The Infrared Astronomical Satellite (IRAS) sampled the entire asteroid population at wavelengths from 12 to 100 microns during its 1983 all sky survey. The IRAS Minor Planet Survey (IMPS) includes updated results for more recently numbered as well as other additional asteroids with reliable orbital elements. Albedos and diameters were derived from the observed thermal emission and assumed absolute visual magnitudes and then entered into the IMPS database at the Infrared Processing and Analysis Center (IPAC) for members of the Themis, Eos, Koronis and Maria asteroid families and compared with their visual colors. The IMPS results for the small (down to about 20 km) asteroids within these major families confirm trends previously noted for their larger members. Each of these dynamical families which are defined by their similar proper elements appears to have homogeneous physical properties

Matson, D. L.

Tedesco, E. F.

Veeder, G. J.

Williams, J. G.

English

NASA Technical Reports Server

:_( >I ' 9 l
N91-26011
IRAS ASTEROID FAMILIES; G.J. Veeder, J.G. Williams, E.F.
Tedesco and D.L. Matson, Jet Propulsion Laboratory, California
Institute of Technology
225
The Infrared Astronomical Satellite (IRAS) sampled the
entire asteroid population at wavelengths from 12 to i00 microns
during its 1983 all sky survey. The IRAS Minor Planet Survey
(IMPS) includes updated results for more recently numbered as
well as other additional asteroids with reliable orbital
elements. Albedos and diameters have been derived from the
observed thermal emission and assumed absolute visual magnitudes
and then entered into the IMPS database at the Infrared
Processing and Analysis Center (IPAC) for members of the Themis,
Eos, Koronis and Maria asteroid families and compared with their
visual colors. The IMPS results for the small (down to about 20
km) asteroids within these major families confirm trends
previously noted for their larger members. Each of these
dynamical families which are defined by their similar proper
elements appears to have homogeneous physical properties. For
example, small members of the large Themis family are also dark.
The Eos family has intermediate albedos and B-V colors between
the ranges observed for main belt C and S class asteroids. In
particular, the centroid of the range of albedos for the Eos
family near a value of 0.i is at a relative minimum for the
albedo distribution observed for the general main belt asteroid
population. The homogeneity observed within each major asteroid
family implies that even if the two parent bodies of the S class
asteroids in the Koronis and Maria families were differentiated
they had relatively uniform interiors and did not have large
distinct (metallic) cores.
The research described in this abstract was carried out at the
Jet Propulsion Laboratory, California Institute of Technology,
sponsored by the Air Force Geophysics Laboratory through
agreement with the National Aeronautics and Space Administration.
https://ntrs.nasa.gov/search.jsp?R=19910016697 2020-03-19T16:50:59+00:00Z
226 ACN '91
Hiqh Resolute.on _maqes of p/Tempel 1 add P/Tempel 2 Constructed
from IRAS Survey Data
Russell G. Walker (Jamieson Science & Engineering, Inc), Humberto
Campins (University of Florida), and Martin F. Schlapfer (Jamieson
Science and Engineering, Inc).
Infrared images of P/Tempel 1
and P/Tempel 2 have been
constructed from IRAS survey
data using a computer algorithm
based on the Maximum Correlation
Method for Image Construction
(MCM) (Aumann, H.H., Fowler,
J.W., and Melnyk, M., Astron. J.
99, no.5, pp 1674-1681, 1990).
Image construction was performed
in a moving Sun-referenced
coordinate system with the comet
at the origin. Motion of the
comet relative to the IRAS scans
p/TEMPrlL 1 12urn JO 2445544
(LONcA'r I ON (ARCS[C)
determines the number of scans Figure i. Image of Tempel 1 after
within the image, and thus 12 iterations of the MCM.
