Hera reaches asteroid system and begins survey

The European Space Agency’s Hera spacecraft reached the Didymos-Dimorphos asteroid system on November 11 and began surveying the pair from about 25 to 30 kilometers away, four years after NASA’s DART spacecraft struck Dimorphos in a planetary-defence test.

ESA said Hera is in an early characterization phase, gathering images and broader observations before moving closer. The spacecraft is following rectangular paths around the binary system rather than a stable circular orbit. ESA’s mission material describes the current survey distance as roughly 25 to 30 kilometers; the weak gravity of the asteroids makes maintaining a circular orbit impractical.

The initial observations are intended to help scientists build a global picture of the system and establish topographic models for more detailed mapping. A first released image shows Didymos clearly, while Dimorphos is mostly hidden behind the larger asteroid. ESA has scheduled a Berlin presentation of a new view of Dimorphos for November 25.

Hera is expected to enter its detailed-characterization phase in December, when it will move to distances of about 20 kilometers. ESA describes the closer phase as an opportunity to examine the...