S-2: 4 units (Schnellboot 1931)
137-573: An airborne early warning and control ( AEW&C ) system is an airborne radar early warning system designed to detect aircraft , ships , vehicles , missiles and other incoming projectiles at long ranges, as well as performing command and control of the battlespace in aerial engagements by informing and directing friendly fighter and attack aircraft . AEW&C units are also used to carry out aerial surveillance over ground and maritime targets , and frequently perform battle management command and control (BMC2). When used at altitude,
274-415: A 40mm Bofors or, less commonly, a 20mm flakvierling (quadruple mount) for the aft 37mm cannon. The S26 class boats - which provided the bulk of the wartime deliveries - were 34.94 m (114 ft 8 in) long and 5.38 m (17 ft 8 in) in beam . Their diesel engines provided a range of 700 to 750 nmi (810–860 mi; 1,300–1,390 km), substantially greater than
411-470: A fractal surface, such as rocks or soil, and are used by navigation radars. A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the refractive index of air, which is called the radar horizon . Even when the beam is emitted parallel to the ground, the beam rises above the ground as the curvature of the Earth sinks below the horizon. Furthermore,
548-424: A transmitter that emits radio waves known as radar signals in predetermined directions. When these signals contact an object they are usually reflected or scattered in many directions, although some of them will be absorbed and penetrate into the target. Radar signals are reflected especially well by materials of considerable electrical conductivity —such as most metals, seawater , and wet ground. This makes
685-667: A 360 degree coverage, the radar antenna of the Chinese AWACS does not rotate. Instead, three PAR antenna modules are placed in a triangular configuration inside the round radome to provide a 360 degree coverage. The installation of equipment at the Il-76 began in late 2002 aircraft by Xian aircraft industries (Xian Aircraft Industry Co.). The first flight of an airplane KJ-2000 made in November 2003. All four machines will be equipped with this type. The last to be introduced into service
822-492: A Chief Engineer ( Obermaschinist ), three engineer NCOs ( Maschinenmaaten ), six engine-room ratings (usually Heizer ), two radio operators ( Funkgefreiter or Funkgast ) for radio communications including decoding, and a torpedo mechanic ( Torpedomechanikergefreiter ) who doubled as the boat's cook. Crew members could earn an award particular to their work — the Schnellbootkriegsabzeichen — denoted by
959-485: A Russian-made Ilyushin-76 cargo plane [also incorrectly reported as a Beriev A-50 Mainstay] with advanced Elta electronic, computer, radar and communications systems. Beijing was expected to acquire several Phalcon AEW systems, and reportedly could buy at least three more [and possibly up to eight] of these systems, the prototype of which was planned for testing beginning in 2000. In July 2000, the US pressured Israel to back out of
1096-408: A badge depicting an E-boat passing through a wreath. The criteria were good conduct, distinction in action, and participating in at least twelve enemy actions. It was also awarded for particularly successful missions, displays of leadership or being killed in action. It could be awarded under special circumstances, such as when another decoration was not suitable. E-boats were primarily used to patrol
1233-482: A different dielectric constant or diamagnetic constant from the first, the waves will reflect or scatter from the boundary between the materials. This means that a solid object in air or in a vacuum , or a significant change in atomic density between the object and what is surrounding it, will usually scatter radar (radio) waves from its surface. This is particularly true for electrically conductive materials such as metal and carbon fibre, making radar well-suited to
1370-509: A different installation was used to direct Bristol Beaufighters toward Heinkel He 111s , which were air-launching V-1 flying bombs . In February 1944, the US Navy ordered the development of a radar system that could be carried aloft in an aircraft under Project Cadillac. A prototype system was built and flown in August on a modified TBM Avenger torpedo bomber . Tests were successful, with
1507-540: A full radar system, that he called a telemobiloscope . It operated on a 50 cm wavelength and the pulsed radar signal was created via a spark-gap. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in Cologne and Rotterdam harbour but was rejected. In 1915, Robert Watson-Watt used radio technology to provide advance warning of thunderstorms to airmen and during
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#17327794802761644-476: A major advance in capability, being the first AEW to use a pulse-Doppler radar , which allowed it to track targets normally lost in ground clutter. Previously, low-flying aircraft could only be readily tracked over water. The AWACS features a three-dimensional radar that measures azimuth, range, and elevation simultaneously; the unit installed upon the E-767 has superior surveillance capability over water compared to
1781-494: A major asset in an AEW aircraft. Following a crash, the US Navy opted to discontinue lighter than air operations in 1962. In 1958, the Soviet Tupolev Design Bureau was ordered to design an AEW aircraft. After determining that the projected radar instrumentation would not fit in a Tupolev Tu-95 or a Tupolev Tu-116 , the decision was made to use the more capacious Tupolev Tu-114 instead. This solved
1918-610: A maximum range of over 850 km at 9,000 metres (30,000 ft) altitude. The Swedish Air Force uses the S 100D Argus ASC890 as its AEW platform. The S 100D Argus is based on the Saab 340 with an Ericsson Erieye PS-890 radar. Saab also offers the Bombardier Global 6000 -based GlobalEye . In early 2006, the Pakistan Air Force ordered six Erieye AEW equipped Saab 2000s from Sweden. In December 2006,
2055-630: A museum-ship at the Richmond dry docks in Bideford, Devon . The Schnellboot design evolved over time. The first groups had a pair of torpedo tubes fitted on the foredeck, but from S26 onwards the forecastle had been raised so that the torpedo tubes were built into the structure. The first post-WW1 torpedo boat was ordered in November 1929 to be built by Lürssen at Vegesack , near Bremen , in 1930 as their Yard No. 12120, using mahogany and light metal composite. Originally numbered as UZ(S)16 , it
2192-626: A number of smaller craft such as fishing boats. They also damaged two cruisers, five destroyers, three landing ships, one repair ship, one naval tug, and numerous other merchant vessels. Sea mines laid by the E-boats sank 37 merchant ships totalling 148,535 tons, a destroyer, two minesweepers, and four landing ships. E-boat crews were awarded 23 Knight's Cross of the Iron Crosses and 112 German Crosses in Gold. To boost Axis naval strength in
2329-775: A patrol boat in the Bundesmarine and became commander-in-chief of the fleet before his retirement in 1978. In 1947, the Danish navy bought twelve former Kriegsmarine boats. These were further augmented in 1951 by six units bought from the Royal Norwegian Navy. The last unit, the P568 Viben , was retired in 1965. After World War II, the Norwegian Navy received a number of former Kriegsmarine boats. Six boats were transferred to Denmark in 1951. There
