PLEASE NOTE:


*

CCNet DIGEST, 1 May 1998
------------------------

(1) NEW ORBIT CALCULATIONS BASED ON CHINESE ANCIENT COMETARY RECORDS
    H.N. Zhou et al., NANJING NORMAL UNIVERSITY

(2) DUNCAN STEEL ON ASTEROIDS, BUFFON & COMETS
    D.I. Steel, SPACEGUARD AUSTRALIA

(3) ROSETTA AHOY: HOW TO ANCHOR A SPACECRAFT ON A COMET
    N.I. Komle et al., AUSTRIAN ACADEMY OF SCIENCE

(4) COMPOSITION OF COMETARY DUST
    L. Kolokolova & K. Jockers, MAX PLANCK INSTITUT

(5) THE LAPLACIAN ORBIT DETERMINATION OF ASTEROIDS
    M.J. Sokolskaya, RUSSIAN ACADEMY OF SCIENCE

(6) THE DANGEROUS BORDER OF THE 5:2 MEAN MOTION RESONANCE
    Z. Knezevic et al., ASTRONOMICAL OBSERVATORY BELGRADE

(7) ESCAPE OF ASTEROIDS FROM THE HECUBA GAP
    T. Michtchenko & S. Ferraz Mello, UNIVERSITY OF SAO PAULO

(8) REQUIRED ACCURACY OF THE MOTION THEORIES OF PERTURBING BODIES
    E.D. Kuznetsov, URAL STATE UNIVERSITY

(9) MONITORING CHIRON'S BRIGHTNESS
    D. Lazzaro et al., DEPARTMENT OF ASTROPHYSICS, RIO JANEIRO

(10) JOINT ASTEROID OBSERVATIONS BY ESO & KHARKIV OBSERVATORIES
     V.G. Shevchenko et al., ASTRONOMICAL OBSERVATORY UPPSALA

(11) A NEW MODEL TO SIMULATE IMPACT BREAKUP
     A. Cordelli & P. Farinella, UNIVERSITY OF PISA

=========================
(1) NEW ORBIT CALCULATIONS BASED ON CHINESE ANCIENT COMETARY RECORDS

H.N. Zhou*), W.F. Zhuang & Y. Wang: New reductions of orbits based upon
Chinese ancient cometary records. PLANETARY AND SPACE SCIENCE, 1997,
Vol.45, No.12, pp.1551-1555

*) NANJING NORMAL UNIVERSITY, DEPARTMENT OF PHYSICS, NANJING
   210097, CHINA

From 146 B.C. to 1760 A.D., 363 sets of cometary observations for a
total 88 different comets were recorded in Chinese Ancient Records of
Celestial Phenomena. According to those records, we reduced apparent
positions and mean equatorial coordinates (epoch 2000.0) for all more
than three times recorded comets. Taking into account the perturbations
of all nine planets and using the numerical method of N-body problem,
the orbits of correlative comets were calculated. For thirty different
comets, new orbits are presented for the first time. (C) 1998 Elsevier
Science Ltd. All rights reserved.

======================
(2) DUNCAN STEEL ON ASTEROIDS, BUFFON & COMETS

D.I. Steel: The ABC of ACM: asteroids, Buffon and comets. PLANETARY AND
SPACE SCIENCE, 1997, Vol.45, No.12, pp.1501-1503

SPACEGUARD AUSTRALIA, POB 3303, RUNDLE MALL, ADELAIDE, SA 5000,
AUSTRALIA

Most of the participants in the ACM 96 conference would have made use
of the facilities in a building named for Georges-Louis Leclerc, the
Compte de Buffon (1707-1799). Buffon made many major contributions to
the natural sciences, and may be considered to be one of the founders
of planetary science. He proposed a theory for the origin of the
planets which involved a massive comet having an oblique impact upon
the Sun, the ejected material condensing so as to form a regular system
of planets. Amongst his mathematical contributions is what is known as
Buffon's Needle, whereby experimental evaluations of may be made by
randomly dropping a needle onto a length, and accumulation the fraction
of times that the needle cuts one of the lines. Near-Earth asteroid
(NEA) trails imaged onto a CCD chip provide a two-dimensional analogue
of this, and where the pixel size is very large (this having some
advantages for NEA searching) an analysis based on Buffon's Needle
provides probabilities of the NEA trail lying within one, two or three
pixels, such probabilities affecting the chances of detection. It is
therefore appropriate that Buffon and his contributions to studies of
comets and asteroids be remembered in these conference proceedings. (C)
1998 Published by Elsevier Science Ltd. All rights reserved.

=====================
(3) ROSETTA AHOY: HOW TO ANCHOR A SPACECRAFT ON A COMET

N.I. Komle*) , A.J. Ball, G. Kargl, J. Stocker, M. Thiel, H.S.
Jolly, M. Dziruni, J.C. Zarnecki: Using the anchoring device of a comet
lander to determine surface mechanical properties. PLANETARY AND SPACE
SCIENCE, 1997, Vol.45, No.12, p.1515

*) AUSTRIAN ACADEMY OF SCIENCE, INSTITUT FUER WELTRAUMFORSCHUNG,
   ELISABETHSTR 20, A-8010 GRAZ

Owning to the low surface gravity of the Rosetta target comet
46P/Wirtanen, a means of anchoring the Rosetta Lander to the cometary
surface will be necessary. This task can be accomplished by firing an
anchor into the cometary soil immediately after touchdown to prevent a
rebound of the spacecraft from the surface or subsequent ejection by
other forces, and to allow for mechanical activities (drilling, etc.)
at the landing site.. The rational for anchoring is examined, based on
estimates of the main forces likely to act on the spacecraft after
landing. We report on the development of an anchoring device using a
pyrotechnic gas generator as a power source and an instrumented anchor.
In addition to the anchoring function, which is the primary purpose of
this system, the integration of acceleration and temperature sensors
into the tip offers the possibility to determine some important
material properties of the cometary surface layer. The accelerometer is
designed to measure the deceleration history of the projectile and is
thus expected to give information on how the material properties (in
particular strength) change within the penetrated layer(s), while the
temperature sensor will measure temperature variations at the depth at
which the anchor finally comes to rest. As the mechanical properties of
the material are not known, it is difficult to predict the final depth
of the anchor with any great certainty, but it may well be greater than
that reached by any other of the lander's instruments. The instrumented
anchor will be part of the MUPUS experiment, selected to form part of
the Rosetta Lander payload. We report on results of laboratory
simulations of anchor penetration performed at the Institut fur
Weltraumforschung, Graz, and compare these with models of projectile
penetration. The value of the results expected from the penetrometry
experiment in the context of an improved understanding of cometary
processes is discussed. (C) 1998 Elsevier Science Ltd. All rights
reserved.

==========================
(4) COMPOSITION OF COMETARY DUST

L. Kolokolova & K. Jockers: Composition of cometary dust from
polarization spectra. PLANETARY AND SPACE SCIENCE, 1997, Vol.45, No.12,
pp.1543-1550

MAX PLANCK INSTITUT FUER AERONAUTIC, KATLENBURG DUHM, GERMANY

The wavelength dependence of the polarization ('polarization spectra')
of cometary dust is discussed. It is shown that, in the case of large
phase angles, the wavelength dependence of the polarization is mainly
controlled by the complex refractive index of the particle material,
whereas the spectral dependence of the intensity is also sensitive to
the size of the particles. This suggests that observations of
'polarization spectra' may determine the composition of cometary dust.
An attempt is made to find the composition of the cometary dust
material by comparing the observed polarimetric data with laboratory
measurements of complex refractive indices of possible cometary
constituents. Silicates, graphite, metals, organics, water ice and
their mixtures are considered. It is shown that astronomical silicate
must be the most abundant constituent of cometary dust in the range of
heliocentric distances from 0.8 to 1.8 AU, whereas the volume fraction
of pure graphite or pure metals is less then 1%. A substance similar to
that of F-type asteroids may be present in comets. There is evidence
for an organic material that is being destroyed between heliocentric
distances of 0.8-1.8 AU. (C) 1998 Elsevier Science Ltd. All rights
reserved.

====================
(5) THE LAPLACIAN ORBIT DETERMINATION OF ASTEROIDS

M.J. Sokolskaya: On the Laplacian orbit determination of asteroids.
PLANETARY AND SPACE SCIENCE, 1997, Vol.45, No.12, pp.1575-1580

RUSSIAN ACADEMY OF SCIENCE, INSTITUTE OF THEORETICAL ASTRONOMY,
10 NABEREZHNAYA, RUSSIA

A modified Laplacian technique is described for initial orbit
determination of asteroids from CCD observations and its applications
for orbit determination of the main belt asteroids and near Earth
asteroids. The proposed modification is based on a simultaneous
improvement of both the orbital elements the derivatives of spherical
coordinates in frames of Laplace's method. It provides an orbit which
represents the used observations with the residuals comparable with
errors of these observations. The improved values of the derivatives
might be used as ephemeris parameters for identification of newly
discovered objects. (C) 1998 Elsevier Science Ltd. All rights
reserved

