USAF Or NATO Should Snap Up The RAF’s Retiring R1 Sentinel Radar Planes

The Sentinels are powerful, highly relevant, modern and relatively efficient intelligence gathering tools that need to remain in the air.

byTyler Rogoway|
NATO photo


The Royal Air Force is being forced to give up one of its most powerful surveillance assets—its fleet of five Sentinel R1 ground targeting radar planes—due to competing budgetary priorities and yet another round of governmental cost saving measures. The R1 fleet has "been on borrowed time" fiscally for most its relatively short service life, but the final decision to axe the planes once and for all seems to have finally occurred, and they will be phased by the end of the decade. Although this is a major blow to UK Ministry of Defense's portfolio of capabilities, it is an outstanding opportunity for the Unites States Air Force and the US military as a total force.

These aircraft provide unique intelligence by keeping track of moving vehicles and taking highly detailed synthetic aperture radar "pictures" or "maps" of the battlefield. They can do this at standoff ranges and over huge swathes of the earth's surface. They have secondary over-water maritime surveillance and low and slow flying target tracking capabilities as well. Their data can be used in real time to inform and reposition ground forces, or to order attacks on enemy columns, or to divert tactical reconnaissance aircraft, such a MQ-9 drones or MC-12s, to take a closer look at a certain area using their electro-optical or tactical GMTI radar systems

The Sentinel's "imagery" can also be used for planning future strikes, for bomb damage assessment and for keeping track of the enemy's pattern of life around key areas. In essence, it gives its war fighting "team" an unfair advantage over the enemy, and it can even do so through bad weather and smoke when optical and infrared sensors are left all but useless. 

Sentinel R1, Raytheon

Originally known as the Airborne Standoff Radar (ASTOR), the Sentinel R1 fleet is not being retired because it is old or inefficient. Far from it in fact. The Global Express business jet-based radar aircraft were introduced into service less than a decade ago, in 2008, and the type's first flight occurred just four years earlier. Compared to the USAF's fleet of rickety old E-8C Joint Surveillance Target Attack Radar (JSTARS) aircraft, which are built around secondhand 707 airframes that were far from new when they were introduced into service starting some 25 years ago, the R1s are toddlers. 

E-8C JSTARS is a very capable sensor system flying on a very old and expensive to operate aircraft., USAF

Today the average age of the 16 strong E-8C fleet is just shy of 50 years. The aircraft are unreliable and notoriously expensive to operate. The mix of a very high-tech sensor system and a tired platform to lug it aloft is not a good one, especially considering the high demand for JSTARS capabilities around the globe today. 

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The R1s provide very similar—and in some cases superior—capabilities as the E-8 but in a far more efficient package, and are totally interoperable with existing US and NATO systems. In fact, the R1s are very similar to designs that are intended to replace the E-8 JSTARS fleet under a competitive tender that is ongoing now. The fight for the $6.9 billion, 17 aircraft deal is fierce, with Boeing’s 737 going up against the Northrop Grumman and L3's Gulfstream G550 and Lockheed and Raytheon's Bombardier Global 6000. Each team has their own significant merits, as do the platforms they have chosen to host their radars, but whichever plane manufacturer wins, they could see more follow-on orders for other special mission aircraft. 

The contract is expected to be awarded this fall, with initial operating capability set for 2024. The new system's fully operational date is slated to be sometime in 2028.

Boeing's JSTARS replacement offering based on the 737-700., Boeing

It will take many years to fully field the JSTARS replacement, and in the meantime the E-8C fleet is having a hard time getting into the air while demand for their unique capabilities is only increasing. During a recent House Armed Services Committee hearing, Pentagon officials made it clear that there is a serious Ground Moving Target Indicator (GMTI) deficit—precisely the primary capability the JSTARS and the Sentinel R1 provides—in theaters around the globe where the US is engaged militarily. This is part of a greater ongoing intelligence, surveillance and reconnaissance (ISR) platform deficit in the US military. As of now only 30 percent of ISR tasking requests can be met. 

