Systems like GPS, Russia’s GLONASS, China’s BeiDou, and Europe’s Galileo systems are Global Satellite Navigation Systems (GNSS) that provides real-time positioning, navigation and timing (PNT) data. The system provides critical navigation capabilities to military systems including UAVs, soldiers in the dark or in unfamiliar territory, missile and projectile guidance, target tracking, precision munitions, search and rescue, and to coordinate troop and supply movement.
However, in many environments in which military operates (inside buildings, in urban canyons, under dense foliage, underwater, and underground) have limited or no GPS access. Similarly, GPS signals can be significantly degraded or unavailable during solar storms.
GPS is also vulnerable to jamming attacks, GNSS jammers are now being used by criminals or vehicle hijackers, as reported by the FBI: “… GPS tracking devices have been jammed by criminals engaged in nefarious activity including cargo theft and illicit shipping of goods.Typical military jammers are able to affect GPS receiver for many tens of kilometers by line of sight. It’s a problem because best accuracy, availability and global coverage of PNT data is through GPS/GNSS.
Militaries are taking two approaches one is integration of GPS with complementary technologies such as chip-scale atomic clocks and small inertial measurement units of the Microelectromechanical Systems (MEMS). Other approach is developing entirely new PNT technologies.
Rafael’s “Iron Flame” – an autonomous precision artillery rocket system- relies on a guidance capability based on image comparison. This makes it immune to GPS jamming as well enable them to execute a very accurate strike with minimum collateral damage even in urban scenarios, using aerial reconnaissance photographs as a reference image.
Honeywell, for its part, is “working on numerous alternatives to GNSS aiding, including vision aiding, collaborative aiding, celestial aiding, terrain-aided navigation, and using signals of opportunity,” Lund says. “All of this is aimed at allowing our customers to continue to operate without any degradation in performance – even if GNSS signals aren’t available.”
Next generation position, navigation, and timing (PNT) technology that will be less vulnerable to cyber attack is scheduled to reach operational assessment early next year, according to Maj. Gen. Wilson Shoffner, Director of Operations at the Army Rapid Capabilities Office (RCO), speaking at the 16th Annual AFCEA Army IT Day, hosted by the Northern Virginia chapter of the Armed Forces Communications and Electronics Association (AFCEA).
Threat of Navigation Warfare
Deliberate intention jamming is increasingly becoming routine operation that is being increasingly used against adversaries for disruption and deception and in coordination with other kinetic capabilities during conflicts. Russia in Ukraine and recently in Syria, has demonstrated supreme electronic warfare capabilities. Whenever drones have flown into southeastern part of Ukraine on-the-ground Russian troops have jammed them into virtual blindness. Organization for Security and Cooperation in Europe has kept reporting that every single drone that has been observing the conflict in eastern Ukraine, has been “subjected to military grade GPS jamming.”
Repeated jamming against GPS, allegedly from North Korea, was also experienced in South Korea between August 2010 and May 2013 when many ships and aircraft reported disruptions to the received GPS signal.
Apart from jamming by adversaries, GPS signals are also subject GPS-spoofing attacks whereby a malicious entity generates a GPS-like signal designed to mislead GPS receivers. This is normally done through rebroadcast or by signal generation. However, spoofing is harder to achieve than jamming. Authorized users can take advantage of US controlled encrypted GPS signals like SAASM [selective-availability anti-spoofing module] or M-Code.
Another way to make a spoofer’s job more difficult is to “combine more than one frequency with possibly more than one constellation, and ,” Peter Soar, business development manager for military and defense for NovAtel in Calgary, Albertaadvises. “Or you can add a tightly coupled inertial navigation system, which can’t be spoofed.”
A common misconception, however, is that a secure military GPS receiver is immune to jamming. “It’s easy to jam even the encrypted signal,” says John Fischer, chief technical officer for Spectracom in Rochester, New Yorkhe . “Signals from satellites are so weak that even a one-watt to 10-watt jammer can deny GPS coverage for a large area of both military and civilian signals.”
