michaelwbusch

Let's keep on doing them, then.

Thank you all for taking the time to do this. It's not exactly one of our usual ways of doing outreach, is it? - Michael Busch

Some additional information for the audience, Paul: We are doing radar and well as infrared and optical observations of potential retrieval targets, so that we know their orbits well enough to retrieve them and so that we have more precise size, shape, and spin state estimates.

Dawn's ion propulsion system has put the spacecraft through more velocity change (delta-v in spacecraft jargon) than the engines of any other deep-space spacecraft. Dawn can go through something over 10 km/s of delta-v.

Edit: And I see John answered faster and better than I did.

Adding on to Paul's answer: As we get better information on an object's trajectory trajectory, the uncertainty region at a given time in the future shrinks. This either confirms a potential impact, or - thousands of times more likely - puts the Earth entirely outside of the allowed space and rules the potential impact out.