GPS World

Tag: quantum

  • Navigation tools aim to compliment GPS

    Navigation tools aim to compliment GPS

    News from the Chicago Quantum Exchange

    Quantum technologies may offer a solution to GPS jamming and spoofing, according to the University of Chicago. Already, prototypes are being tested of a suite of sensor-based techniques that do not rely on satellite signals. 

    GPS jamming and spoofing have emerged as growing threats in recent years, according to the Chicago Quantum Exchange, based at the university. In 2024 alone, more than 1,000 commercial flights per day were affected by GPS spoofing, especially while flying through regions like the Middle East and Eastern Europe. 

    During these incidents, in-flight instruments show pilots that their aircraft is flying higher or lower than they truly are or that they are miles off their actual location. In maritime settings, spoofed GPS signals have even caused ships to veer off course or run aground. These are not isolated glitches but the result of deliberate electronic warfare tactics.

    Corporate partners of the Chicago Quantum Exchange, including Boeing, Infleqtion and SandboxAQ, are among those developing applications. The CQE is a hub that connects leading universities, national labs, and industry partners to advance quantum technology.

    “Governments and the commercial industry are in dire need of this technology,” said Ken Devine, senior product manager for quantum navigation at SandboxAQ. “The geopolitical issues happening across the world, and the ramp up in both jamming and spoofing — Russia, Ukraine, the Middle East, Israel, Iran — everyone’s getting super disruptive, and that’s not going to go away anytime soon. Everyone is saying, ‘We basically need this yesterday.’”

    In May 2023, SandboxAQ completed the first of many flight tests for the United States Air Force and its commercial aviation partners, including two major Air Force exercises that year. 

    In 2024, Boeing completed the world’s first recorded flight using multiple quantum navigation systems, testing the ability of these sensors to navigate across the central U.S. for four hours without GPS. 

    The Boeing test incorporated two different technologies. The first is a magnetic field-based navigation system called AQNav from SandboxAQ, It uses map matching, though the map that they use is of the Earth’s crustal magnetic field rather than terrain. Infleqtion is investigating both techniques. The second is an inertial navigation system from quantum sensing technology company AOSense. 

    Jay Lowell, principal senior technical fellow at Boeing, said it was vital to consider “whether and how” the different technologies could be used together. “Maybe that means a tradeoff of performance between sensors in moments where one struggles and the other’s strong,” Lowell said. “Fundamentally, it means we just need to understand whether their combined data is better than either one alone.”

    Detecting tiny changes 

    Inertial navigation depends on accelerometers and gyroscopes — which respectively measure acceleration and rotation — to measure movement. An inertial sensor tracks how an object moves from a known starting point by recording changes in its speed and direction.

    While basic accelerometers are common in smartphones and fitness trackers, quantum inertial sensors can detect changes in motion down to the femtometer — less than the width of an atom — making them extraordinarily precise. Inertial sensors have applications in space-based technology, since they do not need maps or fixed points to navigate. 

    Infleqtion recently completed commercial flight trials of inertial-based quantum navigation in the United Kingdom and plans to conduct tests in the U.S. as well. Infleqtion’s Chicago office is also developing an AI-powered tool called SAPIENT that won first place in the U.S. Army’s xTechScalable competition.

    “[SAPIENT] is focusing on the software side, taking the outputs of multiple kinds of sensors and stitching them all together with AI to provide a more robust navigation signal,” said Pranav Gokhale, general manager of computing at Infleqtion. “There is a big gap between an inertial measurement unit and a full inertial navigation system, so we’re using AI to fill that gap.”

    Alternatively, magnetic navigation, or MagNav, works much like terrain-following radar, comparing real-time sensor data to a known map to pinpoint location. 

    But instead of elevation, the aircraft senses subtle magnetic fluctuations in the Earth’s crust — variations caused by geology, mineral deposits and even human infrastructure — and compares its measurements to a corresponding map of that field. 

    Scientists believe that birds can use their ability to sense the Earth’s magnetic field to navigate in a similar way. Magnetic field maps of the globe are frequently done for mineral, oil and gas surveys, as small anomalies in the field can indicate resources underground. But there are areas where high-resolution maps can be hard to come by. 

