PLEASE NOTE:


*

CCNet DIGEST, 22 June 1999
--------------------------


(1) ASTEROID HUNTERS BRING OLDIE-BUT-GOODIE INTO NEW AGE
    Ron Baalke <baalke@ssd.jpl.nasa.gov>

(2) NEW IMPACT IMAGES FROM MARS
    James Whitehead <jwhitehe@unb.ca>

(3) ANOTHER ANSWER REGARDING IMPACT PROBABILITY CALCULATIONS
    Karri Muinonen <muinonen@cc.helsinki.fi>

(4) RISK PERCEPTION AND NEO INFORMATION
    Malcolm Miller <stellar2@actonline.com.au>

(5) BRITAIN SEEKS INTERNATIONAL COOPERATION IN ASTEROID SEARCH
    SPACEVIEWS, 18 June 1999

(6) A DISCOURSE ON 1997 XF11
    B.G. Marsden, Harvard-Smithsonian Center for Astrophysics

(7) THE JAPANESE SPACEGUARD TELESCOPES
    S. Isobe, NATIONAL ASTRONOMICAL OBSERVATORY

(8) FRENCH NEO SEARCH PROGRAMMES
    A. Bijaoui et al., OBSERVATORY COTE AZUR

(9) SPACE DEBRIS MEASUREMENTS IN JAPAN
    T. Takano et al., INST SPACE & ASTRONAUT SCI

(10) LIBRIS: DETECTING SMALL AND MEDIUM-SIZED SPACE DEBRIS
     J.C. Worms et al., EUROPEAN SPACE SCI COMM

(11) DETECTING METEOROIDS AND SMALL-SIZED SPACE DEBRIS
     N. McBride et al., UNIVERSITY OF KENT

(12) SECONDARY IMPACT GENERATED PARTICLES
     J.C. Mandeville et al., OFF NATL ETUD & RECH AEROSP

(13) HYPERVELOCITY IMPACTS IN LOW EARTH ORIBIT: COSMIC DUST VS SPACE DEBRIS
     G.A. Graham et al., OPEN UNIVERSITY


==================
(1) ASTEROID HUNTERS BRING OLDIE-BUT-GOODIE INTO NEW AGE

From Ron Baalke <baalke@ssd.jpl.nasa.gov>

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Contact: Jane Platt     (818) 354-0880

FOR IMMEDIATE RELEASE                          June 21, 1999

ASTEROID HUNTERS BRING OLDIE-BUT-GOODIE INTO NEW AGE

  NASA astronomers searching for asteroids headed toward Earth are
expanding their sky-watching repertoire by adding high-tech,
computerized electronic upgrades to the classic 1.2-meter-diameter
(48-inch) Oschin telescope atop Palomar Mountain near San Diego,
California.

  Right now, NASA's Near Earth Asteroid Tracking (NEAT) system uses a
fully automated charge-coupled device (CCD) camera mounted on a
1-meter-diameter (39-inch) telescope atop Mt. Haleakela on Maui, HI.
The U.S. Air Force operates the telescope.

  NEAT scientists will computerize the pointing system of the 1.2-meter
(48-inch) Oschin telescope, which currently uses a human operator
exclusively, and replace photographic plates with a modern electronic
camera.  The refurbished telescope will enable them to peer deeper into
the sky than they can from Haleakela - they'll see 20 percent farther,
and their field of view will be 10 times wider.

  "Imagine watching the Super Bowl on your 25-inch TV and then
switching to an 80-inch giant screen TV," said Dr. Steven Pravdo, NEAT
project manager and co-investigator.  "But in this case, it's even
better than the TV analogy because, with the wider field, we'll see
many more asteroids in each picture - those that would be on the
'sidelines' of other telescopes."

The NEAT-Oschin alliance got a test run on June 9 and 10, when Pravdo
and two other JPL astronomers, Dr. David Rabinowitz and Jeffrey
Schroeder, took the NEAT camera to the Oschin telescope.  They obtained
the first-ever electronic images from that venerable sky eye.

  "This experiment proved that the Oschin telescope will be a powerful
tool in our hunt for near-Earth objects," Pravdo said. "We'll spruce up
this gentle giant and put it to excellent use helping us find
asteroids,"

  "For ten years, I've dreamed and mapped out plans for adding
electronic detectors to this telescope," said Eleanor Helin, principal
investigator for NEAT, which has been operating since December 1995.
"We've been able to study only a fraction of the sky so far, and we've
been looking for ways to cover the entire sky."

