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Heinrich Rudolf Hertz (1857–1894) -

It was German physicist Heinrich Rudolf Hertz whose research in the 1880s showed that radio waves were reflected by metallic objects.

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Groundbreaking experiments -

His groundbreaking experiments on electromagnetic radiation proved an earlier theory put forward by Scottish physicist James Clerk Maxwell (1831–1879) that both light and radio waves are examples of electromagnetic waves.

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Christian Hülsmeyer (1881–1957) -

German engineer Christian Hülsmeyer is actually the man credited with the invention of radar, although his 1904 patent for the apparatus he called a Telemobiloskop could not directly measure distance to a target. It was, though, the first device designed that used radio waves for detecting the presence of distant objects like ships.

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Radar in the First World War -

The First World War created an incentive for the advancement of radar technology. A number of European nations experimented with sound mirrors to detect the sound of aircraft engines at longer distances, but this method proved largely unreliable.

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Robert Watson-Watt (1892–1973) -

True radar technology evolved over the next two decades. In the 1930s, British scientists Robert Watson-Watt and Arnold Wilkins pioneered the use of radio signals to locate aircraft at long distances.

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Arnold Wilkins (1907–1985) -

It was Wilkins who suggested that reflected radio waves might be used to detect aircraft.

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Bouncing off aircraft -

To prove his theory, Wilkins arranged a demonstration where signals from a BBC short-wave transmitter were bounced off a Handley Page Heyford aircraft. It was a success.

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Chain Home radar system -

Watson-Watt led the development of a practical version of the device. This system, codenamed Chain Home, comprised a ring of coastal early warning radar stations built by the Royal Air Force (RAF).

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First early warning radar network -

Chain Home was the first early warning radar network in the world, and the first military radar system to reach operational status. It provided the vital advance information that helped the RAF in the Battle of Britain.

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Plan Position Indicator system -

In 1940, aircraft were being identified by radar controllers using a system known as a Plan Position Indicator (PPI). This system not only indicated how far away an aircraft was, but also at what speed it was traveling.

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Radio Detection and Ranging -

That same year, 1940, the US Navy coined the acronym we use today—RADAR (Radio Detection and Ranging).

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First marine radar -

It was also during the Second World War that marine radar was first used, installed in USS Semmes in 1941. By 1942, they were appearing in quantity in the US and British fleets.

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Post-war advancements in radar -

The ending of the Second World War saw radar development in Germany and Japan cease for several years. But for other countries, particularly the United States, Britain, and the USSR, the Cold War era had brought with it a new urgency in advancing radar technology.

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Pulse-Doppler radar -

New and better radar systems emerged during the late 1940s and throughout the 1950s. Notable among these was the Pulse-Doppler radar. This system, still in use today, determined the range to a target using pulse-timing techniques, and employs the Doppler effect of the returned signal to determine the target object's velocity. The Doppler effect is named after physicist Christian Doppler, who described the phenomenon in 1842.

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Monopulse radar -

Another important development was the monopulse radar, which used additional encoding of radio signals to provide accurate directional and tracking information.

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Phased-array radar -

The phased-array radar used an arrangement of antennas to create a beam of radio waves in order to track multiple objects. First introduced during the Second World War, phased-array radar systems are still in use today.

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Moving-target indication (MTI) radar -

A major development in radar technology in the 1960s was the introduction of moving-target indication (MTI) radar. Airborne MTI radar for aircraft detection was developed for the US Navy's Grumman E-2 "Hawkeye" airborne-early-warning (AEW) aircraft during this era.

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Missile detection -

The same decade saw the appearance of OHF (over-the-horizon) radar, a missile radar system with the ability to detect targets at very long ranges, typically hundreds to thousands of miles beyond the radar horizon. The first radars designed for detecting ballistic missiles and satellites also appeared.

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Digital radar -

The 1970s ushered in the age of digital radar. This new technology made practical the signal and data processing required for modern radar.

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A new frontier -

Radar also achieved a new frontier in the 1970s when it began to be used in spacecraft for remote sensing of the environment.

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Civilian radar use -

Besides its obvious military applications, radar revolutionized civilian Air Traffic Control (ATC) systems. Experiments in 1946 led in 1952 to its first routine use for approach and departure control.

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Beyond civil aviation -

For civil aviation, radar marked a huge step forward in an aircraft's technical performance and safety in the air. But radar proved invaluable in a number of other fields, including meteorology, medicine, and marine navigation.

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Weather radar -

In meteorology, weather patterns can be identified and traced using weather surveillance radar (WSR) and Doppler weather radar.

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Ocean topography -

By extension, radar is also employed in satellites to produce computer-generated maps of the topography of the Earth's oceans. The image here was created from data gathered by the Ocean Topography Experiment (TOPEX) satellite. The satellite uses a radar altimeter to measure height variations on the sea surface that reveals details about currents, eddies, seafloor geologic structures, winds, and waves.

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Vital navigation aid -

Since its inception in the early 1940s, marine radar has been used for locating other ships and land in a designated vicinity.

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New marine navigation devices -

As a vital navigation aid for mariners and recreation boaters, marine radar also helps in detecting obstacles and and weather systems, even if visibility is significantly degraded.

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Medical radar -

A medical radar system can be used for non-contact vital sign monitoring and clinical performance evaluation. For example, they can remotely measure periodic movements of the chest wall induced by breathing and heartbeats.

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Radar speed gun -

The radar gun is one of the most widely used radar devices today. It was invented in the late 1940s to measure the speed of moving objects. The radar gun is commonly used by police to check the speed of moving vehicles while conducting traffic enforcement.

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Applications in sport -

Radar guns are also used in professional sports circles to calculate speeds such as those of baseball pitches, tennis serves, and cricket bowls.

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Advanced radar innovation -

Today the electromagnetic spectrum is an increasingly contentious warfare domain. Technologies for advanced radar are about designing and testing intelligence, surveillance, and reconnaissance systems for use on the battlefield.

Sources: (Britannica) (SkyRadar) (ScienceDirect)

See also: Historic battlefields you can visit

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