NASA issued the next in its series of grand challenges, this time the ultimate killer (or saver) application for the idea of proactive systems - the challenge consists of the sense part -- sensing all moving objects in space, forecast part --- forecast the asteroid trajectories, determine if the trajectory might jeopardize earth, and if yes -- use robotic vehicles to alter the trajectory. An ambitious project, which may be vital for the survival of earth. This includes breakthroughs in sensors and actuators and also lightweight robots that can explore asteroids. Note that there are 8800 known near earth asteroids. See also the Wikipedia value about "Asteroid impact avoidance". The relevant research community will have a lot of resources to work on these issues.