Airborne Maritime Surveillance Radar, Volume 2

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This content has been downloaded from IOPscience. Please scroll down to see the full text.Download details:IP Address: 209.126.2.32This content was downloaded on 23/06/2021 at 03:21Please note that terms and conditions apply.You may also be interested in:Airborne Maritime Surveillance Radar, Volume 1: ASV radar developmentS WattsAirborne Maritime Surveillance Radar, Volume 1: ConclusionsS WattsAirborne Maritime Surveillance Radar, Volume 1: ASV Mk. I and IIS WattsAirborne Maritime Surveillance Radar, Volume 1: ASV Mk VIIS WattsAirborne Maritime Surveillance Radar, Volume 1: Comparative performance assessmentS WattsResearch on Radar Importance with Decision MatrixLingjie Meng, Yu Du and Liuheng WangMeteorology: What multiple parameter radars can revealDesign of Radar Signal Playback Module Based on FPGAJing He and Yang LiuMicrowave Doppler radar in unobtrusive health monitoringP Silva Girão, O Postolache, G Postolache et al.

IOP Concise PhysicsAirborne Maritime Surveillance Radar, Volume 2Post-war British ASV radars 1946–2000Simon WattsChapter 1Introduction1.1 ASV radarsToday, air-to-surface vessel (ASV) radars, or more generally airborne maritimesurveillance radars, are installed on maritime reconnaissance aircraft for long-rangedetection, tracking and classification of surface ships (ASuW—anti-surface warfare)and for hunting submarines (ASW—anti-submarine warfare). These aircraft andtheir radars also play an important role in maritime search and rescue, in times ofpeace as well as hostilities.The first ASV radars were developed in the UK during WWII, as part of theresponse to the threat to shipping from German U-boats. These radars are describedin a companion volume [1]. This book describes the ASV radars developed in theUK after WWII for use by RAF Coastal Command and its successor, after 1969, inRAF Strike Command. These were used between 1946 and 2010 in the RAF’sdedicated maritime patrol aircraft, including the Lancaster GR.3, the ShackletonMR1, MR2 and MR3 and then the Nimrod MR1 and MR2.1.2 RAF Coastal Command and Strike CommandRAF Coastal Command was set up in 1936, having previously been known as theCoastal Area of the RAF. On 1st September 1937 its role was defined in an AirMinistry Directive to the Air Officer Commanding-in-Chief as ‘trade protection,reconnaissance and co-operation with the Royal Navy’. The provision of airbornereconnaissance reports of surface ships was a key requirement and this could beseriously hampered by poor visibility, bad weather and darkness. The advent ofradar to detect our own ships and to find and fight the enemy at sea would bringabout major changes in the function of aircraft in maritime warfare.A comprehensive history of Coastal Command is given in the book by CAshworth [2] and the story of its wartime years is given in the book by A Hendrie[3]. By September 1939 Coastal Command had 19 squadrons, flying Anson,Vildebeest, Hudson, London, Stranraer and Sunderland aircraft, with a totaldoi:10.1088/978-1-6432-7072-2ch11-1ª Morgan & Claypool Publishers 2018

