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98-475: The AN/APG-79 is a type of active electronically scanned array (AESA) radar that was developed for use on the United States Navy 's Boeing F/A-18E/F Super Hornet and Boeing EA-18G Growler aircraft. The radar's AESA technology provides quick updates on multiple targets, and its solid-state antenna construction makes it more reliable and cost-effective than traditional radar systems. The radar has

196-934: A League of Nations Mandate , whereupon it was referred to as Kwezerin-kanshō ( クェゼリン環礁 ) in Japan, part of the Nan'yō gunto . The islands of the Kwajalein Atoll, especially the main island, served as a rural copra -trading outpost administered by Japanese civilians until the beginning of World War II in the Pacific in December 1941. Before the Pacific War , Japanese settlement in Kwajalein Atoll consisted mostly of traders and their families who worked at local branches of shops headquartered at nearby Jaluit Atoll. There were also local administrative staff at Kwajalein. With

294-401: A base for SpaceX for their Falcon 1 rocket. Kwajalein is the 14th largest coral atoll as measured by area of enclosed water. Comprising 97 islands and islets, it has a land area of 16.4 km (6.3 sq mi) and surrounds one of the largest lagoons in the world, with an area of 2,174 km (839 sq mi). The average height above sea level for all the islands

392-524: A chain of inhabited islands about 10 km (6.2 mi) long. Connected islands include Loi, Shell, and Gugeegue. Ebadon ( Epatōn , [ɛbʲɑdˠʌnʲ] ) is located at the westernmost tip of the atoll. It was the second-largest island in the atoll before the formation of Roi-Namur. Like Ebeye, it falls fully under the jurisdiction of the Republic of the Marshall Islands and is not part of

490-626: A hybrid approach, the benefits of AESA (e.g., multiple independent beams) can be realized at a lower cost compared to pure AESA. Bell Labs proposed replacing the Nike Zeus radars with a phased array system in 1960, and was given the go-ahead for development in June 1961. The result was the Zeus Multi-function Array Radar (ZMAR), an early example of an active electronically steered array radar system. ZMAR became MAR when

588-497: A much simpler radar whose primary purpose was to track the outgoing Sprint missiles before they became visible to the potentially distant MAR. These smaller Missile Site Radars (MSR) were passively scanned, forming only a single beam instead of the MAR's multiple beams. While MAR was ultimately successful, the cost of the system was enormous. When the ABM problem became so complex that even

686-441: A much wider range of frequencies, to the point of changing operating frequency with every pulse sent out. Shrinking the entire assembly (the transmitter, receiver and antenna) into a single "transmitter-receiver module" (TRM) about the size of a carton of milk and arraying these elements produces an AESA. The primary advantage of an AESA over a PESA is the capability of the different modules to operate on different frequencies. Unlike

784-420: A narrow range of frequencies to high power levels. To scan a portion of the sky, the radar antenna must be physically moved to point in different directions. Starting in the 1960s new solid-state devices capable of delaying the transmitter signal in a controlled way were introduced. That led to the first practical large-scale passive electronically scanned array (PESA), or simply phased array radar. PESAs took

882-634: A naval base on Kwajalein Island since World War II . It was the final resting place of the German cruiser Prinz Eugen after it survived the Operation Crossroads nuclear test in 1946. In the late 1950s, the US Army took over the base as part of their Nike Zeus anti-ballistic missile efforts, and since then the atoll has been widely used for missile tests of all sorts. Today it is part of

980-718: A range of up to 150 km (80 nm) and can track multiple targets simultaneously. It is capable of firing weapons such as the AIM-120 AMRAAM 's D model and guiding multiple missiles to targets located at varying distances and directions. As of July 2008, 100 APG-79 sets had been delivered to the United States Navy, and the Navy expects to order around 437 production radars. In January 2013, the Director, Operational Test & Evaluation (DOT&E) disclosed some issues with

1078-456: A rotating antenna, or similar passive array using phase or amplitude comparison . Typically RWRs store the detected pulses for a short period of time, and compare their broadcast frequency and pulse repetition frequency against a database of known radars. The direction to the source is normally combined with symbology indicating the likely purpose of the radar – airborne early warning and control , surface-to-air missile , etc. This technique

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1176-451: A signal and then listening for its echo off distant objects. Each of these paths, to and from the target, is subject to the inverse square law of propagation in both the transmitted signal and the signal reflected back. That means that a radar's received energy drops with the fourth power of the distance, which is why radar systems require high powers, often in the megawatt range, to be effective at long range. The radar signal being sent out