  NASA's goal is to find all asteroids larger than 1 kilometer (0.6
mile) across within 10 years.  "This will achieve one-third of that
goal, with the remaining two-thirds filled by the Haleakela camera and
other viewing sites," Helin explained. "The Oschin telescope at Palomar
may become the premier finder of near-Earth objects in the world."

  It's estimated there are 1,000 to 2,000 asteroids larger than 1
kilometer (0.6 mile) that approach within 48 million kilometers (30
million miles) of Earth. Less than 20 percent have been detected so
far.  Although the vast majority are harmless and will never pose a
threat to Earth, scientists want to keep track of the tiny percentage
whose orbits could eventually put them on a collision course with
Earth.

  The Oschin telescope, operated by the California Institute of
Technology, Pasadena, CA, has served as a world-class telescope since
it was built in 1949.  Helin used the telescope to discover near-Earth
asteroids and comets from the late 1970s to the early 1990s.  The
instrument is currently completing the second of two sky surveys that
serve as a resource to astronomers worldwide. The Oschin telescope has
done yeoman's duty for astronomers through the years, but it has been
surpassed in many ways by newer, more advanced telescopes.
Nonetheless, it remains the telescope with the largest field of view.

  NASA will fund the Oschin upgrade, estimated to cost $300,000 to
$500,000, and Caltech will provide the use of the facility and the
infrastructure.  Within about two years, astrophysicists from Yale
University in New Haven, CT, may provide further high-tech upgrades to
maximize the potential of the Palomar telescope.

  Images gathered by NEAT using the Oschin telescope, along with
general information on NEAT, are available at the following web site:

  http://neat.jpl.nasa.gov/

Information on the Palomar Observatory is available at:

  http://astro.caltech.edu/observatories/palomar/public/

  The NEAT project is managed by JPL for NASA's Office of Space
Science, Washington, DC.  JPL is a division of Caltech.

======================
(2) NEW IMPACT IMAGES FROM MARS

From James Whitehead <jwhitehe@unb.ca>

Dear Benny,

I thought you may be interesting in disemminating the following BBC
impact-related story. Images can be found at the source at:
http://news.bbc.co.uk/hi/english/sci/tech/newsid_374000/374629.stm

From Mars with love
by BBC News Online Science Editor Dr David Whitehouse

It all goes to show that if you look hard enough at a craters,
mountain ranges and deserts you will see all kinds of interesting
shapes.

Some took that to absurd levels when they claimed that a mountain on
Mars was actually a "face" sculpted by a long-extinct civilisation.
This theory was shown to be nonsense last year with close-up images
of the mountain in question. At high resolution, there was certainly
no face. But now there is a heart. The new image, taken by the Mars
Global Surveyor spacecraft, shows a heart-shaped pit formed by
collapse within a straight-walled trough known geologically as a
graben. Graben are formed along fault lines when the crust of a
planet is stretched.

It lies on the eastern edge of the Alba Patera volcano in a region
called northern Tharsis. It is about 3.2 kilometres (two miles)
across. Another of the newly released images is of the curious "happy
face" that contains some large, windblown sand dunes.

It is in fact the crater Galle, 224 km (140 miles) across. But no
doubt some people, disappointed that the original face on Mars was
not real, will say it appears to have been constructed. What it
really shows is that Mars has a sense of humour.

-------------------------
Dr. James Whitehead
Department of Geology,
University of New Brunswick,
2, Bailey Drive,
Fredericton, N.B.
E3B 5A3
Canada
Tel: 506-453-4804
Fax: 506-453-5055
Email: impact@unb.ca

============================
(3) ANOTHER ANSWER REGARDING IMPACT PROBABILITY CALCULATIONS

From Karri Muinonen <muinonen@cc.helsinki.fi>

Dear Benny, Paul, Andrea, and Brian,

Paul gave a very good summary of target plane techniques for computing
the collision probability. Such techniques are used at Jet Propulsion
Laboratory (Paul together with Don Yeomans) and at Dipartimento di
Matematica, Universita di Pisa (Andrea together with Steve Chesley and
Giovanni Valsecchi in Rome).

