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How We Knew AL00667 Would Miss Earth
jefu writes "In January there seems to have been an incident in which it was thought that an object (asteroid) in space might have hit the earth within a couple of days of being spotted. It did miss, though. This story (from NASA/Ames) talks about the discovery of the object and the process that astronomers went through to determine if the asteroid was or was not a threat."
Most all missle defense proposals depend on punching a hole in an ICBM by heating it. For all their destructive potential, ICBMs are 90% thin skinned gas tank. You could take one out with a grenade, if you could somehow get it there.
The power required to destroy any rock big enough to survive atmospheric entry would be orders of magnitude greater.
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
Short Warning Times
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Article Posted: February 19, 2004
By: David Morrison
For the story of AL00667, which briefly masqueraded as an asteroid that would hit the Earth within two days of its discovery, read on.
February 19, 2004 Short Warning Times
Following is information on the small asteroid known last January 13-14 as AL00667. A preliminary analysis of the discovery data for this object yielded a possible impact with Earth in less than 2 days time -- a situation not encountered previously in the Spaceguard Program. Although we knew at the time that such a prediction of imminent impact was improbable, a collision could not be ruled out. And if a possibility of an impact in 2 days existed, what should we do about notifying governments or the public? The story of this situation on January 13, 2004, is included as part of a paper by Clark Chapman (Southwest Research Institute) presented on February 22 at the Planetary Defense conference of the AIAA (American Institute of Aeronautics and Astronautics). Several paragraphs taken from this paper are reproduced below. Following these quotes from Chapman's paper are additional quotes from a letter Brian Marsden (Minor Planet Center) wrote to CCNet on 14 January on the same subject. Finally, there is a statement posted on the website of the IAU (International Astronomical Union) discussing what lessons we should draw from the story of AL00667, and how such a situation might be better handled in the future.
Asteroids never cease to surprise us. We may never encounter a situation just like this again, but we are fairly sure to have other crises as the rate of discovery of NEAs continues to increase.
David Morrison
FROM CLARK CHAPMAN'S AIAA PAPER "NEO IMPACT SCENARIOS"
presented February 22, 2004
"Just last month (January 2004) perhaps the most surprising impact prediction ever came and went, this time out of the view of the round-the-clock news media. It illustrates how an impact prediction came very close to having major repercussions, even though -- with hindsight -- nothing was ever, in reality, threatening to impact. It is a story of success in that the impact prediction was nullified in record time, less than half-a-day, but the success was accomplished through a set of ad hoc, unofficial, and often unfunded activities and relationships, although assisted in major ways by the official infrastructure, such as it exists (the LINEAR Project, the IAU Minor Planet Center, and the NASA NEO Program Office).
"About 36 hours before President Bush's planned speech at NASA Headquarters on future American space policy, the Lincoln Near Earth Asteroid Research (LINEAR) observatories in New Mexico routinely recorded four images of a moving object. Half a day later, on Tuesday, January 13th, these data were sent (as part of the daily submission of data) to the Minor Planet Center in Cambridge, Massachusetts. Just before going to dinner, MPC research Tim Spahr ran the data through standard software to generate a nominal ephemeris for the new object. These are posted on the publicly accessible NEO Confirmation Page (NEOCP) so that amateur and professional asteroid astronomers around the world might be able to follow up on the LINEAR observations that night. It is through such follow-up astrometry that NEO orbits can be refined so that the object is not permanently lost. Spahr posted the ephemeris, based on LINEAR's four detections, on the NEOCP under the designation AL00667, along with ephemerides for several other recommended targets. Less than an hour later, a European amateur astronomer, Reiner Stoss, went to the NEOCP and noticed a curiosity: AL00667 was predicted to get 40 times brighter during just the next day, meaning that it was going to be six times closer to the Earth! He expressed his amazement on Yahoo's MPML (Minor Planet Mailing List) chatroom on the internet.
"Professional asteroid researcher Alan Harris happened to be monitoring the chatroom and noticed the strange
try this link for more info http://www.hohmanntransfer.com/mn/0402/09.htm
That's about the size of the Tunguska object (probably a comet, since it exploded in mid-air and didn't leave a crater). Enough to make a mess of a big city or a pretty impressive tsunami, but not enough to wipe out mankind.
When I am king, you will be first against the wall.
Here's an animation of the object. The link to the yahoo egroup discussion is also worth looking at. The discussion morphs from everyone thinking it's a joke post to realizing that the asteroid exists. It's an interesting log of people coping with uncertainty.
Consider it proven (residue left behind as a layer in the soil etc - if you google you'll find quite a lot)
Recent theories suggest the whole solar system moving like a sinus curve up and down through a "cloud" of more-than-usual-objects in the galaxy, and thus every ~30M years or whatever it was there's an increased risk. Several of the almost-everything-killed things that has happened to the earth could be explained this way.
(source: Some issue of Scientific American)
it's in my head
The current best missle defense, the AirBorne Laser (think 747 with a bad attitude) carries a massive chemical laser that takes a couple of seconds to destroy missles. It's mostly designed for theatre of war (intracontinental) missles, and is still in the testing phases.
How would an electron gun produce any significant kinetic change in the rock? Alternately, you could boil off part of the asteroid and "jet" is to the side, but the energy this would require, if it's only a few days out, would be enormous. you'd need to hit it years out to have any hope of significantly changing it's trajectory.
Even IF we had a point defense mechanism... unless we vaporize the rock, or reduce it to very small (inches) pieces, we'll have just created an intergalactic shotgun...
