A sense of direction: Striving to maintain GPS

Transcription

1 A sense of direction: Striving to maintain GPS [Content preview Subscribe to Jane s Defence Weekly for full article] The Global Positioning System, or GPS, is one of the most pervasive technologies in use today. Anything that navigates the land, skies, or seas relies on GPS for position and timing. However, concerns over the ability of adversaries to disrupt or fake a GPS signal mean that militaries are working to harden the signals and receiver hardware while also seeking out alternative methods of navigating without GPS. Geoff Fein explores the efforts being made to ensure that the global navigation system remains reliable and usable Challenges to the Global Positioning System (GPS) are becoming more sophisticated, including the ability of adversaries to disrupt, jam, and spoof its signals. As one industry official told Jane s, GPS jamming is becoming more and more prevalent. Just last month there was a report that vessels operating in the Black Sea were receiving erroneous GPS fixes. No cause was identified, but the affected ships had to react when they realised their navigation and timing information was wrong, explained John Liebetreu, chief engineer of space electronics and communications for General Dynamics Mission Systems. A GLONASS-M navigation satellite during assembly and testing by ISS Reshetnev. GLONASS is Russia's own satellite navigation system. (ISS Reshetnev) When GPS was launched 30 to 40 years ago the US Department of Defense (DoD) did not think that military services would be operating in an environment where the signal could be challenged. Page 1 of 11

2 While the United States and its allies acknowledge that the threat to GPS is real, few will elaborate on how those threats might be carried out or how they can be repelled. However, many officials are confident that jamming and spoofing of the GPS signal can be dealt with. The Glonass-K navigation satellite is based on the Express 1000 bus developed by ISS Reshetnev. (ISS Reshetnev) Although there have been instances of GPS signal disruption, the system continues to operate, providing navigation and timing around the world, said Jean-Philippe Saulay, staff officer for identification (ID) and navigation with the NATO Headquarters consultation, command, and control (C3) staff, who is also vice-chair of the alliance's C3 board navigation and ID panel. The system is up and running 24/7 and provides quite some performance, Saulay said. The jamming and spoofing issues can be dealt with [using] mitigation measures, to some extent of course, he added. The BeiDou navigation satellite is the Chinese alternative to GPS. (CAST) Still, government researchers spend their days trying to think of all the different scenarios that forces could encounter in potential anti-access/area denial (A2/AD) environments, noted Dr Scott Page 2 of 11

3 McLelland, group leader for navigation warfare at the Defence Research and Development Canada (DRDC) centre in Ottawa. While militaries work to enhance, harden, and improve the resiliency of GPS, few if any officials believe that it will be replaced, but that has not stopped countries from pursuing their own satellitebased navigation capability. Russia has its own satellite navigation system Globalnaya Navigazionnaya Sputnikovaya Sistema, or the Global Navigation Satellite System (GLONASS) while the Chinese have BeiDou and the Europeans have Galileo. A model of a Beidou satellite donated by the People's Republic of China to the United Nations Office for Outer Space Affairs. (UN-SPIDER) We are tracking the impacts of all the other systems that are going to be coming online, McLelland said. That is the nearest-term thing that might impact people's use of GPS, even though it is [a] satellite navigation [system]. Developing technologies We need technologies to complement GPS, to provide positioning during the loss of the GPS signal, and to help regain it when possible, Paul M Olson, chief engineer of the US Army s Communications-Electronics Research, Development, and Engineering Center s (CERDEC s) PNT division, told Jane s. CERDEC is one of several US military agencies dedicated to finding ways to repel an adversary s efforts to deny US and allied forces the ability to operate. Technologies such as vision-aided navigation and radio frequency (RF) ranging are close to being fielded, Olson noted. To complete the navigation system suite we are integrating them with other PNT system elements including a GPS, an inertial measurement unit [IMU], an odometer [in vehicles] or a dead reckoning module [for dismounted soldiers], and a chip-scale atomic clock [CSAC] for maintaining time accuracy, he said. Our vision-aided navigation algorithms are of a variety known as visual Page 3 of 11

