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47-633: 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. Originally known as

94-465: A class of military airborne radar system ( Surveillance aircraft ) used for detecting and tracking ground targets, such as vehicles and slow moving helicopters, as opposed to Airborne early warning and control , whose primary role is detecting and tracking aircraft in flight. Antenna beam width should be very small to enhance resolution. This antenna size limitation demands high frequency (GHz range) of operation, to be operated in this mode. AGS radar

141-486: A large nose radome for battlefield surveillance to explore this concept. Experiences gained during the 1991 Gulf War confirmed the requirement for such an aircraft, but the end of the Cold War had somewhat undermined the traditional justification to process, along with a series of rapid defense budget cuts that made funding of any new acquisitions particularly challenging during that time. Despite this, during December 1999,

188-495: A production contract was signed with the American defence firm Raytheon to supply what would become the Sentinel. The programme involved five aircraft and eight mobile ground stations (six on wheeled all-terrain vehicles and two in air-transportable containers), along with a training facility at RAF Waddington. Four of the five Sentinels were integrated at Raytheon's facility in Broughton, Flintshire ; various support series provided by

235-591: A reduced time-to-impact. Most users would tolerate an increased FAR (up to some point where it starts limiting operations) instead of a reduced TTI, because their probability of survival depends fairly directly on the TTI, which represents the time in which countermeasures can be deployed. Accurate azimuth and elevation angle of attack (AOA) information can be another very important requirement. Directional IR counter measures (DIRCM) systems depend on MAW systems for accurate enough initial pointing (about two degrees) to ensure that

282-416: A small but visible radar signature and also a propellant which burns – depending on the platform, typically for a very short duration. MANPADS are relatively short-range weapons, typically up to about five kilometers with the heart of the kill envelope one to three kilometers. They therefore allow very little margin for error to effectively counter them as the time to impact (TTI) on a target at one kilometer,

329-450: A visual positive identification capability; while the addition of an electro-optical / infrared sensor to the Sentinel's canoe fairing to provide complimentary imagery was proposed, this option was never exercised. On 3 August 2001, the first flight of the aerodynamically modified Global Express prototype occurred, which validated the modifications required for the ASTOR system. On 26 May 2004,

376-584: Is limited. If a platform is equipped with both radar and missile warning systems, the HMI should display both threats clearly and unambiguously. The integrated HMI must also indicate the system's operating status, serviceability status, mode of operation, remaining decoy quantities etc. Separate control panels are justified only for safety of flight purposes such as ECM on/off and decoy jettison functions. Procuring electronic warfare (EW) self-protection systems has direct and indirect cost implications. Direct costs involve

423-588: Is no longer required to support operations in Afghanistan." 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 . 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

470-468: 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

517-431: Is only about three seconds. The TTI for targets at three and five kilometers is also relatively short – only seven to a little over eleven seconds respectively. The MAW must provide reliable and timely warning to allow appropriate counter measure responses. Near 100% probability of warning (POW) and very fast reaction times to counter nearby missile launches (in the order of one second) are essential. Air crew will rely on

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564-429: Is typically a medium or low power radar. It includes both maritime and land surveillance. Today, UAVs perform this operation, which often uses optical aids for surveillance. This article related to sensors is a stub . You can help Misplaced Pages by expanding it . Missile approach warning system Guided surface-to-air missile (SAM) systems were developed during World War II and began to make their presence felt in

611-557: The ASTOR (Airborne STand-Off Radar) programme, procurement of the type started during 1999. Following its delivery in 2007, the Sentinel fleet was operated by an RAF squadron manned by both air force and army personnel. The Sentinel was interoperable with other allied systems such as JSTARS and the NATO Alliance Ground Surveillance (AGS) system. Sentinels were deployed overseas on multiple occasions, such as in support of

658-1099: The SA-7 could be as low as $ 5,000. Intelligence regarding the whereabouts of MANPADS, especially in the hands of "non state" organizations, is usually vague and unreliable. This, in turn, makes it difficult to anticipate where and when to expect MANPADS attacks. The 2nd- and 3rd-generation MANPADS that appeared by the 1980s further increased the performance and effectiveness of MANPADS due to advanced new seeker head technology, improved rocket motors, and aerodynamic refinements. Their performance improved in terms of lethal range, minimum launch angle, maneuvering potential and all aspect engagement angles (1st-generation MANPADS were restricted to only rear sector attacks). They also became more electronic counter-countermeasure (ECM) resistant. MANPADS therefore became even more lethal specifically against more vulnerable platforms such as helicopters, light aircraft, and commercial and military transport aircraft (during approaches and departures). The slower speed of these platforms forces them to spend more time within

