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(meteorobs) Excerpts from "CCNet 99/2001 - 10 September 2001"
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet 99/2001 - 10 September 2001
Date: Mon, 10 Sep 2001 12:48:06 +0100
CCNet 99/2001 - 10 September 2001
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(1) NASA SPACECRAFT TO FLY NEAR COMET
AP, 9 September 2001
[...]
(4) NEW OBSERVATIONS OF SUN ADD TO SPLIT OVER BIRTH OF PLANETS
The New York Times, 7 September 2001
(5) SOME OLD TALE OF AN ASTEROID: 2001 PM9
Andrea Milani
(6) FEELINGS OF AN AMATEUR OBSERVER OF NEAS
Jaime Nomen
[...]
(10) NEW PREPRINT ON TUNGUSKA
Luigi Foschini <foschini@tesre.bo.cnrdot it>
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(1) NASA SPACECRAFT TO FLY NEAR COMET
>From AP, 9 September 2001
http://dailynews.yahoo.com/h/ap/20010909/sc/comet_close_up_1.html
By ANDREW BRIDGES, AP Science Writer
PASADENA, Calif. (AP) - A battered NASA (news - web sites) spacecraft will
attempt to fly within 1,240 miles of the heart of a comet this month to give
scientists only their second glimpse of the dark heart of a glowing space
snowball.
The Deep Space 1 spacecraft will swoop past the comet Borrelly on Sept. 22,
snapping up to 32 black-and-white images of its nucleus.
If it succeeds in sending back close-up images of the nucleus during its
approach - and the odds are slim - it will be the first to examine the dark
yet dynamic core of a comet since the Giotto spacecraft flew past Halley in
1986.
``We expect to see an irregularly shaped, black potato spewing fountains of
gas and dust,'' said Donald Yeomans, a comet expert at the National
Aeronautics and Space Administration's Jet Propulsion Laboratory.
The flyby is anything but a sure thing for the spacecraft, which is on its
swan song assignment.
``There is a very real chance none of this is going to work,'' said Marc
Rayman, the mission's project manager at JPL.
``Deep Space 1 is flying on duct tape and good wishes,'' he said.
The probe was launched in October 1998 and completed its main mission of
testing a suite of a dozen innovative technologies a year later.
Shortly thereafter, however, it lost use of its navigational camera.
Engineers fashioned a replacement by reprogramming the probe's science
camera with hastily written software.
But it continues to run into problems, most recently last month when it lost
its orientation in space. And its supply of hydrazine fuel is dwindling,
leaving little for maneuvering.
NASA will turn off the spacecraft in late November, but scientists hope to
use data from the Borrelly flyby to plan for four other NASA missions
scheduled to fly past comets in the next few years.
``The little we know about comets is that they are really individual beasts
and that probably no two comets are alike,'' said Joseph Ververka, a Cornell
University professor of astronomy and principal investigator on the Comet
Nucleus Tour, or CONTOUR, mission to study at least two comets at close
range.
While comets are celebrated for how brilliantly they shine, at their heart
they are thought to be cloaked in a pitch black crust. When they swing close
to the sun, the heat boils off the mix of dust and ice that lies beneath.
When illuminated by the sun, that vaporized material glows brightly, giving
comets their distinctive head, or coma.
In Borrelly's case, the coma is as big as the Earth, dwarfing a nucleus
thought to be just 5 miles long and perhaps half as wide.
That means NASA scientists will have to guess about pointing the
spacecraft's camera and setting its exposure, because they won't know
exactly where or how bright the nucleus will be.
"We make our best estimate and then plunge into the coma," Rayman said.
The closest nucleus images will be taken from about 4,960 miles away, but
other instruments will continue gathering information as the craft nears the
nucleus.
Borrelly may well mean the death of Deep Space 1. Debris will batter the
spacecraft as it flies past the comet at a relative velocity of 36,900 mph.
At that speed, particles no larger than a human hair is thick can damage the
probe or send it spinning.
But NASA officials say the flyby is icing on the cake for the $152 million
Deep Space 1 mission. The flyby cost an additional $12 million.
"That's nothing compared to the cost of building a new spacecraft," said
Paul Hertz, the Deep Space 1 program executive at NASA headquarters.
On the Net:
Deep Space 1: http://nmp.jpl.nasadot gov/ds1/index.html
Copyright 2001 Associated Press
============================
* LETTERS TO THE MODERATOR *
============================
(10) NEW PREPRINT ON TUNGUSKA
>From Luigi Foschini <foschini@tesre.bo.cnrdot it>
Dear Friends and Colleagues,
At the web page for Tunguska at the University of Bologna
(http://www-th.bo.infndot it/tunguska/), you can find now two more preprints
to download freely. They refer to the proceedings of the meetings CELMEC III
(Roma, Italy, June 2001) and METEOROIDS 2001 (Kiruna, Sweden, August 2001).
Greetings,
Luigi
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