The radar operates at high altitude and in all weathers to provide high resolution. ASARS-2 has been reported to provide images of the battlefield at ranges of 160 km, at altitudes up to 47,000 feet. High speed data links transfer the data from aircraft to ground stations in near real time. The system has directional and broadcast data links which are interoperable with existing US U-2Rs, JSTARS and command and control networks. The first aircraft were received by No 5 (AC) Squadron in early 2007. The MoD has spent £954m on five aircraft plus eight ground stations to be operated by 5 (Army Co-operation) Squadron, based at RAF Waddington in Lincolnshire.
Sentinel R1 - ASTOR Specifications:
2 RAF Pilots. 1 RAF Mission Commander. 2 Image Analysts (either RAF or Army Intelligence Corps).
-Max Take-Off Weight
2 x RR BR710
ASARS-2 radar derivative
Narrowband datalink subsystem (NDLS), wideband data link based on Common Data Link (CDL)
-Defensive Aids Subsystem (DASS)
Developed for the Nimrod MRA4, including missile warning system, radar warning receiver, towed radar decoy and chaff and flare dispensers
After the 1990 Gulf War, it was identified by the allies that Intelligence, Surveillance and Reconnaissance had played a key role in the success of this operation. In particular, the use of Synthetic Aperture Radar (SAR) and Ground Moving Target Indicator (GMTI) had proved invaluable in the tracking and prosecution of enemy ground forces. This galvanised the UK to acquire its own capability and in 1993 the requirement was endorsed by the MOD.
The solution chosen by the MOD was the Airborne STand-Off Radar (ASTOR) to be known as the Sentinel system. The Sentinel system consists of Air, Land and Support segments. The Air segment consists of 5 converted Bombardier Global Express aircraft, named the Sentinel R1, fitted with a Dual Mode Radar (DMR). This radar is similar to the U2 ASARS radar, and collects SAR imagery and GMTI data. The Land segment consists of 2 transportable Operational Level Ground Stations (OLGS) and 6 mobile Tactical Ground Stations (TGS). These ground stations (GS) are connected to the aircraft via data links and provide Near Real Time (NRT) intelligence to commanders and their staffs at multiple levels of command.
5(Army Co-operation) Sqn operates the Sentinel system and is based at RAF Waddington. It is a joint sqn, commanded by an RAF Wing Commander. With over 150 RAF and 100 Army service personnel, 5(AC) Sqn is the largest flying sqn in the RAF. The aircraft are manned by two RAF Pilots and a Mission Commander, whilst the intelligence gathered by the aircraft is analysed by 2 on-board Image Analysts (IAs) for NRT effect. The on-board IAs are a mix of RAF and British Army Intelligence Corps SNCOs. The GS provide a longer term analytical capability to answer more in-depth questions and Requests for Information (RFIs). The GS are staffed by IAs from the Intelligence Corps and RAF, and supported by R Signals and REME technicians, both at RAF Waddington and the deployed operating base.
Sentinel was originally intended for conventional war-fighting operations, to track armoured formations and conduct strategic reconnaissance tasks. However, the capability has been shown to be flexible and has been adapted for use in a number of different roles by 5(Army Cooperation) Sqn. The Sentinel’s value has been proven in support of counter-insurgency operations in Afghanistan, and in 2011 the capability provided vital Intelligence to enable coalition air assets to protect civilians from pro-Gaddafi Forces under UN Security Council Resolution 1973. Sentinel is deployed on an enduring basis, providing International Security Assistance Force (ISAF) with operational and tactical intelligence which is having a tangible effect on the success of coalition operations in Afghanistan.
As part of the Strategic Defence and Security Review (SDSR) of 2010 it was announced that the SAR and GMTI capability Sentinel provides would be retained by the UK until the UK’s involvement in Op HERRICK had ceased. 5(AC) Sqn will continue to operate the Sentinel system until a suitable platform has been developed onto which this valuable capability can be transferred. Until that point, 5(AC) Sqn and Sentinel will remain at the forefront of Intelligence, Surveillance and Reconnaissance (ISR) for the RAF in support of operations in Afghanistan.
