Raytheon Sentinel

A close-up of the Sentinel's radar pod.

ZJ690 on trials in 2007

A Sentinel R1 taking off from RAF Akrotiri in support of Operation Shader.

ASTOR has its roots in the British Army's Corps Airborne Stand-Off Radar (CASTOR) programme which in 1984 modified a Britten-Norman Islander (G-DLRA/ZG989) with a large nose radome for battlefield surveillance. The 1991 Gulf War confirmed the requirement for such an aircraft, but the end of the Cold War made funding difficult. The production contract was signed in December 1999 with a projected in-service date of 2005.

The Sentinel R1 is a modified Bombardier Global Express powered by two Rolls-Royce BR700 turbofan engines. The programme involved five aircraft and eight mobile ground stations (six on wheeled all terrain vehicles and two in air transportable containers), and a training facility at RAF Waddington. The programme cost £850 million, as budgeted.[6] The support contract is for 3200 flying hours per year[7] and between 2015–18 the fleet of five aircraft will have average running costs of £54.4m/year.[8]

The Sentinel cockpit has a centrally housed, pull-down screen capable of displaying a moving map, Link 16 datalink information and defensive aids subsystem (DASS) data. The DASS comprises a towed radar decoy, missile approach warning system and chaff and flare dispensers and can be operated in automatic, semi-automatic or manual mode.

The aircraft normally operates at over 40,000 feet (12,000 m) to ensure a high resolution view of a large battlefield area. It is crewed by a pilot, a co-pilot, an Airborne Mission Commander (AMC) and two image analysts. Mission endurance is approximately nine hours.[1] While the image analysts can analyse the images on board the aircraft it is expected that, unlike the JSTARS, the actual battle management will occur on the ground.

The main radar is a Raytheon dual-mode synthetic aperture radar / moving target indication (SAR/MTI) radar known as Sentinel Dual Mode Radar Sensor (DMRS). It uses AESA active electronically scanned array[9] technology. Raytheon claim it could be modified to match the maritime surveillance capability of the cancelled Nimrod MRA4, and the ground stations could be adapted to receive data from Watchkeeper, MQ-9 Reaper and the future Scavenger programme.[6] A contract for the development of a maritime capable software upgrade will be placed in the spring of 2015;[10] Jane's speculates that this would allow the Sentinel to detect surface vessels and potentially submarine periscopes and that other sensors could be fitted as a 'low-end' capability for maritime surveillance to complement a 'high-end' platform such as the P-8A Poseidon.[11][12]

The first flight of the modified prototype, which validated the modifications required for the ASTOR system, was in August 2001. The first production Sentinel R1 made its 4.4-hour maiden flight on 26 May 2004.

The aircraft entered operational service with 5 Squadron of the Royal Air Force based at RAF Waddington[13] and flew its first operational sortie over Afghanistan on 15 Nov 2008.

In 2010 the UK government's Strategic Defence and Security Review announced its intention to "withdraw the Sentinel airborne ground surveillance aircraft once it is no longer required to support operations in Afghanistan."[2] Sentinel has supported the British Army in Afghanistan. Its role above Libya in 2011 was described as "pivotal" by the head of the RAF.[14] In February 2012 it was announced that Sentinel would be offered as the UK contribution to NATO's Alliance Ground Surveillance (AGS) collaboration, complementing NATO RQ-4 Global Hawks and French Heron TPs.[15]

On 25 January 2013, the British Government announced that the RAF would deploy one Sentinel aircraft from RAF Waddington, in support of French operations in Mali.[16] On 14 February 2014, it was reported that the Sentinel was used to map the scale of flooding in Southern England.[17] On 18 May 2014, the MoD announced that a Sentinel had departed to Ghana to assist in the search for the 223 schoolgirls abducted by the Islamic militant group Boko Haram in Nigeria on 14 April 2014.[18]

In 2014, Prime Minister David Cameron announced the retention of the aircraft, even after operations end in Afghanistan in fall 2018.[19]

On 26 March 2015, the MOD announced the deployment of two Sentinel aircraft to provide surveillance to coalition forces fighting as part of the Military intervention against ISIL.[20]

It was announced that the fleet would be cut to four aircraft with effect from 1 April 2017 and the service date extended to 2021.[21]

 United Kingdom

• Royal Air Force
  • RAF Waddington, Lincolnshire, England
    • No. V (AC) Squadron[22]
    • No. 54 Squadron (Operational Conversion Unit)[22]
    • No. 56 Squadron (Test and Evaluation)[22]

Data from Royal Air Force[23]

General characteristics

• Crew: 5
• Length: 99 ft 5 in (30.30 m)
• Wingspan: 93 ft 6 in (28.50 m)
• Height: 27 ft 0 in (8.23 m)
• Wing area: 1,022 sq ft (94.9 m²)
• Empty weight: 24,000 lb (10,886 kg)
• Gross weight: 42,400 lb (19,232 kg)
• Powerplant: 2 × Rolls-Royce BR710 turbofan engines, 14,750 lbf (65.6 kN) thrust each

Performance

• Maximum speed: Mach 0.89
• Range: 4,994 nmi (5,747 mi, 9,249 km)
• Endurance: 9 hours
• Service ceiling: 49,000 ft (15,000 m)

• Airborne Early Warning and Control (AEW&C)

Related development

• Bombardier Global Express

Aircraft of comparable role, configuration and era

• E-8 Joint STARS
• Embraer R-99B

Related lists

• List of aircraft of the Royal Air Force
• List of active United Kingdom military aircraft

General

• Winchester, Jim. "Aircraft of the RAF Part 5 – Raytheon Sentinel R1". Air International, Volume 75 No. 3, September 2008. pp. 54–57.

Wikimedia Commons has media related to Raytheon Sentinel.

• Raytheon UK: ASTOR
• Raytheon: ASTOR
• ASTOR is born
• RAF – Sentinel R1/ASTOR