2466-749: A physics instructor at the Imperial Russian Navy school in Kronstadt , developed an apparatus using a coherer tube for detecting distant lightning strikes. The next year, he added a spark-gap transmitter . In 1897, while testing this equipment for communicating between two ships in the Baltic Sea , he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation. The German inventor Christian Hülsmeyer
2603-498: A proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time. Similarly, in the UK, L. S. Alder took out a secret provisional patent for Naval radar in 1928. W.A.S. Butement and P. E. Pollard developed a breadboard test unit, operating at 50 cm (600 MHz) and using pulsed modulation which gave successful laboratory results. In January 1931,
2740-483: A pseudorandom set of frequencies and also have very short scanning rates, which makes them difficult to detect and jam. Up to 1000 targets can be tracked simultaneously to a range of 243 mi (450 km), while at the same time, multitudes of air-to-air interceptions or air-to-surface (including maritime) attacks can be guided simultaneously. The radar equipment of the Israeli AEW&;C consists of each L-band radar on
2877-732: A pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American Robert M. Page , working at the Naval Research Laboratory . The following year, the United States Army successfully tested a primitive surface-to-surface radar to aim coastal battery searchlights at night. This design was followed by a pulsed system demonstrated in May 1935 by Rudolf Kühnhold and
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#17327794802763014-565: A radius of 265 nmiles @ 33 knots. Each carried two 550mm torpedo tubes, a 40mm gun and 16 men. Kajmakcalan and Durmitor escaped to Alexandria in April 1941 to join the Allies; the other six fell into Italian hands and became Ms41 to Ms46 , four of them eventually captured by the Germans and refitted with standard 533 mm torpedoes (see below under " S2 class"). The poor seaworthiness of
3151-442: A rescue. For similar reasons, objects intended to avoid detection will not have inside corners or surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft . These precautions do not totally eliminate reflection because of diffraction , especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff , are very reflective but do not direct
3288-673: A speed of 33.8 knots. Armament and men as in S1 . They formed a "Half Flotilla" and were used for training crews for later E-boats; all were stricken on 10 December 1936 (along with S1 ) for transfer to Spain. The numbers S2 to S5 were re-used in 1943. Eight petrol-engined boats similar to the original S2 class had been ordered from Lürssen, Vegesack, and completed in 1937-39 for that navy as Orjen , Durmitor , Suvobor , Kajmakcalan , Velebit , Dinaira , Rudnik and Triglav . When Italy occupied Yugoslavia in April 1941, two of them ( Durmitor and Kajmakcalan ) escaped to Alexandria and served with
3425-667: A substantial AEW capability, initially with American Douglas AD-4W Skyraiders , designated Skyraider AEW.1, which in turn were replaced by the Fairey Gannet AEW.3 , using the same AN/APS-20 radar. With the retirement of conventional aircraft carriers, the Gannet was withdrawn and the Royal Air Force (RAF) installed the radars from the Gannets on Avro Shackleton MR.2 airframes, redesignated Shackleton AEW.2. To replace
3562-419: A sustained speed of 34.2 knots (maximum 39.8 knots). It carried two 500mm (19.685 inch) torpedo tubes and one 20mm flak gun. It had a complement of 12 (later 18) men. Along with the next five boats ( S2 to S6 ), it was stricken on 10 December 1936 and sold to Spain as Badajoz (renamed LT15 in 1939). The number S1 was re-used in 1939. Five boats had been ordered by Bulgaria from Lürssen, Vegesack, of which
3699-677: A system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the Daventry Experiment of 26 February 1935, using a powerful BBC shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected, Hugh Dowding , the Air Member for Supply and Research , was very impressed with their system's potential and funds were immediately provided for further operational development. Watson-Watt's team patented
3836-674: A test boat under the name EF 3. S130 was on display in Wilhelmshaven , Germany, having formerly been used as a houseboat. S130 was purchased and towed from Wilhelmshaven to the Husbands Shipyard, Marchwood, Southampton , England in January 2003, under the auspices of the British Military Powerboat Trust. In 2004, S130 was taken to the slipway at Hythe, where, under the supervision of
3973-514: A wide region and direct fighter aircraft towards targets. Marine radars are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour, vessel traffic service radar systems are used to monitor and regulate ship movements in busy waters. Meteorologists use radar to monitor precipitation and wind. It has become
4110-907: A writeup on the apparatus was entered in the Inventions Book maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that was used in coastal defence and was incorporated into Chain Home as Chain Home (low) . Before the Second World War , researchers in the United Kingdom, France , Germany , Italy , Japan , the Netherlands , the Soviet Union , and
4247-452: Is a simplification for transmission in a vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects are also considered. Frequency shift is caused by motion that changes the number of wavelengths between the reflector and the radar. This can degrade or enhance radar performance depending upon how it affects
Airborne early warning and control - Misplaced Pages Continue
4384-436: Is a system that uses radio waves to determine the distance ( ranging ), direction ( azimuth and elevation angles ), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft , ships , spacecraft , guided missiles , motor vehicles , map weather formations , and terrain . A radar system consists of a transmitter producing electromagnetic waves in
4521-451: Is as follows, where F D {\displaystyle F_{D}} is Doppler frequency, F T {\displaystyle F_{T}} is transmit frequency, V R {\displaystyle V_{R}} is radial velocity, and C {\displaystyle C} is the speed of light: Passive radar is applicable to electronic countermeasures and radio astronomy as follows: Only
4658-525: Is considered to be both more capable and less expensive to operate than the older Boeing 707-based Phalcon fleet. In 2017, India announced plans to purchase six airborne early warning and control (AEW&C) ("AWACS") aircraft that can also perform aerial refuelling, with the first two AEW&C aircraft awaiting approval by Cabinet in 2020. However, in September 2021, it was decided to use six Airbus A321s acquired from Air India instead. On 3 June 1957,
4795-488: Is currently in service with Israel, Italy, and Singapore. Instead of using a rotodome, a moving radar was found on some AEW&C aircraft, and the EL/W-2085 used an active electronically scanned array (AESA) – an active phased array radar. This radar consists of an array of transmit/receive (T/R) modules that allow a beam to be electronically steered, making a physically rotating rotodome unnecessary. AESA radars operate on