4 odometry, in which the algorithm detects features in one image and then finds the [same] features in the next image. This enables the algorithm to determine the platform velocity and rotation, which can then be used to correct errors in the IMU, he continued. CERDEC s RF ranging devices measure the distance between two platforms by estimating the flight time of an RF beam between two devices. Very soon we will be demonstrating a vision-aided navigation system that is integrated on a military vehicle and providing position inputs to a blue force tracking system, Olson added. For the last three years CERDEC has been conducting a hardware/software (HW/SW) convergence programme where several C4ISR functions PNT; intelligence, surveillance, and reconnaissance (ISR); communications; radar; electronic warfare; and mission command have been combined into a single chassis. Additional sensors can be easily added, either on a circuit card inside the chassis or externally as appropriate, with integration consisting of updated software on the card, Olson said. The PNT function of the current demonstrator includes GPS and CSAC as a back-up source for precise time if GPS is unavailable. A future vision for the HW/SW convergence system is that all the functions would be integrated to provide synergistic capabilities, he noted. In the case of a positioning capability in the absence of GPS, the ISR function could support a vision-aided navigation function, the radar could serve to provide RF ranges, and the communication system may take on signals of opportunities [SoOPs] and time transfer roles. The open-architecture approach of this effort provides tremendous flexibility and upgrade potential. Looking forward, CERDEC is developing and monitoring several technologies that will provide improvements such as advances in inertial navigation, specifically micro-electromechanical system (MEMS) IMUs, which are rapidly approaching navigation grade in a very small size, Olson said. We are very closely examining the use of several sources of global navigation satellite systems [GNSS], which provide frequency diversity and more sources of signals. SoOPs exploit transmissions not originally intended for navigation, such as AM, FM, and television [TV]. Then the ranges to the towers are estimated and the locations are determined via triangulation, he explained. Advancements in the use of magnetometer data to compensate for IMU errors have demonstrated impressive results for dismounted and mounted applications. Future advances in optics are expected to enable celestial navigation for use in battlefield conditions, even during daytime and smoke-obscured conditions, Olson added. We are working with the other services to develop sensors and fusion filters for rapid plug-andplay, using open-system architecture [OSA] methodologies. The OSA approach will enable us to be especially versatile and able to react to the ever-changing battlefield conditions and environments, Olson said. PNT is also a key mission area for the US Air Force Research Laboratory (AFRL), Neeraj Pujara, AFRL PNT acting lead, told Jane s. The AFRL has three major lines of effort. The first is looking at navigational alternatives where researchers are trying to develop navigation technologies to ensure the availability of PNT. Second, the AFRL researchers have a robust satellite navigation area where they are trying to Page 4 of 11

5 augment and strengthen the resilience of GPS with space-based and user equipment technologies. The third effort is looking at an integrated PNT. Currently in the lab there are efforts to make use of improved sensors and better algorithms and to increase the mission effectiveness of systems similar to terrain contour matching (TERCOM) and digital scene matching area correlator systems (DSMACs), celestial navigation (CelestNav), and tactical air navigation systems (TACANS). The US DoD's PNT science and technology roadmap is exploring alternative or complementary PNT techniques such as CelestNav, correlation navigation, sensor fusion, SoOP, better IMUs, better timing via clocks and time dissemination, and active infrastructure such as beacons, RF, or networks. Some examples of correlation navigation include vision-aided navigation, gravity, magnetics, pressure, image matching, navigation using the Earth's magnetic field, and anomaly maps, Pujara noted. Within the AFRL, PNT research and development is being done across multiple sites and directorates, including the space vehicle directorate at Kirtland Air Force Base (AFB) in New Mexico, the munitions directorate at Eglin AFB in Florida, and the sensors directorate at Wright- Patterson AFB in Ohio. The Navigation Technology Satellite-3 (NTS-3) programme, managed by the AFRL s Space Vehicles Directorate, will be a testbed for advanced techniques and technologies to detect and mitigate interference to GPS, increasing satellite navigation (SATNAV) system resiliency for military, civilian, and commercial users, according to the AFRL. Capabilities planned for NTS-3 include atomic clocks, antennas, reprogrammable digital waveform generators, new signals, automation, use of commercial assets, cyber security, and softwaredefined user equipment. Technology matured and knowledge gained from NTS-3 are expected to transition to future generations of GPS and potential augmentations to the GPS constellation. One challenge is the transition to these alternative PNT technologies because they must be tailored for the mission plus the platform and environment. Today's PNT architectures are not designed to allow for this tailoring, Pujara noted. One of the AFRL s key programmes is called the Resilient Embedded Global Positioning/Inertial Navigation System (REGI). The goal of the initiative is to rapidly and iteratively prototype opensystem processes and open-standard PNT technologies that deliver robust evidence to prove that this open approach can affordably improve PNT capability for the USAF. The REGI programme is a joint effort with the USAF Lifecycle Management Center, he added. In terms of our near term, from a sensors directorate perspective, we are investing in lower-power and higher-performance anti-jam techniques to increase the robustness of GPS and to increase [the] situational awareness of potential jamming environments, Pujara continued. Page 5 of 11

