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Pulse-doppler Radar
A pulse-Doppler radar is a radar system that determines the range to a target using pulse-timing techniques, and uses the Doppler effect of the returned signal to determine the target object's velocity. It combines the features of pulse radars and continuous-wave radars, which were formerly separate due to the complexity of the electronics. The first operational Pulse Doppler radar was in the CIM-10 Bomarc, an American long range supersonic missile powered by ramjet engines, and which was armed with a W40 nuclear weapon to destroy entire formations of attacking enemy aircraft. Pulse-Doppler systems were first widely used on fighter aircraft starting in the 1960s. Earlier radars had used pulse-timing in order to determine range and the angle of the antenna (or similar means) to determine the bearing. However, this only worked when the radar antenna was not pointed down; in that case the reflection off the ground overwhelmed any returns from other objects. As the ground moves at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moving Target Indicator
Moving target indication (MTI) is a mode of operation of a radar to discriminate a target against the clutter. It describes a variety of techniques used for finding moving objects, like an aircraft, and filter out unmoving ones, like hills or trees. It contrasts with the modern stationary target indication (STI) technique, which uses details of the signal to directly determine the mechanical properties of the reflecting objects and thereby find targets whether they are moving or not. Early MTI systems generally used an acoustic delay line to store a single pulse of the received signal for exactly the time between broadcasts (the pulse repetition frequency). This stored pulse will be sent to the display along with the next received pulse. The result was that the signal from any objects that did not move mixed with the stored signal and became muted out. Only signals that changed, because they moved, remained on the display. These were subject to a wide variety of noise effects that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue Angels
The Blue Angels is a flight demonstration squadron of the United States Navy."History of the Blue Angels" Blue Angels official site. Formed in 1946, the unit is the second oldest formal aerobatic team in the world, after the French formed in 1931. The team, composed of six Navy and one Marine Corps demonstration pilot, fly Boeing F/A-18 Super Hornets. The Blue Angels typically perform aerial displays in at least 60 shows annually at 30 location ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terrain Mask
Nap-of-the-earth (NOE) is a type of very low-altitude flight course used by military aircraft to avoid enemy detection and attack in a high-threat environment. Other, mostly older terms include "ground-hugging", "terrain masking", "flying under the radar" and "hedgehopping". During NOE flight, geographical features are used as cover, exploiting valleys and folds in the terrain by flying in, rather than over, them. This keeps the aircraft below enemy air defence radar coverage, avoiding being silhouetted against the sky. Purpose NOE is used to minimize detection by hostile aircraft, AWACS surveillance and control systems, ground-based radar, or attack targets. A high-flying aircraft can be detected by defense systems at long range, giving an air defense system time to react, alerting SAM and AAA systems and fighter aircraft. Using NOE flight, the approach may be undetected; the aircraft "pops up" to attack the target and then turns to escape before the enemy can respond. Dopp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chaff (countermeasure)
Chaff, originally called Window by the British and ''Düppel'' by the Second World War era German Luftwaffe (from the Berlin suburb where it was first developed), is a radar countermeasure in which aircraft or other targets spread a cloud of small, thin pieces of aluminium, metallized glass fibre or plastic, which either appears as a cluster of primary targets on radar screens or swamps the screen with multiple returns, in order to confuse and distract. Modern armed forces use chaff (in naval applications, for instance, using short-range SRBOC rockets) to distract radar-guided missiles from their targets. Most military aircraft and warships have chaff dispensing systems for self-defense. An intercontinental ballistic missile may release in its midcourse phase several independent warheads as well as penetration aids such as decoy balloons and chaff. Modern radar systems can distinguish chaff from target objects by measuring the Doppler shift; chaff quickly loses speed compared ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weather
Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the troposphere, just below the stratosphere. Weather refers to day-to-day temperature, precipitation, and other atmospheric conditions, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, "weather" is generally understood to mean the weather of Earth. Weather is driven by air pressure, temperature, and moisture differences between one place and another. These differences can occur due to the Sun's angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the largest scale atmospheric circulations: the Hadley cell, the Ferrel cell, the polar cell, and the jet stream. Weather ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lockheed YF-12
