European Spacecraft Arrives at Asteroid System for Impact Site Survey

The European Space Agency announced on Wednesday that its Hera spacecraft has arrived at the binary system consisting of the asteroid Didymos and its moonlet Dimorphos. Positioned at a distance between 25 and 30 kilometres from the asteroids, the probe has begun low-altitude observations of both bodies. The operational phase marks the start of a detailed follow-up investigation into the kinetic impact test conducted by NASA in 2022.

The target system underwent structural changes four years ago when NASA's Double Asteroid Redirection Test, known as DART, intentionally crashed into Dimorphos to evaluate planetary defense techniques against potential asteroid threats to Earth. The collision shortened the orbital period of the moonlet around Didymos and shifted its trajectory around the Sun. ESA officials described the newly initiated observations as a crash site investigation to determine the exact extent of the orbital and physical modifications.

The DART impact knocked boulders and rubble off Dimorphos, which measures approximately 151 metres in diameter, while Didymos has a diameter of roughly 780 metres. The resulting debris trail extended more than 10,000 kilometres into space and persisted for months. Scientists associated with the project noted that some of this material could still remain in the immediate vicinity of the asteroids.

To analyze the system, the car-sized Hera spacecraft, which was launched in 2024, carries 25 scientific instruments along with two shoebox-sized CubeSats. These smaller secondary satellites are configured to survey Dimorphos from closer distances and will attempt to land on its surface. Mission plans specify that Hera will decrease its orbital distance to 20 kilometres next month to conduct further measurements.

Written by Andreas Hofer andreas.hofer@alpineweekly.com