Near Earth Asteroids (NEAs) present a clear and present danger to the world's population. Once every 200 years a medium-sized NEA (diameter 40-1000 m) hits the Earth and causes serious local damage. Once every 2 million years a NEA, comparable in size with the one which terminated the era of the dinosaurs, impacts and causes fatal global damage. 85% of the NEAs with diameters larger than 1000 m are known to date; of the potentially hazardous smaller ones, down to 25 m, only 1% is chartered.