That's... amazing. Then it make sense. How do you calibrate a spy satellite, and test its resolution ? I wonder which engineer came with that solution. His coleagues must have thought "he is crazy".
Another article with some better pictures: http://99percentinvisible.org/article/solve-x-deciphering-calibration-marks-made-classified-spy-missions/
This is Corona Satellite calibration target AJ46. In the 1960s 272 of these concrete markers were laid out in a 16 x 16 mile grid in and around Casa Grande, Arizona to aid in calibrating the optics of our first spy satellites.Instagram.com/p/CNT8Q2GhEjP/
It's fascinating to me that these vestiges of the Cold War still exist, often right alongside modern civilization, if one only knows where to look. I can't imagine living a life in constant fear of total nuclear annihilation, and yet - the threat has never really gone away.
I could not come up with a satisfactory answer why the government would build a fixed optical range with such large targets specifically for CORONA in a post-1966 timeframe and not mention it in documentation anywhere. One website states the targets were calibration targets for CORONA from 1966 until 1972. The targets were supposedly abandoned due to shifting caused by subsidence from nearby ground water pumping. [6] Even Wikipedia has a page about these “Corona Satellite Calibration Targets.” Keen observers will note that while NRO references are listed at the bottom, no specific document is identified with information on either Casa Grande or the concrete cross dimensions. [7]<snip>I found what I believe to be the answer on the front page of the Casa Grande Dispatch (Pinal County Edition), dated May 31, 1967: “CG [Casa Grande] Area to be Subject of Precise Photography.” [12]Walt Wiley’s front-page story tells of a US Army Corps of Engineers effort to create “…an extremely accurate yardstick for dynamic testing of aerial cameras at low and high altitudes.” A follow-up article on October 8, 1968, provides estimated costs and timelines, and a curious statement by Roger Lewis, an aide to Arizona Representative Morris Udall: “I was told the markers would be used for photography testing for aircraft at low or extremely high altitude.” The next sentence is conjecture on the part of Lewis: “[Lewis] added that it was his impression that ‘high altitude’ aircraft would also include satellites.” Lewis’ reason or agenda behind this statement of conjecture is unknown. [13]And to hammer home the linkage to aerial photogrammetry, I found this description from John O. Phillips the Chief of the Geodesy Division, Coast and Geodetic Survey, circa 1966:“The resurvey on the original Phoenix, Arizona, test area was completed early in 1963 with modern electronic distance measuring equipment and triangulation methods, and the results were rigidly adjusted during the reporting period. The resurvey and the adjustment were performed to provide accuracy commensurate with currently used aerial photogrammetric equipment…[C]onsiderable progress has been made on surveys to establish another test range (Casa Grande Test Range) just south of the original Phoenix test area. The Casa Grande was designed to be a superaccurate range for use in dynamic calibration of aerial cameras. When completed, the Casa Grande test range will consist of 273 points positioned horizontally and vertically by precision survey methods. Each point will be elaborately paneled, and all points will be located according to an orderly arrangement within a 16-mile square area.” [19]
<snip>A more interesting mystery would be if the USSR had constructed similar calibration targets, and if these were known to and used by the US to calibrate imagery during overflights. Or even less likely to have any information available: if the USSR were aware the CORONA/aircraft/etc targets within CONUS and used them to calibrate their overflight imagery.
Gobi desert also features some interesting artificial "artsy" ground patterns near "40.457751,93.378481". Any guess what purpose they might have served? Image distortion calibration at Landsat-type ground resolution distance? Test of automatic pattern recognition to create maps, and identify airport runways, etc? Some pre-/post-strike damage assessment simulation? Art installation?edit: USGS maintains a "Test Sites Catalog" of radiometric, geometric, and spatial sites - see
Answer to your first question: yes, at least by 1974 the USSR had their own set(s) of calibration targets, and they were apparently repeatedly observed by the US - see "The HEXAGON Story, page 205 (page 191 in the PDF of the 2011 release)
I have no idea how to search for it on my computers.
QuoteI have no idea how to search for it on my computers.Hello! This is the NK №7, 2001 year, pages 66 - 68. If you write e-mail, i can send to you this number of magazine.
Thank you. Here you go: