The Raytheon Sentinel is a retired airborne battlefield and ground surveillance aircraft formerly operated by the Royal Air Force (RAF). While based on the Bombardier Global Express ultra long-range business jet, the prime contractor for the Sentinel was the American defence firm Raytheon, which supplied most of the mission systems and performed the integration work. The type also saw smaller-scale deployments in Ghana and even domestically to assist disaster relief operations.

In 2010, the British government's Strategic Defence and Security Review (SDSR) announced its intention to "withdraw the Sentinel airborne ground surveillance aircraft once it is no longer required to support operations in Afghanistan." The 2010 decision was reversed in 2014 by Prime Minister David Cameron and in the 2015 SDSR, the British government announced that the type's retirement would be delayed and that it would remain in service "into the next decade". Due to the repeated equivocations over its future, the Sentinel did not receive upgrades during its service life. The type was retired in March 2021.

Development

ASTOR can be traced back to the British Army's Corps Airborne Stand-Off Radar (CASTOR) programme, a Cold War-era initiative which sought to bring about an improved surveillance capabilities for monitoring hostile ground forces, with a particular focus on Warsaw Pact forces in East Germany. The support contract for the Sentinel covered 3,200 flying hours per year, and between 2015 and 2018, the five-strong fleet of aircraft had an estimated average running cost of £54.4m/year. This figure does not include standard mid-life updates, which did not take place, that would have increased costs considerably. The main cabin housed 3 workstations at which analysts could analyse the images on board; however, unlike the JSTARS, most of the actual battle management occurred on the ground.

The Sentinel's main radar was a Raytheon dual-mode synthetic-aperture radar / moving target indication (SAR/MTI) radar known as Sentinel Dual Mode Radar Sensor (DMRS). It used active electronically scanned array (AESA) technology, and was related to the ASARS-2 radar used by the Lockheed U-2 reconnaissance aircraft. During 2007, service trials of the Sentinel were conducted. By January 2009, the type had entered regular service with 5 Squadron of the Royal Air Force (RAF), based at RAF Waddington.

In addition to its presence in the Afghan theatre, the Sentinel routinely performed surveillance flights over the Baltic Sea, monitoring military forces stationed in the Kaliningrad Oblast and Belarus; during such missions the type was frequently intercepted by Russian Sukhoi Su-27s.

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."

The Sentinel's role above Libya in 2011 was described as "pivotal" by the head of the RAF. On 30 March 2011, the longest Sentinel flight, of 12 hours and 30 minutes was flown during Operation Ellamy over Libya. While operating along the Libyan coast, it was observed that the Sentinel's dual-mode radar was capable of tracking vessel movements around Libyan harbours, providing viable battlefield intelligence. In February 2014, it was reported that the Sentinel had been used to map the scale of flooding in Southern England. On 18 May 2014, the MoD announced that a Sentinel had departed to Ghana as part of Operation Turus to assist in the search for the 223 schoolgirls abducted by the Islamic militant group Boko Haram in Nigeria on 14 April 2014.

In 2014, Prime Minister David Cameron announced the retention of the aircraft, even after operations end in Afghanistan in Autumn 2018. This reprieve fuelled speculation that not only would the Sentinel be retained but that upgrades of the fleet, particularly for use in a maritime surveillance capacity, might occur. In the absence of UK government backing, Raytheon self-financed development work for over five years on a mid-life upgrade of the Sentinel's mission systems, referred to as Overseer, but this was not applied. However, due to a combination of its operational commitments and constrained budgets, neither the Sentinel or its missions systems received any upgrades for an extended period, which led to some of its onboard systems becoming increasingly obsolescent by the end of the decade. In addition to the Sentinel, the RAF also deployed other surveillance assets, including the Boeing Rivet Joint, General Atomics Reaper, Beechcraft Shadow and Boeing Sentry, for surveillance missions over Iraq and Syria around this time.

Despite the RAF reportedly hoping to retain the entire five-strong fleet, Accordingly, in July 2017, one of the five aircraft was permanently withdrawn. During the following month, the type was formally withdrawn from RAF service. years, the five aircraft flew approximately 32,300 hours roughly distributed across 4,870 sorties.

On 16 November 2021, according to UK Defence Journal, the MoD accepted a proposal from Raytheon/Bombardier to purchase and refurbish the airframes for ultimate use by the United States Army."

  • No. 54 Squadron (Operational Conversion Unit)

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See also

References

Citations

Bibliography

  • Winchester, Jim. "Aircraft of the RAF Part 5 – Raytheon Sentinel R1". Air International, Volume 75 No.&nbsp;3, September 2008. pp.&nbsp;54–57.
  • Raytheon UK: ASTOR
  • Raytheon: ASTOR
  • ASTOR is born
  • RAF – Sentinel R1/ASTOR