    “Map quality in the region you’re going to is definitely a factor that gets plugged into how well magnetic navigation can perform,” Devine said. 

    He identified a list of other key variables, such as the type of aircraft being used, plus its altitude and speed, as additional points of consideration for MagNav technology. At the same time, he said the importance of these tools is likely to grow as electronic warfare strategies become even more entrenched.

    “We’ve validated that we can do real-time navigation with this technology,” Devine said. “And that’s huge, because the need for it is only going to increase.”

  • Australian Navy trials validate quantum solution for GPS denial at sea

    Australian Navy trials validate quantum solution for GPS denial at sea

    Q-CTRL has completed a major field trial with Australian Defence on board the Royal Australian Navy’s Multi-role Aviation Training Vessel (MATV), the MV Sycamore. The results of the trial demonstrated advancements in software-ruggedized quantum sensing for navigation.

    In the trials, Q-CTRL field deployed a quantum dual gravimeter, which measures tiny variations in Earth’s gravity as part of a next-generation quantum-assured positioning, navigation, and timing (PNT) system operable when GPS is unavailable or untrusted.

    This first trial saw over 144 hours of continuous operation and successful data collection with no human intervention during real maritime operations. 

    “Quantum sensors provide a near-term opportunity to achieve transformational defense capabilities, but previous deployments in the field have struggled to deliver defense-relevant performance,” said Q-CTRL CEO and founder Michael J. Biercuk. “Operating on a real moving vehicle is just not the same as conducting a science experiment; at Q-CTRL, we’ve taken a different approach to getting quantum sensors out of the lab, focusing on software as the critical enabler of performance in the real world.”

    Earlier this year, Q-CTRL announced successful airborne field trials of a new generation of quantum-magnetic navigation solutions, Ironstone Opal, validated for the first time to outperform comparable conventional alternatives in challenging real-world settings by 50 times. 

    Developed and fielded in 14 months, the dual gravimeter was installed in a “strapdown” configuration (bolted to the floor) in the space of a single server rack in a communications room onboard MV Sycamore. The sensor consumed only 180W of power – about 10 times less than a household toaster.(Photo: Q-CTRL)
    Developed and fielded in 14 months, the dual gravimeter was installed in a “strapdown” configuration (bolted to the floor) in the space of a single server rack in a communications room onboard MV Sycamore. The sensor consumed only 180W of power – about 10 times less than a household toaster.(Photo: Q-CTRL)

    The newly announced trials of Q-CTRL’s gravimetric navigation technology open opportunities to bring quantum-assured navigation to maritime vessels where magnetic navigation can be less effective. 

    GPS denial has become one of the most pressing strategic challenges in both defense and commercial settings, risking major disruptions to civilian and military operations. Quantum navigation promises a robust and reliable GPS backup that cannot be jammed or spoofed. 

    Q-CTRL’s navigation capability is urgently needed in contested maritime environments, as instances of spoofed signals caused significant disruptions to ships in the Middle East waterways as recently as June 23. This causes not only critical logistical issues but disrupts collision avoidance efforts, revealing major safety implications.

    In quantum gravimetric navigation, the quantum gravimeter continuously “sees” the otherwise invisible hills and valleys in Earth’s gravity, allowing a navigation computer to compare its observations against known gravity maps. This is similar to orienteering, where one can position oneself on a map by identifying landmarks like valleys, mountains, rivers, or roads.  GPS is not needed, making it a robust backup in contested regions.

    Q-CTRL’s demonstration with the Royal Australian Navy departs from most previous quantum sensing field trials in that these tests mandated peak performance with full autonomy and without the addition of any special infrastructure. The sensor had to operate as a real navigation system would operate during a defense mission. 

    The ship’s motion and engine vibrations were sufficient to cause total loss of signal using conventional operating techniques typically employed in research experiments. To address these losses, Q-CTRL’s software-ruggedization strategies recovered operation even while MV Sycamore was underway.

