Radar

The invention: An electronic system for detecting objects at great

distances, radar was a major factor in the Allied victory ofWorld

War II and now pervades modern life, including scientific research.

The people behind the invention:

Sir Robert Watson-Watt (1892-1973), the father of radar who

proposed the chain air-warning system

Arnold F. Wilkins, the person who first calculated the intensity

of a radio wave

William C. Curtis (1914-1976), an American engineer

Looking for Thunder

Sir RobertWatson-Watt, a scientist with twenty years of experience

in government, led the development of the first radar, an acronym

for radio detection and ranging. “Radar” refers to any instrument

that uses the reflection of radio waves to determine the

distance, direction, and speed of an object.

In 1915, during World War I (1914-1918), Watson-Watt joined

Great Britain’s Meteorological Office. He began work on the detection

and location of thunderstorms at the Royal Aircraft Establishment

in Farnborough and remained there throughout the

war. Thunderstorms were known to be a prolific source of “atmospherics”

(audible disturbances produced in radio receiving apparatus

by atmospheric electrical phenomena), andWatson-Watt

began the design of an elementary radio direction finder that

gave the general position of such storms.





Research continued after

the war and reached a high point in 1922 when sealed-off

cathode-ray tubes first became available. With assistance from

J. F. Herd, a fellow Scot who had joined him at Farnborough, he

constructed an instantaneous direction finder, using the new

cathode-ray tubes, that gave the direction of thunderstorm activity.

It was admittedly of low sensitivity, but it worked, and it was

the first of its kind.Watson-Watt did much of this work at a new site at Ditton Park,

near Slough, where the National Physical Laboratory had a field

station devoted to radio research. In 1927, the two endeavors were

combined as the Radio Research Station; it came under the general

supervision of the National Physical Laboratory, withWatson-Watt

as the first superintendent. This became a center with unrivaled expertise

in direction finding using the cathode-ray tube and in studying

the ionosphere using radio waves. No doubt these facilities

were a factor when Watson-Watt invented radar in 1935.

As radar developed, its practical uses expanded. Meteorological

services around the world, using ground-based radar, gave warning

of approaching rainstorms. Airborne radars proved to be a great

help to aircraft by allowing them to recognize potentially hazardous

storm areas. This type of radar was used also to assist research into

cloud and rain physics. In this type of research, radar-equipped research

aircraft observe the radar echoes inside a cloud as rain develops,

and then fly through the cloud, using on-board instruments to

measure the water content.

Aiming Radar at the Moon

The principles of radar were further developed through the discipline

of radio astronomy. This field began with certain observations

made by the American electrical engineer Karl Jansky in 1933

at the Bell Laboratories at Holmdell, New Jersey. Radio astronomers

learn about objects in space by intercepting the radio waves that

these objects emit.

Jansky found that radio signals were coming to Earth from space.

He called these mysterious pulses “cosmic noise.” In particular, there

was an unusual amount of radar noise when the radio antennas were

pointed at the Sun, which increased at the time of sun-spot activity.

All this information lay dormant until after World War II (1939-

1945), at which time many investigators turned their attention to interpreting

the cosmic noise. The pioneers were Sir Bernard Lovell at

Manchester, England, Sir Martin Ryle at Cambridge, England, and

Joseph Pawsey of the Commonwealth of Science Industrial Research

Organization, in Australia. The intensity of these radio waves was

first calculated by Arnold F.Wilkins.

As more powerful tools became available toward the end of

World War II, curiosity caused experimenters to try to detect radio

signals from the Moon. This was accomplished successfully in the

late 1940’s and led to experiments on other objects in the solar system:

planets, satellites, comets, and asteroids.

Impact

Radar introduced some new and revolutionary concepts into warfare,

and in doing so gave birth to entirely new branches of technology.

In the application of radar to marine navigation, the long-range

navigation system developed during the war was taken up at once

by the merchant fleets that used military-style radar equipment

without modification. In addition, radar systems that could detect

buoys and other ships and obstructions in closed waters, particularly

under conditions of low visibility, proved particularly useful

to peacetime marine navigation.

In the same way, radar was adopted to assist in the navigation of

civil aircraft. The various types of track guidance systems developed after the war were aimed at guiding aircraft in the critical last

hundred kilometers or so of their run into an airport. Subsequent

improvements in the system meant that an aircraft could place itself

on an approach or landing path with great accuracy.

The ability of radar to measure distance to an extraordinary degree

of accuracy resulted in the development of an instrument that

provided pilots with a direct measurement of the distances between

airports. Along with these aids, ground-based radars were developed

for the control of aircraft along the air routes or in the airport

control area.

The development of electronic computers can be traced back to

the enormous advances in circuit design, which were an integral part

of radar research during the war. During that time, some elements

of electronic computing had been built into bombsights and other

weaponry; later, it was realized that a whole range of computing operations

could be performed electronically. By the end of the war,

many pulse-forming networks, pulse-counting circuits, and memory

circuits existed in the form needed for an electronic computer.

Finally, the developing radio technology has continued to help

astronomers explore the universe. Large radio telescopes exist in almost

every country and enable scientists to study the solar system

in great detail. Radar-assisted cosmic background radiation studies

have been a building block for the big bang theory of the origin of

the universe.