Brake! Time for ESA’s Hera asteroid mission to go slow
ESA’s Hera spacecraft will execute critical braking manoeuvres starting 15 October to slow its approach to the Didymos binary asteroids, marking its most challenging activity since launch.
The European Space Agency’s Hera mission, launched from Cape Canaveral Space Force Station in Florida on 7 October 2026, is now preparing for sustained braking manoeuvres to slow its approach to the Didymos binary asteroids. After two years of travel, Hera has relied on Newtonian physics and a Mars flyby in spring 2025 to adjust its trajectory and speed. Currently moving at over 12 kilometres per second relative to Earth, the spacecraft is closing in on the asteroid system, requiring precise deceleration to match their orbital velocity.
On Tuesday 15 October, Hera will rotate to align its Orbit Control Thrusters toward the Didymos system and ignite three hydrazine-based thrusters simultaneously for 93 minutes. This burn aims to reduce Hera’s velocity relative to the asteroids by a few hundred metres per second, a complex operation requiring coordination with Reaction Control Thrusters to maintain spacecraft attitude. A test burn on 2 October validated the sequence before full implementation.
Following the initial braking manoeuvre, ESA’s Flight Dynamics team will analyse telemetry and sensor data from Hera’s GNC system to confirm the burn’s effectiveness. The team will assess the delta-v change and direction using ranging and Doppler data from ESA’s 35-metre deep space antenna in New Norcia, Australia. This phase is critical for validating the spacecraft’s trajectory adjustments before proceeding to the next manoeuvre.
A second shorter braking burn, BRM-2, is scheduled for early Thursday 22 October, lasting approximately 31 minutes. This manoeuvre will complete most of the required delta-v to match the Didymos system’s velocity, compensating for any discrepancies from BRM-1. Three additional smaller transition manoeuvres later in October will further reduce Hera’s relative velocity to near zero, enabling its close-up investigation of the asteroid Dimorphos.