The U.S. military is in the midst of transitioning from the current SAASM technology to a newer encryption technology known as M-code. “This offers a few measures to be more jam resistant, but with high jammer-to-signal ratios so easy to implement by the enemy, M-code won’t alleviate the problem with jamming,” Fischer says.
The ever-growing importance of the electromagnetic spectrum has led the Pentagon to update its electronic warfare policy, calling for Electronic Warfare to be incorporated into the full range of military capabilities, including NAVWAR. With threats to PNT and cyberspace, forces might have to revert to more primitive technologies when denied. Reynolds said she was encouraged when recently visiting Okinawa, Japan, for the III Marine Expeditionary Force exercise, as some in the division were using maps and single-channel radios.
“They know how to do that, and we used to do that all the time, and so bringing back those old skills and know that if all else fails,” Marines can use a single-channel radio, she said. Similarly, Rear Adm. Dannell Barrett, director of Navy Cyber Security Division with the Office of the Chief of Naval Operations, said during the conference that one of the skills being taught at the Naval Academy is celestial navigation so that sailors don’t rely on a computer if communications or GPS are denied.
To address this problem, several DARPA programs are exploring innovative technologies and approaches that could eventually provide reliable, highly accurate PNT capabilities when GPS capabilities are degraded or unavailable. DARPA’s current PNT portfolio includes five programs, focused wholly or in part on PNT-related technology.
Canada’s Navigation Warfare program
The Navigation Warfare program, or NAVWAR, at Defence Research and Development Canada (DRDC) seeks to protect and exploit navigational capabilities through research on all three constituents of Electronic Warfare: Electronic Attack (EA), Electronic Protection (EP) and Electronic Support (ES). Electronic support concerns jamming detection, direction finding, and geo-location.
Electronic protection concerns the augmentation of existing equipment to preserve navigational capability in challenging environments. Some of the technologies are smart antennas, such as GAJT, that are capable of reducing or stopping the effectiveness of jammers. Controlled Reception Pattern Antenna (CRPA) anti-jam systems dynamically change the apparent antenna gain pattern to create nulls in the direction of interference signals. This shift effectively reduces the level of interfering signal imparted on the GNSS receiver electronics.
Another is the integration of GPS with complementary technologies such as chip-scale atomic clocks and small inertial measurement units of the Micro-Electro Mechanical Systems (MEMS). Inertial sensors at present lack the long-term stability of GNSS, but they are immune to jamming and spoofing since they do not rely on radio frequency signals. Such integration provides for more robust performance through sensor data fusion.
A DRDC prototype called MiPN (or Minimal Personal Navigator) integrates a number of sensors located on the body of a soldier. For instance, a GPS antenna on a helmet and an inertial sensor located in a boot can provide useable navigation data to a soldier in real time when GPS is not available.
NovAtel’s GAJT® – GPS Anti-Jam Technology
NovAtel’s approach to the problem is to build a range of compact and affordable anti-jam systems for land, sea, air (including unmanned aerial systems), and fixed installations. GAJT is a null-forming system that preserves the antenna’s view of the GPS satellites while ignoring jammers, ensuring the satellite signals required to compute precise position remain available.
The GAJT range of products provides anti-jam performance at a significantly lower cost than others and is available off-the-shelf for rapid deployment. GAJT works with any installed GPS receiver and is ready for M-Code.
The nominal performance of GAJT is 40 dB of interference suppression. Of course, the performance is scenario-dependent but this means effectively that you can operate safely 100 times close to a jammer than without protection. The whole system performance is the sum of GAJT interference suppression plus that provided by the installed receiver itself.
