INCOMING!, Detection and observation of Earth-approaching asteroids. Options

[Paolo]

no sone seems to have noticed this yet

[climber]

Too much info kill the info! Where do we have to look? I've seen something will hit the atmosphere tonigth over Sudan, correct?

[ugordan]

Whoa! Any chance of organizing a crash observing campain from ground or even orbit?

[Holder of the Tw...]

An asteroid... well, really a meteor, is now predicted to hit the atmosphere.

First time I know we have had advanced warning on a single natural object.

MPEC report

Quote: "Steve Chesley (JPL) reports that atmospheric entry will occur on 2008
Oct 07 0246 UTC over northern Sudan."

[charborob]

Any idea how big is this rock?

[Juramike]

The absolute magnitude indicates that the
object will not survive passage through the atmosphere.

Steve Chesley (JPL) reports that atmospheric entry will occur on 2008
Oct 07 0246 UTC over northern Sudan.

Don't sell all your stocks yet, looks like we'll live to see another day....

[imipak]

Is this the first time a fireball's been predicted in advance? I was very interested in meteor observing for a few years and read a lot of stuff (it seems so in retrospect, anyway) but I don't recall ever hearing of an event like this.

For those of us who can't interpret the MPEC data or ephemerides, what does the absolute magnitude mentioned tell us about the size of this object?

[TheChemist]

Hey guys, don't just tear your swimming suits apart.

The link says that it will disintegrate in the atmosphere, as Juramike already pointed in the duplicate thread.

Why do you scare us with no reason ?

THANKS FOR POINTING OUT THE DUPLICATE - BOTH TOPICS NOW MERGED -Admin

You 're welcome !

[Holder of the Tw...]

There have been at least three revisions in the last hour, a lot of people are looking at this object.

Hard to say, but now it looks like it may be a near miss, by about a thousand miles. The latest Mpec
doesn't state whether an impact is still expected.

The absolute magnitude indicates a size of two to seven meters.

Gosh, I just mixed english and metric units in the same post.

Edit: Five meters big at most, more likely two to three. Absolute magnitude of 30.4

[climber]

30.4!!! Gona be visible over the horizont!

[Holder of the Tw...]

Space.com is now reporting the story, and says atmospheric entry is expected.

Link

The report also emphatically states that it will be destroyed at altitude, and doesn't pose a significant danger.

True enough... if it's not a nickle-iron.

[SFJCody]

I wonder if it can be imaged from orbit during entry a la Mars Phoenix? Probably too much uncertainty.

[Shaka]

From TPS:

The meteor is expected to be visible from eastern Africa as an extremely bright fireball traveling rapidly across the sky from northeast to southwest. The object is expected to enter the atmosphere over northern Sudan at a shallow angle.

"We're eager for observations from astronomers near the asteroid's approach path. We really hope that someone will manage to photograph it," said Williams.

Shoot!
My SR71 is in maintenance, or I'd be over there like a shot.

[ngunn]

It may be small and harmless, but for me knowing it is on the way represents a huge psychological milestone. It is a great achievement by those watchers of the skies who search for these objects that the fall of a meteorite need no longer take us by surprise. It feels as though in one more small way we have 'grown up' as a species. If it had been a bit larger and aimed at a suburb near you, you would already have heard when to head for the cellar (and felt quite safe out of doors until a few seconds beforehand).

[SFJCody]

I guess once LSST and PanSTARRS come online we'll get these kind of alerts fairly regularly. I imagine it will change the public perception of 'asteroid impact predicted!' headlines a lot. People will go from thinking of the end of the world to thinking of photo ops + a mad scramble for very valuable rocks.

[Holder of the Tw...]

Man, I've never seen anything quite like this. Twenty observatories have turned in collectively nearly 200 observations of this object, and the Minor Planet Center is issuing updates about every fifteen minutes. This little rock is definitely getting it's share of attention.

A fair number of professional observatories seem to be poised to follow this thing almost into the ground.

[Shaka]

LINKS, man! Give us links, HTL!

[Holder of the Tw...]

Link

Anything with 2008 TC3. Most recent on top.

