PAR was one of two radars that were used in the Sentinel and Safeguard ABM systems. PAR provided long-range detection over wide areas on the order of thousands of miles, generating "tracks" for everything that came into view.
<p>The version illustrated here is essentially a minor adaptation of an earlier radar, MAR. MAR used separate transmitter (smaller disks) and receiver (larger) antenna arrays operating in the S-band microwave region. To lower costs, PAR operated in the VHF region, which greatly simplified the electrons. The system was further simplified by having only two "faces" scanning an area about 240 degrees across, whereas MAR could optionally have one to four faces providing up to 360 degree coverage.
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The PAR that was actually built in North Dakota was considerably different than this concept. Incorporating years of electronics improvements, the new PAR was able to send and receive from a single set of antennas. A single array of much larger size was used and the frequency was increased into the UHF band to help reduce problems from radar blackout. It looks like one of the faces of the building shown here, with one disk.
Bell Labs
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