An asteroid is a minor body orbiting in the Solar System. Usually asteroids are orbiting in the so called Main Belt, which is located between Mars and Jupiter. Half the mass of the belt is contained in the four largest asteroids Ceres (the first asteroid discovered in 1801 by Giuseppe Piazzi), Pallas, Vesta and Hygiea.
A small fraction of the asteroid/comet population is located in the Earth neighborhood, the so called Near Earth Objects (NEOs). NEOs are divided into Near Earth Comets (NECs) and Near Earth Asteroids (NEAs). There exist three main groups of NEA, depending on the geometry of their orbits: Amor, Apollo and Atens. Because of the close encounters with the Earth, they pose a risk to hit the Earth in the next future.
SpaceDyS has a strong expertise in the field of orbit determination of asteroids and in particular of NEAs. The team of SpaceDyS has more than ten years of experience in the field of impact monitoring of NEAs and it is one of the two worldwide teams which are leaders in this field.
Starting from 1 September 2011 SpaceDyS, through an official Service Level Agreement (SLA) with the European Space Agency (ESA), is responsible for managing and operating the NEODyS (link http://newton.dm.unipi.it/neodys) service. NEODyS provides information for all Near Earth Asteroids (NEAs), including impact monitoring.