705-655: The 1950s. In response, electronic countermeasures (ECM) and flying tactics were developed to overcome them. They proved to be quite successful provided that a reliable and timely threat warning was given. Analysis of aircraft losses due to enemy action since the 1960s shows that at least 70% of all losses were attributed to passive heat seeking i.e. infrared (IR) guided missiles . This might be surprising given that radar guided SAM systems have longer engagement ranges, are faster, have higher maneuvering potential, carry larger warheads and are equipped with proximity fuzes . The main reason why IR guided missiles were so effective

752-478: The 1960s. IR MANPADS are relatively cheap, quite robust, easy to operate and difficult to detect. They also do not require the infrastructure, such as radar dishes, associated with radar-guided SAM deployments which often reveals their presence. Vast quantities of MANPADS have been manufactured (as many as 700,000 produced since 1970 ). Large numbers proliferated during the Cold War and immediate post Cold War era. Substantial quantities are available and affordable on

799-441: The 1970s and when the correct jamming modulation techniques were applied, were reasonably effective against 1st-generation amplitude-modulated MANPADS, which operated in the near-IR band (1 to 2 micrometres (μm)). The arrival of 2nd- and 3rd-generation MANPADS changed that. They operate in the mid-IR band (3 to 5 μm) and use more advanced modulation techniques (for example frequency modulation). Instead of jamming these missiles,

846-589: 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

893-705: The British Army in Afghanistan , coalition forces in Libya , and to assist French forces deployed in Mali . 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

940-455: The DIRCM acquires and engages incoming missiles timely and successfully. Accurate AOA is also important in deciding the dispensing direction of the counter measure decoys (flares). It is vital to avoid the situation where the platform and the dispensed decoys both remain within the instantaneous field of view (IFoV) of incoming missiles. In situations like that missiles could very well, once they pass

987-513: The MoD accepted a proposal from Raytheon/Bombardier to purchase and refurbish the airframes for ultimate use by the United States Army ." Data from Royal Air Force General characteristics Performance Related development Aircraft of comparable role, configuration, and era Related lists Airborne ground surveillance Airborne ground surveillance (AGS) refers to

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1034-480: The POW. Since a longer time-to-impact (TTI) warning is almost invariably desirable, this leads to the conclusion that there is something like a too-low FAR: all warning systems gather data, and then make decisions when some confidence level is reached. False alarms represent decision errors, which (assuming optimal processing) can be reduced only by gathering more information, which means taking more time, inevitably resulting in

1081-507: The RAF reportedly hoping to retain the entire five-strong fleet, it was announced, while the type's service date would be extended into 2021, that the number of operational Sentinels would be cut to four aircraft with effect from 1 April 2017. Accordingly, in July 2017, one of the five aircraft was permanently withdrawn. The long-term retention of the platform would have necessitated significant expenditure to modernise aging systems, which strengthened

1128-407: 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. Upgrades for the Sentinel were planned to take place; during 2014,

1175-466: The Sentinel would be flown at altitudes in excess of 40,000 feet (12,000 m) to ensure a high resolution view of a large battlefield area. It was crewed by a pilot, a co-pilot, an Airborne Mission Commander (AMC) and two image analysts. Mission endurance was approximately nine hours. The main cabin housed 3 workstations at which analysts could analyse the images on board; however, unlike the JSTARS, most of

1222-409: The UK government announced that a contract for the type to receive a maritime-capable software upgrade was to be placed in the spring of 2015; 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

1269-511: 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. Raytheon claimed that

1316-461: The black market and have found their way into the hands of "non state" organizations or the so-called "asymmetric" threat. (An estimate by Jane's Intelligence Review of February 2003 puts this number as high as 150,000 ). An article "Proliferation of MANPADS and the Threat to Civil Aviation" of August 13, 2003 by Jane's Terrorism and Insurgency Centre estimates that the black market price of MANPADS like

1363-504: The company during the type's service life, including deep maintenance and upgrade work, were also undertaken at Broughton. The Sentinel programme cost £850 million. 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 Sentinel R1

1410-639: The decade. On 26 March 2015, the MOD announced the deployment of two Sentinel aircraft in support of Operation Shader to provide surveillance to coalition forces fighting as part of the Military intervention against ISIL . 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

1457-513: The decision to withdraw the entire Sentinel fleet during March 2021. Planners determined that new aircraft, such as the Poseidon MRA1 maritime patrol aircraft and the forthcoming Protector UAV, would carry out the surveillance duties formerly performed by the type. Thus, on 25 February 2021, Sentinel ZJ694 completed the type's final operational flight when it returned to RAF Waddington from a mission flown near Kaliningrad Oblast and Belarus. During

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1504-488: The decoy's ejection velocity. A turn towards approaching missiles to establish/increase the angle between the decoy and the platform is especially important in cases where a missile approaches from the rear between the five or seven 'o clock sectors. If the AOA is not accurate enough, the pilot could very well turn in the wrong direction and set himself up for the situation as described above. The system must also be fully automated as

