Roughly 50–100 tons of extraterrestrial material falls into the atmosphere of the Earth every year, with in falls of metersized bodies a daily event. However, there are much larger objects as well, that can pose a serious threat. Impacts of 1 km objects, which would result in civilization threatening effects, are thought to occur on roughly million-year timescales.The population of Near Earth Objects (NEOs) 50 m or larger is modeled to number in the hundreds of thousands. Although impacts by 50-100 m asteroids may devastate “only” a region (like the Tunguska Event of 1908), they also occur much more frequently, occurring on century-to-millennium timescales.

The first time in history, humanity is in a position to have the technical capability to actively deviate the orbit of an Earth threatening asteroid and prevent an impact. Various methods have been discussed where a kinetic impactor appears to be least challenging to implement.

In November 2021 NASA has launched its (Double Asteroid Redirection Test) DART Mission to hit the minor element of the Didymos double asteroid system, named Dimorphos. The impact is planned to occur on September 26th 2022 (EST) and will change the orbit of Dimorphos by momentum transfer, do that the change can be observed in the light curve from ground based observatories. This will be the first test of a kinetic impactor. DART carries, the ASI cubeSat LICIACube, to be separated from the mother spacecraft before impact and observe it from a safe distance.

In 2024 the ESA Hera mission will be launched to the Didymus system, to characterize both bodies in detail (including the determination of their exact mass, internal structure and surface properties). Also the crater, hit by the DART impact will be characterized in detail. Hera carries two CubeSats, Juventus and Milani supporting the characterization of Didymus and its environment. Hera as the European contribution to planetary defense, within a road map that should lead to offering a robust asteroid mitigation plan to future generations will not only perform the measurements necessary to fully understand the effects of the DART impact on Dimorphous but also provide unique information relevant to many current issues inasteroid science.