Satellite Based Augmentation Systems (SBAS)

The objective of the EUROCONTROL SBAS project is to support EUROCONTROL member States in achieving the operational approval for the use of GPS augmented by a Satellite Based Augmentation System. The SBAS system covering Europe is called the European Geostationary Navigation Overlay Service (EGNOS). This project provides a co-ordination platform for all issues related to the operational validation of SBAS systems, supporting member States and encouraging a harmonised approach to operational approval throughout ECAC. It covers both the operational validation and the safety assessment.

EGNOS is being developed by the European Space Agency (ESA) in co-operation with the European Union and Eurocontrol.  The system provides additional signals to users of satellite navigation services, broadcast through geostationary satellites guaranteeing the integrity of GPS so that it can be used in support of safety-of-life services such as civil aviation. The various Member States that are investing in EGNOS intend to offer air navigation services and operational procedures that make use of the system.

In order to obtain maximum benefits from EGNOS, operational approvals need to be achieved as early as possible. The key goal of this project is to expedite the approval process by identifying all the tasks that must be carried out, who should perform them and ensuring that they are done. Each State offering EGNOS services will have to go through a safety assessment and operational approval process. A harmonised approach to operational approval throughout ECAC will be most efficient and is preferred. ESA will perform an extensive EGNOS verification campaign but this will focus on the signal-in-space as seen by a network of independent reference stations. Within the particular environment of an aircraft performing an operation, ESA will perform demonstrations but the results of these will not be applicable to the industrial consortium building EGNOS. As a result additional validation activities will need to be performed within the EUROCONTROL SBAS project to demonstrate compliance with the EGNOS Mission Requirements Document for Civil Aviation.

This part of the SBAS project is called GNSS-1 Operational Validation (GOV). The EGNOS Safety Case Team (ESCT), developing the EGNOS Safety Case, require the output from the operational validation activities for use in the assessment of the safety of operations performed using EGNOS. GOV will need to provide the evidence that EGNOS meets all the necessary performance requirements. The Safety Case will show that the use of EGNOS is safe for its intended operations based on an agreed set of assumptions. Whereas the initial focus of GOV will be on EGNOS, the project will provide knowledge, experience and tools that will be used to support future GNSS validation activities for Ground-Based Augmentation Systems for Category I, II and III precision approach and landing. The experience will also contribute to the validation of the second-generation of satellite navigation systems, in particular GPS Block IIF and Galileo.

PEGASUS provides support to SBAS.