09 December 2009
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.
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
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