Hera, her CubeSats, and their rocky target destination

Due to launch in 2024, Hera will travel to the Didymos pair of near-Earth asteroids. The 780 m-diameter mountain-sized main body is orbited by a 160 m moon, formally christened 'Dimorphos' in June 2020, which is about the same size as the Great Pyramid of Giza. Hera is the European contribution to an international double-spacecraft planetary defence test. NASA will first collide with the smaller of the two bodies, then 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. By actually venturing to Dimorphos, measuring its mass as well as its shifted orbit from up close and performing its own ‘crash scene investigation’ of the asteroid moon’s impact crater and surrounding surface in great detail, Hera will hone our understanding of the impact process at asteroid scale. Hera will carry two CubeSats – Juventas and Milani. These are Europe’s first deep-space CubeSats; they will get closer to Didymos’s companion, Dimorphos, gathering additional data on the asteroid whilst testing new intersatellite link technology. Each companion spacecraft will be small enough to fit inside a briefcase, as compared to the desk-sized Hera.