In the domain of air traffic management (ATM), communication, navigation, and surveillance (CNS) infrastructure is the foundation for the provision of air navigation services. As technology evolves, so must resilience, interoperability and the inclusion of new entrants. In this second part of our story on the evolution of CNS technology, we’ll review the resilience of the CNS system, civil-military interoperability, and the progress for the inclusion of unmanned and suborbital operations as new entrants.
In the domain of air traffic management (ATM), communication, navigation, and surveillance (CNS) infrastructure is the foundation for the provision of air navigation services. As technology evolves, so must resilience, interoperability and the inclusion of new entrants. In this second part of our story on the evolution of CNS technology, we’ll review the resilience of the CNS system, civil-military interoperability, and the progress for the inclusion of unmanned and suborbital operations as new entrants.
Developing Resilience
In ATM, resilience is the intrinsic ability of a system to adjust its functioning prior to, during, or following changes and disturbances, so that it can handle required operations under both expected and unexpected conditions, according to Ruben Flohr, an expert on ATM architecture and systems engineering at SESAR Joint Undertaking in Brussels. “This means that the CNS systems need to keep functioning to an acceptable level, irrespective of atmospheric weather, space weather, cyberattacks, system component failures, etc.,” he says.
Ruben Flohr, SESAR JU
According to the Civil Air Navigation Services Organization, CNS resilience can be considered as an interconnected set of redundancies. “The industry has worked diligently to remove ‘single points of failure’ and the air traffic management system is continually monitored to detect anomalies,” says Coleen Hawrysko, CANSO’s operations program manager.
Coleen Hawrysko, CANSO
Resilience can be developed in two main ways. “Within a system, the components can be made redundant, so that there is no longer a single point of failure. An example is the voice communication systems for an air navigation service provider (ANSP), which are usually installed with triple redundancy through systems of different providers. Another example is the redundancy of power sources at an ANSP, allowing seamless switching between the public electricity net, local diesel generators as backup, and batteries as last resort,” says Flohr. “Another way to increase resilience is to make multiple technologically different solutions available for the same function. An example of this is the VOR/DME (or LDACS: L-band Digital Aeronautical Communications System, in the future) that can serve as A-PNT (Assured Positioning, Navigation and Timing) to mitigate for any outages of GNSS (Global Navigation Satellite System). In the example of datalink, the introduction of the multilink concept enables a seamless switch between all available channels. Depending on where the aircraft is, this could be AeroMACS (Aeronautical Mobile Airport Communication System), LDACS, VLDM2 (VHF Datalink Mode 2) and/or SATCOM, mitigating the risk of temporary failure of any of the individual links. In the example of GNSS, resilience is also increased by introducing the usage of multiple satellite constellations and multiple frequencies within each constellation. This mitigates any potential temporary failure of a single constellation like GPS and may also mitigate aviation collateral damage from road traffic-related targeted single frequency GPS jamming.”
Ghislain Nicolle, vice president of Air Traffic Services at Inmarsat, says the CNS infrastructure is extremely resilient and robust, and in order to provide a safety service, resilience is built in by design. “Nevertheless, as communications between aircraft and ground systems are increasing, creating more and more dependencies on those transmissions, we need to look at resilience in a more systemic way. This involves taking advantage of every available link in the communication capabilities rather than looking at individual capabilities separately,” he says. “This is what we call the multilink approach, which ultimately will enable CNS/ATM to be performed in a fully integrated manner, taking advantage of all radio links available on board.”
A CNS advisory group under the lead of the European Commission is currently exploring ways to translate the principles of resilience into a CNS evolution plan to be consistent with the ICAO Global Air Navigation Plan and the CNS roadmap of the ATM Master Plan, says Christine Berg, head of the European Commission’s Single European Sky Unit at the Directorate General for Mobility and Transport. “It should cover the short, medium and long-term evolution of the CNS infrastructure in Europe and the related transition phases to reach full implementation, enabling the synchronized implementation of airborne elements, ground capabilities and the development of space-based technologies,” she says.
Civil-Military Interoperability
The CNS advisory group is assessing how CNS infrastructure improvements should be effectively managed by identifying lessons learned, key drivers, actions and decision points that will be necessary to support the European ATM Master Plan operational objectives, says Flohr. “Furthermore, the group is in the process of identifying the issues for which EU regulatory or policy actions may be required. It is important to ensure a synchronized deployment of ground stations and avionics, the reason being that the benefits only appear once all components of such a system are deployed,” he says. “A synchronized deployment, however, is not that straightforward, as the different components need to be deployed and paid by different stakeholders, each of them requiring a positive business case for their own expenses. Another challenge is to minimize the use of exemptions from commonly agreed standards. This is, for example, relevant for state aircraft. That is why the civil-military cooperation and interoperability is within the scope of this CNS advisory group.”
