CASA GRANDE, Ariz. (KSAZ) - For more than three decades, the over 100 concrete crosses located just southwest of Casa Grande remained a mystery.
There were many questions, including how the crosses got there, as well as their purpose. As it turns out, they were all part of a top-secret program used to to spy on the Soviet Union, during the height of the Cold War.
People often came upon the crosses out in the desert, roughly 30 feet long, and didn't really think much of them. From the ground, thy also don't look like much, perhaps an abandoned construction project. From the air, they look like targets.
"So the targets themselves are these concrete kind of 'petals'," said Cold War historian Chuck Penson. "They're about 50 feet across, and they're oriented to the cardinal point."
Penson first heard about the targets when a pilot friend of his noticed them while flying over Casa Grande.
"She was out joyriding over this general area in the desert one afternoon, and saw these peculiar things on the ground," said Penson. "I went up on a flight with her, and sure enough, there they were. They looked like Maltese Crosses on the ground."
At one point, there were more than 270 of them dotting Pinal County.
"A huge grid of these, not only the ones we saw, but a huge grid, about 17 square miles," said Penson.
Penson and his friend did some research,c ontacting the Army Corps of Engineers after noticing an emblem in the center point of the target. After months of waiting, they finally got their answer.
"And it turns out that they are essentially calibration targets for our early spy satellites," said Penson. "Kind of an eye chart to make sure the cameras can be calibrated and understand what kind of field of view they're seeing, and how small an object they can resolve."
The Corona spy satellite program began in 1959. The cameras would check their focus using the targets in the Arizona desert, in an effort to make sure they got the clearest pictures possible at the time.
"And they were placed in Arizona because, as you know, it's always sunny in Arizona, and they knew they would almost always be able to see the targets, no matter what stage of the program they were in, or what time of year they were flying," said Penson.
The technology, high-tech for its time, and relied on a complicated process to get the images of the Soviet Union from space back to the United States to be analyzed.
"They were actually taking pictures on film -- 70mm film -- and the film would be ejected in the nose cone of the satellite, then plummet back to Earth," said Penson. "A parachute deploys, and they're actually snagged out midair by a specially equipped aircraft."
These nondescript remnants of the Cold War were abandoned in 1972, but Penson says they serve as a concrete reminder of just how tense the decades were.
The crosses may have been abandoned, but they were hidden in plain sight, for decades.
"It was only declassified in the mid 90's," said Penson. "Prior to that, it was all still hush hush, top secret."
Now that word has gotten out about these Cold War relics, they've become a popular destination for people all across the country who want to come check them out for themselves.