Let me add a few words about our computational methods that are perhaps
more pragmatic (and harder to illustrate). The general starting point
is the probability density of the six orbital elements of the asteroid
specified at an epoch close to the observation dates and, desirably,
within the time span of the observations. This distribution of orbital
elements is established by the fact that there are always random errors
in even accurate astrometric observations (one hopes that the
systematic errors have been corrected for!). The probability density of
the orbital elements can be 'visualized' as a six-dimensional cloud
(with diffuse boundaries) of possible orbital elements.

In order to compute the collision probability, one must specify a time
window: the collision probability at a single moment in time is zero!
For example, for the AN10-Earth encounter in August 2039, I made use of
the time window August 4.0-11.0, just to be on the safe side. In this
case, the time window could be decreased to less than one hour in
August 7, 2039.

Now the computation of the collision probability requires the detailed
knowledge of what subregion of the aforedescribed six-dimensional cloud
of the orbital elements leads to a collision on the given time window.
Once that subregion is known (from, e.g., Monte Carlo computations),
the collision probability is equal to the 'probability mass' in that
region, the entire 'probability mass' of the cloud being equal to
unity. Applying this technique to the 2039 AN10-Earth encounter, I
obtained 1.9 x 10^(-9) for the collision probability.

There are numerous further details of how the computations proceed. In
what we call the linear approximation, the cloud of orbits can often be
described by a Gaussian probability density, significantly simplifying
the computations (as in the case of AN10). As for the Earth-AN10
encounter in 2039, the subregion of the cloud containing the colliding
orbits is a thin slice that cuts almost perpendicular to the very
elongated six-dimensional Gaussian probability density. In such a case,
the six-dimensional computation of the collision probability becomes
essentially one-dimensional, since the five remaining dimensions do not
make a difference (one can make use of the marginal probability density
along the 'line of variation' as Andrea, Steve, and Giovanni
successfully did).

In my computations, a collision within the time window corresponds to
an approach within the planetary radius. The 'key holes' for close
encounters are 'key holes' in the six-dimensional cloud of orbital
elements (just to emphasize, at an epoch close to the observations),
and the close encounters before the specified time window are
implicitly fully taken into account (in general, they must be analyzed
separately, and one must proceed in a 'timely' manner!).

Best wishes, Karri

===================
(4) RISK PERCEPTION AND NEO INFORMATION

From Malcolm Miller <stellar2@actonline.com.au>

Dear Benny,

The NEO and PHA discussion at present is mainly about risk perception,
which is a topic more suited to the social sciences, psychology,
sociology, anthropology, political science than the 'hard' physics of
orbital mechanics, impact dynamics, the cohesion of asteroids and
bolides, and the propagation of shocks and waves in air, water and
rock.  Does this mean that the astronomy/geophysics community should
'stick to their last' and let politicians and the media have all the
running, limiting their input to real observations and measurements?
It's a risky choice, since the political-public relations-media game is
played with different rules, well known to politicians and journalists,
but a virtual minefield  for scientists. The old dilemma about crying
'wolf'' arises, together with the difficulty, always evident in science
reporting, that people unfamiliar with the mores of science want black
and white certainty, and are unable to cope with the acknowledged
uncertainties in the most precise of measurements or calculations,
which are quite familiar to scientists.

What we must accept is that politicians and lay people generally will
never see things from the scientific viewpoint; indeed, I don't think
we would want them to do so.  What we can do is to produce documentary
evidence which is comprehensible to non-scientists and acceptable to the
specialised community.  Duncan Steel's book is an example of this; as far
as I know it has not been condemned by his peers, and has been fairly
widely read by non-scientists.  And of course Steel is not the first to
explain hypervelocity mega-impacts.  My first encounter with the impact
danger was in an article by J. E. Enever writen in 1966.

Suggestions that funding be found for Spaceguard-type instruments and
programs have to be approved by politicians in competition with all
kinds of other demands relating to our survival, including health,
food, pollution, storm and earthquake, most of which are more visible
and more immediate than any menace from space, a region which hardly
exists for most of the world's population. How can we ensure that
reasonable resources are given to what we believe is also a real
survival program?

Perhaps the best we can do is to produce observations, predictions, and
calculations of the highest possible level of excellence. If lengthy
peer reviews are seen as a serious delaying factor, we must devise ways
of giving a weighting or grading to announcements such as the discovery
of new objects which are only potentially hazardous, in such a simple
form that they can hardly be misunderstood by the readers of the most
sensational tabloids.

