1 and 10 cm in diameter is 500,000. The amount of particles bigger than 1 mm exceeds 100 million. The particles travel at speeds up to , so even a small particle impact can severely damage a spacecraft. See also Comparison of orbital launch systems Geostationary orbit (GEO) Heavy lift launch vehicle High Earth orbit (HEO) Highly elliptical orbit (HEO) List of orbits Medium Earth orbit (MEO) Medium-lift launch vehicle Specific orbital energy examples Suborbital spaceflight Ukrainian Optical Facilities for Near-Earth Space Surveillance Network Van Allen radiation belt Notes References Earth orbits Articles containing video clips