In September, the U.S. Department of Transportation (DOT) issued a Request for Information (RFI) to seek industry input on Complementary Positioning, Navigation, and Timing (CPNT) technologies.

Earlier this year, the European Commission’s (EC) science and knowledge service, the Joint Research Centre (JRC), issued its report Assessing Alternative Positioning, Navigation, and Timing Technologies for Potential Deployment in the EU. It summarized the assessment of seven Alternative PNT (A-PNT) platforms which occurred during the eight month period between October 2021 and July 2022. It concluded that commercially available mature Alternative-PNT (A-PNT) technologies are already present in the market that can provide positioning and/or timing information separately from Global Navigation Satellite Systems (GNSS). It also concluded that a system of systems approach that incorporates a range of interoperable technologies, supported by standards, remains the lynchpin to resilient PNT. Will any of the technologies reviewed in the JRC Report come out on top in the U.S. as serious contenders for CPNT?

What’s In A Name?

Before comparing the JRC and DOT requirements as a potential indicator of which technologies may prevail in a U.S. contest for the same, the first issue is whether or not the DOT’s CNPT and the EC’s A-PNT even refer to the same thing. Spoiler alert: they kinda don’t.

It’s nuanced. The EC defines A-PNT as “backup solutions,” meaning “technologies providing PNT independently from GNSS.”(1)

A look at the Volpe Report from a couple years ago would lead one to believe the EC and DOT are on exactly the same page. Back then, both US law, DOT policy and research statements lumped together the terms CPNT and “backup GPS capability” or “GPS backup” technologies. Both essentially meant “capabilities to back up and complement the PNT capabilities of the GPS.”(2) (Gotta love definitions that use the same term to define the term in question.) In fact, even the September 2023 DOT CPNT Plan defines CPNT systems as resilient PNT technologies that could offer complementary service in the event of GPS disruption, denial, or
manipulation.(3)

While this sounds like more of the same, the Plan also shows an important evolution of thinking. In describing the tech DOT seeks, it says “CPNT technologies must provide increased capability, not viewed (sic) only a backup to GPS.”(3) Read that again.

It must also, according to the Plan, have a “mature threat posture against capable actors.” And the Federal Government will act as “lead investor/subscriber of services” across key domains: maritime, rail, and surface applications.

That’s why we see what we see in DOT’s recent RFI. (Previous IG coverage here: https://insidegnss.com/all-jammed-up-dot-urgently-seeks-complementary-pnt/) And there’s more. A glaring difference between A-PNT and CPNT, at least from this initial testing volley, lies in the selection criteria for potential participants. The JRC required a Technology Readiness Level (TRL) greater than 5 for position/navigation services or greater than 6 for timing services. The DOT RFI required a TRL of 8 or beyond. This requirement harkens back to the CPNT plan indicating a need for “mature” technology. A TRL of 8 or 9 indicates something already in use, off-the-shelf if you will, on the commercial market. It underscores the DOT’s current sense of urgency to find it.

A close read of the RFI also shows the DOT seeks interoperable tech. It’s not looking for stand alone, apples-to-oranges systems. It’s looking for an entire CPNT ecoverse to bridge the gap should GPS go Poof!

Yet among all of these differences, the needs driving these different requirements are generally the same here and across the pond.

The Driving Need

Both the U.S. and EC rely heavily on GNSS services for PNT, across a myriad of burgeoning sectors from car-sharing platforms, intelligent logistics solutions, autonomous transit systems (e.g., vehicles, vessels, and aircraft), geolocation-based applications, precision agriculture and more. Perhaps more importantly, vital infrastructures, deemed strategic linchpins for modern societal operations, leverage PNT services, particularly the timing proficiencies. These include telecommunications, energy, finance and a spectrum of transportation modalities (road, maritime and aviation). The need for, and the characteristics of, likely user communities who need A-PNT/CNPT are very similar globally.

With regard to the European front, the JRC Report indicated that an uptick in GNSS jamming and spoofing incidents presents a threat to the GNSS-driven EUR 2 trillion socio-economic boom across Europe (the EU27, UK, Norway and Switzerland) projected by 2027. In terms of dollars and sense, the U.S. and United Kingdom (U.K.) threat assessments have posited that the economic detriment of GNSS unavailability could approximate a EUR 1 billion daily.

These threat estimates do not include GPS jamming incidents in or around the eight countries still pending EU membership, most notably Ukraine.(4) Spillover GPS jamming effects from Russian electronic warfare (EW) has already adversely impacted commercial airlines and shipping in both Bulgaria and Romania. Some have posited that this war-related EW activity has significant potential to destabilize the entire Black Sea region.(5)

In response to these ever-increasing vulnerabilities, to bolster the resilience and ensure the continuity of critical operations, the U.S., the European Union (EU) and U.K., among others, look to find and implement robust and resilient PNT services, whether as alternatives, backups to or completely autonomous-from-but-interoperable-with conventional GNSS services on their own home fronts.

So, does the JRC Report provide any relevant insights for a DOT CPNT solution? Answer: a few.

Some Clues

While the EC characterizes its test results as a “qualitative assessment,” rather than a benchmark, some things in the JRC Report nevertheless can provide a bit of insight into some of the technologies the DOT may be eyeballing for holistic U.S. CPNT system-of-systems solutions. (Previous IG coverage provides a detailed explanation as to how the JRC demos were conducted: https://insidegnss.com/backing-up-gnss/).

Let’s focus on the capabilities to knock out a few contenders right away, at least in terms of independent tech that can act as more than just a back up to GPS, meaning one that could go it alone (while also working well with others). The JRC demonstrations involved seven selected providers. OPNT, 7 Solutions SL, SCPTime and GMV focused on timing services only. That makes them interesting but not the final answer. Satelles, Locata and NextNav successfully demonstrated both positioning and timing. That puts them in the ring.

Next, let’s use the TRL level to show that at least one contender remains down for the count and show our Top 3 are still in the fight. As noted, the EC only required a TRL greater than 5 for position/navigation services or greater than 6 for timing services; DOT seeks a TRL of 8 or higher.

Based on the TRL alone, the DOT RFI’s more stringent criteria GMV Aerospace and Defence SAU is K.O.’d. Although the key technologies used in the company’s WANtime solution all have a high TRL (minimum 6), which qualifies it for the JRC project, each technology individually has a different TRL. Combined their average TRL levels put GMV Aero’s tech at an estimated overall TRL of 7. (6) For example, its atomic clocks, clock modeling and steering and time transfer technology, based in GNSS or TWSTFT and used in the operational generation of Galileo System Time (GST) in the Galileo Precise Timing Facilities (PTFs), can all be considered TRL 9. The company gave its White Rabbit (WR) a TRL of 8, as it noted that “especially long-range WR, poses quite a few challenges and requires careful network engineering.” The application of DTM, packet-exchange network technology, to timing applications is still under development and comes in at TRL 7. Higher-precision network time protocol (NTP) is a relatively new, experimental area and can be considered TRL 6.

On the other hand, Satelle’s LEO satellites for satellite timing and location (7), NextNav’s TerraPoiNT ground-based solution that leverages existing cellular LTE/5G signals and dedicated Signal Sensors and/or TerraPoiNT transmitters (8) are both reported as TRL 9.

While the TRL level for Locata’s LocataNets, a system of terrestrial beacons to provide PNT signals to dedicated receivers in a localized area, were not readily accessible, its commercial deployment in different environments like open-cut mines and harbors, combined with its testing by significant entities like the U.S. Air Force at the White Sands Missile Range, suggests its mature stage in the TRL spectrum, possibly at or near TRL 9. This pseudolite alternative uses multiple, geographically dispersed, terrestrial transmitters to provide passive or pseudo ranging signals that can be used to accurately calculate position. Notably, the EU ranks pseudolites in general at a TRL of 9. (9)

Assuming Satelles, Locata and NextNav have thrown their hats in the ring for DOT’s RFI, and that they can meet DOT’s security and interoperability requirements, their tech illustrates a sea change from reliance on middle earth orbit (MEO) satellites for PNT. Satelles’ solution orbits in LEO, while Locata and NextNav are both terrestrial based. The times (no pun) they may be a changin’.

Next Steps

So, where do we go from here? In Europe, even though the EC just put out its European Radio Navigation Plan 2023 in June, it already has plans in the works to update it. Europe also intends to evolve Galileo and EGNOS and issue new regulations. What exactly it intends to do with the JRC 7, if you will, remains a mystery.

But likely at least 3 of those 7 companies may have a real shot here in the U.S. The DOT’s recent RFI. That’s the first step. The next would be the issuance of a request for proposal (RFP) to actually make that testing a reality. Applying the tech to real world use cases would be the goal. To do that, as noted way back in Volpe’s 2021 report, and now the JRC report, also requires the creation of standards.

For now, who’s really positioned to navigate DOT’s process, and what’s the timing? We may have teased out a few clues here, but, in the end, only time will tell.

References:

1. https://joint-research-centre.ec.europa.eu/scientific-activities-z/alternative-pnt_en#:~:text=To%20address%20this%20threat%2C%20it,or%20A%2DPNT%20for%20short.
2. https://www.transportation.gov/sites/dot.gov/files/2021-01/FY%2718%20NDAA%20Section%201606%20DOT%20Report%20to%20Congress_Combinedv2_January%202021.pdf
3. https://www.transportation.gov/sites/dot.gov/files/2023-09/DOT%20Complementary%20PNT%20Action%20Plan_Final.pdf
4. https://european-union.europa.eu/principles-countries-history/joining-eu_en
5. https://www.rferl.org/a/russia-gps-jamming-black-sea-romania-bulgaria-ukraine/32655397.html
6. https://joint-research-centre.ec.europa.eu/system/files/2023-02/Report_GMV.pdf
7. https://satelles.com/wp-content/uploads/pdf/Satelles-STL-Data-Sheet.pdf
8. https://nextnav.com/gps-alternative/
9. https://data.consilium.europa.eu/doc/document/ST-10259-2023-INIT/en/pdf
10. https://www.minalogic.com/en/member-news/scptime-selected-by-the-european-commission/
11. https://joint-research-centre.ec.europa.eu/system/files/2023-02/Report_7Sol.pdf

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For years, the U.S. Department of Transportation (DOT) has been exploring the technologies and systems necessary to provide positioning, navigation, and timing (PNT) services to complement the Global Positioning System (GPS) so that these critical services remain available even when GPS signals are disrupted. In the past few months, the department has ramped up these Complementary PNT (CPNT) efforts, from its issuance of a CPNT Action Plan in September to a related Request for Information (RFI) seeking industry input on CPNT technologies. What are these efforts, how are they going and why the sense of urgency now?

The Plan

The DOT’s CPNT Action Plan, issued this September, provides a comprehensive roadmap to ensure the safety, security, and efficiency of critical infrastructure in the face of potential GPS disruptions through the adoption of CPNT technologies.

Stakeholder engagement across the PNT enterprise, including providers of PNT services and critical infrastructure owners and operators, ranks high among the plan’s key strategies and actions. So does the development of CPNT solutions specifications and standards. The plan further includes a goal of establishing field trials and test ranges to evaluate the performance and resilience of domain-specific (e.g., maritime, rail, and surface applications) CPNT technologies, based on quantitative performance metrics.

The DOT also plans to act as the federal PNT services clearinghouse to provide real-time situational awareness, performance monitoring, and response capabilities, and as the government’s lead adopter and purchaser of PNT services to accelerate testing and market development in the private sector. The department appears to have fast-tracked this federal marketplace strategy with the issuance of an RFI to industry on CNPT tech.

The RFI

On September 11th, DOT’s Volpe Center issued a 15-day quick-turn RFI to industry seeking information about the “availability and interest in carrying out a small-scale deployment of high-level technology at a field test range to characterize the capabilities and limitations of such technologies to provide PNT information that meet critical infrastructure needs when GPS service is not available and/or degraded due environmental, unintentional, and/or intentional disruptions.” It then extended the deadline to October 10th.

The RFI, which specifically seeks to field test CPNT technology that stands at a Technology Readiness Level (TRL) of eight or beyond, signals the immediate need for a complete solution from core infrastructure to User Equipment (UE).

In an apparent effort to spur broader assimilation of CPNT technology, the RFI outlines a vision of three field test range models to nurture a collaborative environment between CPNT technology vendors and critical infrastructure consumers. It delineates a meticulous setup for examination at the selected Test Range Sites, where either the U.S. Government or designated operators will facilitate the CPNT technologies’ deployment.

To this end, the DOT seeks detailed commentary on test range deployment logistics, across a spectrum of scenarios (e.g., varying levels of urbanization, terrain diversity, meteorological conditions, and indoor/outdoor environments), potential user sectors, exemplar use-cases, as well as an analysis of the economic and safety dividends in alignment with various critical infrastructure sectors. It requires diagrams and achievable execution timelines for such field trial testing.

