It really is scary how much junk is out there flying around and how little money goes into the search for it. This brings me to a fun little thought experiment proposed by Arthur C. Clarke (I assume he originated the idea, I certainly heard it first from him) you take a nuclear bomb and detonate it in space. The resulting shock wave would spread out in all directions and bounce off any object it encountered. Essentially it is like sonar or radar only with the shock wave of a nuclear bomb. We could then see all the "echoes" and plot the vast majority of the junk in the solar system, especially if we set another one off a few weeks/months later and compared the different positions of objects, thus providing some sense of trajectory.