PLEASE NOTE:
*
CCNet 87/2002 - 23 July 2002
-----------------------------
"It took until early evening Monday at NEODyS in Italy to
update
their impactor table for 2002 NT7 with 13 new observations from
Sunday night. And no wonder. With this they have placed NT7's
February 1st, 2019 "virtual impactor" at a first-ever
positive Palermo Scale
rating of 0.18, up from yesterday's -0.11, which had been an
easing from
Saturday's -0.04."
--Asteroid/Comet Connection, 23 July 2002
"To that end, Worden suggested the creation of a Natural
Impact
Warning Clearing House, a body that would expand on NASA's NEO
work
and serve as more of an internationally minded Distant Early
Warning
system. One senses a bit of bureaucratic entrepreneurship here,
as the
Pentagon seeks to gain some astro-turf at NASA's expense, but
what's wrong
with that? Two entities competing to do the better job of
spotting NEOs
can only work to the good of the rest of us. Indeed, two
entities, each
with its own kind of credibility with the public, might do a
world of
good -- and do the world good -- in terms of public education
about the
threats we face. And so to the original concern: tangibilizing
the
intangible, not waiting until the asteroidal equivalent of
9-11."
--Jim Pinkerton, Tech Central Station, 22 July 2002
(1) FIRST EVER POSITIVE PALERMO SCALE 'VIRTUAL IMPACTOR'
ANNOUNCED - WITHOUT
IAU REVIEW
Asteroid/Comet Connection, 23 July 2002
(2) AUGUST'S FLYBY OF 2002 NY40
Daniel Fischer <dfischer@astro.uni-bonn.de>
(3) INTERAGENCY GROUP PROPOSED TO PROMOTE DEFENSE AGAINST
ASTEROIDS
AEROSPACE DAILY, 16 July 2002
(4) PREVENTING ARMAGEDDON
Tech Central Station, 22 July 2002
(5) DETAILS: FOUR ARRESTED IN NASA MOON ROCK HEIST
James Oberg <joberg@houston.rr.com>
(6) REMEMBERING GENE SHOEMAKER: "SCIENTIST SPECIALIZED IN
METEOR IMPACTS"
PITTSBURGH POST-GAZETTE, 22 July 2002
(7) RARE SPACE ROCK 'A GEM'
BBC News Online, 22 July 2002
(8) RIDING THE STONES
Andrea Carusi
(9) DON QUIJOTE (WHO IS AFRAID OF AN ASTEROID?)
Andrea Milani
(10) EARTHGUARD I
Stefano Mottola
(11) THE ISHTAR PROJECT
P. D'Arrigo
(12) REMOTE OBSERVATIONS OF NEOs FROM SPACE
Alberto Cellino
(13) THE EUNEOS PROJECT: LOOKING FOR NEOs FROM SPACE
A. Morbidelli and V. Martinot
(14) THE SIMONE CONCEPT: A FLEET OF SMALL SATELLITES EXPLORING
NEOs
Ettore Perozzi and Nigel Wells
(15) VIRTUAL RADIO TELESCOPE SEVERAL THOUSAND KM IN DIAMETER
Hermann Burchard <burchar@mail.math.okstate.edu]>
(16) AND FINALLY: THE LURE, BILL NAPIER'S NEW NOVEL
===========
(1) FIRST EVER POSITIVE PALERMO SCALE 'VIRTUAL IMPACTOR'
ANNOUNCED - WITHOUT
IAU REVIEW
>From Asteroid/Comet Connection, 23 July 2002
http://www.hohmanntransfer.com/news.htm
It took until early evening Monday at NEODyS in Italy to update
their
impactor table for 2002 NT7
(http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:2002NT7;risk)
with
13 new observations from Sunday night. And no wonder. With this
they have
placed NT7's February 1st, 2019 "virtual impactor" at a
first-ever positive
Palermo Scale (http://neo.jpl.nasa.gov/risk/doc/palermo.html)
rating of
0.18, up from yesterday's -0.11, which had been an easing from
Saturday's
-0.04. They and JPL, however, still have the 2019 impactor Torino
Scale
rating at 1.0.
JPL's NEO Program site this morning posted a new risk assessment
for NT7
(http://neo.jpl.nasa.gov/risk/2002nt7.html),
giving it a Palermo Scale
rating of -0.05 cumulatively, while specifically rating the 2019
event at
-0.10. Later in the day these ratings were revised to -0.15 for
the 2019
event (better), although the cumulative rating that incorporates
other later
possible events, especially one in 2035, is now -0.02 (worse) .
