ESA’s Hera mission launched aboard SpaceX, to probe NASA knocked off asteroid Dimorphos

The European Space Agency’s (ESA) first planetary defense spacecraft has departed planet Earth.

The Hera mission is headed to a unique target among the more than 1.3 million known asteroids in the Solar System – the only body to have had its orbit shifted by human action – to solve lingering mysteries associated with deflection.

By sharpening scientific understanding of the ‘kinetic impact’ technique of asteroid deflection, Hera aims to make Earth safer.

The mission is part of a broader ambition to turn terrestrial asteroid impacts into a fully avoidable class of natural disaster.

Hera launch

The Hera spacecraft, developed as part of ESA’s Space Safety program and sharing a technological heritage with the Agency’s Rosetta comet hunter, was launched on a SpaceX Falcon 9 from Cape Canaveral Space Force Station in Florida, USA, on October 7 at 10:52 local time (16:52 CEST, 14:52 UTC).

Its solar arrays deployed about one hour later.

The automobile-sized Hera will conduct the first detailed survey of a ‘binary’ – or double-body – asteroid, 65803 Didymos , orbited by a smaller body, Dimorphos.

Hera’s main focus will be on the smaller of the two. NASA’s Double Asteroid Redirection Test ( DART ) mission in 2022 changed its orbit around the larger asteroid, demonstrating asteroid deflection by kinetic impact.

“ Planetary defense is an inherently international endeavor, and I am really happy to see ESA’s Hera spacecraft at the forefront of Europe’s efforts to help protect Earth. Here is a bold step in scaling up ESA’s engagement in planetary defense,” said ESA Director General Josef Aschbacher.

To probe asteroids

Hera will also perform challenging deep-space technology experiments, including deploying twin shoebox-sized ‘ CubeSats ’ to fly closer to the target asteroid, maneuvering in ultra-low gravity to acquire additional scientific data before eventually landing.

The main spacecraft will also attempt ‘self-driving’ navigation around the asteroids based on visual tracking.

ESA’s European Space Operations Centre in Darmstadt, Germany, oversees the mission’s launch and deep space journey.

“Hera is finally on its way to Didymos; today, we are writing a new page of space history,” said Hera mission manager Ian Carnelli.

“But the underlying idea of a planetary defense mission based on one spacecraft impacting an asteroid with a second that gathers data goes back two decades, with a significant contribution made by the late Prof. Andrea Milani, a pioneer in asteroid risk monitoring whose name has been lent to one of Hera’s two onboard CubeSats.”

NASA’s DART

Together with NASA and other partner agencies, ESA monitors the sky to identify and track dangerous asteroids.

But if a celestial body was detected on a collision course, what measures could be taken to intercept it? NASA’s DART mission was designed to help address this very question.

On September 26, 2022, the DART spacecraft performed humankind’s first asteroid deflection by intentionally crashing into Dimorphos, the Great Pyramid-sized moonlet of the larger, mountain-sized asteroid Didymos, shifting its orbit.

Based on observations from Earth, DART succeeded in shrinking Dimorphos’s orbit period around Didymos by 33 minutes, nearly 5% of its original value, while casting a plume of debris thousands of kilometers in space.

However, many unknowns remain about the event, which scientists need to resolve to help turn this ‘kinetic impact’ method of asteroid deflection into a well-understood and reliably repeatable planetary defense technique.

How big did DART’s impact leave the crater, or did the entire asteroid undergo reshaping? What is the mineralogy, structure, and precise mass of Dimorphos?

The Hera spacecraft, with a cube-shaped main body measuring approximately 1.6 m across and flanked by twin 5-m solar wings, is ESA’s contribution to this international planetary defense collaboration.

Once it reaches the Didymos binary asteroid in two years, the mission will perform a close-up ‘crash scene investigation’ to gather all the necessary knowledge.

The arrival at Didymos is foreseen for autumn 2026 when the asteroid mission will enter its main science and technology demonstration phase.