Aerospace: research by the Politecnico di Milano protagonist of the launch of the NASA DART impactor

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Divert the trajectory of an asteroid on a collision course with the Earth, by means of a controlled impact at full speed with a space probe. This was the challenge of the DART mission (Double Asteroid Redirection Test) by NASA, successfully completed on 26 September 2022, in which Politecnico was directly involved as part of the scientific team.

The first scientific results on the DART Mission have been published in the authoritative journal Nature in three different articles, co-authored by the researcher Fabio Ferrari from the Department of Aerospace Science and Technology at the Politecnico di Milano.

The article ‘Successful Kinetic Impact into an Asteroid for Planetary Defense’, describes the successful test of kinetic impact technology on the asteroid Dimorphos. The DART mission was the first to test this technology at full scale, demonstrating that it is an effective technique for planetary defence against possible asteroid threats.

The study ‘Ejecta from the DART-produced active asteroid Dimorphos’, describes the observations made using the Hubble Space Telescope on the material ejected by the impact of DART with the asteroid Dimorphos. The observations showed a complex morphology of the ejecta, conditioned by the gravitational interaction between the asteroid and the dust under the influence of solar radiation pressure.

Finally, the effectiveness of the kinetic impact of a satellite in avoiding a potential collision with the Earth is demonstrated in ‘Momentum Transfer from the DART mission Kinetic Impact on Asteroid Dimorphos’ co-authoredby the professor of Flight Mechanics at the Politecnico, Michele Lavagna. The article quantifies the deflection effect produced by the high speed impact on the orbit of the binary system Didymos, showing how the ejection of the fragments generated by the impact helped to increase the efficiency of the energy exchange between the probe and the asteroid.

DART is a historic moment for space exploration: it is not only the first planetary defence test, but it is also the first time we visit a binary asteroid (a system where two asteroids orbit around a common centre of gravity) and where we have the opportunity to observe how an asteroid can react to an external stress,” explains Fabio Ferrari, co-author of the scientific studies on DART. This has allowed us – and will allow us again in the coming months – to study the structure and evolutionary history of these celestial bodies, so close to us but still barely known. The Politecnico di Milano is part of the scientific team of the DART mission and has contributed to studying the evolutionary dynamics of the Didymos binary system. These include the motion and stability of the binary system, as well as the internal structure of the two asteroids Didymos and Dimorphos. The Politecnico has also played a decisive role in the characterization of the motion of the fragments ejected following the impact, and their morphology observed through orbital and Earth-based telescopes.”

It is the first time that an attempt has been made to divert a celestial body from its natural orbital path in a perceptible and significant way and to measure its effectiveness,” adds Michele Lavagna. And it is above all the first time that the impact has been witnessed by an extremely small satellite, LICIACube, the first European probe to travel in deep space. It played a fundamental role in acquiring images during and after the DART impact: images that helped us to understand the composition and structure of Dimorphos and the dynamics of the binary asteroid system, having recorded the sequence of formation of the fragments post impact and their expansion into the surrounding space in the minutes following the collision by DART. The Politecnico di Milano, together with the Italian National Institute of Astrophysics (INAF), contributed to the design and guidance of this small scientific satellite and is actively involved in the scientific analysis of the images acquired to reconstruct the evolution of the motion of the fragments generated.

The Johns Hopkins Applied Physics Lab built and operated the DART spacecraft and manages the DART mission for NASA’s Planetary Defense Coordination Office as a project of the agency’s Planetary Missions Program Office. For more information about the DART mission, visit or . Neither Dimorphos nor Didymos poses any hazard to Earth before or after DART’s controlled collision with Dimorphos

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