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ESA’s Hera spacecraft is in the final weeks of its approach to the Didymos asteroid system, and its scientists have one clear job: finish the experiment that NASA’s DART mission started. In our new video interview, Michael Küppers, Project Scientist of the Hera mission at ESA’s European Space Astronomy Centre (ESAC), walks us through what Hera has to measure and why it matters for protecting Earth.
This article gives you the context around that conversation: what DART achieved, what it left unanswered, how Hera will fill the gaps, and where the spacecraft stands as of 23 October 2026.
Watch the full interview with Michael Küppers:
https://www.youtube.com/@spaceinfoclub/videos
What DART changed, and what it left open
DART shortened the orbit of the asteroid moon Dimorphos by 32 minutes. On 26 September 2022 the NASA spacecraft hit Dimorphos at roughly 6.1 km/s. Before the impact the moon circled its parent asteroid Didymos in 11 hours 55 minutes; afterwards it took 11 hours 23 minutes, with an early uncertainty of about 2 minutes (ESA).
NASA had set 73 seconds as the minimum change for success, so the result exceeded that benchmark by more than 25 times. Dimorphos, about 151 m across, thus became the first Solar System object whose orbit was measurably shifted by human action (ESA, Hera mission overview).
Part of that push came from the debris thrown out by the impact, which acted like a jet of gas from a balloon. To turn the result into something engineers can plan around, scientists need to know how efficiently DART’s momentum was transferred. That calculation is still missing three inputs:
- the mass of Dimorphos
- what Dimorphos is made of and how it is put together
- the shape of the crater DART left behind
Supplying them is Hera’s job (ESA, Hera mission overview).
What Hera will do at Didymos
Hera will perform the first close-up scientific survey of a binary asteroid, concentrating on Dimorphos, the smallest asteroid humankind has visited. ESA plans high-resolution visual, laser and radio science mapping to build detailed maps of its surface and interior. Hera will also measure the moon’s mass and shifted orbit, then study the DART crater in detail (ESA, Hera mission overview).
The main instruments sit on the spacecraft’s top panel, the Asteroid Deck:
| Instrument | What it does | Supplied by |
|---|---|---|
| Asteroid Framing Camera | Monochrome visible-light imaging, with two redundant cameras | Jenoptik (Germany) |
| Thermal Infrared Imager (TIRI) | Maps surface temperature; how fast it changes reveals roughness, particle size and porosity | JAXA |
| HyperScout H | Images in 25 visible and near-infrared bands to prospect the mineral make-up | cosine Remote Sensing (Netherlands) |
| Laser Rangefinder | Measures distance to the surface to better than 1 m, from 10 m to 20 km | Jenoptik (Germany) |
Hera also carries two CubeSats, Milani and Juventas. They are the first ESA CubeSats to operate beyond Earth orbit, and they will fly closer to the asteroids than Hera itself, taking more risk. Milani will prospect the mineral make-up of Dimorphos, while Juventas will perform the first radar sounding inside an asteroid. Both are planned to end their missions by touching down on Dimorphos, and Hera is planned to finish with a descent onto Didymos (ESA, Hera mission overview).
Where Hera is now
Hera has finished its two-year cruise and is now braking to match the speed of the Didymos system. ESA describes the braking as the spacecraft’s most challenging activity since launch (ESA, 7 October 2026). Rendezvous is planned for November 2026, a month earlier than originally scheduled, thanks to a later and harder braking plan (ESA, October 2025).
The approach is delicate because Didymos and Dimorphos are small and dark. Hera has to search for them actively and keep them centred in its field of view as it navigates (ESA, March 2026).
| Date | Milestone |
|---|---|
| 7 October 2024 | Launch from Cape Canaveral Space Force Station, Florida |
| Spring 2025 | Mars flyby to change course and gain speed |
| February to March 2026 | Second deep-space manoeuvre: 123 kg of hydrazine burned, velocity changed by 367 m/s |
| 7 October 2026 | Hera’s camera takes its first glimpse of Didymos |
| 15 October 2026 | Scheduled braking manoeuvre BRM-1: three thrusters firing together for 93 minutes |
| 22 October 2026 | Scheduled braking manoeuvre BRM-2: a shorter burn of about 31 minutes |
| Late October 2026 | Three smaller transition manoeuvres to bring relative velocity near zero |
| November 2026 | Planned rendezvous with the Didymos system |
| November to December 2026 | Early characterisation phase, observing from about 25 to 30 km away (ESA) |
ESA publishes the latest status on its Hera mission page.
