Seeking New Options for GPS, Space Force Eyes Multiple Orbits

The Space Force’s best-known mission is often spelled out with just three letters: GPS. The world relies on U.S. military satellites for precise navigation and timing, and the Space Force delivers with its Global Positioning Satellite constellation.

But increasing use of jamming to block GPS signals and the risk that an adversary could seek to take out some or all of its 30 GPS satellites or distort signals in future conflict has Space Force leaders seeking back up alternatives.  

The Department of the Air Force selected in April an alt-PNT project as one of two new “quick start” programs it would pursue using new authority that allows it to progress without waiting for congressional approval. By September, Space Systems Command had selected four companies to compete to develop Resilient GPS solutions. USSF intends to launch eight small satellites by 2028. 

Congress members have faulted the program for focusing solely on new satellites while overlooking the need for jam-resistant encrypted M-code signals for military operations. But SSC Commander Lt. Gen. Philip A. Garrant pushed back on that criticism in Washington, Nov. 21. 

“It’s focus is really to bolster the civil code for added resiliency, but also it’s a different orbital regime,” he said. Because the new satellites “won’t be in the same planes as GPS,” Garrant added, the PNT enterprise will gain “orbital diversity.”  

Just as the Space Force has constellations operating in multiple orbits to bolster resilience, having PNT systems in low-Earth or geosynchronous orbits in addition to medium-Earth orbits, offers advantages: LEO satellites are far closer to the surface of the Earth, enabling a strong signal, and GEO satellites offer the benefit of a constant, steady presence overhead. 

The Space Development Agency, which is fielding a resilient space architecture of low-Earth orbit satellites, has already begun “embedding” PNT signals into its first data transport satellites. These nodes include information about position and timing while transmitting communications—not unlike a clock in the background of a video call. 

Looking ahead to future tranches of satellites, SDA will go a step further, providing a separate PNT signal from low-Earth orbit, said SDA Director Derek S. Tournear at an AFA Mitchell Instititue event on Nov. 19.

“We’re going to provide a lightweight signal service, PNT service,” Tournear said. “We’re working with the Army on exactly what that looks like. It will either be an L-band or S-band signal that goes out for things like munitions and things like that.” He defined “lightweight” as requiring “very low processing to receive the signal.” 

The Air Force Research Laboratory is also poised to launch its NTS-3 demonstrator satellite, but is waiting for the launch vehicle, ULA’s Vulcan Centaur, to be certified. NTS-3 will go to geosynchronous orbit and test new technologies like reprogrammable signals and a phased array antenna that can direct signals without physically moving the satellite. 

These developments point to a new-look GPS approach in the future, Garrant said: “I think it will in the future be a multiorbit phenomenology. We are very interested in alternate means of PNT.” 

A Space Force official, speaking on background Nov. 21, said commercial interests are also looking to develop their own PNT alternatives.

“There are a couple companies that are going and actually building out an exquisite alt-PNT constellation,” the official said. “They have found a commercial base, especially when you’re looking at potentially autonomous vehicles coming into play, so they definitely want to capitalize on that. Also, our airline companies are looking to potentially make sure that they have an alternate PNT signal.”

Airline operators have had challenges with GPS in contested areas near Ukraine and the Middle East over the past year, as signal jamming increased. 

Another potential way for commercial industry to tap into the market isby adding PNT signals to satellite communications networks, the official said. “Don’t offer it as an a la carte service, just make it kind of fundamental into the capability you’re providing, and then just amortize the cost or something like that.”

Such an approach would have value to the Pentagon, the offficial said. “We would pay a little bit more for that.”  

SpaceX, which operates the massive Starlink constellation, is already looking in that direction. The official said SpaceX’s presentation is “very logical.” 

All told, the Space Force may ultimately gain as many as a half-dozen or more GPS alternatives to choose from. Yet Garrant made clear that the existing GPS constellation remains “healthy.” 

“We’re not moving away from the traditional GPS constellation,” he said. 

Indeed, USSF has several new GPS III satellites stuck on the ground awaiting launch and is eager to get them into orbit. Garrant said Space Systems Command is looking “at options to go faster.” Though he did not say so directly, that could mean moving some satellites assigned to launch on ULA’s rocket to launch instead on SpaceX rockets so they get into orbit faster.