Methods of Integrity Risk Computation for ARAIM FDE

Abstract : Advanced Receiver Autonomous Integrity Monitoring (ARAIM) is under development as a potential means to achieve global Localizer Performance with Vertical Guidance (LPV) approach operations with a decision height down to 200ft. In addition, early improvements to support operations requiring only horizontal guidance are expected. ARAIM takes benefit of dual-frequency measurements to remove large ionospheric errors and the threat they present. Furthermore, multiple constellations are to be supported to enable improved geometry and garner the performance required for the more stringent approach operations. Whilst ARAIM will not depend upon a ground segment with a dedicated real time communication channel in the way that SBAS and GBAS do, an Integrity Support Message (ISM) is to be provided to characterize the satellite and constellation nominal measurement and threat models. The ultimate means and frequency of ISM dissemination is yet to be determined. Whilst this remains one of the key institutional decisions to be made, some technical questions are yet to be fully addressed and in particular surrounding the nature of the fault exclusion process and its associated integrity risk. This paper addresses the latter element and proposes an improved technique to determine an upper bound on this risk. This is achieved whilst also strengthening the mathematical link between the solution separation based (A)RAIM and the parity domain approach, following on from the work presented in [1]. Performance benefits are shown in the case of canonical examples and operational service volume simulations.