This one-quarter scale model represents the second generation, or "Block II" of satellites that make up the Navstar Global Positioning System, known as GPS. GPS is a US Defense-Department system designed to provide world wide, three-dimensional positioning information, 24 hours a day. Civil customers may also access the system at no charge.
The first generation, Block I, satellites were used as research vehicles to test the feasibility of the concept. A constellation of 24 Block II satellites make up the space segment of a fully operational system. The satellites were built by Rockwell International, which also built this scale model for exhibit purposes. Launches of Block II satellites began in 1989, and the Defense Department declared GPS fully operational in 1995. New generation systems are being developed and launched as GPS continues to evolve rapidly.
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