Well, if they are detected early enough, you don't need much to deflect them. Think of a large sheet of mylar... solar wind and light pressure... attached weeks in advance. Micro-newtons are enough; slow it down and let the earth's orbital speed widen the gap. Of course, you need to put a few dedicated telescopes or SAT's up to catalog and calculate the orbits. Oh yeah, and all orbits change constantly when they interact with other orbits. So any static model you think of is not valid today. But we need eyes in the sky. I think one is going up in a few years, but we have been able to do this since the 1970s, at least. for sure in the 80's. It seems like an awful risk with the tons of Starlink and spy satellites we send up. Governments are too greedy to launch three or four payloads that could save humanity.