The world’s first successful deflection of an asteroid — an inside view of recent findings and what lies ahead
NASA made history when its Double Asteroid Redirection Test (DART) spacecraft, launched with the Light Italian CubeSat for Imaging of Asteroids (LICIACube), successfully crashed into the asteroid Dimorphos on Sept. 26, 2022. Recent findings provide new detail on how the collision changed the asteroid’s shape and orbit in the world’s first planetary defense technology demonstration. Andrea Capannolo, now Purdue assistant professor of aeronautics and astronautics, was mission analyst for the LICIACube mission while serving as a research fellow at Politecnico di Milano. He shares his experience and insights with Purdue Engineering Review.
From the beginning, I have been very proud of my contributions to the DART-LICIACube mission. The concept of a kinetic impactor to deflect asteroids was well known before the mission, but this was the first time this concept was tested on a real asteroid.
I remember the day of DART’s impact very well. I was in France, it was late at night, and the LICIACube team participated in a group call to view real-time images coming from DART during the last minutes before it hit the asteroid.
How in awe all of us were to finally see the system of the asteroid Didymos (with the smaller Dimorphos orbiting around it) and its real shape! It differed significantly from what we were expecting based on the shape models we had seen on our monitors for about four years.
This was the first hint of how unpredictable and uncertain the parameters related to these celestial bodies can be.
A few days later, we started to receive images of the impact from LICIACube. The shape of the ejected material was extremely different from the uniform cloud of dust I was expecting, with clumps and filaments expanding in all directions.
The true surprise came with publication of the first measurements of the impact and Dimorphos’ orbit around Didymos. The impact caused a reduction of about 30 minutes in Dimorphos’ orbit, instead of the predicted six to seven minutes. This difference alone proved the success of the mission, and the extreme effectiveness of the kinetic impactor concept.
DART’s impact raised our hope for the future of planetary defense.
Additionally, it made us think about how much care should be put into the preliminary design of this kind of mission.
For example, during the first stages of development, I needed to understand how close LICIACube could fly next to Dimorphos, considering the ejected particle cloud that the spacecraft needed to avoid to survive the flyby.
To set safety margins, my colleagues and I assumed a “monolithic basalt” composition of Dimorphos (as it was a single, large block of very hard material). According to empirical models, we expected this kind of material would cause the ejected particles from the impact to travel the fastest, about 300 meters per second.
The latest findings from the Italian scientific team of the LICIACube mission, published by Nature, instead show how the irregularly ejected material displayed large variations in particles’ velocity, from a few tens of meters per second (m/s) to almost 500 m/s. This means that, given the designed trajectory and distance from Dimorphos, some parts of the particles cloud could have easily reached and maybe destroyed the spacecraft, if they had developed toward the trajectory path — revelations that are fascinating and scary at the same time.
Another interesting result, covered in the Nature article, deals with the change in the spectrum of the observed ejected particles, moving from red to blue, when observing the surface particles and the inner ejected material respectively. Among various possible explanations for this phenomenon, one theory suggests that the outer material “aged” differently due to exposure to the outer space weather.
The growing value of the LICIACube data demonstrates why small spacecraft, such as CubeSats, are a fundamental element of asteroid-exploration missions. Given their light weight, lesser complexity and lower costs, we can afford these kinds of risks. We can try to fly them closer to asteroids and maximize the amount of scientific data we can obtain, while keeping larger spacecraft — the most expensive assets — at a safer distance.
I predict this trend will become a standard for this type of missions, as indicated by Hera, the next mission toward the Didymos system. The European Space Agency’s Hera is scheduled to launch in October 2024 and, by December 2026, to begin additional study of the asteroids’ properties and long-term effects of the DART impact.
As scientists continue to analyze data from the DART-LICIACube mission and build on its success, we are sharpening our ability to protect the Earth from an asteroid threat. I am thrilled to have contributed to the pioneering mission and look forward to witnessing and hopefully contributing to the next advancements that will enable asteroid deflection on a larger scale.
Andrea Capannolo, PhD
Assistant Professor
Member, Area Committee on Astrodynamics and Space Applications
School of Aeronautics and Astronautics
College of Engineering
Purdue University
