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(meteorobs) Excerpts from "CCNet 13/2001 - 26 January 2001"
Several items of interest to meteor enthusiasts in this issue of CCNet.
Note the attempt to redefine meteoric nomenclature ("asteroid" vs. "meteoroid"
vs. "micrometeoroid"). This is from a "meteoritist" (meteoriticist?), based
purely on meteoritical criteria. Quite different from the criteria I understand
meteoricists generally to apply, e.g., any particle that maintains a substantial
portion of its celestial velocity through impact is too large to be a meteoroid;
any particle which fails to produce a meteor trail detectable by ground-based
radar is too small to be a meteoroid - and so is a micrometeoroid.
Clear skies!
Lew Gramer
------- Forwarded Message
From: Benny Peiser <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 26 January 2001
Date: Fri, 26 Jan 2001 11:06:51 -0000
CCNet 13/2001 - 26 January 2001
------------------------------
(1) NIGHT SKY SHOW LIKELY A METEOR
Ron Baalke <baalke@jpl.nasadot gov>
(2) BRIEFINGS AND LIVE FEED SET FOR FIRST ASTEROID TOUCHDOWN
NASANews@hq.nasadot gov
(3) HOW TO BECOME A CRATER RATER
Andrew Yee <ayee@nova.astro.utorontodot ca>
[...]
(7) ADDING THE 'OID'
Matthew Genge <M.Genge@nhm.acdot uk>
[...]
======================================================================
(1) NIGHT SKY SHOW LIKELY A METEOR
>From Ron Baalke <baalke@jpl.nasadot gov>
>From Anchorage Daily News, 24 January 2001
http://www.adn.com/search/story/0,2392,232667,00.html
Night sky show likely a meteor
SPECTACLE: The FAA and the troopers received calls about a greenish-white
light.
By Liz Ruskin
Sandra Lemke and her daughter were driving home Monday evening, near the
Huffman Road exit of the Seward Highway, when something bright lighted up
the night sky.
"It streaked across the sky, with chunks kind of breaking off and then
burning out," she said. "It was bigger than anything I've ever seen before."
It was about 75 degrees above the horizon, she said, and traveled east to
west. Her teenager was awestruck. "Oh Mom, what was that?" she asked.
Lemke said she thought it might be space junk falling into the Earth's
atmosphere. She'd read that the Russian space station Mir was having
problems. Maybe a chunk of it fell off.
Scott Johnson, a spokesman for the Air Force Space Command in Colorado
Springs, Colo., said it was probably a meteor. He said he hadn't been
notified of any man-made space debris falling at that hour.
The Lemkes weren't the only ones floored by the spectacle. The Federal
Aviation Administration got two calls Monday night from people in the
Glennallen area who both reported a greenish-white flash. Both callers said
it occurred at 8:20 p.m. Lemke said her dashboard clock read 8:27 p.m.
No aviation accidents or overdue flights had been reported to the FAA that
evening, according to the agency's operations center. The Alaska State
Troopers in Glennallen took a similar report.
Karen Engstrom and her 9-year-old daughter were walking their dog near
Anchorage's University Lake when they saw it. "It lit up the sky," she said.
"It was like fireworks."
It had a beautiful tail and seemed so close it looked like it was landing in
the inlet, she said.
Her daughter made a wish.
Engstrom figured it was a meteor. "Either that or a jet engine landing in
someone's bedroom," she said.
A meteor is a streak of light across the sky, and especially bright ones are
called fireballs. They are caused by naturally occurring space debris,
usually ranging in size from a grain of sand to a pebble. The particles
hurtle easily through the vacuum of space and then plow into the Earth's
thick atmosphere. The friction of the air causes them to vaporize in a
white-hot streak.
Because the debris hits the atmosphere traveling to 45 miles per second, an
object the size of a grain of rice can produce a mile-long tail.
Fireballs, because of their brightness and sudden appearance, give the
illusion of closeness. Airline pilots have swerved for meteors that were
actually 100 miles away, according to Sky and Telescope magazine.
Sometimes fireball fragments fall to Earth and are recovered, as happened
last year in British Columbia. That fireball, which exploded in the night
sky on Jan. 18, was witness from Juneau to the Yukon.
Whatever she saw Monday night, Lemke said, it was amazing. She wanted to
honk her horn and ask other drivers if they saw it, too. "I've lived in
Alaska for 22 years and it was just the most interesting thing I've ever
seen," she said.
Copyright 2001, Anchorage Daily News
======================================================================
(2) BRIEFINGS AND LIVE FEED SET FOR FIRST ASTEROID TOUCHDOWN
>From NASANews@hq.nasadot gov
Donald Savage
Headquarters, Washington, DC January 25, 2001
(Phone: 202/358-1547)
Helen Worth
Johns Hopkins University Applied Physics Laboratory, Laurel, MD
(Phone: 240/228-5113)
NOTE TO EDITORS: N01-05
BRIEFINGS AND LIVE FEED SET FOR FIRST ASTEROID TOUCHDOWN
On Feb. 12, NASA makes history when mission controllers attempt to bring a
spacecraft down to the surface of an asteroid for the first time.
Controllers will send commands to the NEAR Shoemaker spacecraft to initiate
a four-hour series of engine burns designed to set the spacecraft down
gently on the asteroid Eros at about 3:01
p.m. EST.
