posted on Sep, 17 2015 @ 06:14 PM
a reply to: CranialSponge
The larger asteroids (over 1/2 mile wide) are much easier to spot (those that are in NEOs) than those which are much smaller (say only a football
field wide or smaller).
Comet hunters, using only their own backyard telescopes were able to find small (only a mile or 2 wide) comets, while still very far out and no tails,
decades ago, and still do today, with even more accuracy.
It's not hard to image large sections of the sky over several nights, and then "blink" those images to catch motion of even very small objects that
are only 1/2 mile wide, but close enough (NEOs) to detect via digital imaging.
Better yet: computer software now helps detect that too.
So, given enough time, it is possible to map out most of what are NEOs. After a while, your images of the sky and scanning for movement will start
showing the same things over with (already discovered asteroids), and by knowing that, you're able to work out a model of the density of them.
That in turn gives you a percentage of what has been found.
I'm not really worried about any ELE sneaking up on us in the form of a asteroid big enough to cause that.
I'd be more worried about the tiny ones the size of a large truck, that if they get low enough can explode and level an entire city.
Again: those tiny ones won't end the world. But they certainly would make for a bad day.