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Vital Importance of Maintaining RAF Sentinel R1 Astor Capability By Howard Wheeldon, FRAeS, Wheeldon Strategic Advisory Ltd.





One of many final decisions awaited from the MoD and that, along with other material defence procurement strategy, has been delayed by the planned ‘Defence and foreign policy review’ has been a necessary rethink in respect of the future of the small but strategically very important Royal Air Force fleet of Sentinel R1 (ASTOR) aircraft capability and that, in what I regarded back then as having been one of the worst possible outcomes to have come from the 2015 Strategic Defence and Security Review – the MoD announcing of an OSD (Out of Service Date) of Sentinel R1 Astor capability of 2021.

I am not alone in having worked hard over the past five years to emphasise the vital importance to the nation and to the Royal Air Force of extending the life of Sentinel R1 (Astor) capability until at least 2028 and, with some mid-life investment, all the way through to 2035.

However, although no formal announcement has yet been made, my fear is that what we might get is a ‘process based’ decision not to extend Sentinel R1 Astor capability OSD beyond the already planned 2021 date. It has been suggested to me that such a decision has already been taken and if that is so, a direct result of this would be that the UK would lose yet another crucially important C41STAR capability, an asset that in my view in what is an increasingly more dangerous and uncertain world, the UK just cannot afford to be without.

While I hope that the above suggestion in respect of a decision to scrap Sentinel R1 (ASTOR) capability having already been made is proved to be wrong allow this piece to be a warning of not only how some of those involved in decision-making processes in relation to defence draw their conclusions but importantly, serve as another reminder of the vital importance that Sentinel R1 Astor capability provides. Let it also be timely in saying that if the decision has already been made, they must now reconsider.

To allow Sentinel capability to be scrapped next year would, in my opinion, be one if not the worst decisions possible in relation to defence equipment capability and air power related operation since some of those that came out of the appalling SDSR 2010.

If a decision not to extend Sentinel OSD is the one that eventually emerges I fear that I would be almost bound to place the primary responsibility and blame on the now more Army influenced FinMilCap, an organisation within the MOD designed to influence future direction of defence.

True, funding for each and every existing and future planned defence programme is always an issue but my senses are that some within FinMilCap have also been working hard against a decision to extend Royal Air Force Sentinel R1 ASTOR capability for their own ends.

Whatever, if a decision to scrap Sentinel R1 Astor capability is the one that officially emerges I would as said above regard this as being one of the worst decisions in relation to defence capability that I have ever had the misfortune to come across in my long defence and aerospace related career. We will see but, in any event, I hope that any powers that be who see this piece will see it as an important reminder of why Sentinel R1 Astor capability remains of vital importance to the UK, to NATO and to our other defence allies.   

The bottom line for me is any decision to scrap Sentinel R1 ASTOR capability next year would, in a world of increased uncertainty, rising international tensions and threats, be tantamount to being ‘intellectually absurd’ – one that could only have been based on a mix of bias, politics and process rather than one based on strategy, requirement and proven operational performance of the capability in service. 

Based at RAF Waddington and operated by V(AC) Squadron, suffice to say that Royal Air Force Sentinel R1 Astor capability has been on near-constant operational deployment ever since it was introduced into service in November 2008. Acquired as operationally-tested off-the-shelf capability, Sentinel R1 ASTOR capability has for the past twelve years provided a very practical solution to a crucially important and very necessary aspect of UK ISR (Intelligence, Surveillance and Reconnaissance) requirement.

Regarded as being exceptional capability which has performed consistently well over the past twelve years – made possible by the unwavering commitment, professionalism and pride of the highly skilled and dedicated V(AC) Squadron personnel at RAF Waddington and by the Raytheon UK operation at Broughton, North Wales which is the design authority for RAF Sentinel R1 and the other very important aspect of electronic surveillance capability that is, with its combination of sensors  being considered valuable to Army ground commanders complimentary to Sentinel in the form of RAF Shadow R1, regarded being another aspect of vital ISTAR related capability. 