Airborne Maritime Surveillance Radar, Volume 2establishment of 242 aircraft [3]. Many of these aircraft were obsolete and, apartfrom the Hudsons and Sunderlands, not suitable for the anti U-boat role that was tocome. By April 1945, the Coastal Command battle line, engaged in anti-submarinewarfare and anti shipping operations, comprised 40 RAF squadrons, with two FAA,one SAAF and six USN squadrons, representing a total establishment of 765aircraft, of which 481 were available for operations. The aircraft included Liberator,Wellington, Sunderland, Catalina, Barracuda, Beaufighter, Mosquito, Anson,Warwick, Spitfire, Walrus, Sea Otter, Hurricane, Fortress, Halifax and Hudson[1, 3]. A further four squadrons were used for photo-reconnaissance, six for air/searescue and six for meteorological operations, representing a further establishment of297 aircraft, of which 112 were available for operations. This gave a totalestablishment of over 1000 aircraft.Immediately after the war, many of the Coastal Command squadrons weredisbanded, including all the Catalina squadrons. The maritime reconnaissance rolewas initially continued with Sunderland V aircraft, the Liberators, and someWarwick Vs [2]. With the ending of the Lend–Lease arrangement in August 1945all airframes delivered under the scheme had to be purchased, scrapped or returned(apart from some Liberators transferred to Transport Command). The MRLiberators were all returned to the USA (or scrapped), which left a large gap inUK capability. To fill this gap, the Lancaster bomber was modified as the LancasterGR.3 and allocated to Coastal Command, first entering squadron service in 1946.The Lancaster GR.3 left front-line service in 1953, although it continued to be usedat the School of Maritime Reconnaissance at St Mawgan until 1957 [2]. TheSunderland would continue in service with the RAF in the Far East until 1959. Planswere also underway to develop a new maritime reconnaissance aircraft, which wouldbecome the Avro Shackleton and which entered service as the Shackleton MR1 in1951. As a further stop-gap, while the deliveries of the Shackleton built up, four UKbased Squadrons were equipped in January 1952 with the Lockheed Neptune MR1.These aircraft were supplied by the USA under the Mutual Defence Aid Pact(MDAP) in connection with the setting up of NATO [2]. These long-range Neptuneswere returned to the US in 1956. The Shackleton MR2 entered service in 1953 andthe MR3 in 1957.In 1969 Coastal Command became part of the new RAF Strike Command and atthe same time the new Nimrod MR1 started to replace the Shackletons. In 1980 theNimrod MR2 entered service and remained in the front line until 2010, when itsreplacement, the BAE Systems Nimrod MRA4, was cancelled and all Nimrods wereretired.1.3 Research, testing and evaluationA number of different research, development and trials organisations are mentionedthroughout the book. A brief summary of their history is given here and furtherdetails of their work will be found in the relevant chapters.1-2

Airborne Maritime Surveillance Radar, Volume 21.3.1 Research and development establishmentsThe first work on airborne radar was undertaken at the Bawdsey Research Station,at Bawdsey Manor in Suffolk, starting in 1936. At the outbreak of war the team atBawdsey Manor, now part of the Air Ministry Research Establishment (AMRE),moved first to Perth and then to RAF St Athan. RAF St Athan was home to 32Maintenance Unit (No. 32 MU), which had been given the task of installing thenewly developed ASV and AI radars into Hudson and Blenheim aircraft, respectively [4]. No. 32 MU were subsequently involved with developing installations ofnew ASV radars in different aircraft throughout WWII.In 1940, AMRE, now the Ministry of Aircraft Production ResearchEstablishment (MAPRE), moved to Worth Matravers, near Swanage in Dorset.The name of this organisation was changed to the Telecommunications ResearchEstablishment (TRE) in November 1940, still part of the Air Ministry. In May 1942TRE moved to Malvern because of the danger of commando raids, fear of Germaninterception of TRE experimental transmissions and vulnerability to bombing onthe south coast of England. In 1953 TRE was merged with the British Army’s RadarResearch and Development Establishment (RRDE) to become the Radar ResearchEstablishment (RRE). In 1957 its name was further changed to the Royal RadarEstablishment, also RRE. In 1976, RRE was merged with the Signals Research andDevelopment Establishment (SRDE) to become the Royal Signals and RadarEstablishment (RSRE).In the spring of 1940, when some of the airborne radar team moved to WorthMatravers, others from the team, including Keith Wood, Robert Hanbury-Brown,Gerald Touch and Roy Hearsum moved to the Royal Aircraft Establishment (RAE)at Farnborough [5]. The RAE were responsible for aircraft research and in 1940 itsRadio Department was tasked with overseeing the engineering and production of1.5 m ASV and AI systems.In 1991, the major research establishments, including RSRE and RAE, werecombined as the Defence Research Agency (DRA), which became the DefenceEvaluation and Research Agency (DERA) in 1995. In 2001, DERA was spilt intothe privatised QinetiQ and the government-owned Defence Science and TechnologyLaboratory (Dstl).1.3.2 Performance assessment and trainingIn the early years of radar, TRE were closely involved not only in the design of theradars but most importantly in assessing radar performance through trials andproviding advice to the RAF on the operation and maintenance of the newequipment. The early radars were difficult to use and maintain and required specialtraining of the operators and maintainers. Tactical operating techniques also neededto be developed. RAF Coastal Command set up a training and evaluation unit, theCoastal Command Development Unit (CCDU) at Carew Cheriton in December1940. This unit was tasked with undertaking trials of new radars and developingtactics for their use. This work was very valuable and CCDU was expanded toundertake service trials of all new Coastal Command aircraft and equipment [2].1-3