4932-567: Is intended. Radar relies on its own transmissions rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the target objects themselves, such as infrared radiation (heat). This process of directing artificial radio waves towards objects is called illumination , although radio waves are invisible to the human eye as well as optical cameras. If electromagnetic waves travelling through one material meet another material, having
5069-687: Is just one surviving E-boat, identified as S130 . It was built as hull No. 1030 at the Schlichting boatyard in Travemünde . S130 was commissioned on 21 October 1943 and took an active part in the war, participating in the Exercise Tiger attack and attacks on the D-Day invasion fleet. According to Dutch military historian Maurice Laarman: In 1945, S130 was taken as a British war prize (FPB 5030) and put to use in covert operations. Under
5206-417: Is the range. This yields: This shows that the received power declines as the fourth power of the range, which means that the received power from distant targets is relatively very small. Additional filtering and pulse integration modifies the radar equation slightly for pulse-Doppler radar performance , which can be used to increase detection range and reduce transmit power. The equation above with F = 1
5343-609: The Kriegsmarine in 1939. The E-boats had MB502 diesels and were shorter (by 2.18m) than the standard S26 design of boats. They were re-numbered as S30 to S37 , while the Qi Jiguang was renamed Tanga . Germany sold four E-boats to Romania on 14 August 1944. These vessels displaced 65 tons, had a top speed of 30 knots generated by three Mercedes-Benz engines totalling 2,130 kW (2,850 hp) and were armed with two 500 mm (19.685 in) torpedo tubes. Each of
5480-523: The 9th flotilla were the first naval units to respond to the invasion fleet of Operation Overlord . They left Cherbourg harbour at 5 a.m. on 6 June 1944. On finding themselves confronted by the entire invasion fleet, they fired their torpedoes at maximum range and returned to Cherbourg. During World War II, E-boats claimed 101 merchant ships totalling 214,728 tons. Additional claims include 12 destroyers, 11 minesweepers, eight landing ships, six MTBs, one torpedo boat, one minelayer, one submarine, and
5617-603: The Baltic Sea and the English Channel in order to intercept shipping heading for the English ports in the south and east. As such, they were up against Royal Navy and Commonwealth, e.g., Royal Canadian Navy contingents leading up to D-Day , motor gunboats (MGBs), motor torpedo boats (MTBs), motor launches , frigates and destroyers . They were also transferred in small numbers to the Mediterranean, and
Airborne early warning and control - Misplaced Pages Continue
5754-761: The Indian Air Force (IAF) and Defence Research and Development Organisation (DRDO) began a study of requirements for developing an Airborne Early Warning and Control (AWAC) system. In 2015, DRDO delivered 3 AWACs, called Netra , to the IAF with an advanced Indian AESA radar system fitted on the Brazilian Embraer EMB-145 air frame. Netra gives a 240-degree coverage of airspace. The Emb-145 also has air-to-air refuelling capability for longer surveillance time. The IAF also operates three Israeli EL/W-2090 systems, mounted on Ilyushin Il-76 airframes,
5891-656: The Italian Navy is operated from the aircraft carriers Cavour and Giuseppe Garibaldi . During the 2010s, the Royal Navy opted to replace its Sea Kings with a modular "Crowsnest" system that can be fitted to any of their Merlin HM2 fleet. The Crowsnest system was partially based upon the Sea King ASaC7's equipment; an unsuccessful bid by Lockheed Martin had proposed using a new multi-functional sensor for either
6028-628: The Nyquist frequency , since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring: Or when substituting with F D {\displaystyle F_{D}} : As an example, a Doppler weather radar with a pulse rate of 2 kHz and transmit frequency of 1 GHz can reliably measure weather speed up to at most 150 m/s (340 mph), thus cannot reliably determine radial velocity of aircraft moving 1,000 m/s (2,200 mph). In all electromagnetic radiation ,
6165-526: The Pakistan Navy requested three excess P-3 Orion aircraft to be equipped with Hawkeye 2000 AEW systems. China and Pakistan also signed a memorandum of understanding (MoU) for the joint development of AEW&C systems. The Hellenic Air Force , Brazilian Air Force and Mexican Air Force use the Embraer R-99 with an Ericsson Erieye PS-890 radar, as on the S 100D. Israel has developed
6302-717: The RAF's Pathfinder . The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: to locate air, ground and sea targets. This evolved in the civilian field into applications for aircraft, ships, and automobiles. In aviation , aircraft can be equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft
6439-453: The S100 class), were very seaworthy, heavily armed and capable of sustaining 43.5 knots (80.6 km/h; 50.1 mph), briefly accelerating to 48 knots (89 km/h; 55 mph). These were armed with torpedoes and Flak guns; commonly one 37 mm at the stern, one 20 mm at the bow with a twin mount amidships, plus machine guns. Armament varied and some S26 class boats substituted
6576-698: The Thorn-EMI ARI 5980/3 Searchwater LAST radar attached to the fuselage on a swivel arm and protected by an inflatable dome. The improved Sea King ASaC7 featured the Searchwater 2000AEW radar, which was capable of simultaneously tracking up to 400 targets, instead of an earlier limit of 250 targets. The Spanish Navy fields the SH-3 Sea King in the same role, operated from the LPH Juan Carlos I . The AgustaWestland EH-101A AEW of
6713-487: The Turkish Air Force are deploying Boeing 737 AEW&C aircraft. The Boeing 737 AEW&C has a fixed, active electronically scanned array radar antenna instead of a mechanically-rotating one, and is capable of simultaneous air and sea search, fighter control and area search, with a maximum range of over 600 km (look-up mode). In addition, the radar antenna array is also doubled as an ELINT array, with
6850-583: The United States Navy , the Northrop Grumman E-2 Hawkeye AEW&;C aircraft is assigned to its supercarriers to protect them and augment their onboard command information centers (CICs). The designation "airborne early warning" (AEW) was used for earlier similar aircraft used in the less-demanding radar picket role, such as the Fairey Gannet AEW.3 and Lockheed EC-121 Warning Star , and continues to be used by
6987-479: The Western Approaches . The requirement for good performance in rough seas dictated the use of a round-bottomed displacement hull rather than the flat-bottomed planing hull that was more usual for small, high-speed boats. The shipbuilding company Lürssen at Vegesack , Bremen, overcame many of the disadvantages of such a hull and, with the private motor yacht Oheka II in 1926, produced a craft that
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#17327794802767124-440: The electromagnetic spectrum . One example is lidar , which uses predominantly infrared light from lasers rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents. As early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov ,
