On the attainability of the Near Earth Asteroids.

The accessibility of the Near Earth Asteroid (NEAs) population can be investigated by means of some basic celestial mechanics and astrodynamics.The classical results on teh attainability of celestial bodies obtained by Walter Hohmann at the beginning of the XX.th century are generalised introducing an H-plot. This allows to develop an efficient targeting strategy for space missions aimed to the NEAs. Applications to the ESA phase-A mission studies ISHTAR and SIMONE and to a NEA sample return mission are presented.