    Quantum sensing leverages the physics of light and matter on the smallest scales to enable the detection of tiny signals. Because these devices work based on the fundamental laws of physics and are not affected by drift like other GPS alternatives, their outputs do not change over time, enabling new opportunities where long-term stability is essential. Generally, however, these devices are significantly degraded when taken from a research laboratory into the real world, an issue addressed by Q-CTRL’s software-ruggedization technology.

    For more on Q-CTRL’s software-ruggedized quantum sensing technology, read their peer-reviewed technical demonstration published in Nature.

  • Leidos uses quantum technology to thwart GPS jamming

    Leidos uses quantum technology to thwart GPS jamming

    Susceptibility to jamming is a significant military vulnerability of the GPS signal. Through a Defense Innovation Unit contract, Leidos is developing an alternative navigation technology that measures variations in the Earth’s magnetic field and harnesses the quantum properties of nitrogen in diamonds. 

    “With magnetic navigation (MagNav) there’s no signal to jam,” said Aaron Canciani, manager of the Leidos Transition of Quantum Sensing (TQS) team and a former U.S. Air Force scientist who is a pioneer of the technology. “The one thing MagNav does need is a very sensitive magnetometer, which is where quantum comes in.”

    Quantum sensing uses microscopic particles that can simultaneously exist in multiple states to more accurately detect aspects of geophysical properties like magnetic fields. Leidos has been doing quantum work for years, applying it to a variety of cyber security and sensing applications. 

    “Quantum magnetometers have the potential to greatly increase position and attitude accuracies in magnetic navigation systems,” Canciani said. “Nitrogen vacancy-diamond magnetometers use the crystal structure of a diamond to define a sensing axis in which quantum measurements of the complete vector field can be known to exquisite accuracies.”

    The sensor is being developed by Frequency Electronics Inc. under subcontract to Leidos and in collaboration with MIT Lincoln Lab.

    Compared to classic magnetometers, which tend to drift due to reliance on relative measurements, Canciani added, “These quantum measurements are linked to the magnetic field through fundamental physics-based constants.” 

    Ultimately, Leidos intends to fly a MagNav system with the new magnetometer. If successful, the technology has the potential to significantly advance navigation technology for military use.  

  • UK leading the West in PNT with clocks, eLoran and quantum research

    UK leading the West in PNT with clocks, eLoran and quantum research

    Saying the government must focus on “delivering an operational resilient positioning, navigation and timing (PNT) system for the United Kingdom as soon as we can,” the British Science Minister, Lord Patrick Vallance, announced several initiatives in his opening remarks to the Royal Institute of Navigation’s UK PNT Leadership Seminar on Nov. 20, 2024.

    Among them was a funding increase for the National Physical Laboratory’s National Time Centre (NTC) project from £30 million ($38 million) to £62.7 million ($79 million) and a plan to have NTC and the first of the nation’s new eLoran towers at initial operating capability (IOC) by January of 2027.

    Plans for all efforts beyond next year were necessarily “subject to spending review.”

    Still, seminar attendees were gratified to hear the minister’s endorsement of the 10-point PNT policy framework published by the previous administration in 2023 and his commitment to operationalizing it with implemented systems.

    Shabana Haque, Ph.D., head of the United Kingdom’s National PNT Office, also addressed the seminar and elaborated on the government’s actions to date and plans moving forward. She also discussed efforts toward developing quantum technologies and how all the capabilities would be incorporated into a coherent architecture.

    Photo: RNT Foundation
    Photo: RNT Foundation

    Clocks

    The United Kingdom recognizes time and timing as the most fundamental component of the PNT utility. Its NTC R&D program, run by the National Physical Laboratory (NPL), has been up and running since 2019. Its primary objective is to create “…a resilient UK national time infrastructure through the building and linking of a new atomic clock network distributed geographically in secure locations.”

    Five years later, that program is coming to an end. Plans are in the works for the next phase of the NTC program, which includes developing a national timing infrastructure and supporting a new timing ecosystem — one that includes two-way satellite-time transfer (TWSTT), eLoran and the country’s legacy MSF radio time service. The industry will have a valuable role in the architecture of time distribution and providing value-added services while accessing highly resilient and well-authenticated core government time infrastructure.

