<p>The Zeus Acquisition Radar (ZAR) for the <i>Nike Zeus</i> anti-ballistic missile program on Kwajalein, Marshall Islands. The transmitter is the triangle in the foreground, the receiver is in the background.
The transmitter was built in a triangle form to allow the rapid scanning of the sky. In a typical single-reflector radar, the reflector would have to rotate through a complete circle before it re-visited a particular target. If you need rapid re-scanning, the rotation rate has to be increased. The ZAR solved this by using three reflectors and switching the transmitter to the one closest to the desired target. By continually switching between the faces, the scanning rate was tripled without requiring the antenna to rotate more rapidly.
</p><p>Designed to track warheads at hundreds of miles, the ZAR was extremely powerful, and its broadcasts were dangerous to anyone near the antenna. The large metal fence surrounding the transmitter is opaque to microwaves, and protects anyone walking around the site outside the fence. To access the radar while it was running, staff entered through the metal tunnel.
</p><p>The receiver antenna is located under the radome and is thus not visible in this image. It consisted of a stack of foam blocks with metal strips inside forming a Luneberg lens, nearly filling the entire radome. The entire assembly rotated in synchronicity with the transmitter. The hashed area surrounding the receiver is a large field of metal wires suspended off the ground on poles. This formed a reflector that make a perfect ground plane, improving the accuracy of vertical angle measurements. This technique was first used by British anti-aircraft radars early in WWII.
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The rectangular building between the two parts of the ZAR is a power plant that powers the system. The circular objects on the right are part of the island's water processing system.
U.S. Navy
<a rel="nofollow" class="external text" href="http://www.navy.mil/ah_online/department_arch.html">U.S. Navy All Hands magazine</a> <a rel="nofollow" class="external text" href="http://www.navy.mil/ah_online/archpdf/ah196301.pdf">January 1963</a>, p. 8.