Hera probe heads off to see aftermath of DART’s asteroid impact

The European Space Agency’s Hera spacecraft is on its way to do follow-up observations of Dimorphos, two years after an earlier probe knocked the mini-asteroid into a different orbital path around a bigger space rock.

Scientists say the close-up observations that Hera is due to make millions of miles from Earth, starting in 2026, will help them defend our planet from future threats posed by killer asteroids.

“Hera’s ability to closely study its asteroid target will be just what is needed for operational planetary defense,” Richard Moissl, who heads ESA’s Planetary Defense Office, said today in a news release. “You can imagine a scenario where a reconnaissance mission is dispatched rapidly, to assess if any follow-up deflection action is needed.”

The car-sized probe lifted off from Cape Canaveral Space Force Station in Florida atop a SpaceX Falcon 9 rocket at 10:52 a.m. ET (14:52 UTC) today, just as Hurricane Milton was approaching from the Gulf of Mexico. The day before the launch, forecasters put the chances of acceptable weather at just 15%. Nevertheless, SpaceX persisted.

Due to the mission’s requirements, the first-stage booster couldn’t be recovered this time, as has become the norm for Falcon 9 missions. This was the booster’s 23rd and final mission. A little more than an hour after liftoff, the rocket’s second stage put Hera on its interplanetary trajectory.

During the spacecraft’s two-year cruise to Dimorphos, it’s due to execute a series of course-changing maneuvers, including a swing past Mars that will provide an opportunity for observations of Deimos, one of the Red Planet’s moons.

Hera is returning to the scene of a cosmic crash in 2022 between Dimorphos—which is about 530 feet across, or the size of the Great Pyramid in Egypt—and NASA’s Double Asteroid Redirection Test spacecraft, or DART.

DART was intentionally sent to a collision with Dimorphos to gauge the impact’s effect on the asteroid’s orbit around a larger asteroid known as Didymos. After the crash, scientists determined that Dimorphos’ orbital period had been shortened by 33 minutes, which represented a reduction of roughly 5%. They also identified a plume of debris that extended thousands of miles into space.

Hera is designed to conduct a more detailed “crash scene investigation,” providing data about Dimorphos’ shape and composition as well as the characteristics of the crater left behind by the smash-up.

The spacecraft will deploy two nanosatellites to aid in the investigation: One of the CubeSats, known as Milani, will survey the makeup of Dimorphos and the dust that surrounds it. Meanwhile, the Juventas mini-satellite will perform the first-ever subsurface radar probe of an asteroid. In the later phases of its six-month survey, Hera will test out an experimental self-driving mode as it navigates around Didymos and Dimorphos autonomously.

Data about the aftereffects of DART’s crash will be factored into the plans for deflecting the orbital paths of asteroids, if those paths are ever found to pose a substantial threat of a collision with Earth. Such strategies might require taking action years in advance of an encounter.

“By the end of Hera’s mission, the Didymos pair should become the best-studied asteroids in history, helping to secure Earth from the threat of incoming asteroids,” said Hera mission scientist Michael Kueppers.