Malcolm Miller

==================
(5) BRITAIN SEEKS INTERNATIONAL COOPERATION IN ASTEROID SEARCH

From SPACEVIEWS, 18 June 1999
http://www.spaceviews.com/1999/06/18c.html

The British government would prefer to cooperate with other nations to
set up searches for near-Earth asteroids, rather than establish its own
program, the British science minister told Parliament June 15.

Speaking in the House of Lords, science minister Lord Sainsbury of
Turville told members that the preference of the government would be to
work with fellow European Space Agency countries on any near-Earth
object (NEO) detection programs.

"The Government take the potential threat of impact by near earth
objects very seriously, but we regard it as an issue where a common
international approach is essential," Sainsbury said.

Sainsbury was asked several times by members of the House of Lords if
it would be prudent for Britain to establish its own "Spaceguard"
program to search for NEOs, using such resources as the Armagh
Observatory in Northern Ireland. On each occasion Sainsbury declined to
show support for such a British-only effort.

"At the present moment, the Government have no plans to set up a
national spaceguard agency," he said, although a final decision would
wait until after the government reviewed reports from a recent NEO
conference in Italy. "Any additional work undertaken in the UK must
have benefit over and above that being taken internationally."

The debate in the House of Lords comes three months after a similar
debate in the other branch of Parliament, the House of Commons. At that
time, John Battle, the Minister for Energy and Industry, told members
the government would talk with British astronomers and other experts on
ways the UK could support NEO research.

Since the March debate in the House of Commons, two asteroids have been
discovered on trajectories which have small but non-zero probabilities
of hitting the Earth next century. Those discoveries have intensified
interest worldwide in continuing and expanding the search for other
NEOs.

Sainsbury said the British government does not consider the threat
posed by NEOs to be a "trivial matter" but rather one that calls for
cooperation. "Of all subjects which come before this House, this is one
in respect of which an international effort is the key," he said. "We
shall play our part in that rather than acting independently."

Copyright 1999, SpaceViews

===============
(6) A DISCOURSE ON 1997 XF11

B.G. Marsden: A discourse on 1997 XF11. Journal of The British
Interplanetary Society, vol. 52, 195-202, 1999

Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138

When routine computations showed the possibility that the asteroid
1997 XF11, by then under observation for three months, might be on a
near-collision course with the Earth in 2028, humanity was presented
with an ideal example of an "impact hazard". Although the situation
was presented to the astronomical community as a request for further
observations to clarify the issue, a clarification quickly
forthcoming, the widespread publicity surrounding the event was not
particularly welcome in the first place. This discussion highlights a
number of mistakes, made by many, in the way the situation was
handled. Those mistakes include, but are not restricted to, the
general failure to pay attention to the asteroid earlier and the
assumption that any danger would be restricted to 2028. During at
least one year about a decade later, the chance of an Earth impact by
1997 XF11 may actually have been as high as 1 in 100 thousand,
although the recognition of the 1990 observations makes it clear that
the Earth is safe from this object for the foreseeable future. Given
the recent fivefold increase in the rate of discovery of potentially
hazardous asteroids, the initial 1997 XF11 apathy suggests that a
real danger might not be noticed. Simple steps are set down to ensure
that this does not happen with future discoveries.

Copyright 1999, The British Interplanetary Society

======================
(7) THE JAPANESE SPACEGUARD TELESCOPES

S. Isobe: Japanese 0.5 m and 1.0 m telescopes to detect space debris
and near-earth asteroids. ADVANCES IN SPACE RESEARCH, 1999, Vol.23,
No.1, pp.33-35

NATIONAL ASTRONOMICAL OBSERVATORY,2-21-1 OSAWA,MITAKA,TOKYO 181,JAPAN

After our experimental activities of several years, our telescope
project to build telescopes for the detection and observation of space
debris and near-earth asteroids has been approved by the Science and
Technology Agency and the project was started from the fiscal year
1998. Two telescopes will be built : a 1.0 m telescope with a 3 degree
field of view and position resolution of 0.2 are second to observe
geosynchronous earth orbit (GEO) space debris larger than 20 - 30 cm
and near-earth objects (NEO) larger than 1.0 km, and a 0.5 m telescope
will be used for follow-up observations of GEO and NEO and for testing
observations of low earth orbit (LEO) space debris. The telescopes will
be in full operation around 2001. (C) 1999 COSPAR. Published by
Elsevier Science Ltd.