The DOT set the bar high. Companies replying to this RFI must meticulously outline the technical specifications of their CPNT technology, with a focus on accuracy, integrity, and resilience, especially under adverse GNSS conditions. They must also thoroughly explain their technology’s resilience against a range of signal threats, both intentional and unintentional, including jamming and spoofing.

Additionally, they must produce sufficient data on information assurance across the company’s supply-chain, operational security, system control and maintenance to illustrate robust security, consistent with the national cybersecurity framework.

The RFI places the coherence among system components and their efficacy in an operational environment high as a top priority. The technology must have also undergone a stringent testing and evaluation process, manifesting its designed functionality with precision.

This RFI underscores the DOT’s escalating endeavor to bolster the resilience of the nation’s critical infrastructure against disruptions to GPS. It reflects a growing awareness of the potential risks associated with GPS dependencies and represents an organized effort to mitigate them. But why the sense of urgency now?

The Timing

The problem of potential GNSS disruptions, whether due to natural phenomena, technical issues, or deliberate interference (e.g., jamming or spoofing) is not a new one. It has been well documented, for some time now, that the absence or degradation of GNSS signals can have significant implications for safety, security, and economic activities across the defense enterprise and civil society.

The pressing need for resilient PNT solutions that can function if GNSS gets knocked off line seems to have a direct correlation to current events – in particular, the prevalence of GNSS jamming in both the Hamas-Israel and Russia-Ukraine conflicts. Interfering with GNSS signals, itself a form of electronic warfare (EW), enables combatants to undermine a wide range of adversary capabilities, from simple navigation to advanced weapon systems that rely on GNSS for targeting. The repercussions of these tactics, however, have transcended the battlefield. They’ve extended into the digital infrastructure and electromagnetic spectrum upon which civilian infrastructure relies for precise PNT data.

In the theater of conflict between Israel and Hamas, the strategic use of GNSS jamming has emerged as a significant player. As the hostilities began, Hamas employed GNSS jamming to impede Israeli communication networks. To neutralize aerial threats from drones, shield against airborne assaults and thwart Hamas’s ground offensive and missile launches, Israel intensified its own use of GNSS jamming. This jamming had a spillover effect on civil aviation. In one case, a potent GNSS jammer deployed at an airforce base had reverberations on regional civil aviation.

Similarly, GNSS jamming has been a significant issue in the Russia-Ukraine conflict. While Russia’s military invasion began in February 2021, it has reportedly been engaged in GNSS jamming activities in the region since at least 2014. Over the past several months, these activities have ramped up to a reported 15 regions. Among other concerns, this could cause significant navigational challenges for civil aircraft.

These persistent GNSS jamming activities reflect a broader strategy of EW as a critical component of modern military operations. The problem is that GNSS is a dual-use technology. Many civilian sectors also depend heavily on GNSS. Its disruption can have wide-ranging implications on both the military and civilian sectors alike. For the U.S. government, these electronic skirmishes have underscored the vulnerability of both mil-civ targets to GNSS disruptions. They appear to have propelled the DOT’s current quest for robust CPNT systems capable of withstanding electronic threats. So, who is answering the call?

The Contenders

The specific responses to the US DOT RFI on CPNT at TRL 8 remain unavailable to the public. However, several companies which have engaged in demonstrations and evaluations concerning PNT technologies, both in the US and in Europe, have likely responded.

Earlier this year, the European Joint Research Centre conducted a test campaign to evaluate various Alternative Position, Navigation and Timing (A-PNT) platforms that could provide precise PNT without the use of navigation satellites. The rigorous assessment spanned over eight months. It involved evaluations in both indoor and outdoor environments at both the JRC premises and other locations and encompassed time transfer over the air, fiber, and wired channels. The campaign identified seven companies as having mature technologies ready to take on CPNT: OPNT, Seven Solutions SL, SCPTime, GMV Aerospace and Defence SAU, Satelles Inc., Locata Corporation Pty Ltd and NextNav.

Some of these same companies had also previously participated in U.S. technology demonstrations, specifically Volpe Center’s 2020 demos. Despite the showing of these companies in 2020, in its 400+ page final report to Congress on the matter in 2021, DOT opined that “none of the systems can universally backup the positioning and navigations capabilities provided by GPS and its augmentations.”

Perhaps in the three years between the Volpe and JRC demos, CPNT technology has leap-frogged forward. Regardless, there’s a good chance that at least a handful of the companies that showcased their tech in both the U.S. and Europe have thrown their hats in the ring to respond to the DOT’s most recent call for CPNT tech.

In the meantime, electronic threats continue to surge. Let’s hope global PNT authorities pick some winners to shore up PNT…before we get jammed up.

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A look at the state of 5G NR NTN.

If beyond visual line of sight (BVLOS) operations are the “Holy Grail” of the UAS industry, harnessing the capability of non-terrestrial networks (NTNs), or Space-Based Adaptive Communications Node networks, appears to be the equivalent for a 5G communication system network—particularly in low earth orbit (LEO) satellite communications (SatComs) constellations.

UAS, among many other systems, can play a vital role in developing requirements, which could, in turn, help mitigate current technological limitations for BVLOS and a wide range of other use cases that depend on accurate positioning, navigation and timing (PNT). However, as in so many other areas of emerging technology, challenges in implementation and standardization remain unsolved. Here’s a rundown of the state of play for 5G LEO SatCom networks.

The Basic Plan

To appreciate the game-changing nature of 5G New Radio (NR), you must first have a basic understanding of how traditional mobile telecommunications work.

Telecoms traditionally consist of four key components, according to Ericsson, an information and communication technology (ICT) service provider. Most of us engage directly with user equipment (UE) devices such as smartphones and tablets. The Radio Access Network (RAN) wirelessly connects UEs using radio frequencies (RF). Coordination between various parts of the RAN and the connection to the internet occurs through the core network (CN). Finally, the transport network supplies the connection between the RAN and the CN.

Complex integrated hardware and software enable these functions, even in traditional comms. Baseband equipment that performs all of the signal processing functions required for wireless communications (e.g., for multiple antennas, to detect/correct transmission errors, provide security and manage resources) contains high performance electronics and cutting edge software. Radios ensure signal transmissions travel on the correct bands at the required voltage and actually convert digital information into those signals. Antennas beam out those electric signals into radio waves.

5G, which requires Multiple-Input Multiple-Output (MIMO), adds layers of complexity to this basic telecom system. It requires cross-functional integration, such as integrating radios and baseband hardware and software with antennas. 5G NR RAN (which replaces the Long Term Evolution (LTE) high speed and low latency RAN) and CN software can be deployed and managed on the same infrastructure. 

For this reason, RAN radios (baseband and antenna-integrated) and CN sites depend on software, on each other and on complex code. For maximum coverage, companies have built additional base radio stations, called gNB (Next Generation/gNodeB, which replaces the eNB or eNodeB or Evolved Node B) and deployed AI and ML to orchestrate and balance traffic. 

Why does this matter? 5G’s unified interface enables higher speeds, reduces latency and increases the availability and reliability of connections. 

The Value Proposition

According to Qualcomm, 5G will fuel “massive IoT” and drive global growth. The company’s landmark 5G Economy Study found 5G could potentially enable up to $13.1 trillion worth of goods and services across a diverse group of businesses worldwide by 2035. More than 60 countries have already deployed 5G.

Now add in NTNs, which deliver 5G/NR service via space (satellite) or air (airborne platform) to the 5G mix. This multi-layered network can include SatCom networks, high altitude platform systems (HAPS), UAS and other air-to-ground networks.

According to 3GPP, the NTN 5G value proposition is clear. NTN systems can significantly bolster 5G service continuity where a single or series of combined terrestrial networks cannot, particularly for mobility assets and mission-critical communications. NTN can bridge 5G service coverage gaps where terrestrial networks do not exist or simply do not reach. This includes oceans, deserts, wildernesses and urban areas. Scalability, through NTN’s wide area coverage and ability to multicast, also tops its list of benefits. 

NTN 5G can support a wide range of use cases, including aeronautical and maritime tracking systems. Specifically, Automatic Dependent Surveillance-Broadcast (ADS-B), which is based on the capability of the aircraft to navigate to a destination using GNSS data and barometric altitude, allows for communication with air traffic control, cooperative surveillance, separation and situational awareness. It depends on aircraft navigation system data derived primarily from GNSS signals and then broadcast to aircraft and ground-deployed infrastructure. 

But this infrastructure does not exist in a number of areas, including over oceans and in the Arctic. LEO-based ADS-B receivers could contribute to the ATC relay network. This would result in low latency and secure coverage globally. In the maritime sector, the equivalent tracking system, Automatic Identification System (AIS), also benefits from space-based receivers.

The benefits of NTN 5G extend beyond transportation and more broadly for internet of things (IoT) applications, from surveillance of infrastructure to precision agriculture. 

Standards Moving Forward

The 3rd Generation Partnership Project (3GPP), a global partnership of telecommunications standard development organizations, started working on 5G NR NTN about 5 years ago. Its first study, Release 15 (Rel-15) documented in TR 38.811, targeted deployment scenarios and models that included not only LEO and HAPS, but GEO satellites as well. It addressed issues such as relevant beams, elevation angles, satellite deployment footprint, various NTN terminals and antenna arrays. 

The follow on study, Rel-16, focused on minimum viable architecture, higher layer protocols, and physical layer aspects (TR 38.821). This study concluded that the group’s NR work provided a solid basis to support NTN. It identified additional areas of study including: timing relationships, uplink time and frequency synchronization, and hybrid automatic repeat request (HARQ), a combination of high-rate forward error correction (FEC) and automatic repeat request (ARQ), essential for reliable data transmissions.

Earlier this year, ratified Rel-17 focused on 5G system enhancements. Among other things, Release 17 involves physical layer aspects, protocols, architecture and radio resource management. This study assumes all UEs have GNSS capabilities. 3GPP “froze” (meaning no further functions can be added to the specification) the Protocols for this study in March 2022 and the Protocol Code (OpenAPI) in June. According to 3GPP, the “Release 17 Description; Summary of Rel-17 Work Items” (TR21.917) remains in production. 

In the meantime, 3GPP launched the Rel-18 study. It focuses on 5G Advanced, addressing extraterritorial coverage of satellites and high altitude systems.

Progress continues to move forward on the coding side of the house, courtesy of the OpenAirInterface Software Alliance (OSA). This is significant because many of these systems rely on complex code stacks. The OSA, a French non-profit organization established in 2014 and funded by corporate sponsors, is the home of OpenAirInterface (OAI). OAI, an open software endeavor, has gathered a community of developers from around the world who work together to build wireless cellular RAN and CN technologies. 

The OSA OAI 5G Project Group seeks to develop and deliver a 3GPP compatible 5G gNB RAN software stack under the OAI Public License V1.1. In October, the group provided an OAI codebase status update and development roadmap.

Simultaneously, the organization’s related OAI 5G-LEO extension for 5G satellite links aims to use the OAI as a tool to assist in 5G NTN R&D. This 5G-LEO Project has four main objectives, according to the European Space Agency (ESA):

1. Select a 5G-LEO baseline scenario for 3GPP NR-NTN system deployments to implement and verify with the extended OAI library.

2. Identify fundamental codebase gaps and changes to extend OAI to the 5G-LEO baseline. 

3. Implement required OAI code adaptations for the different layers of the 3GPP protocol stack to support 5G-LEO within Rel-17 and potentially in Rel-18.

4. Set up an end-to-end 5G-LEO demonstrator in the lab for experimental validation of the OAI extension for the 5G-LEO baseline scenario.

This two-phase project, started in December 2021, is in its second phase. It’s focused on implementation, software compliance and demonstration.

Challenges and Stratospheric Possibilities

R&D continues to tackle other challenges that must be mitigated for successful LEO-based 5G NTN. Propagation delays and large Doppler shifts caused by moving cells rank high among them.

Propagation delays result in latency. Depending on the satellite’s altitude, long distances between satellite constellations, ground stations, and user terminals cause time delays in radio wave transmissions. While delays from LEO satellites are much shorter than higher altitude GEO satellites, the constellation and ground station deployments must be larger to cover wider areas. This can increase costs. Groups are exploring workarounds such as sat-to-sat relays, or mesh networks for CN functions, to mitigate these issues.

On the military side, the same mitigation measures used to solve common latency issues in GEO MIL/SATCOM applications can be applied to a LEO MIL/SATCOM architecture, said Jason “JD” Danieli, CEO of Colorado-based Giuseppe Space Enterprises. 

