Space-Based Vhf, a Bridge to the Future

Communication, Navigation and Surveillance (CNS) systems are key in the provision of safe and efficient air traffic management. Although Global Navigation Satellite Systems already exist and changed Air Navigation forever, Communication and Surveillance systems are still mainly ground-based which means that in remote and oceanic areas there is limited provision of these services severely affecting the airspace capacity and flight efficiency. In 2019 The RESOLUTION 428 in the World Radio Conference (WRC-19) concluded to further study a possible new allocation to the aeronautical mobile satellite (Remote) service within the frequency band 117.975-137 MHz to support aeronautical VHF communications in the Earth-to-space and space-to-Earth directions. On December 2023, the new allocation to the ASM(R)S on the VHF aeronautical band from space was approved by the ITU in the World Radio Conference 23 (WRC-23). Making possible to provide Aeronautical Mobile Satellite (Route) Services within the frequency band 117.975-137 MHz. Space-based Very High Frequency (VHF) communications will enable to provide safe and efficient Air Traffic Management (ATM) and Data Link, bringing the service to those regions lacking ground-based infrastructure as it is provided in continental airspace. In order to provide global coverage, a constellation of satellites in different orbital planes is needed to ensure availability and continuity of the service. The solution is using space-based VHF technology in a Low Earth Orbit (LEO) constellation without introducing changes in aircraft avionics, thus having a very rapid time-to-market potential LEO constellations provide advantages compared to other orbits like GEO in terms of costs and communications. It allows a complete constellation renewal faster which lets the latest technologies to be incorporated into the constellation and the smaller distances travelled by the signal allow to reduce significantly the latency of the communications making them perfect, especially for voice service. This paper focuses on the advantages of the Space-Based VHF and highlights some of the work performed by the industry in terms of regulation and standardization as well as technical feasibility. It makes a preliminary analysis based on the doppler shift expected by bringing an already existing ground-based system to space.