BTW: "HTL"? Whazzat?

[Juramike]

I guess they won't be seeing it from here (bad luck!): Haboob sandstorm in Sudan

[dmuller]

If this thing is coming in shallow from NE to SW then it should be visible in Alexandria, Cairo, Egyptian tourist destinations, maybe as far down as Khartoum ... so there is some chance to get it on film. If I get my timzones right, it will be night then. Anybody's got a groundtrack?

[volcanopele]

hmm, I think my Celestia copy needs fixing. Using the most up-to-date orbital parameters, I get a miss distance of 5,850 km over North Africa.

[Fran Ontanaya]

The NEO Program lists it as a close approach at 0.02 LD. That's under 8000 km.

http://neo.jpl.nasa.gov/ca/

It was briefly in the Recently Observed list of Impact Risk, with dates beyond 2080, but it isn't anymore.

[Holder of the Tw...]

Used a reliable horizon calculator to come up with some figures. Provided you have a clear horizon.

When it is at 20 miles altitude (32 km), under perfect seeing, it should be visible for over 400 miles (640 km) in every direction. It will probably survive down to this far.

It should also be glowing brightly at 50 miles altitude (80 km), and at that point be seen for at least 650 miles (1000 km).

[dmuller]

Emily pointed to a beautiful simulation of the event at http://orbit.psi.edu/?q=node/22

[elakdawalla]

By the way, discussion on Minor Planets Mailing List (which is where I got the link to that simulation) indicates that the press release wasn't correct when it described the flight direction -- it's not coming in from northeast, it's coming in more from the west, basically over the Sahara.

--Emily

[volcanopele]

I agree, that's the direction I got from my simulation in Celestia.

[Holder of the Tw...]

Er.. thanks, HTL. (If I wrote Holder of the Two Leashes every time, my posts would get trashed for wasting bandwidth.)
When you referred to loads of observatories, I sort of anticipated a CometCam live picture.
Ephemera are nice, but not very sexy.

My bad. I'm one of the very few people who could even get a little excited over watching raw positional information pouring in.

Here is one real picture: Sky and Telescope

I'm pretty sure just about every other pic of 2008 TC3 looks like that at this point.

In a couple of hours, we may be getting some much more spectacular shots.

A lot of people will shorten my title to "Holder", and I'll answer to that. The dogs don't mind, either. Actually, they don't have a clue.

[nprev]

"Major Bolide Forecast Tonight; No Damage Expected" (S&T from Holder's link.)


What a headline!!! What a time to be alive!!! Nigel is absolutely right; this is marvelous, this is an expansion of our general situational awareness. We've always grown thereby through such things.

[Hungry4info]

If I did the math right, just a few more minutes until impact.

Two ways to look at it.

-> Small asteroid hits planet. No damage done.
-> Comparatively HUGE freaking Planet hits an asteroid, obliterating it. Owned.

Either way, the asteroid will be one with the planet. I look forward to pictures (I hope we get some).

[claurel]

Here's a Celestia simulation of 2008 TC3's entry into Earth's atmopshere:

http://www.youtube.com/watch?v=4FW3oaZgCz0

The green circle indicates the region where the asteroid is visible over the horizon. The trajectory of 2008 TC3 was taken from HORIZONS (about an hour ago.)

--Chris

[dmuller]

Here's a Celestia simulation of 2008 TC3's entry into Earth's atmopshere:
http://www.youtube.com/watch?v=4FW3oaZgCz0

Judging from that clip, 2008TC3 is gonna come down at / explode over the Nubian Desert, somewhere in the center of the triangle made up by the cities Wadi Halfa, Atbara & Port Sudan. Man, I flew over there some years ago!

EDIT: The Horizons system is very slow ... must have a lot of traffic!

[Hungry4info]

Going to? Has it already? Or did I again get my math wrong with time conversions? Lol.

[tedstryk]

Going to? Has it already? Or did I again get my math wrong with time conversions? Lol.

The time given was 10:46 EDT (my time zone). It is now 10:19 EDT. I plan to go outside....we are far too far away, but I figure that just in case it has some smaller cousins, it couldn't hurt to go take a look.