The Lockheed YF-12 was an American Mach 3+ capable, high-altitude interceptor prototype, developed and manufactured by American aerospace company Lockheed Corporation. It was developed during the late 1950s and early 1960s as a potential replacement for the F-106 Delta Dart interceptor for the United States Air Force (USAF). The YF-12 was a twin-seat version of the then-secret single-seat Lockheed A-12 reconnaissance aircraft operated by the Central Intelligence Agency (CIA); unlike the A-12, it was furnished with the Hughes AN/ASG-18 fire-control radar and could be armed with AIM-47 Falcon (GAR-9) air-to-air missiles. Its maiden flight was on 7 August 1963. Its existence was publicly revealed by President Lyndon B. Johnson on 24 February 1964; this move was to provide plausible deniability for the CIA-operated A-12 fleet, which closely resembled the prototype YF-12. During the 1960s, the YF-12 underwent flight evaluations by the USAF, but funding to put it into oper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American XF-108 Rapier
The North American XF-108 Rapier was a proposed long-range, high-speed interceptor aircraft designed by North American Aviation intended to defend the United States from supersonic Soviet strategic bombers. The aircraft would have cruised at speeds around with an unrefueled combat radius over , and was equipped with radar and missiles offering engagement ranges up to against bomber-sized targets. To limit development costs, the program shared engine development with the North American XB-70 Valkyrie strategic bomber program, and used a number of elements of earlier interceptor projects. The program had progressed only as far as the construction of a single wooden mockup when it was cancelled in 1959, due to a shortage of funds and the Soviets' adoption of ballistic missiles as their primary means of nuclear attack. Had it flown, the F-108 would have been the heaviest fighter of its era. Prior to the project's cancellation, U.S. President Dwight D. Eisenhower noted that ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hughes AN/ASG-18 Fire Control System
The Hughes AN/ASG-18 Fire Control System was a prototype airborne fire control radar system for the planned North American XF-108 Rapier interceptor aircraft, and the Lockheed YF-12 for the United States Air Force. It was the US's first Pulse-Doppler radar, giving it look-down/shoot-down capability, and was also the first track while scan radar (could track one target at a time). This was paired with an infrared search and track (IRST) system. Range of the radar was estimated at between 200 and 300 miles (322 to 482 km), with reliable detection of bomber-sized targets at 100 miles. The installation itself was massive, weighing 2,100 lb (953 kg), and taking up most of the nose of the aircraft. The system was to be used with the Hughes AIM-47 Falcon missile, which also had a range of about 100 miles. While development work was done with the XF-108, the AN/ASG-18 and Falcon missiles were first tested on a highly modified Convair B-58 Hustler bomber. To fit the radar, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AN/SPG-51
The AN/SPG-51 is an American tracking / illumination fire-control radar for RIM-24 Tartar and RIM-66 Standard missiles. It is used for target tracking and Surface-to-air missile guidance on s, s, and s. The Italian Navy used it aboard their ''Audace'' class, ''Durand de la Penne'' class and s. The French ''Cassard'' class, Royal Netherlands Navy ''Tromp'' class and Spanish ''Baleares'' class frigates also use this system. Older variants were used on s, as well as the related German ''Lütjens'' class and ''Perth'' class used by the Royal Australian Navy. Aircraft tracking is based on monopulse radar utilizing Pulse-Doppler radar signal processing in MK 74 MOD 14 and MK 74 MOD 15. The MK 74 MOD 15 configuration includes continuous-wave radar tracking in addition to pulse-Doppler tracking. It provides illumination for bistatic radar operation associated with missile guidance in all configurations. Older systems rely on conical scanning Conical scanning is a system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence (physics)
In physics, two wave sources are coherent if their frequency and waveform are identical. Coherence is an ideal property of waves that enables stationary (i.e., temporally or spatially constant) interference. It contains several distinct concepts, which are limiting cases that never quite occur in reality but allow an understanding of the physics of waves, and has become a very important concept in quantum physics. More generally, coherence describes all properties of the correlation between physical quantities of a single wave, or between several waves or wave packets. Interference is the addition, in the mathematical sense, of wave functions. A single wave can interfere with itself, but this is still an addition of two waves (see Young's slits experiment). Constructive or destructive interference are limit cases, and two waves always interfere, even if the result of the addition is complicated or not remarkable. When interfering, two waves can add together to create a wave of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traveling Wave Tube
A traveling-wave tube (TWT, pronounced "twit") or traveling-wave tube amplifier (TWTA, pronounced "tweeta") is a specialized vacuum tube that is used in electronics to amplify radio frequency (RF) signals in the microwave range. The TWT belongs to a category of "linear beam" tubes, such as the klystron, in which the radio wave is amplified by absorbing power from a beam of electrons as it passes down the tube. Although there are various types of TWT, two major categories are: *''Helix TWT'' - in which the radio waves interact with the electron beam while traveling down a wire helix which surrounds the beam. These have wide bandwidth, but output power is limited to a few hundred watts. *''Coupled cavity TWT'' - in which the radio wave interacts with the beam in a series of cavity resonators through which the beam passes. These function as narrowband power amplifiers. A major advantage of the TWT over some other microwave tubes is its ability to amplify a wide range of frequencie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
