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(meteorobs) Excerpts from "CCNet 6/2001 - 12 January 2001"
Several items of research interest - in particular, the inimitable(!)
Dr Marsden's comments on the "January Coma Berenicid" possible shower!
Lew Gramer
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 12 January 2001
Date: Fri, 12 Jan 2001 12:44:13 -0000
CCNet 6/2001 - 12 January 2001
------------------------------
[...]
(2) STARDUST CAN SEE CLEARLY NOW -- JUST BEFORE EARTH FLYBY
NASA News <NASANews@hq.nasadot gov>
[...]
(4) NASA BALLOON RESEARCH RIDES TO THE EDGE OF SPACE
Mark Hess <mhess@pop100.gsfc.nasadot gov>
(5) COMA BERENICIDS, YES; COMET CONNECTIONS, NO
Brian Marsden <brian@cfaps1.harvarddot edu>
[...]
(8) FORMATION OF IRON METEORITES
G.K. Benedix
(9) ACTIVE REGIONS ON THE SURFACE OF COMET 43P/WOLF-HARRINGTON
S. Szutowicz
(10) POSITIONAL ERRORS & THE PERTURBED TWO-BODY PROBLEM
H. Arakida
(11) ASTEROIDAL PROCESSING OF CHONDRITIC MATERIALS
P.A. Bland
====================================================================
(2) STARDUST CAN SEE CLEARLY NOW -- JUST BEFORE EARTH FLYBY
>From NASA News <NASANews@hq.nasadot gov>
Donald Savage
Headquarters, Washington, DC January 11, 2001
(Phone: 202/358-1547)
Martha J. Heil
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/ 354-0850)
RELEASE: 01-06
STARDUST CAN SEE CLEARLY NOW -- JUST BEFORE EARTH FLYBY
After a few months of foggy vision, NASA's Stardust mission team has
improved the spacecraft's navigation-camera resolution to nearly normal,
just as Stardust is preparing to make a close flyby of the Earth on Monday.
By heating the camera's optical path, the Stardust team was able to help its
nearsighted spacecraft boil away contaminants that had been deposited on
optical surfaces.
One year ago, the imaging team took pictures of a small lamp inside the
optical path of the camera. The camera will be used to navigate Stardust to
its 2004 encounter with Comet Wild 2
(pronounced "vilt-2"). Apparent contamination of the navigation-camera
prevented a clear test-image of the squiggly line of the lamp's filament,
and the lens seemed to be covered with a veil of light-scattering material
that produced a blurry image.
The team concluded that the contamination might have been released with
gases escaping from the spacecraft after its launch, and that heating the
optical path of the camera might evaporate the
contaminant covering the camera lens. After a series of heating cycles, they
retested the camera by taking more pictures of the lamp.
Pictures taken after the heating revealed that the zigzag line of the lamp's
filament was visible again. Images of stars taken by the camera are also
clearer. The team estimates the camera can now photograph stars two
magnitudes (celestial degrees of brightness) better. The navigation camera
has detected stars as faint as 9th magnitude, which should allow the
spacecraft to perform its final navigation maneuvers during approach to the
comet nearly at the time originally planned.
Now Stardust, on its journey to collect comet dust, is getting ready to
springboard from Earth -- in a maneuver called a "gravity-assist" -- when
the spacecraft passes closest to Earth on January 15, 2001.
Stardust was launched on February 7, 1999, into its first loop around the
Sun. When Stardust passes by Earth at about 22,400 miles per hour (or 10
kilometers per second), it will go into a slightly wider orbit that will
allow it to reach the comet on January 2, 2004.
On Monday, January 15, Stardust will fly by a point just southeast of the
southern tip of Africa, slightly more than 3,700 miles (6,000 kilometers)
from the surface at about 5:15 a.m. EST (3:15 a.m. PST).
Stardust may be visible to observers using sophisticated telescopes with
charge-coupled device (CCD) detectors from the Pacific Ocean and the Western
United States just after the spacecraft flies by Earth. Stardust will not be
visible using binoculars.