Sunday night's work includes nine observations from Siding Spring
in
Australia, which figured prominently in NEO searches until the
government
there cut funding.
Since 18 July, NEODyS and JPL have had NT7 at Torino Scale 1
("merits
special monitoring"). This is a large object with a diameter
estimated at
more than 2 km. (1.4 miles). It has a 42°-inclined orbit that
crosses the
orbit of Mars and barely crosses the orbit of Earth. It
approaches Earth
most closely from south of the ecliptic, where there is little
PHO
surveillance, and that, along with NT7's inclination, may be part
of why it
hasn't been spotted until now.
---
MODERATOR'S NOTE: It is interesting to note that NEODyS appear to
have
announced this first-ever positive Palermo Scale 'virtual
impactor' without
any formal IAU technical review. The IAU encourages such a review
for any
impact prediction that is at a level equal to or greater than
zero on the
Palermo Technical Scale (http://web.mit.edu/rpb/wgneo/TechComm.html).
According to the IAU guidelines, "information leading to an
impact
prediction, consisting of an evaluation of the case and all data
and
computational details necessary to understand and reproduce the
studies
carried out by the authors, should be transmitted for
confidential review to
the chair of the IAU Working Group for Near Earth Objects
(WGNEO), the
President of IAU Division III, the General Secretary of the IAU,
and the
members of the NEO Technical Review Team, before any announcement
and/or
written document on the subject be made public via any
potentially
nonprivate communication medium, including the World Wide Web.
The
individual members of the NEO Technical Review Committee shall
review the
work for technical accuracy and shall communicate under most
circumstances
within 72 hours the results of their reviews to the chair of the
WGNEO and
directly to the authors of the report or manuscript." It
seems obvious to me
and other critics that it is far too impractical to submit every
positive
Palermo Scale object for review. After all, neither the computers
at NEODyS
nor those used by JPL have ever experienced a problem with the
calculation
of impact probabilities. The pragmatic approach of turning a
blind eye to
the IAU procedures (if that's what happened over the weekend)
seems sensible
in the case of 2002 NT7 given that it is almost certain that
further
observations of this 2km asteroid will eliminate any remaining
impact
threats currently listed. Benny Peiser
=================
(2) AUGUST'S FLYBY OF 2002 NY40
>From Daniel Fischer <dfischer@astro.uni-bonn.de>
Hi,
the attached message has just arrived and should be of interest -
actually,
according to cfa-www.harvard.edu/iau/lists/Closest.html , our
August visitor
will be the biggest (known) one within 1 Million km from Earth
other than
Hermes in 1937 which was just a bit larger.
Regards, Daniel
------------
Date: Mon, 22 Jul 2002 14:00:51 +0100
From: "Roger W. Sinnott" <rsinnott@SkyandTelescope.com>
Subject: AstroAlert: AUGUST'S FLYBY OF 2002 NY40
==================================================================
This Is SKY & TELESCOPE's AstroAlert for Minor Planets
==================================================================
NEXT MONTH'S FLYBY OF 2002 NY40
In mid-August, a newly discovered asteroid will pass close enough
to Earth
that it should be easy to spot in small telescopes and even
binoculars. This object was first
detected on July 14th by astronomers using the LINEAR 1-meter
survey telescope in
New Mexico, and it has now been designated 2002 NY40 by the Minor
Planet Center in Cambridge, Massachusetts. According to
calculations by the center's associate director, Gareth V.
Williams, it is
traveling in a low-inclination, Apollo-type orbit with a period
of 3.03
years. Its August 18th flyby should bring it to within 530,000
kilometers
(330,000 miles) of Earth, which is just outside the Moon's
distance.
There are several key differences between this encounter and that
of 2002
MN, which made news a few weeks ago. That object came well inside
our own
Moon's orbit and was not detected until several days after the
fact. The new asteroid
was found on its way in toward the Sun, a full month before its
own flyby. But 2002
NY40 is about 10 times larger than 2002 MN; the best current
estimates make it
about half a kilometer (a third of a mile) across.
Still quite faint at magnitude 18 in the constellation Aquarius,
2002 NY40
is making a very tight loop around the star Beta Aquarii. During
the next
few weeks it will brighten tremendously
and yet remain almost motionless in the sky -- the eerie
signature of an
asteroid hurtling right toward the Earth! Then it veers off to
the northwest
as it goes by, racing past the double star Albireo in Cygnus for
observers
in the Western Hemisphere on the night of August 17-18.
On that Saturday evening, 2002 NY40 should become as bright as
magnitude 9.3
during the period when it is well placed for viewing from North
America. Its
angular velocity will exceed 4 arcminutes per minute, a motion
easily
perceptible in small telescopes. Sky & Telescope plans to
issue detailed
observing instructions, through AstroAlerts and
SkyandTelescope.com, in
the days leading up to this rare event.