[claurel]

Here's a Celestia simulation of 2008 TC3's entry into Earth's atmopshere:

http://www.youtube.com/watch?v=4FW3oaZgCz0

The green circle indicates the region where the asteroid is visible over the horizon. The trajectory of 2008 TC3 was taken from HORIZONS (about an hour ago.)

This video gives the view from 2008 TC3:
http://www.youtube.com/watch?v=Cxa2PUluqVU
(Itokawa is standing in for 2008 TC3.)

The Celestia add-on used for both simulations is here: http://www.shatters.net/~claurel/celestia/...ids/2008tc3.zip
It requires a very recent version of Celestia, however; I'll make a more widely usable available post-impact.

--Chris

[Holder of the Tw...]

I will take the liberty of posting this quote from Emily's blog over at Planetary.org:

"Thanks to Ron Baalke for posting the following, from JPL asteroid scientist Paul Chodas, on the Minor Planets Mailing List:
Update - 6:45 PM PDT (1 hour prior to atmospheric entry)

Since its discovery barely a day ago, 2008 TC3 has been observed extensively by astronomers around the world, and as a result, our orbit predictions have become very precise. We estimate that this object will enter the Earth's atmosphere at around 2:45:28 UTC and reach maximum deceleration around 2:45:54 UTC at an altitude of about 14 km. These times are uncertain by +/- 15 seconds or so. The time at which any fragments might reach the ground depends a great deal on the physical properties of the object, but should be around 2:46:20 UTC +/- 40 seconds."


Well, the asteroid has passed into the earth's shadow, so telescope observations are at an end now.

Just waiting for the fireworks ...

[volcanopele]

As 2008 TC3 passes over Niger, let's us have a moment of silence for this little asteroid that could. 2008 TC3 started life when it was freed from sub-surface of a larger asteroid. For millions of years it wondered. Unloved. Uncared for. Unnoticed. Now, as it's end approachs, in a fiery burst of light, people care for this little guy.

God speed little doodle.

Now at 1,900 km above north africa.

[stevesliva]

And the earth emits a contented belch.

[deglr6328]

Well that was that....it would seem. Looks like we're all still here! I doubt anyone caught it. It hit news outlets so late in the day and it's almost 3am there. Even with seemingly everybody these days having a cameraphone on them... still doubtful.

[volcanopele]

At last check, Earth still here.

2008 TC3...not so much

[deglr6328]

my mistake, nearly 5am local time rather than 3 UTC.

[dmuller]

I can confirm that Australia is still here as well at 1:55 PM Sydney summer time ... and I couldnt even put up a realtime simulation (I was 4 minutes late) [at least the decision whether to use Earth Received Time or Space Object Event Time would have been easy this time around]. Just imagine this had been a very dark 'biggie' - the stock markets wouldn't even had time to crash further

[Guest_Bobby_*]

Any Videos or Photos of the event yet???

[deglr6328]

here you go!

------------------*

is breathtaking, no?

[Guest_jumpjack_*]

As 2008 TC3 passes over Niger, let's us have a moment of silence for this little asteroid that could. 2008 TC3 started life when it was freed from sub-surface of a larger asteroid.

mmmh....
hope mother-asteroid is not chasing her daughter....

[ugordan]

SpaceWeather.com has news about a possibly positive sighting (from a plane at roughly 750 nm away) of a flash at around the expected time of impact.

[deglr6328]

Well we can at least say that it wasn't CATASTROPHICALLY larger than predicted! Also the nearest ISS pass over the area is way off at the time of expected entry so there was no chance of observation from there...

http://www.heavens-above.com/gtrack.asp?la...amp;satid=25544

http://earthquake.usgs.gov/eqcenter/recent...gion/Africa.php

[volcanopele]

Surprised I haven't seen any word of this from Aswan or Abu Simbel in southern Egypt. These would seem like the likeliest places where word/images/movies would have been returned and posted on the net.

[Fran Ontanaya]

A small piece of info about spectra: http://tech.groups.yahoo.com/group/mpml/message/21169

[djellison]

That series of 10s exposures showing the thing 'speeding up' as it were - that's one of those rare astronomical observations that puts the Earth, the solar system, and the things flying around it into sharp '3d' context.

