Attachment A - CNSS Roadmap V0.5.pdf

Communication, Navigation, Surveillance & Security Roadmap Draft

(current as of February 11, 2026)

Kevin Witzberger, NASA Ames Research Center

Casey Bakula, NASA Glenn Research Center

Evan Dill, NASA Langley Research Center

Terrence Lewis, NASA Ames Research Center

Vincent Varouh, NASA Glenn Research Center

Table of Contents

Executive Summary

Background

Purpose of the Draft Roadmap

Goals of the Roadmap

Scope of the Roadmap

Architecture Extensible Traffic Management (xTM) Foundation Role of CNS&S in the Architecture Data Exchanges

CNS & Security

Communications Data Exchange Examples Network Architecture Considerations Spectrum Availability: A Difficult Communications Challenge

Navigation

Surveillance

Security Cyber Resilience and Contingency Management Cybersecurity Governance

Stakeholders and Proposed Roles

References

Acronyms

Executive Summary This roadmap is a target description of the requirements for communications, navigation, surveillance, and security capabilities required to support midterm urban air operations operations—a specific subset of the advanced air mobility initiative. The document focuses on the evolution of urban air mobility use cases with increasing operational tempo and higher levels of autonomy made possible by a cooperative operating environment known as extensible traffic management.

By design, this draft version is meant to solicit response towards a collaborative CNS&S roadmap that will be released sometime in 2026.

Background NASA’s Airspace Operations and Safety Program (AOSP), under the Aeronautics Research Mission Directorate (ARMD), is leading an effort to collaborate with industry and other government agencies to research new concepts and candidate requirements for new and scalable communications, navigation, surveillance, and security (CNS&S) capabilities for urban air mobility (UAM) operations.

The Federal Aviation Administration (FAA) and industry expect to conduct initial UAM operations under the existing regulatory framework (inclusive of memorandums of understanding, waivers, exceptions or new rules) and automation systems. However, when the tempo increases and/or new and novel operations commence (e.g., remotely piloted air taxis), new technologies, tools, capabilities, and automation (e.g., services) must be developed to accommodate these new operations. This shift is reflected in forward-looking architectures such as the FAA’s Urban Air Mobility Concept of Operations 2.0 [1] and NASA’s Sky for All vision [2]—both of which emphasize extensible traffic management (xTM), cooperative operating practices (COPs), and federated networks of service providers.

While advancements in airframe technology, automation, and operations concepts have accelerated rapidly, the underlying infrastructure—including the digital and physical systems enabling CNS&S—has not kept pace. Existing CNS systems rely heavily on technologies and assumptions developed for conventional aviation, many of which are not directly transferrable to complex urban environments. Examples of today’s potential challenges include radio frequency spectrum limitations in urban environments, current dependency on GPS-based solutions, inadequate surveillance technologies, and the evolving cybersecurity threat landscape.

Future CNS&S development must fit seamlessly into the National Airspace System (NAS) and allow new operators to scale and safely integrate with traditional operators.

Purpose of the Draft Roadmap NASA has drafted an interim roadmap intentionally to solicit feedback from stakeholders through a request for information (RFI) post.

Feedback from the RFI will guide future NASA-hosted workshops and inform the finalization of an initial CNS&S roadmap co-developed with industry. Once established, this roadmap is intended to serve as a strategic reference for guiding research, standards development, investment prioritization, and partnerships. Future versions will expand to address longer-term operations consistent with the Sky for All vision, perhaps including package delivery drones, unmanned aircraft systems (UAS) under 400 ft AGL, and high-altitude operations. By participating in this effort, stakeholders will help define a digitally integrated, performance-based CNS&S capable of supporting the next generation of aviation. In addition, a roadmap can be a tool to coalesce industry with common milestones to reflect priorities.

