EGNOS Future and Evolutions

EGNOS
Title	EGNOS Future and Evolutions
Author(s)	GMV.
Level	Basic
Year of Publication	2011

The European Commission (EC) intends to ensure the future of EGNOS services for GPS L1 legacy users until at least 2030. In this context, the budget should be secured to operate the system and manage the system obsolescence. Moreover, major EGNOS system evolutions towards a multi frequency and multi constellation configuration are currently being assessed with the objective to take an implementation decision by 2013 and to have them operational by 2020.

A technical assessment of the potential EGNOS evolution, EGNOS V3, is currently done by the European Space Agency within the European GNSS Evolution Programme.

EGNOS Mission Roadmap and EGNOS versions

The European Parliament and the Council have allocated the management of the EGNOS programme to the European Commission.. On the other hand, ESA is the technical player responsible for system design and development, and ESSP is the service provider.

The European Commission, in its role of entity in charge of the management of the EGNOS programme, is defining the roadmap for the evolution of the EGNOS mission. This roadmap should cope with legacy missions and new missions:

• 2011-2030: En-route / NPA / APV1 / LPV200 service based on augmentation of GPS L1 only. The SoL service is being offered by EGNOS from early 2011 on a regional basis and this will be guaranteed up to 2030 in compliance with ICAO SBAS SARPS. In order to grant this timeframe, it is still needed to achieve a programmatic committment based on secured funds.
• 2018-2030: It is planned that EGNOS will experiment a major evolution in 2018, EGNOS V3, including the fulfilment of the SBAS L1/L5 standard, which is currently under definition. Beyond the dual-frequency augmentation, there is the possibility to evolve towards a multi-constellation concept. One of the main aspects to determine is wheather or not the new SBAS L1/L5 will support dual constellation, and if the European Commission will include the augmentation of GPS alone or GPS and Galileo as part of mission of the next EGNOS major version.

To support these mission roadmap, EGNOS needs to evolve. This evolution is divided into minor updates of the current EGNOS version, EGNOS V2, and a major evolution leading to the provision of new services, EGNOS V3.

The minor evolutions in the current EGNOS version are performed in a regular basis at an approximate pace of an update per year, and aim at solving infrastructure obsolescence issues, at supporting the LPV200 service beyond APV1 and at improving the operation of the system.

The major evolution requires a full dedicated enginneering cycle starting from the definition of the mission of the system highly coupled with a technical feasibility analysis in coordination with the evolution of the SBAS standards.

As regards the consolidation of the new EGNOS missions, it is expected to take a decision on the main open points in late 2012. The European Commission is in the process of setting up a consultative group of GNSS experts called the Mission Evolution Advisory Group (MEAG). MEAG aims at providing EC with independent advice and recommendations on potential evolutions of the mission objectives and the service definitions for the European satellite navigation programmes Galileo and EGNOS. The group is expected to critically assess changes of both user needs and scope of space-based PNT, both on European and international scale. Changes on the mission and service requirements for the Galileo and EGNOS programme will be analysed too, proposing suitable updates of the mission and service baseline. MEAG members include experts from GNSS user communities, GNSS industry sectors, academia, national space agencies and other recognized experts from Member States. The MEAG meets on a regular basis with an indicative number of three meetings per year. The expert group may establish on an ad-hoc basis Working Groups to provide specialist support as required to carry out its activities. The MEAG shall further record and report its work results and recommendations on a yearly basis to the Commission.

As for the EGNOS technical evolution, ESA is managing several activities within the European GNSS Evolution Programme.

The European GNSS Evolution Programme

The European GNSS Evolution Program was defined in 2006 by ESA to address the second generation of the EGNOS and Galileo systems.

The first phase of this program included a study about the concept of Multi-Constellation Regional System (MRS) over 2007-2009. An outcome of this work was a generic MRS architecture baseline that should be considered as a candidate target for V3 functional architecture and further assessed and refined within the EGNOS V3 phase A definition study.

The second phase of EGEP on SBAS (over 2010-2011) is devoted to the consolidation of system evolutions and to field testing. It is broken down into three main parts:

• EGNOS V3 Definition Phase, aiming at preparing the new EGNOS system generation to address obsolescence issues, robustness improvement, new services, standard evolutions, coverage extension, use of new broadcast means, with a view to start preparing the EGNOS V3 implementation phase at a later stage (post 2013).
• Experimentations with several Test-Beds based on using a complete or partial SPEED infrastructure.
• SPEED related activities in order to procure, install, operate and maintain the SPEED V1 engineering platform allowing to run the above tests and to develop an upgraded version of SPEED V1 platform to implement new features in the Host Structure of SPEED necessary to support a second phase of experimentations (at a later stage).

These Test-Beds have the following objectives:

• HIS (High Integrity Service) to develop one system Test Bed (based on SPEED) to engineer and experiment high Integrity (similar to Safety Of Life for multi-modal applications) and

authentication (authenticated GEO signal + GEO ranging/UDRE)

• ARCTIC to experiment maritime and aeronautics services in northern latitudes.
• HPS (High Precision Service) to demonstrate and generate interest in an HPS service (with integrity), based on, first GPS and later GPS+GALILEO
• MLU (MRS Land User service) to investigate, demonstrate and develop new services for Land Users: Proof of Position, Authentication and Emergency Services.