UK’s eLoran (enhanced Long Range Navigation) for ships and aircrafts
The General Lighthouse Authorities (GLAs) of the UK and Ireland have employed eLoran (enhanced Long Range Navigation), that enables ships and aircraft to determine their position and speed by triangulating low-frequency radio beacon signals transmitted by presently seven differential reference stations on the shore. U.K. has become first country to provide alternative position, navigation, and timing (PNT) information to ships fitted with eLoran receivers that can ensure their safe navigation in the event of GPS failure.
Captain Ian McNaught, deputy master of Trinity House, commented, “eLoran provides a signal around 1 million times more powerful than those from satellite signals, providing resilience from interference and attack.”
eLoran can provide navigation information for vessels as well as the timing data necessary to maintain the power grid, cell phones, financial networks, and the Internet in the event of an outage. Unlike space-based navigation, eLoran signals can also reach inside buildings, underground, and underwater.
Dismounted close combat sensors (DCCS) system for troops
The UK’s Defence Science and Technology Laboratory, together with industry partners Roke Manor Research, QinetiQ and Systems Engineering and Assessment, has developed dismounted close combat sensors which enable GPS-free navigation, automatic threat detection and information sharing for frontline troops.
This wearable sensor system enables navigation even when GPS signals are not available, by using inertial and visual navigation sensors. It considers last known GPS locations and integrates information from visually tracked features captured by a helmet camera and inertial sensors. The DCCS accurately tracks the location of an individual within buildings and tunnels, Dstl said in a statement.
The system has a combination of camera, laser and orientation sensors mounted on the personal weapon. Its acoustic and camera technology automatically identifies where enemy weapons are being fired from and this information is transmitted to the wearer and to commanders. DCCS is expected to enter service in the 2020s.
This integrated visual navigation system is then integrated with high-quality GPS and algorithms developed to understand when GPS can or cannot be trusted and to smoothly transition between the navigation systems when it is most appropriate to do so. “It works by providing a number of different navigation options, then carefully selecting the most trustworthy component at any particular time. There is a need to measure the sensor output but also to carefully monitor the noise and errors with each sensor and fuse the output accordingly.”
US Navy’s Assured Positioning, Navigation and Timing (A-PNT) Navigation Suite
The US Navy has asked industry to submit ideas, products and potential solution for a new Assured Positioning, Navigation and Timing (A-PNT) Navigation Suite to navigate in a GPS denied environment. Terry Halvorsen, the Department of Defense’s chief information officer, recently told Inside GNSS that the Pentagon intended to invest $5 million in research on eLoran receivers in fiscal year 2016. But eLoran, as a terrestrial system that depends on precisely situated signal towers, is unlikely to be able to meet all the Navy’s needs.
Northrop Grumman has received a contract from the US Navy to develop replacement inertial navigation systems (INS-R), which are installed on combat and support ships. The INS-R is designed to support the new navy assured positioning navigation and timing (A-PNT) architecture. The A-PNT is expected to provide increased navigation accuracy for the US Navy in challenging maritime combat environments.
“The INS-R will be the foundation of the assured position, navigation and timing suite for virtually all navy ships.” Under the contract, Northrop will develop fibre-optic gyro sensor at its facilities. The firm will also integrate the sensor into the inertial measuring unit, and will incorporate the navigation algorithms at its facility in Charlottesville, Virginia, U
U.S. Navy shipboard unmanned aviation experts needed navigation and landing capability for unmanned aerial vehicles (UAVs) in areas where RF and GPS signals are jammed or disrupted. ADSYS Controls Inc. is working with the Naval Air Systems Command at Patuxent River Naval Air Station, Md., to develop the Laser-Aided Recovery System (LARS) for precision 3D navigation and landing capability for ships and land sites where RF jamming is in effect.
US Navy is looking towards celestial navigation as a potential source, magnetometry and other signals of opportunity. The Naval Academy has reinstated celestial navigation (CELNAV) classroom instruction because of growing threat of hacking of the navigation systems on a Navy ship.
US Army’s Assured PNT program.