A gravity-assist works like this: when a spacecraft closely approaches a
planet, the planet's gravitational pull accelerates the spacecraft and bends
the flight path. Mission designers account for this extra pull and use it to
their advantage to boost spacecraft speed and direct interplanetary
spacecraft to their targets. Like a windup before the pitch, the Earth
gravity-assist will sling Stardust into the right path to meet Comet Wild 2.
About 15 hours after its closest approach to Earth, the spacecraft will pass
about 61,000 miles (98,000 kilometers) from the Moon. Because of the greater
distance, the Moon's gravity will have essentially no influence on the
spacecraft's flight path.
Stardust, a part of NASA's Discovery Program of low-cost, highly focused
science missions, is managed by the Jet Propulsion Laboratory (JPL),
Pasadena, CA, for NASA's Office of Space Science, Washington, D.C. JPL is a
division of the California Institute of Technology, Pasadena. More
information on the Stardust mission is available at:
http://stardust.jpl.nasadot gov/index.html
====================================================================
(4) NASA BALLOON RESEARCH RIDES TO THE EDGE OF SPACE
>From Mark Hess <mhess@pop100.gsfc.nasadot gov>
Dolores Beasley
Headquarters, Washington, DC January 11, 2001
(Phone: 202-358-1753)
Keith Koehler
Wallops Flight Facility, Wallops Island, VA
(Phone: 757-824-1579)
Betty Flowers
Balloon Launching Station, Alice Springs Airport, Australia
(Phone: 61-8-8952-6315)
RELEASE: 01-03
NASA BALLOON RESEARCH RIDES TO THE EDGE OF SPACE
The countdown is underway for the launch of a revolutionary research-balloon
designed to fly higher and longer than anything before it, and the flight
could open a new era in scientific research.
NASA's new Ultra-Long Duration Balloon (ULDB) is scheduled to lift off Jan.
16 from Alice Springs, Australia, and will carry the hopes of many
scientists who see balloon technology
as an economical means of studying the Earth and space.
"Although balloons have been flying for more than 200 years and scientists
have long used them for a variety of research missions, the length of time
balloons can stay aloft has always constrained their efforts," said Steve
Smith, Chief of the Balloon Program Office, NASA Goddard Space Flight
Center's Wallops Flight Facility, Wallops Island, VA. "Thanks to greatly
enhanced computer technologies, high-tech materials and advanced designs,
longer-range balloons are poised to open a new frontier for high-altitude
research".
The balloon is expected to float over the Southern Hemisphere at an altitude
of approximately 115,000 feet (35 kilometers), 3 to 4 times higher than
passenger planes. While the test
flight is expected to last only about two weeks and circumnavigate the
globe, the ULDB is designed to support missions for up to 100 days.
"Balloons provide cost-effective platforms for near-space observations,"
said Dr. Vernon Jones, Office of Space Science, NASA Headquarters,
Washington, DC. "This January flight provides an excellent opportunity to
test the newly designed ULDB system."
The full-scale ULDB is the largest single-cell, super-pressure (fully
sealed) balloon ever flown. At launch, the balloon is partially inflated
with helium and expands as it rises. When fully inflated, the massive ULDB
would barely fit inside a domed football stadium.The ULDB floats above 99
percent of the Earth's atmosphere and can carry a 3,500-pound
(1.588-kilogram) payload. The balloon system comes down in a controlled
descent. It may be visible from the ground with a telescope and, in some
cases, with the naked eye.
The ULDB's unique pumpkin-shaped design and its novel material, a
lightweight polyethylene film about the thickness of ordinary plastic
food-wrap, were successfully tested during a prototype flight from Ft.
Sumner, NM, last June.
"Recent development of new balloon materials and associated technologies
will enable challenging, important investigations to be done at relatively
modest cost," said Jones. He added that the ability to fly balloons for
months or years at a time would create a multitude of scientific and
business opportunities.
