Hera
What is Hera?
Probes & telescopes· Launched 2024-10-07 – arrives 2026-12 (under way). ESA's planetary-defence mission returning to Dimorphos, the asteroid NASA's DART struck in 2022. Launched in 2024, it reaches the Didymos binary in December 2026 to measure the crater, mass and interior — completing humanity's first asteroid-deflection experiment.
The orbit of Hera at this moment: https://nowsky.org/solar/orbit?fw=probe%3Ahera&sp=2.6 — replayed live, no login.
Mission timeline
Spacecraft specs
| Launch | 2024-10-07 |
|---|---|
| Mars flyby | 2025-03-12 |
| Arrival | December 2026, Didymos system |
| CubeSats | Milani and Juventas |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When did Hera launch?
- 2024-10-07.
- What is the next milestone for Hera?
- 14 Dec 2026 — Hera arrives at Dimorphos.
- In one line, what is Hera?
- Probes & telescopes — ESA's planetary-defence mission returning to Dimorphos, the asteroid NASA's DART struck in 2022.
Eyes that recognise an asteroid on their own
After reaching Didymos, Hera will test flying without commands from Earth. At that distance a radio round trip takes up to thirty minutes, so real-time control is impossible when orbiting a few kilometres from a 160 m moonlet. Hera's computer recognises the asteroid's outline and surface features in its camera images, works out its own position and sets its course — the same principle as a self-driving car, used operationally at an asteroid for the first time.
The technique bears directly on the next step in planetary defence. When a threatening asteroid is found a reconnaissance probe must be sent quickly, and dependence on ground control costs days at each stage of approach. Once Hera's autonomous navigation is proven, later missions could begin mapping within days of arrival. Its two companion cubesats will also test, for the first time in deep space, an inter-satellite network relaying through Hera near an asteroid.
The mission in depth
Hera is the European Space Agency's first planetary-defence spacecraft, launched on 7 October 2024 on a Falcon 9. Its destination is 780-metre asteroid Didymos and its 160-metre moon Dimorphos. In September 2022 NASA's DART slammed into Dimorphos at 22,000 km/h and shortened its orbit by 33 minutes; Hera is the follow-up survey that measures the outcome on site.
From the ground, astronomers could only time the change in orbital period. How large the crater is, whether the asteroid is a rubble pile or solid rock, and how much it weighs can only be learned up close. After a Mars flyby in March 2025, Hera arrives at the Didymos system in December 2026 and releases two CubeSats — Milani for spectroscopy and Juventas with a low-frequency radar to probe Dimorphos's interior. Those numbers are what future missions would need to size an impact against a genuinely threatening asteroid.
Track Hera in the orbit view to see it leave Earth, skim near Mars's orbit and head for the asteroid. Didymos is drawn in the orbit view too, so move the date to December 2026 and replay the arrival. Didymos poses no threat to Earth, but it is a good example of how near-Earth asteroids move.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.