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Radar

Radar (an acronym for radio detection and ranging) is a system that is used to ascertain the position and velocity of distant objects with the use of a certain range of electromagnetic wavelengths known as radio waves. A radar system consists of a transmitter and a receiver of radio waves, usually in the same location. The transmitter directs radio waves at an object, and upon contact with the object, the radio waves reflect or scatter in many directions; reflected radio waves travelling back to the radar system are picked up by the receiver. Because electromagnetic waves travel at the same speed in the same medium, the time it takes from the beginning of the pulse to the beginning of the reception can be used to determine the distance of the object. Because of the Doppler Effect, the wave will also change in frequency if the object is moving. This “Doppler shift” is used to find the speed of the object (Institute for Geophysics). Naturally, it would follow that radar finds much use in military and law-enforcement applications, as well as in certain fields of astronomy and meteorology.

History

Though radar has found a wide range of practical application in the modern world, its roots are at least a century old. In 1904, Christian Hulsmeyer, a German entrepreneur and inventor, first utilized radio waves to detect whether distant metallic objects were there or not. He further developed this system to be used for detecting ships and estimating the distance of said ships, naming the new system the telemobiloscope (Hollmann). This technology, spurred by the insight of an entrepreneur-inventor, would influence the development of radar in such a way that it would eventually find itself to be studied covertly by many nations, including the United States, France, Germany, Italy, Japan, and the Soviet Union. In turn, radar would be one of the several clandestine technological focuses before and during World War II because of the heavy implications it had for warfare.

Application

Military

The military uses of radar today, while more polished, are essentially the same as they have always been. Since radar gives data concerning the bearing and distance of an object, the military can use radar to determine the position and directions of aircraft, ships, and ground vehicles. This data can be used for parameters integral in systems such as air-defense systems, which the military uses to target and shoot down hostile airborne targets (such as planes and missiles). Consider the expectations of a stationary anti-aircraft (AA) battery: in order to effectively shoot down aircraft it has to aim its sights slightly in front of the aircraft, because whatever it is shooting takes time to travel to the aircraft. The faster and more distant an aircraft is, the more it has to be led by the AA-battery. A radar system provides the necessary information to allow accurate target leading, as it provides the velocity and position of the target that can be fed into a targeting system (Bureau of Meteorology).

Law Enforcement

The same information determined by radar can be put to use in law enforcement, where officers need to know whether a car was above a speed limit or not. Here, a radar system in a cheaper and more portable form is then needed; thus, the radar gun was made to assist officers in making objective decisions about the speed of a car. From the same principles integral to radar’s functioning, the radar gun consists of a transmitter and receiver in the same chassis. A radar signal is pulsed to the automobile in question and the receiver receives the Doppler shifted signal. This shift from the original pulse is fed into an equation that determines the speed of the car, which is then fed to an led screen as numerical data for the operator to interpret.

Radar Astronomy

In a more scientific setting, radar technology is used in radar astronomy to determine the distances and velocities of celestial objects. Whereas optical measurements using parallax lack high accuracy with objects that are not well illuminated, radar can directly measure the distance between the radar system and the object. Radar astronomy shines in the amount of control it gives the user over the signal transmitted, as well as the precision it has with objects within the solar system (Ostro 87-96).

Limitations

However, even radar has its limits. Since the amount of reflected radio waves received drops as distance increases, stronger transmitters are needed. However, current technology and resources bottlenecks the strength of transmitters used in radar astronomy, and so extrasolar objects are difficult to detect. Also, because the radar equation shows that the range of a radar is proportional to the square root of an object’s size, objects that are longer distances away need to be larger to gain accurate measurements with radar astronomy.

It is evident that radar has found major utilization in the modern world, despite its decades of use. Perhaps it is that radar seems to prevail where light based observation is limited: detecting a plane against the night sky is much easier with a radar than binoculars, as is detecting the dark face of a distant moon. In any case, radar is a technology that has helped shape what the world is today with its broad range of applications, both in practical and scientific use.

Sources

Hollmann, Martin. “Christian Huelsmeyer, the Inventor.” Radar. Radar World, 2007. Web. 03 Jan. 2014. <http://www.radarworld.org/huelsmeyer.html>.

“How Radar Works.” How Radar Works. Bureau of Meteorology, 2014. Web. 03 Jan. 2014. <http://www.bom.gov.au/australia/radar/about/what_is_radar.shtml>.

“How Radar Works.” How Radar Works. Institute for Geophysics, n.d. Web. 02 Jan. 2014. <http://www.ig.utexas.edu/research/projects/mars/education/radar_works.htm>.

Ostro, Steven J. “Radar Contributions to Asteroid Astrometry and Dynamics.” Celestial Mechanics And Dynamical Astronomy 66.1 (1997): 87-96. Print.


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