Corona was the code name for America’s first spy satellite program, started in the 1950s. The optics for these satellites needed to be tested to verify sharpness, but how do you test the massive chunk of glass you just hurled into space? You use it to take pictures of a known reference object, in this case 272 of these concrete Maltese crosses each laid out about a mile apart in a 16x16 mile grid near Casa Grande, Arizona. By the 1970s the markers were no longer accurate due to land subsistence from groundwater extraction and so they sit today, abandoned. 🎵: Supermen by @jacob2dash2