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(meteorobs) Excerpts from "CCNet 3/2001 - 5 January 2001"
------- Forwarded Message
From: Benny Peiser <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet 5 January 2001
Date: Fri, 5 Jan 2001 11:43:17 -0000
CCNet 3/2001 - 5 January 2001
-----------------------------
"Exploding meteors bombarding the Earth from space could be mistaken
for nuclear bomb tests, say seismologists of the Royal Netherlands
Meteorological Institute. This could present problems for monitoring
theComprehensive Nuclear Test Ban Treaty (CTBT), which aims to halt the
testing of all nuclear weapons."
-- Philip Ball, Nature, 5 January 2001
(1) METEORS COME IN WITH A BANG
Andrew Yee <ayee@nova.astro.utorontodot ca>
[...]
(3) NASA CONSIDERS DISCOVERY MISSION PROPOSALS:
FLIGHTS TO CERES & VESTA UNDER CONSIDERATION
NASANews@hq.nasadot gov=20
[...]
(11) METEOROID IMPACT FLASHES ON THE MOON
L.R.B. Rubio et al.
(12) HYPERVELOCITY IMPACTS FROM THE 1999 LUNAR LEONIDS
L.R.B. Rubio et al.
[...]
(17) SEARCHING FOR SMALL SPACE DEBRIS
W. Flury et al.
[...]
====================================
(1) METEORS COME IN WITH A BANG
>From Andrew Yee <ayee@nova.astro.utorontodot ca>
>From Nature Science Update, 5 January 2001
[http://helix.nature.com/nsu/010104/010104-8.html]
Friday, 5 January 2001
=20
Meteors come in with a bang
By PHILIP BALL
Exploding meteors bombarding the Earth from space could be mistaken for
nuclear bomb tests, say seismologists of the Royal Netherlands
Meteorological Institute. This could present problems for monitoring =
the
Comprehensive Nuclear Test Ban Treaty (CTBT), which aims to halt the =
testing
of all nuclear weapons.
L=E4slo Evers and Hein Haak detected a sonic boom from a meteor =
explosion with
an instrument similar to those currently under construction for =
verification
of the CTBT.
The explosion released energy equivalent to 1.5 kilotons of TNT, the
researchers calculate. This is as big a bang as was made by several of =
the
US nuclear tests of the early 1960s, and at the lower end of the =
estimated
size of the Pakistani tests of 1998.
The future of the CTBT has been under a cloud since the US Senate =
decided
not to ratify it in 1999. But many other nations have already done so, =
and
plans are afoot for global detection systems that will alert the
international community to secret nuclear weapons tests.=20
Underground tests send out shock waves that seismic monitoring stations
designed for earthquake detection can pick up. And atmospheric tests =
create
a kind of low-frequency ('infrasound') sonic=20
boom which highly sensitive air-pressure meters (microbarometers) can
register. A worldwide network of 60 infrasound detectors is being built =
for
this purpose.
Situated near the village of Deelen in the Netherlands, the instrument =
Evers
and Haak used is not designated for CTBT verification -- it is =
primarily a
meteorological device. But in November 1999, it registered a most =
unusual
event.
At around four o'clock in the morning of the 8th November, a few early
risers in Germany and the Netherlands saw a flash in the dark sky above
northern Germany. A meteor -- a small chunk of space rock plunging =
through
the atmosphere -- had exploded at a height of about 20 kilometres.=20
The event was similar to a better-documented one that occurred in the =
middle
of the afternoon over New Zealand the previous July. On that occasion,
observers reported "a bright light, exactly like a flare", variously
described as blue, red, orange or yellow. It was followed by a loud =
boom,
and left behind a puff of brown smoke.
About one meteor detonates in the atmosphere every week. Most go unseen =
by
human eyes, as they break apart very high in the sky. Only rarely does =
one
strike or explode close to the planet's surface, such as the object =
that
levelled trees over hundreds of square kilometres in Tunguska, Siberia, =
in
1908.
