In 1983 a Soviet interceptor shot down Korean Air Lines Flight 007, a Boeing 747 carrying 269 people, after navigational errors took it into prohibited airspace. President Ronald Reagan responded by directing that GPS be made freely available for civilian use once it was ready. That decision turned a Cold War military tool into something close to a public utility.
GPS began as a Defense Department project in 1973. It was not built for drivers or hikers. Congress paid for it because of the nuclear threat: submarines carrying ballistic missiles needed an accurate fix on their position before launch, and the Air Force wanted the same precision for its bombers and land-based missiles. A meeting of about twelve military officers at the Pentagon over Labor Day weekend that year pulled the Navy and Air Force efforts together. The program was named Navstar soon afterward, a word chosen only because it sounded good.
From prototypes to a full constellation
Ten Block I prototype satellites went up between 1978 and 1985. The first Block II satellite launched on February 14, 1989, and the 24th followed in 1994. In 1995 the U.S. Air Force declared the system fully operational. By then the program was no bargain. The Yale Global commentator Joan Johnson-Freese put the cost through 2016 at an estimated $22 billion, “paid for entirely by the United States.”
The program nearly died in the 1980s, when nobody could say exactly what military mission it would serve.
The satellites circle the Earth at about 20,200 kilometers, twice a day each. Every one carries an atomic clock and broadcasts its own code, along with the time, its status and its orbit. A receiver measures how long a signal took to arrive and works out its distance from the satellite. Signals from four satellites are enough to fix a position and the time. At any moment, from any point on the planet, at least four are in view.
Taking the blur off
For years civilians got a deliberately worse signal. Under a policy called Selective Availability, the military added an error to the public data that its own receivers could correct, which held civilian accuracy to around 100 meters. On May 1, 2000, President Bill Clinton signed a directive switching the degradation off. Accuracy afterward was about 5 meters. Newer receivers using the L5 band reach 30 centimeters, and surveying equipment gets down to 2 centimeters.
The uses spread quickly. Pilots and boaters came to depend on it, followed by surveyors, biologists tracking wildlife and farmers deciding where to plant. Amazonian tribes have used GPS to map their lands and monitor deforestation. Phones are required to report their location when a user dials 911.
Timing as well as position
GPS is, in Johnson-Freese’s words, “a highly accurate time-transfer system.” Credit card authorization networks, bank ATMs, broadcast video feeds, emergency dispatch computers and telecommunications networks all lean on its synchronized clocks. A small slip shows how much rides on them. In 1996 a timing error reached one satellite and was caught after only 6 seconds, yet the disruption that followed knocked more than 100 cell phone networks in the United States offline, some for over 24 hours.
Other countries noticed. Johnson-Freese wrote in 2003 that Europeans feared the U.S. military could degrade the signal in wartime, which is why they started their own Galileo program. China had launched two BeiDou satellites, and Russia was running its own aging GLONASS network. Her view was that Washington had no choice but to keep paying for upkeep and modernization if it wanted to keep its lead.
One of the Pentagon’s own modernization efforts has stumbled. The ground control upgrade known as OCX, tied to the new Block III satellites, was canceled in April 2026.
Sources
- Global Positioning System Becomes Operational | History | Research Starters | EBSCOhost
- Global Positioning System – Wikipedia
- Getting Our Bearings
