory that was “part science, part art and part luck,” Hal Levison, Lucy’s principal investigator with the Southwest Research Institute, said during a news conference.
Lucy will initially orbit the sun for one year. Around this time next year, it will line up with Earth and get a gravity assist that pushes Lucy on a two-year elliptical trajectory beyond the orbit of Mars. In 2024, the spacecraft will approach Earth again and get a boost toward Donaldjohanson in the main asteroid belt and the Trojan asteroids orbiting ahead of Jupiter.
Lucy will visit its first Trojan asteroids, Eurybates and its satellite Queta, in August 2027. It will fly past Polymele in September 2027, Leucus in April 2028 and Orus in November 2028. The spacecraft then returns to Earth, gets yet another gravity assist in 2031 and is flung toward the asteroids orbiting behind Jupiter. It will reach Patroclus and Menoetius, a binary pair of asteroids that are roughly the same size and orbit each other, in March 2033.
“When I first saw that (trajectory),” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, “I looked at this like, ‘You’ve got to be kidding me. This is possible?’ ”
The Trojan asteroids share an orbit with Jupiter, but they’re not actually close to the planet. The Trojans are as far away from Jupiter as they are from the sun.
That means Lucy will travel nearly 4 billion miles in 12 years.
“What’s amazing about this trajectory is we can continue to do loops,” said Coralie Adam, Lucy’s deputy navigation team chief at KinetX Aerospace. “So after the fi
nal encounter with the binary asteroids, as long as the spacecraft is healthy, we plan to propose to NASA to do an extended mission and explore more Trojans.”
Lucy was built by Lockheed Martin Space and launched Saturday atop a United Launch Alliance Atlas V rocket.
When the spacecraft flies through the Trojan asteroids, it will have traveled farther from the sun than any other solar-powered spacecraft (the record is currently held by the Juno spacecraft that’s orbiting Jupiter). Its far-flung predecessors relied on nuclear power.
Solar power is preferred for its lower cost — the Lucy mission cost $981 million — and for safety reasons.
“The solar arrays that we use on this mission are really going to prove and pave the way for solar technology,” Cory Prykull, Lucy’s assembly, test and launch mechanical operations lead at Lockheed Martin Space, told the Houston Chronicle. “(It’s) going to unlock other smaller missions to be able to go to the outer planets. If we prove out this technology, it’s going to make it cheaper, it’s going to make it more accessible, for other missions that can go out there.”
The spacecraft has two solar arrays that each measure 24 feet in diameter. They are so big that Lockheed Martin wasn’t able to open them simultaneously when testing here on Earth. Prykull described a “song and dance” where Lucy’s team opened one solar array, closed it, moved the spacecraft and then opened the other solar array.
These solar arrays will generate 18,000 watts of power near Earth. Katie Oakman, Lucy’s structures and mechanisms lead at Lockheed Martin Space, said that’s enough to power her house and a couple of her neighbors.
Near the Trojan asteroids, Lucy’s solar arrays will generate just 500 watts of power. This would turn on a few lights in the living room but not power the microwave. Yet it’s sufficient for Lucy’s science instruments, which will need 82 watts of power when flying by the asteroids. The spacecraft will not orbit these asteroids and, on average, will fly past them at 15,000 mph.
“It’s super important to us to collect as much data as we can and not miss it on that one opportunity,” Joan Salute, associate director for flight programs in NASA’s planetary science division, said during a news conference.
The Trojan asteroids are like fossils of planetary formation. As such, the mission was named for the fossilized skeleton of an early human species. Lucy is a collection of bones (about 40 percent of a full skeleton) that was found in Ethiopia in 1974. They’re believed to be roughly 3.2 million years old.
Paleoanthropologist Donald Johanson, who was among the team that found the fossilized remains, was at the launch Saturday. The first asteroid Lucy will visit, the one in the main asteroid belt, was named after Johanson.
But Lucy isn’t just looking to the past. It will carry a message for our descendants.
The spacecraft could travel between Earth and the Trojan asteroids for hundreds of thousands of years, perhaps millions of years. Future generations might one day retrieve it as relic from humanity’s early exploration of the solar system.
They would then find a plaque depicting the positions of the planets when Lucy launched. They would also read messages from prominent thinkers of our time.
“I’m writing to you from a world you’ll have a hard time imagining, to a world I can’t picture no matter how hard I try,” reads a message from Serbian American poet Charles Simic, a Pulitzer Prize winner for poetry and Poet Laureate Consultant in Poetry to the Library of Congress. “Do you still have birds that wake you up in the morning with their singing and lovers who gaze at the stars trying to read in them the fate of their love? If you do, we’ll recognize one another.”