Goals of the Roadmap This interim roadmap seeks to establish the scope, key airspace assumptions, and provides a few key candidate CNS&S needs for comment. Some of these candidate CNS&S needs have been informed from prior engagements such as the August 2024 CNS&S Workshop conducted at NASA Glenn Research Center and discussions with industry, academia, and other government agencies. With feedback from the RFI, NASA expects to identify areas of consensus and areas of disagreements, as well as industry comments for missing content. Areas of consensus indicates potential future CNS&S requirements whereas areas of disagreements indicate where more research is needed. Another desired result is a timeline of required activities by stakeholder (Figure 1).

Key goals of the roadmap include:

• Identify CNS&S capability options, research needs and gaps

• Identify areas of consensus

• Identify areas of disagreement

• Identify options for roles and responsibilities between government and industry

• Identify key barriers that, if not overcome, might prevent midterm operations, as defined in the FAA’s UAM Concept of Operations 2.0 [1]

• Identify options and pathways for extensibility to mature stage operations and/or barriers to scalability

• Identify potential impacts and changes to the notional UAM architecture (Figure 2)

• Identify potential stakeholders that may have been underrepresented to this point.

Figure 1. Notional roadmap to enable midterm UAM operations from the CNS&S perspective as a result of collaborating with NASA.

Scope of the Roadmap

The current draft roadmap is limited in scope and focuses on midterm UAM operations, specifically the CNS&S capabilities necessary for the safe introduction of eVTOL and similar air taxi aircraft capable of 20-minute nominal flight times.

Midterm operations, as defined in the FAA’s UAM Concept of Operations 2.0 [1] include increased tempo of pilot-on-board UAM operations, changes to regulations facilitated by new UAM infrastructure, cooperative operating practices, airspace structures and procedures and automation, and introduction of remotely piloted in command operations

The remotely piloted passenger-carrying vehicle in an urban area use case is selected because it presents unique challenges and is expected to inform other use cases. Future CNS service providers and OEMs have shown sustained interest in remotely-piloted passenger-carrying operations—alongside higher tempo, pilot-on-board UAM operations and remotely-piloted cargo transport. The data exchanges and system actors identified for these additional use cases are expected to be subsets of those defined for UAM use case, although they may evolve based on ongoing research.

Architecture The notional architecture (Figure 2) for these operations, as outlined in the FAA’s UAM Concept of Operations v2.0 [1] and informed by NASA’s UTM and UAM research, envisions a highly cooperative, data-centric environment. This evolving framework relies on third-party provided services and capabilities—some of which may be analogous to services provided by the FAA for current users of the NAS. In this future landscape, industry—not the FAA—is expected to deliver third party services, including CNS&S services. This architecture provides a common frame of reference and facilitates research for system actors and their associated data exchanges rather than a build-to-print design.

NASA’s CNS&S roadmap will leverage this architecture and explore potentially new data exchanges, service interfaces, and system actors required to enable remotely piloted passenger-carrying air taxis operating within dense urban environments.

Figure 2. Notional UAM Architecture. FAA’s UAM Concept of Operations 2.0 [1] gives high-level descriptions of assumed functionality and roles.

Extensible Traffic Management (xTM) Foundation At the heart of the notional architecture is xTM—an evolution of the UAS traffic management (UTM) framework (Figure 3). xTM enables distributed decision-making, federated service networks, and scalable operations beyond what is feasible with today’s centralized air traffic services (ATS) model.

Figure 3. Notional Overview of Future Complementary Service Environments.

Role of CNS&S in the Architecture CNS&S systems are embedded throughout the xTM-enabled environment and may need to support some or all of the following:

• High-reliability communications across air-to-air, air-to-ground, and ground-to-ground links

• Resilient and redundant navigation in GPS-degraded urban areas

• Persistent surveillance and cooperative data fusion, including non-cooperative tracking technologies where required

• Cybersecure, performance-based infrastructure, built on zero-trust principles and aligned with the FAA’s evolving risk framework.

The architecture must accommodate a wide variety of vehicle types, altitudes, and flight rules— some operating with pilot-in-command and others under remote supervision or autonomous control. Therefore, flexibility, modularity, and extensibility are critical architectural characteristics.