That event aside, the height of these explosions usually hides their
tremendous ferocity. The explosion of November 1999 showed up on the =
Deelen
microbarometer as an infrasound blip slightly greater than the =
background
noise generated by ocean waves, which create a constant barrage of =
small
atmospheric booms called microbaroms.=20
Reported in the journal Geophysical Research Letters [1], Evers and =
Haak's
research highlights how crucial it will be for an infrasound network to =
be
able to distinguish between meteor explosions and genuine nuclear =
blasts.=20
[1] Evers, L. G. & Haak, H. W. Listening to sounds from an exploding =
meteor
and oceanic waves. Geophysical Research Letters 28, 41-44 (2001).=20
=A9 Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE
====================================
(3) NASA CONSIDERS DISCOVERY MISSION PROPOSALS:
FLIGHTS TO CERES & VESTA UNDER CONSIDERATION
>From NASANews@hq.nasadot gov=20
Don Savage
Headquarters, Washington, DC January 4, 2001
(Phone: 202/358-1727)
RELEASE: 01-01
NASA CONSIDERS DISCOVERY MISSION PROPOSALS
It's a difficult decision: With about $300 million to spend, should =
NASA buy
a spacecraft that could find Earth-sized planets around nearby stars? =
What
about a mission that could peer deep=20
inside Jupiter's gaseous atmosphere? Or should the agency go with a =
mission
to orbit the two largest asteroids in the solar system?=20
The answer to that question will have to wait about a year. In the =
first
step of a two-step process, NASA's Office of Space Science selected =
three
proposals for detailed study as candidates for the next mission in the
agency's Discovery Program of lower cost, highly focused, =
rapid-development
scientific spacecraft.=20
"The diversity of science represented in these three mission proposals =
is
outstanding. NASA will have its hands full picking only one for =
flight,"
said Dr. Jay Bergstralh, acting Director of Solar System Exploration at =
NASA
Headquarters, Washington, DC.=20
The selected proposals were judged to have the best science value among =
26
proposals submitted to NASA last August. Each selected team will =
receive
$450,000 to conduct a four-month implementation-feasibility study =
focused on
cost, management and technical plans, including educational outreach =
and
small business involvement.=20
Following detailed mission concept studies, NASA intends to select one =
of
the three proposals late in 2001 for full development. The mission =
should be
launched around 2005 or 2006.
NASA has also decided to fund American participation in a mission to =
Mars
being flown by another nation. In this "Mission of Opportunity" NASA =
will
contribute to seismology, meteorology and=20
geodesy (to measure the size and shape of the planet) experiments on =
the
French-led NetLander Mission, scheduled for launch in 2007. The Mission =
of
Opportunity team will receive $250,000 to conduct its feasibility =
study.
The selected Discovery and Mission of Opportunity proposals are:
* The Kepler mission is a space telescope specifically designed to =
detect
Earth-sized planets around stars in the Sun's neighborhood of the =
galaxy. By
monitoring 100,000 stars over a=20
four-year mission, Kepler could detect up to 500 Earth-sized planets =
and up
to 1000 Jupiter-sized planets. Dr. William Borucki of NASA's Ames =
Research
Center at Moffet Field, CA, would lead Kepler at a total cost to NASA =
of
$286 million.
* The Interior Structure and Internal Dynamical Evolution of Jupiter
(INSIDE Jupiter) mission is a Jupiter orbiter designed to observe and
measure processes occurring within the Jovian magnetosphere and =
atmosphere.
INSIDE Jupiter would determine the internal structure of the planet by
obtaining high resolution maps of the magnetic and gravity fields. Dr.
Edward J. Smith of the Jet Propulsion Laboratory in Pasadena, CA, would =
lead
INSIDE Jupiter at a total cost to NASA of $296 million.
* The Dawn mission intends to orbit Vesta and Ceres, two of the =
largest
asteroids in the solar system. According to current theories, the very
different properties of Vesta and Ceres are the result of the asteroids
being formed and evolving in different parts of the solar system. By
observing both asteroids with the same set of instruments, Dawn would =
probe
the early solar system as well as determine in detail the properties of =
each
asteroid. Dr. Christopher T. Russell of the University of California at =
Los
Angeles would lead Dawn at a total cost to NASA of $271 million.
* A U.S. contribution to the French-led NetLander mission will add =
unique
capabilities to each of the four landers and the orbiter which comprise =
the
mission. In 2007, NetLander will create the first science network on =
Mars to
study the planet's internal structure. The American contribution =
includes
short period seismometers and wind sensors on the landers, and a
high-resolution geodesy instrument on the orbiter. Dr. W. Bruce Banerdt =
of
the Jet Propulsion Laboratory will lead the U.S. contribution to =
NetLander
at a total cost to NASA of $35 million.
