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INCOMING!, Detection and observation of Earth-approaching asteroids.
Paolo
post Oct 6 2008, 07:53 PM
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no sone seems to have noticed this yet


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Tman
post Oct 10 2008, 07:13 AM
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Some analyses of the Meteosat images http://www.eumetsat.int/Home/Main/Media/Features/707785?l=en


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ugordan
post Oct 10 2008, 07:35 AM
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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?


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Spin0
post Oct 11 2008, 07:59 PM
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QUOTE (ugordan @ Oct 10 2008, 10:35 AM) *
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

QUOTE
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.



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ugordan
post Oct 11 2008, 08:02 PM
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QUOTE (Spin0 @ Oct 11 2008, 09:59 PM) *
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?


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Spin0
post Oct 12 2008, 11:24 AM
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QUOTE (ugordan @ Oct 11 2008, 11:02 PM) *
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?
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ugordan
post Oct 12 2008, 11:38 AM
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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.


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dilo
post Oct 12 2008, 05:36 PM
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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.


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Posts in this topic
- Paolo   INCOMING!   Oct 6 2008, 07:53 PM
- - climber   Too much info kill the info! Where do we have ...   Oct 6 2008, 07:57 PM
- - ugordan   Whoa! Any chance of organizing a crash observi...   Oct 6 2008, 07:58 PM
- - Holder of the Two Leashes   An asteroid... well, really a meteor, is now predi...   Oct 6 2008, 07:58 PM
- - charborob   Any idea how big is this rock?   Oct 6 2008, 08:00 PM
- - Juramike   QUOTE The absolute magnitude indicates that the ob...   Oct 6 2008, 08:03 PM
- - imipak   Is this the first time a fireball's been predi...   Oct 6 2008, 08:05 PM
- - TheChemist   Hey guys, don't just tear your swimming suits ...   Oct 6 2008, 08:12 PM
- - Holder of the Two Leashes   There have been at least three revisions in the la...   Oct 6 2008, 08:19 PM
- - climber   30.4!!! Gona be visible over the horiz...   Oct 6 2008, 08:45 PM
- - Holder of the Two Leashes   Space.com is now reporting the story, and says atm...   Oct 6 2008, 08:46 PM
|- - SFJCody   I wonder if it can be imaged from orbit during ent...   Oct 6 2008, 09:30 PM
- - Shaka   From TPS: QUOTE The meteor is expected to be visi...   Oct 6 2008, 09:31 PM
|- - SFJCody   I guess once LSST and PanSTARRS come online we...   Oct 6 2008, 09:44 PM
|- - nprev   QUOTE (Shaka @ Oct 6 2008, 01:31 PM) My S...   Oct 7 2008, 12:10 AM
|- - Shaka   QUOTE (nprev @ Oct 6 2008, 02:10 PM) ...p...   Oct 7 2008, 12:27 AM
- - ngunn   It may be small and harmless, but for me knowing i...   Oct 6 2008, 09:44 PM
- - Holder of the Two Leashes   Man, I've never seen anything quite like this....   Oct 6 2008, 10:39 PM
- - Shaka   LINKS, man! Give us links, HTL!   Oct 6 2008, 10:53 PM