1274-415: A signal from a single source, split it into hundreds of paths, selectively delayed some of them, and sent them to individual antennas. The radio signals from the separate antennas overlapped in space, and the interference patterns between the individual signals were controlled to reinforce the signal in certain directions, and mute it in all others. The delays could be easily controlled electronically, allowing

1372-418: A small population of migrants and volunteers from other island groups and nations. Ebeye is one of the most densely populated places in the world. Many of its residents live in poverty. A coral reef (visible and able to be traveled at low tide) links them to Kwajalein and the rest of the outside world. A causeway at the northern end of the island provides a roadway that connects to several other islands, forming

1470-475: A small residential community of unaccompanied US personnel who deal with missions support and radar tracking. It also has a number of Japanese bunkers and buildings from World War II which are preserved in good condition. Roi-Namur used to be four islands: Roi, Namur, Enedrikdrik (Ane-dikdik), and Kottepina. Roi and Namur were joined by a causeway built by forced laborers working under the Japanese military; it

1568-636: A system like MAR could no longer deal with realistic attack scenarios, the Nike-X concept was abandoned in favor of much simpler concepts like the Sentinel program , which did not use MAR. A second example, MAR-II, was abandoned in-place on Kwajalein Atoll . The first Soviet APAR, the 5N65 , was developed in 1963–1965 as a part of the S-225 ABM system. After some modifications in the system concept in 1967 it

1666-464: A unique convergence of protected channels and small islands. The Nell area is unique and a popular destination for locals and Americans sailing through the area with proper permissions from the Republic of the Marshall Islands. (All non-leased islands are strictly off-limits to American base residents and personnel without applying for official permission.) Enmat ( Enm̧aat , [ɛnʲ(ʌ)mˠɑːtˠ] )

1764-419: A wide band even in a single pulse, a technique known as a "chirp". In this case, the jamming will be the same frequency as the radar for only a short period, while the rest of the radar pulse is unjammed. AESAs can also be switched to a receive-only mode, and use these powerful jamming signals to track its source, something that required a separate receiver in older platforms. By integrating received signals from

1862-460: A wider angle of total coverage. This high off-nose pointing allows the AESA equipped fighter to employ a crossing the T maneuver, often referred to as "beaming" in the context of air-to-air combat, against a mechanically scanned radar that would filter out the low closing speed of the perpendicular flight as ground clutter while the AESA swivels 40 degrees towards the target in order to keep it within

1960-593: Is mo̧ or taboo, birthplace of the irooj (chiefly families) and off-limits to anyone without the blessing of the Iroijlaplap (paramount chief). The remains of a small Marshallese village and burial sites are still intact. This island is in the Mid-Atoll Corridor, and no one can reside there or on surrounding islands due to missile tests. Because of the Battle of Kwajalein of World War II ,

2058-495: Is 3,400 km (2,100 mi) from Honolulu , 3,200 km (2,000 mi) from Australia , and 3,400 km (2,100 mi) from Japan . Kwajalein Island is about 800 km (500 mi) north of the equator. Islands often have alternate names: The first is the Marshallese name, the second was assigned somewhat arbitrarily by the U.S. Navy prior to their attack on the atoll during World War II. The original name

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2156-489: Is 4.0 km (2.5 mi) long and averages about 730 m (800 yd) wide. To enlarge the island, the Americans placed fill at both the northwestern part of the island above the pier (within the atoll, by 1953), the northern part extending towards Ebeye, and the southwestern parts of the island (by 1970). The northern extension was used for housing, the remainder for industrial purposes. Kwajalein Island's population

2254-787: Is a more advanced, sophisticated, second-generation of the original PESA phased array technology. PESAs can only emit a single beam of radio waves at a single frequency at a time. The PESA must utilize a Butler matrix if multiple beams are required. The AESA can radiate multiple beams of radio waves at multiple frequencies simultaneously. AESA radars can spread their signal emissions across a wider range of frequencies, which makes them more difficult to detect over background noise , allowing ships and aircraft to radiate powerful radar signals while still remaining stealthy, as well as being more resistant to jamming. Hybrids of AESA and PESA can also be found, consisting of subarrays that individually resemble PESAs, where each subarray has its own RF front end . Using

2352-411: Is a simple radio signal, and can be received with a simple radio receiver . Military aircraft and ships have defensive receivers, called " radar warning receivers " (RWR), which detect when an enemy radar beam is on them, thus revealing the position of the enemy. Unlike the radar unit, which must send the pulse out and then receive its reflection, the target's receiver does not need the reflection and thus

2450-413: Is about 1,000, mostly made of Americans with a small number of Marshall Islanders and other nationalities, all of whom require express permission from the U.S. Army to live there. Some 13,500 Marshallese citizens live on the atoll, most of them on Ebeye Island . Other islands in the atoll: Ebeye is about 7.2 km (4.5 mi) north of eastern end of Kwajalein Island. It is not part of

