Near-Earth objects (NEOs) are asterois, comets and large meteoroids whose orbits bring them close (perihelion distance < 1.3 AU) to Earth's orbit, and which may therefore pose a collision danger. Due to their size and proximity, NEOs are also more easily accessible for spacecraft from Earth and are important for future scientific investigation and commercial development. Some near-Earth asteroids can be reached with a much smaller change in velocity (ΔV) than the Moon.