Early warning radar
Encyclopedia
An early warning radar is any radar
system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in which to operate. This contrasts it with systems used primarily for tracking or gun laying, which tend to be shorter range but offer much higher accuracy.
, the US CXAM
(Navy) and SCR-270 (Army), and the German Freya
. By modern standards these were quite short range, typically about 100 to 150 miles. This "short" distance is a side effect of radio propagation
at the long wavelengths being used at the time, which were generally limited to line-of-sight. Although techniques for long-range propagation were known and widely used for shortwave radio, the ability to process the complex return signal was simply not possible at the time.
. Perhaps the most capable of these systems was the DEW Line
, although other examples have since been built with even better performance. An alternate early warning design was the McGill Fence, which provided "line breaking" indication across the middle of Canada
, with no provision to identify the target's exact location or direction of travel.
, as the high altitude exo-atmospheric trajectory of these weapons allows them to be seen at great ranges even from ground-based radars.
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in which to operate. This contrasts it with systems used primarily for tracking or gun laying, which tend to be shorter range but offer much higher accuracy.
History
The first early warning radars were the British Chain HomeChain Home
Chain Home was the codename for the ring of coastal Early Warning radar stations built by the British before and during the Second World War. The system otherwise known as AMES Type 1 consisted of radar fixed on top of a radio tower mast, called a 'station' to provide long-range detection of...
, the US CXAM
CXAM radar
The CXAM radar system was the first production radar system deployed on United States Navy ships. It followed several earlier prototype systems, such as the NRL radar installed in April 1937 on the destroyer ; its successor, the XAF, installed in December 1938 on the battleship ; and the first...
(Navy) and SCR-270 (Army), and the German Freya
Freya radar
Freya was an early warning radar deployed by Germany during World War II, named after the Norse Goddess Freyja. During the war over a thousand stations were built. A naval version operating on a slightly different wavelength was also developed as Seetakt...
. By modern standards these were quite short range, typically about 100 to 150 miles. This "short" distance is a side effect of radio propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
at the long wavelengths being used at the time, which were generally limited to line-of-sight. Although techniques for long-range propagation were known and widely used for shortwave radio, the ability to process the complex return signal was simply not possible at the time.
Cold War
Starting in the 1950s, a number of over the horizon radars were developed that greatly extended detection ranges, generally by bouncing the signal off the ionosphereIonosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
. Perhaps the most capable of these systems was the DEW Line
Distant Early Warning Line
The Distant Early Warning Line, also known as the DEW Line or Early Warning Line, was a system of radar stations in the far northern Arctic region of Canada, with additional stations along the North Coast and Aleutian Islands of Alaska, in addition to the Faroe Islands, Greenland, and Iceland...
, although other examples have since been built with even better performance. An alternate early warning design was the McGill Fence, which provided "line breaking" indication across the middle of Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, with no provision to identify the target's exact location or direction of travel.
Modern day
Today the early warning role has been supplanted to a large degree by airborne early warning platforms. By placing the radar on an aircraft, the line-of-sight to the horizon is greatly extended. This allows the radar to use high-frequency signals, offering high resolution, while still offering long range. A major exception to this rule are radars intended to warn of ballistic missile attacks, like BMEWSBallistic Missile Early Warning System
The United States Air Force Ballistic Missile Early Warning System was the first operational ballistic missile detection radar. The original system was built in 1959 and could provide long-range warning of a ballistic missile attack over the polar region of the Northern Hemisphere. They also...
, as the high altitude exo-atmospheric trajectory of these weapons allows them to be seen at great ranges even from ground-based radars.
Early systems
- Chain HomeChain HomeChain Home was the codename for the ring of coastal Early Warning radar stations built by the British before and during the Second World War. The system otherwise known as AMES Type 1 consisted of radar fixed on top of a radio tower mast, called a 'station' to provide long-range detection of...
- Chain Home LowChain Home LowChain Home Low was the name of a British radar early warning system, detecting enemy aircraft movement at lower altitudes than and summarily used with the fixed Chain Home system which was operated by the RAF during World War II...
- SCR-270
- AN/CPS-1
- CXAM radarCXAM radarThe CXAM radar system was the first production radar system deployed on United States Navy ships. It followed several earlier prototype systems, such as the NRL radar installed in April 1937 on the destroyer ; its successor, the XAF, installed in December 1938 on the battleship ; and the first...
- Freya radarFreya radarFreya was an early warning radar deployed by Germany during World War II, named after the Norse Goddess Freyja. During the war over a thousand stations were built. A naval version operating on a slightly different wavelength was also developed as Seetakt...
1950s through 70s
- Pinetree LinePinetree LineThe Pinetree Line was a series of radar stations located across the northern United States and southern Canada at about the 50th parallel north, along with a number of other stations located on the Atlantic and Pacific coasts. Run by NORAD , over half were manned by United States Air Force...
- McGill Fence
- DEW Line
- BMEWSBallistic Missile Early Warning SystemThe United States Air Force Ballistic Missile Early Warning System was the first operational ballistic missile detection radar. The original system was built in 1959 and could provide long-range warning of a ballistic missile attack over the polar region of the Northern Hemisphere. They also...
- Radar Type 80
- ROTORROTORROTOR was a huge and elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers...
- Oko
Operational Systems
- AWACS
- GIRAFFEGIRAFFE RadarThe Saab GIRAFFE Radar is a family of land and naval two- or three-dimensional G/H-band radar-based surveillance and air defense command and control systems tailored for operations with medium- and Short Range Air Defense missile or gun systems or for use as gap-fillers in a larger air defense...
- Jindalee
- Martello radar
- North Warning SystemNorth Warning SystemThe North Warning System is a joint United States and Canadian radar system for the atmospheric air defense of North America. It provides surveillance of airspace from potential incursions or attacks from across North America's polar region...
- PAVE PAWSPAVE PAWSPAVE PAWS is a United States Air Force Space Command radar system operated by three 21st Space Wing squadrons for missile warning and space surveillance. Operational PAVE PAWS radars are located at:...
- Red Dawn