2548-452: Is about 1.8 m (6 ft). The atoll was formed when volcanoes on the seabed from 165 to 76 mya built up enough lava that the land rose from beneath the sea. It cannot be determined how far above sea level the original land rose. Then coral started growing around the land/volcano, about 56 mya. Then the land subsided leaving the coral ring of the atoll. The water temperature averages 27 °C (81 °F) degrees. Underwater visibility

2646-455: Is about 31 km (19 mi) north of Kwajalein. It is a launch site for anti-ballistic missiles and is probably the most restricted island of all the U.S.-leased sites. It was originally built up as part of the Nike-X program, as the main island of Kwajalein was already filled with equipment from the earlier Nike Zeus program, some of which remained in use during Nike-X testing. A large berm

2744-511: Is along the islet's northern lagoon side. Ennylabegan ( Āneeļļap-kaņ , [ænʲeːllˠɑbʲ(ɛ)ɡɑnˠ] ), or "Carlos" Islet, is the site of a small Marshall Islander community that has decreased in size in recent decades; it was once a bigger village. Until 2012, it was actively used by the Reagan Test Site for telemetry tracking activities during missions and has been one of the only non-restricted Marshallese-populated islands used by

2842-417: Is common on ships, for instance. Unlike the radar, which knows which direction it is sending its signal, the receiver simply gets a pulse of energy and has to interpret it. Since the radio spectrum is filled with noise, the receiver's signal is integrated over a short period of time, making periodic sources like a radar add up and stand out over the random background. The rough direction can be calculated using

2940-454: Is much less useful against a radar with a frequency-agile (solid state) transmitter. Since the AESA (or PESA) can change its frequency with every pulse (except when using doppler filtering), and generally does so using a random sequence, integrating over time does not help pull the signal out of the background noise. Moreover, a radar may be designed to extend the duration of the pulse and lower its peak power. An AESA or modern PESA will often have

3038-506: Is possible to wade across the reef between Kwajalein and Little Bustard. Gugeegue or Gugegwe ( / ˈ ɡ uː dʒ i ɡ uː / GOO -jee-goo ; Marshallese: Kōn̄e-jekāān-eņ , [kɤŋeːzʲɛɡæːnʲɛːnˠ] ) is an islet north of Ebeye and is the northernmost point of the concrete causeway connecting the islets between them. Gugeegue is just south of the Bigej Pass which separates it from Bigej islet. Bigej , just north of

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3136-434: Is then disconnected and the antenna is connected to a sensitive receiver which amplifies any echos from target objects. By measuring the time it takes for the signal to return, the radar receiver can determine the distance to the object. The receiver then sends the resulting output to a display of some sort . The transmitter elements were typically klystron tubes or magnetrons , which are suitable for amplifying or generating

3234-493: Is typically 30 m (100 ft) on the ocean side of the atoll. The atoll has an extended oval shape running roughly WNW - ESE on the western side and then bending to run almost due south on the eastern side. It is framed by its three largest islands, Ebadon, Roi-Namur and Kwajalein, which are located at the extreme western, northern, and southern points, respectively. Roi-Namur is about 70 km (43 mi) east of Ebadon and 80 km (50 mi) NWN of Kwajalein. The atoll

3332-442: Is used. Target motion analysis can estimate these quantities by incorporating many directional measurements over time, along with knowledge of the position of the receiver and constraints on the possible motion of the target. Since each element in an AESA is a powerful radio receiver, active arrays have many roles besides traditional radar. One use is to dedicate several of the elements to reception of common radar signals, eliminating

3430-406: Is why AESAs are also known as low probability of intercept radars . Modern RWRs must be made highly sensitive (small angles and bandwidths for individual antennas, low transmission loss and noise) and add successive pulses through time-frequency processing to achieve useful detection rates. Jamming is likewise much more difficult against an AESA. Traditionally, jammers have operated by determining

3528-557: The Marshallese people of the Ralik chain. In Marshallese cosmology , Kwajalein island is the site of an abundant flowering zebra wood tree , thought to have spiritual powers. Marshallese from other islands came to gather the "fruits" of this tree. This, explain many elders, is a Marshallese metaphor that describes the past century of colonialism and serves to explain why Kwajalein is still so precious to foreign interests. This story

3626-651: The Ministry of the Navy to immediately expedite the process. A few months later, a naval officer stationed in Kwajalein sent a memorandum to the Naval Ministry denouncing the failure to ready the region for war. Both warnings were ignored by the Naval Ministry. Korean forced laborers were ordered to work throughout the Pacific beginning in the early 1940s. Over 10,000 were sent to the Nan'yō area alone, mostly from