A mere 24 hours after it goes by, 2002 NY40 plunges hopelessly
beyond reach
of Earth-based telescopes as it heads in toward the Sun. (We are
then
viewing its unilluminated backside, which explains why it becomes
so faint, so fast.)
Meanwhile, professional astronomers are gearing up to make the
most of this
encounter. "2002 NY40 is a potentially very good radar
target for
mid-August," notes Mike Nolan of Arecibo
Observatory and Cornell University. In a message posted on the
Minor Planet
Mailing List ( http://www.bitnik.com/mp
), Nolan urges advanced amateurs to
obtain detailed photometry of the asteroid on the nights leading
up to the flyby. A
good light curve, revealing the object's rotation rate, would
help in selecting the
instrumentation to be used with the Arecibo 1,000-foot radio
dish.
While there is no danger of 2002 NY40 striking the Earth during
this flyby,
a future impact has not been ruled out. Both NEODyS, operated by
the
University of Pisa, and NASA's Near-Earth Object
Program Office at JPL have identified a number of very close
encounters in
the years to come. These occur either around August 18th as the
asteroid
heads in toward the Sun, or else near February 14th when it is on
the way
out. Both agencies are focusing a flyby just 20 years from now
(on August
18, 2022), when there appears to be a 1-in-500,000 chance of an
impact --
extremely unlikely, but worrisome just the same.
Roger W. Sinnott
Senior Editor
Sky & Telescope
============
(3) INTERAGENCY GROUP PROPOSED TO PROMOTE DEFENSE AGAINST
ASTEROIDS
>From AEROSPACE DAILY, 16 July 2002
The U.S. government should form a senior-level interagency
working group to
develop an "integrated" approach for protecting the
planet from asteroids
and comets, according to a new paper by the American Institute of
Aeronautics and Astronautics.
AIAA wrote that the working group is needed to advise the
government on
creating or designating an office that would: coordinate
near-Earth-object
(NEO) detection activities; act as a single point of contact for
international activities; and assess U.S. planetary defense
research and
development options.
AIAA recommended that Air Force Space Command and NASA co-chair
the working
group.
The recent "near miss" of a football field-sized object
underscores the
threat posed by NEOs, yet there is no agreement on which
department or
agency speaks for the U.S. on planetary defense matters, the
paper says. The
object was not detected until after it passed within 75,000 miles
of the
Earth, or roughly one-third the distance to the moon.
An NEO that measured 100 meters (328 feet) across and crashed
into the sea
620 miles offshore could cause an on-shore wave over 10 stories
high. A one-
kilometer (.62 mile) NEO that hit the Earth would kill a quarter
of the
planet's population. "Clearly, the consequences of inaction
on the part of
the U.S. could be severe," AIAA wrote.
Copyright 2002 The McGraw-Hill Companies, Inc.
============
(4) PREVENTING ARMAGEDDON
>From Tech Central Station, 22 July 2002
http://www.techcentralstation.com/1051/defensewrapper.jsp?PID=1051-350&CID=1051-072202A
By Jim Pinkerton 07/22/2002
How does one tangibilize the intangible? That is, how does one
get people to
think about something that has not happened-or more precisely,
has not
happened in a long time?
That's the challenge faced by folks who, for example, want to
sell disaster
insurance. You might have seen those TV commercials in which
earnest
pitch-persons urge people to buy flood-insurance policies. That's
a good
idea, although oftentimes, of course, Uncle Sam bails people out
whether or
not they were prudentially prepared for disaster. But there are
other kinds
of disasters for which insurance may come too late, for which the
only real
strategy is prevention.
That was the subject of a recent conference at the Dirksen Senate
Office
Building on Capitol Hill in Washington: "The Asteroid
Threat: Identification
and Mitigation Strategies."
OK, OK, it's true that America and the world are not under active
assault
right now from deep-impacting, Armageddon-inducing space rocks.
But that's
the point: we're not getting blasted right now, so we should be
insuring
ourselves now. In America, at least, floods are manageable; they
are matters
of millions, maybe billions, of dollars. But an asteroid strike
could take
millions, and maybe even billions, of lives.
Life-annihilating strikes have happened at least five times in
planetary
history, including one such smack-down 65 million years ago.
That's when a
rock no more than a dozen kilometers across struck the Yucatan
Peninsula in
what's now Mexico and put the dinosaurs down for the eonic count.