Doug

[Tman]

Maybe an indirect sighting of a webcam at El Grouna (middle east in Egypt): http://home.pages.at/thie/Asteroid/

In a German meteorite forum had someone contact to people in Egypt and they say it was great (more will be come I guess - the guy in the forum is sleeping now). Sadly Sadly their camera went off in waiting of the event and it was too late to start it again

[Guest_PhilCo126_*]

Based on 26 optical observations, the probability of impact is between 99.8 percent and 100 percent,... so this thing dropped in the sea?

[centsworth_II]

Based on 26 optical observations, the probability of impact is between 99.8 percent and 100 percent,...

"Impact" could just mean impact with the atmosphere. Is there any indication that the original estimation that no impactor would reach the ground (or sea) was wrong?

[Guest_PhilCo126_*]

O.K. impact with Earth's atmosphere was for sure, but I guess there was some chance this meteorite ended up somewhere in the desert?
As the meteor appeared at nighttime it was spotted by an airliner... so maybe something made it through the atmosphere???

[tedstryk]

As the meteor appeared at nighttime it was spotted by an airliner... so maybe something made it through the atmosphere???

What in the world does being spotted from an airliner have to do with reaching the ground?

[ElkGroveDan]

What in the world does being spotted from an airliner have to do with reaching the ground?

Maybe the airliner spotted it streaking by BELOW

[ngunn]

Spaceweather.com now has an update on an infrasound recording of the event.

[dmuller]

well it did get some coverage in Australia: headline at http://www.abc.net.au/news

[Guest_jumpjack_*]

No images/video after more than 24 hours. I guess it means none took any shot of the event?

[Guest_PhilCo126_*]

Other than the webcam images in the German forum and this press article, nothing special I'm afraid...
http://www.abc.net.au/news/stories/2008/10/08/2385111.htm

[Guest_jumpjack_*]

I found some guys who actually have SEEN the object!
http://www.chileastro.com/?p=329

RAW data (???): http://www.christen-eagle.com/slooh/2008_tc3/index.htm

Slooh forum: http://forum.slooh.com/

Slooh blog post on 2008 TC£ with links: http://www.slooh.com/blog/2008-tc3-a-serendipitous-event/

2 hours before atmosphere entry:


Slooh forum thread about raw data: http://forum.slooh.com/viewtopic.php?t=593...&highlight=

Slooh forum thread with images: http://forum.slooh.com/viewtopic.php?t=593...&highlight=

00:40 animation:

[Guest_jumpjack_*]

Standalone Windows .fit viewer:
http://www.nrao.edu/software/fitsview/fvwin.html

But I can't find .fit data around impact time! They end at 02.15!!

And I can't understand how to register to those forums...???

[Fran Ontanaya]

Meteosat 8 catched it! (see SpaceWeather.com)

[ugordan]

Nice! I was hoping some satellite would catch it or at least the infrared afterglow.

[Tman]

Another processed image of Meteosat http://www.eumetsat.int/groups/public/docu...teroid_2008.jpg

[Guest_jumpjack_*]

Another incoming?!?
http://remanzacco.blogspot.com/2008/10/fly...eroid-2008.html

[Guest_jumpjack_*]

2008 TC3 just 1 hour before reentry, while entering Earth shadow:
http://www.minorplanets.org/OLS/2008_TC3/


Another picture before impact, from Canaries islands:
http://www.inaf.it/news_cartella/asteroide-2008-tc3-tng

[djellison]

Another incoming?!?

Errr, NO. Very no.

"008 QS11 (classified as an Apollo-type NEO) will reach on 02 October 2008 the minimum distance from Earth (0.02767 A.U.) "

That's about 4 million km, or 10 times the earth-moon distance.

[Guest_jumpjack_*]

Full inline quote removed - Admin

according to an italian forum, MAYBE a page appeared on NASA site predicting a 1:79 chance to hit Earth (or enter atmosphere??), but page would be no more visible...

But actually I think somebody thaught that "REMOVED" from risk list means "HIDDEN", although it means "NO MORE RISKFUL"...

