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by throwanem
1552 days ago
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Are we sure there's no overlap between the range of impactors susceptible to occlusion and the range of impactors capable of producing a disaster if they strike a populated area? (Granted it's multiplying small probabilities, but so is this whole discussion, so I don't feel too bad about it.) |
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Yes. The key point is that the larger the object, the further away we can see it. And the further away we can see it, the more time we have between the initial sighting and any possible collision with Earth.
The lower bound for a "potentially hazardous object", i.e., one that could cause disastrous damage in a collision, is 140 meters wide, and we can see those far enough away that they are years to decades from getting close to Earth (i.e, time enough to plan a space mission to deflect them enough to miss Earth). Newer surveys are getting to the point where they can detect 10 meter wide objects, which can still cause substantial damage (similar to, say, a hurricane or a tornado), far enough away that they are days to weeks from getting close to Earth (i.e., more than enough time to evacuate possible impact areas if needed).
Even if such an object were temporarily occluded by a low Earth orbit satellite, the occlusion would only last for minutes at most (because the satellite and the distant object are moving across the sky at very different rates). So for objects of the above sizes, occlusion doesn't prevent us from seeing them well in advance.
See here for more info:
https://en.wikipedia.org/wiki/Spaceguard