GPS의 대안으로 양자측지 기술을 주목중인 펜타곤

[위종민]

최근 국방분야 버즈워드는 양자(quantum)인 모양입니다. 

미 DIU(Defense Innovation Unit)가 몇 년 안에 군용 GPS 위성을 백업하거나 보조할 수 있는 양자감시기술을 개발하기 위해 업체에 제아서를 요청했고, 수 십개의 제안이 들어왔다고 합니다. 

미 우주군은 GPS 시스템의 유연성을 강화하기 위해서 GPS 신호를 다양한 궤도 상에 분산된 위성에 GPS 신호를 분산하는 방법을 연구한다고 합니다. 링크된 기사를 찾아보니 기존 GPS 위성의 궤도 외에 지구저궤도나 정지궤도에도 위성을 배치한다는 내용이네요. 

GPS Without Space? DOD Looks to Quantum for an Answer

ARL’s Rydberg quantum sensor experimental apparatus, which was used to sample the radio-frequency spectrum from zero frequency up to 20 GHz and detect real-world communication signals. Army Research Laboratory

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GPS Without Space? DOD Looks to Quantum for an Answer

Nov. 27, 2024 | By Shaun Waterman

The Department of Defense is eyeing localized quantum sensors as a radical alternative to space-based Global Positioning System satellites in the face of increasing threats to GPS signals needed for precision navigation and timing.   

In a peer conflict, notes Lt. Col. Nicholas Estep from the Defense Innovation Unit (DIU), “you really must presume a denied and degraded environment in which you cannot rely upon external PNT signals like GPS.”  

That’s why DIU, the Pentagon’s acquisition outpost in Silicon Valley, is seeking commercial partners to help develop distributed, localized alternatives that don’t rely on easily jammed signals from thousands of miles above the earth’s surface.  

The military depends on GPS for navigation, timing, and targeting, and industries from transportation to agriculture to banking rely on its precision for a host of purposes. But the wars in Ukraine and the Middle East have exposed how signal jamming and spoofing can deny access to signals from space, forcing users to seek alternatives.  

“What are we going to do in order to maintain PNT-enabled solutions, to allow the joint force to execute its mission?” asked Estep, whose DIU portfolio includes quantum sensing, hypersonics and advanced materials.  

DIU solicited industry seeking quantum sensing technology that could augment or back up GPS satellites for military applications within a couple of years. The “project will focus on demonstrating the military utility of quantum sensors to address strategic Joint Force competencies,” DIU said at the time.  

Dozens of proposals poured in, Estep said: “We did get a very strong signal of interest from the community, a mixture of traditional primes, startups, and non-traditional companies.” 

The solicitation was designed to encourage a variety of approaches and solutions, Estep said. “There won’t be one quantum sensor to rule them all, that that the Air Force will use, that the Navy would want to use, that the Army [would want to] … There’s no panacea—quantum or classical—to address all of the joint force PNT needs.” 

Instead, he said, DIU would seek to marry the various approaches presented by industry applicants with appropriate use cases, based on the form factor and the maturity of the technology. “Some [approaches] may be better suited for aircraft. Some are better suited to support surface or subsurface vessels,” he said.  

DIU is working with multiple services and other stakeholders in the Department of Defense to get these innovative solutions into warfighters’ hands as quickly as possible, Estep said, “And so we help to coordinate these different technology solutions, with what we think best correlates to service deployment mechanisms and diverse mission sets… in several different parallel [acquisition] pathways.” 

The Space Force is also working on resilient space-based PNT solutions, including by spreading GPS signals out across a diversity of satellites in different orbits, as a means to make the system more robust and less susceptible to interruption. Indeed, resilient PNT was one of two capabilities identified by Air Force Secretary Frank Kendall for use under the new “Quick Start” funding authorities enabled by Congress to let the Space Force move ahead on some programs without having to wait for a full legislative review. 

Quantum Sensing 

Quantum mechanics involves the extraordinary, counter-intuitive, and often confusing properties of subatomic particles first explored by Albert Einstein nearly a century ago. Recent advances in nano engineering have enabled labs for the first time to demonstrate and exploit the unique properties of quantum particles, generating renewed excitement about the technology. 

Celia Merzbacher, executive director of the Quantum Economic Development Consortium (QED-C), an industry-led stakeholder forum supported by the National Institute for Standards and Technology, said that quantum sensing is among the least understood but most mature of three quantum mechanics fields—the other two are quantum computing and quantum communications. 

