10.1.3 Meteoroids

Meteoroids are particles of natural origin. Nearly all meteoroids originate from asteroids or comets. The natural meteoroid flux represents, at any instant, a total of about 200 kg of mass within 2 000 km of the Earth surface [RD.21].

Meteoroid streams are accumulations of meteoroids with nearly identical heliocentric orbits. Relative to Earth all particles of a given meteoroid stream have nearly identical impact directions and velocities. Encounters with meteoroid streams typically last from a few hours to several days.

Meteoroids which do not form part of identified streams are called sporadics. Their flux is fairly constant over the year and they do not follow any apparent pattern with respect to incident direction or velocity. The annual integrated flux of meteoroid streams amounts to about 10% of the sporadic meteoroid flux.