Reprieve for axed Sentinel R1 spy plane
23 November 2011.-
The decision to scrap the Sentinel spy plane under defence cuts is to be reviewed.
Head of the RAF Air Chief Marshal Sir Stephen Dalton says the Sentinel R1 - fitted with sophisticated radar imaging equipment - played a "pivotal" role in spotting and identifying Colonel Gaddafi's forces and should be retained.
Under the Strategic Defence and Security Review, all five of the RAF's Sentinel aircraft have been listed for withdrawal from service by 2015. However, Air Chief Marshal Dalton has indicated it could be in line for a reprieve in the light of the aircraft's performance in Libya. In an interview with BBC Radio 4's The World At One he said: "Whenever we have had an operation we then have to go back and have a look at whether the assumptions we made before or during were correct.
"The value of Sentinel and the value of the picture it provided was so critical that I think we will need to have another look and see what way we can provide that capability in the future."
The aircraft had been particularly important in convincing the politicians that international forces were able to identify accurately and hit targets on the ground, he said.
"Sentinel was pivotal to be able to provide the picture - the picture in electronic terms, the picture in imagery terms - so that our intelligence was well-placed therefore to identify those targets and to precisely target against them," he said.
"It was also important because we were able to demonstrate that to lawyers, to the targeteers, to the politicians, that we could see what was going on, we could identify them moving as well as the static, and we could therefore focus on what was important to achieve the overall effect."
Parliament Home Page.
Session 2010-12/HC 950 Operations in Libya.
Written evidence from Raytheon UK.-
Raytheon UK is pleased to submit this written evidence in support of the Defence Committee’s inquiry into Operations in Libya. In particular this evidence is submitted with respect to the question posed about the implications of this operation for the outcomes of the Strategic Defence and Security Review (SDSR).
The Airborne Standoff Radar (ASTOR) program that includes the Sentinel R Mk1 as the aircraft element was launched in December 1999 as a key component of the Armed Forces Intelligence, Surveillance, Target Acquisition and Reconnaissance (ISTAR) capability to become the country’s future key ground surveillance capability. It provides surveillance over a wide area; the ability to focus on a discreet area of interest; and the ability to identify moving targets. Using a business jet enables the sensor to be flown much higher than larger aircraft thus greatly extending the range of radar coverage.
Raytheon delivered the programme to the original target cost of £850 million and went from concept to operational capability, deployed in theatre in just over eight years, a significant achievement for what was an extremely complex and technically ambitious programme.
The Strategic Defence and Security Review announced the retirement of the RAF’s fleet of five Sentinel R Mk 1 aircraft on completion of the support to ongoing operations in Afghanistan circa April 2015.
Support to Operation Ellamy
The Sentinel R Mk1 has been providing strategic ISTAR support to the UK and NATO since the beginning of operations in Libya. It has achieved a greater than 97% level of availability. The Sentinel capability has been critical in delivering data to support the general intelligence picture and also to identify specific targets for the strike force. The platform has been at times the only strategic ISTAR platform available and hence has been pivotal to the execution of tasking in support of the objectives of the coalition. The performance of both the platform and the support provided by Raytheon to the operations has been formally acknowledged and praised by the front line command.
The Sentinel R Mk1 has proven its critical role in support of both Operation Ellamy and Operation Herrick providing a wide area surveillance capability that currently can only be delivered by a few assets. It has been relied upon by the collation forces on a number of occasions, and is one of the few capabilities that the UK can deploy that can demonstrably add immediate value to the operation.