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
If it's got an impact velocity of 30,000 meters per second (not out of the question), it wouldn't be in the atmosphere for any more than a second or two. Even if it does "blow apart", the heat transfer into the atmosphere isn't going to be insignificant.
>what are requirements for such a rock to survive its way through atmosphere
High density and low total surface area
Actually that could be a really bad idea, the majority of asteroids threatening Earth are probably not solid bodies - more like aggregations of rubble. A blast could smash such bodies to rubble (all of which would still be heading our way). Many bodies have a composition similar to foam - very fragile with lots of pores and spaces filled with volatiles. When hit by a blast, a small amount is vaporised, the remainder just soaks up the explosion - and keeps on coming.
There are several proposals for deflecting asteroids - either attaching a mass driver to produce a small, almost constant thrust. Alternatively a huge solar mirror could be put on to a trjectory close to the asteroid. It would focus the light of the Sun on to one point on the asteroid - vaporising material into space and creating a thrust.
Sadly both approaches need us to have plenty of warning. The accelerations produced are so small (in the orders of cms^2) that you need plenty of time to get a sizeable deflection.
Such an observation system could be put in place for a tiny fraction of the cost of Star Wars or NMD and wouldn't cause any international uproar. Sadly it doesn't produce nice fat Pentagon contracts.
There's quite a nice summary of the various technologies here.
Beat wishes,
Mike.
For a great novel about asteroid armageddon and the resulting collapse of society, read "Lucifer's Hammer" by Larry Niven and Jerry Pournelle. It's slow for the first half, but man, once that asteroid hits, it's sweet, sweet chaos.
... before its nearest approach. I remember last year, when an object near-misses Earth (I think it was bigger than our 667 friend). It was really close, in fact at that time, it was the one which was closer, about 120000 km (which didn't hit our planet). I don't remember the code, but that fact (the short distance of the fly-by) will help at finding out.
The problem: It was spotted TWO DAYS AFTER the nearest approach. Some scopes are needed in the southern hemisphere.
Uh, I think he's trying to say that your chances of dying of cancer are 240,000,000 times higher than the big one hitting Earth. Don't be so serious, it's funny, laugh.
That would have to be quite a powerful missile to turn that rock into gas before it hits the surface.
If the object is travelling at 10km/s (which is first gear for interstellar speed), then the missile would have to be able detonate with somewhere around 3/1000th of a seconds accuracy for the blast to hit. Not to mention it would have to position itself in the exactly right spot.
You also have to consider that anything we can put up there is nothing compared to the blast that the object goes through by simply coming into the atmosphere.
I pretty much slept through thermodynamics, but I can't imagine that all that extra heat being transfered to the atmospehere is a good thing.
Jack Valenti and Orrin Hatch will be first up against the wall when the revolution comes.
GEODSS first came up in 1982. It consisted of four sites (three today, budget cuts) worldwide, each with three 1-meter telescopes. The whole system is computer-run and reports to NORAD automatically. This was the beginning of automated astronomy.
The telescopes scan the whole sky every night, subtract out everything in the star catalog, and report unknown objects. New satellites and space junk are found this way. Even dark objects that occult stars are noted. There's also a more elaborate USAF site on Maui with even bigger computer-controlled telescopes.
Some of the sites have lasers (Maui definitely does) and can illuminate their targets using one telescope while looking at it with another. This allows time-of-flight ranging, photography of dark objects, and determining whether a satellite has cameras. But illumination is only useful for near earth satellites; it doesn't help with asteroid search.
Asteroid search is a spare-time activity of one of the GEODSS sites. They continue their real job for the USAF, looking for anything near the Earth that shouldn't be there.
The GEODSS hardware was updated in 1999, with better sensors, new computers (the 20 racks of PDP-11 hardware had to go), better positioning accuracy, and some infrared capability for working around cloud cover. The original main optics remain in use.
Your tax dollars at work.
but I can't imagine that all that extra heat being transfered to the atmospehere is a good thing.
This is rather easily estimated.
We can assume most (~95%) of the atmosphere lies in the first 14 kilometers (it's actually 18 km at the equator and 8 km at the poles). Assume Earth is a sphere of radius 6371 km. This gives a total atmospheric volume of 7.16e18 m^3. Assume a conservative average density of 0.8 kg/m^3; the mass is therefore 5.74e18 kg. If that seems overly heavy, consider that the Earth weighs about 5.98e24 kg, or about 1 million times more.
Assume the molecular mass of air is 29.2, and we get 1.96e20 moles. Assume its specific heat is (7/2)R == 29.1 J/K-mol, and we get the heat capacity of the entire atmosphere to be 5.71e21 J/K.
Hiroshima was a 5-kiloton blast, from 35 kg of Uranium. That is, 35 kg U directly converted to energy is like 5000 tons of conventional TNT-like high explosive. Hiroshima translates into 3.15e18 J, which would raise the global temperature by 0.0005 K.
Assume that life will be threatened if the atmospheric temperature rises by more than 2K. Raising the atmospheric temperature by 2K requires 1.14e22 J, which corresponds to 3622 Hiroshima bombs.
The question of whether a given asteroid is 3600 times as powerful as the Hiroshima bomb is left as an exercise to the (astrophysicist / nuclear physicist) reader.
Speaking as an engineer, I'd say that we're probably heating up the atmosphere far quicker all by ourselves, so we probably don't need to worry about asteroids.
Time flies like an arrow. Fruit flies like a banana.