Hera's arrival: Europe's planetary-defense detective reaches Didymos
From a Falcon 9 launch and a Mars flyby to October 2026 braking burns — what Hera and its two CubeSats will do now.
Published 2026-10-23
DART showed that a spacecraft can shift an asteroid's orbit. ESA's Hera is designed to turn that one-off experiment into a well-understood, repeatable technique by surveying Dimorphos in detail after the impact.[4]
Launch and Mars flyby
Hera launched on October 7, 2024, on a SpaceX Falcon 9 from Cape Canaveral.[4][7] On March 12, 2025, it swung past Mars at about 5,000 km for a gravity assist and observed the small Martian moon Deimos along the way.[7]
October 2026: final approach
In October 2025, ESA announced Hera was on track to arrive a month earlier than first planned.[7] Exactly two years after launch, on October 7, 2026, it imaged Didymos for the first time — a single pixel from 236,500 km away. It fired its first braking manoeuvre on October 15, 2026, and a second on October 22, 2026, at about 2,300 km from Didymos.[7] The rendezvous is scheduled for November 2026.[4]
What Hera will do
- Survey the crater and shape. Hera's cameras will map both asteroids and the crater DART left behind.[7]
- Weigh Dimorphos. Measuring its mass is key to calculating exactly how effective the impact was.[7]
- Deploy two CubeSats. Juventas will probe Dimorphos's interior and gravity, and Milani will image the asteroids and study dust.[7]
ESA lists Hera as carrying 12 payloads, including the two CubeSats, and describes it as humanity's first probe to rendezvous with a binary asteroid system.[4] It is expected to study the system for about six months.[7]
Why it matters
DART's measured result depends on Dimorphos's mass and internal structure, which can't be measured well from Earth. Hera's data will let scientists apply the lesson to other asteroids — the heart of planetary defense.[4][6]
Numbered citations link to the sources list on the Didymos overview page.