I wonder if a better technical system would be to mount some sensors on top of a mast. Use a gimballing camera to detect objects moving in a straight line thro

I wonder if a better technical system would be to mount some sensors on top of a mast. Use a gimballing camera to detect objects moving in a straight line through the air. Use microphones to detect engine noise and trilaterate the position. If the system detects something anomalous send a photo to a human to verify. If you placed a tower every half a mile along the eastern seaboard you would need ~2500 towers. A $2.7 billion budget would allow $1 million per tower.