ESA's Hera spacecraft successfully completed its largest deep space maneuver on March 17, burning 123 kg of hydrazine to achieve a 367 m/s delta v—the largest system test since its October 2024 launch on a SpaceX Falcon 9.
Four years is a long time to wait to find out if you hit the right spot. ESA Hera spacecraft completed its largest deep-space maneuver to date on March 17, burning 123 kilograms of hydrazine across three main engine firings and a correction burn over four weeks, shifting velocity by 367 meters per second, according to Space.com. The spacecraft is on track to arrive at Didymos in November, as detailed by ESA. Then we will finally know what DART actually did.
For context: NASA DART mission slammed a 570-kilogram impactor into Dimorphos, the moonlet of the 780-meter asteroid Didymos, on September 26, 2022. It was the first full-scale kinetic deflection test against a real asteroid — the kind of scenario that plays on loop in planetary defense workshops. Hera job is to go look.
"This is the Hera mission largest manoeuvre in terms of fuel consumption, and we used it to test all of the systems that we will need during the braking and rendezvous manoeuvres later this year," said Francesco Castellini of ESA Flight Dynamics division, in an agency press release. The 367 m/s delta-v is not trivial for a spacecraft with a launch mass of 1,128 kilograms and a dry mass of 350 kilograms, manufactured by OHB SE. It was, in effect, a full dress rehearsal for the braking sequence that begins in October, as noted by ESA.
DART was a proof of concept for kinetic impact as a planetary defense tool — the idea that you can nudge an asteroid off course by hitting it. The concept was validated at the mission level: Dimorphos orbit changed, and the Didymos-Dimorphos binary system solar orbit shifted by 0.15 seconds as a result.
Hera carries 12 scientific payloads, including the Milani and Juventus CubeSats, and will spend at least six months in the Didymos system before descending to image the DART crater from approximately one kilometer — close enough to see the structure in detail, but not so close that a debris ejection mishap ends the mission, according to Wikipedia). The spacecraft launched on October 7, 2024 on a SpaceX Falcon 9 from Cape Canaveral.
The October braking burns are the critical sequence. Until then, Hera is a spacecraft on a very long approach. The planetary defense community has been waiting since 2022 for this data. In a few months, they will finally have it.