    As a result of NTC work to date, traceable time and frequency signals can now be accessed by industry and academia from three NPL nodes dispersed across the United Kingdom. They are at the University of Strathclyde in Scotland, the University of Cranfield in the Midlands and the University of Surrey in the south.

    eLoran

    eLoran also features prominently in the United Kingdom’s PNT plans. Britain operated Loran-C as part of the Northern European network until the end of 2015. For the last year of that, differential stations were deployed along the United Kingdom’s eastern coast and maritime operations based on eLoran were authorized.

    On Jan. 1, 2015, and despite British pleas to the contrary, other northern European nations terminated Loran broadcasts in favor of Galileo. The United Kingdom has continued to operate its single eLoran transmitter as a national time signal. Plans call for additional transmitters to enable eLoran navigation across the nation and its adjacent waters within the next two years.

    UrsaNav Loran monitor on Nautel equipment. (Photo: RNT Foundation)
    UrsaNav Loran monitor on Nautel equipment. (Photo: RNT Foundation)

    The UK government has been working with several partners to advance its understanding and plan for the implementation of an eLoran capability. Haque highlighted work with the European Space Agency’s NAVISP program, resulting in the British company Roke developing an eLoran antenna for handheld devices.

    She also discussed integrating the NTC’s clock and fiber network with eLoran signals and developing GNSS/eLoran receivers.

    Many were particularly interested in an “eLoran Effectiveness Report” that the government commissioned and received from the General Lighthouse Authority’s Research and Development (GRAD) team. GRAD has extensive experience with the technology, having operated and evaluated the differential eLoran system along Great Britain’s east coast.

    In a related move that helped signal the United Kingdom’s commitment to the technology, the Ministry of Defence issued a Request for Information (RFI) in September 2024 about a deployable eLoran capability. The RFI indicated that the document was a prelude to an acquisition.

    Quantum research

    The United Kingdom has invested more than £1 billion ($1.3 billion) into quantum research, which has the potential to contribute to PNT with better timekeeping and inertial and gravimetric sensing.

    One aim of the quantum research program is to develop “…new navigation and timing systems to provide resilience and improved accuracy in the event of the denial of satellite systems.” A specific goal is to deploy quantum navigation systems, including clocks, on aircraft by 2030.

    The program began in 2014 and has seen a significant increase in 2024 with the establishment of five quantum hubs nationwide. The hub at the University of Glasgow focuses on resilient PNT systems for national security and critical national infrastructure.

    Policy and coordination

    Minister Vallance and Haque also discussed two important non-technology themes.

    The first was that the United Kingdom’s PNT office is fully funded, staffed, and very active. It was created last year as a cross-government effort and includes representation from the Ministry of Defence. In addition to pushing the nation’s PNT efforts forward, the office has been engaged with numerous other governments, including those of the United States, Canada, Australia, New Zealand, Europe, Japan and Korea.

    USCG Loran tower circa 1995. (Photo: RNT Foundation)
    USCG Loran tower circa 1995. (Photo: RNT Foundation)

    Second, while the PNT initiatives are necessary for the nation’s resilience and security they will also be a source of economic benefits. This goes beyond enabling the British economy to function during local and potentially widespread GNSS disruption events. As the nation develops the technology stack to support its own resilient PNT architecture, along with enabling and supporting policies, resilient PNT devices and services will become marketable to others.

    A sovereign PNT capability that can both stand on its own and cooperate with GNSS is becoming increasingly attractive to many nations. Being able to source such a capability from a respected and trusted ally such as Great Britain could make acquiring and implementing such a system much easier for many.

    The UK Science Minister also praised the RIN’s work and publication of a series of tools to help explain PNT and the need for resilience to those outside the community. The tools also will help organizations evaluate their readiness for GNSS disruptions.

    Available from the RIN’s Resilient PNT Portal, they are

    • A PNT explainer that outlines risks from over-dependence on GNSS and provides links to other informative resources.
    • A best practices “placemat” describing a “Prepare, Act, Recover” framework for PNT disruptions.
    • A PNT resilience checklist for organizations to use to self-evaluate their risk from GNSS disruptions.

