The European Space Agency (ESA) is studying the preliminary design of two space missions for ~2020, named AIDA (formerly Don Quijote), and if flown, they would be the first intentional asteroid deflection mission. ESA's Advanced Concepts Team has also demonstrated theoretically that a deflection of 99942 Apophis could be achieved by sending a simple spacecraft weighing less than one ton to impact against the asteroid. During a trade-off study one of the leading researchers argued that a strategy called 'kinetic impactor deflection' was more efficient than others.