Yes, that was a long time back, the Cretaceous Period, to be
exact. But just
40,000 years ago -- not such a far piece, in the human scheme of
things -- a
35-meter space stone hit Arizona, leaving a crater that many
Americans have
been to visit. It's fun now to see it as a tourist, but it
wouldn't have
been such a joy to be there when it hit with the force of 300
Hiroshima
bombs.
And just in the last century, in 1908, another space particle, no
more than
60 meters across, exploded over Tunguska, Siberia, with the force
of 600
Hiroshima A-bombs, reducing a 40-kilometer wide patch of forest
to kindling.
If the Tunguska bolide had hit further east at the same latitude,
it would
have hit the Russian city of St. Petersburg, and that space rock,
which
merely wiped out unlucky herds of reindeer, would have been a
mini-death
star, a cosmic weapon of mass destruction.
Indeed, that's part of the challenge: to realize that an angry
God, or at
least an angry universe, is constantly raining devastation in our
general
direction -- and it's only a matter of time before we get hit
again, hard.
Once that chilling realization is absorbed, the further and
greater
challenge is to get people thinking about safeguarding
themselves.
Prolife, Prospace
These grim and yet profound challenges have been taken up by
Prospace, a
grassroots space-advocacy organization on July 10. In the words
of Prospace
president Marc Schlather, "It's sort of like 9-11. People
ignored the threat
until it happened." Only after that tragedy, and billions
spent on recovery,
Schlather observed, did America commit billions to terror
prevention.
A similar effort, Schlather declared, is needed now. He's right.
We need to
look ahead, to a disaster of epochal proportions, and then we
need to work
backward from the extinction-level event we don't want to see --
and figure
out how we can protect ourselves, our posterity, and our planet.
Because, declares Brian Marsden, director of the Minor Planet
Center at the
Harvard-Smithsonian Center for Astrophysics, the threat is all
around us. At
least 16 objects of potentially devastating size, he told the
Prospacers,
have passed near the earth -- "near" defined as within
twice the distance
between earth and the moon, or about 384,000 kilometers. One such
NEO --
Near Earth Object -- perhaps 15% larger than the
Tunguska-destroyer, zipped
within 120,000 kilometers of spaceship earth on June 14, although
ominously,
astronomers didn't detect it until three days after its fly-by.
In fact, an
estimated 1000 NEOs, measuring one kilometer or larger, swirl
through our
galactic neighborhood.
Getting Paranoid About 'Roids
So what to do? If all humanity is threatened by NEOs' getting too
close for
comfort, then all humanity should band together in support of the
technology
needed for defense. And that leads, in the long run, to scenarios
seen in
'90s films such as "Armageddon" and "Deep
Impact," in which earthlings
develop the capacity to deploy into space to destroy or deflect
incoming
'roids.
Underscoring the seriousness of these scenarios, Congressman Dana
Rohrabacher (R-Calif.), chairman of the Space and Aeronautics
Subcommittee
of the House Science Committee, spoke at the conference,
endorsing its
high-concept mission. He praised "dual use" technology
that would
"piggyback" planetary defense on top of strategic
missile defense, an issue
that Rohrabacher has been intimately involved with since serving
as a
presidential speechwriter in the Reagan White House. NEOs are
"a grave
threat we should be investing in," he maintained.
Interestingly, Rohrabacher went further, demonstrating that he
wasn't just a
typical politician, volunteering to spend extra money to solve
every
problem. The Golden State GOPer was very specific when he
suggested that
funds for climate change research could and should be diverted to
earth's
defense.
Obviously Rohrabacher is an optimist -- optimistic that good
science will
drive out bad science, that a better calculus for real and
imagined threats
will be developed. But in the meantime, those not quite so
optimistic about
sound policy-making should still be appropriately realistic about
astro-defense.
And the beginning of a realistic strategy is getting a handle on
the threat.
Great Britain has been a leader in NEO-identification (sic!);
Italy has an
energetic space-watch program as well (sic!). The United States,
according
to program speaker Colleen Hartman, Director of NASA's Solar
System
Exploration Division, spends about $4 million annually on its
Near Earth
Observations Program.