Conventional high-altitude, scientific balloon flights typically last a few
days to a week because temperature changes from day to night ultimately
cause the balloon to lose altitude. The ULDB is completely sealed, so gas is
not vented to relieve pressure. The new super-pressure balloon will maintain
lift, size and shape, and will not lose significant altitude due to
atmospheric influences.
Future science missions for the ULDB will study the source of cosmic rays
generated from shock waves emanating from supernovae and will perform
surveys of X-ray emiting objects in the universe, search for planets around
other nearby stars and will study other objects in space, including the Sun.
The Wallops Flight Facility manages NASA's scientific balloon program for
the Office of Space Science. Launch operations are conducted by the National
Scientific Balloon Facility, Palestine, TX, which is managed for NASA by the
Physical Sciences Laboratory of New Mexico State University, Las Cruces.
Australian operational support to NASA is provided by the Commonwealth
Scientific Industrial Research Organization.
More information on the Ultra-Long Duration Balloon mission and tracking of
the balloon flight can be found at:
http://www.wff.nasadot gov/pages/scientificballoons.html
============================
* LETTERS TO THE MODERATOR *
============================
(5) COMA BERENICIDS, YES; COMET CONNECTIONS, NO
>From Brian Marsden <brian@cfaps1.harvarddot edu>
Dear Benny,
I was quite startled to read in the Jan. 11 CCNet, not only of the suggested
association of a recently observed meteor shower with "the poorly observed
Comet Lowe 1913 I", but also of the suggested identity of the 1913 object
with another comet, "observed, again rather badly, in 1750".
The fact is that the 1913 object was recorded only by its discoverer, an
"enthusiastic" Australian amateur astronomer, who on Jan. 7 of that year
reported to the Adelaide Observatory _very_ rough (and initially quite
erroneous) positional data obtained by him with a 3-inch telescope on four
mornings during the previous week. Even when the data were amended and
attempts made to compute an orbit, no observations by others came to light,
which was a little surprising since the object should have been an easy
object for northern-hemisphere astronomers at and before its alleged
discovery. This situation is reminiscent of many that continue to arise at
the IAU Central Bureau for Astronomical Telegrams, and perusal of the Lowe
information
preserved in the Astronomische Nachrichten and the Journal of the British
Astronomical Association cannot help but place the existence of the object
in doubt. Although the various orbits computed at the time by Viljev and
Crommelin agreed on a nodal longitude of 300 to 305 degrees (and the
possibility of a very close approach to the earth around Jan. 25 if the
comet
had come to perihelion some weeks later than indicated), there was
disagreement as to whether the orbital inclination was 80 degrees or 120
degrees: if I wish to contend with residuals of well over a degree, I get an
inclination of something like 110 degrees. Nevertheless, as stated in the
introduction to the Catalogue of Cometary Orbits already in the 1972
edition, I felt it wise to exclude this comet from consideration, and it was
not given a new-style designation when the comet-designation system was
revised at the end of 1994.
What about the comet of 1750? The positional information was also provided
by just a single observer, who saw the comet on three nights in January of
that year. In this case the recorder was the distinguished astronomer and
demographer and secretary of the Royal Swedish Academy of
Sciences, Pehr Wargentin. The observations were made with the naked eye and
two different telescopes, and the comet was also seen by a colleague. Given
that this was in the days before comet hunting became a sport (with comets
named for their discoverers), I have little doubt that the object existed
and discussed it in my paper in the Astronomical Journal in 1973 on the
orbit of the comet associated with the Perseid meteors. Interestingly, the
nodal longitude is also around 300 degrees, and the inclination could be as
low as 120 degrees. The orbit I actually published does in fact bear a
superficial resemblance to some computed from Lowe's 1913 data, although the
published perihelion distance, 0.2 AU, is only half that derived in 1913.
Furthermore--as I actually remarked in my paper--if the 1750 perihelion
distance were as large as 0.4 AU, the argument of perihelion would drop to
240 degrees, which is significantly less than the 280-degree value that best
fits the 1913 data.
