The government's Global Positioning System program has been wildly successful, and more technology enhancements are on the way. However, the success of GPS may help explain why it's in peril.

While most people may know the Global Positioning System (GPS) as a means to finding their way while traveling, its impact goes far beyond the search for the best route for your commute. Signals from GPS satellites have transformed industries you already know about, including aviation, shipping, and ocean navigation. But those signals also have transformed industries you think about less often, such as agriculture, manufacturing, and even spaceflight.

The only thing more remarkable than GPS technology is its ubiquity. There’s a GPS receiver in nearly every cell phone in the world. There are GPS receivers in environmental sensors, in pipeline controllers, and of course in cars—even in many vehicles without navigation systems. The technology improves everything from farming to shark tracking to geocaching games.

Even cooler, GPS is set to get better.

How GPS works

GPS is so ubiquitous because of the simplicity of the concept. Each GPS satellite is essentially an extremely accurate clock that broadcasts the exact time at its location. The satellites also provide the location in orbit of all other GPS satellites. Once the GPS receiver knows the location of the satellite and the time, it can then see the exact distance to the satellite. When a receiver can compare the time from at least three satellites, it can know its own location on the earth’s surface.

The more satellites, the better the accuracy. With at least four satellites to draw upon, the GPS receiver can know its own altitude above the surface of the earth. To do so, it compares the times at which the time signal left each satellite; it can use those times to determine distance because the signals travel at the speed of light.

GPS timing allows the measurement of the speed of light to determine the latency of microwave signals during a test at the University of Hawaii. Image courtesy of Wayne Rash.

Current GPS technology can provide locations that are accurate to within about one meter. The precision is limited by variations in the speed of light due to changes in air density and because of interference by the earth’s ionosphere.

Those limitations are set to change, as a new round of GPS satellites, known as GPS III, begin to take their place in the GPS constellation.

Up, up, and away

The new GPS satellites have just begun to take their places. The first launch occurred as a payload on board a SpaceX Falcon 9 rocket on Dec. 23, 2018. The GPS III satellites will continue to be launched through about 2025.

The new GPS satellites can provide better positioning accuracy because of a new set of atomic clocks carried aboard each satellite. Because they have more transmitter power, GPS reception can be more reliable, even indoors and in dense urban areas. In addition, the signals can be more resistant to jamming. Other improvements include the first adaptations to improve the use of GPS in space navigation.

Yes. Space navigation.

Space case

While GPS was developed for terrestrial navigation, it turns out those same GPS signals can be used by spacecraft as far away as the moon and while in early transit to and from Mars.

While GPS signals are beamed directly at the earth, some of those radio signals spill over and escape into space. “We live off the leftovers,” says Frank Bauer, retired division head for space navigation at NASA. “We live off the spill over of the main beam and any side lobes.” Bauer still works with NASA as a consultant.

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Bauer’s team figured out how to use those “leftovers.” “We developed a special GPS receiver,” Bauer says, explaining that a standard GPS receiver won’t work in space. NASA currently uses GPS in space to control the docking of payloads for the International Space Station, for accurate positioning of the GOES weather satellites, as well as for a number of scientific satellites.

“NASA has already demonstrated that you can use GPS halfway to the moon,” Bauer says, adding that NASA is already working on receivers and antennas for use on and around the moon. “We’re working with the Johnson Space Center folks on opportunities on the Lunar Gateway,” he adds.

NASA is also working on international compatibility for positioning satellites. Through a United Nations committee, a common set of definitions for signals has been developed for positioning satellites from the U.S., Europe, Russia, China, Japan, and India. “We’re trying to get them all interoperable for use in space,” Bauer says.

Once interoperability is accomplished, receivers effectively will have access to all of the positioning satellites, which in turn will lead to greater accuracy. The result: Where one-meter accuracy was once possible, now it will be less than that. You could know your position within inches.

In addition, new signals on the GPS III satellites will provide more accuracy by making more positioning signals and signals with higher accuracy available to users.

