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If not GNSS, then what?

An interesting question.

To some, it means GNSS is so important and unique that without it, all is lost. They enthusiastically support only GNSS-centric research and development, believing that any issues that GNSS has today — such as lack of resilience — can be resolved given enough time and money. It includes pushing for the discontinuance of ground-based systems and the “re-purposing” of their resources to produce more satellites and more space-based signals. It demonstrates an admirable and true dedication to the belief that GNSS is the mission.

To others, these words have a different and darker meaning, warning of a clear and present danger. To them, it means “When (not if) GNSS is not available, what other source(s) of positioning, navigation and timing services (PNT) will be available to support GNSS users’ missions and goals?” For these purpose-driven individuals, GNSS is a means — not the mission, which is to provide the necessary positioning, navigation and/or timing performance, such as accuracy, availability, integrity, continuity and coverage, required to ensure the nation’s safety, security and economic well-being.

Unfortunately, some who have made GNSS their mission strive to convince others that it should be their mission, too!

GNSS is magic — but only when it works. It has played and will continue to play a crucial part in advancing our knowledge and abilities and supporting diverse use cases worldwide. It should and must be supported, but not to the exclusion of everything else. Recently, the magic has failed numerous times all around the world and, as a PNT community of suppliers and users, we must know we are capable of so much more.

We also know that the vast majority of civil PNT service needs are local, not global — based in part on the population density of users and their use cases. Over the years, GNSS’ accuracy and coverage have spoiled us. We even chose to see GNSS interference events as proverbial “black swans.” At the same time, the abandoning of well-engineered, resilient local solutions in favor of a global, one-size-fits-all mentality has been appealing to many. We know this approach is fraught with danger. Throwing away perfectly acceptable, resilient local means rather than enhancing them and bringing their technology into the 21st century may, as a PNT community, be our biggest regret. In many ways we have already gone too far.

I encourage our PNT community to commit to doing more, to open up our minds to design, develop, evolve, create, install, implement and operate more resilient PNT sources and more resilient user systems for which PNT services are critical inputs — especially by focusing on services that are not space-based, operate in different areas of the spectrum, are capable of higher power, and can be installed and evolved more quickly to mitigate emerging new threats. Most importantly, we all need to accept and support the true mission of our PNT community, the “why” that drives our innovative solutions: to ensure PNT services always will be available to support our safety, security and economic well-being.

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GNSS are magic. They are. One dictionary defines magic as “a power that allows people (such as witches and wizards) to do impossible things by saying special words or performing special actions.” By this definition, we have all become witches and wizards, doing what previous generations would have deemed impossible.

This magic, however, can be affected by external forces that render it useless at best and, at worst, dangerous. Warnings about GNSS positioning, navigation and timing (PNT) service vulnerabilities have been raised for 25+ years. Numerous organizations have warned of the potential safety, security and economic impacts of GNSS interference. Still, like modern-day Cassandras, their warnings have been ignored, and sole use of PNT services that rely on space-based signals continues to expand.

“Magic services” are addictive and cannot be ignored. Yet, it is well past the time to merely admire the problem of GNSS interference — benefitting from magical GNSS services while ignoring existing and emerging threats and challenges. It is time to draw a line and implement resilient, complementary PNT solutions to support all critical infrastructure sectors and applications in the event of any GNSS disruption, due to jamming or spoofing or systemic causes. “Magic” is magical when it works. When it does not, first and foremost, it should “do no harm.” 

Threats, Challenges and Needs 

Presidential Policy Directive (PPD) 21, Critical Infrastructure Security and Resilience, issued in 2013, defines resilience as “the ability to prepare for and adapt to changing conditions and withstand and recover rapidly from disruptions.” It also notes that “resilience includes the ability to withstand and recover from deliberate attacks, accidents, or naturally occurring threats or incidents.”

In 2016, the UK Department of International Development noted that “Resilience covers both ‘physical and societal systems” through four “R” principles: robustness, redundancy, resourcefulness and rapidity (see Figure 1).

Figure 1. Infrastructure resilience properties. (Image: UK Department of International Development)

More recently, Andy Proctor (RethinkPNT) pointed out that “A resilient PNT system protects its critical capabilities (assets) from harm by using protective resilience techniques to passively resist or actively detect threats, respond to them, and recover from the harm they cause.” 

