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

[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...)

[tty]

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......

[nprev]

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.