The Eagle Pass TARS site, north of Laredo, is one of eight or so active 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. The Eagle Pass TARS is one of three active TARS locations along the Rio Grande River, which is the border in Texas. The range of the TARS radar is around 200 miles, so TARS sites are less than 400 miles apart from one another.
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