The target site is on a saddle-shaped area known as Himeros on the
Manhattan-sized asteroid. The goal is to obtain high-resolution imagery as
NEAR Shoemaker, which has completed its one-year orbital mission of Eros,
slowly drops to the surface.
A media briefing to discuss the mission's science results and the details of
the descent to the surface of Eros is set for 1 p.m. EST, Wednesday, Jan.
31, in the James E. Webb Auditorium at NASA Headquarters, 300 E St. SW,
Washington, DC. The briefing will be carried live on NASA Television with
question-and-answer capability for reporters at participating NASA Centers.
Speakers for the briefing will be:
- - Dr. Edward Weiler, Associate Administrator for Space Science,
NASA Headquarters
- - Dr. Andrew Cheng, NEAR Project Scientist, The Johns Hopkins
University Applied Physics Laboratory (APL), Laurel, MD
- - Dr. Mark Robinson, Imaging Team member, Northwestern
University, Evanston, IL
- - Dr. Jessica Sunshine, Staff Scientist, Science Applications
International Corp., Chantilly, VA
- - Dr. Robert Farquhar, NEAR Mission Director, APL
On Monday, Feb. 12, 2001, "Descent to Eros" events will be held at the
Applied Physics Laboratory's Kossiakoff Center, in Laurel, MD. Media
interested in covering the descent activities at APL should contact Helen
Worth, APL Public Affairs Office.
A brief summary of the Feb. 12 activities are:
- - 12:30 to 1:30 p.m. EST -- Recap of the mission
- - 1:45 to 3:30 p.m. EST -- Descent Activities from the NEAR
Mission Operations Center (broadcast live on satellite).
On Wednesday, Feb. 14, a press conference is scheduled at 1 p.m. EST in
APL's Kossiakoff Center to discuss details of the landing. Because NEAR was
not designed to land, there is very
little chance the spacecraft will continue to operate after it reaches the
surface of Eros.
Due to the expected launch of the space shuttle mission in February, live
coverage of the descent-day activities on Feb. 12 and the post-mission
briefing on Feb. 14 will not be broadcast on NASA TV, but will be available
on a separate satellite. Details regarding those two events, including
updated satellite information, will be provided early next month.
NASA TV is broadcast on GE-2, transponder 9C, C-Band, located at 85 degrees
West longitude. The frequency is 3880.0 MHz. Polarization is vertical and
audio is monaural at 6.8 MHz.
======================================================================
(3) HOW TO BECOME A CRATER RATER
>From Andrew Yee <ayee@nova.astro.utorontodot ca>
[Extracted from ScienceNOW, AAAS.]
Thursday, 25 January 2001, 7:00 PM
How to Become a Crater Rater
By MITCHELL LESLIE
Here's a way to mark the year 2001 -- and take part in your own space
odyssey -- without leaving your desk. At a new Web site, you can become a
"clickworker" who helps planetary scientists at NASA's Ames Research Center
in California. After completing the site's short tutorial, you're ready to
scrutinize decades-old photos snapped by the Viking orbiters and classify
martian craters as fresh, degraded, or "ghost."
Crater data could help answer questions such as how fast the surface of Mars
ages and what causes it to change. But scientists and grad students now
spend many tedious months classifying the splotches. The Clickworkers pilot
project should show the level of interest in this kind of work and whether
people with minimal training can perform it accurately, says NASA knowledge
engineer Bob Kanefsky.
So far, so good: Since its 17 November launch, Mars Clickworkers has chalked
up more than 200,000 crater identifications. And collectively, the amateurs
seem to be doing almost as well at crater identification as expert planetary
geologists, Kanefsky says. If that continues, the project may expand to
newer, higher resolution images from the Mars Global Surveyor.
* Mars Clickworkers
http://clickworkers.arc.nasadot gov/top
Copyright ) 2001 by the American Association for the Advancement of Science.
============================
* LETTERS TO THE MODERATOR *
============================
(7) ADDING THE 'OID'
>From Matthew Genge <M.Genge@nhm.acdot uk>
Scientists love terminology, its one of these subjects that can give us
hours of harmless fun arguing with each other without anyone feeling
particularly put out afterwards. The whole of this taxonomy and
classification business is all about putting circular pegs in square pigeon
holes to try and work out how the pegs relate to each other.
In CCNET (25th Jan, 2001) Duncan Steel quite rightly corrects the use of
Meteor in connection with a meteorite and points out that meteoroid is the
best term to use, 'oid' of course meaning 'a thingy-like thing'. The problem
is always where do you draw the arbitary line between the thingy and its
thing. Probably the best place for a lower limit to meteoroid is 1 mm rather
than 100 microns suggested by Duncan since micrometeorites up to a mm can be
recovered from Antarctic ice. Objects between 1 mm and a few centimetres
usually being completely destroyed during atmospheric entry and larger
objects, if tough enough, reaching the surface to produce meteorites.
A useful upper limit for meteoroid is probably given by the largest known
meteorites, i.e. the Cape York shower at about 70 tonnes of iron in total.
Which taking ~90% mass loss during atmospheric entry suggests preatmospheric
sizes of around a hundred cubic metres. Close to the size suggested by
Duncan which is roughly equivalent to the minimum size of crater-forming
projectile.
Personally I'm more concerned that 'asteroid' is rather an inappropriate
name for several billion tonnes of rock and metal that's definitely not a
'star-like thingy', but then I'm a meteoritist.
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