Causes and Effects
But that's not enough, insisted Air Force General Simon
"Pete" Worden,
Deputy Director of Operations, U.S. Space Command. The threat
from NEOs is
even greater than the once-a-century risk of a Tunguska-like
strike, he told
the Prospacers. An even more immediate concern is that 30 or so
small
asteroids hit the earth's upper atmosphere every year. These
rogue rocks can
cause detonations the size of Hiroshima, but they remained mostly
harmless
-- until we entered the anxious age of nuclear proliferation, in
which enemy
countries stare down at each other in unblinking anger. Recalling
such a
space blast occurring over the Mediterranean on June 6, Worden
wondered what
might have happened if the shallow-impact rock had struck along
the same
latitude in a place where nerves were already strained nearly to
the nuking
point:
Imagine that the bright flash accompanied by a damaging shock
wave had
occurred over Delhi, India, or Islamabad, Pakistan. Neither of
those nations
have the sophisticated sensors that can determine the difference
between a
natural NEO impact and a nuclear detonation. The resulting panic
in the
nuclear-armed and hair-trigger militaries there could have been
the spark
that would have ignited the nuclear horror we'd avoided for over
a
half-century. This situation alone should be sufficient to get
the world to
take notice of the threat of asteroid impact.
To that end, Worden, emphasizing that he was speaking for
himself, not for
the Air Force, suggested the creation of a Natural Impact Warning
Clearing
House, a body that would expand on NASA's NEO work and serve as
more of an
internationally minded Distant Early Warning system. One senses a
bit of
bureaucratic entrepreneurship here, as the Pentagon seeks to gain
some
astro-turf at NASA's expense, but what's wrong with that? Two
entities
competing to do the better job of spotting NEOs can only work to
the good of
the rest of us.
Indeed, two entities, each with its own kind of credibility with
the public,
might do a world of good -- and do the world good -- in terms of
public
education about the threats we face. And so to the original
concern:
tangibilizing the intangible, not waiting until the asteroidal
equivalent of
9-11. As Rick Tumlinson, director of FINDS -- the Foundation for
the
International Non-governmental Development of Space -- said in a
ringing
speech, asteroid defense should be a part of homeland defense.
Because the
earth, and not just America, is our true homeland, we should be
doing
everything we can to protect it and, in so doing, protect
ourselves.
© 2002 Tech Central Station
=============
(5) DETAILS: FOUR ARRESTED IN NASA MOON ROCK HEIST
>From James Oberg <joberg@houston.rr.com>
Relayed from Robert Pearlman, editor, collectSPACE.com
robert@collectspace.com
http://collectspace.com/news/news-072202a.html
July 22 -- The Federal Bureau of Investigation (FBI) and the NASA
Office of
Inspector General (OIG) announced today the successful recovery
of lunar
samples stolen by student employees working at NASA's Johnson
Space Center
(JSC) in Houston, Texas.
James F. Jarboe, Special Agent in Charge, FBI Tampa Division, and
Lance
Carrington, NASA OIG Assistant Inspector General for
Investigations,
announced the arrests of Thad Ryan Roberts, age 25, Tiffany
Brooke Fowler,
22, Gordon Sean McWorter, 26, and Shae Lynn Saur, 19, for the
theft of lunar
samples returned from each of the six Apollo missions.
On July 13, the four allegedly stole a 600-pound safe housing the
rocks --as
well as reportedly a fragment of the ALH 84001 "Martian
life" meteorite --
from Building 31, NASA's main repository for Apollo lunar
samples.
In an interview with MSNBC.com, NASA spokesman Kyle Herring said
the safe
included "53 different lunar samples, amounting to 5 ounces
(142 grams); and
165 meteorite samples, also amounting to 5 ounces. 'None of the
samples was
pristine,' he said; rather, all of them had been 'degraded by
previous
analysis.'"
Roberts, Fowler and McWorter were taken into custody late
Saturday in
Orlando, Florida, and charged with Conspiracy to Commit Theft of
Government
Property and Transportation in Interstate Commerce of Stolen
Property.
Saur was arrested in Houston and also charged with Conspiracy.
Student employees at JSC, Roberts, Fowler, and Saur were
dismissed from
their respective employment programs based on their involvement
in the case.
Jarboe stated that since May 2002, an FBI undercover operation
had utilized
e-mail to communicate with an individual offering "priceless
moon rocks,"
which the individual described as "the world's largest
private and
verifiable Apollo rock collection."
According to a report filed by the Associated Press, Roberts
initially
posted the offer to the website of the Mineralogy Club of
Antwerp, Belgium.
With sale prices of $1000 to $5000 per gram, Roberts appeared to
be familiar
with the laws governing the sale of astromaterials.
"As you well know, it is illegal to sell Apollo lunar rocks
in the United
States," wrote Roberts in an e-mail quoted by the AP.
"This obviously has
not discouraged me since I live in the United States. However, I
must be
cautious that this deal is handled with delicacy in that I am not
publicly
exposed."
The e-mail messages were sent from several locations -- the
University of
Utah, Johnson Space Center and a public library in Houston.
