Time Synchronization and the Origins of GPS

Easton, Richard

GPS is most prominent GNSS (Global Navigation Satellite System). It provides PNT (Positioning, Navigation and Time). Most accounts of its origins focus on the positioning and navigation aspects. Thus, Dr. Bradford Parkinson, first head of the GPS Joint Program Office, has stated that his motto for the system was to “Drop 5 bombs in the same hole…and don’t you forget it!” Some have even posited that the timing aspect was unforeseen. My oral presentation will illustrate how timing was an integral part of the origins and development of Timation (TIMe navigATION), the major predecessor system to GPS. It originated in an April, 1964 conversation about hydrogen masers between Roger Easton, my father, from the Naval Research Lab and Dr. Arnold Shostak from the Office of Naval Research. They agreed that it made range measurement feasible which is the method GPS uses to determine the distance between the satellite emitting a radio signal and the receiver (time difference). The development of space hardened atomic clocks was an essential part of the development of GPS. In an interview published in 1974, Easton stated that “precise orbiting clocks will prove to be a valuable tool in a variety of applications, by providing the entire planet earth with a single, accurate time system, enveloping the globe in a web of synchronized satellite signals.” This has proven to be the case and I will briefly explore current timing applications of GPS.

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