Policies, processes, financial arrangements and incentives are also crucial to achieving resilience — and that has been, and remains, the problem. Lacking the emergence of strong leadership from our institutions, the ability to achieve actual resilience will continue to falter and admiration of the problem will continue.

Developing a resilient PNT system is always a balance of technical complexity and non-technical aspects, for example, costs. The key consideration for users must be the required performance metrics they need for their use-case(s) to ensure their resilience — including accuracy, availability, integrity, continuity and coverage. The one least understood and many times omitted is integrity — the level of trust a user/use-case needs to safely and securely use the PNT services. The ability to trust PNT services must always be a consideration for critical infrastructure applications.

Unfortunately, many users of critical infrastructure PNT do not know some of the PNT metrics they need to ensure safety and security. More troubling, there is no guidance as to what constitutes “significant economic impact” (see PPD 21) or acceptable economic loss — and over what period or range of use cases. This understanding will require analysis of their design, development and operational experiences, and working with PNT systems engineers to first derive these metrics and then drive the continuous improvements (see Figure 2) needed to achieve and retain truly complementary PNT capabilities. Without clear metrics and guidance, one cannot claim that any solution will meet any “required level of resilience.”

Figure 2. Resilient PNT lifecycle.

Supporting PNT Users

As with all systems engineering (SE) activities, PNT system resilience begins with identifying and documenting user needs based on their specific user stories/use cases. Figure 3 depicts different aspects of resilience that can be sought, depending on the unique use-case “demands.”

Figure 3. Resilience aspects. (Photo: UK Space Agency)

While the resilience needs of different use cases will differ, for any specific use case, a given “PNT solution” will either achieve the required/threshold level of resilience (based on the operational environment) or it will not. Some use cases may also require fail-safe or fail-soft capability and the ability to recover to known, trusted and usable states. Shouldn’t many, if not all critical sector use cases require this?

Equally important is the identification of risks and threats, as they are critical to understanding the challenges that the system must face while continuing to provide the necessary P, N and/or T service performance. It is also key to understand and document the system architecture and environment in which it must perform. With knowledge of a user’s needs, the threats, hazards and challenges they face, and the system architecture, the SE process can develop an understanding of the “gaps” that exist and of the levels of risk they impose on a critical infrastructure system’s functional, physical and operational performance. Understanding this, essential use-appropriate mitigations can be identified, or if need be, developed, and a resilient, solution-agnostic PNT requirement document created.

The Way Forward

The Critical Infrastructure Resilience Institute (CIRI), a U.S. Department of Homeland Security Center of Excellence, notes that “critical infrastructure systems are facing a myriad of challenges. Solutions must address the cyber, physical and human dimensions.” They keyed into four areas where critical infrastructure resilience activities should be directed: building the business case, information policy and regulation, developing new tools and technologies, fostering and educating the workforce.

These include the recognition that “policy and regulation have a powerful impact on market forces.” While the fact that “most U.S. infrastructure is owned and operated by the private sector” is a challenge, it should not be an excuse.

We must start immediately to re-establish strong SE practices, policies, and principles to help critical users understand their needs and determine the metrics required to ensure safety and “preclude significant economic impact.” Only then can we understand from a national perspective, the needed safety and security metrics and what constitutes significant economic impact, and then establish categories of solution-agnostic requirements. Lacking these clear resilience targets, detailed planning, and required resource commitments, the growing threats of PNT vulnerability will continue only to be admired, rather than be mitigated. Hope is not a strategy, but this systems engineer hopes that it does not take a truly catastrophic event to finally prompt much needed and long overdue actions. 

Mitch Narins is the principal consultant/owner of Strategic Synergies LLC, a consultancy he formed following more than 40 years of U.S. government service. He is a Fellow of the Royal Institute of Navigation, a aenior member of the Institute of Electrical and Electronic Engineers, a member of the Institute of Navigation and head of its Washington, D.C., section, and a member of RTCA, RTCM, IEEE and SAE Standards Committees.

