About the Sentinel R1


The Sentinel R.Mk 1 provides long-range, wide-area battlefield surveillance, delivering critical intelligence and target tracking information to British and coalition forces.  The aircraft has been operationally deployed in support of operations in Afghanistan, Libya and Mali, and is currently deployed in support of British and Coalition operations in Iraq and Syria. 


Using its powerful multi-mode radar, the Sentinel’s mission crew identifies, tracks and images numerous targets over great ranges, passing the information in near real time to friendly forces.  A team of intelligence imagery analysts from 1 Intelligence, Surveillance, Reconnaissance (ISR) Wing backs up the Sentinel crews, conducting in-depth forensic analysis of collected data, and using it to generate intelligence products for time-critical dissemination to commanders and decision makers, enabling them to execute current operations and plan future strategies.  

Sentinel engine start for an Op Shader mission.
Engine start for an op's mission.
Image by: Cpl Graham Taylor


During the early 1980s, the UK government identified a need for a battlefield reconnaissance system to provide awareness over a broad area.  Expressed in the Corps Airborne Stand-Off Radar (CASTOR) requirement, the programme elicited responses from Thorn-EMI and Ferranti.  The former’s radar was tested in an English Electric Canberra from 1982, while a Britten-Norman Islander modified to take the latter, first flew in 1984.

By 1988 the programme had become ASTOR and, with a Thorn-EMI radar installed, the Islander flew low-altitude trials examining its compatibility with the USAF’s prototype E-8 J-STARS (Joint-Surveillance Target Acquisition Radar System).  This work was part of a definition phase which, it was hoped, would enable a contract award in 1994.

Finally, in 1999, Raytheon was contracted to develop a five-aircraft ASTOR system, using Bombardier’s Global Express business jet as the airborne platform and basing the mission system on its ASARS-2 radar, developed for the USAF’s U-2.  Raytheon took a first Global Express for modification in 2002 and re-flew it with the ASTOR system installed in May 2004.  Service trials began in 2007 and V(AC) Sqn flew the first operational Sentinel R.Mk 1 mission in November 2008.

The aircraft immediately proved its worth over Afghanistan and again during Operation Ellamy in 2011, becoming a vital link in the chain of target identification and prosecution, especially where fleeting or ‘pop-up’ targets were concerned.  The 2010 Strategic Defence and Security Review nominated Sentinel for withdrawal as soon as the Operation Herrick commitment ended, but such was the system’s value to British and allied commanders that it was given a reprieve.  Since then it continues to prove its worth in Operation Shader and as a result of the 2015 Strategic Defence and Security Review, its out of service date has been moved back to 2021.

Header image by Sgt Laura Bibby

Based at


Raytheon Sentinel R.Mk 1:

  • Powerplant: two 14,750lb st (65.60kN) Rolls-Royce Deutschland BR710 turbofan engines
  • Length: 99ft 5in (30.30m)
  • Height: 27ft (8.23m)
  • Wingspan: 93ft 5½in (28.49m)
  • Wing area: 1,022sqft (94.95m2)
  • Maximum speed: 530kt (982km/h)
  • Range: more than 5,000nm (9,260km)
  • Maximum altitude: more than 40,000ft