1551-415: The decoys, still hit the platform. This is of particular importance where separation between the decoys and the platform takes too long as is the case with slow flying aircraft. Accurate AOA is further important where the platform should preferably maneuver when dispensing decoys to increase the miss distance. This is more applicable to fast jets where their high speed tends to negate the separation caused by

1598-416: The first production Sentinel R1 performed its maiden flight , lasting for 4.4 hours. During 2007, service trials of the Sentinel were conducted. The first operational sortie over Afghanistan in support of the British Army commenced on 15 November 2008. 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

1645-459: The following month, the type was formally withdrawn from RAF service. During their service life of 12.5 (stated in a RAF tweet as 14) years, the five aircraft flew approximately 32,300 hours roughly distributed across 4,870 sorties. Following their withdrawal from RAF service, the aircraft were sold to a US consortium of Springfield Air, Raytheon US, and Bombardier in an unairworthy condition. On 16 November 2021, according to UK Defence Journal ,

1692-511: The human reaction time in relevant cases (short range launches) is too long. Light aircraft, helicopters, and fighters usually have limited space and mass capacity for additional equipment. The system may also cause adverse aerodynamic drag which demands minimal physical size and number of boxes. The power consumption must further be kept within the capacity of the platform's electrical system. Integrated display and control functions are desirable to avoid duplication on instrument panels where space

1739-421: The initial price of the system, spare parts as well as test equipment to ensure that the performance and availability of the systems is maintained throughout their entire life cycle. Installing and integrating EW systems on aircraft is another direct cost Indirect cost on the other hand involves degradation of the aircraft's performance as a result of having the system on-board which in turn impacts negatively on

1786-611: The kill zones of MANPADS compared to high performance fighter and strike aircraft. Over fifty MANPADS attacks on civilian aircraft are on record to 2007. Thirty-three were shot down killing over 800 people in the process. Protecting aircraft against IR guided missiles depends in most cases firstly on reliable detection and warning of missiles and secondly on applying effective ECM. An exception to this are omni-directional IR jammers which do not make use of missile warning at all, as they simply radiate modulated IR energy for as long as they are switched on. These jammers have been around since

1833-441: The omni-directional IR jammer became a source for the missiles to home in. Providing timely warning against IR MANPADS is a challenge. They give no warning of their presence prior to launch, they do not rely on active IR, radar guidance or a laser designator, which would possibly emit a detectable radiation. They are typically fire-and-forget and can lock on and engage a target, speed to the target and destroy it in seconds. They have

1880-698: The operating cost of the aircraft. The lowest initial price of a system does therefore not necessarily offer the best solution as all the factors needs to be considered. The overall cost effectiveness of systems i.e. price versus performance is more important in deciding which system to select. Three different technologies have been used for MAW systems, i.e. systems based on: Pulse-Doppler radar , Infrared , and Ultraviolet . Each technology has its advantages and disadvantages which can be summarized as follows: Current available MAW systems as well as those under development, represent all three types of technologies. Each technology has strong and weak points and none provide

1927-482: The radar 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 different types of unmanned aerial vehicles (UAVs), including the Watchkeeper , MQ-9 Reaper and the future Scavenger programme. The imagery produced by the radar's synthetic aperture mode was incompatible with the UK's rules of engagement necessitating

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1974-406: The system only if they have high confidence in it. The MAW must also have sufficiently low false alarm rates (FAR), even when illuminated by multiple sources (which may include threats) from different directions. Quick response times and low FAR are inherently conflicting requirements. An acceptable solution requires a balanced approach to provide the most successful end result without compromising

2021-482: Was a modified Bombardier Global Express powered by two Rolls-Royce BR700 turbofan engines. The cockpit featured a centrally positioned pull-down screen capable of displaying a moving map, along with Link 16 datalink information and defensive aids subsystem (DASS) data. The DASS comprised a towed radar decoy , missile approach warning system , and chaff and flare dispensers which could be operated in automatic, semi-automatic or manual mode. In typical operations,

2068-550: 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. On 25 January 2013, the British Government announced that the RAF would deploy one Sentinel aircraft from RAF Waddington, in support of Operation Newcombe in Mali . In February 2014, it

2115-774: 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

2162-506: Was retired in March 2021. 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 . In 1984, a single Britten-Norman Islander (G-DLRA/ZG989) was modified with

2209-585: Was that it took much longer to develop effective warning systems against them. Most aircraft that were shot down never knew that the missiles were coming. Radar warning receivers on the other hand already proved their effectiveness by the early 1970s which considerably improved the survival rate of aircraft against radar threats. The first air-to-air IR missiles appeared in the 1950s. The technology allowed more compact missile designs and made it possible to develop IR man-portable air-defense systems (MANPADS) i.e. shoulder-launched missiles, which became operational by

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