Hera Brakes Toward Asteroid System to Study DART Impact

Scientists are preparing to examine the aftermath of a deliberate asteroid collision as the European Space Agency's Hera spacecraft approaches the Didymos asteroid system. Hera completed its first braking maneuver on October 15, 2026, to adjust its trajectory for an investigation into how NASA's impact experiment changed the smaller asteroid Dimorphos and how effectively such collisions can redirect potentially hazardous objects.

ESA confirmed on October 16 that the 93-minute maneuver, designated BRM-1, met the required parameters. Three hydrazine-based Orbit Control Thrusters fired continuously, while Reaction Control Thrusters maintained the spacecraft's orientation, according to the agency's technical description.

The maneuver was designed to reduce Hera's velocity relative to the Didymos system by several hundred meters per second. ESA planned to evaluate the burn using telemetry, guidance and navigation measurements, ranging data, and Doppler observations.

The next braking maneuver, BRM-2, was scheduled for October 22, 2026. According to ESA's October 16 update, the burn was expected to last approximately 31 minutes, followed by three smaller transition maneuvers toward the end of October.

Hera's investigation builds on NASA's Double Asteroid Redirection Test, which struck Dimorphos in September 2022 at approximately 6.1 kilometers per second, or nearly 22,000 kilometers per hour. Dimorphos measures roughly 160 meters across and orbits the larger asteroid Didymos.

Ground-based observations showed that the collision shortened Dimorphos' orbital period from 11 hours and 55 minutes to approximately 11 hours and 22 minutes. Researchers still need to determine how extensively the impact altered the asteroid's internal structure and how much momentum the collision transferred to it.

Martin Jutzi, an astrophysicist at the University of Bern participating in the mission, said the findings would help scientists calculate the requirements for future asteroid deflection efforts.

"The results will provide a better basis for determining how much energy and momentum are needed to deflect an asteroid of a certain mass. This will allow us to determine how efficiently we can actually deflect an asteroid by colliding with it." Jutzi told Keystone-SDA.

Researchers affiliated with the University of Bern and the International Space Science Institute in Bern have modeled the DART collision. Their simulations suggest Dimorphos is not a solid block of rock but a loosely bound accumulation of debris that may have undergone substantial deformation during the impact.

Hera is expected to test those predictions by examining Dimorphos' surface and impact features. Measuring the asteroid's mass is another key objective because that value will help researchers calculate more precisely how effectively the collision transferred momentum and changed its motion.

Jutzi also highlighted the difficulty of the spacecraft's approach to its destination.

"The arrival is a challenging phase for the mission," Jutzi said.

According to the mission timeline reported by Swissinfo and Bluewin, Hera's Early Characterization Phase was expected to begin in November, when the spacecraft would approach to about 30 kilometers from Dimorphos. Researchers anticipated obtaining the first usable images at that distance, with the planned separation decreasing to approximately 10 kilometers by December.

Hera launched in October 2024 to conduct a detailed examination of the aftermath of the DART experiment. The mission aims to improve scientific understanding of how an asteroid's composition, mass, and internal structure influence the outcome of a deliberate collision.

Jutzi said there was no immediate threat identified in the source reports. According to the same reports, objects measuring 10 to 20 meters across strike Earth statistically every few decades, while asteroids approximately 100 to 200 meters wide could impact Earth on timescales of 10,000 to 20,000 years and cause devastating regional or global consequences.