“Modeling, simulation and analysis, as we commonly refer to as MS&A, is an extremely important first step prior to deploying new tech. There are so many variables to consider and account for. A common SW tool, such as MATLAB, is just one of many tools we consider when solutioning,” Danieli said. “We attempt to address issues prior to deployment such as interoperability, performance and resiliency.” 

Research also remains ongoing to address Doppler effects in the LEO orbit. This phenomenon describes the increases (or decreases) in the frequency of sound, light or other waves as the source and observer move toward (or away from) each other. Waves emitted by a source traveling toward an observer get compressed. The LEO satellites and airborne platforms for 5G NTN move very fast while the user terminal remains either stationary or moves slowly. This results in large Doppler shifts experienced by the receiver, leading to communication degradations between transmitters and receivers. This is why 3GPP assumes NTN devices will be equipped with a GNSS chipset to determine position and calculate the needed frequency adjustments. 

But GNSS has its own challenges in terms of vulnerability. Efforts to make PNT more resilient continue to churn…slowly. 

On the bright side, LEO satellites offer several attributes that are attractive to supplement GNSS for positioning and timing. This includes an abundance of signals, favorable geometric configurations, and diverse signal frequencies. 

“With 5G NTN entering the stage, we will have even more satellite signals to consider on top of the 3,000+ LEO satellites whose signals have already shown potential to supplement GNSS,” said StarNav CEO Joshua Morales, who has spent nine years building PNT systems that use cellular and LEO satellite signals as a backup to GPS.

New partnerships have cropped up to tackle these challenges and take advantage of the benefits that NTN has for the future of 5G. Last summer, for example, Ericsson, Qualcomm Technologies, Inc. and French aerospace company Thales announced a partnership for the first testing and validation of 5G NTN. This work aims to validate 3GPP’s assumption that 5G NTN can be supported in a smartphone form factor. Initial tests are taking place in an emulated space environment in France. 

With the possibility of successful 5G NTN just within our grasp, we can no longer just say the sky’s the limit—because the possibilities are truly out of this world. 

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While an independent report from NASEM has validated some NTIA GPS interference claims, no real mitigation is in in sight.

A Congressionally-mandated independent technical review from the National Academies of Sciences, Engineering, and Medicine (NASEM) recently found that Ligado Networks’ low-power terrestrial mobile satellite services (MSS) in the L-band may not harm most commercial uses but will, in fact, interfere with GPS for high precision receivers, Department of Defense (DoD) missions and downlinks from Iridium satellite terminals.

To pile on, mitigation measures may not be practical “at operationally relevant time scales or at reasonable cost.” The NASEM report also suggested FCC tighten up its receiver standards and spectrum-related proceedings in the future. Let’s review the bidding.

How Did We Get Here?

April marked the 2-year anniversary of the FCC granting the conditional and modified license (FCC 20-48) for Ligado’s national MSS network. But the back-and-forth on concerns about near-band interference goes back more than 20 years. The project’s history, dotted with stops and starts (including during the bankruptcy of Ligado’s precursor company LightSquared) and contradictory testing results has created a lengthy public record rife with controversy and emotion.

In the one corner, stands Ligado. Its vision is “to modernize American infrastructure by connecting the Industrial Internet of Things” with state-of-the-art satellite technology and plans to deploy Custom Private Networks to provide the cutting edge technology needed for the future of 5G. Ligado believes interference claims have been overblown and that potential interference can be mitigated, and stands ready to discuss how to do that.

On the other side of the ring, we have the National Telecommunications and Information Administration (NTIA) on behalf of the executive branch, industry, trade associations and Ligado opposition groups such as the Keep GPS Working Coalition. This crowd remains adamant that Ligado’s L-spectrum block will pose a threat to the viability of civil and military GPS receivers across the country.

In 2020, when the FCC unanimously and conditionally approved Ligado’s amended license request, these opponents pled with the FCC to both halt the creation of Ligado’s network and reconsider its decision. In January 2021, the FCC struck down the request to halt Ligado’s progress. However, it still hasn’t ruled on the reconsideration issue.

Much of the debate around the propriety of Ligado’s license is on whether the 1 dB C/N0 interference metric proposed by the feds, but not embraced by the FCC in its ruling for Ligado, is the correct standard to use.

In the midst of this bout, Congress jumped in to referee and ultimately leveraged its power of the purse. In Section 1661 of the 2021 National Defense Authorization Act (NDAA), Congress stopped the DoD from using government funds for technical or information exchanges with Ligado or to retrofit affected equipment, required the Department to submit estimates of reimbursable costs for any retrofit, and directed the DoD to charter an independent NASEM review.

At the heart of this review, NASEM was to compare “the two different approaches used for evaluation of potential harmful interference” and submit a report. The two other elements of NASEM’s task included assessing the: (1) likelihood that the authorized Ligado service will create harmful interference to GPS, MSS and other commercial or DoD services and operations and (2) feasibility, practicality and effectiveness of the measures in the FCC order to mitigate harmful interference effects on DoD devices, operations and activities.

NASEM got a late start and missed its 270-day deadline. However, its effort can be characterized as nothing short of herculean. The group, led by Committee Chair Michael McQuade, Ph.D., strategic advisor to the president at Carnegie Mellon University, listened to dozens of hours of live testimony and reviewed almost 100 documents over several months before rendering the following conclusions on the three tasks:

TASK 1: Approaches to Evaluating Harmful Interference Concerns. The committee determined that neither of the NTIA or Ligado approaches to evaluating harmful interference concerns effectively mitigates the risk of harmful interference.

While both approaches have a role to play in such evaluations, and the NTIA signal-to-noise ratio (SNR) approach may be a bit better than Ligado’s position measurement approach, each has serious flaws.

The SNR approach, the report found, is inflexible and, in some cases, has an overly conservative emission limit because “no single value for signal-to-noise degradation determines when the various types of possible harm to receiver performance will become significant.” The measurement approach depends on a test sampling approach too narrow to apply to the many and varied uses of the GPS system. The mic drop portion states:

“Ultimately, both proposed approaches are cumbersome, owing to the intensive, device-by-device testing required. They do not provide an engineerable, predictable standard that new entrants can readily use to evaluate impact. As such, these approaches impede progress in making more efficient and effective use of the spectrum.”

TASK 2: Harmful Interference to GPS and Mobile Satellite Services. In Ligado’s favor, the report found that, as authorized by the FCC, most commercially produced general navigation, timing, cellular or certified aviation GPS receivers will not experience significant harmful interference from Ligado emissions.

That said, critical high-precision receivers remain the most vulnerable to significant harmful interference from Ligado operations, as do downlinks for Iridium terminals within up to 732 meters (“a significant range”) of Ligado user terminals operating in the UL1 band.

The report discussed DoD systems and missions in a non-public and classified annex, but noted the DoD and agency partner testing demonstrated unacceptable harmful interference to national security missions.

The fix? The report found current state-of-the-art technology could be used to build a receiver robust enough to peacefully coexist with Ligado signals and achieve “good performance” for any GPS application. But, see the conclusions on task 3…

TASK 3: Feasibility, Practicality and Effectiveness of Mitigation Measures in the FCC Order. The FCC’s proposed mitigation measures included, among other things, exclusion zones for Ligado emitters, replacing antennas, filters or full receivers, enabling a “kill switch” to turn off Ligado emitters in some areas and other negotiated mitigations between Ligado and the affected parties.

The report found that while the proposed mitigations may be effective for DoD and national security end-users, where these are immediately available, such mitigation is neither satisfactory nor practical without both extensive dialogue among the impacted parties combined with long and expensive operational test certifications. On the commercial side (even commercial tech that DoD employs), “mitigation may not be practical at operationally relevant time scales or at reasonable cost.”

So, Where Are We?

The bottom line: no perfect interference standard exists; most commercial GPS will be OK but really important national security and satellite tech will experience inference from the Ligado emitter; state-of-the-art tech could help mitigate GPS interference, but would require collaboration between the parties, would take a really long time and would be expensive.

And yet both sides touted the report as a win.

Ligado professed in a statement, “The NAS(EM) found what the nation’s experts at the FCC already determined: A small percentage of very old and poorly designed GPS devices may require upgrading. Ligado, in tandem with the FCC, established a program two years ago to upgrade or replace federal equipment, and we remain ready to help any agency that comes forward with outdated devices. So far, none have.”

Not surprisingly, the DoD took a different view of the report:

“The NASEM study confirms that Ligado’s system will interfere with DoD GPS receivers, which include high-precision GPS receivers. The study also confirms that Iridium satellite communications will experience harmful interference caused by Ligado user terminals. Further, the study notes that when DoD’s testing approach, which is based on signal-to-noise ratio, is correctly applied, it is the more comprehensive and informative approach to assessing interference. The study also concludes that the Federal Communication Commission’s (FCC) proposed mitigation and replacement measures are impractical, cost prohibitive, and possibly ineffective.

These conclusions are consistent with DoD’s longstanding view that Ligado’s system will interfere with critical GPS receivers and that it is impractical to mitigate the impact of that interference.”

As both sides chalk the NASEM report up as a validation of their position, much work remains to be done.

Where Do We Go From Here?

For one, the FCC needs to move out—either way—on the pending Petition for Reconsideration. Enough is enough. In the latest move in that arena, on October 13, a host of businesses and associations, jointly requested the FCC to consider the unclassified portion of the NASEM report “to ensure completeness of the record” for the pending petitions for reconsideration.

As we know, however, the FCC has not taken any action on the Ligado proceedings since early last year. The Commission, which exists independent of the White House, remains deadlocked in a 50/50 split and one member short of a full majority. Meanwhile, the Senate continues to stonewall the appointment of Democratic nominee, Gigi Sohn, to the FCC. Sohn’s appointment would seal a Democratic majority. Not surprisingly, Republicans have stiff-armed her nomination, putting off the vote for more than a year now. Sohn would have given Chairwoman Jessica Rosenworcel the vote needed to pursue rulemakings opposed by the commission’s Republicans.

According to Jennifer Richter, Partner and Head of the communications and information technology practice at Akin Gump, an award-winning global law firm, the Commission does not need to wait. “If Chairwoman Rosenworcel has a majority on any item, that item can pass,” she said. That means the FCC could not only take action on the petition, but also move out on several reasonable suggestions in the NASEM report.

To start, the FCC could update its definition of “harmful interference.” The FCC currently defines it as “interference which endangers the functioning of a radionavigation service or of other safety services or seriously degrades, obstructs, or repeatedly interrupts a radiocommunication service operating in accordance with [the International Telecommunication Union] Radio Regulations.” The committee blamed this non-quantifiable definition of harmful interference for the years long Ligado quagmire, which it says, “has tied up spectrum, as well as untold resources of the participants.”

What could work? In the case of GPS, a harmful interference criterion that accounts for position error effects, acquisition and tracking challenges, and continuity of service potentially based on a maximum limit for degradation of C/N0, possible effects of out-of-band emissions (OOBE) and adjacent-band signals in a designated frequency range for a reasonably well designed receiver to dictate an adjacent-band power mask that the FCC would guarantee going forward for a given period of time.

The FCC might also consider revising design and implementation standards for receivers themselves, in a nuanced way. As the report noted, “One must…distinguish between receiver standards that address operation in the current environment and those that might protect operation in the presence of some future uses that were vastly different in their impact.”

Then there’s the matter of spectrum, and how it should be allocated from a process standpoint. The FCC has no cohesive policy about rights of current users, the impact of equipment lifetime, business models, and similar essential considerations. According to the report, “This must be established outside the pressures of any one spectrum decision” and “current actions supporting the repurposing of spectrum is at best, ad hoc, and certainly does not operate on the same timeline as that which the technology is capable of changing.”

Appearances also matter. The committee suggested all parties might have found the proceedings more palatable had the FCC made independent findings of fact instead of quoting out of the various parties’ filings.

Fairness aside, these issues always boil down to money. But the FCC also has no policies for equipment owner’s rights when it comes to spectrum. The report outlined issues to think about such as: “What is the lifetime for any mitigation responsibility? What is the responsibility for receiver performance? How is any such responsibility addressed administratively?”

Finally, revectoring processes to take a more collaborative, instead of litigious, approach would go a long way to ending “successive cycles of argument.” Steps might include jointly studying and testing the impact of proposed regimes using agreed-upon criteria, experiments and cases. Gone are the days of completely segregated federal and non-federal spectrum.

If the FCC encouraged both communities to have more internal and external coordination and related negotiation, we could all have a higher degree of confidence in the process, our federal agencies and the equitability of spectrum allocation.

Read the NASEM report. You can read the full Ligado report here:
https://nap.nationalacademies.org/read/26611/chapter/1.