limits the effective spatial
resolution achievable by the MCM
to about 40 arcsec at 12 Bm and
25 _m, 57 arcsec at 60 #m, and ,p(.,(_2 ,2.._02,,,,,3
80 arcsec at i00 Dm- The five "_0°_ _ o_°_-_----__0 o_ _ _Pl
sets of images of Tempel 1 at [o o , _-_12, 25, 60 and i00 #m span the
period from 4.6 days to 81 days _...[O_o _ &D A ° & 2 °- J
after perihelion passage. The i _
four sets of images of P/Tempel
2 were taken from 46 to 97 days
past perihelion. Figures 1 and __
2 show a typical pair of 12 _m :I.._::So _: _! .._:_._._O_..o limages of Tempel 1 and Tempel 2.
Solar illumination is from the _ ........:..... _.; ... .........
left. The heliocentric and _o._..,o.(..c_c>
geocentric distances are 1.50 AU Figure 2. Image of Tempel 2 after
and 1.08 AU respectively for 12 iterations of the MCM.
both comets, and the phase is
42 ° . Tempel 1 is 19 days past
perihelion, while Tempel 2 is 56 days past perihelion. The peak
radiance of Tempel 1 is 126 MJy/sr, while that of Tempel 2 is 67
MJy/sr. Contours start at 3 times the mean noise of the map and
are increasing by j_. The prominent linear feature in the Tempel 2
image is the dust trail which is observed both ahead and behind the
comet along its orbit. Direct comparisons of post perihelion comet
dust activity are made at comparable heliocentric distances, and
the relative production of large grains is determined.
ACH ' ,9 i 22 7
DISCOVERY OF COMETARYDUST FROMGRANITE Wan9 Erkang, Hu Zhon9 wei, Wan Yuqiu.
Nanjin9 University, 210008, Nanjin9 China*
A large number of dark magnetic microspherules were extracted from 9ranite near
Suzhou, Jiangsu province, China. Most of them range in diameter from 0.1-0.3mm. They
can be divided into three types: Iron, Stony and Glassy. The analyzed results prove
that these spherules are of extraterrestrial origin (1) (2). Further studies show
the microspherules are of cometary dust.
The main chemical compositions of the spherules( for example:Si02-45.39, Ti02-
0.95, A1203-32.32, Fe0-7.07, Mn0-0.02, M90-1.98, Ca0-4.49, Na20-0.25, K20-0.90) are
similar to those of Tunguska spherules. Some dusts are mainly composed of Fe, C, Ni,
with the maximum content of C up to 9.21%. As M.E Lawler et ai(1989) found that
about I_ of Halley's comet dust are almost completely composed of Fe and C, auther
belives these two kinds of dusts are quite similar to each other. Under HREM,
special microscrystals, such as whiskers and platelets, can be observed in some
samples, which reveals the characteristic of 9as to particle. The INAA results
demonstrate that contents of Al, Ca, Ti, V, Sc,, Hf, W are enriched, while M9, Mn,
Co, Cr, Zn seriously depleted. Besides, Content of REE is much more than that of CI
chondrite. The REE distribution partten displays that it has not been differentiated
obviously. In contrast to the results of K. Notsu (1978), main element and trace
element of some samples are very similar to that of vaporized residual fraction of
Allende meteorite.
These 9eneral characteristics mentioned above indicate that: Bein9 riched in
pre-solar system component features these dusts, and is exactly similar to cometary
dust known so far. That shows the dusts are cometary ori9in. They took part in the
evolution of the Earth and were captured by 9ranite magma durin9 the Mesozoic era.
References:
(I) Wan9 Erkang, et al.,
(2) Wan9 Erkang, et al.,
1990,15th IMA. abstracts, 670-671.
1990, 126th IAU. abstracts, 124.
* This project is supported by NNSFC.
E28 AC._I '91
ROTATION OF SPLIT COMETARY NUCLEI
Jun-ichi WATANABE
National Astronomical Observatory of Japan
Institute for Astronomy, University of Hawaii
The rotational motion of split cometary nuclei is studied.
A large-amplitude precession in each fragment is easily excited
by the splitting. Some simulation cases show the excitation of
higher energy state for rotation with given angular momentum.
The rotational state strongly depends on the mass-volume
