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  • Writer's pictureThe Pulse

ACCS Makes Tracks

An ACCS Estonia Operator working on the system
ACCS Estonia Operator

By Dr Thomas Withington

The North Atlantic Treaty Organisation’s Air Command and Control System is the alliance’s biggest single procurement and perhaps its least well known.

“The NATO Air Command and Control System is intended to combine and automate at the tactical level the planning and tasking and execution of all air operations,” notes a NATO (North Atlantic Treaty Organisation) document outlining the ACCS’ scope. Dubbed “the most comprehensive and complex of NATO’s programmes” once completed, the Air Command and Control System’s (ACCS) architecture will help safeguard 2.9 million square nautical miles (ten million square kilometres) of NATO’s European airspace. It will connect 20 different installations responsible for controlling NATO combat aircraft and 40 different types of ground-based air surveillance radar will be networked into the architecture, the NATO document continues. Connectivity between airbases, Surface-to-Air Missile (SAM) installations; control and reporting centres; fighters, radars and supporting infrastructure will be assured not only within a nation’s Integrated Air Defence System (IADS), but between NATO European nations equipped with ACCS. This will be achieved through 160 datalinks and interfaces and the 14 million lines of code needed by the ACCS software. For all intents and purposes, ACCS will be the C2 backbone underpinning the NATO Integrated Air and Missile Defense System (NATINAMDS) protecting the skies of the alliance’s European membership.

Taken individually its goals sound relatively simple: ACCS is to replace a raft of Command and Control (C2) systems managing an array of IADS throughout most of NATO’s European membership with a single, scalable hardware and software C2 architecture. This same architecture will provide the C2 element for fixed Combined Air Operations Centres (CAOCs) and their deployable CAOC counterparts (DCAOCs) which NATO uses to manage air campaigns. Finally, ACCS will federate the Recognised Air Pictures (RAPs) produced by individual IADS members into a so-called ‘Super RAP’ depicting NATO’s European airspace and air approaches in its entirety. The requirement for ACCS was originally defined by NATO back in 1980. The rationale to consolidate the disparate tasks the ACCS was to perform occurred at the end of the Cold War in late 1990 precipitated by the seismic shift in European geopolitics. It is the combining of these three goals into a single project executed simultaneously which gives ACCS its fiendish complexity, not to mention its surfeit of acronyms.

The story so far

NATO air defence and acronyms have always been synonymous with one another. STRIDA, POACCS, SADA, SEKTOR and MASE were just five of the disparate IADS C2 systems used by the air forces of France, Portugal, Spain, the Czech Republic and Denmark respectively. The C2 hardware and software equipping all these, and several other European NATO IADS have been, or are being, replaced by the scalable ACCS ensemble.

The ensemble forms the basis of six different configurations which the programme is rolling out across most of NATO’s European membership. These five configurations provide NATO with CAOCs, DCAOCs, ARS (Aircraft Control Centre, Recognised Air Picture Production Centre and Sensor Fusion Post), deployable ARS (DARS), combined CAOC and ARS (CARS) and ACCS Software Base Elements (ASBE).

The fixed and deployable CAOCs form the war planning and tasking element of ACCS. They allow NATO to plan and manage an air campaign from European territory and draft the all-important Air Tasking Order (ATO), the ‘sheet music’ denoting air operations to be performed over a 24-hour period. The CAOC then monitors the execution of the ATO.

NATO has two fixed CAOCs. One is based in Germany at Uedem airbase in the west of the country the other is located at Torrejón outside Madrid. The DACCC (Deployable Air Command and Control Centre) is based at Poggio Renatico airbase, northern Italy. The CAOCs and DACCC are directly subordinate to COM AIRCOM (Commander Allied Air Command) headquartered at Ramstein airbase, southwestern Germany. AIRCOM is responsible for the operational command of NATO air operations and uses the Air C2 Information System to this end. The DCAOC and DARS perform similar functions for NATO out-of-area operations.