GPS at risk

But before that can happen, a new ground control system called OCX needs to become fully operational, and that won’t happen until sometime in 2021.

Delays in the operational control system are just one of the many risks to the promise of GPS. There’s also the possibility that GPS can be taken out of service by cyberattackers, foreign governments, or even bureaucratic infighting.

"Acquisitions tend to be fairly troubled,” says Cristina Chaplain, director of contracting and national security acquisition for the U.S. Government Accountability Office. Chaplain oversees the GPS program for the U.S. Congress. There are management issues and manufacturing delays in making the satellites, she says. In addition, the U.S. Air Force needs to be able to maintain a minimum number of satellites and depend on the satellites outliving design life when it plans acquisitions.

But there’s a second area of concern as well. “The second track is that space is becoming a dangerous place,” Chaplain says. Other countries could attempt to damage or destroy GPS satellites; both India and China have demonstrated the ability to take out orbiting satellites, she notes.

However, an even more immediate threat is jamming of GPS signals, which doesn’t require an attack by another government, Chaplain says. In fact, flights at the Newark airport were recently interrupted when truckers, trying to confuse the GPS receivers used to track their rigs, used commercially available GPS jammers on the New Jersey Turnpike.

Chaplain says that the anti-jamming features of the GPS III satellites will be available to the military once the OCX ground control system is operational. However, she expects it to take another decade before that will be a reality because corresponding receivers still need to be installed on hundreds of weapons platforms. “There are other things you can deploy in space that mess with data or the satellites,” Chaplain says. “It’s a serious enough threat for DOD to be working on it." (Note: The anti-jamming feature is for military purposes.)

“Threats to GPS and other military satellites tie to the calls for a space force,” Chaplain adds. “DOD believes it is not effectively positioned to counter attacks to its space assets. This is partly due to the fragmented nature of space leadership. A space force would help to reduce fragmentation and increase senior leadership attention to protect satellites. In a contested environment, the space force will need to bring together the components to protect these assets.”

The simple passage of time is also a risk. “In the future, there is a risk of losing knowledge about highly specialized payloads and technologies related to GPS and other military satellites. We have already seen programs affected by the loss of critical expertise,” Chaplain says. “Most of the space workforce are on the older side, and these payloads are very specialized; they’re almost works of art.”

The U.S. Air Force (which is responsible for the current GPS satellites) and other agencies are looking at potential supplements or replacements for GPS, Chaplain says. These might be the mega low Earth orbiting constellations that commercial industry is pursuing.

In addition, there’s the new Space Development Agency (SDA), which was just formed within the Department of Defense. At a meeting in June, the agency's director at the time, Fred Kennedy, said he planned to create an alternate navigation constellation that’s completely separate from GPS. If the government is denied the use of GPS, which Kennedy said he expected, he would then have an alternate source of navigation signals operating on different frequencies. (Kennedy has since stepped down from the post.)

At this point, it’s not clear whether the SDA will ever get the ability to build its own version of GPS and, if it does, whether that would siphon money from the existing GPS program. At this point, Congress has cut back funding for SDA, but lobbying by the administration for the agency and the larger effort of a space force continues.

Even if the SDA does get to move forward, it’s likely to be decades before it can field real competition to GPS.

GPS finding its way

In the meantime, with GPS III, the near future for GPS will see a much-improved constellation of satellites, better reception, and with international interoperability, much more accurate positioning. Given the crucial role GPS plays in the U.S. and global economies, and the role it now plays in everything from agriculture to flight safety, it seems highly unlikely GPS will be terminated by the U.S. government any time soon.

However, as Chaplain points out, the threats have not gone away. GPS satellites and their control systems may be vulnerable to cyberattacks. A successful cyberattack, whether from a state-sponsored entity or a criminal demanding ransom, could cripple a vast array of operations worldwide. Whether a space force will be required to protect GPS, along with similar forces from other operators of navigation satellites, remains to be seen.

What is clear is that GPS has become indispensable to commerce and more everywhere, so the risks of losing it have become immense.