The small fleet of four Sentinel R1 Astor (Airborne Stand-off radar) aircraft currently in service with the Royal Air Force are based at RAF Waddington in Lincolnshire. Aa fifth Sentinel airframe which, as directed within SDSR 2015, has been out of service for some years but with that decision subsequently having been reversed, the aircraft is I believe currently undergoing a full overhaul process in order to bring it back into service.

Raytheon UK’s Broughton MRO facility is a highly invested operation but, if my conjecture that a decision by the MOD to pull Sentinel has already been taken, such work would likely soon stop. In any event, Raytheon are to be congratulated for the manner and scale of investment they have made Broughton to support this and other related defence activities on site. Clearly, a potential abandoning of Sentinel R1 Astor capability by the MOD next year would have implications for Raytheon as well.  

I would describe RAF Sentinel R1 Astor as being a capability that provides timely and actionable intelligence data and that over the past twelve years, it has made a very significant contribution to military and surveillance operations around the world.

Cancelling what is a modern, highly relevant and efficient intelligence gathering platform would create yet another huge and potentially dangerous capability gap and one that would have serious implications not just for the UK. Over the years the US, NATO and other international partner air forces such as France have spoken out about the vital contribution Sentinel R1 Astor capability has made and how the capability has supported their operations. Be in no doubt that no other capability exists in the UK to deliver the acute and very necessary intelligence pictures that Sentinel R1 Astor capability provides.

Since entering service in 2008, Sentinel R1 Astor capability has been deployed on operations, including Operations HERRICK (Afghanistan), TURUS (Nigeria), NEWCOMBE (Mali), ELLAMY (Libya) and most recently Op SHADER (Syria) and where in the latter operation it has delivered consistent and highly valuable reconnaissance and intelligence support to coalition operations against ISIL/Da’esh. 

When not deployed, Sentinel routinely conducts operational missions from its home base at RAF Waddington in support of UK and NATO ISR requirements. It also has valuable flexibility and is capable of monitoring hostile forces, immigrant boats in the Mediterranean, or amassing vital data during natural disasters, such as had occurred in 2014, when Sentinel R1 aircraft were used to assess flood damage across southern England

In November 2018 I wrote the following:

Of particular importance in these more troubled geo-political times and one that highlights the absolute need to ensure that the UK maintains sufficient capacity in all forms of critical intelligence, surveillance and target tracking capability, one that really stands out is to ensure that the Royal Air Force maintains sufficient levels of Airborne Stand-Off Radar (ASTOR) Sentinel R1 capability for the longer term.

To that end and following a similarly sensible decision from the then Secretary of State for Defence to retain the Royal Navy’s Batch One OPV fleet, I reminded of the huge importance of Sentinel R1 ASTOR capability and requested that government must now reconsider and move toward long term extension of Sentinel R1 capability. This as far I was concerned was not only to be considered as a ‘must’ but also as an obvious step for the Secretary of State for Defence to take.

It was already very clear to me then that we needed to bring the number of available Sentinel R1 aircraft back up to the original five and at the same time, push forward the Out-Of-Service Date (OSD) beyond 2028 to 2035 where it obviously needs to be. This would also allow mid-life investment to occur ensuring that Sentinel R1 Astor capability could continue providing the absolutely vital elements of air power-based specialist deep photographic, intelligence and reconnaissance capability that the UK and our allies required we required. 

Those engaged in the wider air defence community agree that Sentinel R1 Astor capability has proved, over its so far twelve-year service life, to have been formidable wherever deployed. The powerful ‘dual mode’ surveillance radar capability allows for the very best imagery that I have personally ever seen. The ground moving target indicator (GMTI) combined with that of synthetic aperture radar (SAR) imagery is truly fantastic and as already mentioned, the combination of all this provides the UK with unparalleled levels of situational awareness. Sentinel R1 remains a key C4ISTAR (Command, Control, Communication, Computers, Information/Intelligence Surveillance, Target Acquisition and Reconnaissance) asset and the role and importance that it plays can only but continue to grow.