Below the CAOCs, the ARS is tasked with the C2 of an IAMDS protecting a nation’s airspace and air approaches. ACCS will yield a DARS (an element of the DACCC) to provide similar support to NATO out-of-area operations or to back up a static ARS when need be. Finally, the ASBE (ACCS Software Based Element) provides a mechanism for NATO members not destined to obtain the ACCS architecture, either because they are relatively new NATO entrants or because they do not have the financial wherewithal to make the procurement, with a gateway to connect into the ACCS architecture and hence into the NATINAMDS network. This is important so that these nations can share their own radar pictures with the rest of the alliance, and likewise receive relevant C2 and situational awareness information from elsewhere in NATO. For instance, the new Baltic NATO members of Estonia, Latvia and Lithuania will all have ASBEs, as will Iceland amongst others. The full breakdown of sites that will receive the ACCS architecture is indicated in Figure 1.

Figure 1 – Sites Receiving ACCS Architecture

The ARS element is concerned with mission execution focused on surveillance and fighter/ground-based air defence tasking. As noted above, the ARS centres combine several tasks: They are Aircraft Control Centres commanding fighters and ground-based air defences within their area of responsibility. The ARS’ RAP Production Centre combines the sensor feeds in its area of operations to provide a single RAP of its locale, known as the Local Air Picture or LAP. As well as using organic sensors, the RAP Production Centre can accept sensor feeds from non-organic assets in its locale like naval vessels or Airborne Early Warning and Control platforms and ground-based air defences. The ARS will send the RAP upwards to other echelons at the national level, to help create the national recognised air picture and to NATO command (CAOCs) to populate the Joint Environment Picture, previously known as the Common Operating Picture of the alliance’s airspace at the AIRCOM. The sensors which the ARS relies upon are managed by the ARS’ Sensor Fusion Post.


Unsurprisingly, the entire ACCS infrastructure places a premium on communications, notably Tactical Data Links (TDLs). These shuttle information between ARS sites and between these sites and the AIRCOM; and carry sensor data while connecting ground-based air defences and airbases. These TDLs include NATO’s Link-16 protocol which moves track and tactical information between aircraft, ground sites and personnel involved in the air battle across frequencies of 960 megahertz/MHz to 1.215 gigahertz/GHz. NATO’s Link-11, which performs a similar task, but mainly for naval assets using frequencies of 2MHz to 29.9MHz and 225MHz to 399.975MHz also forms part of the ACCS TDL structure, as does Link-11’s successor, Link-22. Link-22 will gradually replace Link-11 over the coming decade. Track data can be shared between ground-based elements like ARS sites, CAOCs and SAM batteries using NATO’s Link-1 TDL which, despite being developed in 1950s is still in use. Meanwhile the ASTERIX (All Purpose Structured Eurocontrol Surveillance Information Exchange) protocol will be used extensively by the ground-based air surveillance radars supporting ACCS networks across the continent. ASTERIX is a data format which digitises a radar’s data allowing this to be shared around a network to help create the RAP. In addition, NATO has a radar language protocol known as the ACCS Wide Common Information Exchange Standard, or AWCIES. This is defined by NATO’s Standardised Agreement 5535 for the exchange of radar track data.

United Kingdom

One NATO member remains conspicuous by her their absence in the programme, namely the United Kingdom. The UK has forged ahead with the Royal Air Force’s Project Guardian initiative. This replaces the existing UKASACS (UK Air Surveillance and Control System) hardware and software architecture which provides C2 for the RAF’s air defence system. IBM is leading the rollout of Project Guardian winning the contract from the UK Ministry of Defence (MOD) in April 2018. The UK had been a partner in the ACCS effort and continues to pay into NATO’s ACCS budget but last decade the MOD suspended the UK’s involvement in the procurement. This occurred amidst concerns that the nascent ACCS architecture did not meet UK safety requirements.

Since then the ACCS architecture has matured, although the decision of the British government to move ahead with the Project Guardian initiative in 2017 effectively ended the UK’s involvement in the effort beyond its financial contribution. Nonetheless, the Project Guardian system will feed the UK’s RAP into NATO’s CAOC at Uedem, central Germany. This will be vital to ensure that NATO has the most detailed picture of European airspace possible with the radar coverage provided over the UK contributing to the radar picture of NATO’s northern and western flanks.