The US Army recently completed an extensive laboratory test of Global Positioning System (GPS) Anti-Jam antenna capabilities, a key step toward enabling Soldiers to maneuver safely on the battlefield. Ten antenna systems were assessed on their ability to receive GPS satellite signals in contested environments to accurately determine a platform’s PNT. The antennas were tested in two configurations: stand alone on a ground plane and mounted on a Stryker vehicle.
The anti-jam capability is just one of the solutions under development within PM PNT. Assured PNT has four subprograms geared toward the development of systems to achieve the required PNT capability. A-PNT is a system of systems solution designed to complement each other. In addition to anti-jam antennas, A-PNT consists of pseudolites, which will provide PNT data to users when GPS satellite signals are distorted or unavailable; dismounted PNT, a scalable and upgradable GPS receiver that will send secure PNT data to the Soldier; and mounted PNT, a scalable and upgradable PNT system for mounting within a platform.
The A-PNT program focuses on platform distribution of PNT, scalable PNT architectures that outpace the threat, and the ability to upgrade to future technologies, including Military Code (M-Code). M-Code is expected to further improve anti-jamming capabilities and secure access of Military GPS signals.
The Assured PNT approach doesn’t just involve material solutions such as hardware and software, but also requires that the Army’s architecture, training, testing and operational concepts evolve, said MAJ Christopher Brown, assistant program manager Dismounted PNT within the Assured PNT program
Dismounted Position and Navigation Sensor (DPNS)
Raytheon UK unveiled a newly developed Dismounted Position and Navigation Sensor (DPNS) designed for dismounted operators at DSEI 2017 in London. Development of DPNS follows a requirement to continuously track soldiers operating in
environments that have a complete absence of GPS signals, including tunnels systems, caves, built-up areas, and environments subject to GPS denial or spoofing.
DPNS uses a puck configuration that currently mounts to the boot of the user using a specially designed fixing .The DPNS is transparent to the user, requiring no user input or control and features a GNSS/MIL GPS location engine combined with a built-in barometer that provides location information in full GPS-denied environments. The device includes Bluetooth connectivity used to interface with the chosen bearer system. The DPNS output tracks enable blue force tracking to increase situational awareness, and the system has a built-in haptic feedback capability that is used to provide tangible feedback to the user.
Pseudolites provide high-powered signals
Pseudolites are ground and airborne GPS satellite-like transmitters whose signals have many of the characteristics of the L1 signals broadcast by the satellites in the GPS system but having higher power. They use a carrier that is near L1, and a randomizing code that is similar to the C/A code used by the GPS system.
The transmitter consists of various components, such as a GPS anti-jam receive antenna, inertial navigation unit, a signal generator, power amplifier and a transmit antenna. A legacy GPS receiver would only require a software upgrade to receive the pseudolite signal. No other hardware items need to be purchased for a legacy GPS receiver to receive and process the signal.
Area protection can be provided through the deployment of pseudolite transmitters supporting a brigade combat team area of operations, he noted. The Pseudolite subprogram enables continued operations of PNT-enabled systems, such as Blue Force Tracking, communications networks, and precision-guided munitions, Kevin Coggins, program manager for PNT said.
The Army Communications-Electronics, Research, Development and Engineering Center (CERDEC) has previously developed and proven the effectiveness of pseudolites and the receiver software upgrade at the White Sands Missile Range I June 2015.
The pseudolites have completed feasibility testing and entered acquisition for transmitters, receivers and command-and-control. Rockwell International and L-3 are developing the transmitters. The effort seeks to use current military GPS receivers with software modified to accept pseudolite signals.
Harris Corp. is also involved in pseudolite-related PNT development. Harris worked with an unmanned aerial vehicle provider to develop an all-digital payload that was successfully flight tested in a UAV.
Ongoing SoSA work
The framework based on System of Systems Architecture (SoSA), including the PNT Hub, under development within the Assured PNT program, will enable the integration of innovative technologies such as the Chip Scale Atomic Clock, which harnesses the stable oscillations of the cesium atom to preserve precise time, even in the absence of GPS.