The continued exchanges included curatorial and historical
records on the
samples provided by the seller, and culminated in a meeting at a
restaurant
in Orlando over the weekend of July 20, to finalize the purchase.
The defendants arrested in Orlando appeared before U.S.
Magistrate Judge
Thomas B. McCoun on July 22.
Citing Jarboe, the AP reported "that with the current
charges the suspects
each face up to five years in prison, but more charges are
likely."
The FBI began the investigation after receiving a tip through an
e-mail
address established by the Tampa Division for Internet Fraud
Matters.
© 1999-2002 collectSPACE.com All rights reserved.
===========
(6) REMEMBERING GENE SHOEMAKER: "SCIENTIST SPECIALIZED IN
METEOR IMPACTS"
>From PITTSBURGH POST-GAZETTE, 22 July 2002
Gene Shoemaker died in a car accident July 18, 1997, while
searching for
meteor craters in Australia. He was a planetary scientist who
specialized in
meteor impacts and the role they played in shaping the solar
system. His
passion was astrogeology, and he dreamed of going to the moon.
Shoemaker pioneered research on the formation of impact craters
on planetary
bodies. He also discovered numerous Earth-crossing asteroids and
comets.
Shoemaker, his wife, Carolyn, and colleague David Levy are best
known for
discovering Comet Shoemaker-Levy 9, which crashed into Jupiter in
1994. The
Shoemakers were the leading discovers of comets in this century
and are
credited with discovering more than 800 asteroids.
In the late 1950s while studying the rubble at the bottom of
Barringer
Crater in Arizona, Shoemaker discovered coesite, a mineral
created only
during impacts. With the discovery of this mineral, geologists
were able to
identify many more impact craters on Earth. This discovery led to
the theory
that catastrophic impacts may have caused mass extinctions in the
past.
Shoemaker dreamed of being the first geologist to map the moon;
but health
problems prevented him from becoming the first
astronaut-geologist. He still
helped train the Apollo astronauts about what rocks and minerals
to bring
back to Earth. During those historic Apollo moon walks, he sat
beside Walter
Cronkite, giving commentary on the evening news.
After his death, his colleagues and friends placed a capsule
carrying an
ounce of his cremated remains in the Lunar Prospector spacecraft.
When the
probe crashed Aug. 31, 1999, into a dark crater near the moon's
South Pole,
it deposited the ashes on the lunar surface.
Copyright 2002 PG Publishing Co.
=================
(7) RARE SPACE ROCK 'A GEM'
>From BBC News Online, 22 July 2002
http://news.bbc.co.uk/hi/english/sci/tech/newsid_2144000/2144150.stm
By Helen Briggs
BBC News Online science reporter
British scientists have confirmed that one of the rarest
meteorites ever to
fall to Earth is from a time when the Solar System was born. It
provides a
glimpse of a period, 4.5 billion years ago, when the planets were
beginning
to form.
The chunk of space rock is higher in extra-terrestrial material
than any
other meteorite and may belong in a class of its own, say
researchers at
London's Natural History Museum.
A team led by Dr Sara Russell is one of a handful around the
world that is
analysing slivers of the rock. It came down over Tagish Lake, a
remote area
of northern Canada, on 18 January, 2000.
Fragments landed on a frozen lake and were preserved in ice
almost
immediately.
By a stroke of luck, they were found by someone who knew to keep
them cold
and not to touch them.
"It turns out that this meteorite is a really unique
sample," says Dr
Russell. "It's higher in extra-terrestrial organic material
than any other
meteorite."
Building blocks
Research at the museum has confirmed that the Tagish meteorite is
"extremely
primitive" in its chemical composition. It has changed
little since it first
arose "in the very earliest stages of the Solar
System," says Dr Russell.
Tiny grains in the rock should reveal new information about the
dust and
gases that came together to make the planets.
"Our work on Tagish lake is very much work in progress at
the moment," Dr
Russell told BBC News Online. "What we think we've found is
that this is a
sample of the very earliest building blocks of the materials that
went on to
make up the planets in our Solar System."
The sample gives scientists a chance to learn more about how the
planets
formed.
It could also reveal whether or not other Earth-like planets are
likely to
be found around other young stars.
Space gems
The meteorite is from a class known as the carbonaceous
chondrites. These
primitive, carbon-rich space rocks contain organic compounds such
as amino
acids. They also contain tiny jewels in the form of pre-solar
diamonds and
sapphires.
The meteorite was seen for miles
These would have been made around the stars that were the
ancestors of the
Sun, and can tell scientists about the processes that occur
inside stars.
