Meteoroid orbits

Numerically-speaking, the orbits of meteoroids dominate our knowledge of the orbital parameters of Earth-crossing small bodies: the meteoroid orbit database outstrips the numbers of observed Earth-crossing asteroids and comets by over two orders of magnitude. Whilst it is often imagined that small meteoroids are predominantly derived from comets through stream formation, and thus must have comet-like orbits, in fact the majority of observed meteoroid orbits are more similar to those of Apollo and Aten asteroids, with small, low-inclination orbits. In all about 69 000 meteoroid orbits are available from the IAU Meteor Data Center in Lund, Sweden, having been measured in various optical and radar observation programs based in the U.S.A., Canada, the former Soviet Union, Somalia, the Czech Republic, Japan, and Australia. Depending upon the detection method used, the original meteoroids producing the observed meteoric phenomena range in size from 100 m to 10 cm. Here the raw orbital, radiant and speed distributions are presented for the major surveys, a common format being used so that they may be intercompared such that general conclusions may be drawn, and the differences between the survey results identified. These data, collected over the past several decades, provide an important source of information on the origin and evolution of the small bodies in the solar system.