Hera, ESA’s asteroid investigator


  • The European Space Agency (ESA) will launch the Hera spacecraft in October 2024.
  • Hera will analyze the aftermath of NASA’s DART mission, in which a spacecraft will intentionally strike an asteroid’s moon.
  • Hera will be critically important for understanding the future of planetary defense technology.

In November 2021, NASA’s DART mission will embark on a one-way mission to strike the moon of a near-Earth asteroid. Two years after the spacecraft completes its collision, the European Space Agency (ESA) will send a follow-up, Hera, to measure the literal and figurative impact.

To put it in non-sciency terms: if DART is a call with customer support and Hera is the survey afterward that asks “how did we do?” Basically that, with asteroids.

When will Hera launch?

Though it’s set to launch in October 2024, Hera is not expected to reach its destination until 2026.

Hera ESA's proposed Hera spacecraft would visit asteroid Didymos in 2025 and observe the crater NASA's DART spacecraft creates.Image: ESA / ScienceOffice.org

What will Hera study? Why is it important?

Hera will travel to a binary asteroid system composed of the asteroid Didymos and its moonlet, Dimorphos. They’re about 780 meters (2,560 feet) and 160 meters (525 feet) in diameter, respectively.

Although Didymos and Dimorphos (thankfully) pose no threat to Earth, they pass relatively close to our planet, making them the perfect subject for a scientific walloping. But once DART strikes into Dimorphos, the resulting cloud of dust could make it hard for ground-based telescopes to get a good look at the immediate aftermath.

Hera will investigate the same area a few years later once the coast is clear. The spacecraft will measure the impact crater left behind by DART, allowing scientists to better assess the overall success of the mission. It’ll also take high-resolution images and measurements in order to map Dimorphos in unprecedented detail.

How much did the tiny moon move in orbit? What can this tell us about kinetic impact as a method of planetary defense? These are all questions Hera will be in a unique position to help answer.

Should we be afraid of Dimorphos ping-ponging into Earth once DART smashes into it?

The short answer is: no.

In fact, DART and Hera will help scientists understand how to protect Earth from potentially harmful asteroids. It’ll also help organizations like ours better advocate for more planetary defense missions in the future.

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