Corona Satellite Calibration Targets

The Corona Satellite Calibration Targets consist of 272 concrete calibration markers embedded into the Earth's surface in and around Casa Grande, Arizona, United States. The purpose of the markers is disputed. The markers are commonly believed to have been used to aid camera calibration for the US Central Intelligence Agency's Corona spy satellite program, though they may have been used as references for aerial surveys through photogrammetry. The markers formed a square 16-by-16-mile grid, and were maintained from 1959 to 1972. Some of the original markers can still be found on satellite maps and ground inspection. See links to maps below.

Following 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. Working with the Arizona Real Estate Office, the US Army Map Service was directed to lease land for office space in Casa Grande, Arizona. Land was leased in 100-by-100-foot parcels, with access to a road. Large concrete Maltese crosses in the ground, each 60 feet in width, were in place by 1967. The crosses were arranged in a 16-by-16-mile grid.

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