Data Exchanges Safe, scalable UAM will depend on robust, timely, and secure data exchanges between a wide range of actors. Future architectures must enable real-time, distributed exchanges across a federated ecosystem of vehicles, operators, service providers, and regulators.

Communications, Navigation, Surveillance & Security

Communications UAM operations—particularly those that are highly automated or remotely piloted—will place unique demands on aviation communications systems. These include the need for resilient, low-latency data exchange between aircraft, ground systems, service providers, and passengers across a dense and dynamic urban environment. Unlike traditional aviation operations, UAM is likely to depend heavily on third-party communication networks (e.g., commercial cellular, satellite), new data exchange architectures, and federated service providers. These changes introduce new vulnerabilities, ambiguities in responsibility, and performance expectations that are not fully addressed by current aviation communication frameworks.

From an architectural perspective, these evolving needs imply new data exchanges between aircraft, vertiport operators, traffic management services, and third-party communications providers. Emerging roles—such as commercial network operators or vertiport-based integration entities—will likely be critical to enabling seamless connectivity across all flight phases. These roles may need to establish or conform to aviation-specific data handling, prioritization, and resilience standards.

Data Exchange Examples Data Exchanges Supporting Remotely Piloted Flight. To maintain safe operations with the pilot outside of the aircraft, data exchanges between the remote pilot and the aircraft must maintain the pilot’s situational awareness and their ability to command the aircraft. These exchanges, often referred to as "command and control (C2)," may include aircraft telemetry, aircraft health and status data, flight route updates, turn-by-turn commands, and the relay of sensor data captured by the aircraft to the remote pilot. During off nominal and emergency scenarios, the remote pilot may require elevated situational awareness via additional data exchanges, possibly including video feeds.

Data Exchanges Supporting Passenger-Carrying Operations. In addition to safely operating the aircraft, the remote pilot (or perhaps a dedicated passenger attendant) is also responsible for the safety and well-being of the passengers on board. During current commercial operations, flight crews hold this same responsibility, but the way this will be done for remotely piloted operations will be different. The remote pilot must be able to monitor and communicate with passengers during flight, and passengers must be able to communicate with the remote pilot, when needed. These data exchanges may require some combination of digital data, voice, and video traffic, and while these data exchanges may not be required for safe operation of the aircraft, they may be considered just as critical. Therefore, they must be accounted for in capacity planning for any proposed UAM communications candidate technology.

Data Exchanges Between UAM Aircraft. Deconfliction and collision avoidance services will indisputably make the airspace safer for all participants, and these services becomes even more critical as pilots are moved offboard and as airspace density increases. Cooperative solutions like ADS-B (automatic dependent surveillance-broadcast) and TCAS (traffic collision avoidance system) have proven invaluable for current aviation operations, but future operations, including UAM, may have more challenging cooperative deconfliction requirements. These future requirements may include the broadcast of intent information, authentication, forwarding of cooperative A2A (aircraft-to-aircraft) data to the remote pilots via A2G links, and increased bandwidth requirements due to higher density operations. New A2A technologies and data standards may be required to meet these needs.

Ancillary Data Exchanges. Remote pilots will utilize ancillary data feeds such as weather and air traffic to make informed decisions regarding the operation of their aircraft. These feeds will be available to the remote pilot via terrestrial networks. However, if the communications link to their vehicle was lost, would these ancillary data feeds be required by the aircraft to temporarily operate in an autonomous manner?

These communication demands evolve throughout the phases of flight:

• During pre-flight and surface operations, aircraft must upload and download large volumes of data over potentially different network types (e.g., WLAN, cellular), with no current standard method for verifying readiness.

• In taxi and takeoff, all communications services required for a remote pilot to operate the aircraft must be available and must be verified before takeoff is approved.

• During en route flight, CNS&S systems must manage safe separation using aircraft-to-aircraft data links for cooperative deconfliction and collision avoidance and ensure reliable transition across wide-area terrestrial or satellite networks.