As a crucial capability Sentinel R1 provides the UK and its allies with unprecedented long-range, wide-area battlefield surveillance, the ability to track armoured formations, conduct strategic reconnaissance and to deliver critical intelligence tasks. The data collected and imagery is passed in near real-time within minutes to a team of specialist Intelligence, Surveillance, Reconnaissance (ISR) imagery analysts who are then able to conduct forensic data analysis, generate a variety of intelligence products for time-critical dissemination and that enable commanders on the ground to execute current operations and plan future strategies.

The airframe is based on a Global Express business jet manufactured by Bombardier and which was modified by and subsequently maintained over the past twelve years by Raytheon UK. Sentinel R1 ASTOR capability had originally been intended to support conventional war-fighting operations, track armoured formations and conduct strategic reconnaissance tasks. However, such was the now well proven adaptability and flexibility of Sentinel R1, that the aircraft has also been able to provide crucial intelligence within humanitarian crisis roles – this has included mapping and in 2014, being used for scaling the flood crisis that hit Southern England.

The current Out-Of-Service Date (OSD) for Sentinel R1 (ASTOR) capability is 2021. As mentioned previously, the 2015 Strategic Defence and Security Review process had also reduced the available number of fully operational aircraft from five down to four but the resulting reduction in aircraft and crew capacity, particularly during a time when the Royal Air Force found itself being increasingly deployed internationally, proved difficult. Perhaps the more serious implication and genuine reason to be concerned was that, based on the current rate of anticipate mission requirements, 5(AC) Squadron might no longer have been able to field or sustain sufficient capability in order to meet the level of current demand.

Universally regarded within the military and defence community as being one of the most important assets that the UK currently has within the UK C4ISTAR inventory, my view remains that to lose Sentinel R1 (ASTOR) capability now would be to diminish a very important aspect of C41STAR capability that we continue to need but would leave us open to serious criticism that as a nation, we are pulling back from yet another crucial defence responsibility, but also that we are burying our heads in the sand. As a most powerful and proven piece of the UK ISTAR related air power inventory this is no time for us to let Sentinel R1 ASTOR capability go.

While taking Sentinel R1 Astor capability all the way through to a 2035 OSD creates a requirement for mid-life upgrading, the vital importance that the capability provides to UK and to our NATO allies is in my view fully deserving of long-term commitment and extension to the currently proposed 2021 OSD.

If, as I believe, the decision to withdraw Sentinel R1 capability next year has already been taken I would urge that the Chief of Defence Staff whose task is to ensure that the UK government is now properly advised of the real and underlying value of the crucial asset now before further damage is done and morale further weakened. Just as FinMilCap should also do, CDS should look again at the wider consequences of the UK no longer maintaining what is to me, a very relevant capability in the uncertain world that we live in today. To base a decision such as this on their being no money to support maintaining the Sentinel R1 Astor programme and to base such a decision on process rather than on anything other than a soundly based strategic and operational need would be a national disgrace!

BATTLESPACE Comment: One of the stumbling blocks to retaining Sentinel is the requirement for an upgrade to the existing non-AESA radar which is a derivative of the Raytheon ASARS-2 radar as used on the U2. That radar is reaching the end of its life and thus spares availability. Leonardo could supply its Osprey as a  replacement radar or, as proposed by Northrop in the original ASTOR bid in 1998, the MP-RTIP as supplied to the Global Hawk and Triton UAVs. But, given the budget restrictions and COVID-19 problems, this may be unaffordable. This may usher in a buy of a UAV such as Global Hawk to replace Sentinel?

CHW (London – 13th May 2020)

Howard Wheeldon FRAeS 

Wheeldon Strategic Advisory Ltd,

M: +44 7710 779785

Skype: chwheeldon



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