Surveillance Data Distribution System

A state of the art solution for providing added value surveillance data handling services.

The EUROCONTROL Surveillance Data Distribution System (SDDS) is a versatile, high-performance communication gateway that provides value-added services for the safe and secure distribution of Surveillance information in (but not limited to) EUROCONTROL’s All-purpose structured surveillance Information exchange (ASTERIX) format.

SDDS enables Air Navigation Service Providers (ANSPs) to exchange surveillance data in an efficient manner, contributing to the reliable and efficient operation of the pan-European ATM network.

Acting as an interface between the external world and the ATC Centres, SDDS is meant to protect the ATC systems from deficient data coming directly from sensors or from other surveillance data exchange networks. It is capable of:

  • checking the surveillance data flows for syntactic and semantic errors at ASTERIX level;
  • providing firewall services, protecting the downstream systems from possibly harmful data streams;
  • filtering out data that may cause processing problems (duplicated messages, ADS-B server, BDS-Swap, overload situations);
  • acting as ADS-B Server, concentrating target reports received by multiple ADS-B Ground Stations into a single source.


SDDS enhances safety, security and interoperability by providing the following features:

ASTERIX data format conversion

ASTERIX data format conversion is an interoperability feature allowing the introduction of technologies such as ADS-B and Multilateration in the surveillance infrastructure, without having necessarily to update the end systems at the same time.


The static-filtering capabilities allow data streams to be tailored to User's needs, applying a wide range of filtering criteria (e.g. geographical filter, surveillance technology filter, specific SSR Mode 3/A code ranges, etc.), while dynamic-filtering capabilities help prevent uncontrolled loss of data due to overload. The SDDS uses a lean publish/subscribe mechanism to manage the connections to the provided services, thereby facilitating interoperability and reducing configuration effort. Such a mechanism also ensures that Users can only access data for which they are authorised.

ADS-B Server

The ADS-B Server function is responsible for the processing of ASTERIX CAT021 messages, provided by various ADS-B Ground Stations. It can be used to reduce the data load on other surveillance components either filtering out duplicated messages related to the same Target Address (data-driven mode) or merging the information delivered in multiple messages – related to the same target – in one single message, to be served at a defined pace (periodic mode).


Gateway functions allow the simultaneous use of a wide variety of communication protocols. These functions are not restricted to surveillance data: indeed SDDS can be used in transparent mode to distribute any other type of data. An automatic switchover function ensures data availability in case of data source loss, activating the connection to a backup source.


Safety-related features include a high availability hardware platform, alternative data path selection, data syntax and range checks, static and dynamic filtering.


Security-related features include a top-level architecture separating payload and management flows, as well as a clear segregation of the inter-centre and intra-centre communications.

SDDS Use-Cases

Inter-centre distribution

SDDS was primarily developed to cover the inter-centre distribution use-case, where data streams received from the surveillance sensor infrastructure had to be conveyed to ATC Centres and the output of Surveillance Data Processing Systems had to be redistributed to other neighbour ATC Centres.

Intra-centre distribution

Another use-case covered by SDDS is the intra-centre distribution of surveillance data, where the filtering and protocol conversion capabilities allow data streams to be tailored for different types of consumers (e.g. Area, Approach and Tower Control Units, but also data processing systems with different needs).

International gateway

A more generic application would be as a general-purpose international gateway, allowing ANSPs to exchange multiple data flows containing different protocol types, enforcing advanced security features and offering high levels of control.


The architecture is based on a SDDS unit, consisting of software and hardware resources, designed to meet all the functional and performance requirements.

The SDDS system architecture has at least four machines (i.e. 2 x MNG Servers - MNG BB 1A & 1B with WKS embedded and 2 x CORE Servers (CORE BB Servers CORE BB 1A & 1B).

SDDS Architecture

The main concepts used in the configuration of an SDDS System are:

  • A set of inputs;
  • A set of outputs;
  • DataStream (DS), defining the action to be applied on a data flow, such as:
    • Geographical filtering
    • Data conversion
    • Data validation
  • Logical Channel (LC), defined as the association between a given input, a given output and a DataStream.

Software and hardware

Each SDDS System is made of a set of Building Blocks (BB). A Building Block is a functional element made of one or two (redundant) Units, where a Unit is the smallest functional element. It is made of an HWCI and CSCIs.

There are Mandatory and Optional Building Blocks. For some of the SDDS functionalities, Building Blocks can be replicated, in order to extend the performances and capabilities of the system.

There are two types of Building Blocks:

  • Functional Building Block:
    • CORE Building Block, in charge of providing SDDS business services. It includes the three following CSCIs:
      • CORE_DIST provides the data distribution functions
      • CORE_MNG provides the configuration management features, to control the CORE_DIST
      • CORE_REC: provides the data recording functions (CORE_REC_RECORDER)
    • Manager Building Block, that is in charge of providing SDDS management services. It includes the two following CSCIs:
      • MNG_CONF: includes an embedded HMI to configure the SDDS system
      • MNG_SMC: includes an embedded HMI to monitor and control SDDS system.
    • Workstation Building Block
  • Network Building Block:
    • Switch Building Block (not part of the SDDS HW solution), which represents the equipment that allows connections with external systems
    • Router Building Block (not part of the SDDS HW solution), which represents the equipment that implements local network connections

All components are interconnected via the following System LANs:

  • ILAN: for system management, logging and recording data
  • ELAN: for payload data
  • IWAN: for system management, logging, recording data and payload data




Target reports / sec



25 ms

Average delays ( 95% cases)

1.2 mln

Target reports / sec




Core building blocks system

An SDDS System can include up to 20 CORE Building Blocks, where up to 400 Logical Channels can be configured on each of them.