Emma Bullock, a postgraduate student in the department, is
working on the
composition of the meteorite for her thesis. "It's unlike
any other
meteorite we've ever seen so it possibly belongs in a group all
of its own,"
she says.
"There are [compounds containing the element sulphur] in
this meteorite that
aren't found on Earth and there are also some very unusual shapes
of
sulphide.
"It's got some other very interesting features," she
adds. "It's been
altered by water but not really by heat so that's affected some
of the
minerals."
Copyright 2002, BBC
====================================================================
PIPE DREAMS OR FUTURE POSSIBILITIES? EUROPEANS PLAN NEW NEO
MISSIONS
====================================================================
(8) RIDING THE STONES
>From Tumbling Stone, 25 July 2002
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/eng/introduction.htm#phase-a
by Andrea Carusi - Copyright Tumbling Stone 2002
Six spacecrafts to study NEOs. This is a possible scenario that
will be
studied in the next six months by ESA. In this number of Tumbling
Stone we
present the six projects that have been selected by the European
Space
Agency for a Phase A study (see box: "The preliminary phases
of a space
mission") and that will be illustrated at ESRIN on Jun
25-26. There is a
variety of different approaches: from observatories devoted to
discovery and
physical characterization to rendez-vous (see dict.) aimed at
mapping the
objects' interior, to combined missions designed for studying
possible
deflection maneuvers.
The projects are here illustrated by scientists assisting the
Companies that
have passed ESA's selection. The common denominator of all of
them is that
there are studies related to NEOs that can only be done from
space, and the
Agency has taken the initiative to open a phase of broad
reconnessaince of
the possible options offered by to-date space technologies in
this important
field. Probably none of these studies will really materialize in
a real
mission; nonetheless, it is important that one of the largest
space
agencies, already deeply involved in support of NEO studies, has
decided to
make a further step in this direction.
When the Spaceguard Foundation was set up, in 1996, the status of
the NEO
research was still in its infancy: the impact problem was already
recognized
as an important one, but nobody could have anticipated the real
explosion of
programs and investigations that have followed since then. At
this time we
are almost halfway in mapping the population of NEOs larger than
1 km, the
ones that poses the largest threat to humankind, and we have set
up an
international system able to coordinate researches all over the
world.
Sure, there is still a lot to do, and the mechanisms that have
been put in
operation are not perfect (sometimes quite inefficient), but the
important
aspect of the history of these last 6-7 years is that the
cooperation among
hundreds of scientists and amateurs is firmly established as the
only way
for an efficient program. The role of space agencies has now been
clearly
identified: to study the contribution that space projects may
give to the
global system and to support the coordinating centers.
I'm particularly happy for the opportunity given by the start of
these six
projects: the SGF was founded exactly to foster international
involvement at
all levels, and it is now commonly accepted that the the study of
NEOs is
not just the study of another scientific topic, but a service to
the
international community. ESA and NASA are doing their part of the
job, but
the issue is already being studied at a more political level by
organizations such as the United Nations and the Organization for
the
Economic Cooperation and Development. That is to say that
non-scientists are
now aware that there is an issue, and that we need to examine it
carefully
in order to identify possible actions to be taken.
I'm also particularly happy to see that the SGF has been
instrumental to
reach this result. The six ESA projects will be overviewed by the
Spaceguard
Central Node, that is being moved to ESRIN in these days. It is a
result of
all the dedicated people that have devoted a large fraction of
their time to
the development of the SGF, and I want to express here my
appreciation and
my thanks to all of them.
Andrea Carusi - President of the Spaceguard Foundation
---------------
The preliminary phases of a space mission
An original idea for a space mission takes usually birth in the
science
community, from an individual or group. This idea is first put in
the form
of a Pre-Phase-A conceptual study, which can be presented to ESA
or NASA
where it is studied and evaluated for merit.
At this point, if the idea is accepted (as in the case of the 6
projects of
missions to NEO) Phase-A takes place. A Phase-A study is a
Preliminary
Analysis of the mission: the team of the project creates a
preliminary
design and project plan specifying what to build, when to launch,
the course
the spacecraft is to take, what is to be done during cruise, when
the
spacecraft will reach the target, and what operations will be
carried out.
This preliminary plan also indicates what spacecraft instruments
are needed,
where system tests will be performed, who performs mission
operations, what
ground data system capabilities are required, and who the
experimenters are.
Generally speaking, publication of the preliminary plan with
costing data
marks the completion of this phase.
After Phase-A there will be two other study pahses: a definition
phase
(Phase-B), during which the preliminary plan is converted into a
baseline
technical solution, and a design and developement phase (Phase
C/D). Only
after all these phases the last,Operations Phase takes place.