Christine Berg, European Commission
Nicolle observes that in civil airspace, military aircraft are using the same CNS/ATM systems as any commercial aircraft and are subject to exactly the same rules. “They are therefore fully integrated in the CNS/ATM system. From an Inmarsat perspective, we make a point at making sure that our terminals fitted in military aircraft operate in accordance with the standards set forth by ICAO, which prevails over the civil airspace,” he says.
Inmarsat recently launched its Velaris UAV connectivity solution. The company says it will deliver new digital automation capabilities, allowing operators to send their drones on long-distance flights and to access various applications, such as real-time monitoring, to ensure safe integration with other air traffic. Image by Rainer Puster.
Civil and military airspace users have very different operational, technical, and business needs, yet use common CNS services and infrastructure, Berg points out. “This is why all stakeholders would need to be involved in the development and endorsement of a common evolution plan addressing civil and military perspectives. The European ATM Master Plan already contains a CNS roadmap, endorsed by civil and military stakeholders, defining the targeted CNS infrastructure over the next decade without entering into detail. A joint effort to define a CNS evolution plan, also involving Member States, would help to improve mutual trust and understanding,” she says. “An inclusive decision-making process is important to reconcile potentially contradictory requirements and cases where the evolution may impact stakeholders differently. Member States should try to harmonize national military requirements and plans related to CNS wherever possible to contribute to a European evolution plan covering both civil and military needs. Civil-military cooperation has strong potential to support a rationalized and resilient CNS infrastructure: data sharing will improve performance and assist in the rationalization of surveillance systems, in particular. A robust data-sharing network with relevant cyber-protection and cyber-resilience is essential.”
Unmanned Traffic
Unmanned traffic management (UTM) is the next frontier, according to Nicolle.
“UTM will be similar to military aviation, in that they will have to comply with civil aviation rules and integrate into the civil airspace. The main difference is in terms of numbers, as we are talking about much higher volumes of airborne data and equipment, for which artificial intelligence will play a major role,” he says. “This is what Inmarsat is preparing with its Velaris program. It is clear that commercial UAVs will have a positive and far-reaching impact on various aspects of society and business, ranging from cargo delivery, urban transport and surveillance to emergency services and disaster relief. However, unless autonomous vehicles and unmanned aviation are safely and securely integrated into managed commercial airspace, their true potential cannot be unlocked on a commercial scale.”
Inmarsat’s recently launched Velaris UAV connectivity solution will deliver new digital automation capabilities, allowing operators to send their drones on long-distance flights and to access various applications, such as real-time monitoring, to ensure safe integration with other air traffic, notes Nicolle. “In addition, Velaris will allow a single pilot to remotely operate multiple UAVs at scale, making operations more commercially viable and supporting the transport of people and goods in an environmentally friendly manner,” he says.
The European initiative to develop an ecosystem for the safe and secure integration of UAS is still under development. “Requirements for CNS in support of tactical separation will depend on the operational concept to separate UAS. Such requirements are not yet defined, and research is ongoing in SESAR, in particular in relation to the surveillance of UAS,” says Flohr. “As drones are operated by remote pilots on the ground, this is unlikely to have much impact on the A/G communication from UAS to ground-based UAS separation management (ATC or U-space management), with the exception of the command & control (C2) link from the operator to the drone/UAS. However, for drones this is currently not planned to be run over the aviation safety critical spectrum, which remains reserved for manned aviation. IFR traffic of remotely piloted aircraft systems (RPAS) into regular ATC is expected to follow all the CNS principles like any manned aircraft flying in controlled airspace.”
Suborbital Operations
Suborbital operations are another future entrant, and they are likely to be very different from regular air traffic. “In particular, this is due to the fact that the possibilities for tactical control are very limited at such altitudes,” says Flohr. “The type of separation control is expected to be much more based on pre-tactical or even strategic separation, and hence will have very different performance requirements on the corresponding CNS functions. An operational concept for this is not yet defined.”
One emerging challenge with both UAVs and suborbital operations is the vertical separation of these new entrants from the regular air traffic, according to Flohr. “In the near future, SESAR intends to investigate the transition from barometric to geometric [altitude measurements], considering that positioning for the UAS is heavily reliant on GNSS, and only the more sophisticated drones that are prepared for IFR integration are being equipped with barometric sensors. The SESAR research project ICARUS is looking into this for UAS,” he says. “The suborbital operations are at such a high altitude that the gradient of barometric pressure becomes too low to distinguish flight levels with the same accuracy as for regular air traffic. In order to avoid losing space by adding huge vertical buffers between traffic, it would be much more efficient to separate them by using geometric altitude, which is GNSS-based.”
CANSO has its own workgroups and task forces focused on resolving the issues of interoperability and the inclusion of new entrants, and it is also involved in many global workgroups. “CANSO also recently established the Complete Air Traffic System Council, an innovation forum composed of leaders from across the entire aviation industry (both manned and unmanned) to design a blueprint for future skies,” says Hawrysko.
“The implementation of the operational changes defined in the 2020 edition of the European ATM Master Plan can drive the evolution of CNS infrastructure, including the provision of services to new entrants (e.g. U-space services) and for higher airspace operations,” Berg says.
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