=======================
(6) THE DANGEROUS BORDER OF THE 5:2 MEAN MOTION RESONANCE

Z. Knezevic*), A. Milani & P. Farinella: The dangerous border of the
5:2 mean motion resonance. PLANETARY AND SPACE SCIENCE, 1997, Vol.45,
No.12, pp.1581-1585

*) ASTRONOMICAL OBSERVATORY, VOLGINA 7, YU-11050 BELGRADE, YUGOSLAVIA

After discovering that asteroid (2953) Vysheslavia, a Koronis family
member, has a typical dynamical lifetime of the order of 10 Myr only
against 'falling' into the 5:2 Kirkwood gap and ending up in a
hyperbolic orbit (Milani and Farinella, 1995. Icarus 114, 209-212), we
decided to repeat the same study for two other asteroids: 1991 UA(2)
and 1993 FR58, lying also very close to the outer edge of the same
resonance. The orbital elements of these bodies were not yet accurate
enough and we appealed to observers, both professional and amateur, to
obtain more astrometric data. Eight groups in three different countries
carried out observations, and as a result the Minor Planet Center could
derive updated, accurate orbits for both objects. Here we report on the
preliminary results of our study. Whereas the long-term behavior of
1991 UA(2) looks fairly regular and stable, 1993 FR58 exhibits a
typical 'stable chaos' behavior; nevertheless, it does not end up in
the resonance within a time span of 50 Myr. On the other hand, its
fictitious clones, placed just 3-4 x 10(-3) AU closer to the resonance,
undergo large irregular semimajor axis changes, fall into the resonance
and escape on a timescale <1 Myr. (C) 1998 Elsevier Science Ltd. All
rights reserved.

======================
(7) ESCAPE OF ASTEROIDS FROM THE HECUBA GAP

T. Michtchenko, S. Ferraz Mello: Escape of asteroids from the Hecuba
gap. PLANETARY AND SPACE SCIENCE, 1997, Vol.45, No.12, pp.1587-1593

UNIVERSITY OF SAO PAULO, INSTITUE OF ASTRONOMY & GEOPHYSICS, CAIXA
POSTAL 3386, BR-01060 SAO PAULO, SP, BRAZIL

The dynamics of the 2/1 mean-motion asteroidal resonance with Jupiter
is studied by numerical integration of the equations of motion of the
Sun-Jupiter-Saturn asteroid system. The measurement of the fundamental
asteroidal frequencies by means of Fourier and wavelet analyses allows
us to construct the web of the secular, secondary and Kozai resonances
inside the 2/1-resonance boundaries. The structure of the phase space
of the 2/1 resonance is discussed with emphasis on the acting
depletion mechanisms due to presence of these inner resonances. Special
attention is paid to the study of the middle-eccentricity depleted
region. The importance of the great inequality of the Jupiter-Saturn
system in the acceleration of the diffusion processes in this region is
pointed out. The existence of a group of asteroids like (3789)
Zhongguo, inside the 2/1 resonance, is also discussed. (C) 1998
Elsevier Science Ltd. All rights reserved.

=========================
(8) REQUIRED ACCURACY OF THE MOTION THEORIES OF PERTURBING BODIES

E.D. Kuznetsov: The celestial bodies motion theories: on the required
accuracy of the motion theories of the perturbing bodies. PLANETARY AND
SPACE SCIENCE, 1997, Vol.45, No.12, pp.1595-1606

URAL STATE UNIVERSITY, DEPARTMENT OF ASTRONOMY, LENIN AVE 51,
EKATERINBURG 620083, RUSSIA

The equation for calculation of the required accuracy of the perturbing
bodies motion theories is obtained. The equation relates the accuracy
required to take into account perturbing acceleration, acting on the
perturbed body, with the accuracy of the motion theory of the
perturbing body. The solutions for estimation of the required accuracy
both for the inner and external cases in the spherical coordinates are
coincided. The solution for the calculation of the required accuracy
for the general case (combining the inner and the external cases) in
Cartesian coordinates is obtained. The special cases for the solution
in Cartesian are studied. As an example, the estimations of the
required accuracy of the motion theories of the solar system planets
for some perturbed bodies (the near-Earth asteroid 4179 Toutatis, the
main belt asteroid 208 Larcimosa, the trojan asteroid 588 Achilles, the
centaur asteroid 5145 Pholus, the Kuiper belt asteroid 1995 QZ9, the
comet Halley) are obtained. The conditions of the use of the obtained
results are discussed. (C) 1998 Elsevier Science Ltd. All rights
reserved.

