Feasibility Analysis of GPS III Integrated With an Inertial System to Provide Cat IIIb Services
This paper describes a follow-on analysis of the potential for an integrated GPS III/Inertial Reference System (IRS) to provide CATegory IIIB (CAT IIIB) precision approach and landing services. Three different levels of GPS III capability are considered: one without cross-link (GPS IIIA), one with cross-link but without improved integrity assurance (GPS IIIB), and one with cross-link also providing improved integrity assurance (GPS IIIC). The CAT IIIB landing requirements are expressed as constraints on the vertical Navigation Sensor Error (NSE) to ensure a high probability of safe landing under both fault-free and faulted conditions. In particular the most restrictive requirement dictates the probability of missed detection of a satellite fault resulting in erroneous range measurements.