partition of the nuclei at the splitting, and on the original
rotation.
This characteristic of the cometary nuclei survived after
the splitting gives us a clue to study the internal structure
of the nuclei. The damping of the precession needs long time(
>i0 Myr) if the internal dissipation is similar to that of
asteroid(Burns and Safronov 1973). Hence, if most of the nuclei
which were remnants of splitting have no large precession, then
the internal structure of the cometary nuclei would be
extremely fragile.
The excitation of the precession also gives us an
important information on the origin of the short period comets.
It is proposed that the short period comets are supplied from
the larger bodies of long period comets by splitting. This idea
solves the unbalance problem of number flux between the short
and long period comets. There may be evidences for supporting
this idea, for example, many splitting events, sun-grazing
comets, and Chiron. This idea can be tested by observing
rotational state of the short period comets if the internal
dissipation in the nuclei is small. If they have precession
with large amplitude, then these comets may be split origin.
On these view points, it is important to observe the split
nuclei. We also show the result of CCD imaging observation of
comet P/Taylor, which is a survived nucleus of splitting in
1916.
.-\CH '91 229
METEOR RADIANT MAPPING WITH MU RADAR
J. WATANABE(1), T. NAKAMURA(2), T. TSUDA(2),
M. TSUTSUMI(2), A. MIYASHITA(1), and M. YOSHIKAWA(3)
l:Natlonal Astronomical Observatory of Japan
2:Radlo Atmospheric Science Center, Kyoto University
3:Communicatlons Research Laboratory
We carried out mapping of radiant point of the meteor
shower with the MU radar located at Shlgaraki, Japan(34.85"N,
136.10"E). This radar is characterized by an active phased
array system, and mainly used for atmospheric observations. The
frequency is 46.5 MHz, which is also appropriate for meteor
echo observations. As same as other radar systems, the MU radar
can be interferometrlc use for determining the position of the
meteors.
Our mapping method is similar to Chat originally proposed
by Morton and Jones(1982). The modification is that we weighted
each meteor by using the beam pattern. We present some
preliminary results of the radiant point mapping of several
meteor shows.
Flg. Radiant point map of
the Geminids in 1989.
53
49
__J
o 2_
w
J9
9'.'
s
"01 Ill 121 l
-OUATORIAL LONGITUDE
230 ACH '91
NEAR-IR IMAGING OBSERVATION OF COMET AUSTIN 1989C1
J. Watanabe(1), T.e. Aoki(2), N. Hlromoto(2), H. Takaml(2)
l:National Astronomical Observatory of Japan
2:Communications Research Laboratory
Imaging observations of comet Austin 1989cl were carrled
out with an array detector attached to the Nasmyth focus of the
1.5-m telescope. We obtained 36 images of J, H, K bands in
total on April 29, 30, May 9, 26, and 27. A featureless, round
shape of the comet was revealed in all images of 4.2' field of
view. The asymmetry of the coma was not recognized even if we
applled an image enhancement technique. The intensity
distribution is well fitted by d'-2 density dlstrlbutlon of
scattering dust in the coma, where d is the radial distance
from the nucleus. The flux of the comet decreased as r'-5,
where r Is the heliocentric distance. This decreasing rate is
steeper than that of comet P/Halley.
Photometry of comet Austin 1989ci in K band. The open squares,
circles, triangles, and crosses represents magnitude data of
4200km, 8400km, 12600km, and 16800km apertures at the comet.
W
rn
b--
Z
L.O
5.0
6.0
7.0
8.0
9.0
L , , , I , , , , I
1.0 1.5
LOG HELIOCENTRIC OISTANCE(A.U.]
AC_'I '91 231
Comets, Image Deconvolution, and Second-Generation Instruments
Harold A. Weaver, Space Telescope Science Institute, 3700 San Martin Drive,
Baltimore MD 20771
NO ABSTRACT AVAILABLE


IRAS asteroid families

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server