3724-589: The Reagan Test Site ; it is a Marshallese island-city with shops, restaurants, and an active commercial port. It is the administrative center of the Republic of the Marshall Islands at Kwajalein Atoll and the Kwajalein Atoll Local Government (KALGOV). It has the largest population in the atoll, with approximately 13,000 residents living on 32 ha (80 acres) of land. Inhabitants are mostly Marshall Islanders but include

3822-659: The Ronald Reagan Ballistic Missile Defense Test Site , with various radars , tracking cameras, missile launchers, and many support systems spread across many islands. One of the five ground stations used in controlling the operation of the Global Positioning System (GPS) navigation system is located on Kwajalein. The Marshall Islands are a dependent nation through the Free Compact of Association with

3920-477: The atoll is named Kwajalein Island , which its majority English-speaking residents (about 1,000 mostly U.S. civilian personnel) often use the shortened name, Kwaj / k w ɑː dʒ / . The total land area of the atoll amounts to just over 6 square miles (16 km ). It lies in the Ralik Chain , 2,100 nautical miles (3,900 km; 2,400 mi) southwest of Honolulu, Hawaii . The US Navy has hosted

4018-477: The "South Seas" ( 南洋 , Nan'yō ) in the 19th century, prior to its imperial expansion into Korea and China . By 1875, ships from the newly established Imperial Japanese Navy began to hold training missions in the area. Shigetaka Shiga , a writer who accompanied a Navy cruise to the region in 1886, published his Current State of Affairs in the South Seas ( 南洋時事 , Nan'yō jiji ) in 1887, marking

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4116-492: The 'building blocks' of an AESA radar. The requisite electronics technology was developed in-house via Department of Defense research programs such as MMIC Program. In 2016 the Congress funded a military industry competition to produce new radars for two dozen National Guard fighter aircraft. Radar systems generally work by connecting an antenna to a powerful radio transmitter to emit a short pulse of signal. The transmitter

4214-641: The 1940s; it was left incomplete at the time of the American invasion in 1944. On February 1, 1942, the USS Enterprise (CV-6) launched a series of raids on the Roi Namur airfield and merchant shipping in Carlos Pass, where they sank several ships. In Kwajalein, forced laborers from across the empire and Marshallese volunteers known as teishintai ( 挺身隊 ) built military facilities throughout

4312-444: The 1960s, followed by airborne sensors as the electronics shrank. AESAs are the result of further developments in solid-state electronics. In earlier systems the transmitted signal was originally created in a klystron or traveling wave tube or similar device, which are relatively large. Receiver electronics were also large due to the high frequencies that they worked with. The introduction of gallium arsenide microelectronics through

4410-448: The 1980s served to greatly reduce the size of the receiver elements until effective ones could be built at sizes similar to those of handheld radios, only a few cubic centimeters in volume. The introduction of JFETs and MESFETs did the same to the transmitter side of the systems as well. It gave rise to amplifier-transmitters with a low-power solid-state waveform generator feeding an amplifier, allowing any radar so equipped to transmit on

4508-462: The 8–10°N, as reported by the Villalobos expedition chroniclers. However, at some point in the late 18th century, due to some transcription error from the old Spanish maps, they start to appear in the nautical charts shifted northwards to 21°N, thus creating phantom islands of Los Jardines that, even if sought and never found, remained on charts of the Pacific until 1973. The atoll came under

4606-465: The AESA system of a Raptor to act like a WiFi access point, able to transmit data at 548 megabits per second and receive at gigabit speed; this is far faster than the Link 16 system used by US and allied aircraft, which transfers data at just over 1 Mbit/s. To achieve these high data rates requires a highly directional antenna which AESA provides but which precludes reception by other units not within

4704-517: The AESA's 60 degree off-angle limit. With a half wavelength distance between the elements, the maximum beam angle is approximately ± 45 {\displaystyle \pm 45} °. With a shorter element distance, the highest field of view (FOV) for a flat phased array antenna is currently 120° ( ± 60 {\displaystyle \pm 60} °), although this can be combined with mechanical steering as noted above. The first AESA radar employed on an operational warship

4802-665: The APG-79 radar during its initial operational testing, but upgrades have been made over time. The AN/APG-79(V)4 has been selected for retrofitting the F/A-18C/D and upgrading the fleets of F/A-18 fighters in Malaysia and the United States Marine Corps . The APG-79(V)4 is the first U.S. fighter radar to use gallium nitride (GaN) transmit/receive modules. Active electronically scanned array The AESA

