Physical properties of near-Earth asteroids

More than 400 near-Earth asteroids (NEAs) have been discovered and their discovery rate is continuously increasing. The study of the physical properties of these objects is secressary in order to understand their history and relations with comets and meteors, for the analysis and solution of new applied topics, such as the asteroid hazard problem, and the possibility of using NEAs as foture sources of raw materials in near-Earth space. The present review article collects and summaries the most important new data on the physical properties of Earth-approaching asteroids, obtained by photometric, polarimetric, spectroscopic, radar and other techniques. The analysis of all the available data gives clear indications that asteroid main-belt is the main source of NEAs.