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(meteorobs) Excerpts from "CCNet 107/2001 - 15 October 2001"
Note the latest entry in the "Leonid links" barrage this month...
This one from Dr. Michael Paine. Clear skies!
Lew Gramer <owner-meteorobs@atmob.org>
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet 107/2001 - 15 October 2001
Date: Mon, 15 Oct 2001 14:56:05 +0100
CCNet 107/2001 - 15 October 2001
==========================================================================
[...]
(4) THE FUZZY FACE OF CERES
Ron Baalke <baalke@jpl.nasadot gov>
(5) METEOROID AND ORBITAL DEBRIS IMPACT ANALYSIS
OF RETURNED ISS HARDWARE
Andrew Yee <ayee@nova.astro.utorontodot ca>
[...]
(8) LEONID LINKS
Michael Paine <mpaine@tpgi.com.au>
[...]
==========================================================================
(4) THE FUZZY FACE OF CERES
>From Ron Baalke <baalke@jpl.nasadot gov>
SKY & TELESCOPE'S NEWS BULLETIN - OCTOBER 12, 2001
For images and Web links for these items, visit http://www.skypub.com
THE FUZZY FACE OF CERES
When Guiseppe Piazzi discovered Ceres on January 1, 1801, he believed
he'd found the planet hypothesized to orbit between Mars and Jupiter.
Although Ceres is no planet, it turned out to be the largest body in
the asteroid belt. And now, two centuries later, astronomers finally
have a crude idea of what its surface looks like.
Thanks to the optical prowess of the Hubble Space Telescope, a team of
observers led by Joel W. Parker (Southwest Research Institute)
captured several images of Ceres on June 25, 1995, in ultraviolet
light (at which HST affords the best resolution). Previous
ground-based observations had resolved Ceres' disk, but only crudely,
using adaptive optics; by contrast, Hubble's images reveal details as
small as 50 kilometers across. Apparently the side of Ceres recorded
by HST is rather bland, except for one dusky dark marking about 250 km
across. As Parker and his colleagues describe in the forthcoming
January 2002 issue of the Astronomical Journal, it's unclear whether
this spot is a crater, a dark area, or something else. But they
believe it's a real feature, enough so to propose that it be named
Piazzi.
The 5-hour HST run was not long enough to follow Ceres through an
entire 9.1-hour rotation, but the pictorial coverage suggests a mean
diameter of 950 =B1 8 km. From that, as well as previous mass =
estimates,
the team determined that Ceres' mean density is roughly 2.6 g/cm^3 --
a reasonable match to the rocky, carbon-enriched composition suggested
by the asteroid's spectrum. Ceres occupies a roughly circular orbit
that averages 2.8 astronomical units (414 million km) from the Sun.
[snip]
Copyright 2001 Sky Publishing Corporation. S&T's Weekly News Bulletin
and Sky at a Glance stargazing calendar are provided as a service to
the astronomical community by the editors of SKY & TELESCOPE magazine.
Widespread electronic distribution is encouraged as long as these
paragraphs are included. But the text of the bulletin and calendar may
not be published in any other form without permission from Sky
Publishing (contact permissions@skypub.com or phone 617-864-7360).
Updates of astronomical news, including active links to related
Internet resources, are available via SKY & TELESCOPE's site on the
World Wide Web at http://www.skypub.com/.
==========================================================================
(5) METEOROID AND ORBITAL DEBRIS IMPACT ANALYSIS OF
RETURNED ISS HARDWARE
>From Andrew Yee <ayee@nova.astro.utorontodot ca>
[From July 2001 issue of ORBITAL DEBRIS QUARTERLY NEWS, NASA JSC]
Meteoroid and Orbital Debris Impact Analysis of Returned International
Space Station Hardware=20
By J. Hyde, E. Christiansen, & R. Bernhard=20
Three hypervelocity impacts were observed on the cylinder region of the
MPLM 1 after STS-102/5A.1. The impacts caused only superficial damage to
the outer bumper. The most significant of the three was a 1.44 mm
diameter hole in the 0.8 mm thick aluminum bumper of the Meteoroid
Debris Protection System (MDPS). It was determined from Scanning Electron
Microscope (SEM) analysis that the hole was caused by orbital debris, a
fragment of spacecraft paint approximately 0.5 mm in diameter. The other
two impacts produced craters in the MDPS bumper. There was no observed
damage to the MLI thermal blanket underneath or to the MPLM1 pressure
wall.
A BUMPER code analysis was performed with post-flight attitude data to
determine the regions of the MPLM1 cylinder that were most likely to be
hit by meteoroid and orbital debris particles in the general size ranges
of the observed impacts. All three impacts were near the region with the
highest risk. The analysis indicated that the bumper had a 1 in 5 chance
of being perforated during the 6 days of exposure and that orbital
debris was most likely to cause the penetration.
Five hypervelocity impacts were detected on the aluminum housing of an
EVA Safety Tether returned on STS-97/4A after nearly two years on orbit.
The largest impact, a 0.83 mm diameter by 0.45 mm deep crater, was
caused by an estimated 0.3 mm diameter orbital debris particle. SEM
analysis of crater residue revealed an abundance of silicon, indicating
that the impactor may have originated from a glass window or a solar
panel. The craters did not effect the on-orbit operation of the tether
or prevent its reuse.
Probability calculations using post-flight data indicated a 1 in 114
chance that the tether housing would be impacted by a 0.3 mm diameter
projectile during the two-year exposure period, an impact risk of less
than 1%.
IMAGE CAPTIONS:
[Figure 1:
http://www.orbitaldebris.jsc.nasadot gov/newsletter/v6i3/Meteoroid-Fig1.jpg=
]
MPLM bumper perforation risk plot, with impact locations noted.
[Figure 2:
http://www.orbitaldebris.jsc.nasadot gov/newsletter/v6i3/Meteoroid-Fig2.jpg=
]
Inspection of 21.2 cm (8.4 inch) long tether housing.
==========================================================================
* LETTERS TO THE MODERATOR *
==========================================================================
(9) LEONID LINKS
>From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
I created a new web page to cover the forthcoming Leonids meteor shower:
http://www4.tpg.com.au/users/tps-seti/leonids.html
Suggestions for extra links and news items are welcome. Australians
should be ideally located for viewing the predicted peak of the shower
before dawn on 19th November. I have to take a flight from Sydney to
Melbourne later that day to attend a conference. Although (I understand)
there is virtually no direct risk to aircraft there is an increased risk
of damage to GPS and communications satellites. I am therefore leaving
my departure at late as possible to let things settle down!
Regards,
Michael Paine
==========================================================================
(10) BALONEY DETECTION
>From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
The November issue of Scientific American has an excellent article on
baloney detection:
http://www.sciam.com/2001/1101issue/1101skeptic.html
See also Carl Sagan's Baloney Detection Kit:
http://www4.tpg.com.au/users/tps-seti/baloney.html
regards
Michael Paine
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