Naked eye has angular resolution of 30m at 100km, you need something slightly better. A small lense should do it. Cameras + zoom lens are well understood mass produced components. And this is a highly parallelizable task.
It works only if it fly above your territory—and similar systems are used for drones detection now. Actually, they use people eyes and smartphones and instant messaging. But during recent attack on Iran a single F35 flied over Iraq and fired a missile from like 200 km distance on a target in Iran.
Also, radars are good in pinpointing exact coordinates in space and time. Optical recognition may have delays or difficultly in measuring distance. Even 1 second delay makes their information useless for supersonic aircrafts.
Why would you need large telescopes?
Naked eye has angular resolution of 30m at 100km, you need something slightly better. A small lense should do it. Cameras + zoom lens are well understood mass produced components. And this is a highly parallelizable task.
Note you don’t even need high resolution in all directions, just high enough to see whether it’s worth zooming in/switching to a better camera.
Did you ever see any plane that far? I saw only planes above me (10 km) and they are almost like dots.
The difference between optics and radar is that with optics you need to know where to look—but the radar has constant 360 perception.
But I discussed that in the post. All you need are enough cameras + processing power. Both are cheap.
It works only if it fly above your territory—and similar systems are used for drones detection now. Actually, they use people eyes and smartphones and instant messaging. But during recent attack on Iran a single F35 flied over Iraq and fired a missile from like 200 km distance on a target in Iran.
Also, radars are good in pinpointing exact coordinates in space and time. Optical recognition may have delays or difficultly in measuring distance. Even 1 second delay makes their information useless for supersonic aircrafts.