The Asteroid Impact and Deflection Assessment (AIDA) study examines ways to potentially deflect asteroids from trajectories that could lead to them impacting Earth. The Johns Hopkins University Applied Physics Laboratory would work with NASA and ESA on the mission, which includes two independent spacecraft: an impactor (to be built by APL for NASA) and an impact monitor (to be built by ESA).

The target of this mission is the binary asteroid system Didymos. The impactor would strike the smaller secondary of Didymos, while the monitor would observe and measure any change in the relative orbit.

Learn more:
http://www.esa.int/Our_Activities/Technology/NEO/Asteroid_Impact_Deflection_Assessment_AIDA_study
http://neo.jpl.nasa.gov/
http://www.neoshield.net/en/index.htm