Hera is the European contribution to an ESA-NASA double-spacecraft AIDA mission, which is intended to test whether a kinetic deflection technique can be used to shift the orbit of an asteroid. The target of the mission is a double asteroid system, called Didymos, which will come a comparatively close 11 million km to Earth in 2022. The 800 m-diameter main body is orbited by a 170 m-diameter moon, informally called ‘Didymoon’.
In 2022, NASA's DART spacecraft will first perform a kinetic impact on the smaller of the two bodies, and, later, Hera will follow-up with a detailed post-impact survey that will turn this grand-scale experiment into a well-understood and repeatable planetary defence technique.
Hera will also gather crucial scientific data on asteroids as a whole by carefully studying the exterior and interior properties of both bodies in the system. The spacecraft will also host two 6-unit cubesats that will be deployed near Didymos to perform, for the first time ever, multi-point measurements in a “mother-daughter” configuration. A novel intersatellite link will be used to establish a flexible communications network supporting the close-proximity operations in very low-gravity conditions, a crucial step for future exploration activities around small bodies.
As of 2018, Hera, a further optimisation of ESA’s earlier proposed Asteroid Impact Mission, was in Phase B1 of mission development in preparation of the Agency’s Council of Ministers at European Level in late 2019.