From minitrack to NAVSTAR: The early development of the Global Positioning System, 1955–1975

The paper outlines the early days of satellite navigation, focusing on the work of the Naval Research Laboratory (NRL) on systems that contributed to the later Global Positioning System (GPS). NRL's innovations included the Minitrack system for space surveillance, the development of high-precision timing systems for use in space, the Timation navigation satellite program, and the first two Navigation Technology Satellites (NTS-1 and NTS-2). NAVSTAR-GPS emerged as a joint Department of Defense (DoD) program in 1973, by which time much of the GPS concept had been developed and a number of GPS technologies had been tested