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Space debris poses a danger to PNT. Here’s a look at the threat and how the FCC plans to regulate its removal.

The resilience of the Global Navigation and Satellite System (GNSS) that enables mission and life-critical position, navigation and timing (PNT) remains a topic of interest around the world. Threats to PNT continue to increase exponentially. Space-based threats rank high among them, including space debris.

Recently, the Federal Communications Commission (FCC) caused a bit of a stir by indicating it plans to issue regulations governing activities in space that currently fall between jurisdictional policy lines, including on the controversial matter of debris removal. Will there be clarity on this issue for the PNT industry soon despite the clutter among the stars and in the halls of government?

The Threat Spectrum

Earth’s orbit, home to GNSS satellite constellations, continues to grow increasingly crowded. According to the most recent statistics from the European Space Agency (ESA), humankind has launched about 13,630 satellites into Earth’s orbit since 1957, the beginning of the Space Age. Of those, almost 9,000 still remain.

While the majority are functional, more than 2,500 defunct satellites also continue to zip around in orbit. They have become nothing more than very large pieces of debris, which may break up, explode, collide or be involved in an event that results in fragmentation. 

Such mayhem has already occurred. The first documented case of the destruction of an operational satellite after a collision with a defunct satellite happened in early 2009. In that case, an inactive Russian military communications satellite destroyed an American Iridium 33 communications satellite. The impact blew both satellites apart. The ESA estimates more than 630 of the currently defunct satellites in orbit may be involved in similar events.

Add this to an environment already littered with hunks of other dangerous junk. The space surveillance networks regularly catalog and track 36,500 objects of debris larger than 4 inches across. But not all objects are tracked. Based on statistical models, ESA estimates there are 1 million chunks of space debris from 0.4 inches to 4 inches and 130 million from .04 to 0.4 inches. The total mass of this space garbage is estimated to weigh in at more than 10,000 tons.

The problem will continue to get worse. Computer simulations project that space trash between 4 and 8 inches may multiply 3.2 times over the next 200 years. These same models predict debris less than 4 inches will increase even more, by a factor of 13 to 20.

This raises serious concerns for PNT resilience. While the danger of satellite-to-satellite impacts may be obvious, even a tiny fragment of debris in space can cause catastrophic damage to satellites. These objects often travel faster than a speeding bullet, at speeds of more than 22,300 miles per hour. This can lead to satellite destruction and result in fragmentation. 

Growing orbital congestion also increases the risk of unintentional radio frequency interference.

For these reasons, the costs of mitigating space debris continue to add up. In addition to costs associated with tracking it, companies and governments pay a hefty price for design measures, dodging space debris in orbit or scrubbing missions entirely. Considering a GPS III satellite costs $400 million or more to build, an ounce of prevention may be worth the potential financial losses of a collision.

A Big Cluster

From a policy standpoint, space debris remains an unsolved global issue. Space law consists primarily of international agreements, treaties, conventions, and United Nations General Assembly resolutions and rules and regulations of international organizations. None of these explicitly forbid the production of space debris. They also don’t indicate who is responsible for removing it.

For example, the 1967 Outer Space Treaty imposes general responsibilities on member states for national activities to ensure they are conducted in conformity with the treaty (with the premise of freedom for exploration by all), to authorize and continually supervise its activities, and to share international responsibility for activities in which the state is a participant. Article VIII provides that a state “shall retain jurisdiction” and control over its objects. Most interpret this as including debris. Thus, states and organizations make their own rules for dealing with debris.

In the United States, just this July, the White House Office of Science and Technology Policy released the National Orbital Debris Mitigation Plan to meet space sustainability priorities to mitigate, track and remediate debris. This new 14-page plan supports the overarching 2021 U.S. Space Priorities Framework and implements Space Policy Directive-3 (SPD-3).

Signed by former President Trump, SPD-3 was the nation’s first National Space Traffic Management Policy. It outlined key roles and responsibilities. The directive assigned the administrator of NASA as lead for efforts to update the U.S.’ Orbital Debris Mitigation Standard Practices and to establish new guidelines for satellite design and operation to mitigate the effect of orbital debris on space activities.

NASA, the directive indicated, must do this in coordination with the secretaries of state, defense, commerce and transportation, and the director of national intelligence. In contrast to this coordination requirement, according to the directive, the NASA administrator must consult with the FCC chairman.

SPD-3 requires the secretaries of commerce and transportation to assess the suitability of incorporating these updated standards and best practices into their respective licensing processes—again, in consultation with the FCC chairman. In short, the FCC has an important, but consultative, role when it comes to space debris—at least for U.S. government agencies.

In 2019, NASA updated The United States Government (USG) Orbital Debris Mitigation Standard Practices (ODMSP), originally established in 2001 to address the increase in orbital debris in the near-Earth space environment. These updated standard practices for the feds included preferred disposal options for immediate removal of structures from the near-Earth space environment, a low-risk geosynchronous Earth orbit (GEO) transfer disposal option, a long-term reentry option, and improved move-away-and-stay-away storage options in medium Earth orbit (MEO) and above GEO. 

But when it comes to commercial use of space, the FCC holds the keys to the kingdom in terms of licensing. Even so, generally speaking, agencies coordinate across the aisle when creating policies that could impact each other. Imagine the surprise when in August the FCC announced a proceeding on Space Innovation; Facilitating Capabilities for In-space Servicing, Assembly, and Manufacturing (ISAM).” As defined in this Notice of Inquiry (NOI), the FCC defines missions in its purview as those “which can include satellite refueling, inspecting and repairing in-orbit spacecraft, capturing and removing debris (emphasis added), and transforming materials through manufacturing while in space.” 

Playing Nice in the Space Box

An FCC NOI is a way to ask the public to comment on specific questions about an issue to help determine whether further action is warranted. NOIs are the precursor to the agency’s Notice of Public Rulemaking (NPRM).

In this most recent NOI, the FCC specifically seeks comment on “space safety issues that may be implicated by ISAM activities, including orbital debris considerations.” 

This is not the commission’s first foray into space debris regulation. It has been reviewing the orbital debris mitigation plans of non-Federal satellites and systems for more than 20 years as part of its licensing and grants for space systems. The commission asserts its authority to regulate orbital debris derives from the Communications Act of 1934, as amended, which provides this authority to license radio frequency uses by satellites. 

In 2000, for example, it adopted rules requiring disclosure of plans to mitigate orbital debris for licensees in the 2 GHz mobile-satellite service. Those were the basis for rules applicable to all services that were adopted shortly thereafter (Establishment of Policies and Service Rules for Mobile Satellite Service in the 2 GHz Band, Report and Order, 15 FCC Rcd 16127, 16187-88, paras. 135-138). In 2004, it adopted a comprehensive set of rules on orbital debris mitigation (2004 Orbital Debris Order, 19 FCC Rcd at 11575, para. 14).

Just two years ago, it held an orbital debris proceeding, Mitigation of Orbital Debris in the New Space Age. It sought public comment on a variety of areas for rule updates, including an “active debris removal” as a debris mitigation strategy for planned proximity operations. While it concluded more detailed regulations would be premature, the resultant report nevertheless updated the commission’s satellite rules on orbital debris mitigation for the first time in more than 15 years. 

The 2020 FCC rule changes included “requiring that satellite applicants assign numerical values to collision risk, probability of successful post-mission disposal, and casualty risk associated with those satellites that will re-enter earth’s atmosphere.” Among other things, the rule changes also levied new disclosure requirements on satellite applicants related to protecting inhabitable spacecraft, maneuverability, use of deployment devices, release of persistent liquids, proximity operations, trackability and identification, and information sharing for situational awareness. 

And yet, others in the interagency balk at what some have referred to as the FCC’s continued stretching of its legal limits. The 2020 rule changes apparently stirred up considerable debate and controversy. Despite objections from the Department of Defense and other government agencies, the FCC pressed ahead. 

PNT Industry Impacts?

Fast forward to today. Comments on the FCC’s latest space-based regs focused on ISAM issues are due 45 days following publication in the Federal Register (August 5). Here is the list of topics for which the commission seeks comment. (Note the commission includes space debris as part of ISAM for purposes of this drill):

Spectrum Needs and Relevant Allocation: 
The variety of radiofrequency communications links that could be involved in ISAM missions. 

Licensing Processes in General: Any updates or modifications to the commission’s licensing rules and processes that would facilitate ISAM capabilities. 

Satellite Servicing Missions: Any additional licensing considerations unique to satellite servicing missions including servicing missions consisting of multiple spacecraft. 

Assembly, Manufacturing and Other Activities: Any special considerations in licensing of assembly and manufacturing missions. 

International Considerations: Whether and how to take into account that ISAM missions also raise the possibility of interactions between operators under the jurisdiction of multiple nations in the commission’s licensing process. 

Orbital Debris Mitigation: The implications of updated practices and approaches to stored energy and potential byproducts from in-space assembly. 

Orbital Debris Remediation: Whether and how the commission should consider active debris removal as part of an operator’s orbital debris strategy. 

Activities Beyond Earth’s Orbit: Any updates to the commission’s rules that might facilitate licensing ISAM missions beyond Earth’s orbit, including missions to the Moon and asteroids. 

Encouraging Innovation and Investments in ISAM: Ways to facilitate development of and competition in ISAM activities, provide a diversity of on-orbit service options and promote innovation and investment in the ISAM field. 

Digital Equity and Inclusion: How the topics discussed and any related proposals may promote or inhibit advances in diversity, equity, inclusion and accessibility, as well as the scope of the commission’s relevant legal authority.

Insofar as all commercial satellites may be affected by this proposal, the PNT community should engage. Will this latest FCC foray into potential space debris rulemaking protect, or lay waste to, the industry’s chances of reaching the space-high projected valuation of $8,817.3 million by 2031? Only time..and space…will tell. 

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RTCA is working to develop new standards to tackle GNSS growth and challenges. Here’s an update on the special committee’s progress, provided during a recent webinar. 

As the number of global navigation and satellite systems continues to increase, so too does the need for universal standards to ensure resilient, cybersecure and reliable navigation equipment.

A special committee (SC) of the Radio Technical Commission for Aeronautics (RTCA) has been working on developing an updated suite of dual-frequency, multi-constellation (DFMC) GNSS standards for avionics equipment with the European Organization for Civil Aviation Equipment (EUROCAE) and International Civil Aviation Organization (ICAO). Here, based on a recent RTCA webinar, “From GPS to GNSS,” we provide an update on its slow but steady progress.

Historical Standards

Let’s start with a brief review of relevant RTCA and ICAO GNSS standards to provide context for their needed updates. 

RTCA

RTCA, a not-for-profit membership association and public-private partnership standards development organization founded in 1935, develops global consensus integrated performance standards on critical aviation modernization issues. It works with, among other civil aviation authorities, the Federal Aviation Administration (FAA), to develop industry-vetted and endorsed standards that can be used as means of compliance (MOCs) with FAA regulations. 

In 1985, RTCA established SC-159, Navigation Equipment using the Global Position System. Since its inception, SC-159 has produced and maintained a suite of minimum operational performance standards (MOPS) and minimum aviation system performance standards (MASPS) for aviation equipment using GPS and its augmentations: aircraft-based (ABAS), ground-based (GBAS) and satellite-based (SBAS) augmentation systems. In 1998, RTCA published its first technical standards orders (TSOs) for avionics certification of GPS/SBAS and related antennas. In 2003, it published GPS/GBAS TSOs. 

These original RTCA standards have focused on a single GPS signal, the GPS coarse/acquisition (C/A) code that is modulated on the link 1 (L1) carrier frequency of 1575.42 MHz. With single-frequency, the receiver provides only decimeter-level accuracy, will not consistently produce a fixed position and risks frequent loss of signal. These standards have remained relatively unchanged over the years, even though the GNSS landscape has grown significantly more complex (Table 1).

ICAO 

Thirty-five years before the establishment of RTCA’s SC-159, the ICAO Navigation System Panel (NSP) adopted Standards and Recommended Practices for Aeronautical Telecommunications. These became effective and designated as Annex 10 to the Convention on International Civil Aviation (Chicago 1944). 

ICAO’s Annex 10 contains information and material for guidance in the applications of GNSS Standards and Recommended Practices (SARPs). It was not until 2001 that ICAO added GPS-related technical specifications in the SBAS and GBAS sections of GNSS requirements, through Amendment 76 to the Annex. A year later, Amendment 77 incorporated GLONASS into the Annex. Like RTCA, ICAO SARPS have thus far focused on single-frequency GPS. As with the RTCA standards, these have not been updated in decades.