With all this in mind, taking on the RAF's young Sentinel fleet as the RAF retires them would provide enhanced capabilities in the near term that are especially suited for operating at high sortie rates from relatively austere locations around the globe. Not just that, but the R1's AESA radar could potentially be upgraded to provide enhanced surveillance over water and littoral regions and even possibly execute electronic attacks on enemy emitters at standoff ranges. 

Sentinel R1, MoD/Crown Copyright

The Sentinel/ASTOR system also includes specialized communications and command and control infrastructure, including eight transportable ground stations—two Operational Level Ground Stations (OLGS) and six mobile Tactical Ground Stations (TGS). Much of the Sentinel's synthetic aperture radar imagery and GMTI tracking can be exploited by operators in these ground stations via data-link, which is somewhat different than the JSTARS concept, but is more like the systems being fielded for the JSTARS recapitalization initiative. All this infrastructure exists and would be basically thrown away with the retirement of the R1s.

The R1's networking concept., Public Domain

Overall, the USAF could not only immediately augment its existing fleet of tired E-8s by acquiring the Sentinels, but it could also lower the initial tender for the E-8 replacement by a number of aircraft, and thus save billions. The Global Express is also already in the USAF's inventory in the form of the E-11 Battlefield Airborne Communications Node (BACN), so commonality and training within the service already exists. Also, these E-11s are deployed to the same places R1s would be, which could be beneficial when it comes to logistically supporting these jets in the field. 

E-11 BACN. Some have different configurations, including large satcom domes on their spine and sensor canoes on their belly, making them closely resemble the R-1., USAF

It may also be possible for the Department of Defense to work out a crew and cost sharing deal with the Ministry of Defense, whereby a certain number of R1 taskings can be dedicated to the UK's strategic needs. This way the cost is shared by both parties based on usage, and as a result, MoD doesn't have to say goodby totally to its strategic GMTI and SAR capability. It also means that the MoD will not have to bare the cost of the infrastructure that goes along with operating the R1s. Since the two allies work together on foreign campaigns more than not, such a deal would be a win-win for both parties and the concept does have precedent.  

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Although the loss of the R1 fleet may be a sad pill to swallow for the Royal Air Force, and the MoD as a whole, it represents a real opportunity for the US that could be aggressively explored in the near term. Sadly, the powers that be within the Pentagon and in the US defense industry will likely fight any sort of second hand acquisition of the Sentinel fleet because it will, even if to a relatively small degree, put in jeopardy the scope of lucrative E-8 JSTARS replacement contract. With careers being bet on this procurement initiative both inside the DoD and in the ranks of its biggest vendors, the retired R1s, which are needed today and can fit right into the USAF's inventory and order of battle, will likely be passed over. We can only hope this won't be the case as America's warfighters can seriously benefit from having these aircraft overhead in hotspots around the globe. 

An R-1 takes off from Mojave Air And Space Port. , Alan Radecki /wikicommons

Alternatively, NATO could acquire these aircraft for the alliance's collective use under a similar scheme as their E-3 AWACS fleet, but they are already receiving GMTI and SAR capability via their five aircraft, Global Hawk-based "Alliance Ground Surveillance" initiative. But NATO will likely want more capacity and in a more flexible manner than the unmanned Global Hawks can provide. Instead of buying more Global Hawk derivatives, they could diversify their capabilities and likely save large sums of money by taking on the R1 fleet. 

Such a transfer of capability would also make losing the aircraft more palatable for the UK. But where exactly the funding for operating and maintaining the Sentinels will come from is unclear. The Trump Administration could tell the alliance pitch in to adopt the fleet, as making demands of NATO partners has been part of the White House's core foreign policy agenda, but it could take time for making such an arrangement a reality. Like any weapon system, the longer the R1s sit in limbo the more expensive it will be to return them to service. 

Either way, these aircraft need a home. Hopefully the US will step in—either with money or leadership—and see that they find one that is beneficial to the US and its allies. 

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