. . . and just in case you wanted some hard facts/examples of real satellite targeting calibration work, here's a very good research report on the calibration of the BiLSAT earth observing satellite from a couple of years ago. The team used a specially prepared combined flat field/contoured test site set up by the University of Nevada ground team at a location near Railroad Valley, Nevada.
You think Nikonian Len Sheppard is insistently critical about AF test targets commented in various threads here? Forget about it - he's a kitten compared to the BiLSAT team members who went nearly out of their minds trying to calibrate their earth imaging orbital devices. Weeks and weeks of very difficult work.