Radar Exploration of Mars: Recent Results and Progresses - Planetary Exploration and Science: Recent Results and Advances - page 76

The principle of radar, namely, the possibility of target detection offered by
shortwaves, was for the first time announced in June 1922 by Italian physicist
Guglielmo Marconi in a famous speech at the Institute of Radio Engineers (USA):
“As it was for the first time demonstrated by Hertz, electric waves can be completely
reflected by conducting bodies. In my experience, I found reflection and detection
effects of electric waves by metallic objects at a distance of miles. I think it should
be possible to design a device by means of which a ship can radiate a wave beam
in a desired direction in order that, if those waves encounter a metal object, such
as another ship, they will be reflected to a receiver, shielded with respect to the
transmitter of the transmitting ship, immediately indicating the presence and bearing
of the other ship in fog or bad weather.”
In 1922, engineer Albert Taylor of the Naval Research Laboratory (NRL) in
Washington, DC, made the first observation of the radar effect. He observed that a
ship passing between a transmitter and a receiver reflected some of the radio waves
back to the transmitter. In 1930, further tests at the NRL showed a fluctuation in the
signal when a plane flied through a beam from a transmitting antenna. Finally, when
scientists and engineers learned how to use a single antenna for both transmitting
and receiving, the interest for radar and its capabilities of tracking aircraft and ships
grew worldwide.
The technologies that led to the modern version of radar were developed
independently and in great secrecy before the Second World War especially in
France, Germany, Italy, Japan, the Netherlands, the Soviet Union, the United
Kingdom, and the United States.
Though the first studies on radar devices have been developed in the United
States, the British were the first to investigate the feasibility of aircraft detection
by electromagnetic waves propagation and to fully exploit radar as a defense system
against aircraft attack. Those studies let sir Robert Watson-Watt to the production
of a first prototype in 1935, which he called RADAR. The most notable result of
British efforts was the Chain Home network of radars which defended Great Britain
by detecting approaching German aircrafts in the Battle of Britain in 1940.
After those first exploitations in the military field, radar evolved as a useful device
also in the civil field. A natural evolution of military radar was to equip aircrafts
with radar device warning of obstacles in their path, displaying weather information
and giving accurate altitude readings, while in the marine field, radars are used
to measure the distance between ships to prevent collision, to navigate, and to fix
position at sea when within range of shore or other fixed references such as islands.
In the course of time, radar extended its application to air traffic control, vessel
traffic service, meteorological monitoring, radar astronomy, antimissile systems,
and outer space surveillance.
In geology, specialized ground-penetrating radars are used to map the composi-
tion of Earth crust. At the end of the twentieth century, the feasibility of using such
radars to investigate Mars subsurface has been studied. And at the beginning of the
twenty-first century, two different space missions to the Red Planet carried a radar
as part of their payloads.