“Quantum sensing for PNT is, to some extent, already here,” she said. The technology is the same as that used in atomic clocks, which provide precise timing based on the movements of subatomic particles.  

In a September report, QED-C noted that “Quantum sensors can provide navigational information in environments where GPS signals are unavailable or unreliable.” 

The report and the DIU industry offering outline three ways quantum sensing can be applicable to PNT: Measuring movement, gravity, and Earth’s magnetic field.  

Each offers a way for a plane, ship, or vehicle to accurately ascertain its position, without having to rely on radio signals from faraway GPS satellites.  

Merzbacher predicted that DOD’s involvement could spur a commercial market for quantum sensing PNT within five years. Without DOD, it would take longer, she said, “because these companies that are developing quantum sensors for PNT and other uses are smaller companies, and they have somewhat limited resources to invest in anything that’s beyond two or three years to market.” 

This is precisely the kind of problem for which DIU was created—as a bridge to private equity. “Private capital is expensive and very hard to get,” Merzbacher said. DOD is effectively vouching for its view that a market could emerge. 

“Government can really accelerate progress by stepping in and helping to defray the cost of the engineering and R&D at this stage,” she explained. “Eventually the flywheel will be spinning, and as revenues are being generated, those companies can reinvest. But if the government doesn’t step in and invest … then progress will just be much slower.” 

The QED-C report identified the transition from lab to battlefield as a key hurdle. “A big challenge is integrating these new components that are really just being developed in the lab, in a controlled environment, integrating and packaging those into something that can go onto a plane or a Space Platform,” and withstand the rigors of vibration or radiation, she said. 

“There’s going to be a lot of work needing to be done,” she said. 

Meanwhile, China and others are investing in their own solutions, said Dana Goward, a career U.S. Coast Guard officer who is now president of the Resilient Navigation and Timing Foundation, a 501(c)3 scientific and educational non-profit. 

China (and U.S. allies South Korea and Saudi Arabia) already had a functioning terrestrial alternative to GPS in an Enhanced Long-Range Navigation (eLORAN) system, Goward said. eLoran relies on hyperbolic navigation, where a plane, ship, or vehicle can ascertain its location by correlating signals from two or more terrestrial broadcast towers. 

“It’s much more accurate, much more difficult to disrupt,” than GPS or other satellite-based PNT, said Goward. 

Goward called quantum sensing “exciting,” but said it could be “many years” before the technology clears all the necessary engineering and regulatory hurdles necessary for broad adoption. “How close are we to something that is viable in any commercial application?” he asked. 

GPS is now taken for granted by consumers and businesses, Goward said, and there is little understanding of how fragile it is. But technologies that require materials to be maintained at extremely low temperatures or to operate at extremely precise laser frequencies are hardly ready for prime time, he said. “They’ll keep making it better and better, and perhaps someday it will get down to the common folk like you and me.” 

Quantum Orienteering 

The supporters of quantum sensing for PNT say it represents a step change, away from the inherently fragile beacon-signal approach of GPS or even eLoran. “The next generation of PNT technologies returns positioning to the local vehicle or individual and it says, essentially, now we want to be able to navigate using only things that we measure locally,” said Michael Biercuk, CEO of Q-CTRL, a quantum technology company. 

Because the Earth’s magnetic and gravitational fields vary minutely from place to place and because those variations have already been mapped, a tool that can measure those minute variations can accurately locate the user, Biercuk explained. 

“If you combine a really good map of these geophysical phenomena with a really good local sensor, you can do what we sometimes jokingly refer to as quantum orienteering,” Biercuk said, “You can take your map and your sensor and figure it out where you are.” 

The extreme technical requirements of quantum sensing equipment can be mitigated by the use of software algorithms, he said.  

“The laboratory performance is extraordinary, but the performance outside the lab is tremendously degraded. Anytime you put it on a moving vessel, it’s really hard to keep it operational. They’re very, very sensitive devices,” he said. 

But Q-CTRL had been “able to show that when you combine, obviously very good hardware engineering with software enablement, you can actually make these tools viable in real environments,” he said.

The company is working with Airbus on safety-testing a GPS-replacement inertial motion sensor that could be installed in commercial aircraft “within two or three years,” he said.

Beyond GPS: Space Force Want Multiple Orbits, Backups for PNT

An artist’s concept illustrating Navigation Technology Satellite 3 in geostationary orbit. Air Force Research Laboratory graphic by 2nd Lt. Jacob Lutz.

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Seeking New Options for GPS, Space Force Eyes Multiple Orbits

Nov. 22, 2024 | By Greg Hadley

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.