Max Kingsley-Jones andKieran Daly/LONDON

THE PARTNERS responsible for developing the European Geostationary Navigation Overlay System (EGNOS) now have leases for the first navigation transponders to be flown on two Inmarsat satellites, and are considering the need for the use of a third satellite.

The EGNOS is intended to upgrade the integrity, availability and accuracy of Global Navigation Satellite System (GNSS) signals to provide the equivalent service to that of the US Wide Area Augmentation System. The partners in the consortium responsible for the development of the EGNOS, which is dubbed the Tri-partite Group (TPG), include Eurocontrol, the European Space Agency, and the European Commission (EC).

The TPG is looking at whether a third satellite will be required, to provide satisfactory coverage. Speaking to Flight International's sister publication, Air Navigation International, at the recent Global Navcom conference in Singapore, Luc Tytgat explained that two satellites - the Atlantic Oceanic Region-East and Indian Oceanic Region satellites - would leave inadequate redundancy in some of the core coverage area, primarily parts of the UK and Ireland. Luc Tytgat is in charge of defining policy in the EC's transport directorate,

It appears almost certain that a third satellite will be needed, but there are several candidates, and a selection is not believed to be close. The EGNOS' final operational capability is planned for the start of 1999, but some functions, including the ground-based integrity channel and ranging signal are expected to be available earlier.

About 30 ground-reference stations are envisaged for the core area of Europe, Scandinavia and the Mediterranean, together with probably three master stations. One of those will be in Toulouse, but the location of the others, is controversial and will not be decided until at least the end of the EGNOS-B phase later this year.

The TPG is also looking at making the EGNOS signal available to other nations, including parts of Asia, Australia, South America, the USA and all of Africa.

Source: Flight International