First pre-impact discovery for NEO search!

[Graff]

Originally Posted by cheesehead

Chuffed? Hmmm ...

http://english2american.com/dictionary/c.html (entry has important caveats!)

Hope that's okay. Some other online dictionaries might mislead, not having the above important caveats.

"Chuffed" is a perfectly respectable word. "Chuff" is
not to be used in polite company. Not quite sure
why the page you mentioned seems to need to warn
you about using "chuffed"...

Gareth

[Graff]

Originally Posted by cheesehead

An object as close to Earth as this one was when discovered is plenty close enough for its motion to take it over a substantial arc during a short time. Then the problem becomes one of keeping up with it -- if the initial observer gets only one position, no orbit can be projected; if only a couple of positions an hour or so apart, then the preliminary path projection may not be good enough for other observers to find it (which, after all, is just a small point of light among millions of other points of light).

Acutally, that last situation is very common. It essentially
happens every time a new NEO is discovered. The
discoverers report 3 to 5 observations of a moving object
to the Minor Planet Center which, if we decide that the
object really could be a new NEO, post a prediction (with
uncertainties) on the NEO Confirmation Page. Other
observers use the information to make further
observations. They report the observations to us,
we update the predictions. As a result, further
observations are obtained. When the orbit is "secure",
it is removed from the NEOCP and, if it is an NEO or
other interesting object, announced on a MPEC.
Most of the posting of new objects and updating of
predictions is usually done automatically.

This sequence of events happened with 2008 TC3.
If you look at the discovery MPEC
(http://www.cfa.harvard.edu/mpec/K08/K08T50.html)
you will see that follow-up observations were obtained
very quickly. If you look at other surrounding MPECs
for other discoveries, you will see that sometimes
the follow-up observations are not obtained for one or
two days after discovery, all based on a prediction made
from an observed arc of one hour or less.

We've been very good in the past 20 years at making
good predictions of short-term future motion based on
very limited observational information. And not only
for NEOs, but also for TNOs.

Gareth

[cheesehead]

Originally Posted by Graff

"Chuffed" is a perfectly respectable word. "Chuff" is not to be used in polite company.

See? That distinction is automatic to you, right?

Not over here!

Here, neither "chuffed" nor its present tense is commonly known, much less used, and verb and verbed are, of course, by default considered equally polite in general.

Not quite sure why the page you mentioned seems to need to warn you about using "chuffed"...

exactly because the distinction that's natural to you would not be known or suspected to many folks here, so an English-to-American translation dictionary needs to warn the American reader.

When I visited England, I encountered a few such verbal misunderstandings (fortunately, none that rude ... at least, no one said so ...) before I bought an American-to-English/English-to-American translation dictionary at the gift shop outside Salisbury Cathedral. If I'd never seen a BBC production on public television here previously, I might have gotten into trouble.

[cheesehead]

Originally Posted by Graff

Acutally, that last situation is very common.

... depending on our individual definitions of "close", "substantial", and "good".

I wrote that previous entry aimed toward an average reader not familiar with MPECs or NEOCP, or indeed with celestial mechanics at all. Only when I saw Norm's second posting just ahead of mine was I reminded that he didn't need that level of explanation. (I knew you didn't.)

I don't do any sky observing or orbit calculations nowadays, but I comfortably read MPECs, NEOCP, etc., and subscribe to MPML Digest.

If you look at the discovery MPEC (http://www.cfa.harvard.edu/mpec/K08/K08T50.html) you will see that follow-up observations were obtained very quickly.

... which I did as soon as I read MPML Digest Number 3032.

[Spherical Cow]

Originally Posted by Graff

If you look at the discovery MPEC
(http://www.cfa.harvard.edu/mpec/K08/K08T50.html)
you will see that follow-up observations were obtained
very quickly.

Gareth

That must give everyone an interesting feeling as they see "Delta" going
to zero like that (on the MPEC). Probably makes you take a second look
at the magnitudes to be sure the object isn't too terribly big.

From Cheesehead:

I wrote that previous entry aimed toward an average reader not
familiar with MPECs or NEOCP, or indeed with celestial mechanics at all.
Only when I saw Norm's second posting just ahead of mine was I reminded
that he didn't need that level of explanation. (I knew you didn't.)

A very good description, though, for the folks that haven't passed through
some orbital mechanics during their wanderings. Although I suspect there's
a fair number of astronomy types wandering around loose in this forum.

Gareth: Glad to contribute in some minor form to your wife feeling "chuffed".
(But that is a very odd term...)

