Giving the NEO a good bump
The kinetic impactor mitigation method can be understood from the above video (credit Astrium).
The principle of the kinetic impactor mitigation method is that the NEO is deflected following an impact from an impactor spacecraft. The principle of momentum transfer is used, as the impactor crashes into the NEO at a very high velocity of up to 10km/s or more. The mass and velocity of the impactor (the momentum) are transferred to the NEO, causing a change in velocity and therefore causing it to change its course slightly.
An observer spacecraft is also required, which allows accurate measurement of the NEO's orbit before the impactor departs Earth, ensuring that it is in fact a dangerous object. Additionally, the observer can map the NEO, providing the impactor with vital information such as its exact size, shape, rotation speed and even chemical composition.
Following the impact, the observer once again accurately measures the orbit of the NEO to confirm the succecss of the impact in changing the NEO's course.
The behaviour of the impact itself, and how the momentum is transferred to the NEO, is a key research topic for the scientific side of the NEOShield project. For example, if ejecta can be kicked out from the NEO behind the impact site, this increases the efficiency of the impact by reducing the mass of the NEO after the impact.
The kinetic impactor concept has been studied to phase A level within Europe as the Don Quijote mission study. The experience gained from this study will be used during the NEOShield project in developing the detailed test mission design for the kinetic impactor mitigation method.
(Image Credit ESA)