Old soldiers say, "you never hear the bullet that gets you"... On 8/7/07, Patrick Wiggins <paw@wirelessbeehive.com> wrote:
On 07 Aug 2007, at 18:25, Julie Chorley wrote:
How easy would it be to spot an asteroid of, say, 600 meters five years out?
The idea is to spot them during a pass that brings them close enough to measure their orbit. From those data its position is plotted well into the future. If those calculations show it poses no danger, followup observations are a low priority. But if there's a chance it may cause trouble a very close eye is kept on it to further refine knowledge of the orbit.
With luck the first hints of possible danger will come many years and several passes near Earth before it poses a real threat. With that kind of time only a relatively small amount of push is required to steer it clear of an impact with Earth.