7261-592: The gasoline -fueled American PT boats and British motor torpedo boats (MTBs). As a result of early war experience of combat against the fast and powerful S-boats, the Royal Navy created its MGB force and later developed better-matched MTBs, using the Fairmile 'D' hull design. This design was chosen because the theatre of operations of such boats was expected to be the North Sea , English Channel and
7398-460: The radio or microwaves domain, a transmitting antenna , a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds. Radar was developed secretly for military use by several countries in
7535-407: The reflective surfaces . A corner reflector consists of three flat surfaces meeting like the inside corner of a cube. The structure will reflect waves entering its opening directly back to the source. They are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect. Corner reflectors on boats, for example, make them more detectable to avoid collision or during
7672-534: The "new boy" Arnold Frederic Wilkins to conduct an extensive review of available shortwave units. Wilkins would select a General Post Office model after noting its manual's description of a "fading" effect (the common term for interference at the time) when aircraft flew overhead. By placing a transmitter and receiver on opposite sides of the Potomac River in 1922, U.S. Navy researchers A. Hoyt Taylor and Leo C. Young discovered that ships passing through
7809-513: The $ 1 billion agreement to sell China four Phalcon phased-array radar systems. Following the cancelled A-50I/Phalcon deal, China turned to indigenous solutions. The Phalcon radar and other electronic systems were taken off from the unfinished Il-76, and the airframe was handed to China via Russia in 2002. The Chinese AWACS has a unique phased array radar (PAR) carried in a round radome. Unlike the US AWACS aircraft, which rotate their rotodomes to give
7946-413: The 1920s went on to lead the U.K. research establishment to make many advances using radio techniques, including the probing of the ionosphere and the detection of lightning at long distances. Through his lightning experiments, Watson-Watt became an expert on the use of radio direction finding before turning his inquiry to shortwave transmission. Requiring a suitable receiver for such studies, he told
8083-611: The 1930s, the British developed a radar set that could be carried on an aircraft for what they termed "Air Controlled Interception". The intention was to cover the North West approaches where German long range Focke-Wulf Fw 200 Condor aircraft were threatening shipping. A Vickers Wellington bomber (serial R1629) was fitted with a rotating antenna array. It was tested for use against aerial targets and then for possible use against German E boats . Another radar equipped Wellington with
8220-736: The AEW role. The "Mainstay" is based on the Ilyushin Il-76 airframe, with a large non-rotating disk radome on the rear fuselage. These replaced the 12 Tupolev Tu-126 that filled the role previously. The A-50 and A-50U will eventually be replaced by the Beriev A-100 , which features an AESA array in the radome and is based on the updated Il-476. In May 1997, Russia and Israel agreed to jointly fulfill an order from China to develop and deliver an early warning system. China reportedly ordered one Phalcon for $ 250 million, which entailed retrofitting
8357-498: The AN/APY-1 system on the earlier E-3 models. The E-2 Hawkeye was a specially designed AEW aircraft. Upon its entry to service in 1965, it was initially plagued by technical issues, causing a (later reversed) cancellation. Procurement resumed after efforts to improve reliability, such as replacement of the original rotary drum computer used for processing radar information by a Litton L-304 digital computer. In addition to purchases by
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#17327794802768494-600: The AW101 or another aircraft. The Russian-built Kamov Ka-31 is deployed by the Indian Navy on the aircraft carriers INS Vikramaditya and INS Vikrant and also on Talwar -class frigates . The Russian Navy has two Ka-31R variants, at least one of which was deployed on their aircraft carrier Admiral Kuznetsov in 2016. It is fitted with E-801M Oko (Eye) airborne electronic warfare radar that can track 20 targets simultaneously, detecting aircraft up to 150 km (90 mi) away, and surface warships up to 200 km (120 mi) distant. Radar Radar
8631-408: The BMPT, she was prepared and then towed to Mashfords yard in Cremyll , Cornwall, England to await funding for restoration. In 2008, S130 , having been purchased by the Wheatcroft Collection , was set up ashore at Southdown in Cornwall to undergo restoration work involving Roving Commissions Ltd. In July 2020, S130 was still awaiting restoration, with the intention that upon completion it would be
8768-559: The Black Sea by river and land transport. Some small E-boats were built as boats for carrying by auxiliary cruisers. E-boats were organisationally under the command of the Seekriegsleitung or SKL (the naval warfare command, responsible for the planning, execution and direction of naval warfare), and were administratively organised into flotillas, each originally comprising 8 boats. Consequently most orders for new construction were placed in batches of eight boats, or of multiple of eight. The first half-flotilla ( 1st Schnellbootshalbflotille )
8905-421: The Black Sea, the OKW ordered to the region the transfer of six E-boats of the 1st S-flotilla, the last to be released from action in the Baltic Sea before refit. The Romanian port of Constanța , in the Black Sea, was chosen as the S-flotilla's headquarters. Transporting the six boats overland from Germany to Romania was an impressive logistical feat. The superstructure and all weapons were removed, leaving only
9042-444: The Chinese Air Force until the end of 2007. China is also developing a carrier-based AEW&C, Xian KJ-600 via Y-7 derived Xian JZY-01 testbed. The EL/W-2085 is an airborne early warning and control (AEW&C) multi-band radar system developed by Israel Aerospace Industries (IAI) and its subsidiary Elta Systems of Israel. Its primary objective is to provide intelligence to maintain air superiority and conduct surveillance. The system
9179-409: The E-boat in 1931, a lengthened version of the prototype S1 . The first two were ordered from Lürssen on 28 April 1931 and the other two on 16 July 1931. Each measured 27.95 x 4.2 x 1.06 metres (91 ft 8in x 13 ft 9in x 3 ft 6in) and had a displacement of 46.5 tons standard (58 tons full load). Powered by Daimler-Benz petrol engines on three shafts, with a rating of 3,300 bhp, they had
9316-421: The IAI/Elta EL/M-2075 Phalcon system, which uses an AESA ( active electronically scanned array ) in lieu of a rotodome antenna. The system was the first such system to enter service. The original Phalcon was mounted on a Boeing 707 and developed for the Israeli Defense Force and for export. Israel uses IAI EL/W-2085 airborne early warning and control multi-band radar system on Gulfstream G550 ; this platform
9453-426: The Italian-designed MAS boats of World War I and early World War II led its navy to build its own version of E-boats, the CRDA 60 t type, classed MS ( Motosilurante ). The prototype was designed on the pattern of the six German-built E-boats captured from the Yugoslav Navy in 1941. Two of them sank the British light cruiser HMS Manchester in August 1942, the largest warship to be sunk by fast torpedo craft in