New Collaborations

In 2017, RTCA signed a landmark agreement with ICAO to share standards with their respective members, for free, in the areas of communication, navigation, surveillance and air traffic management. Simultaneously, RTCA signed similar agreements with EUROCAE, SAE International (formerly named the Society of Automotive Engineers) and ARINC (Aeronautical Radio, Incorporated), to increase “the collaboration and safety of the global aviation industry,” RTCA President Margaret Jenny said. 

All of these groups, with RTCA at the lead, now collectively struggle to bring their standards up-to-date to meet the challenges of today and tomorrow.

The Space Has Changed

From these initial RTCA and ICAO endeavors to codify standards for GNSS to now, several new developments have changed the game dramatically. For one, the number of GNSS constellations and ranging sources has exploded. 

More Constellations

When SC-159 stood up, the landscape consisted of only seven GPS satellites. Today, core constellations consist of GPS (U.S.), GLONASS (Russia), Galileo (Europe), BeiDou (China) and QZSS (Japan). Galileo alone now includes 22 satellites. BeiDou, the largest single global satellite system, has double that. Standards have not kept pace.

Add to this complex landscape an ever-increasing number of commercial satellites. Naeem Altaf, IBM Distinguished Engineer and CTO Space Tech at IBM Space, said that within the next several years, a handful of companies such as Starlink, Telesat, OneWeb and Kuiper, plan to launch more than 20,000 satellites into space. This clutter has the potential to cause PNT signal interference.

Even More Signals

The modernization of core constellations adds to this complexity. GPS plans include adding three new civil signals (L5, L2C and L1C) on multiple frequencies. These additional end-state civil signals will be added to the legacy civil signal, L1 C/A or C.A at L1. They will be located within bands allocated for aeronautical radio navigation services (ARNS). 

L5, for example, will be reserved exclusively for critical requirements for aviation safety-of-life transportation and other high-performance applications. Future aircraft will use a combination of L5 and L1 C/A. GLONASS plans to engage in similar modernization efforts. Existing standards do not account for these.

Other Realities

In addition to more satellites and signals, a few other things have changed. Interference concerns relating to adjacent-band systems have emerged. Threats, such as jamming and spoofing, have increased. Geopolitical tensions have erupted.

With regard to adjacent-band concerns, in the U.S., two years ago the Federal Communications Commission (FCC) authorized Ligado Networks to use portions of the L-band for low-power terrestrial mobile satellite services (MSS), which many say will interfere with GPS. 

A Congressionally mandated review committee has completed its information-gathering but has not yet issued its final report. There remain concerns that operations close to base stations will adversely affect GPS signals in aircraft built to single frequency standards. 

Natural or human-caused signal interference or tampering also remains a significant challenge. A RAND report from May 2021, Analyzing a More Resilient National Positioning, Navigation, and Timing Capability, validated that various threats could destroy, deny or trick PNT signals. These threats range from acts of war (such as the current Ukraine conflict) and extreme space weather events that could destroy space systems to PNT terrorism, computer system failures, or simple communications breakdowns. PNT backups may also be vulnerable to these and other threats, including terrestrial systems that are susceptible to physical attacks. 

On the geopolitical front, some states have prohibited citizens and businesses from using constellations other than their own and/or mandated the use of their own constellations. For example, the European Parliament approved the eCall Regulation that requires all receivers in 112-based eCall in-vehicle systems to be compatible with Galileo and its SBAS, the European Geostationary Navigation Overlay Service.

All of these issues have converged to create new challenges for GNSS that RTCA and standards bodies must now address.

Charting a New Course

SC-159 leadership Co-Chairs Christopher Hegarty (The MITRE Corporation) and George Ligler (GTL Associates), the FAA’s Government Authorized Representative (GAR) Barbara Clark and Secretary Wes Googe (American Airlines) issued Terms of Reference (ToR) in June 2020. Not surprisingly, given the state of play, the committee’s specific guidance includes:

Addressing core constellations: GPS, GLONASS, Galileo and BeiDou. Incorporation of these foreign core constellations within equipment standards must be contingent upon multiple prerequisites being satisfied for operational use.

Addressing augmentations: ABAS, SBAS and GBAS. 

Focusing on integrity and availability. Standards must meet integrity and availability requirements for all phases of flight.

New MOPS. These will address, to the extent practicable, the threats of intentional interference and spoofing and the possibility of higher levels of adjacent-band interference in the future operational environment.

The ToR also requires that the committee’s work be coordinated with the EUROCAE Working Groups 28 and 62 and ICAO’s NSP and that the GNSS (SBAS) L1/L5 MOPS (both versions) be developed jointly with EUROCAE WG-62.

During the presentation, all SC-159 members except Googe provided insights on their next-generation DFMC avionics workplan.

At the start, Hegarty noted that all committee timelines have slipped because of the pandemic and the fact that external multi-billion dollar external core constellation upgrade schedules have also been pushed to the right. For example, the 2001 Federal Radionavigation Plan projected 24 L5-capable GPS satellites by 2014. Today, only 17 such satellites have been launched. As a result, the updated L5 interference environment report, originally due March 2021, is now projected to be completed this October. Table 2 outlines new completion dates.

Clark, the GAR and FAA’s certification, policy and innovation lead, said the committee chose to update, rather than scrub, existing standards because it was “easier…to plug and play for constellations without going back and reimaging everything.” The Amendments to Annex 10 provided a foundation for their work. Representatives from U.S., Russia, Europe, China and Japan reviewed all of these documents and validated them in late 2020.

The team revealed they have focused on dual-frequency user equipment to address many of the challenges noted. Dual-frequency can minimize errors caused by both the ionosphere (located about 50 to 400 miles above Earth’s surface at the edge of space) and the troposphere (the lowest region of the atmosphere from the earth’s surface to a height of about 3.7–6.2 miles). These atmospheric effects can slow down and scatter GPS signals as they pass through them, altering the speed and the direction of the signal. Dual-frequencies reduce these errors and provide up to a centimeter-level accuracy more quickly.

Ligler, however, acknowledged the team’s struggle to find, as he referred to it, “a good cost-to-benefit ratio,” due to the increased costs associated with dual-use frequency equipment and infrastructure. That said, he lauded the practical benefits to users, which include greater resilience with these additional ranging sources and higher levels of accuracy at the point of receivers. “Outside of areas of SBAS coverage, the benefits will increase substantially,” Ligler said. “GNSS is highly available. But in those times where there is no particular availability, we need alternatives to support graceful degradation.” He added, “We should not mandate equipment.”

The group lamented that its requirement to update interference environment descriptions for L1 and L5 have proven to be “huge tasks” that remain in progress. One member described the process as “a constant state of negotiation and understanding,” through which they have undergone “several rounds.” Without getting into specifics, the new MOPS, they said, are going to make DFMC more resilient to these interference environments. Ligado Networks participates on their committee.

The SC-159 leaders also noted that, while ASTM is creating cybersecurity standards for aircraft to address issues such as spoofing and jamming, they are looking at signals authentication methods as part of their work. Authentication can only help with spoofing, not jamming.

In closing, the group emphasized that they seek to avoid proliferation of different definitions and different requirements. ICAO’s NSP has issued a state letter acknowledging they will adopt the final standards—whatever they ultimately look like. The goal remains to have them completed and effective by 2023. 

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Will the network, which some are still fighting, be ready for a September rollout, and if so, what are the implications for GPS and the people who rely on it?

It’s been two years now since the Federal Communications Commission (FCC) authorized Ligado to use portions of the L-band for low-power terrestrial mobile satellite services (MSS), which many say will interfere with GPS.

In that time, the FCC has either denied or failed to act on motions filed by federal agencies and commercial industry. Congress stepped in, using the 2021 National Defense Authorization Act (NDAA) to pull its purse strings tight and demand some answers. 

Meanwhile, Ligado has pressed on. The company says it will launch its first systems by the end of September. It recently published a map of its preliminary coverage (see p. 14). 

An earlier attempt by major telecom companies to roll out 5G, with similar GPS interference concerns, resulted in an eleventh hour safety campaign and program delays, which I reported on for Inside GNSS earlier this year. Will Ligado become yet another chapter in the book of 5G rollout blunders? 

Looking Back to Look Ahead

The Ligado saga has played out in the public arena for more than two decades. It began in 2004 when Ligado’s predecessor, LightSquared, obtained FCC spectrum licenses for about 1,725 ground stations. 

In 2010, the company expanded its request to include up to 40,000 base stations. By 2012, the FCC halted the project after preliminary testing revealed significant GPS interference (e.g., jamming airplane receivers up to 12 miles away). That same year, the company filed for bankruptcy. 

Ligado reemerged in 2015. In the interim, even as it modified its FCC applications, additional testing continued to reveal GPS-interference problems, according to gps.gov/spectrum/ABC. 

Ultimately, on April 19, 2020, over federal and industry objections, the FCC granted Ligado a conditional and modified license (FCC 20-48) for its national MSS network. Opponents struck back with Motions to Stay (meaning to halt) and to Reconsider.

Congress stepped in toward the end of that same year. Section 1661 of the 2021 National Defense Authorization Act (NDAA) precluded the Department of Defense (DOD) from using appropriated funds for technical or information exchanges with Ligado or to retrofit affected equipment. It required the DOD to submit estimates of reimbursable costs for such a retrofit. It also directed the DOD to charter an independent technical review by the National Academies of Science, Engineering, and Medicine (National Academies). The report, the NDAA said, was to be delivered to Congress within 270 days.

In a bold counter move, as one of the final acts of the outgoing administration, in January 2021, the FCC denied the federal request (via the National Telecommunications and Information Administration or NTIA) to halt Ligado’s action on the license. The Reconsideration Petition still remains pending.

It was not until September 2021, past the Congressionally-mandated report deadline, that the Academies’ ad hoc committee (“Review Committee”) began its work. The group planned to close the record to additional evidence at the end of April.

Review of the Review

The Review Committee’s findings were already overdue when it started. That said, the group, led by Committee Chair Michael McQuade, Ph.D., Strategic Advisor to the President at Carnegie Mellon University, has been busy.

As one of its first orders of business, the Committee reviewed, and waved off, potential conflicts of interest (COI) of two of its own members, Dr. Nambirajan Seshadri and Dr. Mark Psiaki. Sehsardi holds ownership of stock in Verizon Communications; Psiaki consults for and receives research support from a communications systems design and manufacturing company that uses Iridium Communications Incs’ satellites. The COI drill appears to have missed Jennifer Lacroix Alvarez, who, according to her posted bio, “was CTO and is currently CEO of Aurora Insight, which provided Ligado Networks Inc. with consulting services in 2018.”

The team appears to have been fully formed by November 18, 2021. It aims to address these three issues: 

1. Which of the two prevailing proposed approaches to evaluating harmful interference concerns—one based on a signal-to-noise interference protection criterion and the other based on a device-by-device measurement of the GPS position error—most effectively mitigates risks of harmful interference with GPS services and DOD operations and activities. 

2. The potential for harmful interference from the proposed Ligado network to MSS including GPS and other commercial or DOD services such as the potential to impact DOD operations and activities. 

3. The feasibility, practicality and effectiveness of the mitigation measures proposed in the FCC order with respect to DOD devices, operations and activities.

In the 7 months since its inception, the committee has held 23 meetings. Almost half of its sessions (10) have been completely closed to the public, including all of its meetings after January 27, 2022, to now. 

The public record lists more than 83 documents. Ligado submissions account for more than half (43) of all the documents gathered by the Committee. The next closest in terms of volume amounts to 11 documents, from Iridium. 

The record also contains more than 17 hours of video testimony from both sides of the aisle and third parties. The lines were drawn in the lineup: Ligado, Roberson and Associates and the FCC versus the NTIA, Department of Transportation (DOT), National Advanced Spectrum and Communications Test Network, Brad Parkinson Stanford University, Garmin, Trimble, Iridium, Resilient Navigation and Timing Foundation, American Meteorological Society’s Committee on Radio Frequency Allocations, National Society of Professional Surveyors (NSPS), Helicopter Association International (HAI), Aviation Spectrum Resources Inc. (ASRI), RTCA and several commercial aviation industry organizations and experts.

Garmin’s Scott Burgett explained the concerns succinctly. “There are four internationally recognized and defined components of GPS performance that are critical to preserving the performance of a myriad of applications: accuracy, integrity, availability and continuity,” he said. “The Ligado order affects each of these. It raises troubling unanswered and safety-relevant questions for certified aviation.”

History Repeats?

Given the recent kerfuffle between the FAA and the 5G crowd over avionics interference concerns, the view presented by the commercial aviation industry merits close attention. This is especially so as the entire crewed aircraft industry, and parts of the uncrewed aircraft crowd, have challenged the FCC’s Ligado order.

