European Geostationary Navigation Overlay Service-EGNOS

 EGNOS is the European counterpart of the US WAAS 

It is a joint project of the European Space Agency ( ESA ) the European Commission ( EC ) and Eurocontrol the European Organization for the Safely of air Navigation EGNOS will augment the GPS and GLONASS systems to make them suitable for safety critical applications 

The EGNOS space segment is the set of navigation transponders on three geostationary satellites as well as the signals from the GPS and GLONASS constellation 

There are transponders on the satellites but they have no signal generators on board Instead each transponder uses a bent pipe system where the satellite transmits signals uplinked from the ground which is where all signal processing takes place 

On the ground there are about 34 Ranging and Integrity Monitoring Stations ( RIMS ) four master control centres including three reserves and six uplink station also including three reserves 

The RIMS measure the positions of the EGNOS satellites and compare their own positions from positions calculated from the GPS and GLONASS satellite signals 

The RIMS then send this data to the master control centres 

The master control centres determine the accuracy of the GPS and GLONASS signals and determine the position inaccuracies due to the ionosphere 

They send signals to the uplink stations that send them to the EGNOS satellites 

The EGNOS satellites then transmit the correction signals to GPS/GLONASS users who are equipped with an EGNOS enabled receiver 

To enable a receiver the EGNOS PRN numbers are PRN 120.12 and 126 

Operational stability for the system is expected in late 2006 

The latest position may be checked at http://esamultimedia.esa.int/docs/egnos/estb/newsletter.htm.

In Japan they are developing a similar Multi Functional Transport Satellite ( MTSAT ) system and China is understood to be testing its own two satellites Satellite Navigation augmentation System ( SNAS ) India too has proposals for their own system