EGNOS back-up integrity based on NLES autonomous integrity: the mini-GIC solution

Javier Ventura -Traveset, Isabel Neto, Manuel Toledo, S Gmv, Isaac Newton, P Tres, Cantos, Spain Madrid
The EGNOS (European Geostationary Navigation Overlay System) system is being developed in Europe to provide GPS (and GLONASS) regional augmentation services to aviation, maritime and land users ([3], [4]). The EGNOS System is being designed to serve the needs of all modes of transport in the European Region, namely: Civil Aviation; maritime and in-land water navigation and docking; and rail and road transport and traffic monitoring systems. For civil aviation, EGNOS Advanced Operational
more » ... Operational Capability (AOC) will provide a primary means service of navigation for en-route oceanic and continental, non-precision approach and CAT-I precision approach within the ECAC (European Civil aviation conference) area. EGNOS Full Operational Capability (FOC), which will follow the AOC phase, will ensure sole means operation. The EGNOS AOC architecture is very robust and it is designed in such a way that integrity will always be guaranteed. For EGNOS AOC, though, under some very unlikely extreme failure conditions (e.g. in the case of SW common mode failure in all EGNOS Central Processing Facilities --CPFs--), although the system will be kept safe (integrity guaranteed), continuity of service may not be guaranteed. The probability of those outage situations is very low. Yet it is expected to remove those in EGNOS FOC (several solutions have been proposed by the EGNOS industrial consortia). Aiming at contributing to the EGNOS FOC debate, this article introduces the concept of mini-GIC, as an elegant and very simple way of filling those unlikely outages, i.e. guarantying an operational service even under these extreme events. The EGNOS mini-GIC concept is based on the idea that, in extreme failure conditions of the EGNOS AOC System (e.g. a SW common mode failure in all EGNOS CPFs), and in order to ensure continuity of service, each navigation uplink GEO station (NLES) may autonomously assess on the integrity of visible GPS satellites. A rough integrity information may then be provided by combining that partial NLES information in a single message which is forwarded to the users (backup integrity). This paper discusses the mini-GIC performance as well as some related architectural issues. 1