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The first artificial satellite was Sputnik 1, launched by the Soviet Union on 4 October 1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer and Kerim Kerimov as his assistant. This in turn triggered the Space Race between the Soviet Union and the United States. Satellites are tracked by United States Space Surveillance Network (SSN), which has been tracking every object in orbit over 10 cm in diameter since it was founded in 1957. There are approximately 560 satellites operating in Earth orbit, out of about 8,000 man-made objects in total. In its entire history, the SSN has tracked more than 26,000 space objects orbiting Earth. The majority of these have fallen into unstable orbits and incinerated during re-entry. The SSN also keeps track which piece of space junk belongs to which country.
The Global Positioning System (GPS) is a global navigation satellite system (GNSS) developed by the United States Department of Defence and managed by the United States Air Force 50th Space Wing. It is the only fully functional GNSS in the world and can be used freely by anyone, anywhere, and is often used by civilians for navigation purposes. It uses a constellation of between 24 and 32 medium Earth orbit satellites that transmit precise radio wave signals, which allow GPS receivers to determine their current location, the time, and their velocity. At any one time at least eight satellites are ‘in view’ from any position on the Earth’s surface. Skygistics makes use of the GPS satellites for vehicle monitoring and tracking.
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