9590-728: The RAF for its Sentry AEW1 , while AEW&C (airborne early warning and control) emphasizes the command and control capabilities that may not be present on smaller or simpler radar picket aircraft. AWACS (Airborne Warning and Control System) is the name of the specific system installed in the E-3 and Japanese Boeing E-767 AEW&C airframes, but is often used as a general synonym for AEW&C. Modern AEW&C systems can detect aircraft from up to 400 km (220 nmi) away, well out of range of most surface-to-air missiles. One AEW&C aircraft flying at 9,000 m (30,000 ft) can cover an area of 312,000 km (120,000 sq mi). Three such aircraft in overlapping orbits can cover
9727-443: The S-bands. Historically, UHF radars had resolution and detection issues that made them ineffective for accurate targeting and fire control; Northrop Grumman and Lockheed claim that the APY-9 has solved these shortcomings in the APY-9 using advanced electronic scanning and high digital computing power via space/time adaptive processing. The Russian Aerospace Forces are currently using approximately 3-5 Beriev A-50 and A-50U "Shmel" in
9864-716: The S-flotilla was disbanded after Romania switched sides on the same day. Eight E-boats were built by Lürssen, Vegesack for the Yugoslav Navy from 1936 to 1939. These were named Orjen , Durmitor , Suvobor , Kajmakcalan , Velebit , Dinaira , Rudnik and Triglav . Each measured 28.00 (overall)/27.70 (waterline) x 4.46 x 1.51 m (91 ft 10in/90 ft 10in x 14 ft 4in x 4 ft 11in) and 51 tonnes standard (61.7 tonnes full load). Three Daimler-Benz BF2 petrol engines of 1,100 hp each = 3,300 hp = 33 kts, while they carried 5.8 tonnes of petrrol to give them
10001-704: The Second World War. After the war these boats served with the Italian Navy , some well into the 1970s. The Kriegsmarine supplied the Spanish Francoist Navy with six E-boats ( S1 to S6 ) in December 1936 during the Spanish Civil War , and sold six more ( S73 , S78 , S124 , S125 , S126 and S134 ) to them in 1943 during the Second World War. Another six were built in Spain with some assistance from Lürssen. A motor boat of
10138-762: The Shackleton AEW.2, an AEW variant of the Hawker Siddeley Nimrod , known as the Nimrod AEW3 , was ordered in 1974. After a protracted and problematic development, this was cancelled in 1986, and seven E-3Ds, designated Sentry AEW.1 in RAF service, were purchased instead. Many countries have developed their own AEW&C systems, although the Boeing E-3 Sentry , E-7A and Northrop Grumman E-2 Hawkeye and Gulfstream/IAI EL/W-2085 are
10275-521: The Swedish flag for a dash to Gotland , and there they would wait for orders from Hamburg. The first mission consisted in the landing of Lithuanian agents at Palanga , Lithuania , in May 1949, and the last one took place in April 1955 in Saaremaa , Estonia . During the last two years of the operation, three new German-built motorboats replaced the old E-boats. Klose was later assigned the command of
10412-539: The US Navy, the E-2 Hawkeye has been sold to the armed forces of Egypt , France , Israel , Japan , Singapore and Taiwan . The latest E-2 version is the E-2D Advanced Hawkeye , which features the new AN/APY-9 radar. The APY-9 radar has been speculated to be capable of detecting fighter-sized stealth aircraft, which are typically optimized against high frequencies like Ka, Ku, X, C and parts of
10549-787: The United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, Hungary and Sweden generated its radar technology during the war. In France in 1934, following systematic studies on the split-anode magnetron , the research branch of the Compagnie générale de la télégraphie sans fil (CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on
10686-703: The Wehrmacht's Fremde Heere Ost (Foreign Armies East), used the Royal Navy's E-boats in order to infiltrate its agents into the Baltic states and Poland . Royal Navy Commander Anthony Courtney was struck by the potential capabilities of former E-boat hulls, and John Harvey-Jones of the Naval Intelligence Division was put in charge of the project. He discovered that the Royal Navy still had two E-boats, P5230 and P5208 , and had them sent to Portsmouth, where one of them, P5230 (ex- S130 ),
10823-537: The arrest of Oshchepkov and his subsequent gulag sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar, Gneiss-2 , entered into service in June 1943 on Pe-2 dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944. The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems. Full radar evolved as
10960-479: The beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later, Lawrence A. Hyland at the Naval Research Laboratory (NRL) observed similar fading effects from passing aircraft; this revelation led to a patent application as well as
11097-431: The consequence of lessons learnt by the Royal Navy during the 1982 Falklands War when the lack of AEW coverage for the task force was a major tactical handicap, and rendered them vulnerable to low-level attack. The Sea King was determined to be both more practical and responsive than the proposed alternative of relying on the RAF's land-based Shackleton AEW.2 fleet. The first examples were a pair of Sea King HAS2s that had
11234-598: The converted steamer Nordsea , but from 1934 a series of purpose-built tenders were commissioned - the Tsingtau in 1934, followed by the Tanga (in 1939), Carl Peters and Adolf Lüderitz in 1940, and finally the Herman von Wissmamm and Gustav Nachtigal . E-boats of the 6th & 9th flotillas from Cherbourg attacked Exercise Tiger on 28 April 1944, causing about 749 American Army and Navy casualties. The E-boats of
11371-568: The cover of the British Control Commission's Fishery Protection Service, which was responsible for preventing Soviet navy vessels from interfering with German fishing boats and for destroying stray mines. The home port of the boats was Kiel , and operated under the supervision of Harvey-Jones. Manned by Klose and his crew, they usually departed for the island of Bornholm waving the White Ensign , where they would hoist
11508-408: The detection of aircraft and ships. Radar absorbing material , containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection . This is the radio equivalent of painting something a dark colour so that it cannot be seen by the eye at night. Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of
11645-476: The detection process. As an example, moving target indication can interact with Doppler to produce signal cancellation at certain radial velocities, which degrades performance. Sea-based radar systems, semi-active radar homing , active radar homing , weather radar , military aircraft, and radar astronomy rely on the Doppler effect to enhance performance. This produces information about target velocity during
11782-411: The detection process. This also allows small objects to be detected in an environment containing much larger nearby slow moving objects. Doppler shift depends upon whether the radar configuration is active or passive. Active radar transmits a signal that is reflected back to the receiver. Passive radar depends upon the object sending a signal to the receiver. The Doppler frequency shift for active radar
