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Detections Meteoroids are what you call meteors when they are in the earth's atmosphere, when they land they are called meteorites. When meteoroids break through the atmosphere they reach velocities of between 15 and 20 kilometres per second. A meteoroid 10 metres across the world would weigh about 1000 tonnes. The energy of impact of this kind of meteoroid is equal to a bomb of 20,000 tonnes of TNT-this is greater than the atom bomb that was dropped on Hiroshima in 1945.

Comets are usually really hard to detect, due to their small size.The USDD(United States Department of Defence) uses satellites and they have managed to detect 136 explosions in the upper atmosphere, this happened in the period of 1975 to 1992. These explosions are called airbursts, airburst detectors are kept on board of the Sentinel satellites, these satellites operate at 38,000km altitude in the geosynchronous orbit. The satellites' job is to detect heat from rocket engines and ballistic missilies. They do this by detecting radiation. The infrared sensors check the earth's disc every 10 seconds and these detectors are connected to a 3.6m focal lenght optical Scmict telescope. Destroyed in Seconds (Page 4)