Even if one accepts the reality of the 1913 data, there is no reason to
believe that the comet had a period as short as a century or two, and there
is in any case no way to satisfy both apparitions of data with the same
orbit. Given my predilection for the reality of the 1750 comet, one might
wish to consider it a better candidate for the parent of the Coma Berenicid
meteors.
But it does not seem that the orbit of the 1750 comet comes particularly
close to the earth. Although the date was close to the anticipated previous
perihelion passage of the 1862 parent of the Perseid meteors, Wargentin's
comet was clearly not it. My acceptance instead of Kegler's 1737 comet as "a
far better candidate" and consequent prediction of the late-1992 return was
of course later amply demonstrated.
So while I give Gorelli and McBeath credit for attempting a meteor-comet
association, the least said about the 1913 and the 1750 events, the better.
Regards
Brian
============
* ABSTRACTS *
============
(8) FORMATION OF IRON METEORITES
Benedix GK, McCoy TJ, Keil K, Love SG: A petrologic study of the IAB iron
meteorites: Constraints on the formation of the IAB-Winonaite parent body
METEORITICS & PLANETARY SCIENCE 35: (6) 1127-1141 NOV 2000
We studied 26 IAB iron meteorites containing silicate-bearing inclusions to
better constrain the many diverse hypotheses for the formation of this
complex group. These meteorites contain inclusions that fall broadly into
five types: (1) sulfide-rich, composed primarily of troilite and containing
abundant embedded silicates; (2) nonchondritic, silicate-rich, comprised of
basaltic, troctolitic, and peridotitic mineralogies; (3) angular, chondritic
silicate-rich, the most common type, with approximately chondritic
mineralogy and most closely resembling the winonaites in composition and
texture; (4) rounded, often graphite-rich assemblages that sometimes contain
silicates; and (5) phosphate-bearing inclusions with phosphates generally
found in contact with the metallic host. Similarities in mineralogy and
mineral and O-isotopic compositions suggest that IAB iron and winonaite
meteorites are from the same parent body.
We propose a hypothesis for the origin of IAB iron meteorites that combines
some aspects of previous formation models for these meteorites. We suggest
that the precursor parent body was chondritic, although unlike any known
chondrite group. Metamorphism, partial melting,and incomplete
differentiation (i.e., incomplete separation of melt from residue) produced
metallic, sulfide-rich and silicate partial melts (portions of which may
have crystallized prior to the mixing event), as well as metamorphosed
chondritic materials and residues. Catastrophic impact breakup and
reassembly of the debris while near the peak temperature mixed materials
from various depths into the re-accreted parent body. Thus, molten metal
from depth was mixed with near-surface silicate rock, resulting in the
formation of silicate-rich IAB iron and winonaite meteorites. Results of
smoothed particle hydrodynamic model calculations support the feasibility of
such a mixing mechanism. Not all of the metal melt bodies were mixed with
silicate materials during this impact and reaccretion event, and these are
now represented by silicate-free IAB iron meteorites. Ages of silicate
inclusions and winonaites of 4.40-4.54 Ga indicate this entire process
occurred early in solar system history.
Addresses:
Benedix GK, Virginia Tech, Dept Geol Sci, Blacksburg, VA 24061 USA.
Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA.
Smithsonian Inst, Natl Museum Nat Hist, Dept Mineral Sci, Washington, DC
20560 USA.
NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA.
Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys &
Planetol, Honolulu, HI 96822 USA.
Hawaii Ctr Volcanol, Honolulu, HI USA.
