NASA’s Lucy spacecraft is about to make its very first flyby of an asteroid on Wednesday, Nov. 1.
When Lucy flies past the half-mile-wide asteroid, named Dinkinesh, the moment will mark the start of the probe's 12-lear-long tour of 10 asteroid subjects. Ultimately, the planned legacy of this spacecraft is for it to become the first to investigate the Trojan asteroids — asteroids that follow Jupiter’s orbit around the sun and are believed to be remnants of our solar system's formation.
Lucy has been preparing for its visit to Dinkinesh since Sept. 3, keeping the tiny asteroid in its sights to the best of its ability. But on the first day of November, the spacecraft will get its first close look at the space rock.
"This is the first time Lucy will be getting a close look at an object that, up to this point, has only been an unresolved smudge in the best telescopes," Lucy principal investigator and Southwest Research Institute (SwRI) researcher Hal Levison said in a statement. "Dinkinesh is about to be revealed to humanity for the first time."
Lucy launched at 5:34 a.m. EDT (0934 GMT) on Oct. 16, 2021, from Kennedy Space Center, Cape Canaveral, Florida, atop an Atlas V rocket. Then, the spacecraft returned to Earth for a gravity assist one year later, on Oct. 16, 2022. Passing 220 miles (350 kilometers) above the surface of Earth, Lucy was slingshot toward the main asteroid belt around 300 million miles (480 million kilometers) away — which brings us to now.
Lucy's past: What’s in a name?
Planning for the Lucy mission began when the project — part of the 2014 Discovery Program Announcement of Opportunity (AO) — was selected by NASA in 2017 from 28 proposals that had to be ready for a 2021 launch. Lucy was originally given its name from The Beatles' song, "Lucy in the Sky With Diamonds," but the moniker also has scientific inspiration. The Lucy mission shares its name with a famous fossil of one of the oldest known human ancestors that's part of the Australopithecus afarensis species. Interestingly, "Dinkinesh," an Ethiopian word that translates from Amharic to "you are marvelous," is actually another name for that same fossil.
And, just as Lucy the fossil revealed important details about the origins of our species, Lucy the spacecraft promises to reveal more about the origins of our cosmic neighborhood. The latter will do so by investigating asteroids (the Trojan asteroids) believed to be primordial "fossils" of our solar system, made of material left over from the creation of the planets. That means these asteroids are likely at least 4.6 billion years old, as that's around when our solar system formed. It also means the composition of those Trojan asteroids could show us what elements were present when the Earth was still coming together.
The asteroid Dinkinesh was only given its Lucy-related name in Feb. 2023. Its previous designation was the less snappy title of "1999 VD57." Dinkinesh's new name officially arrived in January of this year, following the decision to add Dinkinesh to Lucy’s itinerary. Since then, Lucy operators also lovingly nicknamed the space rock "Dinky."
Lucy's Present: Hello 'Dinky'
On Nov. 1, Lucy will reach Dinkinesh — and at 12:54 EDT (1654 GMT), it will make its closest approach to the asteroid, coming to within 270 miles (430 kilometers) of the space rock’s surface.
This will be far more than a social visit, as Lucy’s flyby of Dinkinesh is expected to represent an important test of the spacecraft’s instruments prior to its Trojan asteroid destination. An hour before its close approach of Dinkinesh, for instance, Lucy will begin tracking the target using its terminal-tracking system.
Then, around 8 minutes before close approach, the spacecraft will begin collecting data about Dinkinesh with its color imager and infrared spectrometer. Once close enough to the asteroid, Lucy will begin collecting data with its high-resolution camera (L'LORRI) and its thermal-infrared camera (L'TES). Such continuous imaging and tracking of Dinkinesh will continue for almost another hour.
"We'll know what the spacecraft should be doing at all times, but Lucy is so far away it takes about 30 minutes for radio signals to travel between the spacecraft and Earth, so we can’t command an asteroid encounter interactively," Mark Effertz, Lucy's chief engineer at Lockheed Martin Space said in the statement. "Instead, we pre-program all the science observations. After the science observations and flyby are complete, Lucy will reorient its high-gain antenna toward Earth, and then it will take nearly 30 minutes for the first signal to make it to Earth."
After Lucy has reoriented itself and resumed communications with Earth, the spacecraft will then continue to periodically image Dinkinesh with L'LORRI over the next four days as it bids farewell to the asteroid.
Lucy's Future: Hunting the Trojans
Following this important test of Lucy’s instruments, the spacecraft will head back to Earth for yet another gravity assist in Dec. 2024. That push will send it back to the main asteroid belt between Mars and Jupiter, leading to Lucy’s second asteroid flyby scheduled to take place on April 20, 2025. This flyby will be of another main asteroid belt body, the 2.5-mile-wide (4-kilometer-wide) space rock dubbed 52246 Donaldjohanson — named after co-discoverer of the Lucy fossil, American paleoanthropologist Donald Johanson.
After this, Lucy will finally zoom on toward the two swarms of Trojans anchored to the orbital path of Jupiter.
Its first Trojan flyby target is slated to happen in Aug. 2027 and be of the 40-mile-wide (64-kilometer-wide) asteroid named 3548 Eurybates. 3548 Eurybates is also accompanied by a small, merely half-mile (1 kilometer) space rock satellite named Queta — meaning this will be a "two-for-one" flyby experience for Lucy .
Lucy’s next target will be the dark, reddish asteroid 15094 Polymele. It'll fly by this space rock in Sept. 2027. At 13 miles (21 kilometers) in diameter, 15094 Polymele is the smallest of Lucy’s subjects. And in fact, Polymele is also accompanied by a partner. This partner isn't officially named yet, but scientists have t nicknamed it "Shuan." Hopefully, Lucy will also catch a glimpse of Shuan.
After this, next up for Lucy will be a flyby of the 25-mile-wide (40-kilometer-wide) Trojan asteroid 11351 Leucus, a pass expected to happen in April 2028. Because this asteroid rotates very slowly, it gets much hotter during its day and colder at night. The slow speed is a good thing for astronomers, however, because it means we can learn more about what material comprises the asteroids as it sluggishly moves.
In Nov. 2028, Lucy will pass by the 32-mile-wide (51-kilometer-wide) asteroid 21900 Orus, another dark red asteroid believed to be rich in organic material and carbon.
Last but not least, the final encounter of Lucy’s primary mission will be another two-in-one situation as the spacecraft flies past the binary pair of asteroids, 617 Patroclus and Menoetius. Lucy is heading for a big finish as these Trojan asteroids are the largest space rocks on its itinerary at 70 miles (113 kilometers) and 65 miles (104 kilometers) wide, respectively. Just visiting those asteroids would be a massive achievement in itself, as they orbit the sun at a high inclination above the plane of the solar system and are thus very difficult for spacecraft to reach.
The binary asteroids will be passing a region that Lucy can access in March 2033. But the journey officially starts on Nov. 1, with little Dinky.
