Investigating near-Earth asteroids

Recent publicity, including the Hollywood blockbusters Deep Impact and Arma geddon, has raised the level of public awareness that comets and asteroids frequently fly by the Earth at distances close to zero in astronomical term s. In fact the Earth moves among a swarm of such objects, mainly asteroids, and more are being discovered almost daily. Knowledge of the size distribu tion, surface properties and compositions of near-Earth asteroids is essent ial for investigations of their origins, their relation to meteorites and c omets, the role they have played in the evolution and development of the te rrestrial planets and life on Earth, and the current threat they pose to ci vilization as potential impactors on the Earth. Techniques applied to the s tudy of near-Earth asteroids and some recent results are described.