In October 2021, NASA launched its formidable Lucy mission. Its targets are asteroids, two in the principle belt and eight Jupiter trojans, which orbit the Solar in the identical path as Jupiter. The mission is called after early hominin fossils (Australopithecus afarensis,) and the title pays homage to the concept asteroids are fossils from the Photo voltaic System’s early days of planet formation.
Visiting ten asteroids in a single mission is the definition of formidable, and now NASA is including an eleventh.
Astronomers typically confer with asteroids as fossils as a result of they’re remnants from the Photo voltaic System’s early days when the planets have been forming. Their standing makes them necessary objects in piecing collectively the historical past of the Photo voltaic System. One kind of asteroid, known as Rubble-pile asteroids, might be over 4 billion years outdated.
Astronomers are desirous to study extra about asteroids, and whereas chunks that fall to Earth are useful, they’ve limitations. Lately, two separate missions have visited asteroids and gathered samples: Japan’s Hayabusa 2 returned samples from asteroid Ryugu in December 2020, and NASA’s OSIRIS-REx mission will return samples from asteroid Bennu in September 2023.
Lucy gained’t be bringing any samples house, nevertheless it’ll be observing 10 totally different asteroids intimately throughout separate flybys. The spacecraft has some of the sophisticated paths of any mission. An in depth itinerary is critical for the spacecraft to go to two teams of Jupiter’s Trojan asteroids.
However now NASA has added one other asteroid to Lucy’s busy itinerary. It gained’t want to change its course to go to this one. As a substitute, it presents itself as a goal of alternative in the principle asteroid belt.
All of Lucy’s targets are in fixed movement, and mixing Earth flybys with visits to separate teams of asteroids is daunting. Different spacecraft have visited a number of objects with flybys, however none have ever tried to go to as many as Lucy is. Visiting all these asteroids requires a complicated, asteroid-tracking navigation system.
“There are two methods to navigate a mission like Lucy,” said Jacob Englander, the optimization technical lead for the Lucy mission. “You possibly can both burn an unlimited quantity of propellant and zig-zag your manner round looking for extra targets, or you may search for a chance the place they simply all occur to line up completely.”
Mission designers have calculated the place all of Lucy’s targets shall be years prematurely, however that doesn’t imply it isn’t sophisticated. Optical navigation continues to be needed when Lucy approaches one among its targets. Digicam photographs are mixed with monitoring knowledge to find out the spacecraft’s precise place.
That’s the place the extra go to to a different asteroid is available in.
The asteroid is within the interior essential belt and is designated (152830) 1999 VD57. It’s a goal of alternative that may permit mission operators to check Lucy’s navigation system earlier than it visits its scientific targets.
“There are hundreds of thousands of asteroids in the principle asteroid belt,” mentioned Raphael Marschall, Lucy collaborator on the Good Observatory in France, who recognized asteroid 1999 VD57 as an object of particular curiosity for Lucy. “I chosen 500,000 asteroids with well-defined orbits to see if Lucy could be travelling shut sufficient to get an excellent take a look at any of them, even from a distance. This asteroid actually stood out. Lucy’s trajectory as initially designed will take it inside 40,000 miles of the asteroid, at the least 3 times nearer than the subsequent closest asteroid.”
If a big, propellant-intensive maneuver was wanted to go to the brand new asteroid, NASA wouldn’t have thought of it. However that’s not the case. It may be added with solely a small maneuver.
It’s being added due to its worth as an engineering check, in keeping with NASA. And it’ll deal with a difficulty that’s explicit to visiting smaller, quickly transferring objects like asteroids: as a spacecraft approaches one, it’s tough to find out the spacecraft’s precise place in relation to the asteroid. That makes it tough to know the place to level its cameras.
“Prior to now, most flyby missions have accounted for this uncertainty by taking a number of photographs of the area the place the asteroid could be, that means low effectivity and plenty of photographs of clean house,” mentioned Hal Levison, Lucy’s principal investigator from the Southwest Analysis Institute Boulder, Colorado workplace. “Lucy would be the first flyby mission to make use of this modern and complicated system to routinely monitor the asteroid in the course of the encounter. This novel system will permit the crew to take many extra photographs of the goal.”
Monitoring the asteroid in the course of the encounter relatively than counting on pre-existing photographs isn’t with out threat. However due to 1999 VD57’s orientation, Lucy’s flyby of the asteroid can function a gown rehearsal for its modern manner of navigating. The geometry of the encounter is analogous sufficient to the spacecraft’s eventual flybys of the Trojan asteroids that NASA can apply for its rendezvous with its scientific targets.
The asteroid is small and was by no means thought of a goal when NASA was designing the Lucy mission. It’s solely about 700 metres (0.4 miles) in diameter. It’ll be the smallest main-belt asteroid ever visited. It’s nearer in dimension to Bennu and Ryugu, the near-Earth asteroids that have been visited and sampled in recent times.
Lucy’s authentic trajectory would’ve taken it to inside 64,000 km (40,000 miles) of the small asteroid. However the brand new trajectory will convey it to inside 450 km (280 miles) of the goal.
The Jupiter Trojans are attention-grabbing targets as a result of they’re totally different than main-belt asteroids. Their surfaces are darkish and replicate little mild. They’ve been trapped in Jupiter’s orbit for billions of years. Whereas they’re known as asteroids, a paper outlining Lucy’s science objectives refers to them as planetesimal from the outer Photo voltaic System. Based on that paper, “They might have initially fashioned far past their present house (at ?15–30 au) and have been transported to their present places by early orbital evolution of the large planet orbits.”
Fundamental-belt asteroids should not as outdated and should not pristine. They’ve been subjected to house weathering, heating, and collisions. They’re attention-grabbing scientific targets for various causes.
However the Trojan asteroids haven’t been subjected to the identical forces and are preserved primordial objects from our Photo voltaic System’s early days. Throughout the Trojan asteroids, there are totally different taxonomic varieties, and Lucy will go to representatives of the different sorts, together with a collisional member of the family and a close to equal-mass binary. Its targets vary from about 1km in diameter to 100 km in diameter.
We’ve solely visited eight main-belt asteroids to this point, and people visits revolutionized our understanding of each the asteroid belt and planetary formation within the Photo voltaic System. The Jupiter Trojans are unvisited, and Lucy will go to eight of them in a single mission. They’re a reservoir of early Photo voltaic System objects that virtually beg to be explored and have been serendipitously introduced into attain by the migrations of the large planets.
In Could 2023, Lucy will begin a sequence of maneuvers that may convey it near its new goal. Hopefully, this late addition to Lucy’s itinerary will make their exploration extra fruitful.
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