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What is ASTERIX?

ASTERIX stands for All Purpose STructured Eurocontrol SuRveillance Information EXchange.

It is an ATM Surveillance Data Binary Messaging Format which allows transmission of harmonised information between any surveillance and automation system.

ASTERIX defines the structure of the data to be exchanged over a communication medium, from the encoding of every bit of information up to the organisation of the data within a block of data - without any loss of information during the whole process.

ASTERIX is a EUROCONTROL Standard which refers to the Presentation and Application layers (layers six and seven) as defined by the Open Systems Interconnection (OSI) Reference Model (International Standards Organization (ISO) Standard 7498).

Transmission of ASTERIX coded surveillance information can make use of any available communication medium, for instance Wide Area Network (WAN), Local Area Network (LAN), Internet Protocols (IP), etc as those belong to lower layers.

Considering that there is information common to all systems (for instance position, Mode-A Code and Mode-C Code information), ASTERIX specifies minimum requirements at the Application level, so as to ease data exchange between heterogeneous applications. The communication between two different systems (even located in different countries) is thus made possible, based on a core of commonly used surveillance related data, transferred in the same way by the ASTERIX Presentation layer.

For the transmission of information related to a specific application, data items are grouped in ASTERIX Categories. Up to 256 categories can be defined. The definition of these categories and their composition is managed by the ASTERIX Maintenance Group (AMG).

Scope of ASTERIX

ASTERIX has been developed to ease the exchange of surveillance information between and within countries.

Thus, the main users of ASTERIX are the Air Traffic Control (ATC) Centres.
Today almost all ECAC States are using this data format in their ATC Centres.

But ASTERIX is also used by Industries to help stabilisation/maturation of new technologies, and is then integrated in surveillance sensors and in automation systems such as ARTAS (ATM suRveillance Tracker And Server), RMCDE (Radar Message Conversion and Distribution Equipment) and RADNET (RADar NETwork implemented in the so-called four states area - Benelux and Germany), RAPS II (Radar Analysis, Playback & Simulation System for Surveillance Data).


ASTERIX as an evolutive standard

As the volume of Air Traffic is continuously increasing and as high level of Safety must be maintained, the surveillance systems are under constant evolution.
New-generation surveillance technologies are being developed which need to cohabit with current systems. The information they generate must be transmitted in a harmonised and efficient way.

ASTERIX is past, present and future.

Until the 1980s, every National Administration developed its own format for delivering radar data to Air Traffic Control Centres. This resulted in duplicate effort and made exchange of radar data across borders a complicated issue.
The need for a common European data format became apparent and an example of what a standard format could look like was presented by Maastricht UAC to the former Radar Systems Specialists Panel (RSSP) in 1984.

The All purpose STructured Eurocontrol SuRveillance Information eXchange format (ASTERIX) was born, the ASTERIX Users Group was created to work on a common European definition which led to ASTERIX's official approval by the RSSP in its 15th Meeting held on 1/4 July 1986.

In 1988, the ASTERIX Manual was presented, describing the initial structure of ASTERIX and providing a set of "data items" to cover monoradar and weather data.

This initial structure was enhanced in 1991 to provide more flexibility, and the ASTERIX Manual was replaced by the first draft of what is now the ASTERIX Structure Document which is the Standard Document to be used for implementing ASTERIX (this document can be found under section ASTERIX Categories).

In 1994, the responsibilities of the former RSSP were taken over by the Surveillance Team, and the Surveillance Task Force for Radar Data Exchange (STFRDE) was created to continue the work of the ASTERIX Users Group (now renamed ASTERIX Maintenance Group). Since then, the application domain of ASTERIX has constantly expanded, and ASTERIX has now been adopted world-wide as the standard format for exchanging data from primary, secondary, monopulse, Mode S and weather radars, and also for carrying multiradar data, data-link, SMGCS, control & monitoring, etc...


The philosophy of ASTERIX can be described in two short phrases:

  • "Distribute everything as required" and
  • "Do not transmit more than necessary"

ASTERIX has been designed as a flexible way of encoding surveillance related information to be exchanged between users. It is characterised by the grouping of information in data categories and the flexible generation of messages in order to save bandwidth in the transmission.

For the various applications within the surveillance domain, individual data categories are defined. This allows the designer of a system to implement exactly what is needed, not more and not less. The software to be implemented can be tailored exactly to the function of the respective system.

Should at a later stage additional functionality be required, the necessary interface can easily be added by integrating the ASTERIX category defined for the specific application.

The same flexibility applies to the generation of the ASTERIX messages itself. Subdividing the whole information into individual data-items, a message can be composed according to the information available. Items carrying no information are simply left out when creating the message. The FSPEC, a sort of "Table of Contents" for each ASTERIX message precedes the data items, indicating unambiguously to the receiving system, which data items are present and which are not. This allows the processing to be adapted to the real message contents. There is no need anymore to transmit useless bits and bytes or to skip unwanted information in a message.

