The European Space Agency (ESA) is preparing to launch its Hera mission into a historic rendezvous with the Dimorphos-Didymos asteroid pair. Moving at a relative speed of 12 kilometers per second, the spacecraft is tasked with providing a detailed follow-up view of the 'scars' left by NASA’s Double Asteroid Redirection Test (DART). In 2022, the DART mission successfully slammed into the smaller moonlet, Dimorphos, to test the feasibility of redirecting asteroids as a planetary defense strategy. Hera will now provide the close-up data necessary to understand the physical consequences of that impact.
This rendering visualizes the Hera spacecraft's approach to the asteroid pair to inspect the DART impact site.
Didymos is a 780-meter-wide asteroid that orbits the Sun every 2.1 years, accompanied by its 151-meter-wide companion, Dimorphos. Both bodies are described as 'rubble pile' asteroids—collections of rocks held together by weak gravity that are near their structural limits. The DART impact successfully shortened Dimorphos's orbital period by approximately 32 minutes and generated a visible debris stream. Hera’s primary role is to acquire baseline measurements of these asteroids from a distance of 25 to 30 kilometers, providing the first high-resolution post-impact views of the surface and the surrounding environment.
To expand the scope of the mission, Hera will deploy two CubeSats: Juventas and Milani. These smaller satellites will perform specialized tasks; Milani will analyze the dust field and spectral composition of the pair, while Juventas will compare the internal structures of the asteroids and may even attempt to come to rest on the surface of Dimorphos. These observations are critical for refining models of how kinetic impacts affect different types of asteroid compositions. After completing its nominal mission in 2027, Hera may be extended as a technology demonstrator to test autonomous spacecraft control techniques.