Hera Beats the Weather – Sets Sights on Dual Asteroid

The European Space Agency’s Hera spacecraft has lifted off on a unique mission to the binary asteroid pair Didymos and Dimorphos. The probe will seek new insights into planetary defense techniques that could protect the Earth from asteroid impacts in the future, following up on NASA’s DART mission which intentionally struck Dimorphos in September of 2022. Hera’s path to the pad has been winding, and its launch marks the third, albeit conditional, return to flight of SpaceX’s Falcon 9 rocket this year following an incident late last month.

Like Crew-9 before it, Hera’s launch campaign narrowly avoided inclement weather, this time including the looming threat of Hurricane Milton in Florida. Hera lifted off on time at 10:52 AM ET from Space Launch Complex-40 at Cape Canaveral Space Force Station. Falcon 9 booster B1061, completing its 23rd and final mission, flew an expendable profile to help propel Hera on its interplanetary trajectory.

Hera’s mission to Didymos and Dimorphos is closely tied to that of NASA’s Double Asteroid Redirection Test (DART). Originally, both probes constituted the Asteroid Impact and Deflection Assessment, a two-part international partnership to test asteroid deflection using a kinetic impactor. Under this architecture, an ESA-built spacecraft called AIM would have characterized the two asteroids up close for some time, leading up to the arrival of NASA’s DART spacecraft. AIM would then observe from a safe distance as DART collided with Dimorphos at high speed, altering the smaller asteroid’s orbit around its parent. AIM would study the immediate aftermath of the collision in great detail, helping to quantify the effectiveness of this approach to deflecting hazardous asteroids.

When AIM was canceled due to funding challenges, it was promptly reformulated into Hera. Although Hera will still orbit Dimorphos and study it in depth, it will arrive later than originally planned. NASA’s DART spacecraft proceeded to launch in November of 2021 and impacted Dimorphos on September 26, 2022. Observers on Earth, in conjunction with the Hubble and James Webb Space Telescopes, determined that the impact shortened Dimorphos’ orbit by 32 minutes, a much bigger change than expected. The tiny asteroid was violently disrupted by the event, and was seen shedding a dramatic plume of debris into space, forming a short-lived tail like that of a comet. Hera will finally arrive at the system in December of 2026, unveiling the carnage up close for the first time. The spacecraft will witness an asteroid totally reshaped by human activity, a fact reflected in its very name: Dimorphos, meaning “having two forms.”

Hera’s final launch campaign was marred by uncertainty. Before dodging a hurricane, the mission’s fate was thrown into question when its launch vehicle, SpaceX’s Falcon 9, was grounded following an in-flight anomaly. After delivering Crew-9 safely into orbit, the rocket’s upper stage suffered a malfunction during its deorbit burn, causing the stage to impact the ocean outside of its safe disposal area. The Federal Aviation Administration duly launched an investigation into the incident, barring Falcon from future flights until further notice. In an interview with Spaceflight Now, Hera project manager Ian Carnelli acknowledged that this month’s launch window was likely Hera’s only credible path to flight. Ultimately, a one-time waiver from the FAA allowed this mission to fly, though the immediate future for Falcon 9 remains unclear.

In the meantime, Hera is now in space and healthy, talking to ESA controllers with the help of NASA’s Deep Space Network. As it sails out of the Earth-Moon system, the spacecraft’s next major milestone will be a Mars flyby in March of 2025, setting it up for its final encounter with Didymos and Dimorphos. Despite a long and challenging journey, Hera is finally on track to uncover groundbreaking insights into planetary defense—lessons which could one day save millions of lives.

Edited by Scarlet Dominik and Nik Alexander