Copyright ) 2001 Institute for Scientific Information
==============
(9) ACTIVE REGIONS ON THE SURFACE OF COMET 43P/WOLF-HARRINGTON
Szutowicz S: Active regions on the surface of Comet 43P/Wolf-Harrington
determined from its nongravitational effects
ASTRONOMY AND ASTROPHYSICS 363: (1) 323-334 NOV 2000
The nongravitational perturbations in the motion of the periodic comet
Wolf-Harrington are investigated during its nine observable apparitions in
the period 1924-1998. To explain the irregular variations in the
nongravitational acceleration, two different models are considered and
successfully used to link all the apparitions: a) Model of nucleus with the
activation and deactivation of discrete outgassing sources on the surface;
b) Forced precession model of the spin axis of the nucleus with an activity
described by nonlinear changes of the perihelion shift of the gas production
curve. The first model is represented by two slightly different orbital
solutions in which the northern active region is persistent and the
initiations and disappearances of two southern regions are responsible for
the observed variability of the nongravitational acceleration. Profiles of
the modelled gas production rates are compared with observed light curves of
the comet and used for an estimation of the effective outgassing area and
the activity level of the cometary nucleus. According to all employed models
of the nongravitational acceleration similar shifts of the maximum of the
comet activity with respect to successive perihelion passages over the whole
examined interval of the motion have been detected.
The model parameters describing physical properties of the comet nucleus
such as the nucleus orientation, the localization and the size of the active
regions or the oblateness of the nucleus are derived from numerical fitting
of the models to positional observations of the comet.
Addresses:
Szutowicz S, Polish Acad Sci, Space Res Ctr, Bartycka 18A, PL-01237 Warsaw,
Poland.
Polish Acad Sci, Space Res Ctr, PL-01237 Warsaw, Poland.
Copyright ) 2001 Institute for Scientific Information
===============
(10) POSITIONAL ERRORS & THE PERTURBED TWO-BODY PROBLEM
Arakida H, Fukushima T: Long-term integration error of Kustaanheimo-Stiefel
regularized orbital motion
ASTRONOMICAL JOURNAL 120: (6) 3333-3339 DEC 2000
We confirm that the positional error of a perturbed two-body problem
expressed in the Kustaanheimo-Stiefel (K-S) variable is proportional to the
fictitious time s, which is the independent variable in the K-S
transformation. This property does not depend on the type of perturbation,
on the integrator used, or on the initial conditions, including the nominal
eccentricity. The error growth of the physical time evolution and the Kepler
energy is proportional to s if the perturbed harmonic oscillator part of the
equation of motion is integrated by a time-symmetric integration formula,
such as the leapfrog or the symmetric multistep method, and is proportional
to s(2) when using traditional integrators, such as the Runge-Kutta, Adams,
Stormer, and extrapolation methods. Also, we discovered that the K-S
regularization avoids the step size resonance/instability of the symmetric
multistep method that appears in the unregularized cases. Therefore, the K-S
regularized equation of motion is useful to investigate the long-term
behavior of perturbed two-body problems, namely, those used for studying the
dynamics of comets, minor planets, the Moon, and other natural and
artificial satellites.
Addresses:
Arakida H, Grad Univ Adv Studies, Dept Astron Sci, 2-21-1 Osawa, Mitaka,
Tokyo 1818588, Japan.
Grad Univ Adv Studies, Dept Astron Sci, Mitaka, Tokyo 1818588, Japan.
Natl Astron Observ, Tokyo 1818588, Japan.
Copyright ) 2001 Institute for Scientific Information
=================
(11) ASTEROIDAL PROCESSING OF CHONDRITIC MATERIALS
Bland PA, Lee MR, Sexton AS, Franchi IA, Fallick AET, Miller MF, Cadogan JM,
Berry FJ, Pillinger CT: Aqueous alteration without a pronounced
oxygen-isotopic shift: Implications for the asteroidal processing of
chondritic materials
METEORITICS & PLANETARY SCIENCE 35: (6) 1387-1395 NOV 2000
Primitive meteorites exhibit certain features that are consistent with
aqueous and thermal alteration on asteroids, but O-isotopic analyses show
only a modest heavy-isotope shift, interpreted as indicating modification in
the nebula. To understand the isotopic effects of asteroidal alteration, we
take the L-group ordinary chondrites weathered in Antarctica as an analogue.
