Lucy Flyby Sharpens NASA Readiness for Jupiter Trojan Operations
When NASA’s Lucy spacecraft encountered asteroid Donaldjohanson on April 20, 2025, it wasn’t just about an odd science target. This encounter also helped prepare the deep-space mission in advance of a much more important objective: studying Jupiter’s Trojan asteroids.
First, the scientific finding is impressive enough on its own right. The asteroid turned out not to have a simple rotation like one can imagine for such an astronomical object. Rather, Donaldjohanson seems to rotate around two axes, meaning it tumbles or wobbles while traveling in outer space. The images captured during the flyby confirmed that the asteroid is bilobate, having an elongated shape with a neck between two lobes, making it resemble a peanut. The presence of such an object morphology was inferred based on previous Earth-based telescopic observations.
The above facts were presented in a recent publication in Science titled “The Lucy flyby of (52246) Donaldjohanson: A bilobed asteroid with tumbling rotation,” by Simone Marchi, the deputy principal investigator of the Lucy mission. But the main value of this encounter for the aerospace industry is that Donaldjohanson provided a chance to test mission procedures before reaching the main target of the Lucy project. Marchi commented, “This encounter gave us an opportunity to test our instruments and our procedures to make sure we are ready when we get to Jupiter’s Trojans.”
It is necessary because asteroid flybys aren’t just an opportunity to see something unusual. This is a complex procedure involving timing, pointing, imaging of a specific object and receiving data about its properties. A close approach to a small and irregularly shaped object is one of the occasions which allows testing whether observation procedures, imaging capabilities and mission teams are prepared to cope with future challenges.
At the same time, Donaldjohanson encounter provided the mission team with an object suitable for science research in addition to being tested on. Thus, Lucy images confirmed the geometry of the asteroid, and also scientists detected iron-rich clays in it, implying that there were liquid water processes in the past. Researchers believe that the asteroid formed after a collision of a large asteroid with carbon and water content in the main asteroid belt 155 million years ago.
Such an additional information obtained during the encounter is also crucial for building up confidence in future success of a deep-space mission. While proving the ability to flyby the target, the mission needs to prove that it is able to obtain reliable information about the surface and minerals of the encountered object. In other words, the Lucy encounter with Donaldjohanson is not just a demonstration of navigation skills, but a comprehensive test of a mission capability to extract science information from fast-mov ing objects.
In turn, Lucy’s next phase will be much more challenging. The spacecraft is moving towards Trojan asteroids associated with Jupiter’s orbit. These ancient celestial objects are of great scientific interest, since it is believed that they haven’t changed since the origin of the solar system, making them valuable records of early solar system history. But at the same time, each encounter will have significant scientific value, leaving limited room for procedural surprises.
And that’s why such an intermediate flyby is so crucial for space missions’ operations. Mission teams have an opportunity to work out observation sequences, to ensure proper functioning of their instruments and to evaluate in-flight performance in comparison with initial expectations. For Lucy, Donaldjohanson offered a complex object (with unusual rotation, bilobate shape and mineral signature) to be encountered before the start of the Trojan mission.
Finally, there is an important context of the U.S. space program here. NASA missions traditionally build up confidence step-by-step, validating not only their hardware, but also human operations (planning, procedure execution, scientific analysis). And Lucy’s encounter with Donaldjohanson can be viewed as such a step as well. In addition to delivering a scientific result, this encounter can be considered as a rehearsal for the upcoming mission phase.
Trojan asteroids could actually challenge our understanding of the origin of our solar system since they constitute “a completely different population of space rocks with very different histories,” Marchi noted. This is the scientific potential of the mission. But for NASA, it is crucial to approach these objects with already proven in-flight and operational experience.
This is the real significance of Donaldjohanson. The asteroid with wobbling rotation and unusual shape is interesting in terms of science, but for mission readiness purposes, it is even more important as a systems verification test. Now, before starting investigation of some of the oldest preserved solar system bodies, NASA knows how its spacecraft and teams perform when the clock is ticking and the target is not theoretical anymore.
By David Whitaker – Associate editor for AMI’s aerospace and drone systems desk, covering flight systems, aircraft programs, spaceflight and UAV developments.
