Hera has entered “rectangular orbits” 30-25 km from Didymos and Dimorphos, starting its first survey of the binary asteroids after arriving at the system.
The early characterization phase will capture global images of Dimorphos to show how NASA’s 2022 DART collision altered the 151-meter moonlet’s orbit, shape and possible crater.
ESA chose the unusual flight path because gravity is extremely weak—about 40,000 times weaker than Earth’s at Didymos and 200,000 times weaker at Dimorphos’s orbit—making circular orbits impractical.
In about a week, Hera will fire thrusters twice to turn 90 degrees while moving at just 12 cm per second; if a burn fails, ESA says the craft would drift away rather than hit the asteroids.
The mission shifts to a detailed phase in December at roughly 20 km, before deploying the Juventas and Milani CubeSats in coming months to gather more data and eventually land on Dimorphos.