=================
(8) FRENCH NEO SEARCH PROGRAMMES

A. Bijaoui*), A. Maury, P. Oberti, B. Vandame, J.C. Venturino, F.
Alby: Detection of objects near the geostationary ring using a CCD
camera. ADVANCES IN SPACE RESEARCH, 1999, Vol.23, No.1, pp.37-44

*) OBSERVATORY COTE AZUR,BP 229,F-06304 NICE 4,FRANCE

A collaboration between the Observatoire de la Cote d'Azur (OCA) and
the Centre National d'Etudes Spatiales (CNES) started in 1996 for
detecting optically faint sources close to the geostationary ring using
the OCA Schmidt camera. After a first approach based on photographic
films we have installed a 2048 x 2048 CCD camera at the focus of the
telescope. An automated analysis method was developed. After
identifying all stellar trails on the CCD frames we subtract them after
a suitable modelization. The detection of the remaining objects takes
into account the noise variations due to the model defects. For each
CCD frame about two hundred point-like objects are identified. The
detection of possible space objects is achieved by matching the lists
of candidates obtained on three or more successive images. Few objects
are observed at a limiting magnitude-around 20. mie determine their
approximate orbits in order to allow follow up observations for each
object. A software allowing the user to process the images just after
the acquisition has been developed. A one year observational campaign
is foreseen in the near future. (C) 1999 COSPAR. Published by Elsevier
Science Ltd.

===============
(9) SPACE DEBRIS MEASUREMENTS IN JAPAN

T. Takano*), T. Tajima, T. Satoh, Y. Arimoto: Space debris measurements
in Japan. ADVANCES IN SPACE RESEARCH, 1999, Vol.23, No.1, pp.55-65

*) INST SPACE & ASTRONAUT SCI,3-1-1 YOSHINO DAI,SAGAMIHARA,KANAGAWA
   229851,JAPAN

This paper describes the present status of space debris measurements in
Japan, focusing on the recent achievements of existing systems and the
design of new systems. Issues concerning the Leonids meteoroid storm in
November 1998/99 will be also discussed. (C) 1999 COSPAR. Published by
Elsevier Science Ltd.

=============
(10) LIBRIS: DETECTING SMALL AND MEDIUM-SIZED SPACE DEBRIS

J.C. Worms*), O. Girard, A. Hauchecorne, K. Muinonen: LIBRIS: An
orbital imaging lidar for the detection of small to medium-sized debris
in low-Earth orbit. ADVANCES IN SPACE RESEARCH, 1999, Vol.23, No.1,
pp.67-70

*) EUROPEAN SPACE SCI COMM,PARC INNOVAT,BLVD SEBASTIEN BRANDT,F-
   67400 ILLKIRCH GRAFFENS,FRANCE

LIBRIS aims at detecting and locating orbital debris in the 0.1 mm - 1
cm size range, retrieving such parameters as distance at the time of
detection, trajectory parameters (incidence and  velocity) and
estimated size. It makes use of backscattered  lidar radiation and will
provide long-term information to improve cataloging of debris in
law-Earth orbit (LEO) and thus refine existing evolutionary debris
models. Knowledge about interplanetary dust particles (IDPs) will be
gained by discriminating between natural (micro-meteoroids) and
man-made debris in LEO by means of the retrieved orbital parameters.
(C) 1999 COSPAR. Published by Elsevier Science Ltd.

===============
(11) DETECTING METEOROIDS AND SMALL-SIZED SPACE DEBRIS

N. McBride*), S.F. Green, J.A.M. McDonnell: Meteoroids and small sized
debris in Low Earth Orbit and at 1 au: Results of recent modelling.
ADVANCES IN SPACE RESEARCH, 1999, Vol.23, No.1, pp.73-82