• Approach and landing require uninterrupted command and control, real-time surveillance integration, and high-bandwidth cloud-based data exchanges—often in RF-challenging urban canyons.

These demands reinforce the need for end-to-end, high-reliability communications architectures that can gracefully handle degraded performance, cyberattacks, or environmental interference.

Network Architecture Considerations In addition to data exchanges between UAM actors, we must also consider the network architecture(s) that might be utilized to carry these data services. One of the most accepted network architecture concepts discussed in the UAM communications community of practice is the use of a command-and-control communications service provider (C2CSP) that connects UAM aircraft to their respective fleet operators. C2CSPs would independently operate their own terrestrial- or satellite-based network as a PSU, SDSP, or perhaps as another classification not defined in the FAA ConOps. These networks may be deployed specifically for the UAM market or operated as a UAM service on an existing communications network (e.g., cellular, LEO satcom, etc.).

There are other network architecture considerations that have not received as much attention as the C2CSP idea and warrant further discussion and research (see Figure 4). For example, A2A data exchanges could be conducted either through direct links between aircraft or by routing A2A data exchanges through a C2CSP's network. The question of whether there needs to be a direct communications link between UAM aircraft and vertiports as a means of redundancy during a loss of C2CSP service remains. Also, is there any need for direct connectivity between aircraft and PSUs to carry, for example, real-time air traffic or weather data in the event of a loss of C2CSP service?

Figure 4. UAM Architecture with Additional Network Connectivity Options, indicated by arrows with dashed lines.

Spectrum Availability: A Difficult Communications Challenge If existing or future commercial (i.e. not specifically designed for aviation markets) wireless networks can meet all UAM communications needs, access to aviation spectrum may not be required. However, if a commercial network solution is not available and new networks are required, they would likely utilize aviation spectrum bands. In this scenario, RF spectrum availability and its lengthy rulemaking processes and possible international considerations could be the most significant barrier to the development and deployment of these new networks. Further complicating this matter is the limited availability of aviation spectrum and its underutilization, which has attracted attention from industry and regulators to consider the shared use or even reallocation of this spectrum.

Navigation Navigation is foundational to many aspects of modern life and requires knowing where you are, where you want to go, and how to get there. Precise and reliable positioning technology has become essential to public safety and across all modes of transportation. Executive Order 13905 [3], “Strengthening National Resilience through Responsible Use of Positioning, Navigation, and Timing (PNT) Services”, states that “Disruption or manipulation of PNT services has the potential to adversely affect national security, emergency response, transportation, and numerous other critical functions.” This is especially true for terrestrial aerospace operations that provide commercial transportation and where inadequate PNT capabilities can lead to catastrophic events. And as flight operations become increasingly autonomous and pilot roles shift, the critical importance of PNT capabilities will likely rise [4]. Resilient navigation solutions must be tailored, or possibly invented, to meet the challenges posed by emerging UAM flight operations [5].

For traditional commercial air transportation, PNT data of sufficient quality is, or can be, provided during all phases of flight, owing to significant R&D and industry investment over many decades. PNT data is provided by high-quality sensors (often employed redundantly) and a myriad of available dissimilar PNT systems [6] (e.g., IMU/INS, VOR, DME, ILS, GNSS). For global navigation satellite systems (GNSS) in particular, various forms of augmentation systems have been deployed as well [6] (e.g., GBAS, SBAS, and ABAS). All achieve a desired required navigation performance (RNP) for a particular class of operations and at specific locations (e.g., where GBAS infrastructure is installed and maintained) [7, 8].

Unfortunately, the full complement of PNT systems and infrastructure employed for traditional commercial transportation operations will likely not be usable for all stages of flight for anticipated future UAM operations. Many of the existing PNT systems are terrestrial based [9] and become increasingly unavailable as operational altitude decreases. Low altitude flights, especially in urban areas, will not have access to the full suite of already deployed PNT systems for the entirety of their operations [10]. Some UAM operations will be conducted at a sufficiently low altitude where only inertial (IMU/INS) and GNSS-based solutions will be available, and vision-based solutions will be constrained by visibility conditions. Thus, GNSS would be the only absolute positioning capability for elements of UAM operations given today’s infrastructure and accepted PNT methods in use. Therefore, GNSS would become a single point of failure to obtain critical navigation data for portions of current UAM ConOps.