ASRI’s Andrew Roy said, “Spectrum is key to how aviation operates…We have to meet higher standards. Aviation is the safest mode of travel by design. It needs to be a certainty. It’s not an ‘80/20’ thing.” He warned that while the 2018 version of Ligado’s plan seems to emit more localized interferences, “…what is still out there can have a significant effect on users, compounded by the unknowns based on conditions applied and current aviation practices.”

Bryan Lesko, chairman aircraft design for the Airline Pilots Association (ALPA), a 20 year professional pilot who is rated in 10 different jets with more than 12,000 hours of flight time, explained the importance of GPS to commercial flight. It is deeply integrated into aircraft systems, from calibrating aircraft clocks to the transponder functions that allow them to be seen on air traffic control radars and to squawk for ADS-B. It is the lynchpin of critical safety-of-life systems such as Terrain Awareness System (TAWS) for airplanes and the sister functionality for helicopters (HTAWS). That’s “why this is a really big deal and why we should really be concerned about this,” he said.

John Shea, director of government affairs for HAI said that for low altitude operations within the 250 to 500 foot diameter cylinder around Ligado base stations, helicopters would be flying blind. This rings true even around heliports covered by Part 77 Obstacle Clearances. Perhaps more troubling, about 15,000 private and aero-med heliports would not be accounted for or protected under the FCC order. These estimates may be low because, according to NASA, the FAA does not include many hospital heliports and Predesignated Emergency Landing Areas in its databases. 

The testimony revealed that these same GPS-interference concerns apply to the almost 850,000 registered uncrewed aircraft systems (UAS). Almost all of these use uncertified GPS.

The agricultural aviation community expressed concerns specific to its unique operations. These missions occur across every state. They account for 25% of all croplands (127 million acres). Scott Bertthaurer, Director of Education and Safety for the National Agricultural Aviation Association, said “If we lost GPS we would not be able to make the passes accurately.” This would have negative impacts across the $37 billion market in the U.S. for corn, soybean, wheat, cotton and rice alone.

In a March 25 return volley, Ligado essentially states all of this is much ado over nothing. It amended its license in 2018 to address the FAA’s determination that 9.8 dBW on the lower downlink would protect all certified aviation GPS devices. UAS, it said, are so high tech that “The suggestion that drones are at risk from Ligado base stations operating at 10 Watts just doesn’t hold water.” Even so, it continues, even the FAA’s recent beyond visual line of sight (BVLOS) advisory rule making committee suggested that alternate technologies should be used in GPS-denied environments. The reply admits, however, there are still issues to resolve to protect Inmarsat SATCOM devices from interference. According to the letter, Inmarsat is responsible for resolving those problems.

So, What are the Feds Doing?

Other than testifying before the committee, the feds have otherwise stayed relatively mum. 

The NTIA has been representing all federal agencies in this matter and took lead in the hearings. While the DOT, which serves as the Civil Lead for GPS, also testified, the DOD did not. Perhaps this is why the committee sent several follow-on questions directly to the DOD. Answers were due April 15. 

Getting at the heart of the issue, the committee specifically asked, “Can the DOD provide information on the availability or lack thereof of practical bandpass filters that would allow M-code receivers to function with manageably low interference from aliased versions of the permitted power in the Ligado bands?” DOD’s response: 

Repair and Replace: Military platforms have numerous GPS receivers, each of which would need to be independently evaluated for impacts. When impacts are found, the military would need to modify or replace all receivers, which would take over a decade.

Even assuming the DOD has a filter fix in the works, this will not address commercial users. The DOT remains “concerned about the millions of receivers that will experience interference.” In response to an Inside GNSS query, the DOT’s spokesperson said the agency’s “position remains unchanged” since its 2020 briefing to the FCC. Highlights include:

• Costs to federal and private users: “Tens of Billions of Dollars…Lives Lost…People Injured”

• General aviation GPS (Non-IFR) will be affected up to one kilometer

• HTAWS could be severely harmed

• The majority of civil GPS receivers are not U.S. Government devices and will not qualify for repair or replacement paid by Ligado.

The DOT also echoed the aviation community’s concerns, noting “unresolved issues relating to aviation operations and safety.” The FAA apparently still has not completed an exhaustive evaluation of operational scenarios relating to impact zones, including in densely populated areas. As noted before, the DOD said it would take about 10 years to see how filters might work. Many unknowns continue to linger.

Predicting the Future

The jury is still out, but even as early as October 2021, some members of the Committee seemed to be inclined to fault federal agencies for not meaningfully participating in the FCC process. Take, for example, these comments by Alvarez:

“I think, just in terms of lessons, the FCC had a totally transparent process that is supposed to work through issues like this. And at no point during that process did the people who are now asking me to do this study, say ‘Here is the data that we are providing to you and to the other experts in this process that will enable you to understand why we are so concerned.’ …If people participate willingly and fully in the process it can work, but all of the agencies have to be willing to do that.”

The Review Committee findings aside, there are those who believe Ligado simply won’t be able to execute by September. Given the controversy surrounding Ligado’s spectrum, it may literally be a tough sell. In a recent piece for Forbes.com, Diana Furchtgott-Roth, the DOT’s former deputy assistant secretary for research and technology, notes that front-runner Verizon has not linked up with Ligado, as anticipated. Instead, Ligado has pivoted to employing a spectrum broker, Select Spectrum, according to a company news release, to peddle its wares. She also alludes to the possibility that the FAA and other federal agencies will throw down the red card in the face of avionics interference claims as they did during the recent 5G launch.

If not, and Ligado does succeed in rolling out its transmitters, Furchtgott-Roth predicts, “This will swamp GPS in a number of places. People will not be able to use their navigation systems without interference. Firefighters and emergency workers won’t be able to get to people’s houses when they have problems. Precision agriculture and precision construction won’t work effectively. Everything depends on reliable GPS.”

And so it does. The question is: Will GPS remain reliable post-Ligado?

The post Washington View – Deja Vu All Over Again: Ligado’s 5G Network Set For Collision Course With GPS?  appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

Warfighting systems rely on GPS to provide cyber-secure and accurate positioning, navigation and timing (PNT). A recent Department of Defense Operational Test and Evaluation (DOT&E) report examined, along with all U.S. tactical weaponry, the adequacy of current GPS equipment, test strategies and plans for future operational effectiveness. It found some causes for concern.

For almost 20 years, the Department of Defense (DOD) has conducted a multi-billion dollar GPS modernization and sustainment effort, centered around M-code capability. A military-only GPS toughening solution, M-code will provide more powerful and encrypted anti-jam, anti-spoof, cybersecure signals once fully activated. Its “system of systems” requires three interrelated components to work effectively:

• broadcast-capable satellites (space), 

• an overhauled and updated ground system administer to the complex software (control) and 

• user equipment for warfighters to receive and put into theater play the PNT information (user). 

Multiple programs of record feed into this enterprise solution, across all three segments (see Sidebar).

Under the leadership of its new director, Nickolas H. Guertin, the DOD Operational Test and Evaluation (DOT&E) tracks 234 acquisition programs across the department. It provides independent, unbiased assessments to ensure the DOD has the edge necessary to protect homeland and allies, and to advance the United States’ strategic objectives. The Fiscal Year 2021 DOT&E Annual Report introduction summarizes the organizational imperative as:

“There are three Imperatives of Combat. The first is “believe in your mission;” the second is “believe in your commanders.” For the operational test community, the third imperative holds special significance: “believe in your weapons and equipment.” Our soldiers, sailors, airmen, marines, and guardians, along with DOD leadership and the Congress, count on us to tell them when and where to place that faith. We must not let them down.”

Bottom Line

According to the Report, U.S. military efforts to field jam-resistant GPS weaponry not only run behind schedule, they continue to fall behind commercial tech. Because “the lack of M-code capable receivers limits the M-code use by U.S. and allied warfighters,” branches of the Armed Forces are now sourcing directly from commercial suppliers. 

The OCX ground control system, destined to manage the GPS III constellation and M-Code-enabled military GPS user equipment (MGUE), has yet to fully and viably appear on the scene, though its initially projected delivery date has passed.

“Full control of modernized civil and M-code signals and navigation warfare functions, as well as improved cybersecurity, continue to be delayed due to ongoing development and deployment delays of the next generation Operational Control System (OCX), along with delays in the fielding of M-code capable receivers for use by the U.S. and allied warfighters.”

Delays of final software and hardware builds of MGUE Increment 1 equipment, even as Increment 2 has gotten underway, have impacted test schedules and created fears that, once finally produced and fielded, the equipment may incorporate obsolete components or be itself obsolete.

“Consequently, the Army and Marine Corps decided not to field their respective platforms with the ground-based MGUE Increment 1 card…the Services have turned to commercially available, MGUE-derived M-code receivers to continue meeting PNT requirements. Those systems will undergo operational testing outside of the MGUE Increment 1 program of record.”

Sober Evaluation

The DOT&E plans and assesses. On the planning side, its GPS Enterprise Test and Evaluation Master Plan (E-TEMP) continues to evolve. DOT&E partially revised the E-TEMP in 2021 but plans to make additional adjustments to address space-threat requirements, cyber-testing needs, and the concurrent delivery of OCX, MGUE Increment 2, upgraded Nuclear Detonation Detection System control system, GPS IIIF satellites, and OCX Block 3F.

Testing related to these plans occurred in 2020. 

OCS, COps and MCEU. The U.S. Space Force Space Training and Readiness Space Delta 12, 4th Test and Evaluation Squadron probed both operations and cybersecurity of OCS, COps, and MCEU at three different locations: the GPS Master Control Station at Schriever Space Force Base, the GPS Alternate Master Control Station at Vandenberg Space Force Base and the GPS monitoring and ground antenna facility at Canaveral Space Force Station. 

GPS III Satellite Simulator. The 4th Test and Evaluation Squadron also conducted cyber-resiliency testing of Lockheed Martin’s sat sim at its contractor facility. 

More testing looms on the horizon (see Figure 1 from the DOT&E Report). The results from current testing revealed a mixed bag.

While the report does not break down its three criteria of operational effectiveness, suitability and survivability in terms of the space, control and user segments, I have attempted to do so in Table 1. The conclusions are mine and mine alone.

The bottom line: Space and control segments remain effective and suitable, but not cyber- or space-threat survivable. The user segment comes up short on all fronts.

The M-code receiver issue presents exceedingly complex technical challenges. Dr. Mikel Miller, vice president for PNT Technologies at Integrated Solutions for Systems (IS4S) and former Air Force Senior Scientist for PNT Technologies for the AF Research Laboratory, explained: 

“A significant reason for the current lack of M-code capability is that M-code receivers need to be embedded into complex, closed, and proprietary systems of systems. This leads to a costly and time-intensive process to integrate and certify new technology into today’s existing vendor-locked proprietary PNT systems.” 

Miller also currently serves as program manager at IS4S for the Air Force’s Resilient Embedded GPS-inertial (R-EGI) project.

As would be expected, the DOD continues to work the problem hard. “The DOD’s push to acquire PNT technology using a Modular Open System Approach (MOSA)-based acquisition method will go a long way to correct this shortfall and remove the barriers that currently inhibit rapid technology insertion and refresh,” Miller said.

Moving Forward

The deficiencies are clear. The DOD lacks the necessary MGUE to widely integrate M-code cards and receivers into various aircraft, ships, vehicles, and other weapon systems. Space and control systems, while operational, need fine-tuning in terms of human-interface, cybersecurity and space environment resilience. 

The report gives several practical recommendations to the U.S. Space Force to minimize risk to warfighters and maximize probability of mission success in conflict:

• Jointly develop standardized operational test procedures for M-code PNT performance

• Plan and test GPS Enterprise against projected space threats

• Incorporate M-code and GPS Enterprise-wide testing in existing war games

• No-notice swap control stations during the OCX IOT&E test drill

• Include cyber survivability requirements in all GPS Enterprise acquisition programs

At least one GPS expert outside the Beltway thinks this plan should be more strategic. Until a centralized planning authority with control over the funding can provide cohesive policy and enact decisions, the U.S. GPS Enterprise will continue to fall behind adversaries, including China in particular. 

“There are some exceptions, but I envy the Chinese with their strong central policy over all of PNT. They are rapidly overtaking us, and in fact have passed us on several issues.” 

Complying with the DOT&E recommendations will—or would—be a start, but a larger structural overhaul may be needed. Difficult or even painful as it may be for some, only such a bellwether change in strategic operations can assure critical GPS capabilities will provide American forces the critical advantage in the complex, dynamic multi-domain operational environment.