    The RIN recommends PNT experts use these tools working with customers, suppliers, and partners and act as a “guiding hand.”

    The RIN sees these all as a “phase 1 release.” Feedback on the tools is encouraged and should be sent to [email protected]. The RIN team is eager to know what works and what could be improved, as well as to receive suggestions for other efforts.

    As a “learned society,” the RIN has a significant influence on government policy and direction. This was recognized by Lord Vallance, saying, “The Royal Institute has played a really important role in recent years to highlight the PNT opportunity and risk, to provide expertise, and to work with government on solutions.”

    The RIN’s director, John Pottle, and RIN Fellows Ramsey Faragher, Guy Buesnel and Andy Proctor were all recognized during the seminar for their contributions to the organization’s resilient PNT efforts.

    UK leading the west

    While China is in the final stages of establishing a nationwide clock system integrated with eLoran and signals from space, and South Korea is following suit, the United Kingdom seems to be the only Western nation in the process of establishing a coherent and resilient national PNT systems-of-systems architecture.

    Some nations have substantial fiber timing networks, Europe seems to be on the path to a timing backbone, and the United States has three eLoran transmitters on air. However, none have announced the type of integrated plans the UK has published.

    When asked about this, one UK PNT technology and policy expert opined that his nation is so far ahead of Europe and the United States because “we are unencumbered by having our own GNSS.”

    His idea is that GNSS involves a lot of time, effort and money. The kind of financial and emotional commitments needed for these huge projects makes it hard for many to come to grips with the limitations and vulnerabilities of GNSS and the need to implement complementary systems. Both government officials and GNSS industry lobbyists may tend to resist such efforts, he said.

    Concerning the UK government’s investment in OneNav, he said it is still possible that the United Kingdom might also pursue a space-based capability. Rather than establishing the capability on its own, in his opinion, the government will be much more likely to look for a commercial subscription service.

    “We will access GNSS when we can trust it, and may pay for other signals from space,” he said. “But we want a sovereign capability for the United Kingdom, and the future of resilient PNT is terrestrial.”

  • Lidar-based system for high-speed tolling coming soon to US highway

    Lidar-based system for high-speed tolling coming soon to US highway

    First commercial deployment to be installed on a major turnpike used by tens of millions of vehicles every year

    An electronic tolling system that uses high-performance lidar sensors from Cepton and a vehicle identification solution from Red Fox ID is expected to be deployed on a major highway turnpike crossing multiple states in the United States.

    The turnpike project is expected to provide fast, accurate, real-time tolling to enable smooth traffic flows. Specifics of the project — including states involved and the timeframe of installation — were not disclosed.

    Photo: Cepton
    Photo: Cepton

    Based on an extended collaboration with leading lidar solution provider Cepton, Red Fox ID — a designer and developer of vehicle identification and classification solutions — has developed a multi-lane, free-flow tolling system called Quantum, which is able to accurately detect, track and classify vehicles of any size or type at highway speeds.

    Quantum uses Cepton’s Micro Motion Technology (MMT)-based Sora-P60 or Sora-P90 lidar sensors for high-resolution vehicle profiling, to enable integrators and road operators to achieve highly accurate customer billing in real time, with free flow, barrier-free tolling.

    For tolls to be charged correctly based on vehicle class, traditional tolling systems often use tollbooths for manual processing or depend on vehicle speed-reduction infrastructure to allow for time to capture vehicle information. That can cause congestion, increased emissions and frustration among customers.

    Advanced systems that aim to enable faster tolling are often subject to significant errors, such as missed vehicles or wrong vehicle classification, because of limitations of the sensors being used, such as cameras and weight-based ground sensors. Vehicle-classification errors can have significant operating cost consequences for tolling operators, while leakage leads to lower revenues. With tollways processing tens of millions of vehicles a year, the cumulative impact of inaccuracies and errors creates significant administrative costs, losses and customer dissatisfaction.

    Red Fox ID’s Quantum solution adds an extra layer of accuracy to the tolling system by integrating Cepton’s lidar technology. A gantry-mounted system using Quantum is able to accurately detect and track vehicles even as they switch lanes. Quantum captures and extracts high-quality information, such as vehicle velocity, size and class. All of that information is used as input to a separate billing system to compute and apply the appropriate tolling charge.