- - Holder of the Two Leashes   Link Anything with 2008 TC3. Most recent on top....   Oct 6 2008, 10:59 PM
- - Juramike   I guess they won't be seeing it from here (bad...   Oct 6 2008, 11:31 PM
- - dmuller   If this thing is coming in shallow from NE to SW t...   Oct 6 2008, 11:38 PM
- - volcanopele   hmm, I think my Celestia copy needs fixing. Using...   Oct 6 2008, 11:46 PM
- - Fran Ontanaya   The NEO Program lists it as a close approach at 0....   Oct 6 2008, 11:55 PM
- - Holder of the Two Leashes   Used a reliable horizon calculator to come up with...   Oct 6 2008, 11:59 PM
- - nprev   RE: INCOMING!   Oct 7 2008, 12:34 AM
- - dmuller   Emily pointed to a beautiful simulation of the eve...   Oct 7 2008, 12:47 AM
- - elakdawalla   By the way, discussion on Minor Planets Mailing Li...   Oct 7 2008, 12:56 AM
- - volcanopele   I agree, that's the direction I got from my si...   Oct 7 2008, 01:00 AM
- - Holder of the Two Leashes   QUOTE (Shaka @ Oct 6 2008, 06:48 PM) Er.....   Oct 7 2008, 01:00 AM
- - nprev   "Major Bolide Forecast Tonight; No Damage Exp...   Oct 7 2008, 01:19 AM
- - Hungry4info   If I did the math right, just a few more minutes u...   Oct 7 2008, 01:39 AM
- - claurel   Here's a Celestia simulation of 2008 TC3's...   Oct 7 2008, 01:44 AM
|- - dmuller   QUOTE (claurel @ Oct 7 2008, 11:44 AM) He...   Oct 7 2008, 01:58 AM
- - Hungry4info   Going to? Has it already? Or did I again get my ma...   Oct 7 2008, 02:00 AM
|- - tedstryk   QUOTE (Hungry4info @ Oct 7 2008, 03:00 AM...   Oct 7 2008, 02:23 AM
- - claurel   Here's a Celestia simulation of 2008 TC3's...   Oct 7 2008, 02:31 AM
- - Holder of the Two Leashes   I will take the liberty of posting this quote from...   Oct 7 2008, 02:32 AM
- - volcanopele   As 2008 TC3 passes over Niger, let's us have a...   Oct 7 2008, 02:40 AM
|- - jumpjack   QUOTE (volcanopele @ Oct 7 2008, 04:40 AM...   Oct 7 2008, 07:49 AM
|- - ugordan   SpaceWeather.com has news about a possibly positiv...   Oct 7 2008, 08:33 AM
- - stevesliva   And the earth emits a contented belch.   Oct 7 2008, 02:50 AM
- - deglr6328   Well that was that....it would seem. Looks like we...   Oct 7 2008, 02:50 AM
- - volcanopele   At last check, Earth still here. 2008 TC3...not s...   Oct 7 2008, 02:51 AM
- - deglr6328   my mistake, nearly 5am local time rather than 3 UT...   Oct 7 2008, 02:53 AM
- - dmuller   I can confirm that Australia is still here as well...   Oct 7 2008, 02:57 AM
- - Bobby   Any Videos or Photos of the event yet???   Oct 7 2008, 03:48 AM
- - deglr6328   here you go! ------------------* ...   Oct 7 2008, 03:57 AM
- - deglr6328   Well we can at least say that it wasn't CATAST...   Oct 7 2008, 08:48 AM
- - volcanopele   Surprised I haven't seen any word of this from...   Oct 7 2008, 09:20 AM
- - Fran Ontanaya   A small piece of info about spectra: http://tech.g...   Oct 7 2008, 09:49 AM
- - djellison   That series of 10s exposures showing the thing ...   Oct 7 2008, 09:57 AM
- - Tman   Maybe an indirect sighting of a webcam at El Groun...   Oct 7 2008, 10:27 AM
- - PhilCo126   Based on 26 optical observations, the probability ...   Oct 7 2008, 05:06 PM
|- - centsworth_II   QUOTE (PhilCo126 @ Oct 7 2008, 01:06 PM) ...   Oct 7 2008, 05:25 PM
- - PhilCo126   O.K. impact with Earth's atmosphere was for su...   Oct 7 2008, 05:31 PM
|- - tedstryk   QUOTE (PhilCo126 @ Oct 7 2008, 06:31 PM) ...   Oct 7 2008, 06:29 PM
|- - ElkGroveDan   QUOTE (tedstryk @ Oct 7 2008, 11:29 AM) W...   Oct 7 2008, 08:20 PM
- - ngunn   Spaceweather.com now has an update on an infrasoun...   Oct 7 2008, 09:45 PM
- - dmuller   well it did get some coverage in Australia: headli...   Oct 8 2008, 02:36 AM
