[meteorite-list] Rosetta gravity assist flyby

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon, 12 Nov 2007 23:53:25 -0600
Message-ID: <0eac01c825b9$825b2d10$c944e146_at_ATARIENGINE>

Hi, Larry, Doug, and other members
    of the Target Population,

    While my first reaction was to be pleased:

>There's something re-assuring about the notion
>that we could detect a "potential impactor,"
>even if we didn't immediately recognize that
>it's one of ours!

    I'm beginning to reconsider. The MPC Circular
was Nov. 8th, so the detection would seem to have
been the night of Nov. 7-8, or since that seems to be
cutting things close, perhaps Nov. 6-7. But the first
"we" knew of the potential event was Nov. 8th. The
flyby is 20:57 UT on Nov. 13th, which for the US
is the early morning hours of the 14th.

    That means that effectively there was 5.5 days
of lead time for a potential impact. When we thought
it was a small, dark (and hence unreflective) asteroid,
it was estimated to be a 20-meter object (instead of
a small shiny spacecraft) which, if it had stuck the
Earth's atmosphere, would not have survived the
encounter and would have been no threat. (Or not,
if stone, it's about 10,500 tons, with an airburst of
a trivial 150,000 tons of TNT.)

    It would interesting to know if 2007 VN84 was
detected because of its "brightness" or because of
its high proper motion. If it was because of brightness,
we would have 11 days of warning for a 40-meter
object, 23 days of warning for a 80-meter object,
47 days of warning for a 160-meter object...

   That last one, the 160-meter stone, weighs in at
5,120,000 tons, and I, for one, am willing to take
that seriously (75 MegaTons of TNT and a one-and-
a-half mile crater 1500 feet deep). OK, I've got 47
days. What do I do? Practically, I think the only
thing that I could do is to calculate exactly where
is a good place to watch the show when it hits.

    It's probably significant that the CSS (Catalina Sky
Survey) was the one to catch it; in 2005 they found
the greatest number of NEO's of all the searchers. Their
methodology, as I understand it, is based on detection
by large proper motion, but the object has to be bright
enough to be noticed first. A really "dim" object shifting
its relative position rapidly wouldn't get caught... until
it brightened.

    Our problem (as a species and civilization) is that
we're still in the phase of trying to find all those sneaky
potential impactors. We haven't been promoted to the
grade level where all we have to do is keep track of them
and roll out the laser cannons in case of emergency!

    In this event, however, we have encountered the first
known occasion where part of the problem fell under
the jurisdiction of the keeping-track department (you
know, the one we don't have yet). And, by pinpointing
that problem, I think we've made another advancement,
assuming we do something about getting that department.

Sterling K. Webb

----- Original Message -----
From: <lebofsky at lpl.arizona.edu>
To: "mexicodoug" <mexicodoug at aol.com>
Cc: <meteorite-list at meteoritecentral.com>
Sent: Monday, November 12, 2007 8:33 PM
Subject: Re: [meteorite-list] Rosetta gravity assist flyby

Hello Doug:

I take exception to your comments that this was either a screw-up or a
joke. These are hard-working dedicated people, most of whom I have known
for 20-30 years.

I do not know all of the details, but when a "discovery" is made, the
discoverers have access to a very large database of Small Solar System
Bodies (asteroids and comets). Generally, things in orbit around the Earth
have distinct enough orbits so that they are easily recognized. Not so for
objects in heliocentric orbits (orbiting the Sun). In this case, an object
was seen that appeared to be a Near-Earth Object that was about to make a
close approach to the Earth and for which the database did not have the
orbital elements. Thus, it was at first considered to be a new discovery.

There are nearly 500,000 known asteroids (many with poorly known orbits)
and about 5000 new ones are being discovered every month! Maintaining this
database is not an easy task.

Obviously, someone fairly quickly realized that this was not an asteroid,
but Rosetta, but not before the alert went out for astronomers to make
observations. The system worked!

What did not work, as was pointed out by the Minor Planet Center, was that
unless there is someone who is in a position to provide them with the
orbital elements of Rosetta, there is no way that they can put this into
their database. This is where the system failed. Actually it is impressive
that the Catalina Survey people did see this "incoming asteroid" and shows
how well they are covering the sky in order to locate any asteroids
heading toward the Earth.

However, Doug, Pluto and the IAU decision is another story that we should
discuss over beers sometime.

Larry Lebofsky

On Mon, November 12, 2007 6:51 pm, mexicodoug wrote:
> Hi Darren,
> It certainly was an actual screw-up by the IAU. The joke I meant was by
> Catalina Sky Survey, no matter what they say. You deserve a medal. Just
> tell us you didn't look in the back of the book (or leave a Google crumb
> path)! Clyde Tombaugh is is snickering in his grave at the foolish
> bureaucracy that was arrogant enough to strip a true astronomer of his
> life's crowning achievement to play word footsies...
> Best wishes,
> Doug.
> ----- Original Message -----
> From: "Darren Garrison" <cynapse at charter.net>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Monday, November 12, 2007 6:13 PM
> Subject: Re: [meteorite-list] Rosetta gravity assist flyby
>> On Fri, 9 Nov 2007 12:35:28 -0600, you wrote:
>>> Someone has a sense of humour, especially the flying couch comment !
>> Looks like it might have been an actual screw-up, not just a joke.
>> http://blogs.smh.com.au/sit/archives/2007/11/alarm_astronomers_in_a_spi
>> n_ov.html
>> http://www.space.com/businesstechnology/071112-technov-asteroid-mistake
>> .html
>> http://www.dailymail.co.uk/pages/live/articles/technology/technology.ht
>> ml?in_article_id=493152&in_page_id=1965
>> ______________________________________________
>> Meteorite-list mailing list
>> Meteorite-list at meteoritecentral.com
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