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

[Guest_PhilCo126_*]

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

[nprev]

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.

[Guest_PhilCo126_*]

Indeed no worries, but being a meteorite collector, the subject fascinates me

[nprev]

I hear ya; I have a couple myself (a Silkhote-Alin & a small Allende piece.)

[ugordan]

... a 1 MegaTon event once every MONTH...

Um, are you sure about this? Can you give some references?

That doesn't jibe with estimates I've found on the web, I could buy a kiloton event every month or a few months, but a megaton event is a major fraction of a Tunguska-type event - those are said to happen once every few decades at most.

[Fran Ontanaya]

In a 2002 interview for the BBC, a retired member of the US Department of Defense recalled a 100 kT explosion detected over Greenland in 1996. That seems to imply that 1 MT bolids aren't very common.

[mchan]

Agree with ugordan on the dubious megaton class events. I recall the Sky and Telescope article (c. late 1980's) which discussed the stats when data on atmospheric detonation detections from the US Defense Support Program (early warning satellites) were sanitized and released. The largest events going back decades were in the ten to low tens of kiloton range. A megaton class event would likely make the television news even if it happened over in the middle of the Pacific Ocean.

The sensor that detects these detonations are intended to detect nuclear explosions --

Bhangmeter

The etymology of the word is an interesting bit of trivia.

In the Cold War days of long nuclear war scenarios, the US had some pretty Strangelovian plans for capabilities that were at least partially implemented. This was the Integrated Operational NUDET Detection System (IONDS) which put bhangmeters on GPS satellites so the location of detonations can be plotted to tens of meters. One use would be for nuclear attack damage assessment, i.e., did the target get blown up or are additional attacks needed?

Atmospheric detonations of meteors would similarly be well pinpointed.

[deglr6328]

I was the one who initially created the Bhangmeter article a few years ago.

[Guest_PhilCo126_*]

It looks like nobody noticed the question mark in blue circle at top left of my reply
Indeed the 1 MegaTon event rate seemed over-estimated, I'll check this evening in which book/article I've found that number. I have been using it in lectures during the last few years so for IYA 2009 a recheck might be necessary...

BTW superb reply on the etymology of the word "Bhangmeter"

US Department of Defense and Department of Energy satellites scanning the Earth for evidence of nuclear explosions over the last eight years detected nearly 300 optical flashes caused by small asteroids (one to 10 metres in size) exploding in the upper atmosphere. This provided research teams with a new estimate of the flux of near-Earth objects colliding with the Earth. The revised estimate suggests Earth's upper atmosphere is hit about once a year by asteroids that release energy equivalent to five kilotons of TNT. The object that exploded above Tunguska, Siberia in 1908 was considered 'small' (30 to 50 metres across), yet its energy was big enough to flatten 2,000 square kilometres of forest. It would have completely destroyed a city the size of New York.
Prior estimates suggested that Tunguska-like events (10-15 MegaTon) happened every 1,000 years or so. New estimates put that closer to the 250-300 year range. Although estimates are based on a lot of uncertainty, every couple of centuries there could be a significant event…

So I guess that brings numbers down to a 10 KiloTon event every year

[Guest_PhilCo126_*]

http://www.astroguard.com/

and a few good books on the subject:

[Guest_PhilCo126_*]

Back on topic; 2008TC3 meteor of 7th October 2008:
http://www.observatorij.org/News/News.html

[Tman]

Summary of the fall on http://neo.jpl.nasa.gov/news/2008tc3.html

It also mentions the Egyptian webcam as a possible capture of the flash http://home.pages.at/thie/asteroid_2008_tc3/

Btw. the search for fragments in Sudan seems to be under way.

[Tman]

Wow, eventually someone managed to capture the persistent train after the impact http://asima.seti.org/

http://antwrp.gsfc.nasa.gov/apod/ap081108.html

[Guest_PhilCo126_*]

Another Fireball this month: Canada 20th November 2008

YouTube video:
http://www.youtube.com/watch?v=e_2aX-784sw

More info:
http://www.ctvbc.ctv.ca/servlet/an/local/C...ishColumbiaHome

[Guest_PhilCo126_*]

The search continues: http://www.sciencedaily.com/releases/2008/...81125141602.htm