Space debris is tracked by the United States Space Surveillance Network that uses radar that can detect an object the size of a pea at 400 miles.

BBC: By BBC News Online Science Editor Dr David Whitehouse

These provide readings on location, charting, weather, sonar and radar via a proprietary Ethernet-based network.

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The United States has a network of listening posts and radar stations across Colombia, built and manned by American technicians.

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After the 1953 disasters, developers of weather radar convinced Congress to support a national network of detectors known as the WSR-57 (for 1957), a very acceptable machine for picking up tornadoes capable of causing significant damage.

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For a job seeker, this means contacting your network on a regular basis to stay on their radar.

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Mr Rasmussen wants NATO to build a missile-defence umbrella to link up America's network (scaled back from plans to have a large radar in the Czech Republic and interceptors in Poland) with smaller systems being developed by NATO and European countries like France.

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