>There was also a hot-air balloon program that would persist at stationary at high altitude and track all moving targets over a metropolitan area for up to a mo

>There was also a hot-air balloon program that would persist at stationary at high altitude and track all moving targets over a metropolitan area for up to a month without maintenance. They could do this with a single (bajillion dollar) military radar slung from the bottom of a plane over Iraq 15yr ago. The current tech is probably cheaper and better.