If you want to hide something really, really big, there's no better place to do it than in the middle of the desert. Just ask any person who's ever buried treasure, or the US government. Case in point: these giant cement target crosses, scattered across the desert in Arizona. But what are they for-- and why in the middle of nowhere?

Turns out, the Arizona desert was the perfect place for the government to set up a calibration system for their then-super secret spy satellite cameras, known as Project Corona. Project Corona was a series of 144 satellites launched by the CIA between June of 1959 and May 1972. The purpose? To keep an eye on the Soviet Union, China, and other areas across the globe as Cold War tensions mounted. In fact, the project got fast-tracked after one of the US's U-2 spy planes was shot down over Soviet Russia. 

The intended purpose of the satellites was to take pictures of the Earth from space. The film was designed to fall back to Earth and be retrieved by a passing airplane in mid-air. Obviously, this took a few tries to nail down. Initial launches were plagued by issues with the cameras and the satellites, but the Corona cams quickly improved with time, and it wasn't long before they were remotely taking photos with ten, five, and eventually one foot resolution.

The crosses were used to calibrate the satellites by the people controlling them from an industrial park in Palo Alto, and later from the Sunnyvale Air Force Base. They formed a 16-mile by 16-mile grid (plus a few extra scattered around the edges), with 60-foot crosses serving as mile markers. In the middle of each cross is a marker that reads "CORPS OF ENGINEERS- U.S. ARMY SURVEY MARK $250 FINE OR IMPRISONMENT FOR DISTURBING THIS MARK." Nice and vague, but totally serious. In one verticle section of the crosses is a covered manhole, which according to Gary Morgan from the Warrenton, VA Cold War Museum in a post from borntourist.com was probably intended to house laser lights, which would improve calibration accuracy.

A good portion of the roughly 272 target crosses are gone now, either destroyed by the elements or the land that they were on was developed, but there are a few that still remain (like this Corona Satellite Calibration Target) as a mysterious reminder of the Cold War and the government's secrecy.


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