4900-510: The American invasion of Kwajalein. Whether this figure represents Kwajalein islet or the whole atoll is unclear. Since no distinction was made between dead Japanese soldiers and Korean forced laborers in mass graves on Kwajalein, both are enshrined as war hero guardian spirits for the Japanese nation in Yasukuni Shrine . This enshrinement is solely due to the mingling of Korean and Japanese corpses in this one case and has not occurred with

4998-523: The Ebeye chain, is covered with tropical palm trees and jungle. People from Kwajalein have visited it for picnics and camping. It is a site of cultural significance to the indigenous people of Kwajalein atoll, as are most of the small islands throughout the atoll. Some Kwajalein atoll landowners have proposed developing Bigej to look similar to the landscaped beauty of Kwajalein islet, for the exclusive use of Kwajalein atoll landowners and their families. Meck

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5096-472: The Marshall Islands, plotting it on the map and specifying the location of some other islands. At the time, the atoll was known as Kuadelen and Kabajaia to Spain. In early November, 1875, a typhoon resulted in an 8 feet (2.4 m) storm surge , drowning everyone on Kwajalein Island. The German Empire annexed the Marshall Islands, including Kwajalein Atoll, as a protectorate on October 15, 1885. Japan had developed an interest in what it called

5194-437: The Nan'yō, colonial settlers outnumbered Micronesian natives by as much as ten to one, amounting to the most significant violation of Japan's League of Nations mandate. In the furthest eastern areas, however, immigrants remained in the minority. Contemporary testimony and postwar investigations have attested that Japan honored their agreement under the mandate to administer the islands peacefully. Nevertheless, Kwajalein along with

5292-498: The PESA, where the signal is generated at single frequencies by a small number of transmitters, in the AESA each module generates and radiates its own independent signal. This allows the AESA to produce numerous simultaneous "sub-beams" that it can recognize due to different frequencies, and actively track a much larger number of targets. AESAs can also produce beams that consist of many different frequencies at once, using post-processing of

5390-425: The Reagan Test Site. The village of Ebadon was much more heavily populated before the war, and it was where some of the irooj (chiefs) of Kwajalein Atoll grew up. Like many other key islets in the atoll, it has significant cultural and spiritual significance in Marshallese cosmology. Roi-Namur is the northernmost island in the atoll, located some distance north of Kwajalein. It has several radar installations and

5488-456: The Red Cross. The island acquired the nickname "Execution Island" because of the treatment and killing of prisoners at the hands of Japanese military staff. The Japanese military also tested biological warfare agents on prisoners there. After the war, a US Naval War Crimes court located on the atoll tried several Japanese naval officers for war crimes committed elsewhere; at least one officer

5586-479: The United States Army. As such, power and clean drinking water were provided to half of the island similar to the other military-leased islands. This has been phased out as the island ceases to be used for mission support. The power plant, which also performed water treatment, is no longer in use. Legan ( Am̧bo , [ɑmbˠo] ) is uninhabited but it has a few buildings on the southern part. Most of

5684-542: The United States, after their independence established in the 1980s from a U.N. Protectorate. The defense of the Kwajalein, and the Marshall Islands is the responsibility of the United States. The important missile test range has been a mutually agreed task, and many Marshalese work at the military bases. The atoll is also used as a base for orbital rocket launches with the Pegasus-XL rocket, and previously had

5782-471: The Zeus program ended in favor of the Nike-X system in 1963. The MAR (Multi-function Array Radar) was made of a large number of small antennas, each one connected to a separate computer-controlled transmitter or receiver. Using a variety of beamforming and signal processing steps, a single MAR was able to perform long-distance detection, track generation, discrimination of warheads from decoys, and tracking of

5880-454: The antennas beamwidth, whereas like most Wi-Fi designs, Link-16 transmits its signal omni-directionally to ensure all units within range can receive the data. AESAs are also much more reliable than either PESAs or older designs. Since each module operates independently of the others, single failures have little effect on the operation of the system as a whole. Additionally, the modules individually operate at low powers, perhaps 40 to 60 watts, so

5978-570: The atoll. The trauma of this experience, together with the influx of these young and underprepared soldiers, surprised the local population. Islanders who survived this period make clear distinctions in their recollections of civilian and military Japanese for this reason. This is the first known instance of forced relocation in Kwajalein Atoll, although similar events took place throughout the Marshall Islands. Archaeological evidence as well as testimony from Japanese and Marshallese sources indicate that this militarization would likely not have begun until

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6076-494: The atoll. These construction teams would repair the resulting damage from American bombing raids. A second wave of Japanese naval and ground forces was dispatched to Kwajalein in early 1943 from the Manchurian front. These soldiers were between the ages of 18 and 21, poorly trained, and had no experience in the tropics. The supply ships that were meant to provide them with food rations were sunk by American forces before reaching