    Quantum can also direct camera-based systems on the gantry to capture a vehicle’s front and rear plates in the event that a transponder cannot be detected. Through these innovations, Quantum has demonstrated a vehicle-detection accuracy in all traffic conditions of 99.96%, an axle-classification accuracy in all traffic conditions of 99.9% and a vehicle-length accuracy of +/-5%. The system uses Cepton’s Sora-P sensor family which has been tested and proven during extended trials, including in various weather and light conditions.

    The recently released Sora-P90 lidar features a 380-Hz frame rate to deliver 1140 line scans per second, providing high-fidelity profiling of vehicles passing at highway speeds. Powered by Cepton’s patented, rotation-free, frictionless and mirrorless MMT, the Sora-P90 is rugged, reliable and scalable, making it suited for automated tolling applications.With a 90° horizontal field of view, the lidar can be set up using one gantry instead of two separate sensors and gantries, making overall deployment more cost effective.

    Red Fox ID has been working with Cepton on multiple trials and proof of concept projects across the globe since 2019. This has allowed both partners to expand the application of advanced lidar intelligence for high-accuracy tolling on highways and roadways in a growing list of countries, across North America, Europe, the Middle Eas, Africa and Asia.

    “Our industry’s drive for overhead tolling solutions has failed to materialize in the mainstream due, primarily, to a lack of sensors capable of achieving the high levels of accuracy required for a modern tolling product,” said Steve Bird, CEO of Red Fox ID. “The technical innovations enabled by Cepton offer us new design options. Improvements in the resolution of the data, the ability to deal with the full range of weather-related conditions, and the development of a sensor with an in-service lifespan suitable for tolling make it possible, for the first time, for us to develop an accurate, overhead free flow system. Our partnership with Cepton will be a game-changer in revolutionizing the tolling market.”

    “It is very clear that lidar’s uses extend far beyond just serving as the ‘eyes’ of autonomous vehicles,” said Jun Pei, CEO of Cepton. “Our lidar technology has a huge part to play in making our transport infrastructure smarter, safer, greener and more efficient, as we can see here following Quantum’s highly successful real-world testing. The key to success for toll operators and providers is minimal error and maximum yield, and we are excited to be partnering with Red Fox ID to help our mutual customers achieve this goal with our market-leading lidar technology. We look forward to working with them to expand our partnership worldwide.”

  • The promises of M-code and quantum

    November has certainly been a busy month, and I’ve been lucky enough to be involved in a number of standout events where defense PNT was discussed.

    The National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board met in California; GPS World hosted a webinar on military PNT technology; and the International Navigation Conference took place in the U.K. Check out a brief roundup of what’s been taking place.

    Next-generation GPS takes steps in the right direction

    The December issue of GPS World magazine has an excellent update from Col. Steven Whitney. GPS itself is often referred to as the “gold standard” by which other GNSS and PNT solutions are benchmarked. And GPS is undergoing a fairly monumental modernization program, in order to stay current and provide the right services to the military. There are broadly three aspects to this: the next-generation ground segment, the space segment, and the user equipment.

    It’s fair to say that the ride hasn’t been a particularly smooth one, and the Next Generation Operational Control System (OCX) has been plagued by delays and challenges. Following a Nunn-McCurdy breach in 2016, the future of the OCX development program looked to be hanging on a knife edge, but the program was recertified and continued.

    At the PNT Advisory Board meeting on Nov. 15, Col. Gerry Gleckel (deputy director, GPS Directorate, Space & Missile Systems Center) gave an upbeat presentation on the status of GPS modernization. Describing the current status of OCX as “working through program challenges,” he described how the first integrated launch rehearsal between GPS III and OCX Block 0 had been completed in August.

    The GPS III satellites themselves are in full production flow, with five satellites at various stages of assembly.

    Figure 1. Five GPS III satellites are in production flow. (Credit: Gerry Gleckel, Nov. 15, 2017).