Norm

[cheesehead]

"Impact of Asteroid 2008 TC3 Confirmed"

http://neo.jpl.nasa.gov/news/news160.html

Don Yeomans
NASA/JPL Near-Earth Object Program Office
October 7, 2008

Confirmation has been received that the asteroid impact fireball occurred at the predicted time and place. The energy recorded was estimated to be 0.9 to 1.0 kT of TNT and the time of detection was 02:45:45 on October 7 (Greenwich Standard Time). More details on this detection will be forthcoming. An additional confirmation was apparently reported by a KLM airliner (see: http://www.spaceweather.com/). As reported by Peter Brown (University of Western Ontario, Canada), a preliminary examination of infrasound stations nearest to the predicted impact point shows that at least one station recorded the event. These measurements are consistent with the predicted time and place of the atmospheric impact and indicate an estimated energy of 1.1 - 2.1 kT of TNT.

The follow-up astrometric observations from professional and sophisticated amateur astronomers alike were rather extraordinary, with 570 observations from 26 observatories being reported between the time of discovery by the Catalina Sky Survey to just before the object entered Earth's shadow (57 minutes prior to impact). All this happened in less than 19 hours!

[cheesehead]

At the spaceweather.com site, you have to go to their archive for October 7 to see:

http://www.spaceweather.com/archive....h=10&year=2008

"ASTEROID IMPACT--UPDATE"

Asteroid 2008 TC3 hit Earth this morning, Oct. 7th, and exploded in the atmosphere over northern Sudan. An infrasound array in Kenya recorded the impact. Dr. Peter Brown of the University of Western Ontario has inspected the data and he estimates that the asteroid hit at 0243 UTC with an energy between 1.1 and 2.1 kilotons of TNT. Most of the 3-meter-wide space rock should have been vaporized in the atmosphere with only small pieces reaching the ground as meteorites.

http://www.spaceweather.com/swpod200...map_strip2.jpg
Image credit: Peter Brown, University of Western Ontario

No pictures of the fireball have been submitted; the impact occurred in a remote area with few and possibly no onlookers capable of recording the event. So far, the only report of a visual sighting comes from Jacob Kuiper, General Aviation meteorologist at the National Weather Service in the Netherlands:

"Half an hour before the predicted impact of asteroid 2008 TC3, I informed an official of Air-France-KLM at Amsterdam airport about the possibility that crews of their airliners in the vicinity of impact would have a chance to see a fireball. And it was a success! I have received confirmation that a KLM airliner, roughly 750 nautical miles southwest of the predicted atmospheric impact position, has observed a short flash just before the expected impact time 0246 UTC. Because of the distance it was not a very large phenomenon, but still a confirmation that some bright meteor has been seen in the predicted direction. Projected on an infrared satellite-image of Meteosat-7 of 0300 UTC, I have indicated the position of the plane (+) and the predicted impact area in Sudan (0)."

2008 TC3 was discovered on Oct. 6th by astronomers using the Mt. Lemmon telescope in Arizona as part of the NASA-funded Catalina Sky Survey for near-Earth objects. Asteroids the size of 2008 TC3 hit Earth 5 to 10 times a year, but this is the first time one has been discovered before it hit.

pre-impact images: from Paolo Beltrame of CAST Astronomical Observatory, Talmassons, Italy; from Eric Allen of Observatoire du Cegep de Trois-Rivieres, Champlain, Québec; from Ernesto Guido et al. of Remanzacco Observatory, Italy; from S.Korotkiy and T.Kryachko of Kazan State University Astrotel observatory, Russia;

[cheesehead]

An example of what else is out there:

Another rock, smaller than 2008 TC3, just whizzed by. Its observations and calculated orbit (geocentric hyperbola, not heliocentric ellipse) elements can be seen at http://home.gwi.net/~pluto/mpecs/fastball.htm.
Closest distance to Earth was less than 4000 miles above the surface. Its brightness (or, lack thereof) implies that it was 1/3.6 as wide as ~3-meter-wide 2008 TC3, assuming it had a similar type of surface, or, as one guy put it:

"It may be the first object found so small you could actually carry it in a pickup truck."

(I don't intend to keep reporting stuff like this. It's just handy for comparison, and apparently the smallest object found so far by NEO hunters.)

[cheesehead]

Satellite photos of asteroid 2008 TC3's atmospheric entry and explosion:

http://www.eumetsat.int/Home/Main/Me...es/707785?l=en

Note comparison of visual flash and infrared image positions at bottom.

[Xyzzy]

http://news.yahoo.com/s/space/200810...lcaughtonvideo

[Spherical Cow]

Here is an interesting local article about the discoverer of the NEO
that vaporized in the atmosphere. Turns out he is not a degreed astronomer,
and has two other part-time, non-astronomy jobs. Note also in the article
that during those hectic hours between discovery and burn-up, the first
prediction that the object would hit the atmosphere came from an amateur.

http://www.azstarnet.com/allheadlines/264185.php

Norm