Impact cut asteroid orbit by 33 minutes; ESA's Hera due to inspect in November

In 2022 a spacecraft hit Dimorphos, a moonlet about 150 metres across, and shortened the time it takes to orbit Didymos by about 33 minutes. The European Space Agency's (ESA) Hera probe is now heading for this double-asteroid system to measure at close range what that impact left behind.

Under ESA's plan, Hera is due to rendezvous with the Didymos asteroids in November 2026. As of 8 November 2026, ESA's Hera mission page still lists the rendezvous as a planned date in November 2026 and does not say the probe has arrived.

What the 2022 impact has already established

On 26 September 2022, NASA's Double Asteroid Redirection Test (DART) spacecraft struck Dimorphos. Dimorphos is about 150 metres across and orbits Didymos, which is about 800 metres across.

According to a University of Helsinki press release, Dimorphos's orbital period was shortened by about 33 minutes after the impact. The figure was found by two independent methods, and the research was published in Nature in March 2023.

The impact threw up a large debris cloud, which the Hubble Space Telescope also observed. The ejected material gave extra thrust, so the momentum transferred to the asteroid was greater than that carried by the spacecraft alone.

How far Hera's journey has got

Hera launched on 7 October 2024 and is controlled from ESA's European Space Operations Centre (ESOC) in Germany. In March 2025 it flew past Mars, using the planet's gravity to bend its trajectory towards Didymos, and the team also tested its instruments at close range.

On 7 October 2025, ESA said the propulsion system had proved reliable, allowing a more aggressive braking plan, and that Hera was on track to arrive in November 2026, one month earlier than originally planned.

On 17 March 2026, ESA announced that Hera had completed its second deep-space manoeuvre: three main engine burns plus one smaller correction over about four weeks, with a delta-v (the change in speed the engine gives the probe) of 367 metres per second, using 123 kg of hydrazine fuel. Data from ESA's Estrack ground tracking network confirmed the manoeuvre's success, and telemetry showed all subsystems performing as expected.

The same article said a series of precisely timed burns would begin in October to move Hera from interplanetary cruise to asteroid rendezvous, followed by an approach of about three weeks that would test its guidance, navigation and control.

ESA's mission page shows an update dated 12 October saying Hera was preparing for sustained braking manoeuvres, and another dated 27 October saying Hera had resolved its two target asteroids separately for the first time, with the Didymos system about 197 million km from Earth. A repost on the space news site Space Launch Schedule also confirms the publication date and the distance.

What Hera will measure on arrival

ESA says Hera will study the aftermath of the DART impact, helping to show how an asteroid's trajectory can be changed reliably.

Hera also carries two suitcase-sized CubeSats, Milani and Juventas, each to carry out its own close-up investigations.

Confirmed and unconfirmed at a glance

The following is based on public information as of 8 November 2026.

Confirmed

• DART hit Dimorphos on 26 September 2022, shortening its orbital period by about 33 minutes, as found by two independent methods.
• The ejected material made the momentum transfer greater than that carried by the spacecraft alone.
• Hera launched on 7 October 2024 and flew past Mars in March 2025.
• ESA announced on 17 March 2026 that the second deep-space manoeuvre was complete, with ground tracking data confirming its success.
• ESA announced on 27 October 2026 that Hera had resolved the two asteroids separately for the first time.

Unconfirmed or not announced

• Exact arrival date: ESA lists only November 2026, and as of 8 November has announced no arrival.
• Whether all the braking burns that began in October have been completed: ESA's mission page shows no confirmation.
• Dimorphos's internal structure: the University of Helsinki release describes it as a rubble pile, a loose conglomerate of boulders and pebbles, but the ESA material shows no on-site measurement by Hera.

Whether Hera has arrived is a matter for ESA's announcements.

Prices and details correct as of November 2026

Compiled by the F50 Editorial Team from public sources, for general reference only and not professional advice. Details are correct as of the publication date and may change.