<p>The post Delivering security through systems engineering first appeared on GPS World.</p>

Mitch Narins, principal consultant & owner, Strategic Synergies LLC

Recently there have been conversations within the world’s position, navigation and timing communities regarding the use of the term “Gold Standard.” Many systems aspire to be a Gold Standard, but what does this mean and how should one rightfully claim this meritorious distinction? For me, to be called a Gold Standard, a system must meet a number of hard and soft performance requirements that instill users with trust and confidence. What are these performance metrics., and how should we measure them?

I propose that for a PNT system to be a Gold Standard, it must embody and embrace three basic operational aspects in its vision, mission and goals, which drive its design, development and operation:

Requirements. First, a PNT Gold Standard system must have clear, concise, published and independent operational requirements, established through recognized and appropriate standards — that is, the PNT “promises” of accuracy, availability, integrity, continuity and coverage provided by the system are available to all users, and any changes to these “performance requirements” are communicated and implemented in a formal and transparent process.

Monitoring. Next, a PNT Gold Standard must continuously monitor the system “health” to ensure that it is meeting all of its promised requirements (accuracy, availability, integrity, continuity and coverage). The measurements and monitoring information must be available to all users so they can, with confidence, independently verify performance in support of their missions and needs.

Transparency. Finally, and most importantly, a PNT Gold Standard must not only maintain transparency during normal operations, but at the most crucial times when the PNT system is not meeting its promised performance. When “things go wrong,” user communications and constant, continuous, and reliable information flows are essential to retaining trust (that is, the measure of the system operator’s integrity). “We don’t know what happened yet, but we will let you know as soon as we do” is acceptable; saying “no comment” is not. As soon as the cause of the problem is known, it must be promptly shared, in detail, along with the schedule for restoration of normal operations. All changes that will be implemented to preclude such an occurrence in the future and all lessons learned must also be communicated openly and honestly to users.

So, what is a PNT Gold Standard? It is a system that makes operational promises based on known and controlled standards and requirements and openly shares how performance against those promises is being monitored and assured. It is a system defined by mission, values, standards and operating principles that is committed to free and open communications when promised performance is being met and when it is not. It is a system that transparently documents, communicates, investigates and reports health and status to users without delay. It is a combination of known, measured and exceptional performance provided by a system operated with open, honest, inclusive, transparent and complete communications that evoke user trust. For me, that is what it means to be a PNT Gold Standard.

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Mitch Narins, principal consultant, Strategic Synergies, LLC

A: (1) Agree that “No electromagnetic spectrum use will be approved, now or in the future, that impacts GNSS PNT users.” – a common mission statement essential to establishing trust!

(2) Determine how best to migrate today’s GNSS PNT users to be more resilient to both interference and planned future adjacent band services.

(3) Provide detailed architectures, network layouts, and implementation plans for rollout of new adjacent band services compliant with (1) and supportive of (2).

John Fischer, VP, Advanced R&D, Orolia/Spectracom

A: We cannot ignore fielded legacy systems, but neither can we chain ourselves to old technology and hinder progress.

Spectrum usage cannot be solved by less regulation, but it can be with innovative regulatory ideas adhering to minimalist principles. For example, would a “cash for clunkers” program work to eliminate weak receivers from the field to enable more efficient spectrum use?

This is one of those situations where government involvement can spur an innovative solution.

<p>The post Expert Opinions: Ensuring full utility while evolving GNSS first appeared on GPS World.</p>

Performance-based navigation specifies the aircraft area navigation performance in terms of accuracy, integrity, availability, continuity and functionality needed to conduct specific operations in a particular airspace.

While promoting the PBN benefits of GNSS such as the GPS and the Wide Area Augmentation System (WAAS), the PBN Strategy also recognizes the need to maintain resilient PBN capabilities that remain unaffected in the event of GNSS interference, and that can continue to support PBN operations or provide safe navigation alternatives. It is a well-constructed, valuable document that provides detail on the means by which many of the Operational Improvements (OIs) described in the FAA’s Next Generation Air Transportation System (NextGen) implementation Plan (NGIP) will be achieved.

