Can someone explain to my dumbass how they helped calibrate the photos or satellites?
Think of it as an eye chart for satellites.
These were film cameras, so the computer on board can't look through the camera and see if the objects are in focus, can they?
However, a sharply focused image has more high-frequency components than a poorly focused one, so some sort of frequency discriminator (a technology from the 1920's IIRC) could possibly suffice to check and adjust focus. Remember that we've had sophisticated servomechanisms since WW2 so the feedback theory to do this was already well known.
But that's just a guess...