The interview: Michael Küppers, Hera Project Scientist
Michael Küppers is ESA’s Project Scientist for Hera, working at the European Space Astronomy Centre (ESAC). His name is spelled Kueppers on some ESA pages. The project scientist works with the mission’s Principal Investigator, Patrick Michel of the CNRS Observatoire de la Côte d’Azur, and together they head the Hera Science Management Board. That board oversees the working groups and the leads of the individual instruments. The science team spans ten European countries, plus Japan and the United States (ESA, Hera Science Team).
In our conversation we cover:
- what Hera has to answer first after DART
- why the mass and internal structure of Dimorphos matter for asteroid deflection
- what the DART crater can reveal
- how solar heating and radiation influence an asteroid’s spin and orbit
- how Hera’s findings feed into future planetary defence work, including ESA’s Ramses mission
Watch the interview: full video on the SpaceInfo Club YouTube channel
Why it matters for planetary defence
Hera’s value is repeatability: it aims to turn one successful test into a technique that could be used on a real threat. The chance of a major asteroid impact is low, but the consequences could be severe. ESA points to the 1908 Tunguska event, probably caused by an object 30 to 40 m across, and the 2013 Chelyabinsk airburst, which may have come from an asteroid just 20 m wide (ESA, Hera mission overview).
The next step is already planned. ESA’s Ramses mission will rendezvous with the asteroid Apophis, which is roughly 375 m across and will pass within 32,000 km of Earth’s surface on 13 April 2029. Astronomers have ruled out an impact. Ramses is scheduled to launch in April 2028 and arrive in February 2029, and it is a collaboration between ESA and JAXA (ESA, Ramses).
The two missions complement each other. DART and Hera show that an asteroid can in principle be redirected. Ramses is meant to show that a reconnaissance spacecraft can reach an incoming asteroid within a few years, and ESA says it reuses much of the technology and expertise developed for Hera (ESA, Ramses).
Frequently asked questions
What is the Hera mission?
Hera is ESA’s first planetary defence mission. Launched on 7 October 2024, it is travelling to the Didymos binary asteroid system to survey Dimorphos, the moon that NASA’s DART spacecraft hit in 2022.
When does Hera arrive at Didymos?
ESA’s mission page lists the rendezvous for November 2026. Before that, the spacecraft performs braking and transition manoeuvres through October.
What did DART change?
DART shortened the orbit of Dimorphos around Didymos by 32 minutes, from 11 hours 55 minutes to 11 hours 23 minutes.
What will Hera measure that DART could not?
Hera will measure the mass and make-up of Dimorphos and the shape of the impact crater. Together these determine how efficiently DART transferred momentum to the moon.
What are Milani and Juventas?
They are Hera’s two CubeSats and the first ESA CubeSats to operate beyond Earth orbit. Milani will prospect the mineral make-up of Dimorphos, while Juventas will perform the first radar sounding inside an asteroid.
Will Apophis hit Earth?
No. Astronomers have ruled out an impact. Apophis will pass within 32,000 km of Earth’s surface on 13 April 2029.
Who is Michael Küppers?
He is ESA’s Project Scientist for Hera, based at ESAC. Together with the mission’s Principal Investigator, he heads the Hera Science Management Board.
Sources
- ESA: Hera mission page
- ESA: Hera mission overview
- ESA: Hera’s Asteroid Deck and instruments
- ESA: Hera Science Team
- ESA: Braking news! Time for ESA’s Hera asteroid mission to go slow
- ESA: Hera on course for asteroid rendezvous
- ESA: ESA’s Hera targets early arrival at Didymos asteroids
- ESA: First kinetic impact test succeeds in shifting asteroid orbit
- ESA: Ramses: ESA’s mission to asteroid Apophis
More space and aerospace coverage is collected in our full article archive.
All mission data is sourced from ESA. The status of the mission is as of 23 October 2026; timings are subject to change, so refer to ESA’s Hera page for the latest updates.
