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(meteorobs) Excerpt from "CCNet, 38/2000 - 23 March 2000"
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 23 March 2000
Date: Thu, 23 Mar 2000 10:44:42 -0500 (EST)
CCNet, 38/2000 - 23 March 2000
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[...]
(8) IMPACT CRATERS IN 3D
D. Wallis et al., UNIVERSITY OF KENT
(9) JAPANESE CONTRIBUTION TO METEOROID & SPACE DEBRIS MEASUREMENT
H. Yano, INST SPACE & ASTRONAUT SCI
[...]
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(8) IMPACT CRATERS IN 3D
D. Wallis*), C.J. Solomon, L. Kay: Use of Scanning Electron Microscopy=20
for three dimensional stereo analysis of impact craters and modelling=20
with Zernike polynomials. ADVANCES IN SPACE RESEARCH, 1999, Vol.25,=20
No.2, pp.339-344
*) UNIVERSITY OF KENT,UNIT SPACE SCI & ASTROPHYS,CANTERBURY CT2=20
7NR,KENT,ENGLAND
Examples will be presented to demonstrate the use of a Scanning=20
Electron Microscope to obtain detailed measurements of hypervelocity=20
impact craters and to obtain the shapes of craters in three dimensions=20
by comparing stereo pairs. The depth of each crater is sampled at=20
approximately 5000 points and the data is fitted using a set of=20
polynomials orthogonal over a unit disc ( the Zernike polynomials). The =
specific application to be presented is the study of groups of craters=20
produced under identical impact conditions by firing a quantity of=20
projectiles as buckshot from a light gas gun. Analysis of the Zernike=20
polynomial spectrum of the crater shapes will show quantitatively the=20
variations in crater shapes, both within groups of identical craters=20
and between groups corresponding to different impact conditions. In=20
this way the potential of the method for inferring properties of=20
impactors will be assessed, with the aim of applying the method to=20
obtain velocity and density information from craters in retrieved=20
space-exposed surfaces. (C) 1999 COSPAR. Published by Elsevier Science=20
Ltd.
=================================================================
(9) JAPANESE CONTRIBUTION TO METEOROID & SPACE DEBRIS MEASUREMENT
H. Yano: Japanese contribution to in-situ meteoroid and debris=20
measurement in the near Earth space. EARTH PLANETS AND SPACE, 1999,=20
Vol.51, No.11, pp.1233-1246
INST SPACE & ASTRONAUT SCI,PLANETARY SCI DIV,3-1-1=20
YOSHINODAI,SAGAMIHARA,KANAGAWA 229851,JAPAN
This paper reviews major results of present studies and recent=20
developments for future missions in the Japanese space program=20
regarding in-situ measurement and collection of micrometeoroids
and orbital debris in the near Earth space. Japan's contribution in=20
this area began with the post flight impact analysis of the Space=20
Flyer Unit (SFU) satellite which was returned to Earth in 1996 after=20
10-month exposure in space. Despite a decade later than similar=20
efforts first conducted in the USA and Europe, it resulted in a=20
record of over 700 hypervelocity impact signatures, which now forms=20
the nation's first database of real space impacts being open to=20
public in the Internet. Together with laboratory impact tests, both=20
morphological and elemental analyses of the impact craters yielded=20
new insights of the meteoroid to debris ratio as well as flux=20
variation compared with the previous spacecraft. The next step was a=20
passive aerogel exposure in the STS-85 shuttle mission in 1997. No=20
hypervelocity impact was found there but its experience has been=20
incorporated for designing a microparticle collector to be on-board=20
the Japan Experiment Module-Exposed Facility of the International=20
Space Station. All of such ''passive'' collection of micro-impact=20
features, however, still leave the significant uncertainty in the=20
quest of their origins. Therefore an aerogel-based ''hybrid'' dust=20
collector and detector (HD-CAD) is currently under the development.=20
It measures time of impact and deduces impactors' orbital and=20
physical parameters by detecting impact flash while still capturing=20
them intact. The system is suitable for both (1) sample return=20
missions in LEO as well as to parent bodies of meteoroids, i.e.,=20
comets and asteroids, and (2) one-way mission to where the thermal=20
and plasma environment is such that impact induced plasma detectors=20
may suffer from significant noise, e.g., a Mercury orbiter and a=20
solar probe. Together with unambiguous dust samples from a comet by=20
STARDUST and an asteroid by MUSES-C as references, the HD-CAD in the=20
LEO will be able to deduce the accretion rates of the cometary and=20
asteroidal dust grains on the Earth. Copyright 2000, Institute for=20
Scientific Information Inc.
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THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
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