Sole reliance on GNSS for absolute positioning for UAM can be tenuous for a multitude of reasons. Cybersecurity threats, such as jamming (unintentional or intentional) and spoofing, can result in unavailable or significantly erroneous positioning [6]. Additionally, in a complicated urban environment at low altitudes, the architecture of cities can introduce a myriad of problems that detrimentally affect the performance of GNSS (i.e., accuracy, integrity, continuity, coverage, and availability). RF effects from nearby buildings such as shadowing, signal occlusion, or multipath can result in performance degradation to the point of making GNSS unusable or unavailable [6]. Despite the maturity and ubiquity of GNSS systems, these difficulties make it insufficient as a sole solution. As such, non-GNSS based alternative positioning, navigation, and timing (APNT) systems will be needed as backup or complementary services. Unfortunately, no APNT system exists that can serve as a universal backup for GNSS’s [11] positioning and navigation capabilities. This is likely the largest challenge in meeting the navigation requirements for UAM: GNSS backups/complements that can provide absolute positioning during all phases of flight.

In addition to the need for appropriate backups/complements to GNSS, there are a multitude of developments and actions that need to be taken to enable these emerging operations. From the positioning and navigation perspective, appropriate standards (e.g., RNP [12]) need to be developed that satisfy the unique requirements of UAM, including the various stages of UAM flight (e.g., takeoff and landing, enroute, contingency rerouting, etc.).Using these developed standards, an evaluation of current technologies can identify suitable and practical (e.g., size, weight, power and cost [SWaP-C]) solutions that can be implemented to satisfy the derived requirements for metrics such as accuracy, integrity, continuity, coverage, and availability. If appropriate solutions cannot be achieved with current technology and infrastructure, or if the SWaP-C is untenable, research, development, testing and evaluation (RDT&E) will need to be conducted to pursue adequate solutions. This RDT&E would likely include exploration into ways to improve GNSS performance [6, 13, 14], and its responsible use [3], data exchanges and connectivity for UAM infrastructure, as well as non-GNSS based APNT systems [11].

Surveillance NASA expects to lean heavily on experts in industry and other government agencies to provide content.

Security As previously noted, the proposed xTM architecture shifts from FAA-managed services to a decentralized, third-party model that will include CNS services. To support high-density, low-altitude operations by novel entrants, the architecture must leverage scalable automation and advanced technologies. Cybersecurity is a foundational element of this future vision and must be integrated throughout CNS and the xTM environment. Ensuring a secure and efficient airspace depends on addressing the unique cybersecurity challenges of xTM.

The xTM environment will be highly connected and involve real-time data exchange between ground infrastructures, vehicles, and cloud-based services via multiple third-party providers.

This high degree of connectivity introduces a broad attack surface and complex cyber-physical risks; current airworthiness hardware and software cybersecurity techniques do not accommodate the advanced aerial mobility platform [50].

Given this landscape, two critical cybersecurity challenges, 1. cyber resilience and contingency management and 2. Cybersecurity governance, must be addressed to enable midterm operations.

Cyber Resilience and Contingency Management

As in many fast-moving industries, the rapid development of xTM vehicles and services increases the risk for skirting cybersecurity [51]. It is frequently viewed as a barrier to innovation—too costly, time-consuming, or simply someone else’s responsibility. This mindset leads to cybersecurity being bolted on late in the process, resulting in vulnerabilities and costly redesigns. For example, merely stating that xTM technologies will use IP protocols and thus will utilize encryption is simply not a viable solution in a domain where safety, trust, and real-time integrity are critical.

Effective cybersecurity requires thoughtful design choices, including considerations for what needs encryption and latency-sensitivities, and must be embedded into the design, development, and operational lifecycle of all xTM technologies. It should follow secure by design [52] principles and incorporate models like Zero Trust from the start.

