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EGNOS Architecture
| EGNOS | |
|---|---|
| Title | EGNOS Architecture |
| Author(s) | GMV. |
| Level | Basic |
| Year of Publication | 2011 |
The goal of EGNOS (European Geostationary Navigation Overlay Service) is to augment the [GPS Introduction|GPS]] in order to improve the navigation performances in terms of accuracy and integrity (with the required levels of availability and continuity of service) over the European Civil Aviation Conference (ECAC) Region and to be expandable over neighbouring regions.
These augmentations are obtained by providing a GPS-like Geostationary Ranging service (R-GEO), by broadcasting precise Wide Area Differential corrections to correct for GPS, GLONASS and GEO orbit and clock errors and also to correct the ionospheric delays affecting the signal paths to the users. The complex message broadcast by EGNOS GEOs also include Integrity data which allow to bound the remaining errors with a high level of confidence. EGNOS has deployed its Advanced Operational Capability (AOC) using two existing INMARSAT-III navigation transponders (AOR-E and IOR-W) plus a navigation transponder on board of Artemis satellite.[1]
The EGNOS architecture is very complex and highly redundant. It is composed by 47 elements deployed onto 41 sites in 22 Countries. EGNOS has been designed to meet the international SBAS standards and performs the following tasks:
- Collect GPS/GLONASS/GEO signals and data.
- Estimate the integrity data and WAD corrections for the service area.
- Transmit to the users, via the GEO satellites, a GPS-like signal, augmented with integrity and correction messages.
- Verify the correctness of these integrity and correction messages.
Architecture Overview
The EGNOS system is directly decomposed in its four segments, a Ground Segment, a Space Segment, a User segment and a Support Segment:[1]
- The Ground Segment is the real-time part of EGNOS. It computes precise differential corrections as well as the GEO ranging and makes all these information available to users through a broadcast by the Space Segment.
- Space segment, using three GEO satellites, provides redundant data transmission channel to broadcast toward EGNOS users messages containing differential corrections with the associated integrity information. The GEO satellites additionally provide GPS-like ranging signal that is permanently steered and synchronised by the ground segment.
- User Segment is made of EGNOS receivers that enable EGNOS users to accurately compute their position.