Global Positioning System
summary
Built and flown the original onboard satellite software for GPS, starting proof-of-concept launches in 1977 and full implementation in 1980; satellites orbit nearly circularly twice a day with an 11h58m period and sit around ~11,000 miles (vs geosynchronous ~22–23k). Navigation fixes use four or more satellites, a five-part navigation message with 11 orbit parameters, and atomic clocks corrected for relativistic effects, yielding user accuracy down to side-of-highway and costing continuous receiver CPU and battery.
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