Out Of The Cradle notes a new program to look for errant objects:

When fully operational, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) project will deeply scan most of the night sky several times a month. About three-quarters of the sky are visible from the Hawaiian Islands, and Pan-STARRS will use four linked telescopes connected to its enormous cameras to take broad pictures of unprecedented detail. Objects as dim as 24th magnitude—250 times fainter than objects detected by the current champ in asteroid spotting LINEAR—will pop out of the background and be analyzed for their threat potential.

Now, if we can just get some funding for some creative thinking about what to do about them when we find them (and stop listening to the people at Livermore who've never seen a problem that can't be solved with a nuke). Particularly ideas that allow us to utilize them, as well as avoid them.

You mean there *are* problems that can't be solved with a nuke? :)

This survey will also be very useful for discovering large numbers of Edgeworth-Kuiper Belt Objects, possibly including large (Mars sized or larger) new planets in the outer solar system.

I'd rather see a better program in the CIA to look for errant people out to smack us, frankly.

Rather radical shift in direction there Paul.

Al: yes, but I think it's on topic for this blog. Large planet-sized objects out at that distance may be able to retain some helium in their atmospheres, which could make them very valuable in the future as 3He mines. They may be easier to get to and mine than other sources in the solar system (the moon or Uranus, say, where the problems are either extracting the 3He from very dilute regolith or getting the 3He back up the 20 km/s gravity well to orbit.)

If the true objective is to look for "dangerous space rocks", then it is one of the dumber things to happen recently. If the objective is to do some CIA things that no one can talk about, then using the fear card to get, or cover, the funding is a brilliant stroke.

Would a nuke, even a big one, even be able to exert enough of a Delta-V to change the orbit of a large asteroid? Wouldn't it just blow the target into chunks that would still stay in the same orbit, hitting us anyway, and making a bad massive strike worse with dozens of large strikes wordwide?

Would a nuke, even a big one, even be able to exert enough of a Delta-V to change the orbit of a large asteroid?

There's certainly enough energy there to change the orbit sufficiently to avoid impact. Very small delta-V (1 cm/s or so) can do that, if done far enough in advance. A large nuke would do this by depositing energy from neutrons and gammas in the top meter or so of asteroidal material on one side. This material would be vaporized and ejected, causing the rest of the asteroid to be pushed in the other direction.

Fragmentation of the asteroid would be undesirable, since it would make it harder to keep any pieces from hitting Earth.

I'd rather see a better program in the CIA to look for errant people out to smack us, frankly.
--Phil S

Yeah, that would be good too. It is rather naive to worry about the cost of this program (which I didn't find in the source post) compared to the gargantuan amount of money going to other federal priorities.

The asteriod risk is small, but it is unquestionably real. It would very dumb to NOT spend some money on simple measures like sky surveys to characterize the problem domain and provide a potential early warning.

Consider the recent boxing day tsunami. It was of the scale of destruction of a rather small asteriod impact. There is very little warning for tsunamis. Asteriod impacts can certainly be predicted far in advance, and we may be able to prevent them. Imagine the lives saved.

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The risk of an asteroid impact is not small, in terms of the expected value, because the catastrophic effects would tend to be rather large (even a 100m asteroid would take out a city or cause a substantial tsunami, while a 1 km or bigger asteroid would likely destroy civilization).

One way to measure the approximate importance of a disaster is the odds that a person will be killed as a result of such a disaster. Asteroid impacts have an estimated 1 in 7500 chance of killing an individual, the same as the odds an individual will die in a plane crash. This is primarily because a large asteroid (1 km and up) would likely kill at least a billion people. So even though it's an event that's unlikely to occur in any particular year, its magnitude makes it an equally important disaster to a plane crash.

Fortunately, detection is really the key, as there a large number of ways to impart sufficient delta-V to an asteroid to deflect if the threat is detected early enough. An asteroid one or two months out might require a succession of nuclear blasts, while an asteroid decades out could potentially be deflected merely by changing its albedo on one side with either graphite dust or aluminum dust (the differential absorption of sunlight can slowly provide sufficient delta-V in those circumstances).

Suppose we found an object early enough and had the means of giving it a nudge. Might the material in it be of enough value to use the moon as a catchers mit?

You should have linked directly to the original Space.com article instead, rather than a blog with a couple of comments. The original article has more information:

http://www.space.com/businesstechnology/051221_pan-starrs.html

However... what the original article fails to mention is that Pan-STARRS is significantly funded by the USAF. What interest would the Air Force have in a large field of view telescope, hmmmmmm?

Same reason they've had since the 50's, I'd guess - getting hi-res looks at other people's orbiting toys. I seem to recall that most of the instruments currently looking for NEO's were acquired as surplus from the USAF when they moved on to bigger and better. Looks like they're trading up again.

I don't think the relevant attribute was high resolution, but rather very wide field of view. The USAAF had satellite tracking cameras (Baker-Nunn, I think they were called) with very low F numbers). The optics were based on Schmidt telescopes which stay in focus over large fields of view due to the use of a spherical mirror (spherical aberration being corrected by a specially shaped lens on the front of the camera).