The post Washington View: Not There Yet; DOD Report Says M-Code Capability Lags appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

A  deadlock over 5G implementation, and the potential hazards the technology would create for air traffic safety, has been at least temporarily resolved. Not all questions have been answered nor problems eliminated, however. And while radio altimeters do not use GPS or GNSS technology, they are definitely PNT devices, and this situation could create precedents for ongoing and future conflicts between telecom and PNT use of the finite radio spectrum.

Almost two years into the pandemic, virtual collaboration and connectivity remains critical to sustaining remote workplaces, school learning and personal relationships globally. The situation has accelerated the urgency of deploying 5th Generation (5G) broadband cellular networks to increase capacity to connect to more devices simultaneously with fewer lags and quicker downloads.

But deadlines for 5G implementation have been pushed, and forward movement stymied, as the Federal Aviation Administration (FAA) and a growing number of aviation industry voices warn of potential of 5G interference with radio altimeters, which measure the height of an aircraft above terrain immediately below it. This column addresses how we got here and what occurred just as this magazine was preparing for press. 

Moving FAST?

The current administration has made 5G a linchpin of its sustainable infrastructure and clean energy platform. It even proposed a $65 billion investment in “broadband for all” as part of its $1.2 trillion infrastructure bill. However, launching 5G has been a high priority in the United States for years. 

Under former Federal Communications Commission (FCC) Chairman Ajit Pai, the agency released a comprehensive strategy to Facilitate America’s Superiority in 5G Technology (the 5G FAST Plan), emphasizing the need to set aside spectrum in the low-, mid- and high-frequency bands for commercial, flexible use and unlicensed use. Its three key components included: 

• pushing more spectrum into the marketplace

• updating infrastructure policy 

• modernizing outdated regulations 

Pushing more spectrum into the marketplace has fomented the current quagmire. The FCC plans to release almost 5 gigahertz of 5G spectrum into the market, which is more than all other flexible-use bands combined.

In 2016, the FCC commenced its first-ever broadcast incentive auction to make low-band airwaves available for wireless broadband. That auction, which closed in March 2017, repurposed 84 megahertz of spectrum, 70 megahertz for licensed use in the 600 MHz band and another 14 megahertz for wireless microphones and unlicensed use. The auction netted $19.8 billion in revenue, including $10.05 billion for winning broadcast bidders and more than $7 billion deposited with the U.S. Treasury for deficit reduction.

The follow-on Spectrum Frontiers proceeding, which remains ongoing, focused on 3,400 megahertz of high-band spectrum in the 37 GHz, 39 GHz and 47 GHz bands. As part of this initiative, the FCC auctioned a total of 1,550 megahertz of high-band spectrum for purposes of commercial use. The 2018 tranche involved the 28 GHz band; the 2019 auction, the 24 GHz band. 

Congressional mandates in the 2018 Making Opportunities for Broadband Investment and Limiting Excessive and Needless Obstacles to Wireless Act (MOBILE NOW Act) directed the FCC to evaluate the feasibility of commercial wireless deployments in the mid-band at the 3.7–4.2 GHz range. In furtherance of this, the FCC has focused on the upper 37 GHz, 39 GHz and 47 GHz bands. 

In 2020, it adopted new rapid public auction rules to make 280 megahertz of mid-band spectrum available for flexible use. The FCC allocated the 3.7–4.0 GHz portion of the C-band for mobile use, set aside 280 megahertz (3.7–3.98 GHz) to be auctioned for U.S. wireless services and allocated another 20 megahertz (3.98–4.0 GHz), a guard band for existing satellite operations, to be repacked into the upper 200 megahertz of the band (4.0–4.2 GHz). 

In February 2021, upon completion of the auction of the 3.7–3.98 GHz frequency band, the FCC issued licenses to several wireless network providers conditioned on a phased deployment starting in the lower 100 MHz of the band (3700–3800 MHz) in 46 markets, with a target deployment date of December 5, 2021. In all, the telecoms paid about $80 billion to play.

The current controversy surrounds this mid-level C-Band, which is ideal for next-generation wireless broadband. Unlike high-band, it has favorable propagation characteristics. Compared to low-bands, it possesses the needed characteristics for additional channel re-use. 

The problem is that aviation radio altimeters, which measure height by timing how long it takes a beam of radio waves to travel to ground, reflect and return, operate between 4200–4400 MHz. The concern is wireless broadband operations in the 3700–3980 MHz band may interfere with these radio altimeters. 

Risk of Potential Adverse Effects

On November 2, 2021, the FAA issued a Special Airworthiness Information Bulletin (SAIB) AIR-21-18, Risk of Potential Adverse Effects on Radio Altimeters, recommending radio altimeter manufacturers, aircraft manufacturers and operators and pilots take a host of actions and voluntarily submit feedback to the FAA, FCC and National Telecommunications and Information Administration (NTIA).

Among other things, the FAA asked manufacturers to “complete analysis or testing of each model number either in production, supported, or still being employed, to determine the susceptibility to interference from fundamental emissions in 3700–3800 MHz…and the full 3700–3980 MHz band…as well as potential spurious emissions in the 4200–4400MHz band, and assess this susceptibility for compatibility with the adjacent spectrum environment.” Pilots and operators must “remind passengers to set all portable electronic devices in the cabin and any carried on the aircraft to a non-transmitting mode or turn them off.”

In November, under pressure to do something while still publicly disagreeing that aviation interference is an issue, key spectrum auction winners AT&T and Verizon delayed their launch of commercial wireless services in the C-Band until January 5. The two also agreed to take additional mitigation measures during the first six months of 2022, including generally lowering power levels nationwide on 5G cell towers and placing even more stringent limits near regional airports and public helipads.

The aviation community continued to advocate further delays. 

Agreeing to Disagree

The trade association that represents the U.S. wireless communications industry, the CTIA, has naturally aligned with the telecomms. 

In an ex parte letter to the FCC Secretary, the CTIA noted, “Nearly 40 countries have already adopted rules and deployed hundreds of thousands of 5G base stations in the C-Band at similar frequencies and similar power levels—and in some instances, at closer proximity to aviation operations—than 5G will be in the U.S. None of these countries have reported any harmful interference with aviation equipment from these commercial deployments…”

The major airlines and the aviation trade associations disagree. The Helicopter Association International (HAI) stated, “It is falsely believed that since there has been no noted 5G interference in other countries, U.S. aviation safety won’t be compromised by deployment. This statement is misleading because the deployment details and maximum power levels in a variety of other countries aren’t the same as those planned in the United States.”

HAI explained that some countries, such as Japan, where 5G is deployed up to 4.1 GHz at power levels for 5G that are at least 90% below those permitted in the U.S., have reduced the potential for aviation equipment interference. Generally, in Europe, according to HAI, 5G is deployed in the 3.4 to 3.8 GHz band, also at power levels “well below the permitted power levels in the United States” with an amount of separation from adjacent bands at 100 MHz greater than authorized in the States. France, specifically, has implemented 5G “exclusion zones” to protect public safety. Finally, Australia operates even farther away from radio altimeter RF bands at power levels 76% lower than allowable here.

In an Aviation Safety Proposal for 5G Limits, the aviation industry recommended the FCC adopt technical, regulatory and operational mitigations similar to what some of these other countries have instituted.

Major airlines such as United and Southwest indicated during a mid-December U.S. Senate Commerce Committee hearing on airline oversight that the January 5G rollout, without a viable interference fix, would negatively impact radio altimeters at 40 or more of the country’s largest airports. This, they noted, could potentially impact 4% of daily flights, resulting in delays, diversions or cancellations to the detriment of hundreds of thousands of passengers. United Airlines CEO Scott Kirby has been quoted as saying, “It is a certainty. This is not a debate.”

Helicopters also face significant challenges. Nineteen aviation and aerospace companies and associations told the FCC in August that, absent mitigations to protect radio altimeters, flexible base use stations at large medical centers with multiple heliports would “have the potential to wreak havoc on the use of heliports at hospitals and in medical centers, as well as at the countless random offsite locations where helicopters frequently land in first responder situations.” More than 550,000 patients in the U.S. use air ambulance services every year.

The Radio Technical Commission for Aeronautics (RTCA), a not-for-profit corporation that develops consensus-based recommendations on contemporary aviation issues, agrees there is cause for concern. The kicker is that it has been sounding the warning alarm for more than a year.

New Fuel on An Old Fire

In October 2020, RTCA issued Paper No. 274-20/PMC-2073, Assessment of C-Band Mobile Telecommunications Interference Impact on Low-Range Radar Altimeter Operations.

Using technical information provided by mobile wireless industry and radar altimeter manufacturers, the RTCA tested several representative radar altimeter models to empirically and quantitatively evaluate their performance tolerance to expected 5G RF interference signals in the 3.7–3.98 GHz band. It developed models and assumptions to predict the received interference levels across a wide range of operational scenarios and compared them to empirical tolerance limits. It also studied two real-world operational scenarios for civil aircraft in which the presence of the expected 5G interference will result in a direct impact to aviation safety, as part of its detailed risk assessment. 

The bottom line from its 231-page report: “The results . . . reveal a major risk that 5G telecommunications systems in the 3.7–3.98 GHz band will cause harmful interference to radar altimeters on all types of civil aircraft—including commercial transport airplanes; business, regional, and general aviation airplanes; and both transport and general aviation helicopters.” Possible consequences:

• Loss of Situational Awareness: Erroneous or unexpected behavior of radar altimeters leads to a loss of situational awareness for the flight crew and a risk of task saturation for the crew, who must compensate for the lack of reliable height information using other sensors and visual cues.

• Controlled Flight into Terrain (CFIT): Crashing the plane, which almost always results in aircraft hull loss, with a high likelihood of loss of life or severe injuries.

• Other Specific Operational Impacts on Commercial Aircraft: Radar altimeters are also used as safety-critical navigation sensors by the auto flight guidance system that feeds into systems such as traffic collision avoidance systems/airborne collision avoidance systems, predictive windshear systems, and terrain avoidance and warning systems. 

In 2019, Texas A&M University’s Aerospace Vehicle Systems Institute (AVSI), an aerospace industry research cooperative, conducted an analysis for the FCC. AVSI’s “Preliminary Report: Behavior of Radio Altimeters Subject to Out-Of-Band Interference” found that for all three altitude scenarios tested, 200 feet, 1,000 feet, 2,000 feet there was “a clear performance difference in altimeters as an increasing amount of out-of-band interference (OoBI) was received by the radio altimeters from the 3700–4200 MHz band.” 

Most of the altimeters reported broadly consistent susceptibility to OoBI power spectral density (PSD) levels until more than approximately 200 to 250 MHz of OoBI was introduced (starting at the 3700 MHz band edge). At that point, the acceptable levels of PSD began to decrease as OoBI spectrum occupancy increased toward the 4200 MHz band edge.

In February 2020, AVSI issued a supplemental report conceding that the majority of radio altimeters demonstrate some resilience to OoBI. However, the report noted, “this does not guarantee absolute protection from any signals in the 3700–4200 MHz band.” 

The White House Steps In

United’s Kirby has said the FCC and FAA “need to get in a room and talk to each other and solve the problem,” adding that the issue “cannot be solved on the back of airlines.” That happened after the White House got involved.

In mid- December, White House National Economic Council director Brian Deese met with FCC Chair Jessica Rosenworcel and Transportation Secretary Pete Buttigieg on the 5G aviation issue. Subsequent negotiations among government, aviation and telecoms produced an agreement issued on January 3: deadlines for 5G deployment, slated for January 5, were rolled back for another two weeks.

President Joe Biden stated “This agreement ensures that there will be no disruptions to air operations over the next two weeks and puts us on track to substantially reduce disruptions to air operations when AT&T and Verizon launch 5G on January 19th.”

According to FCC Chair Jessica Rosenworcel, the agreement “provides the framework and the certainty needed to achieve our shared goal of deploying 5G swiftly while ensuring air safety.”

A letter the FAA submitted to the FCC on New Year’s Eve submitted the proposed new safety framework. Under the agreement, commercial C-band service would begin as planned in mid-January with certain exceptions around priority airports, around which buffer zones would be placed until the FAA completed its assessments of interference potential and identified appropriate mitigations. The FAA said it would safely expedite the approvals of Alternate Means of Compliance for operators with high-performing radio altimeters to operate at those airports.

The parties hammered out the final terms of the deal in a document published on January 3 (www.faa.gov/sites/faa.gov/files/2022-01/USDOT%20Letter%20to%20ATT%20Verizon_20220103.pdf).

True to the original proposal, the deal required the FAA to provide a list of no more than 50 airports subject to C-Band exclusion zones. The telcos would honor their voluntary commitments to the DOT to hold off full deployments around these priority locations through July 5, after which 5G base stations would be potentially unconditionally deployed. Generally, all parties agreed to work together collegially through information-sharing and ongoing dialogue. The FAA agreed not to seek additional delays beyond July.

