Oct 29th 2025|5 min read
THE TROUBLE with first-mover advantage is that it devalues quickly. Once the hard work of inventing a technology has been done, others are free to copy and improve it. Take the Global Positioning System (GPS). Designed for America’s armed forces in the 1970s, made available to civilians during the 1980s and declared fully operational in 1993, GPS was revolutionary: anyone with a receiver and a clear view of the sky could work out exactly where on Earth they were standing.
But these days GPS is showing its age. Other systems such as Galileo, a European satellite constellation, or BeiDou, a Chinese one, offer better accuracy—and, says William Shelton, a former general who led what is now the US Space Force, which runs GPS, are more robust against foul play.
America is therefore planning an upgrade. Testing recently began on Navigation Technology Satellite-3 (NTS-3). Launched in August, this is the first GPS test satellite to be sent into space since 1977. The results will inform the design of the next generation of GPS satellites, known as GPS IIIF, which are due to begin going up in 2027.
The idea behind GPS is simple. Thirty-two satellites orbit 20,200km above Earth. Each carries radio transmitters (with roughly the power of the light-bulb in a fridge) that between them cover the planet in signals. These electromagnetic murmurs can be sensed by receivers. Add a bit of mathematics, and anyone carrying such a device can work out their position to within a handful of metres (for something like a smartphone) or a few centimetres (for military or professional equipment).
The technology has rapidly become vital. Soldiers use GPS to work out where they are. Receivers are built into everything from cruise missiles to artillery shells to help them hit what they have been aimed at. Civilians rely on GPS, and its rival systems, for everything from satnav apps and self-driving farm equipment to mapping, wildlife tracking and managing logistics. To work properly, GPS relies on ultra-accurate timing signals generated by atomic clocks aboard the satellites. Electricity grids, mobile-phone networks and financial systems use those signals, which are available anywhere on the planet, to synchronise their own operations.
One of the Space Force’s goals is to make sure GPS can be relied upon in wartime. Because the signals are so weak by the time they reach the ground, opponents can drown them out by broadcasting more powerful ones. Such jamming has become a constant feature of the fierce electronic warfare on the front lines in Ukraine. Mr Shelton says that Pentagon types now fear that GPS, in its current form, “is unreliable”. NTS-3 is thus equipped with a new transmitter designed to concentrate the system’s military signals, known as M-code, into a relatively narrow “spot beam”.
Focusing transmitting power into a smaller area means the signals will be harder to jam. Joanna Hinks, an NTS-3 engineer at the Air Force Research Laboratory in Albuquerque, New Mexico, says one such spot beam would cover an area a bit smaller than Texas. Lockheed Martin, the American firm making the GPS IIIF satellites, says the new signals will be able to cut through roughly 60 times more jamming power than today’s can manage.
Another problem is “spoofing”. Here the idea is not to drown out the signal, but to replace it with a new, misleading one that will cause false readings. Pilots and ship captains regularly report spoofing, especially in the Middle East and near Russia. The clumsiest attacks, says Victoria Samson of Secure World Foundation, a think-tank, are given away by their absurdities, like ships appearing to be on land, or clocks seeming to run backwards.
Part of the problem is that GPS still uses radio signals designed in the 1970s. These are “tremendously obsolete” and utterly insecure, says Logan Scott, an engineer who has worked for a variety of GPS contractors and is a consultant to NTS-3. Details of how the signals work are public knowledge, which makes it easy to copy or alter them using cheap, protean software-defined radios. With BeiDou and Galileo, signals can be tweaked by software updates beamed from the ground, which makes spoofing harder. Another of NTS-3’s jobs is to test a similar capability for GPS.
The satellite will also test another anti-spoofing system called CHIMERA. The idea is to insert secret features, known as watermarks, into the GPS signals at certain intervals. Receivers set these signals aside until the arrival, a moment later, of a follow-on signal. The second signal reveals the times at which the watermarks in the original signal were transmitted. This allows the receiver to check the times at which the watermarks in the original signal actually arrived—and, crucially, determine if enough time has passed for the watermarks to have travelled from a distant orbit, rather than a nearby spoofer.
Atomic clocks aboard GPS satellites do occasionally conk out, and even minuscule “drifting” over time can produce errors. The current generation of satellites therefore sport two back-up clocks each. Before a back-up can be used, though, it has to be warmed up, a process that can take a satellite offline for days. NTS-3 is testing an alternative approach by running two clocks at the same time.
But timing has caused other sorts of problems with the new satellites. The software designed to run the upgraded system, known as OCX and developed by RTX (formerly known as Raytheon), has been plagued with delays—to the point that one retired senior official now regrets not forcing a handoff to another company. It was eventually delivered to the Space Force in July, but the $3.7bn cost could more than double by the time testing is complete, perhaps next year. However advanced the technology becomes it seems some things in military procurement never change. ■
Subscriber only | Simply Science
Delivered to you every week
Yes, I agree to receive exclusive content, offers and updates to products and services from The Economist Group. I can change these preferences at any time.