[Guest_PhilCo126_*]

True video of 2008 TC3 ??? ??? ???

http://www.youtube.com/watch?v=WPWqB5Zo53M...feature=related

[ugordan]

True video of 2008 TC3 ??? ??? ???

I don't buy it.

[djellison]

Nor do I - that's just your average meteor streak.

[deglr6328]

on the NIGHT OF entry I was looking at random youtube videos of meteorites and this was on there as another video name then. So, def fake.

[Tman]

Some analyses of the Meteosat images http://www.eumetsat.int/Home/Main/Media/Features/707785?l=en

[ugordan]

I haven't seen their ideas on whether the Meteosat images captured the streaking bolide or the fading fireball after disintegration. The fact IR and visible channel hotspot locations don't match, it's plausible the IR frame was captured a couple of seconds earlier with the "RGB" channels capturing the static fireball.
Thoughts?

[Guest_PhilCo126_*]

Looks like our doubts on the 2008 TC3 video were correct:

http://www.astronomy.com/asy/default.aspx?c=a&id=7468

[Guest_jumpjack_*]

Looks like our doubts on the 2008 TC3 video were correct:

http://www.astronomy.com/asy/default.aspx?c=a&id=7468

what?!?

[Tman]

Nice GIF of the fast gyrating http://www.skyandtelescope.com/community/s...g/30686199.html

...telescopic observations show that 2008 TC3 was gyrating wildly before it hit. According to Czech asteroid specialist Petr Pravec, it was "definitely a tumbler." His analysis reveals two distinct periods of 49 and 98 seconds long. One is probably due to rotation and the other to spin-axis precession, but he can't tell yet which is which. But he notes that this ranks (or ranked!) as one of the three fastest-spinning asteroids known.

Another one here http://news.astronomie.info/ai.php/headlines/200810020

[Tman]

That's by far a better one to trick with it - wow!

Today's APOD of a huge bolide http://antwrp.gsfc.nasa.gov/apod/ap081011.html

Astronomy enthusiast Howard Edin reports that he was looking in the opposite direction at the time, but saw the whole observing field light up and at first thought someone had turned on their car headlights.

[dilo]

Really impressive and beatiful lucky picture!

[Guest_jumpjack_*]

That's by far a better one to trick with it - wow!

Today's APOD of a huge bolide http://antwrp.gsfc.nasa.gov/apod/ap081011.html

it's NOT 2008 TC3, so what?!?

[claurel]

While hoping and waiting for some images of the bolide, I created another visualization of the trajectory and ground track of 2008 TC3 right before atmospheric entry. The trajectory comes from a HORIZONS integration on Oct. 6 (I don't think there have been any subsequent refinements since then.) The trajectory is marked off in minutes.

[Spin0]

I haven't seen their ideas on whether the Meteosat images captured the streaking bolide or the fading fireball after disintegration. The fact IR and visible channel hotspot locations don't match, it's plausible the IR frame was captured a couple of seconds earlier with the "RGB" channels capturing the static fireball.
Thoughts?

Could it be possible that the explosion had a highspeed directional jet of hot gas and dust? The explosion would be visible in visible channels and the hot jet-burst in infrared. And as the burst is very high-speed maybe it explains the 23 km distance between the two hotspots.

Last year Sandia Labs made new computer models and simulations regarding Tunguska explosion. Their simulations showed a higly directional high-speed jet of hot gas and dust emanating from an exploding asteroid when it explodes in the atmosphere. Here's a link to their news (with cool animations!): http://www.sandia.gov/news/resources/relea...7/asteroid.html

Simulations show that the material of an incoming asteroid is compressed by the increasing resistance of Earth’s atmosphere. As it penetrates deeper, the more and more resistant atmospheric wall causes it to explode as an airburst that precipitates the downward flow of heated gas.

[ugordan]

Could it be possible that the explosion had a highspeed directional jet of hot gas and dust? The explosion would be visible in visible channels and the hot jet-burst in infrared.

Why wouldn't the explosion be visible in the infrared as well?