6174-431: The atoll; many Japanese succumbed to illnesses like dengue fever and dysentery, as did many of the laborers. As the military situation worsened and the pressures of military ideology increased, soldiers at Kwajalein became harsher and more violent toward Marshall Islanders, whom they often suspected of spying for the Americans. Kwajalein was also the site of a prisoner of war camp, whose detainees were not registered with

6272-496: The beam to be steered very quickly without moving the antenna. A PESA can scan a volume of space much quicker than a traditional mechanical system. Additionally, thanks to progress in electronics, PESAs added the ability to produce several active beams, allowing them to continue scanning the sky while at the same time focusing smaller beams on certain targets for tracking or guiding semi-active radar homing missiles. PESAs quickly became widespread on ships and large fixed emplacements in

6370-429: The capability to alter these parameters during operation. This makes no difference to the total energy reflected by the target but makes the detection of the pulse by an RWR system less likely. Nor does the AESA have any sort of fixed pulse repetition frequency, which can also be varied and thus hide any periodic brightening across the entire spectrum. Older generation RWRs are essentially useless against AESA radars, which

6468-657: The combined signal from a number of TRMs to re-create a display as if there was a single powerful beam being sent. However, this means that the noise present in each frequency is also received and added. AESAs add many capabilities of their own to those of the PESAs. Among these are: the ability to form multiple beams simultaneously, to use groups of TRMs for different roles concurrently, like radar detection, and, more importantly, their multiple simultaneous beams and scanning frequencies create difficulties for traditional, correlation-type radar detectors. Radar systems work by sending out

6566-600: The control of Spain but was largely ignored by European powers during the 17th and 18th centuries except for some short-lived missionary expeditions, minor trading posts and demarcation treaties between the Iberian kingdoms (Portugal and Spain). In 1828–1829, Russian Navy captain Ludwig von Hagemeister made his final circumnavigation on the ship Krotky. During this journey, he surveyed the Menshikov Atoll (Kwajalein) in

6664-482: The establishment of Kwajalein's public school in 1935, schoolteachers were sent to the island from Japan. Most Marshall Islanders who recall those times describe a peaceful time of cooperation and development between Japanese and Marshallese, although the latter were not considered on the same social tier as Japanese. By the 1930s, immigration from the Japanese mainland had increased exponentially. In some regions of

6762-575: The first of several series of nuclear tests (comprising a total of 67 blasts) at the Marshall island atolls of Bikini and Enewetak . Significant portions of the native population were forced to relocate as a result of American weapons testing and military activity in the islands between 1945 and 1965. The German heavy cruiser Prinz Eugen was towed to Kwajalein from Bikini Atoll after the Operation Crossroads nuclear tests. It developed

6860-470: The first time a Japanese civilian published a firsthand account of Micronesia. Three years later, Shiga advocated for annexation of the area by claiming that doing so would "excite an expeditionary spirit in the demoralized Japanese race." Despite the appeal imperialism had for the Japanese public at the time, neither the Meiji government nor the Navy seized any pretexts to fulfill this popular aspiration. It

6958-428: The heavy bombardment. Taking refuge in bunkers resulted in many Marshallese deaths when their shelters were destroyed by hand grenades. Some Marshallese were reportedly induced to fight by Japanese propaganda which, as would occur later in the Battle of Okinawa , stated that the Americans would indiscriminately rape and massacre the civilian population if they successfully took the atoll. On February 6, 1944, Kwajalein

7056-486: The island is thick and jungle-covered, like most in the Marshall Islands. Unlike most islands, Legan has a very small lake in the middle. Illeginni was used as a remote launch site for Sprint and Spartan missiles during the 1970s, with Meck as the primary control center. Coral soil dredged from the northeastern tip of the island was piled up to build a berm supporting the missile launchers. Several remotely-controlled tracking cameras and other devices were also built on

7154-454: The island, adding to the destruction. Of the 8,782 Japanese personnel deployed to the atoll, including forced laborers, 7,870 were killed. U.S. military documents do not differentiate between the Japanese and Korean dead. However, the Korean government's Truth Commission for Forced Labor Under Japanese Imperialism reports an official figure from the Japanese government of 310 Koreans killed in

7252-480: The island, although access is granted for islanders who need to use the air terminal to fly to Kwajalein. Little Bustard ( Orpāp , [worˠ(ɤ)bʲæpʲ] ) and Big Bustard ( Epjā-dik , [ɛbʲ(ɛ)zʲæːrʲik] , 'little Ebeye ') are the first and second islets respectively north of Kwajalein island on the East reef, and are the only islets between Kwajalein and Ebeye . During low tide and with protective boots, it

