The European Space Agency, the European Commission and the European Organisation for the Safety of Air Navigation (Eurocontrol) are jointly developing EGNOS, Europe's augmentation system for satellite navigation. This ECU 150 million project will provide civil GPS or GLONASS users - on land, at sea or airborne - with improved accuracy, integrity and availability. Working together, the three entities are known as the European Tripartite Group (ETG).
Yesterday, the ETG signed leases for the first two navigation transponders that will be used to broadcast EGNOS signals to users. These transponders are being flown by two Inmarsat-III satellites, located at longitudes 64 East (Indian Ocean Region - IOR) and 15.5 West (Atlantic Ocean Region-East - AOR- E).
Together they will cover not only the whole of Europe but Africa, South America and most of Asia. The IOR satellite was launched on 3 April 1996 and has been operational since 12 May. The AOR-E satellite is scheduled for launch in August.
The leases were signed in the presence of the European Commission, EUROCONTROL and INMARSAT, by the European Space Agency, France Telecom and Deutsche Telekom, the two European signatories of the Inmarsat operating agreement which had submitted the EGNOS proposal to the Inmarsat Council. The leases run for five years, with a possible five- year extension.
In its final set-up, EGNOS will provide Ranging, Integrity and Wide Area Differential Services: - The Ranging Service will broadcast GPS-like navigation signals to improve overall satellite navigation service availability. For instantaneous determination of his position, a user has to receive signals from four satellites. Neither GPS nor GLONASS can provide this at all times and all locations worldwide. EGNOS will help to fill this gap.
The Integrity Service will broadcast range error estimates for each GPS, GLONASS or EGNOS navigation signal. Without this EGNOS capability, information on abnormal performance or failure of GPS and GLONASS would take 15 minutes or longer to reach the user. The Integrity Service will enable users to decide whether a navigation satellite signal is out of tolerance before any critical situation arises.
- The Wide Area Differential Service will broadcast correction signals to improve the precision of satellite navigation. For civil users, the GPS signals are intentionally corrupted to lower the real-time precision from approx. 16 metres to 100 metres. The Wide Area Differential Service will establish a precision of 5 - 10 metres.
The Ranging Service is planned to start in 1997. The other services will be introduced gradually between 1998 and 2000. EGNOS itself will be composed of:
The space segment: two INMARSAT III transponders, later to be extended to meet the extreme safety requirements for certain aircraft precision approaches to airports.
The earth segment: Ranging and Integrity Monitors distributed over the service area will be connected to Master Control Centres, where the EGNOS signals will be generated. At least three such centres are needed to meet civil aviation safety requirements. The France Telecom's earth station at Aussaguel and that of Deutsche Telekom at Raisting will be used as primary access stations, respectively for the INMARSAT III, AOR-E and IOR navigation transponders.
The user segment: EGNOS standard receivers.
The contract for development of the ranging function was awarded to the French company Thomson-CSF in July 1995. In December 1995, the same company was awarded another contract, for detailed design of the entire EGNOS infrastructure. A proposal for subsequent EGNOS development, system verification and testing will be submitted in the second half of 1996.
Recently, the ETG and several European States have started considering proposals to extend the scope of EGNOS beyond the "Initial Operational Capability" covered by the current ECU 150 million budget and at the same time to speed up the entry into service of the "Full Operational Capability".
Within the ETG, ESA is responsible for management of all development, deployment and technical validation activities, Eurocontrol provides the civil aviation user requirements and supports the European activities for the certification process, while the European Commission consolidates all user requirements and oversees development of the EGNOS receivers and associated standardisation activities and trials, and supports the access to the INMARSAT III navigation transponders. Within the European Union, EGNOS is part of the European Union Navigation and Positioning Network as described in the Transport Trans-European Network guidelines.