The "Mode S" Project - Mode S Development and Experiments

The "Mode S" system is based on a logical development of the SSR (secondary surveillance radar) system currently deployed throughout the whole ECAC (European Civil Aviation Conference) area in accordance with the ECAC en-route strategy for the 2000's.

In addition to SSR functionality, the mode S system enables the selective interrogation of aircraft and the extraction of air-derived data through which new ATM functionality can be developed.


Mode S standards are defined in ICAO Annex 10, Volumes III and IV, Amendment 77. The "Mode S Elementary Surveillance" standard is being introduced in many ECAC states; its selective interrogation capability will overcome the limitations on the current SSR systems, allowing capacity to continue to increase in a safe and efficient manner.

EUROCONTROL's Provisional Council has approved the implementation of the "Mode S Elementary Surveillance" standard.

The EATMP Mode S Programme Common designs within the "Mode S" programme include:
  • POEMS (pre-operational European mode S) stations, validated against procurement specifications and specific test and evaluation tools (PTE [POEMS Test Environment]);
  • Upgraded ARTAS (ATC surveillance tracker and server equipment). Two versions are foreseen; the first one to handle "Elementary Surveillance", the second one to handle "Enhanced Surveillance";
  • Upgraded RADNET (radar network) to transmit new categories of ASTERIX mode S data; and
  • SASS (surveillance analysis support system) which will enable both the Agency and the ANSPs (air navigation service providers) to validate the performance of the mode S system.
In addition, the "Mode S" programme provides:
  • overall co-ordination of a "Mode S" implementation plan based on the plans of all participating states,
  • regulatory guidelines (specimen AICs [Aeronautical Information Circulars]),
  • operational procedures and guidelines, and
  • the "Mode S" interrogator IC (identity code) allocation process.
The "Mode S" programme is being implemented in two stages:
  1. "Elementary Surveillance", and
  2. "Enhanced Surveillance".
Within EATMP, the "Mode S" programme manages all the activities necessary to deliver the appropriate products to allow the implementation of the "Mode S" system. Between these activities, the EEC performs the "Airborne Monitoring" project, which consists of two major tasks:
  • the evaluation of transponders, and
  • the evaluation the fleet of aircraft.


The "Mode S Elementary Surveillance" system was introduced in March, 2003; there followed a transition period, which first lasted for 2 years up to March, 2005, and was then extended to March, 2007.

An important condition for the successful deployment of the "Elementary Surveillance" system is related to the inter-operability of the air-ground components. The aircraft have to be properly detected. To achieve this pre-requisite, the "Mode S" programme has put in place the "Airborne Monitoring" project to monitor the avionics and the European fleet before, and during, the implementation of Mode S.


The main objective of this project is to ensure that the majority of the fleet in core Europe have the required surveillance capability by March 2003 and during any following transition period. To achieve this aim, the project includes plans for the development and implementation of tools. The tools will be used to evaluate both the European fleet and the avionics hardware for the required "Mode S Elementary" and "Mode S Enhanced" surveillance functionality. An assessment of the evolution of the transponder equipage will be made until the end of 2009 to ensure that the mandatory process as set out in the "Mode S" roadmap is met.


The "Airborne Monitoring" project (AMP) uses a set of integrated tools and systems to record, process, and display "Mode S" radar information. These tools identify and report any possible deficiencies or issues that might prevent the correct operational use of a "Mode S" system.

To ensure that the "Mode S" coverage in the core European region is suitable, the following locations are being used:
  • Charles de Gaulle airport in France,
  • Prague in the Czech Republic,
  • Bertem in Belgium,
  • Schipol airport in the Netherlands,
  • Pease Pottage in England, and
  • Geneva in Switzerland
in co-operation with the service providers DSNA, ANS CR, Belgocontrol, LVNL, NATS, and Skyguide respectively.

All airborne type Mode S problems encountered during the period of monitoring will be analysed and resolved. Following a fault report either rectification will be sought by direct interaction with the manufacturer or airline, or the problem is resolved through the national authority.

Expected results

The target date of March, 2007, having been reached, the states involved in the "Mode S" programme are gradually deploying the "Mode S" services in their airspace.


Jose Ibanez
AMP Secretary
Philippe Brun
AMP Investigations
Roza Karadumi
AMP Monitoring
Alice Suzan
AMP Monitoring
Last validation: 08/10/2008