IPB

Welcome Guest ( Log In | Register )

27 Pages V  « < 6 7 8 9 10 > »   
Reply to this topicStart new topic
INCOMING!, Detection and observation of Earth-approaching asteroids.
nprev
post Oct 19 2008, 11:04 AM
Post #106


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



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


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
ugordan
post Oct 19 2008, 03:58 PM
Post #107


Senior Member
****

Group: Members
Posts: 3648
Joined: 1-October 05
From: Croatia
Member No.: 523



QUOTE (PhilCo126 @ Oct 19 2008, 11:51 AM) *
... 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.


--------------------
Go to the top of the page
 
+Quote Post
Fran Ontanaya
post Oct 19 2008, 09:57 PM
Post #108


Member
***

Group: Members
Posts: 293
Joined: 22-September 08
From: Spain
Member No.: 4350



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.
Go to the top of the page
 
+Quote Post
mchan
post Oct 20 2008, 02:48 AM
Post #109


Member
***

Group: Members
Posts: 599
Joined: 26-August 05
Member No.: 476



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.
Go to the top of the page
 
+Quote Post
deglr6328
post Oct 20 2008, 04:01 AM
Post #110


Member
***

Group: Members
Posts: 356
Joined: 12-March 05
Member No.: 190



I was the one who initially created the Bhangmeter article a few years ago. smile.gif
Go to the top of the page
 
+Quote Post
Guest_PhilCo126_*
post Oct 20 2008, 10:34 AM
Post #111





Guests






It looks like nobody noticed the question mark in blue circle at top left of my reply smile.gif
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 unsure.gif so for IYA 2009 a recheck might be necessary...

BTW superb reply on the etymology of the word "Bhangmeter" cool.gif

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 huh.gif

Go to the top of the page
 
+Quote Post
Guest_PhilCo126_*
post Oct 20 2008, 05:53 PM
Post #112





Guests






http://www.astroguard.com/

and a few good books on the subject:
Go to the top of the page
 
+Quote Post
Guest_PhilCo126_*
post Oct 20 2008, 07:25 PM
Post #113





Guests






Back on topic; 2008TC3 meteor of 7th October 2008:
http://www.observatorij.org/News/News.html
ohmy.gif
Go to the top of the page
 
+Quote Post
Tman
post Nov 6 2008, 10:28 AM
Post #114


Member
***

Group: Members
Posts: 877
Joined: 7-March 05
From: Switzerland
Member No.: 186



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.


--------------------
Go to the top of the page
 
+Quote Post
Tman
post Nov 8 2008, 10:43 AM
Post #115


Member
***

Group: Members
Posts: 877
Joined: 7-March 05
From: Switzerland
Member No.: 186



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

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


--------------------
Go to the top of the page
 
+Quote Post
Guest_PhilCo126_*
post Nov 22 2008, 09:21 AM
Post #116





Guests






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

Go to the top of the page
 
+Quote Post
Guest_PhilCo126_*
post Nov 28 2008, 11:06 AM
Post #117





Guests






The search continues: http://www.sciencedaily.com/releases/2008/...81125141602.htm
cool.gif
Go to the top of the page
 
+Quote Post
marsbug
post Nov 28 2008, 11:48 AM
Post #118


Member
***

Group: Members
Posts: 401
Joined: 5-January 07
From: Manchester England
Member No.: 1563



QUOTE (PhilCo126 @ Nov 22 2008, 09:21 AM) *
Another Fireball this month: Canada 20th November 2008

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



!

Thats beautifull, but quite scary...


--------------------
Go to the top of the page
 
+Quote Post
Tman
post Nov 29 2008, 05:19 PM
Post #119


Member
***

Group: Members
Posts: 877
Joined: 7-March 05
From: Switzerland
Member No.: 186



First piece has been located (looks nice... the meteorite) http://www.youtube.com/watch?v=UjU8boyXwqc


--------------------
Go to the top of the page
 
+Quote Post
Guest_PhilCo126_*
post Nov 29 2008, 09:36 PM
Post #120





Guests






Indeed a very nice piece:
http://www.foxnews.com/story/0,2933,458984,00.html
cool.gif

http://skyriver.ca/astro/bruce/meteorite.htm
Go to the top of the page
 
+Quote Post

27 Pages V  « < 6 7 8 9 10 > » 
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 29th March 2024 - 09:09 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.