    The next-generation military receivers, known as Military GPS User Equipment (MGUE), are also under development by a range of vendors, of which L-3 Technologies was the first vendor to receive security certification in 2016. A number of equipment form factors are being developed to address land, sea and air platforms, and great progress is being made.

    Figure 2. Military GPS User Equipment (MGUE) will address a range of platforms. (Credit: Gerry Gleckel, Nov. 15, 2017)

    The U.S. Air Force recently completed a number of successful test flights of a prototype M-code receiver on board a B-2 stealth bomber, which marks an important milestone for the GPS modernization effort. Let’s remind ourselves what M-code is, and what it does for us.

    The promise of M-code

    Until now, the military has relied on the encrypted P(Y) code to provide advantage on the battlefield. Compared to the civilian C/A code, the P(Y) offered improved accuracy, ionospheric correction, resistance to spoofing and a marginal level of jamming resistance.

    M-code is quite a different picture. Rather than the traditional BPSK modulation schemes used by legacy signals, M-code utilizes a type of binary offset carrier (BOC) signal. In the case of M-code, the signal is a BOCsin(10,5) modulation, which has a power spectral density given by:

    This power spectral density can be seen in the figures below, along with legacy C/A and P(Y) codes (and also the new L2C signal on L2). The M-code BOC signal has a number of important properties; I won’t describe all of them, but I will pick out a couple.

    Firstly, the signal is able to support navigation warfare activities. Because the energy in the signal is spread in two lobes away from the center, it allows for the C/A code to be selectively jammed without affecting the military receivers. This is often referred to as “blue force jamming” or “blue on blue jamming,” where friendly forces might wish to perform jamming in an environment in which they are themselves operating. Currently, such blue force jamming is not possible with P(Y) code receivers, without also degrading the friendly force’s receiver.

    Another promise of M-code is the ability to use spot-beam transmissions from Block III satellites. This is where a high-gain antenna on the satellites aims the M-code signal at a specific region of the earth, with much greater received satellite power in that region. The received signal from the spot beam is expected to be around 20-dB more powerful than the conventional full-Earth coverage beam. This means that, in a given conflict region, military GPS receivers should be able to benefit from a large increase in jamming resistance.

    Figure 3a. M-code signal compared to traditional L1 GPS signal. (Image: Michael Jones)

    Figure 3b. M-code signal compared to traditional L2 GPS signal. (Image: Michael Jones)

    Shortly after the GPS Advisory Board meeting in California, on the other side of the Atlantic a range of defense PNT technologies was also discussed.

    International PNT experts gather in the UK

    The International Navigation Conference (INC 2017) is now in its third year, and has been steadily growing in prominence. This year’s event, which took place Nov. 27-30, focused on the themes of resilient PNT, autonomy, and sensor and data fusion. As usual, there was a substantial defense presence.

    I had the pleasure of chairing a few sessions, including a panel discussion on resilient PNT. The event began with a cross-government meeting, where representatives from across the UK government met to discuss PNT issues concerning defense and national security.

    What I loved about this conference is the sheer diversity of PNT topics that were discussed. In the military domain, it wasn’t just the traditional subjects of GNSS, inertial, visual and signals-of-opportunity that were discussed. Also considered was cognitive navigation — how does a soldier’s brain work when in an unfamiliar battlefield? And how will quantum technology benefit defense PNT in the medium to long term?

    The promise of quantum

    Quantum technology has for some time been touted as the future of PNT: clocks so accurate that you’ll never need to worry about timing again. Inertial measurement units that have so little drift, you’ll never need anything else for navigation.

    If you’re not familiar with quantum technology, let me explain. Quantum technology exploits science that cannot be explained by classical physics, such as Newtonian mechanics, thermodynamics and Maxwell’s electromagnetism.

    As atoms get colder, they have lower energy levels and move more slowly. Taking this argument all the way down to absolute zero, the atoms would stop moving. By using lasers to cool atoms to very near absolute zero, the atoms are essentially placed under precise control, and hence are sensitive to changes in the local magnetic and gravitational fields. What does this mean for navigation?