[DDAVIS]

I created another visualization of the trajectory and ground track of 2008 TC3 right before atmospheric entry.

What would the entry angle have been?

Don

[claurel]

What would the entry angle have been?

Using the HORIZONS trajectory, I calculated it to be just over 19 degrees above the horizon plane within about a minute of impact.

--Chris

[Spin0]

Why wouldn't the explosion be visible in the infrared as well?

Well... um.. a good question!
You are right - the two different hot spots couldn't have been simultaneous. It looks like the 23 km difference in distance could have been actually a difference in time. Here's how I think it happened. And I really tried to be short but bear with me.

I found a Eumetsat pdf describing the imaging system of Meteosat 8 (SEVIRI): MSG Level 1.5 Image Data Format Description (pp.12-13)

Meteosat 8 spins 100 rpm in its geostationary orbit. For imaging it has 12 spectral channels and each channel has 3 detectors, except HRV has 9. The detectors are arranged into two 'rows' in the focal point: the 'warm row' has visual channels (HRV and VIS aka VNIR) and the 'cold row' has IR channels. A mirror reflects light into each detector line by line as the satellite spins and scans the image. During image scanning all 12 channels are recording the image simultaneously, but there will be a small timing difference between each channel. Within the same row the maximum timing difference is only 432 microseconds. But between warm and cold rows it's 3.6 seconds because of the time it takes for the mirror to turn it's angle to reflect the same spot of Earth to different rows. Timing differences are compensated by readdressing the images' lines and columns accordingly. As Earth and clouds move relatively slowly this difference in timing is not a big deal.

According to Eumetsat the meteor's entry velocity was 12.8 km/s.

The Eumetsat's page has three images of the fireball: two visual HRV and NCOL, and one infrared. Their channels are accordingly HRV, VIS and IR3.9. In the visual channels the images of the fireball seem to overlap and there's no mention of a noticeable difference in distance. The difference is noticeable in the IR-image and can be measured as a distance of approx. 23 km between the IR and visual channel image.

In the satellite the detectors for HRV and VIS channels are in the 'warm row' and IR3.9 is in the 'cold row'. So one would expect for the images from the same row to have a tiny timing difference of a few hundred microseconds, and the images from different rows to have a timing difference of 3.6 seconds plus some microseconds. And it looks like this is what we see - HRV and VIS channels' images don't show a noticeable difference in distance. But the timing difference becomes notable when compared to the IR3.9 channel image from the cold row. I think that's why there's two separate fireballs and not three.

The maximum timing difference between the 'warm row' channels is 432 microseconds, at 12.8 km/s velocity it translates to 0.55 km distance. This is well within the satellite's interchannel Residual Misregistration Requirement of 1.5 km and would not be noticeable in the visual channel images. But the 3.6 s timing difference between visual and IR channels would be noticeable at the meteor's velocity.

But 3.6 seconds at 12.8 km/s would translate to 46 km distance - not 23 km as measured in the images. Could this be due to meteor's deceleration?

[ugordan]

Great analysis, Spin0. I think you've nailed the reason for the discrepancy. I had a hunch it had something to do with different timings in the satellite, but I didn't expect the thing to be rotating so fast and with mirrors and all!

I agree that the smaller 23 km distance likely comes from deceleration - the time is near expected impact, well into peak heating and deceleration.

[dilo]

Excellent work, Spin! I think too that halved distance could be easily explained by atmospheric deceleration, obviously definitive confirm would need a more accurate simulation to match data.

[Spin0]

US Gov fireball data release regarding 2008 TC3:

Fireball Detection

Sensors aboard US satellites detected the impact of a bolide over Africa on 7 October 2008 at 02:45:40 UT. The initial observation put the object at 65.4 km altitude at 20.9 degrees North Latitude, 31.4 degrees East Longitude. The object detonated at an altitude of approximately 37 km at 20.8 degrees North Latitude, 32.2 degrees East Longitude. The total radiated energy was approximately 4.0X10^11 joules. This is equivalent to approximately 0.1 KT of radiated energy (assumes a 6000 Kelvin black body).

http://aquarid.physics.uwo.ca/~pbrown/usaf.html

[ugordan]

US Gov fireball data release regarding 2008 TC3

Interestingly, the radiative energy of 0.1 kT is an order of magnitude lower than the infrasound estimate of the blast wave (between 1.1 and 2.1 kT). I find that a bit surprising, for example nuclear detonations (a bad analogue, but similar high energy density in a low volume after the initial high energy fireball expands a bit) produce roughly a 60:40 thermal:blast energy distribution, shifting even more in favor of thermal effect at higher altitudes.