7350-483: The island, and serviced by boats or helicopters landing on a pad on the western end of the island. Today a single tracking camera remains in use, along with telemetry equipment to support it. Illeginni was used successfully for the first Minuteman III land impact test in 1980. It also hosts one of the two remote receivers for the TRADEX radar, the other being on Gellinam and the main radar on Roi-Namur. Nell has

7448-473: The lagoon contains the wrecks of many ships and aircraft. Most of the ships were merchant vessels. Barracuda Junction is about 1.6 km (1 mi) northeast of the southern tip of Enubuj (Carlson) Island. The atoll has a tropical rainforest climate under the Köppen climate classification . The average temperature varies less than 1.1 °C (2 °F) from month to month. The record low from 1950 to 1969

7546-562: The need for a large high-voltage power supply is eliminated. Replacing a mechanically scanned array with a fixed AESA mount (such as on the Boeing F/A-18E/F Super Hornet ) can help reduce an aircraft's overall radar cross-section (RCS), but some designs (such as the Eurofighter Typhoon and Gripen NG ) forgo this advantage in order to combine mechanical scanning with electronic scanning and provide

7644-464: The need for a separate radar warning receiver. The same basic concept can be used to provide traditional radio support, and with some elements also broadcasting, form a very high bandwidth data link . The F-35 uses this mechanism to send sensor data between aircraft in order to provide a synthetic picture of higher resolution and range than any one radar could generate. In 2007, tests by Northrop Grumman , Lockheed Martin, and L-3 Communications enabled

7742-433: The one to be used to jam. Most radars using modern electronics are capable of changing their operating frequency with every pulse. This can make jamming less effective; although it is possible to send out broadband white noise to conduct barrage jamming against all the possible frequencies, this reduces the amount of jammer energy in any one frequency. An AESA has the additional capability of spreading its frequencies across

7840-472: The operating frequency of the radar and then broadcasting a signal on it to confuse the receiver as to which is the "real" pulse and which is the jammer's. This technique works as long as the radar system cannot easily change its operating frequency. When the transmitters were based on klystron tubes this was generally true, and radars, especially airborne ones, had only a few frequencies to choose among. A jammer could listen to those possible frequencies and select

7938-472: The outbound interceptor missiles. MAR allowed the entire battle over a wide space to be controlled from a single site. Each MAR, and its associated battle center, would process tracks for hundreds of targets. The system would then select the most appropriate battery for each one, and hand off particular targets for them to attack. One battery would normally be associated with the MAR, while others would be distributed around it. Remote batteries were equipped with

8036-568: The remains of other Korean forced laborers elsewhere. Additionally, while many of the native Marshallese successfully fled the island in their canoes just before the battle, an estimated 200 were killed on the atoll during the fighting. Kwajalein was one of the few locations in the Pacific War where indigenous islanders were recorded to have been killed while fighting for the Japanese. Many Marshallese dead were found among those killed in bunkers. The flat island offered no other protection against

8134-782: The rest of the territories in the Nan'yō began to be fortified militarily after Japan's departure from the League of Nations in 1933. With the assistance of the Imperial Japanese Navy, local infrastructure was improved between 1934 and 1939. The first combat units, from the Imperial Japanese Navy's 4th Fleet , arrived in February 1941. Prior to the attack on Pearl Harbor , militarization of the Nan'yō, including Kwajalein, had been considered meagre enough that it alarmed Admiral Shigeyoshi Inoue , who in January 1941 strongly urged

8232-615: The runway. After the Army's main ABM programs shut down in the 1970s, Meck has served as the primary launch site for a variety of follow-on programs, including the Homing Overlay Experiment and THAAD , among many others. Omelek , about 5 km (3.1 mi) north of Meck, is uninhabited and leased by the U.S. military. From 2006 to 2009, it was used by SpaceX to launch five Falcon 1 rockets. Enubuj ( Āne-buoj , [ænʲeːbˠuotʲ] ), or "Carlson" Islet which

8330-477: The signal drops off only as the square of distance. This means that the receiver is always at an advantage [neglecting disparity in antenna size] over the radar in terms of range - it will always be able to detect the signal long before the radar can see the target's echo. Since the position of the radar is extremely useful information in an attack on that platform, this means that radars generally must be turned off for lengthy periods if they are subject to attack; this

8428-417: The southernmost provinces of Chōsen . In some atolls, such as Wotje , those forced laborers were joined by Japanese prisoners from Hokkaido , most of them political dissidents. In order to build the aerial runway on Kwajalein Island, the Japanese public school was demolished and, along with the civil administration, moved to Namu Atoll . Islanders were forcibly moved to live on some of the smaller islets in