============================
(9) MONITORING CHIRON'S BRIGHTNESS

D. Lazzaro*), M.A. Florczak, C.A. Angeli, J.M. Carvano, A.S.
Betzler, A.A. Casati, M.A. Barucci, A. Doressoundiram, M. Lazzarin:
Photometric monitoring of 2060 Chiron's brightness at perihelion.
PLANETARY AND SPACE SCIENCE, 1997, Vol.45, No.12, pp.1607-1614

*) ON CNPQ, DEPARTMENT OF ASTROPHYSICS, BR-20921 RIO JANEIRO, BRAZIL

The results of photometric and spectroscopic observations of
comet/asteroid 2060 Chiron carried on at the Observatorio do
Pico-dos-Dias (Brazil) at the European Southern Observatory (Chile) and
at the Mauna Kea Observatory (Hawaii) during 1996 are presented. The
analysis of the photometric data shows that even at a minimum of
brightness 2060 Chiron presents some activity. The absolute magnitude,
H-v, varied from 6.79 in February to 6.22 in March. Therefore 2060
Chiron is still in a minimum of activity close to that of 1983-1985 and
of 1994-1995. (C) 1998 Elsevier Science Ltd. All rights reserved.

=============================================
(10) JOINT ASTEROID OBSERVATIONS BY ESO & KHARKIV OBSERVATORIES

V.G. Shevchenko*), I.N. Belskaya, V.G. Chiorny, J. Piironen, A.
Erikson, G. Neukum & R. Mohamed: Asteroid observations at low phase
angles. I. 50 Virginia, 91 Aegina and 102 Miriam. PLANETARY AND SPACE
SCIENCE, 1997, Vol.45, No.12, pp.1615-1623

*) ASTRONOMICAL OBSERVATORY, BOX 515, S-75120 UPPSALA, SWEDEN

We present observations of magnitude-phase dependences of three
low-albedo asteroids down to phase angles of 0.1-0.2 degrees. Data were
obtained during 40 nights from 1994 to 1995 within the joint
observational program at ESO and Kharkiv Astronomical Observatories
with the aim to reach as low phase angles as possible. All three
low-albedo asteroids may display a small nonlinear increase in
magnitude-phase dependence at subdegree phase angles. The phase curves
of 50 Virginia and 102 Miriam are poorly approximated by the HG
function. Rotation periods of the asteroids were also determined:
14.310+/-0.010 hours for 50 Virginia, 6.030+/-0.001 h for 91 Aegina and
15.789+/-0.003 h for 102 Miriam. (C) 1998 Elsevier Science Ltd. All
rights reserved.

===========================
(11) A NEW MODEL TO SIMULATE IMPACT BREAKUP

A. Cordelli & P. Farinella: A new model to simulate impact breakup
PLANETARY AND SPACE SCIENCE, 1997, Vol.45, No.12, pp.1639-1647

UNIVERSITY OF PISA, DIPARTIMENTO MATEMAT, GRP MECCAN SPAZIALE, VIA
BUONARROTI 2, I-56127 PISA, ITALY

We have developed a preliminary version of a new type of code to
simulate the outcomes of impacts between solid bodies, which we plan to
further refine for application to both asteroid science and space
debris studies. In the current code, colliding objects are modeled as
two-dimensional arrays of finite elements, which can interact with each
other in both an elastic and a shock-wave regime. The finite elements
are hard spheres with a given value for mass and radius. When two of
them come into contact the laws of inelastic scattering are applied,
thus giving rise to the propagation of shock waves. Moreover each
spherical elements interacts elastically with its nearest neighbours.
The interaction force corresponds to that of a spring having an
equilibrium length equal to the lattice spacing, and results into the
propagation of elastic waves in the lattice. Dissipation effects are
modeled by means of a dissipative force term proportional to the
relative velocity, with a given characteristic time of decay. The
possible occurrence of fractures in the material is model by assuming
that when the distance of two neighbouring elements exceeds a threshold
value, the binding force between them disappears for ever. This model
requires finding a plausible correspondence between the input
parameters appearing in the equations of motion, and the physical
properties of real solid materials. Some of the required links are
quite obvious (e.g., the relationship between mass of the elements and
elastic constant on one side, and material density and sound velocity
on the other side), some others a priori are unclear, and additional
hypotheses on them must be made (e.g., on the restitution coefficient
of inelastic scattering). Despite the preliminary character of the
model, we have obtained some interesting results, which appear to mimic
in a realistic way the outcomes of actual impacts. For instance, we
have observed the formation of crates and fractures, and (for high
impact energies) the occurrence of catastrophic breakup.. The masses and
velocities of the fragments resemble those found in laboratory impact
experiments. (C) 1998 Elsevier Science Ltd. All rights reserved.

----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To subscribe, please
contact the moderator Benny J Peiser at <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied or
reproduced for any other purposes without prior permission of the
copyright holders.



CCCMENU CCC for 1998

The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of

The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of Georgia or the University System of Georgia.