What's more, the detonation altitude of 37 kilometers is seriously high which puzzles me even more - how can a small fast moving object couple most of its energy to a very rarified atmosphere? I'd expect vaporization of the body, plasma around it and radiative cooling as primary energy deposition mechanism.

[Mongo]

I guess that this shows that we still have a lot to learn about upper-atmosphere meteoric explosions -- were any hard data on radiative vs blast energy collected from previous similarly-sized events?

I would guess that military observation sats have recorded similar explosions in the past, but their detailed results would presumably not have been made publicly available.

I would love to see a plot of total energy vs blast/radiation ratio vs detonation altitude for as many events as the information has been obtained for.

[ugordan]

I would guess that military observation sats have recorded similar explosions in the past, but their detailed results would presumably not have been made publicly available.

http://aquarid.physics.uwo.ca/~pbrown/usaf.html

[nprev]

Neat link, Gordan; thanks!

Re the detonation stats: I suspect what we're seeing is a lot more compositional variation in these objects than is generally assumed. Recovered meteorites are overwhelmingly fairly robust rocks (iron/nickel, stony); falls like that extremely volatile-rich one up in Canada a few years ago are exceedingly rare since the material is so fragile; has to be a true big 'un to survive the trip.

So, this might be affecting our assumptions about the entire meteoritic/asteroidal population in general. Sure wish that some of these staring sats were obtaining detailed broad-band spectra of the events, esp. the residual trails. (Hey, there's a mission proposal in there for somebody! Maybe ride-along sensors on GOES or other geosynchronous satellites?)

[Guest_jumpjack_*]

http://aquarid.physics.uwo.ca/~pbrown/usaf.html

So we have a military high-atmosphere monitoring system? Relic from ancient "Star Wars project"?

Do those acronyms in that page mean that there are so MANY USAF satellites up there? Or do they refer to observation times?

[djellison]

So we have a military high-atmosphere monitoring system?

Loads. It doesn't take much imagination to figure out what they're actually for.


Doug

[volcanopele]

Spying for Major League Baseball? (sorry, old Simpsons joke)

Seriously, the military routinely monitors meteoric airbursts as part of their campaign to monitor nuclear weapons testing and as an early warning system. I seem to recall hearing that there are usually a few events per year that are big enough to set off alerts at NORAD (but that could just be an urban legend).

[ugordan]

I seem to recall hearing that there are usually a few events per year that are big enough to set off alerts at NORAD (but that could just be an urban legend).

I don't think those are rumors. There's a relatively recent story of a large asteroid detonating over the Mediterranean right at the time India and Pakistan were engaged in a military standoff. The asteroid released a yield of 26 kilotons which, had it detonated above India or Pakistan, could have caused some hairy consequences.

More at wikipedia: http://en.wikipedia.org/wiki/Eastern_Mediterranean_Event

[Guest_jumpjack_*]

full inline quote removed. Admins are VERY scary. - Admin

Scary.

[ugordan]

Scary.

Welcome to the real world...

[stevesliva]

Seriously, the military routinely monitors meteoric airbursts as part of their campaign to monitor nuclear weapons testing and as an early warning system.

Launch-detect, too. They're monitoring ballistic missile and orbital rocket launches.

The first gamma-ray detectors in orbit were, of course, looking down.

For nuclear weapons test monitoring, I believe the USAF has planes setup for atmospheric sampling, or did. It would be neat if these happened to be near enough to sniff around after a bolide. And of course, the satellites have also led to a regime of pre-announcing missile tests, so there are the sister aircraft that are configured to watch things fall into the atmosphere. The planes are 40-some-years old! (And will likely be flying when they're 60...)