OLD

The European Space Agency (ESA) is currently completing the final qualification stages of the European Geostationary Navigation Overlay Service (EGNOS) and is in the process of developing the GALILEO system, a self-standing 30 satellite constellation for global satellite navigation. The European GNSS Evolution Program was defined in 2006 by ESA to address the second generation of these systems.

As part of the evolutions considered, three more RIMS are scheduled to be deployed in Agadir (Morrocco), Athens (Greece) and Alexandria (Egypt) providing the extension of EGNOS signal coverage to northern Africa.

Besides, processing improvements are scheduled for the EGNOS signal, including iono algorithm pre-processing fine tuning. Finally, the deployment of EGNOS v3 is scheduled to cover the Multi-Constellation Regional System (MRS) concept and implement a GPS L5 augmentation service.

GNSS Evolution program FrameWork

As part of the GNSS Evolution program, ESA called for two parallel studies in the scope of a Multi-constellation Regional System (MRS), that is, the evolution of the EGNOS concept to cope within a multi-constellation environment (Galileo, GPS, others GNSS constellations), and a multi-frequency scenario (GPS L1, L5; Galileo L1, E5a, E5b, E6, etc..).

With this multi-constellation scenario, and with multiple frequencies available for navigation, the wide area regional augmentation systems must evolve and need to be adapted to this new behaviour. The next generation of the regional augmentation systems will not only be an adaptation of the architecture to the current state-of-art but also an important change of the concept. Considering only the new approach to the ground segment, this paper presents the alternative implementations of the integrity concepts, the different broadcast means and possible architectures analysed.

MRS mission is a natural evolution of a regional system, such as EGNOS, considering the advent of new constellations and new frequencies in the GNSS panorama. As GNSS modernisation plans are today under definition and other studies are assessing possible evolutions of GNSS systems beyond 2015, the MRS Study is focused on the 2012-2015 timeframe.

EGNOS Evolution Features

As a multi-constellation, multi-frequency and multi-broadcast system, the MRS system shall not only continue providing an SBAS service to L1 users but shall also cover GPS L5 and Galileo L1 and L5/E5 users. The system evolution considers different dissemination channels, including the SBAS GEO (Geostationary Earth Orbit) L1 and L5 channels, Galileo MEO (Medium Earth Orbit) ERIS (External Regional Integrity System) channels and other satellite or terrestrial means to be defined according to regional or user defined interests (e.g. SISNET, LORAN-C, etc).

The high level objectives defined by the Evolution program are the following:

• To maximize European ‘User’ Performance when combining EGNOS and Galileo infrastructures, allowing SoL service provision.
• To optimize cost of operation and infrastructure of both systems when combined in MRS, keeping independence of both systems and ensuring robustness against GNSS failures.
• To provide mainly an integrity service for safety of life aviation or liability critical applications.
• To provide regional GPS and Galileo integrity and continuity by using MRS and Galileo.
• Understood as a multi-constellation (GPS/GAL) multi-frequency (L1/E5) and multibroadcast (GEO, MEO and others) system, to provide a service assuming all combination of mono/multi constellation and mono/multi frequency users.
• To provide better availability of SBAS integrity for regions of poor GEO reception through additional Galileo ERIS MEO broadcast of integrity information or other means.
• To enhance ionosphere monitoring accuracy by adding Galileo observations or decrease number of RIMS.
• To broadcast new messages: Message Type 28 is one of the most solid candidates to be included a new message broadcast by EGNOS in future evolutions. This message contains matrices for two satellites per message, and each message is broadcast at the same rate as the long-term corrections (Message Type 25).

Benefits and New Services

Forthcoming constellation deployments (GALILEO, GLONASS M, COMPASS), combined with GPS, will enhance EGNOS performances as well as its robustness. Besides, they will allow the development of new services. These services have been studied in the frame of the MRS (Multi-constellation Regional Augmentation System) concept and include: Safety Of Life service (SOL), Open Services (OS), Liability Critical Services (LCS), Commercial Data Dissemination Services (CCDS), detailed below:

• Enhance User performances (SOL, aeronautical users): On the one hand, the existence of more signals belonging to new constellations will provide more information about the ionosphere and consequently better performances, specially under ionsopherically degraded conditions (forecast for the coming years here). On the other hand, the provision of ionosphere measurements would reduce the number of RIMS required, lowering the cost of RIMS maintenance and reducing the EGNOS infrastructure cost.

Moreover, given the current SBAS standards that permit the augmentation of up to 51 satellites, the system could take advantage of the increasing number of constellations and satellites to provide increased continuity and availability with enhanced accuracy and higher navigation robustness to face signal blockages.

• New services (OS, LCS, CDDS): EGNOS Evolutions consider the provision of new services that may reach communities that cannot benefit from current EGNOS signal due to environmental constraints. For this purpose the EGNOS system has studied to take the following steps:
  • Broadcast of EGNOS data through alternative channels.
  • Broadcast of new parameters.
  • Provision of authentication capabilities for Liability Critical Services (LCS).

System Architecture

Future EGNOS architecture shall be able to provide the new EGNOS features and services considered.

One important consideration when designing the EGNOS architecture is to define whether if EGNOS and Galileo should be independent. In this case, any event leading to performance degradation in one of both systems shall not impact the other system performance and, in the event of such an occurrence, switching from one system to the other would be feasible.

This consideration results in high level architecture designs that suggest:

• Dense collecting stations network (stations spread inside and outside Europe).
• Hardware, Software and conception diversification (including monitoring stations, processing facilities and station networks).
• Mixed EGNOS communication channel (including GEO and MEO satellites).