By the late-1970s, the US Army Map Service considered the targets to be obsolete for their use as the land on which they were situated had subsided because of groundwater extraction. The majority of the targets were abandoned when the program ended in 1972. According to Gary Morgan, member of the Cold War Museum in Warrenton, Virginia, the six pieces of rebar, which protrude at an equal distance from each other, may have been used to hold a laser designator to provide the Corona satellites a more accurate fix on each target. Įach of the targets has a manhole on the west arm of the cross, the manhole has a cement cover and steel reinforcement bars. The Corona satellite program used a different 'tri-bar' calibration pattern. The cross-shaped patterns were used to calibrate aerial photography equipment for aircraft. The crosses were arranged in a 16-by-16-mile (26 by 26 km) grid. Large concrete Maltese crosses in the ground, each 60 feet (18 m) in width, were in place by 1967. Land was leased in 100-by-100-foot (30 by 30 m) parcels, with access to a road. Working with the Arizona Real Estate Office, the US Army Map Service was directed to lease land for office space in Casa Grande, Arizona. See links to maps below.įollowing the launch of Corona satellites in the 1960s, the US National Foreign Intelligence Program determined that there was a need for calibration under the Controlled Range Network. Some of the original markers can still be found on satellite maps and ground inspection.

The markers formed a square 16-by-16-mile (26 by 26 km) grid, and were maintained from 1959 to 1972. The markers are commonly (and erroneously) believed to have been used to aid camera calibration for the US Central Intelligence Agency's Corona spy satellite program in fact, they were used as references for aerial surveys through photogrammetry. The range consisted of consist of 272 concrete calibration markers embedded into the Earth's surface in and around Casa Grande, Arizona, United States. The Casa Grande Photogrammetric Test Range is a test range established in the mid-1960s to test the dynamic performance of aerial survey cameras. Target dimensions of the Casa Grande Test Range crosses

Google maps satellite