Resilience must be central to the xTM architecture. This means utilizing technologies that ensure layered defenses, continuous monitoring, and adaptive security practices [53]. Given the inevitability of cyber threats—especially in semi- or fully autonomous operations—systems must be built to detect, isolate, and quickly recover from attacks autonomously. Cyber-resilient architectures for xTM and ancillary CNS systems and services must maintain critical functions even while under attack. These capabilities are essential for operational continuity, safety, and public trust, and they lay the groundwork for future integration of AI and other advanced technologies.

As aviation becomes increasingly digital, traditional cybersecurity approaches focused solely on perimeter defense and static threat models will no longer suffice. “Current cybersecurity approaches that rely on threat analysis, maintaining impenetrable boundaries, and focusing primarily on information security will not be adequate for UAM missions involving learning and adaptive platforms” [50]. A new, integrated approach is essential for the success of xTM.

Cybersecurity Governance In 2024, NASA hosted a CNS&S workshop with industry, federal agencies, and internal teams to gather feedback on communication and security strategies for the future UAM environment.

The workshop explored communication needs, proposed an xTM security architecture, and discussed associated threats, vulnerabilities, risks, and mitigation strategies. While relevant, desirable aspects of the notional architecture received broad support, a key point of contention was cybersecurity governance—specifically, who should manage it and what form it should take.

Clear definitions are needed for the cybersecurity standards that UAM stakeholders must follow.

Establishing a common set of cybersecurity principles and governance is essential. Without enforcement, best practices risk being selectively applied based on cost or convenience which can ultimately undermine overall system security.

Lastly, given the complexity, connectivity, and safety-critical nature of UAM, collaboration across organizations is vital. In the cybersecurity context, this includes structured information sharing—something that effective governance can help facilitate.

Collectively, these actions would strengthen trust and safety, ensure broader coverage, and support a more dynamic, risk-based approach to cybersecurity. Neglecting to meaningfully integrate cybersecurity and resilience will lead to cascading impacts on safety, operations, and public adoption.

Stakeholders and Proposed Roles The successful implementation of UAM operations requires a coordinated "whole of community" approach where stakeholders fulfill complementary roles. At the CNS&S workshop held in August 2024, NASA received feedback on the desire for the agency to fill an existing void by serving as a catalyst between the federal agencies, UAM operators, service providers, standards bodies, and others. NASA is uniquely positioned to lead the development of strategic artifacts, such as a roadmap, that can be used to propel the community towards working together to address the challenges outlined in this roadmap. In addition to this leadership role, NASA will also leverage and contribute in-house technical expertise.

The FAA will maintain its critical regulatory and safety oversight functions while developing performance-based standards that enable innovation. Industry partners will drive technology development and operational concepts based on business requirements. Other government agencies, including the NTIA and DHS, will contribute expertise on spectrum allocation and cybersecurity frameworks respectively. Standards development organizations (SDOs) represent a critical bridge between regulatory requirements and technical implementation for UAM operations.

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Acronyms Acronym Definition A2A Aircraft-to-aircraft AAM Advanced air mobility ADS-B Automatic dependent surveillance-broadcast APNT Alternative positioning, navigation, and timing C2 Command and control CNS&S Communications, navigation, surveillance, and security ConOps Concept of operations COP Cooperative operating practices FAA Federal Aviation Administration GBAS Ground-based augmentation system GNSS Global navigation satellite system GPS Global positioning system NAS National airspace system PNT Positioning, navigation, and timing RDT&E Research, development, testing, and evaluation RFI Request for information RNP Required navigation performance SWaP-C Size, weight, power, and cost TCAS Traffic collision avoidance system UAM Urban air mobility UAS Unmanned aircraft system UTM UAS traffic management xTM Extensible traffic management https://www.helpnetsecurity.com/2021/11/05/not-effectively-stopping-cyberattacks/ https://www.cisa.gov/securebydesign https://doi.org/10.2172/1906953