As part of the worlds first test of asteroid deflection, Hera will perform a detailed post-impact survey of the target asteroid, Dimorphos - the orbiting moonlet of a binary asteroid system known as Didymos. Now that NASAs DART mission has impacted the moonlet, Hera will turn the grand-scale experiment into a well-understood and repeatable planetary defence technique. Demonstrating new technologies from autonomous navigation around an asteroid to low gravity proximity operations, Hera will be humankinds first probe to rendezvous with a binary asteroid system and Europes flagship Planetary Defender.