Here's an idea that popped into my head a few years ago whilst having an on-line discussion with someone who worked for an agency involved tracking space debris by radar. And it won't go away. I don't know enough about orbital mechanics, nor have a sufficient appreciation of the forces and velocities involved, to dimiss it. So, if anyone can shoot it down, please do and I can give my brain a rest.

My assumption is that for any given piece of debris currently in a long term orbit, it would only take a small (earthwards) delta change in its instantaneous trajectory to cause it to fall back to earth of its own accord. And, for the vast majority of those small objects, that would be a safe method of displosal. Also, that a near-but-not-quite parallel collision between a piece of debris and a solid flat surface, is likely to redirect the debris, rather than for it to penetrate. Like a bulllet ricocheting off a wall.

In the next couple of years the shuttles are due to be stood down on safety grounds. It long struck me that the biggest risks are associate with launch and return with people on board. And the biggest limitations on individual missions is the support needs for that wet ware. As a final act, one or more of the shuttles could be sent into orbit, perhaps to dock with the space station unmanned, or with a skeleton crew to be returned by other means.

If it took up extra fuel (in the bay) for manovering; the robot arm; and a large solid deflector. It could use that deflector, extended below the shuttles orbit to change the orbits of small pieces of debris (the vast majority of the 9000 or so they track), just enough to cause them to re-enter and burn up.

'scuse the crudity of the ascii art (its obviously not to scale :):

          ____
        >[____]>
           /
          /
         /
         \
          \
           \            ____----
            \   ____----
        ____----  .  .  .  .  .  .  .  
____----        .
             .
          .
       .          Earth V this way
    .                   V
 .                      V
[download]

So, shoot it down--but no missiles please :)