EUROCONTROL has just given its approval to the Comsoft RAPS-II test and verification tool for Asterix surveillance data, after evaluating it against strict new standards

Differences in air traffic control systems, procedures and data formats have long been an obstacle to harmonization. The long-awaited goal of a Single European Sky, for example, is dependent on seamless airspace which means that information must be able to flow between air traffic management systems irrespective of national boundaries.

While English has become a common global aviation language for verbal information, there is a versatile language for swapping radar data – the All-Purpose Structured EUROCONTROL Radar Information Exchange, or Asterix – which is also fast becoming a worldwide standard.

As cooperation between states becomes closer it becomes increasingly necessary to share radar surveillance information. It is essential, therefore, that neighbouring air traffic systems are able to speak the same language so that their exchanges of data take place safely and efficiently. Civil aviation authorities can make sure that their systems do indeed meet this requirement by employing a specialised Asterix testing tool.

EUROCONTROL has recently reaffirmed its approval of an Asterix testing tool called RAPS-II, designed by German communications specialist Comsoft – the first company to implement Asterix back in 1989. EUROCONTROL has formally qualified RAPS-II as an official Asterix reference product following a four-month evaluation against the latest tough European regulations, reinforcing a preliminary qualification of the tool made in 1998.

“This is important for Comsoft,” explains Erwin Mayer, the department manager responsible for the RAPS business “because the RAPS-II is now the first officially qualified Asterix reference product and test tool worldwide. We believe this is particularly remarkable because it also coincides with being the first qualification carried out under the newly developed, strict EUROCONTROL regulation guidelines unit.”

Asterix’s creation dates back to the 1980s when Europe needed a common data-exchange language to become the backbone for the cross-country radar data distribution network RADNET.

It was designed to be a flexible surveillance data format which would also allow existing legacy formats to be converted simply without deterioration of information. The language is based on the idea of categorized data. Each particular type of surveillance data is classified according to a coding system – weather data fits into one category, for instance, and surface movement data into another – and each part of the overall batch of information is specially encrypted. Asterix is flexible enough for users to customize the information format to a specific application, such as a national surveillance network.

Mayer says that Asterix is “fairly close” to becoming the official global standard for exchanging radar data. Military organizations as well as civil have integrated the standard into procurement specifications. “Today it is used widely in Europe and worldwide,” he says. “All radar manufacturers deliver data in this format. “Tender documents from anywhere in the world now require Asterix to be the surveillance standard to be used by new equipment. Particularly important is that today the United States is also using Asterix.”

One of the primary uses of the RAPS-II equipment is as a conformance test tool to verify that a particular implementation of the Asterix format complies with the standard – assisting civil aviation administrations to diagnose possible problems and handle integration or acceptance testing independently from their systems suppliers.

But the RAPS-II system is not limited to this function. It can act as a ‘universal tool box’ for Asterix which enables the operator to manage and analyse the data in several different ways.

For example, it can transform the basic Asterix data into a higher level language, namely a form which can be read and edited by people. It means that the operator does not have to put up with the complication of reading computer code in order to work with the information.

RAPS-II also allows the Asterix data to be manipulated and filtered according to sets of logical rules. The operator can also record, replay and analyse all of the current Asterix data categories over a multitude of existing communication lines – including local area networks (LANs), TCP/IP, HDLC, X.25 and others. Because it was designed as an open standard, Asterix is able to adapt to account for possible changes in the surveillance domain, such as the introduction of new technologies: for example, Mode S, automatic dependent surveillance, new surface guidance techniques and the ARTAS tracking system. There are a large number of Asterix categories available for future use. The format has proved itself able to keep up with the broadening range of surveillance data.

Mayer says that RAPS-II is also designed to keep up with this evolving environment. “RAPS-II is updated,” he explains, “whenever new Asterix categories come out or when an existing Asterix category is amended.”

"The user of RAPS-II can choose to subscribe to updates", he adds, "whenever a change in Asterix occurs." Comsoft participates in the official standardisation assemblies which govern these changes and therefore is the first to know when such changes might occur.

If there is an alteration then users can receive a corresponding update of the equipment, free of charge, directly from Comsoft. RAPS-II supports legacy Asterix categories – which can be particularly important to administrations which operate equipment using the older versions of the format – but the tool’s usefulness can also reach beyond Asterix, because it is able to support more than 20 other legacy surveillance data formats (CD2, AIRCAT and RDIF among them).

Typically the operator sets up the RAPS-II system by attaching it to a serial line or LAN. From then on, a full graphical user interface assists the operator through the configuration process. A radar databank allows the user to re-use a particular configuration, simplifying the record, replay and analysis process. Ease of use of the equipment was one of the criteria validated as part of the new EUROCONTROL qualification procedure.

This new procedure meant that RAPS-II had to pass a tougher set of requirements than those drawn up for the original 1998 qualification.

Both qualifications involved a full technical evaluation of the tool by an independent test laboratory. All of the new Asterix data categories which have been developed in the intervening five years – to handle the new surveillance techniques such as ADS – were added to the evaluation process.

In addition the 1998 and 2003 qualifications both included a quality evaluation. The earlier process included validating Comsoft’s quality processes for software development. The new qualification extends the scope of this quality assessment so that it covers maintenance and support for the tool.

But it is not just the software development which the new EUROCONTROL qualification procedure evaluates. It also examines the end product and compares it against a point-by-point list of around 30 criteria laid down by standard ISO/IEC 6126 – judging the system on characteristics such as reliability, efficiency, portability and ease of maintenance.

“The RAPS-II passed this assessment – which was carried out by a EUROCONTROL unit – with excellence,” says Mayer.

Nearly 20 countries’ aviation administrations and air traffic services providers have adopted the RAPS-II system. As the use of Asterix spreads beyond Europe the tool is set to become a valuable asset for organizations around the globe.

It is also likely that national authorities will increasingly offer to perform verification and analysis services for third-party customers using the Comsoft equipment. “Both we and other industry partners have carried out verifications for air traffic service providers using the RAPS-II,” confirms Mayer. “We have also seen cases where the RAPS-II was already included in tender documents as the required means of verification.” Mayer believes that as the use of Asterix continues to spread, so will the take-up of RAPS-II.

Because Asterix has matured greatly in the last 15 years, and its surveillance data categories have stabilized, the core formats are expected to remain stable with no major changes – although Mayer says that there is still “quite a bit of movement” related to the new surveillance categories, notably traffic information service/broadcast (TIS-B), ADS-B and ground surveillance.

With future requirements in mind, Comsoft has prepared an evolution path for RAPS-II which includes the provision of further surveillance data inventory displays, as well as additional statistical and quality monitoring features on various levels of the application data.