Airborne Maritime Surveillance Radar, Volume 2CCDU moved to Ballykelly in November 1941 and then in June 1942 to Tain [2]. InSeptember 1943 CCDU moved to RAF Angle. Finally, in January 1945, the CCDUmoved to Thorney Island and was renamed the Air Sea Warfare Development Unit(ASWDU).After WWII, ASWDU continued to be responsible for testing new equipment tobe used by Coastal Command. In 1948 ASWDU moved from Thorney Island toBallykelly. In 1951 it moved to St Mawgan and then in 1958 back to Ballykelly.ASWDU were active from 1945 to 1969, when the Central Tactical and TrialsOrganisation (CTTO) was set up in RAF Strike Command. CTTO was responsiblefor the trialling of operational modifications and the development of tactics for allRAF operational aircraft.TRE and subsequently RRE and RSRE also continued to play a key role in thedesign and testing of new radars, as will become evident from this book.In January 1947, a Joint Anti-Submarine School (JASS) was set up inLondonderry, Northern Ireland. The role of JASS was to run courses to train RNand RAF crews of ships and aircraft on the broader aspects of anti-submarinewarfare. In the 1950s, JASS had a flight of Shackletons for trials use, but this wasdisbanded in 1957.1.4 WWII ASV radarsSoon after the start of WW II, the UK had in service ASV Mk. I, quickly followedby ASV Mk II. ASV Mk. II radar operated at 176 MHz and its range was up to36 miles, with a minimum range of about one mile. Several thousand sets were builtand installed in many different aircraft of RAF Coastal Command. Following theinitial development of the high power magnetron in 1940, the H2S [6] ‘blindnavigation’ microwave radar was developed, entering service with BomberCommand at the end of 1942. In 1942 there was an urgent requirement to upgradethe performance of ASV radar to detect submarines and for this purpose H2S Mk IIwas put into service as ASV Mk III, first becoming operational in 1943. DuringWWII there were various further evolutions of ASV radars based on H2S, culminatingin ASV Mk VI, all operating on 9 cm wavelength. H2S Mk I and Mk II operated at afrequency of 3 GHz (9 cm wavelength) but H2S Mk III, first operational in December1943, and most subsequent marks operated in X-band (9 GHz, 3 cm wavelength).A prototype 3 cm ASV radar, ASV Mk. VII, was developed but long-range ASVradars based on 3 cm H2S did not enter service with the RAF during WWII becausethe 3 cm H2S production was reserved for the bomber force. This was despite theintroduction in 1944 by the Germans of the schnorkel (often referred to in the UK as asnort), allowing U-boats to charge their batteries whilst submerged. The snort waseffectively undetectable by the 9 cm ASV radars and it was recognised that operationat 3 cm would be most desirable. Various 3 cm ASV systems from the USA were usedby Coastal Command during WWII, including ASV Mk. X (AN/APS-15) onLiberators and ASV Mk. VIIIA (AN/APS-3) on Catalinas. Smaller forward-looking3 cm ASV radars for the Fleet Air Arm and strike aircraft of Coastal Commandwere also developed in the UK, including ASV Mk. XI, also known as ASV.X,1-4

