European Space Agency

ICOS - Iris Communications System Design Study Phase-A


The overall objective of the activities in the Iris Programme is to design a communication system able to support the technical and operational requirements for different airspace of interest, and to propose an infrastructure supporting the provision of communication services at the least possible cost for the airspace users. The communication standard, to be developed for use by SESAR, will be valid worldwide and compatible with ICAO provisions adopted by nations intending to mandate carriage and implementation of this new Air/Ground communication system.

The overall objective of the ICOS Project is to analyse and define a technical solution for the satellite communication standard able to meet the stringent performance requirements for Air Traffic Communication services (ATS/AOC). The Project will also carry out a cost analysis in order to propose a solution which best meets the operational requirements.


The ICOS project major outcomes will be:

  • The definition of the satellite communications system architecture and protocols that best fit the ATC/AOC service constraints.
  • A trade-off analysis to assess the proposed architecture and protocols in terms of performances (by means of analytical evaluation and simulations) and cost.
  • Finally, a preliminary development plan including all satellite communications system deployment activities necessary to ensure compatibility with the SESAR master plan needs will be provided, including the provision of support to ESA in activities such as results dissemination and initial standardization.


The current systems used for air traffic management are terrestrially based analogue systems. In most cases, they are provided on a State-by-State basis and full efficiency is inhibited by the imposition of State boundaries. This often means that duplication is provided, not for operational purposes, but because of the perceived need for each State to provide the full menu of services and facilities. Because the European air traffic management system is close to saturation, the need to replace voice traffic exchange with data traffic exchange and the increasing need to share information between stakeholders, communication technologies must evolve from an analogue to a digital system and from voice to data. In the future, the data services will be the primary means, whilst voice services will become a secondary and backup means.

In this context, the Future Radio System (FRS) infrastructure will consist of a mix of access technologies, each with its own communication elements at the aircraft side (antennas, base-band equipments, etc) and its own ground infrastructure (base stations, etc). The future terrestrial communication technologies and the satellite based ones will provide a dual-link over high density continental airspace, offering the same services. The satellite will also provide the means of communication over oceanic and remote airspace. The main advantages the satellite-based communications technology can offer are its inherent capability for broadcasting and the possibility to provide worldwide coverage, especially over those oceanic and remote regions with very simple ground infrastructure.

Satellite access network within the context of Future Radio System Infrastructure

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The Iris satellite communication system will be a multi-star type of network. Its main constituents are the space segment elements composed of one or more satellites, several fixed ground segment elements and several mobile user segment elements, namely the AES (Aircraft Earth Station) located at the satellite network edges.

Iris satellite communications system

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Even though at the beginning a centralised network architecture is foreseen, the system will be scalable to a distributed architecture, easily deployable, flexible and highly scalable to reach the worldwide coverage.

The ground segment comprises three network elements: the Network Management Centre (NMC), the Network Control Centre (NCC) and the Ground Earth Station (GES). The NMC is the network entity responsible for performing the overall management of the satellite communications system elements, defining frequency plans, establishing service policies and logging alarms and monitor information from the whole network entities (NCC, GES and AES), adopting an unified management mechanism inside the Pan-European Network (PEN).
The NCC is in charge of performing network control functions, which involves the generation of the network signalling information and the control of service policies defined by the NMC.
Finally, the GES is the network entity responsible for providing communication between the air traffic control centre (ATCC) and airline operational centre (AOC) and the aircrafts (AES) via satellite. For providing access to remote ATC/AOC, the GES will also interface with the terrestrial network.


The project will be divided into 3 phases: the requirements consolidation and architecture definition phase, the preliminary design phase and future work support.

  • Architecture definition phase: In this phase, the satellite technology will be assessed from the technical and aeronautical commercial point of view, including architecture options coming from the satellite system study. This assessment will allow consolidating the communications system requirements document (SRD) and define preliminary satellite system architecture and protocols. At completion of this phase, a communications architecture review (CAR) is foreseen with ESA in March, 2008.
  • Preliminary Design phase: this phase has the purpose to define a preliminary communications system and protocols design providing justification trade-offs for its selection. In parallel:
    • A detailed architecture of the communication system parts (AES, GES, NCC and NMC) will be carried out for specific avionics and satellite communications experts. Maturity of equipments selected, risks derived from its use, and level of standardization reached will be identified by using SESAR criteria.
    • A preliminary simulation campaign will allow the verification of some of the ATC/AOC services performances that can be reached.
    • An independent cost assessment will be also carried out by identifying development, deployment and operation costs of all the system parts.

    On completion of this phase, a preliminary requirements review (PRR) meeting will be held with ESA in June, 2008.

  • Preparation of future works Phase: this phase starts once ESA approval of the previous phase in the PRR review has been received. The purpose of this phase will be to consolidate the communications system DDP and risk mitigation outputs of the previous phase and prepare specific technical data to present to international forums for dissemination and standardization purposes. This phase will be concluded once the final review (FR) meeting has been held in July, 2008.

Current status

The ICOS project is now at the end of the Preliminary Design Phase having reached the expected level of refinement in the satellite system communications architecture and protocols initially defined in the previous Architecture Definition Phase.

Performed in the Preliminary Design Phase were also:

  • Trade-off analyses at avionics and ground segment level, and
  • Simulations at satellite physical and data link layer levels

to allow deriving system performances, identifying elements of risk and completing an initial estimation of the satellite system cost in terms of development, deployment and future operation.

A preliminary assessment has been carried out, showing the feasibility of a design meeting user requirements.
A preliminary system development plan and product tree has been issued to ensure compatibility with SESAR master plan activities foreseen for the next 10 years.

Status date

Thursday, February 5, 2009 - 12:15