The Discovery Program is designed to provide frequent, low-cost access =
to
space for planetary missions and missions to search for planets around =
other
stars. The selected science missions must be ready for launch before
September 30, 2006, within the Discovery Program's cap on each =
mission's
cost to NASA of $299 million.=20
The Discovery Program is managed at NASA's Jet Propulsion Laboratory, a
division of the California Institute of Technology, Pasadena, for the =
Office
of Space Science, Washington, DC. More information on the Discovery =
Program
is available at: =20
http://discovery.nasadot gov/
====================================
(11) METEOROID IMPACT FLASHES ON THE MOON
Rubio LRB, Ortiz JL, Sada PV: Observation and interpretation of =
meteoroid
impact flashes on the moon
EARTH MOON AND PLANETS 82-3: 575-598 2000
The first unambiguous detection of meteoroids impacting the night side =
of
the Moon was obtained during the 1999 Leonid storm. Up to eight optical
flashes were recorded with CCD video cameras attached to small =
telescopes on
November 18, 1999. Six impacts were videotaped by at least two =
independent
observers at the same times and lunar locations, which is perhaps the
strongest evidence for their collisional nature. The flashes were =
clearly
above the noise and lasted for less than 0.02 s. Although previous
observational efforts did not succeed in detecting impact flashes,
additional candidates have been reported in the literature. The =
evidence
accumulated so far implies that small telescopes equipped with high =
speed
cameras can be used as a new tool for studying meteoroid streams, =
sporadic
meteoroids, and hypervelocity collisions. In this review we discuss the
various intervening parameters for detectability of flashes on the =
night
side of the Moon (geometrical effects, contamination by scattered light =
from
the day side, and properties of the meteoroids such as speed and flux =
of
particles). Particular emphasis is placed on the analysis of the
observations in order to derive relevant physical parameters such as
luminous efficiencies, impactor masses, and crater sizes. Some of these
parameters are of interest for constraining theoretical impact models. =
From
a simple analysis, it is possible to derive the mass distribution of =
the
impactors in the kg range. A more elaborate analysis of the data =
permits an
estimate of the fraction of kinetic energy converted to radiation =
(luminous
efficiency) if the meteoroid flux on the Moon is known. Applied to the =
1999
lunar Leonids, these methods yield a mass index of 1.6 +/- 0.1 and =
luminous
efficiencies of 2 x 10(-3) with an uncertainty of about one order of
magnitude. Predictions of visibility of the major annual meteor showers =
are
given for the next few years. These include the forthcoming 2001 Leonid
return, for which we estimate detection rates in the visible.
Addresses:
Rubio LRB, Inst Astrofis Canarias, Tenerife, Spain.
Inst Astrofis Canarias, Tenerife, Spain.
CSIC, Inst Astrofis Andalucia, Granada, Spain.
Univ Monterrey, Monterrey, Mexico.
Copyright =A9 2001 Institute for Scientific Information
====================================
(12) HYPERVELOCITY IMPACTS FROM THE 1999 LUNAR LEONIDS
Rubio LRB, Ortiz JL, Sada RV: Luminous efficiency in hypervelocity =
impacts
from the 1999 lunar Leonids
ASTROPHYSICAL JOURNAL 542: (1) L65-L68, Part 2 OCT 10 2000
An analysis of the optical flashes produced by Leonid meteoroids =
impacting
the Moon in 1999 November is carried out in order to estimate the =
fraction
of kinetic energy converted into radiation, the so-called luminous
efficiency eta. It is shown that the observational data are consistent =
with
luminous efficiencies of 2 x 10(-3) in the wavelength range of 400-900 =
nm
with an uncertainty of about 1 order of magnitude. This experimental =
value
of eta is significantly larger than previous estimates for meteoroids =
of
asteroidal composition based on numerical calculations and scaling laws =
from
laboratory collisions. According to our results, the luminous =
efficiency
might vary with mass, i.e., the smaller impactors converting less =
kinetic
energy into light and vice versa. A comparison with recent numerical
simulations for meteoroids of cometary composition is also carried out.
Addresses:
Rubio LRB, Inst Astrofis Canarias, Via Lactea, E-38200 La Laguna, =
Canary
Islands, Spain.
Inst Astrofis Canarias, E-38200 La Laguna, Canary Islands, Spain.
CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain.
Univ Monterrey, Dept Fis & Matemat, Monterrey 66238, Nuevo Leon, =
Mexico.
Copyright =A9 2001 Institute for Scientific Information
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