11919-626: The device in patent GB593017. Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British Air Ministry , Bawdsey Research Station located in Bawdsey Manor , near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called " Chain Home " along the East and South coasts of England in time for
12056-725: The early series, either the Falange or the Requeté , laid two mines off Almería that crippled the British destroyer HMS Hunter on 13 May 1937. The German-built boats were discarded in the 1960s, while some of the Spanish-built ones served until the early 1970s. The Chinese Nationalist Navy had three S7 -class boats during the Second Sino-Japanese War . Yue-22 was destroyed by Japanese planes, Yue-371
12193-538: The electric field is perpendicular to the direction of propagation, and the electric field direction is the polarization of the wave. For a transmitted radar signal, the polarization can be controlled to yield different effects. Radars use horizontal, vertical, linear, and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate
12330-473: The entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies. A key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared
12467-466: The firm GEMA [ de ] in Germany and then another in June 1935 by an Air Ministry team led by Robert Watson-Watt in Great Britain. In 1935, Watson-Watt was asked to judge recent reports of a German radio-based death ray and turned the request over to Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such
12604-581: The first four were delivered as F1 to F4 . The fifth boat was retained in Germany and given the number S1 . These were petrol-engined boats, similar to the S2 class built for the Kriegsmarine. Although commissioned in 1939, its petrol engines gave frequent problems, and on 10 September 1940 its stern was rammed (by S13 ) in Vlissingen, and was later removed from active service. The first production of
12741-592: The first of 2 HR2S-1W, a derivative of the Sikorsky CH-37 Mojave , was delivered to the US Navy, it used the AN/APS-32 but proved unreliable due to vibration. The British Sea King ASaC7 naval helicopter was operated from both the Invincible -class aircraft carriers and later the helicopter carrier HMS Ocean . The creation of Sea King ASaC7, and earlier AEW.2 and AEW.5 models, came as
12878-711: The first of which first arrived on 25 May 2009. The DRDO proposed a more advanced AWACS with a longer range and with a 360-degree coverage akin to the Phalcon system, based on the Airbus A330 airframe, but given the costs involved there is also the possibility of converting used A320 airliners as well. IAF has plans to develop 6 more Netra AEW&CS based on Embraer EMB-145 platform and another 6 based on Airbus A321 platform. These systems are expected to have an enhanced performance including range and azimuth The Royal Australian Air Force , Republic of Korea Air Force and
13015-550: The four boats had a crew of 25. They were numbered 10 to 13 (formerly S151 , S152 , S153 and S154 ) and served in the Romanian Navy until at least 1954. At the end of the war about 34 E-boats were surrendered to the British. Three boats, S130 (renamed P5230 ), S208 ( P5208 ) and S212 ( P5212 ) were retained for trials. The Gehlen Organization , an intelligence agency established by American occupation authorities in Germany in 1946 and manned by former members of
13152-567: The guise of the "British Baltic Fishery Protection Service", the British Secret Intelligence Service MI-6 ferried spies and agents into Eastern Europe. Beginning in May 1949, MI-6 used S208 , (Kommandant Hans-Helmut Klose) to insert agents into Lithuania, Latvia, Estonia, and Poland. The operations were very successful and continued under a more permanent organisation based in Hamburg. In 1952, S130 joined
13289-648: The hull. After a long road journey of 60 hours, the boats arrived at Ingolstadt , where they were transferred back to water and towed towards Linz . Upon reaching the Austrian city, the superstructure was rebuilt, then the journey continued down the Danube to Galați , where the main engines were installed. The E-boats then continued on their own power towards Constanța , where refitting was completed. The first two boats, S26 and S28 , arrived in Constanța on 24 May 1942,
13426-479: The left and right sides of the fuselage and each S-band antenna in the nose and tail. The phased array allows aircraft positions on operator screens to be updated every 2–4 seconds rather than every 10 seconds, as is the case on the rotodome AWACS. ELTA was the first company to introduce an Active Electronically Scanned Array Airborne (AESA) Early Warning Aircraft and implement advanced mission aircraft using efficient, high-performance business jet platforms. In 2003,
13563-467: The main rudder could be angled outboard to 30 degrees, creating at high speed what is known as the Lürssen Effect . This drew in an "air pocket slightly behind the three propellers, increasing their efficiency, reducing the stern wave and keeping the boat at a nearly horizontal attitude". This was an important innovation as the horizontal attitude lifted the stern, allowing even greater speed, and
13700-446: The manning had increased to 18 men. The S26 class required a complement of between 21 and 24 men, and this remained generally constant for all subsequent boats (except the ex-Italian and KS and LS boats). This comprised a commanding officer (usually an Oberleutnant zur See ), a Chief Boatswain ( Oberbootsmann ), a Helmsman ( Matrosen-Gefreiter ), about six seamen including those operating semaphore and engine telegraph posts ( Matrosen ),
13837-608: The most common systems worldwide. Boeing produces a specific system with a " rotodome " rotating radome that incorporates Westinghouse (now Northrop Grumman ) radar. It is mounted on either the E-3 Sentry aircraft ( Boeing 707 ) or more recently the Boeing E-767 ( Boeing 767 ), the latter only being used by the Japan Air Self-Defense Force . When AWACS first entered service it represented
13974-415: The mouth of the Danube, where S42 was fitted with a new propeller. They were joined by S72 in early August, the rest of the boats remaining in Constanța. On 19 August, S26 , S40 and S72 were destroyed in port by a Soviet air attack. On 22 August S148 hit a mine and sank near Sulina, and on the following day, S42 , S52 and S131 were destroyed in Constanța by a Soviet air attack. What remained of
14111-655: The newly commissioned S49 operational. On 1 January 1944, the 1st S-flotilla numbered six operational boats: S26 , S42 , S47 , S49 , S52 and S79 , while S28 , S40 , S45 and S51 were all out of commission, undergoing repair in Constanța. Three more boats were shipped down the Danube and were being reconstructed at Constanța. On 1 June 1944, 8 boats were operational in Constanța: S28 , S40 , S47 , S49 , S72 , S131 , S148 and S149 . The boats were however penned in harbor, due to fuel shortage. During July, S26 , S28 , S40 and S42 were transferred to Sulina at
14248-508: The ocean liner Normandie in 1935. During the same period, Soviet military engineer P.K. Oshchepkov , in collaboration with the Leningrad Electrotechnical Institute , produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3 km of a receiver. The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following