6 The AFRL is also working to develop GNSS technologies and GPS electronic warfare (EW) training devices. The 2015 Department of Defense Space, Science, and Technology (S&T) strategy document roadmap provides a comprehensive summary of DoD-sponsored 6.2 and 6.3 research activities, Pujara said, adding that work is currently underway on the 2017 PNT S&T roadmap. One thing that came out of the 2015 roadmap, Pujara noted, is that it recommended areas for increased focus and areas in which to facilitate the development and insertion of complementary PNT technologies. That led to the undertaking of three initiatives. The first is PNT Open Architecture (OA), where the services can effectively 'plug and play' with additional capability. Led by Pujara, the effort seeks to take advantage of sensors already on board a platform to help you in your PNT solution, he said, adding, We are looking at any sensor where data is available. We are developing the OA, a government PNT reference architecture, to be able to take advantage of any sensor. We are just getting started in this area. It is also hoped that having a modular capability will enable the services to avoid repeating integration costs, he added. The US Army, meanwhile, is leading a modelling and simulation effort, while the US Navy is leading the third initiative, focused on timing. [The] AFRL has been working in the area of alternative navigation technologies for quite some time, more than 10 years. It is getting to the point [where] we are seeing some fruits to our labours, Pujara explained. There is viability in some of the alternative navigation technologies that we and the other services are working on. The DRDC s McLelland leads the Canadian S&T agency s navigation warfare effort to preserve GPS in as many different circumstances as can be imagined. Our concern and our research are understanding what those impacts in those environments could be, in our case military receivers... military systems that are dependent on GPS, and then come up with S&T to preserve GPS in those circumstances, McLelland added. Size matters One challenge for McLelland is the physical limitations of the antennas themselves: how big they are. Their size impacts their performance, but then there is the software that goes inside... our firmware that does the signal processing to remove the jamming, he said. There is a lot of work being done in the academic world and has been for many years on the signal processing software, or firmware, or techniques to better remove different kinds of interferers or jammers. While there are numerous antennas that can be fitted onto a large platform like a frigate or destroyer, that same antenna will not fit on an unmanned aerial vehicle (UAV). What we saw in the beginning with anti-jam antennas, like with almost every other piece of technology I can imagine, is that the first thing that comes out tends to be kind of big... everything tends to be big at the beginning and they tend to be expensive, McLelland said. Page 6 of 11

7 So you may decide you need to make that hardware fit on a much smaller platform and that is going to change the overall performance and there is going to be a lot of R&D [research and development] there, he added. Soon, cheaper anti-jam antennas suitable for a land vehicle came along. The Department of National Defence (DND) in Canada sponsored NovAtel to build a land variant of an anti-jam solution known as the GPS Anti-Jam Technology (GAJT) antenna, McLelland said. The NovAtel GAJT GPS anti-jam antenna, seen here installed on a LAV III 8x8 armoured personnel carrier. (DAGR) At the time when it was released it was the first, if not the only, GPS anti-jam antenna that was at a cost and size and targeted to land vehicles. There are many others now, but the existing solutions at the time, three to four years ago, were too cost prohibitive or too big for land vehicles, he explained. Still, as good as NovAtel s GAJT is, it was too big for a UAV, McLelland noted. They now have something called GAJT AE: a smaller two-piece solution where the antenna is separate and the electronics can go somewhere else connected by cables, he added. According to NovAtel, GAJT-AE-N is designed for size- and weight-constrained applications, such as small airborne and unmanned ground platforms, where it is preferable to mount the antenna electronics inside the vehicle. Page 7 of 11

8 The size and configurations of anti-jam antennas continue to evolve as the different commercial vendors look to meet the different needs of customers, McLelland said. Platform architecture & software resiliency Industry is also undertaking efforts to not only provide enhanced and hardened receivers, but to ensure that the platforms and systems that they provide to the military will function in a GPSdenied environment. Northrop Grumman, for example, is developing the preliminary hardware and software architecture design for the USAF s Embedded GPS/Inertial Navigation System - Modernisation (EGI-M) technology, Charles Volk, director of Advanced Technologies and Products for Northrop Grumman, told Jane s. Based upon modular, open-systems architecture, EGI-M will support rapid insertion of new capabilities to enable robust, accurate, and reliable positioning, navigation, and timing information, even in GPS-denied conditions, Volk said. The modernised, next-generation navigation system is expected to be available for platform integration starting in There are a number of initiatives striving to improve the performance of inertial sensing, Volk noted. These range from self-calibrating sensors to atom interferometry, which may in some situations provide near-gps performance for the duration of the mission. There are also government initiatives that are seeking to improve the inherent stability of atomic clocks, again to provide sufficient accuracy to accomplish the mission, he explained. Al Simon, business development manager for weapons products at Rockwell Collins, said that there has been a noticeable uptick in the need for anti-jam and GPS resiliency. Everybody is focused on strengthening [GPS] as much as they can, yet provisioning for it if for some reason it is not available, he said. That conversation, depending on the customer, user, or platform, becomes kind of a platform-centric conversation 'What are the redundant systems that you need or the redundant mission concept of operations that you need to operate to in case GPS is not there?' and it is different for everybody. Rockwell Collins is involved in an army effort that could provide GPS in the event that GPS systems go offline, said Dan Stearns, the company's business development manager for airborne navigation products. The US Army s PseudoLites programme would use a manned aircraft or UAV to fly outside the reach of an enemy s interference to broadcast a GPS signal to ground troops, other aircraft, or ships operating in theatre. BAE Systems has been looking at techniques and technologies that are going to allow its weapon systems to continue to operate in a contested environment, Dave Harrold, BAE's director of business development for survivability, targeting, and sensing solutions, told Jane s. All of our GPS capabilities from a US perspective are using the SAASM [Selective Availability Anti-Spoofing Module] GPS, which has some level of anti-spoofing in [it], he said. Page 8 of 11

