NEOs can be defined as asteroids and comets
that come near the Earth and therefore, with orbits characterized
by a perihelion distance q less than 1.3 AU (click here to know more about
the parameters that define an orbit).
These objects can be divided in NECs (near earth comets) which normally include only short period comets and NEAs , near earth asteroids. A further classification of the NEAs is established dividing them into three groups (Amor, Apollo and Atens) according to their perihelion and aphelion distances and their semi major axes.
Near Earth Comets
|NEA near earth asteroids||Atens||q<1.3 AU
a<1.0 AU Q>1 AU