The Global Position System (GPS) has turned 25 years old. Operated by the US Space Force, the constellation of navigational satellites went fully operational on April 27, 1995, though US Space Command only made the formal announcement three months later in July of that year.
GPS and other global navigation satellite systems (GNSSs) have become so much a part of our lives that it's easy to forget that they only started to be widely used less than a generation ago.
The concept itself dates back to 1957 when two American physicists at Johns Hopkins University's Applied Physics Laboratory (APL) worked out that they could calculate the orbital position of the Soviet Union's Sputnik satellite by the Doppler effect on its radio signal. Shortly after, Frank McClure, the deputy director of the APL, realized that the calculations would work in reverse. If you knew where the satellite was, you could figure out the exact location of the earthbound receiver.
A number of experimental systems were subsequently designed for military applications, and in the 1970s the US Defense Department began work on what is now GPS. After the shooting down of a Korean airliner by the USSR in 1983 due to a navigational error that sent it into Soviet airspace, President Ronald Reagan ordered that the system should be made available to civilians.
Though the first GPS satellite was launched in 1978, it wasn't until 1995 that the first constellation was in place and declared fully operational. Since then, it has become an essential tool around the world for military purposes, general navigation, motorway traffic monitoring, financial transactions, agriculture, and even warehouse management.
According to the Space Force, there are currently 31 GPS satellites in service, with a new GPS III version boasting longer service life, as well as greater safety, signal integrity, and accuracy, slated to replace them. The first of these GPS III satellites, Vespucci, was launched in 2018, and the second, Magellan, went into service on March 27, 2020.
"The 25th Anniversary is a huge, momentous occasion for us. We take great pride in providing this global utility to the approximately six billion users worldwide," says Lieutenant Colonel Stephen Toth, 2nd SOPS commander. "Celebrating this anniversary gives us a moment to recognize how far we’ve come, but also to get pumped about what lies ahead for our program and our role in executing that."
Source: US Space Force