*) UNIVERSITY OF KENT,UNIT SPACE SCI & ASTROPHYS,SCH PHYS
   SCI,CANTERBURY CT2 7NR,KENT,ENGLAND

We present consolidated flux data from the Long Duration Exposure
Facility (LDEF) and develop an isotropic meteoroid model applicable to
predicting damage to the LDEF surfaces. The model is shown to work
well, and is used to derive the resultant component of orbital debris
incident on the LDEF east (ram) and west (wake) faces. Overall, orbital
debris dominates the measured fluxes at small sizes (aluminium
penetration depth F-max < 30 mu m) whereas meteoroids dominate above
this size (see also McDonnell et al., 1997). The east and west face
comparison shows that at least 2 distinct populations of debris exist
with different size distributions. Analysis of data from the European
Retrievable Carrier (EuReCa) shows the interplanetary meteoroid flux to
he biased towards the Earth-apex direction (in the measured size
regime). An enhanced meteoroid model is derived which is consistent
with both EuReCa and LDEF data, and which does not affect the debris
fluxes derived from LDEF data. (C) 1999 COSPAR. Published by Elsevier
Science Ltd.

=============
(12) SECONDARY IMPACT GENERATED PARTICLES

J.C. Mandeville, M. Rival, F. Alby: Secondary impact generated
particles: Implications for the orbital debris population. ADVANCES IN
SPACE RESEARCH, 1999, Vol.23, No.1, pp.89-94

*) OFF NATL ETUD & RECH AEROSP,DESP,2 AV E BELIN,F-31400
   TOULOUSE,FRANCE

Every time a debris or a meteoroid hits a part of a satellite in orbit,
a great amount of secondary particles is ejected in the neighborhood of
the impact site. This phenomenon is important for brittle materials,
such as used for solar generators. The secondary particles that do not
impact other parts of the spacecraft are added to the primary debris
population and increase the small debris flux. We present an ejecta
production model that gives the size and the velocity distribution of
ejected particles as a function of primary impact parameters. We derive
the parameters of all ejecta created during one orbital revolution of a
satellite. An orbital evolution program is used to extrapolate the
secondary debris position at later times. Preliminary results show that
spall fragments ejected at low velocities remain in the vicinity of the
parent satellite. The:, ejecta trajectories are similar and their
inclination is very close to those of the parent satellite. Their
orbital evolution depends mainly on the size of the debris and on the
altitude of the parent body: the smallest particles in low earth orbit
quickly reenter the earth atmosphere, while the largest spalls have a
very slow decay. The antagonistic action of debris production and
debris decay by drag leads to an equilibrium for particles within a
given size range. Quantitative results on densities and fluxes compared
to the primary debris population are presented for the peculiar case of
heliosynchronous orbits. (C) 1999 COSPAR. Published by Elsevier Science
Ltd.

=========
(13) HYPERVELOCITY IMPACTS IN LOW EARTH ORIBIT: COSMIC DUST VS SPACE DEBRIS

G.A. Graham*), A.T. Kearsley, M.M. Grady, I.P. Wright,
A.D. Griffiths, J.A.M. McDonnell: Hypervelocity impacts in low Earth
orbit: Cosmic dust versus space debris. ADVANCES IN SPACE RESEARCH,
1999, Vol.23, No.1, pp.95-100

*) OPEN UNIVERSITY,PSRI,MILTON KEYNES MK7 6AA,BUCKS,ENGLAND

The understanding of the micron-sized populations of natural
micrometeoroids and artificial space debris in low Earth orbit
has benefited considerably from the post-flight investigations of
retrieved surfaces from spacecraft, such as the Long Duration Exposure
Facility. The returned solar array from the Hubble Space Telescope has
added to this repository and has offered a further opportunity to
document these particles. 25 individual solar cells were specially
selected on the basis that they contained impact craters (diameter
100-1000 mu m) which had the most potential to retain impactor residue
chemistry. The solar cells were subject to a detailed investigation
using analytical scanning electron microscopy which identified 29
impact craters, the analysis of which identified 3 residues as
artificial in origin, 6 unclassified and 20 as natural in origin. The
limited number of unclassified residues identified indicates that the
methods of analysis employed in this investigation are a significant
step forward for such studies and, if employed on a greater number of
samples, will improve the calculations of the time-integrated flux
rates for micrometeoroids and space debris in the low Earth orbit
environment. Notwithstanding the small sample set examined, the
observed chemical classification of the impact residues in terms of
micrometeoroid to space debris (in the particle size range 8-80 mu m)
corresponds well to the flux model that predicts the dominance of
natural particles. (C)  1999 COSPAR. Published by Elsevier Science Ltd.

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*

A FEW SMALL ODDS AND ENDS

From Bob Kobres (06/22/99/) <bkobres@arches.uga.edu>



CCCMENU CCC for 1999

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