- - jumpjack   No images/video after more than 24 hours. I guess ...   Oct 8 2008, 06:38 AM
- - PhilCo126   Other than the webcam images in the German forum a...   Oct 8 2008, 10:36 AM
- - jumpjack   I found some guys who actually have SEEN the objec...   Oct 8 2008, 02:09 PM
- - jumpjack   Standalone Windows .fit viewer: http://www.nrao.ed...   Oct 8 2008, 02:43 PM
- - Fran Ontanaya   Meteosat 8 catched it! (see SpaceWeather.com)   Oct 8 2008, 06:26 PM
|- - ugordan   Nice! I was hoping some satellite would catch ...   Oct 8 2008, 06:33 PM
- - Tman   Another processed image of Meteosat http://www.eum...   Oct 9 2008, 10:37 AM
- - jumpjack   Another incoming?!? http://remanzacco.blogspot...   Oct 9 2008, 01:04 PM
|- - djellison   QUOTE (jumpjack @ Oct 9 2008, 02:04 PM) A...   Oct 9 2008, 01:06 PM
|- - jumpjack   Full inline quote removed - Admin according to an...   Oct 9 2008, 01:21 PM
- - jumpjack   2008 TC3 just 1 hour before reentry, while enterin...   Oct 9 2008, 01:06 PM
- - PhilCo126   True video of 2008 TC3 ??? ??? ??? http://www....   Oct 9 2008, 06:09 PM
|- - ugordan   QUOTE (PhilCo126 @ Oct 9 2008, 08:09 PM) ...   Oct 9 2008, 06:12 PM
- - djellison   Nor do I - that's just your average meteor str...   Oct 9 2008, 06:14 PM
- - deglr6328   on the NIGHT OF entry I was looking at random yout...   Oct 9 2008, 07:53 PM
- - Tman   Some analyses of the Meteosat images http://www.eu...   Oct 10 2008, 07:13 AM
|- - ugordan   I haven't seen their ideas on whether the Mete...   Oct 10 2008, 07:35 AM
|- - Spin0   QUOTE (ugordan @ Oct 10 2008, 10:35 AM) I...   Oct 11 2008, 07:59 PM
|- - ugordan   QUOTE (Spin0 @ Oct 11 2008, 09:59 PM) Cou...   Oct 11 2008, 08:02 PM
|- - Spin0   QUOTE (ugordan @ Oct 11 2008, 11:02 PM) W...   Oct 12 2008, 11:24 AM
|- - ugordan   Great analysis, Spin0. I think you've nailed t...   Oct 12 2008, 11:38 AM
|- - dilo   Excellent work, Spin! I think too that halved ...   Oct 12 2008, 05:36 PM
- - PhilCo126   Looks like our doubts on the 2008 TC3 video were c...   Oct 10 2008, 06:56 PM
|- - jumpjack   QUOTE (PhilCo126 @ Oct 10 2008, 08:56 PM)...   Oct 11 2008, 08:49 AM
- - Tman   Nice GIF of the fast gyrating http://www.skyandtel...   Oct 11 2008, 09:15 AM
- - Tman   That's by far a better one to trick with it - ...   Oct 11 2008, 04:11 PM
|- - dilo   Really impressive and beatiful lucky picture!   Oct 11 2008, 05:49 PM
|- - jumpjack   QUOTE (Tman @ Oct 11 2008, 06:11 PM) That...   Oct 11 2008, 06:02 PM
- - claurel   While hoping and waiting for some images of the bo...   Oct 11 2008, 06:46 PM
|- - DDAVIS   I created another visualization of the trajectory ...   Oct 11 2008, 09:58 PM
|- - claurel   QUOTE (DDAVIS @ Oct 11 2008, 02:58 PM) Wh...   Oct 12 2008, 04:51 AM
- - Spin0   US Gov fireball data release regarding 2008 TC3: ...   Oct 16 2008, 02:34 PM
|- - ugordan   QUOTE (Spin0 @ Oct 16 2008, 04:34 PM) US ...   Oct 16 2008, 02:56 PM
- - Mongo   I guess that this shows that we still have a lot t...   Oct 16 2008, 05:14 PM
|- - ugordan   QUOTE (Mongo @ Oct 16 2008, 07:14 PM) I w...   Oct 16 2008, 05:22 PM
|- - jumpjack   QUOTE (ugordan @ Oct 16 2008, 07:22 PM) h...   Oct 17 2008, 07:25 AM
|- - djellison   QUOTE (jumpjack @ Oct 17 2008, 08:25 AM) ...   Oct 17 2008, 07:37 AM
- - nprev   Neat link, Gordan; thanks! Re the detonation ...   Oct 16 2008, 09:58 PM
- - volcanopele   Spying for Major League Baseball? (sorry, old Simp...   Oct 17 2008, 08:59 AM
- - ugordan   QUOTE (volcanopele @ Oct 17 2008, 10:59 A...   Oct 17 2008, 09:16 AM
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