8526-530: The targets' own radar along with a lower rate of data from its own broadcasts, a detection system with a precise RWR like an AESA can generate more data with less energy. Some receive beamforming-capable systems, usually ground-based, may even discard a transmitter entirely. However, using a single receiving antenna only gives a direction. Obtaining a range and a target vector requires at least two physically separate passive devices for triangulation to provide instantaneous determinations, unless phase interferometry

8624-414: Was 21 °C (70 °F). The highest temperature was 36 °C (97 °F). While tropical rainforest climates have no true dry season , the atoll's noticeably drier season occurs from January through March. The average annual rainfall was 2,570 millimetres (101.2 in). The average monthly relative humidity is between 78 and 83%. Kwajalein ( Kuwajleen ) Atoll is an important cultural site to

8722-583: Was built at Sary Shagan Test Range in 1970–1971 and nicknamed Flat Twin in the West. Four years later another radar of this design was built on Kura Test Range , while the S-225 system was never commissioned. US based manufacturers of the AESA radars used in the F-22 and Super Hornet include Northrop Grumman and Raytheon. These companies also design, develop and manufacture the transmit/receive modules which comprise

8820-478: Was built on the northern end of the island to support the missile silos, while a Missile Site Radar was built to its south, on the western side. An airstrip, somewhat longer than 300 m (1,000 ft) running north–south at the southeastern end of the island provided STOL service to the base, although the strong prevailing winds from the west made for very tricky landings. Air service was later deemed too dangerous, and replaced by helicopter pads at either end of

8918-436: Was claimed by the United States and was designated, with the rest of the Marshall Islands, as a United Nations Trust Territory under the United States. In the years following, Kwajalein Atoll was converted into a staging area for campaigns in the advance on the Japanese homeland in the Pacific War . After the war ended, the United States used it as a main command center and preparation base in 1946 for Operation Crossroads ,

9016-420: Was condemned to death. On January 31, 1944, the 7th Infantry Division , spearheaded by the 111th Infantry Regiment performed an amphibious assault on Kwajalein. On February 1, 1944, Kwajalein was the target of the most concentrated bombardment of the Pacific War . An estimated 36,000 shells from naval ships and ground artillery on a nearby islet struck Kwajalein. B-24 Liberator bombers aerially bombarded

9114-415: Was considered too difficult for English speakers to properly differentiate among the islands. The latter has often been retained by English speakers. The exception to this is Kwajalein itself, which is close to the native name; the received spelling is from German, however. Kwajalein Island is the southernmost and largest of the islands in the atoll. The area is about 3.1 km (1.2 sq mi). It

9212-432: Was filled with sand that was dredged from the lagoon by both the Japanese and later American administration between 1940 and 1945. After the war, the resulting conjoined islands were renamed Roi-Namur. There is a significant indigenous Marshall Islander workforce that commutes to Roi-Namur from the nearby island of Ennubirr, much like workers commute from Ebeye to Kwajalein. These workers are badged and have limited access to

9310-461: Was its 1944 World War II U.S. operation codename, is situated next to Kwajalein to the northwest, directly west of Little Bustard. It was from this island that U.S. forces launched their amphibious invasion of Kwajalein island. Today, it is the site of a small Marshallese village with a church and small cemetery. The sunken vessel Prinz Eugen , used during the Bikini Atoll atomic weapons tests,

9408-698: Was the Japanese OPS-24 manufactured by Mitsubishi Electric introduced on the JDS Hamagiri (DD-155), the first ship of the latter batch of the Asagiri-class destroyer , launched in 1988. Kwajalein Atoll Kwajalein Atoll ( / ˈ k w ɑː dʒ ə l ɪ n / ; Marshallese : Kuwajleen [kʷuwɑzʲ(ɛ)lʲɛːnʲ] ) is part of the Republic of the Marshall Islands (RMI). The southernmost and largest island in

9506-506: Was the origin of the name Kuwajleen , which apparently derives from Ri-ruk-jan-leen , "the people who harvest the flowers". The first recorded sighting of Kwajalein by Europeans was during the Spanish expedition of Ruy López de Villalobos in January 1543. The atoll was charted as Los Jardines (The Gardens) because of its fresh appearance and trees. Los Jardines remained well located in most 16th and 17th century charts in

9604-544: Was through the commercial operations of fisherman and traders that the Japanese first began to make a wider presence in the region, which continued to grow despite challenges from competing German commercial interests. At the outbreak of World War I in Europe, Japan joined the Triple Entente and seized the Marshall Islands against only token resistance. In 1922 the islands were placed under Japanese administration as

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