14385-549: The operation and the mission was enlarged to include signal intelligence (SIGINT) equipment. In 1954/55, S130 and S208 were replaced by a new generation of German S-boote. S130 was returned to the newly formed Bundesmarine in March 1957, and operated under the number UW 10 . Serving initially in the Unterwasserwaffenschule training sailors in underwater weaponry such as mines and torpedoes, she later became
14522-531: The outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the Battle of Britain ; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the " Dowding system " for collecting reports of enemy aircraft and coordinating
14659-1302: The period before and during World War II . A key development was the cavity magnetron in the United Kingdom , which allowed the creation of relatively small systems with sub-meter resolution. The term RADAR was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term radar has since entered English and other languages as an anacronym , a common noun, losing all capitalization . The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy , air-defense systems , anti-missile systems , marine radars to locate landmarks and other ships, aircraft anti-collision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, radar remote sensing , altimetry and flight control systems , guided missile target locating systems, self-driving cars , and ground-penetrating radar for geological observations. Modern high tech radar systems use digital signal processing and machine learning and are capable of extracting useful information from very high noise levels. Other systems which are similar to radar make use of other parts of
14796-706: The primary tool for short-term weather forecasting and watching for severe weather such as thunderstorms , tornadoes , winter storms , precipitation types, etc. Geologists use specialized ground-penetrating radars to map the composition of Earth's crust . Police forces use radar guns to monitor vehicle speeds on the roads. Automotive radars are used for adaptive cruise control and emergency breaking on vehicles by ignoring stationary roadside objects that could cause incorrect brake application and instead measuring moving objects to prevent collision with other vehicles. As part of Intelligent Transport Systems , fixed-position stopped vehicle detection (SVD) radars are mounted on
14933-651: The problems with cooling and operator space that existed with the narrower Tu-95 and Tu-116 fuselage. To meet range requirements, production examples were fitted with an air-to-air refueling probe. The resulting system, the Tupolev Tu-126 , entered service in 1965 with the Soviet Air Forces and remained in service until replaced by the Beriev A-50 in 1984. During the Cold war, United Kingdom deployed
15070-538: The radar system on AEW&C aircraft allows the operators to detect, track and prioritize targets and identify friendly aircraft from hostile ones in real-time and from much farther away than ground-based radars. Like ground-based radars, AEW&C systems can be detected and targeted by opposing forces, but due to aircraft mobility and extended sensor range, they are much less vulnerable to counter-attacks than ground systems. AEW&C aircraft are used for both defensive and offensive air operations, and serve air forces in
15207-432: The radial component of the velocity is relevant. When the reflector is moving at right angle to the radar beam, it has no relative velocity. Objects moving parallel to the radar beam produce the maximum Doppler frequency shift. When the transmit frequency ( F T {\displaystyle F_{T}} ) is pulsed, using a pulse repeat frequency of F R {\displaystyle F_{R}} ,
15344-457: The reduced stern wave made E-boats harder to see, especially at night. The rounded wood planking hull helped reduce weight, and flattened at the stern area, the aft section area was reduced at high speeds, it allowed more hydrodynamic lift. The internal layout of the E-boat remained the same for all types. Its length was generally divided by eight transverse bulkheads (made of 4mm steel below
15481-414: The response. Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland. Even by standards of the era, CH was crude; instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting
15618-410: The resulting frequency spectrum will contain harmonic frequencies above and below F T {\displaystyle F_{T}} with a distance of F R {\displaystyle F_{R}} . As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of F R {\displaystyle F_{R}} , called
15755-427: The roadside to detect stranded vehicles, obstructions and debris by inverting the automotive radar approach and ignoring moving objects. Smaller radar systems are used to detect human movement . Examples are breathing pattern detection for sleep monitoring and hand and finger gesture detection for computer interaction. Automatic door opening, light activation and intruder sensing are also common. A radar system has
15892-560: The same radar. The Lockheed WV and EC-121 Warning Star , which first flew in 1949, served widely with US Air Force and US Navy. It provided the main AEW coverage for US forces during the Vietnam war. It remained operational until replaced with the E-3 AWACS. Developed roughly in parallel, N-class blimps were also used as AEW aircraft, filling gaps in radar coverage for the continental US, their tremendous endurance of over 200 hours being
16029-410: The same role as what the combat information center is to naval warships , in addition to being a highly mobile and powerful radar platform. So useful and advantageous is it to have such aircraft operating at a high altitude, that some navies also operate AEW&C aircraft for their warships at sea, either coastal- or carrier-based and on both fixed-wing and rotary-wing platforms. In the case of
16166-407: The scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross-section . The power P r returning to the receiving antenna is given by the equation: where In the common case where the transmitter and the receiver are at the same location, R t = R r and the term R t ² R r ² can be replaced by R , where R
16303-529: The second pair, S72 and S102 on 3 June, and the final pair, S27 and S40 10 days later. After the sinking of S27 by a malfunctioning torpedo, four more reserve boats, S47 , S49 , S51 and S-52 were dispatched to the Black Sea , in order to replace boats undergoing maintenance. S28 , S72 and S102 were soon relegated to the Constanța Shipyard for engine replacement, leaving only S26 and
16440-407: The signal is attenuated by the medium the beam crosses, and the beam disperses. The maximum range of conventional radar can be limited by a number of factors: E boat S-7: 7 units (Schnellboot 1933) S-14: 4 units (Schnellboot 1934) S-18: 8 units (Schnellboot 1937) S-26: 4 units S-30: 16 units (Schnellboot 1939) S-38: 58 units (Schnellboot 1939/40) S-38b: S-100: 81 units E-boat
16577-664: The system being able to detect low flying formations at a range greater than 100 miles (160 km). US Navy then ordered production of the TBM-3W, the first production AEW aircraft to enter service. TBM-3Ws fitted with the AN/APS-20 radar entered service in March 1945, with 27 eventually constructed. It was also recognised that a larger land-based aircraft would be attractive, thus, under the Cadillac II program, multiple Boeing B-17G Flying Fortress bombers were also outfitted with