Engineers with innovative approaches to determine positioning and timing will have an affordable pathway to insert this technology into a PNT SoSA-compliant product.
“PNT Hub is a potential product of the Mounted PNT subprogram,” Kevin Coggins, program manager for PNT said. “Research and development activities are being conducted; however, there is no specific contract award or deliverables yet. The future Mounted PNT solution will incorporate PNT SoSA attributes and complement the Army’s Enterprise approach to PNT.”
DARPA’s PNT programs
“Position, navigation, and timing are as essential as oxygen for our military operators,” said DARPA Director Arati Prabhakar. “Now we are putting new physics, new devices, and new algorithms on the job so our people and our systems can break free of their reliance on GPS.”
DARPA is giving thrust to five PNT programs:
Adaptable Navigation Systems (ANS) seeks to provide GPS-quality PNT to military users regardless of the operational environment .
Precision Inertial Navigation Systems (PINS) is an effort to address the vulnerabilities of GPS navigation — jamming, spoofing, blind spots, etc. — by using ultra-cold atom interferometers to reduce the positional accuracy drift of inertial navigation system (INS) by several magnitudes to achieve near-GPS accuracies. Such a system could be used as a backup in case of GPS denial, or as an alternative to GPS on some platforms.
Additionally, ANS seeks to exploit non-navigational electromagnetic signals–including commercial satellite, radio and television signals and even lightning strikes–to provide additional points of reference for PNT. In combination, these various sources are much more abundant and have stronger signals than GPS, and so could provide position information in both GPS-denied and GPS-degraded environments.
Microtechnology for Positioning, Navigation, and Timing (Micro-PNT) leverages extreme miniaturization made possible by DARPA-developed micro-electromechanical systems (MEMS) technology. Micro-PNT comprises a portfolio of diverse efforts collectively devoted to develop highly stable and precise chip-scale gyroscopes, clocks and complete integrated timing and inertial measurement devices. DARPA researchers have fabricated a prototype with three gyroscopes, three accelerometers and a highly accurate master clock on a small penny sized chip.
Quantum-Assisted Sensing and Readout (QuASAR) intends to make the world’s most accurate atomic clocks—which currently reside in laboratories—both robust and portable. QuASAR researchers have developed optical atomic clocks in laboratories with a timing error of less than 1 second in 5 billion years. Making clocks this precise portable could improve upon existing military systems such as GPS, and potentially enable entirely new radar, LIDAR and metrology applications.
The Program in Ultrafast Laser Science and Engineering (PULSE) applies the latest in pulsed laser technology to significantly improve the precision and size of atomic clocks and microwave sources, enabling more accurate time and frequency synchronization over large distances. These capabilities are essential to fully leverage super-accurate atomic clocks, as clocks such as those that QuASAR seeks to build are more precise than our current ability to synchronize between them. If successful, PULSE technology could enable global distribution of time precise enough to take advantage of the world’s most accurate optical atomic clocks.
The Spatial, Temporal and Orientation Information in Contested Environments (STOIC) program seeks to develop PNT systems that provide GPS-independent PNT with GPS-level timing in a contested environment. STOIC comprises three primary elements that when integrated have the potential to provide global PNT independent of GPS: long-range robust reference signals, ultra-stable tactical clocks, and multifunctional systems that provide PNT information between multiples users.
Additionally, DARPA recently announced a new program related to PNT called “Precise Robust Inertial Guidance for Munitions: Navigation-Grade Inertial Measurement Unit.” This PRIGM program addresses the challenge of providing precise PNT for low-cost, -size, -weight and -power consumption platforms, such as smart bombs and guided munitions, in GPS-denied environment.
for more information on DARPA’s GPS denied and beyond technologies:http://idstch.com/home5/international-defence-security-and-technology/technology/ict/darpa-developing-gps-backup-and-beyond-technologies-for-contested-environments/