Navstar 1, the world’s first operational GPS satellite, launches

The U.S. Air Force launches Navstar 1, the world’s first operational GPS satellite, from Vandenberg Air Force Base in California. GPS begins as a military technology, but expands to transform industries from aviation to communications.

Global Positioning System (GPS) technology is an indispensible part of 21st century life, powering everything from rideshare apps to fitness trackers to commercial aviation. The origins of GPS technology, however, lie in the early years of the Cold War space race.

When the USSR launched its first satellite, Sputnik, into orbit in 1957, American scientists observed the Doppler effect: Sputnik's radio signal frequency increased as it moved closer, and decreased as it moved farther away. These changes in radio signal frequency allowed scientists to track Sputnik's movement across the sky. Inspired by this observation, DARPA (Defense Advanced Research Projects Agency) launched the Transit program, which provided navigation largely to warships, submarines, freighters and private maritime users. The first Transit satellite entered orbit in 1960.

Over the next few decades, the federal government funded several more satellite navigation projects (including 621B and Timation) in its quest to provide real-time, all-weather, high-accuracy navigation for all types of moving vehicles, around the clock. Developments in microprocessing, bandwidth, signal frequency and atomic clocks furthered the goal, enabling ever-greater miniaturization and accuracy.

Enter the U.S. Air Force Navstar project, which consolidated these different programs in 1974, harnessing these advances. Navstar 1, its first operational GPS satellite, launched into space four years later. GPS satellites travel through medium earth orbit, 12,550 miles high, and circle the globe once every 12 hours. They work by emitting radio signals, which are picked up by receivers on the ground. The receivers then calculate location and time, based on comparing the signals from at least four different satellites. Modern GPS technology can accurately pinpoint a location anywhere on earth, within several meters, 95 percent of the time.

GPS capabilities expanded throughout the 1980s—and beyond. The military has used it for everything from helping troops navigate trackless desert landscapes (think Desert Storm) to enabling ultra-precise missile guidance. After a Korean passenger jet strayed into Soviet air space and was shot down in September 1983, the U.S. declassifed GPS technology to help commercial airlines improve safety.

The first portable GPS device for civilians, the Magellan Nav 1000, went on sale to the public in 1989. It cost $3,000, weighed a clunky 1.5 pounds, and only offered a few hours of battery life. The U.S. GPS satellite constellation became fully operational in 1995, with 24 satellites in orbit. Cellphones began to incorporate GPS receivers as the technology improved and costs dropped; the first GPS-enabled cellphone went on sale in 1999.

In the 21st century, GPS has become ubiquitous. Today, the U.S. Space Force, created in 2019, oversees the GPS program. The Space Force aims to operate the "GPS satellite constellation as a global utility—always available to everyone, everywhere on Earth."