Not too long ago there was this diplomatic incident in my country where the US military forgot to mention they where bringing (or tried to smuggle in) a briefcase with some GPS equipment and other stuff. They where discovered when their plane was inspected and the briefcase was not in their customs declaration.
They where forced to open the briefcase, which was less than 1 meter (3 feet) wide. They agreed only if the briefcase was opened under a roof, alluding it was standard procedure because of spy satellites looking at its content.
That was when I realised that spy satellites currently have ridiculous amounts of optical resolution I had never though equipment could achieve in orbit.
They can't. The diffraction limit of a 2.4m (HST/KH) mirror from their orbit is around 6cm, the practical limit with an atmosphere is around 10cm.
However the photo-recon interpreter guys are amazing. They can look at a 1m resolution image of a vehicle made up of half-a-dozen blurred pixels and say "that's the new mkII whatever - you can see the extended wheelbase from the length of the shadow"
Can't they be using bigger telescopes? The James Webb Space Telescope is declassified technology and has a self-assembling 6.5m mirror.
I'm not sure how atmosphere is optically taken into the equation, but maybe having a mathematical model of it can be used to increase the 10cm practical limit... sort of like with heat shimmer binoculars.
You could use a bigger mirror, although a 6.5m mirror in low earth orbit is going to have a very short lifetime due to drag. The atmosphere has much less optical effect looking down, simply because all the phase tilts are close to the target and so don't have much angular effect. It's like laying frosted glass on top of a document and looking at - compared to putting the frosted glass upto your eye and looking at a distant object.
Really there is a limited return from higher and higher resolution imaging. Once you have vehicles, roads, missile batteries etc spotted there isn't much point being able to see which of the operators are bald.
With modern wars photo-recon is even more limited, you could have mm accurate imaging from a drone of an Afghan tribesman but it wouldn't tell you what he thinks of your politics.
Most of the ones I knew were from WWII. There was rather less need to 'sex-up' dossiers on the capabilities of Rommel's army.
They explained how you could detect barbed wire in photos with >feet resolution by the patterns of wear animals left on the ground near it, or find underwater tank traps on Normandy beaches by the change in the wave patterns
You can improve things a little by flying in an elliptical orbit. Some of the KH8s have listed orbits with perigees as low as 125km -- but they're not that low for the whole orbit. They also didn't have particularly long mission durations (weeks, not years) and may have used their attached Agena stages for some reboosting. Still impressive, though!
They where forced to open the briefcase, which was less than 1 meter (3 feet) wide. They agreed only if the briefcase was opened under a roof, alluding it was standard procedure because of spy satellites looking at its content.
That was when I realised that spy satellites currently have ridiculous amounts of optical resolution I had never though equipment could achieve in orbit.