No. Before the 120 goes active; if your radar losses track of the target, the missile is useless, and there are many ways to loss track of your target. TWS works by comparing target parameters of successive scan instead of maintaining a constant bean on the target. By comparing target parameters from multiple returns of different scans. The radar is able to tell return x of this scan is from the same object as return y of the last scan. So the radar can kind of "lock" on to the target. If the parameters of the return is different enough, the radar can be fooled into thinking it is a different object, and that is one way you can loss track of a target. As what parameters do radars used for their heuristic target designation, they are clasify, and diferent manufacturer and different countries have their own tricks.