The Strategic Defence and Security Review announced the retirement of the RAF’s fleet of five Sentinel R Mk 1 aircraft on completion of the support to ongoing operations in Afghanistan circa April 2015. This decision leaves the UK without a viable wide area ground surveillance capability. Raytheon’s understanding is that the MoD believes that wide area surveillance can be provided by a combination of the Scavenger capability, the procurement of which has not yet commenced, and the Joint Strike Fighter (JSF).
However, whilst these programmes may provide a ground surveillance capability, they are intended to provide coverage complementary to Sentinel’s wide area capability. JSF and Scavenger will be optimised for local area surveillance provided by smaller sensors and less powerful processing capability. Unmanned assets like Scavenger need cueing from very wide area pattern of life based product libraries and without Sentinel, another means will be needed to update these databases in near real time. We are not aware of MoD plans to provide this capability.
With the JSF not due to enter into service until between 2017 and 2020 and Scavenger not planned to deliver an operational capability until sometime after 2018, there remains a risk of no capability in this area for a significant period of time.
The Sentinel system also has a valuable role in communications. The Ground Station currently provides the coalition forces with the only means of interoperation with JSTARS which will be lost when Sentinel is retired.
Furthermore this loss will have an effect on potential plans for the long range deployment of UAVs, for which radio relay of data may be required, especially if SATCOM bandwidth is limited or not available. Sentinel’s high altitude ceiling has been utilised in this way by the USAF using the original ASTOR demonstrator GEX 9001 as a trials aircraft operating out of Afghanistan.
The Battle Against IEDs
In addition to its pattern of life picture that Sentinel currently provides, the system could assist further in the battle against IEDs due to the inherent quality of the raw data provided. Offboard post processing trials have proven that there is the capability to identify disturbed earth and cue the identification of IED locations. The Sentinel aircraft does not require any modifications in order to deliver this near real-time IED detection capability. Therefore, with minimal additional outlay, further trials could be undertaken with in theatre data to refine this capability, and potentially help to reduce the casualty figures in theatre.
Such a capability is considered essential given the latest trend in warfighting scenarios, and would be valuable, not just for current operations in Afghanistan, but wherever the next theatre of interest lies. Afghanistan has proven that terrorism will likely continue to revolve around insurgency and IED based threats, a scenario that the current platforms have difficulty in addressing over wide areas.
The ASTOR System has untapped capability that with incremental investment could deliver significantly enhanced capabilities. This spiral capability development would be a more cost effective and lower risk way of delivering new capability, rather than investing in the development and entry into service of new platforms.
The SDSR decision to cancel the Nimrod MRA4 leaves the UK with maritime capability gaps that the Sentinel R Mk 1 capability could address, including:
·Deep sea search and rescue maritime target detection;
·Scene of Action presence for maritime emergencies beyond the range of current Sea King helicopters;
·Overhead naval force protection; and
·Wide area submarine threat detection.
The Sentinel Dual Mode Radar Sensor (DMRS) could be modified to accept a high sea state target detection capability that would match and possibly even surpass that lost by the cancellation of the Nimrod MRA4. This capability is already in service in the US.
In addition the ASTOR Ground Station could be upgraded, with relatively little investment, to provide a multi ISTAR hub for the reception of information feeds from Watchkeeper, Reaper and, in the future, Scavenger. This would fit well into the future plans for the Solomon programme, as we understand them, maximising reuse of existing assets, saving valuable resource and costs.
Sentinel R Mk 1 has proven invaluable to operational success in Libya and Afghanistan.
The SDSR decision to retire Sentinel leaves the UK with capability gaps covering significant wide area pattern of life surveillance, long range target detection and coalition force interoperability.
Retirement of Sentinel leaves the UK with vital capability gaps some of which may be filled by new platforms in the 2020 -2024 timeframe, but not all.
In addition spiral development of the proven Sentinel capability could deliver solutions to capability gaps left by other SDSR decisions, such as maritime search and rescue, and deep sea threat detection, at significantly lower cost and risk, than developing and deploying new platforms.