https://geo-matching.com/content/new-approach-to-use-ground-...
Outside the atmosphere you would not be able to do it
Yes, SAR [1].
[1] https://www.earthdata.nasa.gov/learn/backgrounders/what-is-s...
The Space Shuttle flew missions with an imaging radar that discovered ancient riverbeds beneath deep sand in the Sahara. At the time, some thought it would have worked equally well to disclose buried military infrastructure.
https://www.jpl.nasa.gov/missions/shuttle-imaging-radar-a-si...
Now compare that challenge to simply setting up a shell company and purchasing 15-30cm commercial satellite imagery in their choice of bands.
Commercial satellites can generate 15-30cm images good enough to tell what make and model a car is in a parking lot. https://blog.maxar.com/earth-intelligence/2020/introducing-1...
Camera gimbals provide image stability regardless of motion in 3D space. Digital post processing is used to clean up images from planes and other moving sources.
> with the weight restrictions of a high altitude balloon.
People seem to really underestimate the size of these balloons. They are hundreds of feet across and capable of lifting massive loads. Using Google's Loon as an example it had a balloon that weighed almost 200 pounds and carried an additional 175 pounds of solar panels before you even added the mission payload.
> compare that challenge to simply setting up a shell company and purchasing 15-30cm commercial satellite imagery
Satellites have predictable passes and military installations schedule sensitive outdoor activities around them. The problem for defenders with balloons is that they can loiter on station for months at a time making scheduling around them impractical.
It is a lot easier to take pictures and collect data at 60,000 ft (balloon) than from a satellite in low earth orbit, which is closer to 6,000,000 ft.