Hera deploying CubeSats

ESA's Hera asteroid mission for planetary defence carries a pair of CubeSats in Deep Space Deployers. When Hera reaches its target Didymos asteroid system, the spacecraft will deploy the two CubeSats - radar mission Juventas and mineral prospecting Milani - one at a time so they can perform complementary observations, drawing closer to the Didymos asteroid and Dimorphos moonlet than their Hera mothership could risk. The three spacecraft will communicate together using inter-satellite links, with Hera relaying their data back to Earth. These links will also allow an estimate of the mass of the two asteroid bodies, by identifying small tugs due to gravity in the motion of Hera, Juventas and Milani by slight Doppler shifts identified in the signals.