16714-491: The target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror . If the wavelength is much longer than the size of the target, the target may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by Rayleigh scattering , an effect that creates Earth's blue sky and red sunsets. When
16851-475: The technology with the U.S. during the 1940 Tizard Mission . In April 1940, Popular Science showed an example of a radar unit using the Watson-Watt patent in an article on air defence. Also, in late 1941 Popular Mechanics had an article in which a U.S. scientist speculated about the British early warning system on the English east coast and came close to what it was and how it worked. Watson-Watt
16988-879: The transmitter. The reflected radar signals captured by the receiving antenna are usually very weak. They can be strengthened by electronic amplifiers . More sophisticated methods of signal processing are also used in order to recover useful radar signals. The weak absorption of radio waves by the medium through which they pass is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as visible light , infrared light , and ultraviolet light , are too strongly attenuated. Weather phenomena, such as fog, clouds, rain, falling snow, and sleet, that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapour, raindrops, or atmospheric gases (especially oxygen) are avoided when designing radars, except when their detection
17125-487: The two length scales are comparable, there may be resonances . Early radars used very long wavelengths that were larger than the targets and thus received a vague signal, whereas many modern systems use shorter wavelengths (a few centimetres or less) that can image objects as small as a loaf of bread. Short radio waves reflect from curves and corners in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between
17262-472: The use of radar altimeters possible in certain cases. The radar signals that are reflected back towards the radar receiver are the desirable ones that make radar detection work. If the object is moving either toward or away from the transmitter, there will be a slight change in the frequency of the radio waves due to the Doppler effect . Radar receivers are usually, but not always, in the same location as
17399-452: The waterline and slightly thinner light metal alloy above) into nine watertight compartments. From bow to stern, these were: Note that the earliest (shorter) boats lacked the first transverse bulkhead, and thus the senior ratings' accommodation was included in the first watertight compartment. The earliest six boats had a crew of 12 men, but by the time of the S7 and S14 types ( S7 to S25 )
17536-516: The whole of Central Europe . AEW&C system indicates close and far proximity range on threats and targets, help extend the range of their sensors, and make offensive aircraft harder to track by avoiding the need for them to keep their own radar active, which the enemy can detect. Systems also communicate with friendly aircraft, vectoring fighters towards hostile aircraft or any unidentified flying object. After having developed Chain Home —the first ground-based early-warning radar detection system—in
17673-608: Was a 1938 Bell Lab unit on some United Air Lines aircraft. Aircraft can land in fog at airports equipped with radar-assisted ground-controlled approach systems in which the plane's position is observed on precision approach radar screens by operators who thereby give radio landing instructions to the pilot, maintaining the aircraft on a defined approach path to the runway. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized military aircraft carry powerful airborne radars to observe air traffic over
17810-465: Was commissioned into the Reichmarine on 7 August 1930. It was renamed W1 on 31 March 1931, and then as S1 on 16 March 1932. It measured 26.8 x 4.2 x 1.06 metres (87 ft x 13 ft 9in x 3 ft 6in) and had a displacement of 39 tons standard (50 tons full load). Powered by three Daimler-Benz BF2 12-cylinder 900 hp petrol engines on three shafts, with a rating of 2,700 bhp, it had
17947-502: Was fast, strong and seaworthy. It was also very light, being constructed of wooden planking over alloy frames. This attracted the interest of the Reichsmarine , which in November 1929 ordered a similar boat but fitted with two torpedo tubes. This became the S1 , and was the basis for all subsequent E-boats. After experimenting with the S1 , the Germans made several improvements to the design. Small rudders added on either side of
18084-463: Was formed in July 1932, but was reorganised as 1st Schnellbootsflotille in June 1935. A second flotilla was established in August 1938, and a third in 1940. Eventually there were fourteen operational flotillas, numbered 1st to 11th plus 21st, 22nd and 24th, together with three training flotillas ( Schnellbootsschulflotille ). Each flotilla required the backup of a depot ship; initially this was provided by
18221-574: Was modified to reduce its weight and increase its power with the installation of two Napier Deltic engines of 1,900 kW (2,500 hp) each. Lieutenant-Commander Hans-Helmut Klose [ de ] was assigned to command a German crew, recruited by the British MI6 and funded by the American Office of Policy Coordination . The missions were assigned the codename " Operation Jungle ". The boats carried out their missions under
18358-748: Was sent to the U.S. in 1941 to advise on air defense after Japan's attack on Pearl Harbor . Alfred Lee Loomis organized the secret MIT Radiation Laboratory at Massachusetts Institute of Technology , Cambridge, Massachusetts which developed microwave radar technology in the years 1941–45. Later, in 1943, Page greatly improved radar with the monopulse technique that was used for many years in most radar applications. The war precipitated research to find better resolution, more portability, and more features for radar, including small, lightweight sets to equip night fighters ( aircraft interception radar ) and maritime patrol aircraft ( air-to-surface-vessel radar ), and complementary navigation systems like Oboe used by
18495-694: Was sunk by its sailors to avoid being captured by the Japanese soldiers and Yue-253 was captured by the People's Liberation Army during the Chinese Civil War . Yue-253 was renamed "Hoiking" (海鯨), meaning "Seawhale" in Chinese . The People's Liberation Army Navy used it as a patrol boat until 1963. The Chinese Nationalist government also ordered eight E-boats and a tender , Qi Jiguang (戚繼光). These were all taken over while under construction by
18632-566: Was the Western Allies ' designation for the fast attack craft (German: Schnellboot , or S-Boot , meaning "fast boat"; plural Schnellboote ) of the Kriegsmarine during World War II ; E-boat could refer to a patrol craft from an armed motorboat to a large Torpedoboot. The name of E-boats was a British designation using the letter E for Enemy . The main wartime production boats, from S26 onwards (but often designated
18769-411: Was the first to use radio waves to detect "the presence of distant metallic objects". In 1904, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter. He obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also obtained a British patent on 23 September 1904 for
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