The data show that alteration is a two-stage process, with an initial phase
producing only a negligible isotopic effect. Although surprising, a possible
explanation is found when we consider the alteration of terrestrial
silicates. Numerous studies report pervasive development of channels a few
to a few tens of nanometer wide in the incipient alteration of silicates. We
observe a similar texture. Alteration involves a restructuring of clay
minerals along these narrow channels, in which access of water is
restricted. The clay shows a topotactic relationship to the primary grain,
which suggests either epitaxial growth of the clay using the silicate as a
substrate or inheritance of the original O structure by the clay. Our data
suggests the latter: with extensive inheritance of structural polymers by
the weathering product, the bulk O-isotopic composition is comparatively
unaffected. This offers an explanation for the lack of an isotopic effect in
the weathering of the L chondrites. If substantial modification of
chondritic materials may occur without a pronounced isotopic effect, it also
reconciles existing O analyses of CV chondrites with an asteroidal model of
aqueous alteration.
Addresses:
Bland PA, Nat Hist Museum, Dept Mineral, Cromwell Rd, London SW7 5BD,
England.
Nat Hist Museum, Dept Mineral, London SW7 5BD, England.
Univ Edinburgh, Dept Geol & Geophys, Edinburgh EH9 3JW, Midlothian,
Scotland.
Open Univ, Planetary Sci Res Inst, Milton Keynes MK7 6AA, Bucks, England.
Scottish Univ Res & Reactor Ctr, Glasgow G75 0QF, Lanark, Scotland.
Univ New S Wales, Sch Phys, Sydney, NSW 2052, Australia.
Open Univ, Dept Chem, Milton Keynes MK7 6AA, Bucks, England.
Copyright ) 2001 Institute for Scientific Information
==============
(13) AND FIMALLY: SPACE RESAERCH SPILLS ZE END FOR DYSLEXIA
>From The Scotsman, 12 January 2001
http://www.thescotsman.codot uk/uk.cfm?id=38724&keyword=the
Jennifer Trueland Health Correspondent
DYSLEXIA could be eradicated within a decade for most children using
exercises developed for disorientated spacemen returning to earth, British
experts said yesterday.
A private clinic in Warwickshire has harnessed discoveries made by the US
space administration NASA to help affected children improve their reading
and writing ability.
Initial results of a study into the exercise method are to be presented at a
conference held by the British Dyslexia Association in York in April.
NASA had found that astronauts suffered a kind of temporary dyslexia,
thought to be caused by weightlessness, which disrupts the way the
connections between their brain and actual functions. To help the
astronauts, they developed a balance and measurement machine and exercises
to retrain the eyes to track smoothly and the brain to listen to the body's
balance mechanisms.
The programme is now being pioneered at the Dyslexia, Dyspraxia and
Attention Treatment Centre (DdAT) in Kenilworth, which is funded by Wynford
Dore, whose own daughter, Susie, suffered from dyslexia.
His programme is based on work conducted by Professor Rod Nicholson and
Angela Fawcett at the University of Sheffield which focuses upon the area of
the brain which manages co-ordination.
The British clinic uses one of the #100,000 NASA machines to screen children
with dyslexia and prescribe individual exercise programmes at a cost of
about #475.
According to Mr Dore, the clinic has shown results no one could have dreamt
of, with 97 per cent of children showing significant improvement within
three months.
"I hope that within ten years every child starting school will be screened
and treated so that they can go through school without the stigma and
difficulties they suffer at the moment.
"I think every child who has been through the programme has shown some
improvement and adults too, who have tried it have found an explanation why
they have always found some things difficult. It's like a sigh of relief for
adults and for children it's the chance to ride a bike, catch a ball and do
all the other things that they want to do."
The programmes work on posture, balance and eye control. Exercises include
encouraging children to recite a times table while standing one-legged on a
cushion and throwing a bean bag from one hand to the other at eye level.
A formal research programme to evaluate the technique's success will be
started this month, overseen by Professor David Reynolds of Exeter
University.
He said: "Best-case scenario is that there's a powerful treatment effect
which could live up to the claim that it will eradicate dyslexia within ten
years. But we need the scientific evidence to back the impressionistic
evidence that there appears to be something there."
He said the clinic had already treated more than 90 children.
Copyright 2001, The Scotsman
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