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by aw3c2 3355 days ago
Some links for you:

https://space.stackexchange.com/questions/3868/is-photograph...

http://boards.straightdope.com/sdmb/showthread.php?t=627617

https://everything2.com/title/Spy+satellites+can%2527t+read+...

A perfect 2.4-meter mirror observing in the visual (500 nm) would have a diffraction limited resolution of around 0.05 arcsec, which from an orbital altitude of 250 km would correspond to a ground sample distance of 0.05 m. Operational resolution should be worse due to effects of the atmospheric turbulence.

https://en.wikipedia.org/wiki/KH-11_Kennen