Airborne Maritime Surveillance Radar, Volume 2installed on Farey Swordfish aircraft of the Fleet Air Arm, ASV Mk. XII used onBeaufighters and ASV Mk. XIII. ASV Mk. XIII was developed from ASV Mk. XI,with Mk XIIIA used by FAA and in Mosquito aircraft of Coastal Command and Mk.XIIIB used in Beaufighter and Brigand aircraft of Coastal Command.The deployment of different long-range ASV systems in Coastal Command at theend of WWII was as follows [7]:ASV Mk. Mk.Mk.Mk.Mk.IIIIIIBIIICVIVIAVIBVICVAXVIIIALRASV and SRASV on Halifaxes, Fortresses, Warwicks I, Hudsonsand Sea Otters of meteorological and air/sea rescues squadrons.1 Wellington squadron.Nos. 58 and 502 Halifax MR squadrons.Squadrons with Sunderland Mk. III.3 Wellington squadrons.3 Wellington squadrons.No. 179 Squadron Warwicks.Nos. 228 and 461 Squadrons with Sunderland Mk. V.Nos 220 and 311 Liberator squadrons.All remaining Liberator squadrons.3 Catalina squadrons.1.5 Post-war ASV radar and aircraft developmentsImmediately after the war, as discussed above, the maritime reconnaissance role wasinitially continued by Sunderland Mk. V aircraft with ASV Mk. VIC, theLiberators, with ASV Mk. X, and some Warwick Vs in 179 squadron, with ASVMk. VIB. With the loss of the Liberators, the Lancaster GR.3 was used to fill thegap, from 1946 to 1954. These were fitted with ASV Mk. 7A [8] which was directlydeveloped from the prototype ASV Mk. VII produced in 1944 [9].The Lockheed Neptune MR1 aircraft from USA, in service from 1952 to 1956,were fitted with the US AN/APS-20 radar (see chapter 8). This was a high-power Sband radar, principally designed for long-range detection of air targets (airborneearly warning, AEW). This radar was later used on the AEW versions of theShackleton and the AEW Gannets used by the Royal Navy.A replacement maritime reconnaissance aircraft had been under considerationsince the end of the war and this eventually resulted in the Shackleton MR1 aircraft(figure 1.1) entering squadron service in March 1951. The story of the AvroShackleton development is given in [10]. The Shackleton’s primary roles wereanti-submarine warfare (ASW) and surface surveillance (anti-surface warfare,ASuW). The Shackleton was a development from the Avro Lincoln heavy bomber,itself a development of the Avro Lancaster. The Shackleton MR1, with a nosemounted radar, was soon replaced by the MR2 (figure 1.2), which entered service in1953. The MR2 had several significant changes, including repositioning the radar toa ventral position, aft of the bomb bay, and making the tail wheel retractable.Finally, the MR3 (figure 1.3), with a tricycle undercarriage and improved soundproofing, entered service with the RAF in 1957. The first radar installed in all marks1-5

Airborne Maritime Surveillance Radar, Volume 2Figure 1.1. Shackleton MR1 VP256 [By San Diego Air & Space Museum Archives [No restrictions or Publicdomain], via Wikimedia Commons].Figure 1.2. Shackleton MR2 WR961 [By San Diego Air & Space Museum Archives [No restrictions or Publicdomain], via Wikimedia Commons].Figure 1.3. Shackleton MR3 [By RAF [Public domain], via Wikimedia Commons].1-6

Airborne Maritime Surveillance Radar, Volume 2of Shackleton was ASV Mk. 13 (ARI 5729), described in chapter 3. This was a 3 cmASV radar, originally designed during WWII for FAA aircraft. This radar wasreplaced in 1959 by the ASV Mk. 21 (chapter 4), which was developed by EMIElectronics. ASV 21 was again a 3 cm radar with magnetron transmitter but hadhigher power and was better engineered, with improved reliability and improvedergonomics.At the same time as the ASV Mk. 13, the ASV Mk. 19 was developed for use bythe Royal Navy Fleet Air Arm and was in service from about 1953 until the mid1960s. It was installed in carrier-based aircraft for ASW (anti-submarine warfare)operations and also in shore-based aircraft, used for training radar operators. Twovariants were made, the ASV Mk. 19A (ARI 5834) and the ASV Mk. 19B (ARI5838). The Mk. 19A was installed in the Grumman Avenger AS.4 and the PercivalSea Prince T.1. The Mk. 19B was installed in the Short Seamew AS.1 and the FaireyGannet AS.1 and AS.4 (see chapter 8).In 1964 development started to meet ASR 381, the replacement for theShackleton. This would eventually be the Hawker Siddeley Nimrod MR1, whichentered service in 1969. The Nimrod MR1 was based on the De Havilland Cometairliner, with the first two aircraft using unfinished Comet 4C airframes and with atotal final build of 46 aircraft. Starting in 1975, 35 aircraft were upgraded to the newNimrod MR2 standard, with the MR2 entering service in 1980. The history of theNimrod development until the cancellation in 2010 of its replacement, the NimrodMRA4, and the removal of all MR2s from service is given in [11]. The NimrodMR1, figure 1.4, had the ASV 21D radar (chapter 4), very similar to the ASV 21 onthe Shackletons. It was known from the start that ASV 21D was not well-suited tothe role required of the Nimrod. Following an extensive research programme led byRRE and an industrial competition, the development and manufacture of a modernreplacement radar was won by EMI Electronics (see chapter 5). This radar wasSearchwater (see chapter 6) and entered service in 1980 in the Nimrod MR2, figure 1.5.Figure 1.4. Nimrod MR1 XV250, 201 Squadron, RAF Kinloss [By RuthAS (Own work) [CC BY 3.0(http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons].1-7

