This is one of eight or so Tethered Aerostat Radar System (TARS) program sites, from Arizona to Florida, operated by the federal government to monitor the US border with Mexico. At each site an unmanned blimp is held aloft, two miles up, tethered by a nylon cord spooled in a winch. Most TARS sites use the 420K blimp, a 208-foot-long balloon, filled with 420,000 cubic feet of helium, made by TCOM and Lockheed. Inside the blimp is more than a ton of radar equipment, powered by a diesel generator, capable of seeing any aircraft or boat, as small as an ultralight, within 200 miles. Radar data is transmitted wirelessly, and uploaded to a Defense Department data cloud. It is processed and analyzed in real time at the Air and Marine Operations Center (AMOC) at March Air Reserve Base, in Riverside, California. This TARS site, located at Yuma Proving Ground, went online in the late 1980s. It is the westernmost TARS, and covers the border from Arizona to the Pacific Ocean, watching for low-flying small aircraft that might be sneaking across the border.
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