However, the UK’s decision to has been controversial. Some sources close to the UK’s air defence community told the author in the past that the UK chose to cease its involvement with ACCS, beyond its financial contributions when the ACCS programme was at a comparatively early stage. They intermated that the maturity of ACCS at the time meant that the ensemble would have been unable to meet the UK’s safety criteria. This committed the UK to proceed with Project Guardian. The sources added that these safety concerns are now no longer valid given ACCS’ maturity. Project Guardian is expected to cost the UK $80.7 million to procure according to official UK announcements, with this potentially increasing to $108.7 million during the purchase. The UK will have to pay for Project Guardian at the same time as contributing financially to ACCS. Given that the Project Guardian effort is now well and truly underway debates over whether the UK would have been better waiting for ACCS to mature and then adopt this as the C2 element of the UK’s IADS are now purely academic.

ACCS and Missile Defence

Alongside helping to protect NATO airspace against air-breathing threats, and assisting the management and execution of air operations, the alliance uses the ACCS architecture to assist its Ballistic Missile Defence (BMD) posture. ACCS will federate disparate sensors and weapons deployed to help protect NATO’s European membership against ballistic missile attack. These include ship-based assets like US Navy warships equipped with Lockheed Martin’s Aegis Combat Management System (CMS) and Raytheon RIM-161 Standard Missile-3 series SAMs routinely deployed from the Armada Española (Spanish Navy) base in Rota, southern Spain. Other assets include the Eurosam PAAMS (Principle Anti-Air Missile System) SAM capability deployed by the navies of France, Italy and the United Kingdom. This is in addition to Thales SMART-L L-band (1.215GHz to 1.4GHz) and APAR X-band (8.5GHz to 10.68GHz) naval surveillance radars deployed on warships operated by the Danish, Dutch, German, French and UK navies. Ballistic Missile Early Warning satellites owned by NATO members can also feed their data into the NATINAMDS.

The NATINAMDS is reinforced with data from Land-based sensors. For instance, the US Army has forward-deployed a Lockheed Martin AN/TPY-2 X-band ground-based air surveillance radar to Kürecik airbase in eastern Turkey. This keeps watch for ballistic missile launches from the Middle East. Other radars watching NATO’s European airspace share their data with the NATINAMDS. Radar information lets effectors like the RIM-161 SM-3 SAMs mentioned above along with other surface-to-air missile systems like Raytheon’s MIM-104 Patriot series, and MBDA’s Aster-30/SAMP/T and Aster-15/30 weapons deployed at sea engage incoming missiles.

The ACCS configuration supporting NATO BMD efforts connects the so-called ‘Aegis Ashore’ site at Deveselu airbase, southern Romania. Aegis Ashore is a land-based combination of the Aegis CMS, the Lockheed Martin AN/SPY-1D S-band naval surveillance radar and RIM-161 SM-3 SAMs tasked with ballistic missile interception. A second Aegis Ashore site is under construction at Redzikowo airbase, northern Poland. This should be operational by 2022 according to media reports. The ACCS BMD architecture is now operational at NATO Allied Air Command’s Ballistic Missile Defence centre at Ramstein airbase.


NATO’s Communications and Information Agency, known as the NCI, is charged with delivering ACCS via the NCI’s Air Command and Control Programme Office and Services (Air C2 POS). Air C2 POS is spread across three sites at NATO headquarters in Brussels, Belgium and at the NCI Agencies in The Hague, on the Netherland’s western North Sea coast and Glons, eastern Belgium.

Where does ACCS go from here? Its full implementation remains some years away and may not be realised until early next decade: “The first priority of the programme is for everyone to have the ACCS architecture and the interoperable systems,” says a source close to the programme. The next priority, they continue, will be to connect all the disparate elements of ACCS across the participating nations. In essence, the existing legacy C2 systems underpinning the disparate IADS deployed across NATO’s European membership will remain in service as ACCS is phased in and these legacy systems retired. The source added that a programme as wide-ranging and complex as ACCS will inevitably suffer delays and setbacks. To date, the only element of ACCS fully deployed is the DARS at Poggio Renatico. NATO plans to deploy the DARS to Greece and will perform NATO exercises and trials connecting it with the Hellenic Air Force ARS (ARS Larissa) with a view to implementing ACCS in the immediate future the source revealed. Besides, the CAOC Uedem is striving to reach its initial operating capability for ACCS by this summer. ACCS is a marathon and not a sprint, but the effort should be a major leap in safeguarding NATO’s European skies and efficiently managing future air campaigns.

Read the article published by Military Technology Magazine:


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