Airborne Maritime Surveillance Radar, Volume 2Figure 1.5. Hawker Siddeley Nimrod MR2 [Ref Number: 22-15-16; Photographer: Ian Britton;www.FreeFoto.com].Searchwater was a completely new concept in airborne maritime surveillance radar.It had a wide bandwidth, high-power travelling wave tube (TWT) transmitter,extensive digital and analogue signal processing and computer control.1.6 Summary of bookChapter 2 describes the ASV Mk. 7A radar used on the Lancaster GR.3 aircraft.This radar was a direct descendant of the ASV Mk. VII that was developed in 1944but never entered service. Chapter 3 describes the ASV Mk. 13 radar, with a designalso dating from 1944, including its proving trials in a Warwick V and subsequentservice in the Shackleton. Chapter 4 continues with the ASV 21 in the Shackletonand ASV 21D in the Nimrod MR1. These radars were still using the basic principlesdeveloped during WWII, with magnetron transmitters and long-persistence phosphor displays. The move to a modern radar, with digital signal processing andcomputer control, started with the research led by RRE in support of ASR 846,which is discussed in chapter 5. The resulting radar, Searchwater, is described inchapter 6. Chapter 7 considers the comparative performance of ASV 21 andSearchwater. Chapter 8 returns to the 1950s and gives an overview of ASV Mk.19, a radar used by the FAA and designed and built at the same time as ASV 13, andAN/APS-20, the US radar that was installed on the Neptune MR1 aircraft used bythe RAF from 1952 to 1956. Finally, chapter 9 summarises the developments inASV radar covered by the book and the next generation of radar that would havebeen used in the Nimrod MRA4.The descriptions of the various radars and their operational performance aretaken mainly from documents held by The National Archives. These documents aretypically Air Ministry handbooks and trials reports issued by ASWDU, CTTO,JASS, TRE and RRE. In addition, use has been made of material relating to ASV 21and Searchwater provided by EMI Electronics (now Thales UK).1-8

Airborne Maritime Surveillance Radar, Volume 2References[1] Watts S 2018 Airborne Maritime Surveillance Radar, Vol. 1 British ASV Radars in WWII1939-1945 (San Rafael, CA: Morgan and Claypool)[2] Ashworth C 1992 RAF Coastal Command 1936—1969 (UK: Patrick Stevens)[3] Hendrie A 2010 The Cinderella Service, RAF Coastal Command 1939—1945 (England: Penand Sword Aviation)[4] Clements J 2001 Electronic Airborne Goldfish (UK: Paterchurch Publications)[5] Wood K 2004 Echoes and Reflections (Serendipity)[6] Lovell B 1991 Echoes of War; The Story of H2S Radar (London: Taylor and Francis)[7] The Second World War 1939-1945—Royal Air Force, Signals Volume VI—Radar inMaritime Warfare, Air Ministry, 1954 (TNA AIR 10/5555)[8] ASV Mk. 7A, ARI. 5753, Air Publication 2894G, Vol. 1, 2nd Edition, Air Ministry, 19461949 (TNA AIR 10/4949)[9] Performance of A.S.V. Mk. VII (X band) in Wellington XIV Aircraft, C.C.D.U. TrialReport No. 44/36, 15th August 1944, (TNA AIR 65/123)[10] Ashworth C 1990 Avro’s Maritime Heavyweight: The Shackleton (Aston PublicationsLimited)[11] Gibson C 2015 Nimrod’s Genesis, RAF Maritime Patrol Projects and Weapons Since 1945(Manchester: Hikoki Publications)1-9

1.5 m ASV and AI systems. In 1991, the major research establishments, including RSRE and RAE, were combined as the Defence Research Agency (DRA), which became the Defence Evaluation and Research Agency (DERA) in 1995. In 2001, DERA was spilt into the privatised QinetiQ and the government-owned Defence

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