On January 7, 2022, the FAA announced it had selected the 50 airports for these “5G buffers,” based on their traffic volume, the number of low-visibility days and geographic location. Among others, not surprisingly, the list includes Dallas-Fort Worth International, John F. Kennedy International and Los Angeles International.

The FAA has also erected an entire webpage dedicated to “5G and Aviation Safety” (https://www.faa.gov/5g), where it lists handy resources and provides Q&As. 

Will additional concerns surface or mitigations be required? Only time will tell. Secretary Buttigieg wrote to the AT&T and Verizon CEOs on January 3, “We are confident that your voluntary steps will support the safe coexistence of 5G C-Band deployment and aviation activities, helping to retain America’s economic strength and leadership role around the world.” 

The post Washington View: 5G, PNT, and Air Safety appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

Skin in the Game – Engineers Subject Themselves to Sensor Fusion

Two Hexagon I NovAtel employees and a reporter sacrificed their bodies in the name of science by riding in the jump seat of an Aero Albatros fighter training jet during the L-39 demonstrations. Here, we get the perspectives of those brave souls and the mastermind behind the unique human aspect of this experiment.

Extreme test and evaluation (T&E) runs in the DNA at Hexagon | NovAtel. And I mean extreme.

In 2019, the team tested its IMUs in a skydiving scenario. That experience led the team to start thinking about how to introduce more complexity to their T&E through even more advanced maneuvers. Miguel Amor, chief marketing officer, said that’s when the idea was born to expose the IMUs to the power, speed and machinations of a twisting, turning, swooping, diving, gyrating fighter jet.

“We consider we have the best tech for GNSS/inertial navigation system (INS) integration,” Amor explained. “We always try to find the most aggressive applications to push the limits of the tech. The jet is the most aggressive platform for some of the attitudes we wanted to test.” 

In 2021, Hexagon | NovAtel engineers made the idea a reality. After only about six months of planning, the flights took place in Tampa in early December.

Extreme Attitude 

Among others, the engineering team’s wish list of maneuvers, including combat maneuvers, to max out the capabilities of its IMUs included: 

• Coordinated turns: forces acting on the airplane in a turn are perfectly balanced. In other words, the plane turns but its occupants are not pushed or pulled in any direction in their seats. 

• Aileron rolls: aerobatic maneuvers in which an aircraft does a full 360° revolution about its longitudinal axis

• Medium and high G turns: maneuvers that allow the pilot to make sharper turns than normal

• Immelmann turns: also known as a roll-off-the-top, an aerobatic maneuver that results in level flight in the opposite direction at a higher altitude

• Stalls: an aircraft’s angle of attack increases beyond a certain point, at which the lift begins to decrease

• Steep dives: sharp descending flight paths

• Split S: the pilot half-rolls the aircraft inverted and executes a descending half-loop, producing level flight in the opposite direction at a lower altitude

• Dynamic weave: a dramatic and demanding maneuver in which an airplane flying at a moderate speed suddenly raises the nose momentarily to the vertical position and slightly beyond vertical with an extremely high angle of attack, momentarily stalling the plane and making it a full-body air brake, before dropping it back to normal, during which the aircraft does not change effective altitude

The IMUs zipped through the national airspace over the Gulf of Mexico, wedged between the front and back seats of the jet, subjected to these maneuvers at top speeds between 333 and 510 mph. As they did, the team recorded more than just inertial measurements. They also captured the whole radio frequency (RF) spectrum. 

“Understanding the scope of the problem of the RF interference environment will help shape our solutions,” Amor noted. The team plans to use these terabytes of high-value data in future simulations, consistent with the overall objectives of the experiment. 

The first experimental objective was to show the tech could perform in a combat environment. The second objective was to illustrate the tech could be customized for commercial use, such as autonomous cars that might experience vibrations similar to the jet’s turbulence. Both of these objectives tied directly back to the company’s future PNT/GNSS road map. 

The third objective was more personal. Hexagon | NovAtel decided to put some of its employees in the jet to ride along with the IMUs as an incentive flight. Amor, who hatched this part of the plan, elaborated: “We wanted our team to have a once-in-a-lifetime experience, while doing something good for the technologies that they could share with industry.”

With these objectives in mind, the team adopted the tagline “Extreme Attitude” for the experiment. It had two meanings. From the technical standpoint, it captured the behavior of the jet’s pitch, roll and other dynamic maneuvers to which the IMUs would be exposed. 

“Extreme Attitude” also captured the spirit of the team, always seeking next-level ways to push boundaries. 

Bodies on the Line for Science

As the engineers developed the parameters of the experiment, Amor and his marketing team pushed out a lottery to all Hexagon | NovAtel employees for the jet ride-along.

“We wanted to show our employees that we are working on serious problems with real-world applications,” he noted. “The employee lottery added motivation for everybody about the importance of our mission. It helped activate a high attitude culture within the team.”

Tanner Whitmire, the company’s director of sales and support who proactively leads and assists the global sales team to grow Hexagon | NovAtel’s autonomous agriculture market vertical, was randomly selected in the lottery. Whitmire said he accepted because he is an “adrenaline junkie.” He has been racing cars for years and has broken close to 20 bones over his career. “This was a bucket-list item for me,” he said.

After Whitmire’s flight, Amor conducted a second lottery of the three engineers on site. The lucky winner was Sam Kiley-Kubik, an inertial navigation expert who has worked with the Sensor Fusion group at NovAtel for more than 12 years on system verification and system design across a broad spectrum of markets including aerospace, agriculture, defense and survey. During L-39, he provided support as a geomatic software expert to make sure the programs functioned and operated correctly. He worked with the Calgary team for months as they designed the mount for the IMUs and conducted data post-testing analysis.

“It seemed like it would be an incredible experience, a fantastic opportunity,” Kiley-Kubik recalled. “I’ve always been a fan of jets. I also felt confident going into the flight that I would not get sick, which, in the end, did not hold up.”

IMUs Survived; Co-Riders, Not So Much

Bryan Leedham, the product manager of enclosures and post-processing software at Hexagon | NovAtel, who oversees the renowned SPAN GNSS+INS sensor fusion technology, said “This was a unique integration, the first time we integrated into a fighter jet for our own testing purposes. It was exciting. We were pushing the boundaries. Stuff like this campaign is evidence that we are right there with our clients. Wherever partners are trying to position, we are literally right there with them. And whatever we could throw at the sensors, they held up.”

On the other hand, both Whitmire and Kiley-Kubik became members of the “blue bag” (airsickness bag) club. The sensors and machines outperformed the humans. 

Whitmire experienced max speeds of 333 mph, barrel rolls and 4Gs. “For me, when the plane went from extreme to leveling out, my body just did not know how to respond,” he recalled. He came off the jet holding his blue bag and looking incredibly shaken.

Even in the face of Whitmire’s post-flight condition, Kiley-Kubik still raised his hand to go next. He too, succumbed. He remembered queasiness building up early in flight, with the high G turns and then rolls. “We would do a roll and then wait for a roll. After the rolls and stall maneuver, I asked the pilot to level it out. At some point, I got sick,” he said.

Kiley-Kubik is still not sure whether he lost consciousness sometime between the Split S and Immelmann maneuvers. “I wasn’t prepared for the G load. My vision blacked out.” He remembers seeing 4.5Gs on the instrumentation before things got fuzzy. It’s no wonder. Records show he experienced top speeds of 425 mph.

Yet, despite this, both Hexagon | NovAtel employees, without hesitation, said they would do it all again. Kiley-Kubik had only one caveat. “I first would practice my lower body squeeze to hold consciousness better.” 

Not only was this experience a once-in-a-lifetime opportunity for these brave souls, the entire team learned valuable lessons that will inform future work.

Lasting Impacts

Looking back, Kiley-Kubik knew the IMUs and GNSS receivers would hold up better than he was going to. “This is what inertial tech was built to do. The test data we are going to get from this about quality levels of different IMUs and antennas, which would not be possible without doing flights like these, is going to be incredible,” he said.

Similarly, Whitmire, who before NovAtel spent more than 10 years in the corporate precision agriculture field managing operations at an active farm, already understood the challenges facing farmers and the importance of providing positioning and assured autonomy. Being able to feel the pressure and disorientation of having his “own gyros not in sync” helped him to feel and see, firsthand, what the equipment goes through. This convinced him NovAtel’s products are going to perform in the most difficult environments.

In agriculture, Whitmire explained, while speed may not be relevant (a jet at 400 mph vs. a tractor at 4 mph), the ruggedness of the solution and knowing a product can withstand the extreme conditions of a high-dynamic environment matters. The ability to continuously perform under the most harsh conditions is key, whether in a fighter jet or in a crop field. 

“Just like the jet could experience a signal outage when flying upside down with the sky out of view, a tractor could drive next to a tree line and similarly not have the visibility needed to perform,” he surmised. “Being able to handle GNSS in a jet speaks to the quality and reliability and ruggedness of our solution in agriculture and other commercial markets.”

Leedham, who has integrated GNSS and INS positioning technologies into myriad applications around the globe and has years of hands-on experience in the automotive and autonomy space, elaborated: “People might think agricultural applications, being lower and slower than a jet, may not translate. But it’s all about range and ruggedness. Some agricultural environments can mimic the jet’s motion readings due to things like the shocks from vibrations that occur over rough terrain.”

Whitmire agreed. “The jet scenario intensified what we might see in an ag application by a factor of five times or more. If we are able to ensure the solution works in an intensified situation, we know it will work in one that is less so.”

On the human side, Amor believes having employees onboard with the IMUs produced greater levels of engagement with this project than he has seen in the past. He plans to have Whitmire and Kiley-Kubik give presentations to their colleagues about their experiences to help keep the internal momentum going. Given the success of L-39, he plans to institute similar employee engagement programs in the future.

In the end, the main value of the experiment was that it showed the equipment is robust and will work, whether slow like ag or wild like jet. The team squeezed out every ounce of performance for inertial GNSS fusion. They plan to use the technical data to verify, validate and refine algorithms for fixed wing and unmanned aircraft flights, when maximum reliability is needed. 

Reporting From the Jump Seat

Having dedicated nearly 27 years in service to the U.S. Air Force as both an active duty military and federal civilian attorney, I had opportunities to experience some interesting things from an aviation standpoint. Early in my career, I got to fly up and down a chunk of the California coastline in a helicopter. I took an FBI small charter to Cuba during my deployment to Guantanamo Bay in 2004. As a more senior officer, I spiraled into Kabul, Afghanistan, lights off, during a combat landing in a cargo plane. 

Never before had I sped through the air in the jump seat of a fighter jet…until now.

As Amor hatched his plan to put some of the company’s employees in the fighter jet with its IMUs, he reached out to Inside GNSS to see if the magazine wanted to embed a journalist into the experiment.

The goal was to lend additional credibility to the human element of the experiment by allowing a reporter to go literally along for the ride, see the company’s work first-hand and provide a different point of view.

I was asked to participate because of my Air Force background. I agreed, much like Whitmire and Kiley-Kubik, because I knew this would be the chance of a lifetime. 

It was. In every way.

I arrived onsite just after Whitmire had finished his flight. I saw how tough it was on his body and how the equipment remained intact. I sat through the flight briefing with Kiley-Kubik and watched him take off, land and exit the jet, also looking a bit worse for the wear. I flew the next day. 

After having a bit of a restless night, there was definitely a part of me that was concerned about whether I would make it through the flight without passing out or getting sick. Some of the engineers were taking bets on the side.

That morning, I made sure not to eat or drink anything. I got up early, put a Dramamine patch on and made my way to the flightline. After an in-cockpit brief about how to punch out in the event of an emergency, I sat back and listened as the pilot spoke with the tower. We were ready to go wheels up.

As we rolled down the runway on that bright and sunny day, I recall thinking, “Am I insane?” And then we were off.

The initial flight was smooth. Our plan was to rendezvous with some of the Hexagon folks, who had taken a boat out into the Gulf of Mexico with the camera crew, to give them some close up “fly by” footage.

Initially, we could not find the boat. When we did, just a few minutes in, the real fun started. I remember buzzing the boat at speeds up to 337 mph, sideways. I made it through several rounds of barrel rolls, vertical ascents and a lot of circling that boat. I could feel the Gs pressing on my body and head.

It started to get to me once we switched directions, two barrel rolls in. I was breathing deeply (think Lamaze). I reached for the blue bag. My stomach squinched, but alas, Lady Luck prevailed. I never did get sick.

In the end, the equipment in that jet never flinched, but the humans did in one way or another. Overall, like my Hexagon colleagues, I would do it all again. It was absolutely spectacular.

And I did, in fact, have the time of my life.

Continue reading (Part Three)…

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