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INCOMING!, Detection and observation of Earth-approaching asteroids.
Mongo
post Oct 16 2008, 05:14 PM
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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.
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ugordan
post Oct 16 2008, 05:22 PM
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QUOTE (Mongo @ Oct 16 2008, 07:14 PM) *
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


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nprev
post Oct 16 2008, 09:58 PM
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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?)


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post Oct 17 2008, 07:25 AM
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QUOTE (ugordan @ Oct 16 2008, 07:22 PM) *

So we have a military high-atmosphere monitoring system? huh.gif 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?
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djellison
post Oct 17 2008, 07:37 AM
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QUOTE (jumpjack @ Oct 17 2008, 08:25 AM) *
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
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volcanopele
post Oct 17 2008, 08:59 AM
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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).


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ugordan
post Oct 17 2008, 09:16 AM
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QUOTE (volcanopele @ Oct 17 2008, 10:59 AM) *
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


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Guest_jumpjack_*
post Oct 17 2008, 09:16 AM
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ugordan
post Oct 17 2008, 09:18 AM
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QUOTE (jumpjack @ Oct 17 2008, 11:16 AM) *
Scary. blink.gif

Welcome to the real world...


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stevesliva
post Oct 18 2008, 01:04 PM
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QUOTE (volcanopele @ Oct 17 2008, 04:59 AM) *
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...)
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tty
post Oct 18 2008, 05:52 PM
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It's the same in Sweden. We use 45 year old J 32B Lansen aircraft for the air sampling mission. In addition they are also part of the Air Force Historical Flight......
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nprev
post Oct 18 2008, 06:23 PM
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QUOTE (ugordan @ Oct 17 2008, 02:18 AM) *
Welcome to the real world...


I do seem to remember seeing a report on the Montana local news a few days after the 1972 Daylight Fireball happened that NORAD was rapidly ramping up to a full alert, since it at first glance looked like a possible sub-launched missile heading in the general direction of Malmstrom AFB...scary indeed.


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post Oct 19 2008, 09:51 AM
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Pitty the list doesn't give info on the satellite-recorded impact of 1s February 1994 above Papua New Guinea.
The event was witnessed by fishermen near the island of Kusaie, the explosion occurred at 35 km altitude.
According to the observed flash, scientists estimated that the original object was about 15 m in diameter and the blast energy was in the range of about 100 KiloTons ( comparison: Atombombs: Hiroshima = 10 KiloTon , Nagasaki = 20 KiloTon ).

So far statistics point out that a 1 KiloTon event takes place every WEEK, and a 1 MegaTon event once every MONTH...
Although 35000 tons of material per year fall into Earth's atmosphere, and 70% of our planet consists of oceans, the 1 MegaTon rate seems alarming huh.gif
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nprev
post Oct 19 2008, 10:34 AM
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No worries:

"The Earth gains mass each day, as a result of incoming debris from space. This occurs in the forms of "falling stars", or meteors, on a dark night. The actual amount of added material depends on each study, though it is estimated that 10 to the 8th power kilograms of in-falling matter accumulates every day. The seemingly large amount, however, is insignificant to the Earth's total mass. The Earth adds an estimated one quadrillionth of one percent to its weight each day."

--from this source.


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Guest_PhilCo126_*
post Oct 19 2008, 10:50 AM
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Indeed no worries, but being a meteorite collector, the subject fascinates me cool.gif
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