EGNOS: The first step in Europe's contribution to the Global Navigation Satellite System

The European Tripartite Group* - consisting of ESA, the European Commission and Eurocontrol - is implementing, via the EGNOS project, the European con tribution to the Global Navigation Satellite System (GNSS-1), which will pr ovide and guarantee the availability of navigation signals for aeronautical , maritime and land mobile trans-European network applications. On behalf o f this Tripartite Group, ESA is responsible for the system design, developm ent and qualification of an Advanced Operational Capability (AOC) of the EG NOS system. EGNOS will significantly improve the accuracy of GPS, typically from 20 m t o better than 5 m, will offer a service guarantee by means of the 'Integrit y Signal', and will also provide additional ranging signals. It will operat e on the GPS L1 frequency, and will thus be receivable with standard GPS fr ont-ends. EGNOS is one of three inter-regional Satellite-Based Augmentation Services (SBAS) that complement GPS and GLONASS. The other two are the Uni ted States WAAS and the Japanese MSAS. The EGNOS coverage area will be the European Civil Aviation Conference area, but could be readily extended to i nclude other regions within the broadcast area of the geostationary satelli tes, such as Africa, Eastern countries, and Russia. EGNOS will meet, in com bination with GPS and GLONASS, many of the current positioning, velocity an d timing requirements of the land, maritime and aeronautical modes of trans port in the European region. It is the first element of the European satell ite-navigation strategy and a major stepping stone towards Galileo, Europe' s own global satellite navigation system for the future. This article summarises the EGNOS system requirements, the overall system d esign, as well as the current status of the on-going development activities , including the EGNOS System Test Bed (ESTB).