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The Air Force’s Global Positioning System—known worldwide simply as GPS—affects the lives of billions of people every second.
It’s how Uber drivers find you; how your automatic teller transactions are timed; and how ships at sea fix their location. It is a global timing and location utility that the Air Force offers for free to the entire world.
GPS is also how USAF delivers precise combat power and exercises precision warfare. In fact, virtually every weapon the Air Force drops in the Middle East today is guided by GPS. Its military worth has been proved in conflicts spanning from Operation Desert Storm in 1991 to Operation Inherent Resolve.
GPS, fully operational for 22 years, traces its roots to the Cold War. The system’s genesis came with Sputnik, the Soviet Union’s first satellite, which was lofted in 1957.
Massachusetts Institute of Technology scientists, following Sputnik’s radio beeps, noticed they increased in frequency as the satellite approached and decreased as it flew away—a classic example of the Doppler effect. The MIT scientists reasoned that they could use this principle, using future satellites, to determine data such as location, speed, and elevation. By 1959, the Navy had launched its Transit system, the forerunner of GPS. This system, according to GPS World, was based on solar-powered satellites. It provided position data to ballistic missile-carrying submarines every few hours, but it was only accurate to within 25 meters, or about 82 feet.
In 1963, the Aerospace Corp. proposed a system of satellites to provide precise location information to vehicles, especially those moving really fast.
More satellite development programs emerged, including the Naval Research Laboratory’s Time and Navigation (TIMATION) program and USAF’s Project 621B.
In 1973, Pentagon leaders recognized that separate service programs aimed at a satellite navigation system would create problems and proposed a unified military approach.
Air Force Col. Bradford Parkinson, director of the NAVSTAR/GPS Joint Program Office, “assembled about a dozen members of the JPO over Labor Day weekend in 1973 and directed them to synthesize the design for a new satellite navigation system,” according to Air Force historian Rick W. Sturdevant in 2007’s Societal Impact of Spaceflight.
The result, in 1974, was the NAVSTAR system, which, according to Sturdevant was “the first satellite navigation system that enabled users to determine precisely their location in three dimensions and time within billionths of a second.”
Good as it was, military users wanted better. The drivers of “GPS development were the need to deliver weapons precisely on target and to reverse the proliferation of navigation systems in the US military,” wrote Sturdevant.
However, from the very start, “the Department of Defense (DOD) recognized the usefulness of GPS to the worldwide civilian community.”
A GPS prototype launched in 1978. The system worked when a surface or air unit interrogated the satellite for location and timing information. The more satellites that are within line-of-sight to the user, the more accurate the information.
The danger of a nonstop satellite broadcast, though, was that hostile users would be able to take advantage of it. The Air Force designed into GPS a feature called “selective availability,” which allowed US and approved allied military users a stronger and more precise GPS signal than that available to commercial entities.
In 1983, GPS became even more broadly available. The tragedy of Korean Airline Flight 007, shot down by Soviet interceptors after straying off course, provided the impetus for making the signal broadly available.After the Korean Airline incident,“President Ronald Reagan reassured the world that the coarser signal would remain continually and universally available at no cost once GPS became fully operational,” Sturdevant wrote.This took another 12 years.
Desert Storm saw the first heavy use of GPS in combat, offering unprecedented precision and changing the way wars are fought. Desert Storm also highlighted the critical importance of space contributions to airpower.“Precision navigation and timing, GPS. That was the dawn of criticality of GPS to military operations,” Maj. Gen. Paul T. “PJ” Johnson, who earned an Air Force Cross for his role in Desert Storm, told Air Force Magazine. (See “Perspectives on the Storm,” April 2016.)
Desert Storm also saw the debut of the JSTARS aircraft, which gave the coalition the capability to see, track, and target enemy ground formations in any weather, day or night. With all the attack packages airborne, “we saw the ability to dynamically … detect, … characterize, and … target” ground formations, Johnson said. During Desert Storm, the GPS constellation was limited, with 19 satellites of various generations: GPS I, GPS II, and GPS IIA. These only allowed for 19 to 20 daily hours of 3-D coverage.
Shortly after the war, the Air Force used GPS to position the airdrop of food in Somalia during 1993’s Operation Restore Hope. It was used in various peacekeeping operations across the planet, from the Haitian crisis in 1994 to the Balkan crisis in the mid-90s.
On April 27, 1995, GPS became fully operational, with a complete constellation of 24 operational Block II/IIA satellites. It provided information to both military and civilian users.
The new technology allowed the proliferation of what would eventually become the GPS our phones and computers use. Those satellites are the ones civilians still use today for these purposes.
In 1998, Vice President Al Gore said he wanted to see improvements to the GPS system, and Congress obliged with a program christened GPS III. It was approved for development in 2000.
In 2000, President Bill Clinton ordered the end of selective availability, which had offered civilian users slightly degraded accuracy relative to the military signal. Later, in 2007, President George W. Bush agreed to drop the ability to reinstate selective availability from the GPS III requirements.
In recent years, adversaries have experimented with jamming of GPS signals, persuading the Air Force to have “day without space” exercises in which participants don’t have access to GPS signals and must resort to more old-fashioned methods of navigation and target identification.
In 2008, Lockheed Martin was awarded the contract to develop the GPS III satellites. According to the company, once these satellites are launched and operating, they will provide signals three times more accurate than current GPS spacecraft, improve the anti-jamming capabilities for military users by eight times, and greatly enhance global connectivity for civilian users.
The first batch of GPS III satellites is expected to reach orbit in spring 2018.
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