The Asteroid Impact & Deflection Assessment (AIDA) mission is a proposed space probe under development by the European Space Agency, which would study the effects of crashing a spacecraft into an asteroid. The mission is intended to test whether a spacecraft could successfully deflect an asteroid on a collision course with Earth. The project was formed by joining two separate studies, called 'DART' (an asteroid impact probe) and 'AIM' (an asteroid orbiter).
The target is 65803 Didymos, a binary system in which one asteroid is orbited by a smaller one. In the AIDA mission, the DART spacecraft would impact the smaller of the asteroids and AIM would study the effect on its orbit around the larger asteroid, as well as studying the geology of the two asteroids. Both spacecraft would be able to operate independently, so that if one failed, the other could still achieve science goals.
The mission is still in the planning stages and no launch date has been proposed.