Corona Satellite Calibration Targets, Photogrammetric test range in Casa Grande, Arizona, US.

The Corona Satellite Calibration Targets are a grid of white concrete Maltese crosses spread across the desert landscape near Casa Grande. Each cross was designed as a reference marker for aerial photography and precise ground verification.

In 1959 the US Army Map Service began leasing 100-by-100-foot parcels in and around Casa Grande, working with the Arizona Real Estate Office under the Controlled Range Network. Concrete Maltese crosses, each 60 feet wide, were in place by 1967, arranged in a 16-by-16-mile grid to calibrate aerial photography equipment for aircraft. The program ended in 1972, and by the late 1970s subsidence from groundwater extraction made the targets obsolete.

The concrete crosses represent how Americans developed new ways to map and monitor land from the air during a time of global tension. These markers show the importance that precision mapping held for military planning and defense strategies of that era.

The two surviving crosses named in the sources sit at the southeast corner of South Montgomery and West Cornman Roads, and at the northeast corner of West Cornman Road and Carmel Boulevard. Both are roadside parcels in flat farmland, so they can be checked on foot from the shoulder; the concrete is weathered and partly buried, so look for the cross arms at ground level rather than a standing monument.

The crosses are often said to have calibrated Corona spy satellites, but the Corona program used a different "tri-bar" pattern; these Maltese crosses served aerial photography for aircraft. The Army Map Service leased 100-by-100-foot parcels with road access from the Arizona Real Estate Office, and by 1967 the crosses were in place.