British surveillance aircraft are currently operating in the Baltic region.

Royal Air Force RC-135 and Sentinel surveillance aircraft have been observed operating over the Baltic nations near the Russian border.

The Open Source Intelligence Twitter account Intel Air & Sea is following the event, if you don’t follow them then I’d suggest you go do that now.

Why have we reported a relatively common occurrence? While most of us know that these are routine flights and that both NATO and Russia operate aircraft for this purpose, we believe it’s important to remind people that this is routine in order to pre-empt any tabloid or social media outrage.

What does the RC-135W do?

According to the Royal Air Force website, the RC-135W Rivet Joint is a dedicated electronic surveillance aircraft that can be employed in all theatres on strategic and tactical missions. Its sensors ‘soak up’ electronic emissions from communications, radar and other systems.

British RC-135 touches down.

“RC-135W Rivet Joint employs multidiscipline Weapons System Officer (WSO) and Weapons System Operator (WSOp) specialists whose mission is to survey elements of the electromagnetic spectrum in order to derive intelligence for commanders.”

The Royal Air Force say that Rivet Joint has been deployed extensively for Operation Shader and on other operational taskings. It had been formally named Airseeker, but is almost universally known in service as the RC-135W Rivet Joint.

The UK operates three of these aircraft.

What does Sentinel do?

The soon to be retired Sentinel is an airborne battlefield and ground surveillance aircraft based on the Bombardier Global Express ultra long range business jet and serves a role similar to JSTARS with the RAF, the jet was adapted by Raytheon to meet the RAF’s requirements.

Sentinel in flight over Iraq.

Sentinel operates in three modes: spotlight SAR, with 5-meter resolution for small-area surveillance of fixed targets; swath SAR, which provides large-area surveillance of fixed targets; and large-area surveillance of moving targets (including helicopters) travelling at a minimum of 10 kmph.

The system’s operating altitude is between 12,802 metres and 15,200 metres. From this height, its radar sensors are able to detect targets at a range of up to 300 kilometres (186.4 miles). Aside from battlefield scenarios, Sentinel can be used to monitor natural disasters, pollution, and smuggling activities.

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Seems odd that we are dropping Sentinel particularly when we are using it strategically against a long-term foe. I hope we replace the capability though, probably with further P8s.


Sentinel is being dropped because of lack of money. How is that same lack of money going to buy us more P8 airframes?


It appears we are retiring yet another valuable asset, with out replacing it
Wedgetails are a long way off , and will we get 5…….. Gapping again…..

Daniele Mandelli

Hi Ian. Wedgetail fulfils a different role and replaces Sentry, not Sentinel.

Does Protector carry a SLAR to carry out some of sentinels mission?

John Clark

We are indeed Ian, I’m hoping the news of Sentinel withdrawal will be tempered with replacement options in the SDSR.

The easiest and most obvious route is the podded system used by the P8. So additional airframes and a few pods would make sense.

Sentinel was always going to be life limited by systems obsolescence and the cost of upgrading the fleet would be considerable.

We must make sure we don’t fall into this expensive sort of bespoke trap again.

Nick Harriss

Could those pods also be carried by the RC-135?

John Clark

I shouldn’t think so Nick, the equipment has been trialed on the P8, so it’s a no brainer really.

I wonder how capable it is in relation to Sentinels abilities?

Daniele Mandelli

No idea. But even if they could, a total non starter as the 3 RC135 are “gold plated” assets, strategic platforms with a niche mission and in high demand providing intelligence to GCHQ and the NSA. They would not use them for the Sentinels ground surveillance role.


Another great asset that we have, although yet again, I know it replaced the previous 3 Nimrod versions, we could do with a few more. Its assets like these that many people don’t know about and forget we as a Country provide more niche assets for the NATO, in Europe, second only to the yanks.

Daniele Mandelli

I’ve read often that whenever there was an US op with British support 51 Sqns ELINT Nimrod R1’s plus of course SF were always first on the US request list.

The ground analysis elements that support 51 Sqn are even more interesting.

John Clark

Absolutely Airborne and Daniele. They are great assets, a couple more RC135 wouldn’t go a miss….

Another great example of leveraging Uncle Sam’s investment and support network.

Can you imagine the pickle we would have now been in had the three development MR4a’s been refurbished as ‘R1’ replacements, as the original plan stood to serve along the 9 Nimrod MR4a aircraft.

Bespoke British ELINT systems in a bespoke airframe, what an absolute nightmare that would have been.

The cost of regular systems upgrading and keeping them in the air would have been absolutely eye watering!

Daniele Mandelli

Yes. I’m unsure of the exact fit on the Rivets as its obviously all classified. I assume a high commonality with USAF/NSA systems, though I also read of something called “StarWindow” once.

John Clark

Hi Daniele,

A very high commonality in systems, considering they are effectively regarded as an extension of the US fleet and get jointly tasked, they must have virtually the same fit, or it would effect their usefulness.

As you say, perhaps without some of the highly classified NSA specific systems.


Sentinel was an incredible asset. It always left allies amazed and dare I say with envy. It was an asset the RAF could gloat about how the RN can with the Type 45 PAAMS and the Astute-class sub hunting capabilities. Raytheon is one of those partners who a rare to find nowadays, they have always been heavily invested in the asset and the Broughton site, they were always proposing to the MoD upgrades and additional capabilities for Sentinel that would give it a lifeline. Upgrades and additional capabilities such as an upgraded radar (incl. maritime capability), fitting the DB-110 into… Read more »

Daniele Mandelli

Never mind RC135’s and Sentinel.

The last word in UAV stealth surveillance may have been photographed for the first time.