spaceSpace and Physics

This Reborn ESA Spacecraft Will Find Out If We Can Save Earth From An Asteroid


Jonathan O'Callaghan

Senior Staff Writer

Hera will scan the smaller asteroid with lasers. ESA-ScienceOffice

A European spacecraft will head to an asteroid next decade on a mission of planetary defense – but only after its predecessor was canceled due to a lack of funding.

The mission from the European Space Agency (ESA) is called Hera, and it will launch towards a pair of near-Earth asteroids called Didymos in 2023, arriving in 2026. The former called Didymain is 780 meters (2,600 feet) across, while the latter known as Didymoon is 160 meters (525 feet).


Hera will focus on the smaller Didymoon, taking high-resolution pictures and mapping the asteroid with lasers and radio waves. This would be the smallest asteroid a spacecraft has ever visited, and almost the first mission to a binary asteroid – two asteroids orbiting each other.

We say almost because Hera will actually be beaten to the pair of asteroids by NASA’s Double Asteroid Redirection Test (DART). In October 2022, this mission will slam into Didymoon and attempt to very slightly change its orbit.

Observatories on Earth will track the subsequent change in the asteroid’s orbit. But Hera, when it arrives, will be used to see how much the orbit has changed up close. This could tell us if an impactor is a viable method to push an asteroid out of our path. If there was an asteroid with our name on it in the future, then hitting it with an impactor years in advance might be a way to make it miss us.

After DART slams into Didymoon, Hera will study the resulting crater and its change in orbit. ESA-Science Office

“Such a binary asteroid system is the perfect testbed for a planetary defence experiment but is also an entirely new environment for asteroid investigations,” Hera manager Ian Carnelli said in a statement. “Although binaries make up 15 percent of all known asteroids, they have never been explored before, and we anticipate many surprises.”


This is all a little bit awkward though, because ESA was originally supposed to fly with NASA on this mission with a spacecraft called the Asteroid Impact Mission (AIM). That would have studied the impact and the resulting motion up close alongside DART, launching in October 2020, but ESA canceled the mission in 2016.

So, instead, they’ve decided to fund a separate mission that will arrive at the asteroid four years later. In comments sent to IFLScience, Carnelli said that they had "gone into mission reformulation and missed the 2020 launch date" after the funding cancellation in 2016. "Hera, the further optimisation of AIM, can now launch realistically in 2023 the earliest," he added.

The mission will be hugely exciting regardless though. ESA said Hera has now entered its next engineering phase, while DART has passed its preliminary design review and is moving to its detailed design stage. Here’s hoping for no cancellations this time around.


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