Architectures for Advanced RAIM: Offline and Online

Advanced Receiver Autonomous Integrity Monitoring (ARAIM) is a proposed extension of RAIM to aviation safety of life operations, which include approaches with vertical guidance. ARAIM would exploit the new civilian signals in L5 and new GNSS core constellations. The European Union (EU) and the United States (US) have an agreement establishing cooperation between GPS and Europe’s Galileo system. As part of this cooperative agreement a subgroup was formed to investigate ARAIM. As opposed to RAIM, ARAIM would depend on an Integrity Support Message (ISM), approved by the Air Navigation Service Providers. In this work, we describe the two ARAIM ground architectures to determine and disseminate the ISM on which the ARAIM technical subgroup has converged. In the first one, called “offline” a quasistatic ISM would be manually produced and rarely updated. We show that current GPS service performance suggests that the offline architecture could be feasible if new constellations offer a level of performance similar to GPS. In the second one, called “online”, a dynamic Integrity Support Message would be automatically updated every hour. In the online architecture, a navigation message overlay and online monitor would allow more control over nominal errors and constellation wide fault by the Air Navigation Service Provider (ANSP). At this point, the ARAIM TSG is not recommending one approach over the other and is seeking feedback on the proposed architectures by stakeholders.