Hera is scheduled to reach a binary asteroid pair called Didymos and Dimorphos in late 2026 for a minimum-six-month study of the asteroid system.
Hera is ESA’s second attempt at sending a planetary defense mission to an asteroid. It draws heavily on an earlier program called the Asteroid Impact Mission that was canceled in 2016 after failing to secure funding.
Hera will follow NASA’s Double Asteroid Redirection Test, or DART, which is scheduled to launch in July 2021 on a SpaceX Falcon 9 rocket. DART will crash into the smaller of the two asteroids, Dimorphos, in September 2022, to test a technique for deflecting an asteroid on a collision course with Earth.
While DART will carry a cubesat co-passenger that will be released prior to the collision to conduct an initial post-collision fly-by, Hera will provide a more thorough assessment of the impact and determine how much the asteroids’ orbits changed.
Hera, according to ESA, aims to convert the results of DART from a “grand-scale experiment into a well-understood and repeatable asteroid deflection technique.”
Some 15% of asteroids are in binary orbits, according to the agency. In the binary system DART and Hera will visit, Dimorphos measures 160 meters in diameter and is about the size of the Great Pyramid of Giza, while its larger companion measures 780 meters across and is the size of a mountain. Material ejected from DART’s impact is expected to land on both asteroids.
OHB’s contract covers Hera’s design, integration and testing. The 1,050-kilogram spacecraft will carry two cubesats, one from GomSpace and one from Tyvak International, for which ESA is negotiating final contracts.
GomSpace plans to build the Juventas cubesat in Luxembourg, which will scan the interior of Dimorphos using a low-frequency radar.
The Italian-led Milano cubesat from Tyvak International will conduct dust and mineral prospecting studies.
Hera will act as a carrier for the two cubesats and as a relay station for communications with Earth for the spacecraft. ESA will control the Hera mission from the European Space Operations Centre in Darmstadt, Germany.