The FAA began the introduction of PBN operations following the release of its Roadmap for Performance-Based Navigation in 2003, which promoted more efficient and higher capacity operations based on the capabilities of modern aircraft and emerging GNSS-supported PBN procedures. By 2010, many PBN procedures were in use across the NAS, and especially at the busiest airports and most complicated and congested airspace. Building on this experience, the 2016 PBN Strategy recognizes that the U.S. NAS is not a homogeneous entity; its needs vary based on both location and time. To best serve NAS users and to continue to provide the safest, highest capacity, most efficient airspace in the world, some of the key concepts of the strategy are to provide:

• the right procedure to meet the need;
• structure where beneficial and flexibility where possible;
• shifting to time- and speed-based air traffic management;
• and delivering and using resilient navigation services.

To provide correct procedure and structure where needed, the PBN Strategy defines six Navigation Service Groups (NSG) and services potentially available at the airports within each group. NSG 1, now comprising about 15 airports, is reserved for the busiest large hubs that would benefit from common aircraft performance capabilities to maximize capacity. NSG 2 contains the remaining large-hub and all medium-hub airports. Small and non-hub airports comprise NSG 3. NSG 4 includes more than 500 airports, including national and regional general aviation (GA, or private plane) airports, and NSG 5 2,400 local and basic GA airports. NSG 6 consists of thousands of small airports not part of the National Plan of Integrated Airport System (NPIAS).

Time- and speed-based navigation is essential to optimal utilization of airport capability and capacity for both arrival and approach and departure operations. The ability of aircraft to more precisely follow PBN procedures because of onboard navigation capability and space- and ground-based navigation services maintains safety, increases airspace and runway utilization, and — because of more efficient, precise routing — minimizes fuel burn and carbon footprint.

The PBN Strategy also recognizes the need to maintain resilient PBN services and, while GNSS-provided PNT services are able to support both RNAV and RNP procedures, GNSS is vulnerable to both intentional and unintentional interference. To preclude loss of efficiency and capacity benefits in the event of GNSS interference, the FAA will maintain and improve the ground-based Distance Measuring Equipment (DME)/Tactical Navigation (TACAN) network to support DME-DME RNAV 2 in the enroute domain and RNAV 1 in the necessary terminal domains. Because of plans to fill gaps in coverage at high altitudes (FL 180 and above) and remove single DME facility criticality, aircraft without inertial reference units (IRUs) will be able to fly these procedures using DME-DME RNAV, although at the much lower altitudes associated with terminal operations, an IRU may still be required. For aircraft without DME-DME RNAV capability, for example General Aviation, the FAA will maintain a Minimum Operational Network (MON) of Very High Frequency Omnidirectional Ranges (VORs) to either support navigation out of a GNSS interference area or navigation to an airport where approach and landing is supported by either an Instrument Landing System (ILS) or VOR.

Commentary

PBN services depicted across Navigation Service Group airports represent the standard in the far term, 2026–2030.

The FAA’s plan to maintain resilience, while admirable, does have some issues. All of the VORs, DMEs and TACANs that provide resilient navigation services are extremely old, the vast majority designed in the 1970s and installed in the 1980s. There is no current plan to modernize or recapitalize them.

As for researching and developing an Alternate Position, Navigation and Timing capability that would support resilient PBN capability for all of aviation, maintain the ability for aircraft to report their positions via Automatic Dependent Surveillance – Broadcast (ADS-B), and support the rapid and vast emergence of unmanned aerial vehicles (UAS) and benefits, the PBN Strategy states that “During the far term and moving out into the 2030 timeframe and beyond, the FAA will continue to research the best methods for Alternate Position, Navigation and Timing (APNT).”

This delay is unfortunate, as further delay in implementing PNT resilience for all aspects of aviation, as well as for all critical infrastructure areas is, at best, imprudent, as recent agency attempts to develop and implement other resilient PNT capabilities — Enhanced DME (eDME) and Enhance Loran (eLoran) — have been suspended.

The release of the 2016 PBN Strategy is a significant event. It will help guide the agency and the aviation community forward. It will help clarify policy, facilitate decisions, drive equipage, and provide for a safe, higher capacity and more efficient NAS. It is a good start, which could be improved by recognizing the significant investments needed in resilient PNT equipment, architecture and systems.

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