The sequence of items in the message has been defined in the co-called “User Application Profile” UAP.

It is the task of the “ASTERIX Maintenance Group (AMG)” to manage and co-ordinate the maintenance and evolution of existing or the development of new ASTERIX categories, should the need come up. In most cases this will be triggered by the launch of a new application (such as ADS-B or Multi-Lateration) or by the need to adapt an existing category to changing needs. In any case, the fact that this process is controlled by a body composed of members of most ANSPs makes sure that the results and a new ASTERIX category are commonly accepted and form the specification against which at a later stage the implementation will be validated.


What is a Category?

To implement the ASTERIX data format in a structured way, the set of documentation has been subdivided into Parts, each of which grouping the data for a specific application and purpose.

Each ASTERIX Part contains one or more Data Categories.

The information contained in these categories is dedicated to a specific area of application and defines which data in which format is to be transmitted between the users of these applications.

Each category consist of a Catalogue of Data Items, with the Data Item being the smallest unit of standardised information.

This categorisation serves multiple purposes:

  • it is easy to identify the application;
  • The dispatching of the data to the appropriate task within the receiving system is facilitated;
  • only the category for applications implemented in the user system have to be implemented.

Up to 256 Data Categories can be defined and their usage is as follows:

  • Data Categories 000 to 127 for standard civil and military applications;
  • Data Categories 128 to 240 reserved for special civil and military applications;
  • Data Categories 241 to 255 used for both civil and military non-standard applications.

For Data Categories 000 to 127, the responsibility for the allocation of the number rests with the SuRveillance Data Exchange – Task Force (RDE-TF), with endorsement by the Surveillance Team (SURT).

For Data Categories in the range from 128 to 240, the allocation of the category number is delegated to the issuing authorities. In future a closer co-ordination with EUROCONTROL is envisaged wherever possible. For more information, please contact the ASTERIX team.

For the definition of Data Categories between 241 to 255 please contact the ASTERIX team. These categories are designed for specific users and not part of the ASTERIX Standard Document.

You will find below the ASTERIX Structure Document which is the Standard Document to be used for implementing ASTERIX.

  • Part 1 - ASTERIX Structure: ASTERIX, the "All Purpose STructured Eurocontrol SuRveillance Information EXchange" describes the message structure and contents applied to the exchange of surveillance related data between systems in the ATM environment. The development of ASTERIX is managed by the ASTERIX Maintenance Group (AMG).

    The ASTERIX standard documentation is subdivided into parts, part 1 of which describes the basic principles to be respected and the general rules to be applied when defining and implementing the ASTERIX data format.

How to choose?

Choosing the adequate ASTERIX Category

The following table will give you indication on how to choose the relevant ASTERIX Category, according to the type of Surveillance related Data to transmit.

Transmission of (Surveillance related Data)

From (Data Source)

ASTERIX Category to use

Monoradar target reports

PSR radar
SSR radar
M-SSR radar
Mode-S station

Cat 048

Monosensor target reports

ADS-B ground station

Cat 021

Monoradar target reports

Surface movement radar

Cat 010

Monoradar service messages

PSR radar
SSR radar
M-SSR radar
Mode-S station

Cat 034

Mode S surveillance coordination function messages

Mode-S station

Cat 017

Mode S datalink function messages

Mode-S station

Cat 018

Ground station service messages

ADS-B ground station

Cat 023

Monoradar service messages

Surface movement radar

Cat 010

Directed Interrogation Messages

Mode-S station

Cat 007

Monoradar weather information


Cat 008

TIS-B Management messages

ADS-B ground station

Cat 022

A-SMGCS data (target report, flight plan data, holdbar status)

SMGCS system

Cat 011

System track data

SDPS system

Cat 062

Sensor Status messages

SDPS system

Cat 063

SDPS Service status messages

SDPS system

Cat 065

Safety Nets Alarms

Safety Nets Server

Cat 004

Multilateration data

Multilateration ground stations

Cat 020

Multilateration System Status Messages

Multilateration ground stations

Cat 019

Digitised Raw Video Information

Rotating Radar

Cat 240

ASTERIX Version Information

Any system

Cat 247

Monoradar Target Reports

Precision Approach Radar (PAR)

Cat 012 (Reserved)

Monoradar Service and Status Messages

Precision Approach Radar (PAR)

Cat 013 (Reserved)

Monoradar Weather Reports

Precision Approach Radar (PAR)

Cat 014 (Reserved)

Monosensor Target Reports

ADS-C Ground Station

Cat 024

Foreign Object Debris (FOD)

Runway Debris Detection System (RDDS)

Cat 239 (Reserved)



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