9 Harrold said there is a growing need in a contested environment to have a robust capability, both on the targeting side and on the seeker or guidance side on a munition, because without a reliable GPS capability to deliver the munition to its target, a weapon might need imaging infrared (IR), RF, or millimetre wave capabilities, which are done in combination. Raytheon has taken that approach with its Small Diameter Bomb (SDB) II, which has wedded GPS with an IMU to navigate the weapon to target. Raytheon's precision-guided Small Diameter Bomb II, which has wedded GPS with an IMU to navigate the weapon to target. (Raytheon) If you talk to the engineering people they will tell you GPS is very accurate but very noisy. If you plot it out it looks like an electrocardiogram [ECG], Mike Heyser, senior manager for business development within Raytheon s SDB II programme, told Jane s. IMUs are very smooth but they tend to drift over time, Heyser said, but if you blend [GPS and IMU] together you get the best of both; you get a smooth line and the accuracy of GPS. The US Air Force (USAF) faces a daunting challenge because it must ensure that its aircraft and weapon systems can operate in a GPS-denied environment while also protecting the GPS and communications satellites, which face a continuum of threats, including physical and cyber attacks, as well as signal jamming and spoofing, Colonel Steven Whitney, director of the USAF Space and Missile Systems Center s Global Positioning System Directorate, told Jane s. Although the colonel could not discuss specifics on the types or number of attacks, he noted that the USAF has active systems to monitor and deter activities that may become a threat to the systems in its defensive space control network. The GPS constellation is healthy and our 31 operational satellites will continue to provide a navigation signal around the world to meet military and civilian requirements. As part of GPS modernisation the GPS next-generation Operational Control System [OCX] will provide improved cyber-security protection ensuring that GPS remains postured to operate through cyber-attacks, Col Whitney explained. The GPS III satellites will provide a new M-Code [Military-Code] signal Page 9 of 11

10 with greater security and higher power with comparable availability and accuracy improvements to further add capabilities to the 19 M-Code satellites on orbit today. The new M-Code is designed to allow military receivers to operate closer to jammers and under trees, enhancing their ability to track the GPS satellites, support a more secure and flexible cryptography architecture, and detect and reject false signals, Col Whitney noted. Ensuring that the GPS satellite system remains functional is not just limited to the military. GPS is considered to be a shared national asset and its operation is critical not only to the United States, but internationally. As such, protecting it is one of the USAF s top priorities. The GPS III programme provides navigation and timing to a broad spectrum of civil users, which will include the three civil signals (L1C/A, L2C, and L5) flown on previous satellites, he added. It will also transmit a new fourth civil signal, L1C, which is compatible with the European Galileo satellite navigation system signal. L1C is additionally compatible with those signals planned for broadcast on Japan's Quazi-Zenith Satellite System (QZSS): a system meant to augment GPS services, Col Whitney said. A European Galileo satellite. A common civil positioning signal will be jointly broadcast by up to 60 satellites from both GPS and Galileo constellations, further increasing the accuracy and availability of user PNT solutions. (European Space Agency) Once implemented, the common civil signal will be jointly broadcast by up to 60 satellites from both GPS and Galileo constellations, further increasing the accuracy and availability of user PNT solutions, he added. Page 10 of 11

11 Inevitably, the growth of GPS and other space-based systems makes them targets for adversaries. While the AFRL, for example, is researching ways to assure PNT, Col Whitney noted that exploring GPS alternatives is not within the scope of the GPS programme office. He added that the GPS Directorate has been working on efforts that mature multi-gnss receiver concepts, advance antenna designs for higher performance in contested environments, and field nextgeneration navigation signals to combat the jammer threat. For the full version and more content: Jane's Defence Industry and Markets Intelligence Centre This analysis is taken from Jane s Defence Industry & Markets Intelligence Centre, which provides world-leading analysis of commercial, industrial and technological defence developments, budget and programme forecasts, and insight into new and emerging defence markets around the world. Jane s defence industry and markets news and analysis is also available within Jane s Defence Weekly. To learn more and to subscribe to Jane s Defence Weekly online, offline or print visit For advertising solutions visit Jane s Advertising Page 11 of 11