Early Warning against "Killer"-Asteroids - current state, ideas..

Oberst Villa

Here I would like to discuss any current or future early warning system against "Killer"-Asteroids, i.e. asteroids that might cause major damage to earth.

My main interest is not so much in asteroids like Apophis that are currently known, but rather in the detection of those asteroids that might attack us "out of the blue". That is asteroids, against which our current technology might only give us a warning of a few days before impact. I would be interested to hear about currently operational systems, their efficiency and their shortcomings. But also in novel ideas from you how such a system might be designed.

I would suggest to limit this thread to the "sensor" aspect of the problem. I.e. detection, tracking, estimation of the impact site etc. For the discussion of how such an asteroid might be destroyed (or deflected in such a way that it would no longer pose a threat), there already exists another thread:

http://www.physicsforums.com/showthread.php?t=129368

cesiumfrog

This is really the reason we need to focus toward starting to get colonies beyond one planet: to lower the constant risk of our total obliteration.

Consider for example that if a rogue black hole is shooting toward our solar system on such a trajectory so as not to be in our line of sight from a visible star, the only way to detect it would be to look for the Einstein ring reflection after pointing an immensely powerful light directly at it (there's a paper that discusses this..); in practice there is just no way to guarantee any warning (let alone protection).

Nabeshin

A rogue black hole?! You're worried that we're going to get gobbled up by a black hole? Even if we found one there's nothing we could do, lol. Asteroids and comets pose an astronomically larger threat.

Oberst Villa

on a very large timescale, I agree with you.

however, at the moment I am not even concerned with events that might happen in 2036 like Apophis, when there is (at least theoretically) a chance that we might receive a suprise knock-out blow during the next week ! in these events I am most interested in, are there any options to get an earlier warning for those ?

This is the kind of stuff Im talking about:
http://www.newscientist.com/article/...lind-spot.html

LURCH

The biggest threat, as I perceive it, is the rock that comes "out of the Sun." More than once in recent memory, I can recall finding out about a good-sized rock passing very close by the Earth and not being seen untill ti had gone by. This happened because would have had to be looking almost directly at the Sun to see it, and we were looking at the dark side of the rock. We didn't see it untill it went passed and we could see the side on which the Sun was shining. Perhaps some of the unmanned science facilities being stationed on Mars could be equipped with telescopes so that, at least when Mars is in opposition to Earth, we can get a look out into space from the other side of the Sun.

Oberst Villa

I agree with your perception. an asteroid that we did not even notice until AFTER it passed us is quite frightening. I also agree that the best solution to the "out of the sun" problem would be to put the telescope in some other place than earth, though I have to admit that I had not thought of mars yet.

Nabeshin

Why limit yourself to planets anyways? You can engineer your own orbit for a space telescope such that it optimizes the ability to see asteroids heading towards the Earth from the direction of the sun. Not to mention there would be many less problems with weather, rotation, etc.

cesiumfrog

I wonder if anyone has done those figures: are we more likely to be hit by a rare asteroid that we couldn't see because of our blind spot, or by a common asteroid that we just failed to notice due to the mundane difficulty?

Oberst Villa

I agree. does anybody have an idea for a good orbit ?

Oberst Villa

perhaps as a first step to answer this question it would be useful to investigate what these "mundane difficulties" are:

"Technology has now advanced to a level where humans are capable to inventory the NEO population. Given the catastrophic consequences of a collision with a large object, the NEO Observations Program (NEOO) is a result of a 1998 congressional directive to NASA to begin a program to identify 1 kilometer or larger objects to around 90 percent confidence level or better." (source: http://en.wikipedia.org/wiki/Catalina_Sky_Survey )

so could you say that this is the current limit of our technology (1km objects with 90% confidence) or can we do better now, 10 years later ?

ray b

are asteroids the biggest danger or comets a bigger threat
do most asteroids move in a common direction like the planets do
or are there many retro orbiting asteroids as earths speed PLUS the asteroids
if coming nearly head on sure would be a bigger bang with less lead time to act

so how many near earth crossing asteroids are there,
that we know of vs new unexpected ones that fall in to the inner system
vs comets that can just pop in the the inner system at random from deep space
and do not the comets have a bigger speed and more random direction too

I would guess comets are easier to spot but would be harder to divert

Nabeshin

Comets surely would be much easier to spot as, by they're being a comet, they get easier to spot as they get closer to the earth (and the sun). Not sure about this one, but I think comets would be less destructive too. Correct me someone who knows more about these matters, but the Tunguska event makes me think that given equal sized comets and asteroids, the asteroids will cause more damage.

ray b

there are far more comets and they have far higher speeds
when near earth
and speed is the real killer
and they are bigger on avg then the avg earth crossing asteroids
only plus on comets is you can see them coming easier

Tunguska was a small comet as nobody saw it coming or maybe a very small rocky asteroid, as some resent reports think a small rocky
asteroid [under 200 m ] will blow up before impact depending on speed and angle it comes in at

LURCH

Although comets have far greater speeds, there are far fewer of them that cross our path, or come close enough to need watching.

Also, now that I think of it, an observatory on (or orbiting) Mars could look at the far side of the Sun any time that Earth and Mars were not in perfect alignment. Still, spotting an asteroid on its final approach would be of very little use. What we need to do (and what the NEOO was appointed to do) is spot them several orbtis before the one that intersects with us. So maybe what we are doing is all we can do, realistically. We record all the NEO's we can see, and calculate their paths on future robits to see if there is some point in the future when they might come too close for comfort.

Oberst Villa

I agree that early detection and tracking is the preferable solution. Still, a "layered defense" might be useful: just in case we missed to detect one of them and this one happens to come straight towards us, we should be able to finally detect it before impact.

And I do not think that late detection would be of a very little use. Even if we had no option of any active measures (a big fat nuke might be such an option, but this would be a topic for the other thread I linked in my first post), any kind of public warning might limit casualties. Even if it was only hours before impact (in this case we should have a good idea on which place on earth the thing will impact). Of course, the public would have to be educated before, how to behave in such a case - has anybody seen this "Duck and Cover" movie with that stupid turtle ?

Nabeshin

Haha! yes! I can only imagine the government making another one of those except instead of atomic bombs.. there's asteroids falling out of the sky. However, implementing any kind of early warning system would require education and in my opinion in educating people they would get an even larger sense of fear than they already have. Especially if we said things like "The majority of these asteroids we don't even know about! Heck, most of them fly by before we even knew they were coming!" I'm not one to promote ignorance, but when people start hearing about possible asteroid impacts, they tend to get antsy.

ray b

so how many new untracked asteroids in a near earth orbit do they find each year ?
and we would have found most of them by now
do both asteroids and comets stay close to the plain of the ecliptic and move in common
direction or can we get them from any angle

I would have guessed that there are more comets esp new un-tracked ones
that pop in on avg as they tend to have longer orbits and there are more of them out there in deep space


to spot ether a hubble like scope maybe with a super wide lens
in orbit on the opposite side of the sun from earth
should work and need less boost to get there then sending it out near mars
where it would not stay in an idea spot to see objects we can't see from earth

any way a top mission should be to locate and track all the close asteroids that could hit us
would radar work better then a light scope to do that??