    An excellent INC 2017 session on quantum navigation revealed some of the answers. Dr. Tim Freegarde of the University of Southampton gave the keynote “Navigator’s Introduction to Quantum Technologies,” which was followed by sessions on quantum/classical combined navigation, and quantum technology for performing gravity gradient map matching.

    Quantum sensors rely on a phenomenon known as entanglement, where two physically separated systems are linked in such a way that a measurement of one affects the results of the other. Once atoms have been cooled, they can be made to travel in opposite directions around a loop, where the interference pattern generated allows rotation to be sensed.

    But the atoms can also be sensitive to gravitational and magnetic fields, and frequency. So, amongst many other things, quantum technology allows for more accurate atomic clocks, and rotational and gravitational sensors.

    A huge amount of money has been poured into quantum research in recent years and, whilst it’s clear there is still a long way to go, progress is certainly being made. At the UK National Quantum Technology Hub in Sensors and Metrology, the focus is on achieving sensors that are useful, and not necessarily to look for the highest possible precision. This is essential if quantum sensors for PNT are to be adopted by governments and industry.

    Cyber takes center stage

    At the end of the conference, I had the pleasure of chairing a lively panel discussion on resilient PNT, where I put a number of questions to both the panel and the audience.

    Coming back to satellite navigation, my first question was, “What is the greatest threat to GNSS over the next three years?” You may be forgiven for thinking that “jamming” or “spoofing” was the top answer because, no, the top answer was in fact “cyber attack”.

    Figure 4. At the International Navigation Conference, the audience voted “cyber attack” as the greatest threat to GNSS. (Photo: Michael Jones)

    But what exactly do we mean by “cyber attack”? The word “cyber” is a pretty loose word, which is often misused as a catch-all phrase to cover anything that’s not RF related. Let’s quote the NIST definition of cyber attack:

    “An attack, via cyberspace, targeting an enterprise’s use of cyberspace for the purpose of disrupting, disabling, destroying or maliciously controlling a computing environment/infrastructure; or destroying the integrity of the data or stealing controlled information.”

    How does this apply to military PNT? Well, a key theme from the conference was the trend towards more complex PNT systems. No longer do we have a simple GPS receiver, but an ever-increasing mix of different PNT sensors, and a system more comparable to a computer than a traditional GPS receiver.

    What this means is that modern and future military PNT will be susceptible to the full range of cyber attacks currently associated with computing environments. Guy Buesnel from Spirent Communications gave an excellent keynote presentation where he covered this topic. Describing the “attack surface” for GNSS, he noted how many GNSS receivers currently run embedded operating systems such as VxWorks or Linux, and many support standard protocols such as TCP/IP and USB, all of which leaves them vulnerable to cyber attacks.

    But let’s not despair. The good news is that there is an awful lot to learn from the computing domain. After all, when computers first became vulnerable to cyber attacks, we quickly learned to make use of virus checkers, firewalls and other such mechanisms available to us. And now the domain of cyber security gives us an arsenal of defensive measures to combat cyber-space risks.

    I’ll finish by returning to the PNT Advisory Board meeting in California on Nov. 15, where Harold Martin, director of the National Coordination Office for Space-Based PNT, said “GPS is more computer than radio… GPS receivers lack cyber resilience. This is a national issue.”

    Don’t forget it.

    Equation figure: Michael Jones

  • Precision Timekeeping with Chip-Scale Atomic Clocks

    Sponsored by: Symmetricom
    Broadcast Date: Thursday, March 7, 2013
    Speaker: Steve Fossi, Director of New Business Development, Symmetricom
    Panelist: Ravi Pragasam, Marketing Manager, Embedded Solutions, Symmetricom
    Summary: Atomic clocks have enabled a world where ultra-precise timekeeping is now mandatory for communications, navigation, signal processing and many other applications critical to a modern functioning society. Symmetricom has utilized leading-edge technology and multiple innovations in various disciplines such as semiconductor laser technology, silicon processing, vacuum-packaging and firmware algorithms to deliver the Quantum SA.45c CSAC (Chip Scale Atomic Clock). Attend this webinar and learn how the CSAC can address your requirements for a precise clock without consuming excessive power or taking up too much space in your application.