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By Alaina G. Levine
As part of the APS historic sites initiative, on October 5, 2007 APS President-elect Arthur Bienenstock presented a plaque to MIT to commemorate the MIT Radiation Laboratory that played a key role in the development of radar during World War II. The citation on the plaque reads "At this location, the MIT Radiation Laboratory was established in the fall of 1940 to develop microwave radar systems. Radar quickly took its place in all arenas of World War II and played a decisive role in the Allied victory. The laboratory closed on December 31, 1945."
Radar, an acronym for Radio Detection And Ranging, works by transmitting electromagnetic waves and analyzing the reflecting echo off an object. It is used for detection and identification of objects’ velocity, range, and direction, among other characteristics. Although it was first patented in the UK, it wasn’t until the founding of the MIT Radiation Laboratory, also known as the "Rad Lab", that the use of and research in radar began to flourish and be used for military and other purposes.
The foundations of radar lie in the research conducted by German physicist Heinrich Hertz in the late 1880s1. In 1935, British scientist Sir Robert Watson-Watt patented radar for metrological purposes. But it wasn’t until 1939, when scientists at the University of Birmingham invented the cavity magnetron oscillator,2 that the use of radar to detect faraway objects became more of a reality. The magnetron produced 400 watts of power at higher frequencies, most notably in the microwave region, "enough to produce echoes from airplanes many miles away."3 It made microwave radar a "reality" in World War II.4
Britain was interested in developing practical applications for airborne microwave radar, but did not have the large-scale manufacturing ability to mass produce magnetrons5. So in 1940, Britain partnered with the US National Defense Research Committee (NDRC) to create opportunities to do so. In October of that year, MIT was selected at the site of a radar laboratory that would be staffed by scientists to build magnetrons and research microwave electronics. Fourteen months before the U.S. entered World War II, the MIT Radiation Laboratory was up and running.6
During the war, scientists at the Rad Lab moved quickly to develop microwave radar systems. Research focused on physical electronics, microwave physics, electromagnetic properties of matter, and microwave communication principles. Over the course of five years, researchers designed 50 percent of the radar used in World War II, invented over 100 different radar systems, and built $1.5 billion worth of radar.7 "The successful development of innovative and important microwave radars at the MIT Radiation Laboratory has been attributed to the urgency for meeting new military capabilities as well as to the enlightened and effective management of the laboratory and the recruitment of talented, dedicated scientists."8
One of the most important microwave radars designed by the MIT Radiation Laboratory was the SCR-584, a gunfire-control system. It utilized a four degree beamwidth and conical scan tracking – "in which a single offset…radar beam is continuously rotated about the radar antenna’s central axis" - to accurately "place anti-aircraft guns on target without the need for searchlights or optics, as was required for older radars with wider beamwidths."9 It was first employed in battle in 1944 at the Italian beachhead of Anzio. "Its introduction was timely, since the Germans by that time had learned how to jam its predecessor, the SCR-268. The introduction of the SCR-584 microwave radar caught the Germans unprepared."10
The MIT Radiation Laboratory employed upwards of 4000 people collaborating in several countries. "What began as a British-American effort to make microwave radar work, evolved into a centralized laboratory committed to understanding the theories behind experimental radar while solving its engineering problems."11 Though the lab was shuttered in 1945, its innovations, organization, and even surplus equipment contributed to the creation of MIT’s Research Laboratory of Electronics.12