A single CORE Building Block is able to process up to 60.000 messages per second (based on the size of a typical ASTERIX CAT048 message, assumed to be 40 bytes).

With 400 Logical Channels configured, the information is processed with a delay smaller than 25ms, in 95% of the cases. The maximum delay becomes 50ms when validation, conversion, filtering and access control functionalities are enabled.

Implementation Status

4 countries

Belgium, Nederland, Luxembourg, Germany

7 partners

SKEYES, Belgian Air Force, LVNL, Royal Nederland Air Force, ANA-LUX, EUROCONTROL MUAC and DFS

Today, SDDS is operational in 11 Air Traffic Control Centres. In total, around 30 SDDS units are currently deployed in the ECAC Area.

SDDS has not been deployed in any Non-EUROCONTROL Member States Organisations (NEMSO) yet.

Safety compliance and certification

SDDS and SIMOS-related processes are compliant with the ED-153 Software Assurance Level 3 (SWAL 3) and they have been certified ISO 9001.

Since 2020, EUROCONTROL has been issuing an EC Declaration of Suitability for Use for all new SDDS system releases.

Recent SDDS releases are aligned with Regulation (EU) 2017/373 to facilitate Service Providers to create their safety support assessment and/or safety assessment.

Support and maintenance

Support and maintenance activities are managed by the SDDS Implementation and Operational Support (SIMOS) Team, based at the EUROCONTROL Headquarters in Brussels, providing direct support to SDDS Users. In turn, the EUROCONTROL SIMOS Team is supported by an Industrial Partner, which is specifically responsible for documentation and software maintenance and the implementation of new functions.

SIMOS in in charge of:

  • supporting activities at a European level to the numerous EMSO SDDS systems (both Operational and Pre-Operational);
  • preparing and maintaining the SDDS Courses, held at the EUROCONTROL Aviation Learning Centre (Luxemburg), to train SDDS Users;
  • verifying and the releasing bug fixes, updates and new SDDS versions, avoiding any regression.


  • provides a Helpdesk service, by answering Support Requests raised by SDDS Users, normally for EMSO ANSP representatives;
  • processes Trouble Reports and Change Proposals and discusses technical matters with Users, Industrial Partners and Subcontractors;
  • manages the developments performed by Subcontractors. Produces and publishes SDDS technical documentation (via iSIMOS tool);
  • participates in Factory Acceptance Testing;
  • Tests and distributes patches and new SDDS versions, delivered by Industrial Partners to SDDS Users (via iSIMOS tool).

The SIMOS service does not include hardware support.

Licence and fees


SDDS and SIMOS can be accessed by:

  • EVALUATORS, upon of signature of the SDDS EVALUATION licence (does not include the SIMOS support);
  • SDDS USERSwithin EUROCONTROL Member States organisations (EMSO), including organisations that have signed a Comprehensive Agreements, upon of signature of SDDS Service Level Agreement (includes the SIMOS support);
  • SDDS DISTRIBUTORS for non-EUROCONTROL Member States organisations (NEMSO), upon of signature of the SDDS Distributor License Agreement (this does not include the SIMOS support).

To request a licence, please contact us via the contact form on this page.


The SDDS software (in binary form, no source code) and the SIMOS service are currently free of charge to EMSO that have signed the SLA.

The SDDS software (in binary form, no source code) is also available to SDDS Distributors for NEMSO, upon signature of a Distributor License Agreement (DLA) and fees as described in the DLA (no SIMOS service is available in this case).

The SDDS software (in binary form, no source code) is also available for evaluation purposes to interested parties upon signature of an EVALUATION license, which is limited in time but free of charge (no SIMOS service is available in this case).

Please contact us via the contact form on this page in order to request a licence.

Interested in a SDDS licence?

Send us your request via our contact form. 

Communication channels

The main channels of communication with the SIMOS Team are the tools listed below.


Reporting tool for Surveillance products


Surveillance Data Distribution System Dashboard


Surveillance Data Distribution System and Dashboard Library

Training and support

At our EUROCONTROL Aviation Learning Centre in Luxembourg, we offer the following SDDS course:


The Course material is available to EMSO ANSPs (upon signature of a Non-Disclosure Agreement) and to SDDS Distributors.


All changes in SDDS are done under control of the Change Control Board (CCB) of the SDDS User Group (SDDS-UG).

In the context of SIMOS, the EUROCONTROL Agency (represented by the SDDS Service Manager) acts as the SDDS-UG representative and provides guidance to the Industrial Partners on their behalf.

The activities of maintenance and support are currently performed by the Agency, whereby EUROCONTROL experts, in conjunction with industrial partners, ensure support to the SDDS Community.

The SDDS Management team, at EUROCONTROL, is responsible for the overall strategy of SDDS, in terms of the Contractual Actions, Procurement, Licencing and SDDS User Group etc.

SDDS Governance