I was 13 and followed it closely. My Dad started working on the space program in 1952. He worked on Project Viking (not the later NASA program), designed the Vanguard 1 and then invented GPS. Here’s the website for my book. www.gpsdeclassified.com
GPS was a further evolution of a sat nav system called TRANSIT.
“The Transit system, also known as NAVSAT or NNSS (for Navy Navigation Satellite System), was the first satellite navigation system to be used operationally. ... Transit provided continuous navigation satellite service from 1964, initially for Polaris submarines and later for civilian use as well.”
THE TRANSIT Navigation Satellite System
By Thomas A.Stansell
https://www.ion.org/museum/files/TransitBooklet.pdf
Full disclosure: I did work at TI on the HDUE and MANPACK GPS units in the late 70’s (1977 - 78) time frame. At that time tests were being run on a ground range at Yuma proving grounds and only 3 NAVSAT ‘birds’ had been launched at the time.
GPS was a further evolution of a sat nav system called TRANSIT.
“The Transit system, also known as NAVSAT or NNSS (for Navy Navigation Satellite System), was the first satellite navigation system to be used operationally. ... Transit provided continuous navigation satellite service from 1964, initially for Polaris submarines and later for civilian use as well.”
THE TRANSIT Navigation Satellite System
By Thomas A.Stansell
https://www.ion.org/museum/files/TransitBooklet.pdf
Full disclosure: I did work at TI on the HDUE and MANPACK GPS units in the late 70’s (1977 - 78) time frame. At that time tests were being run on a ground range at Yuma proving grounds and only 3 NAVSAT ‘birds’ had been launched at the time.