==============
(9) DON QUIJOTE (WHO IS AFRAID OF AN ASTEROID?)
>From Tumbling Ston, 25 July 2002
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/eng/quijote.htm
by Andrea Milani (*) - Copyright Tumbling Stone 2002
The spacecraft has been travelling in ostensibly empty space for
quite some
time, then a small speck of light appears, as dim as a magnitude
9 star.
Very quickly, it becomes brighter and brighter: after 20 hours it
is
magnitude 5, would be visible to the naked eye... if there was a
man on
board. In the last hours, the spacecraft is rushing to the
encounter with
the starlet, which in fact is a small, but nearby, asteroid, In
the last few
minutes the small planet appears with its irregular shape,
punched with
craters. But this is not just another asteroid fly-by. The
spacecraft points
directly against the asteroid, even making last hour adjustments
to be sure
to hit, and finally smashes at more than 10 kilometres per second
against
its target, just slightly off centre. A sizable crater is
excavated, and a
cloud of debris is ejected from it; the asteroid even changes
slightly its
rotation, and its orbit is affected by a minute amount,
imperceptible unless
the most accurate instruments are used to measure it.
It is over? Not yet. While the cloud of ejecta is spreading to
form a kind
of ring around the wounded asteroid, another spacecraft comes out
of hiding
from behind the small planet. It sweeps through the cloud of
dust, with
minute windows collecting samples. It also flies over a few
locations on the
asteroid, where long wire antenna come out from holes dug in the
fine
grained surface. The seismometers have done their job. the
advanced tracking
system can measure the deflection imparted by the kamikaze
spacecraft. From
a terrible act of destruction, knowledge is gathered. For a
scientist
moonlighting as a Science Fiction writer, like myself, it is not
difficult
to imagine being spectator of such an event (of course from the
bridge of an
alien spaceship). What would E.T. think of this? Are the natives
of the
third planet gone crazy? Why are they using two spacecraft to
explore a
minuscule body? And why the fiery sacrifice of one of the two? It
would be
difficult for them to understand that this apparent madness is,
in fact, a
very good reason to believe that mankind is able to act
rationally in the
pursuit of its own interest.
What else to do about an asteroid?
With the very successful NASA mission NEAR-Shoemaker (see T.S.
number 1 "How
to land on an asteroid" by A.Milani), the first asteroid
orbiter, our
understanding of the nature of the smaller bodies of our solar
system has
progressed substantially. Moreover, there is a string of
approved missions
to small bodies, including the ESA comet orbiter Rosetta, which
will also
fly by two asteroids (see T.S number 12 : "Mission
Rosetta" by L.Giacomini),
the NASA Dawn mission (Ceres and Vesta orbiter) and the Japanese
asteroid
lander MUSES-C, the NASA comet missions Stardust, CONTOUR, and
Deep Impact.
Thus within few years there will be even more progress and
understanding.
In this context, the Announcement of Opportunity of ESA (see
editorial of
this issue: "Riding the stones" by A.Carusi) for
proposing "yet another
mission to asteroids" could be a source of embarrassment.
Are the scientists
specialized in asteroids overdoing it, asking for more out of
some kind of
scientific greed? What else can be proposed, which is not (and
does not even
appear to be) a duplication? A correct answer to this question
requires to
identify a scientific problem on the nature of asteroids which is
not
addressed at all by these approved missions, and is nevertheless
fundamental. Moreover, just for once the scientists have to be
prepared to
answer to the questions: fundamental why? Fundamental for whom?
It has to be
fundamental for you, man of the street, part of a public larger
than the one
interested in basic knowledge.
The internal structure of an asteroid
There is indeed an outstanding scientific problem about
asteroids: the
internal structure. There are many asteroids, and that is why
they can
collide with each other (as well as with the planets). The
collisions
disrupt the solid body of the asteroids, to the extent that only
few very
large ones (Ceres, Pallas, Vesta, and few more) can still be in
one piece,
like the major planets. Very energetic collisions can shatter an
asteroid
and generate a "family" of fragments, each one orbiting
the Sun on its own.
Intermediate energy collisions can break the target asteroid into
pieces,
leaving a "rubble pile" held together by mutual
gravity. The images of
asteroid Eros shown by NEAR-Shoemaker suggest a composite
structure,
possibly consisting of a small number of large pieces with a
scatter of
small fragments "filling the gaps" between the major
ones, a spray of sand,
pebbles and boulders to cover up the structure and form the
surface with its
strange "beaches". None of the proposed missions to
asteroids can indeed
solve this problem, because it is easy to take images and spectra
of the
surface, but to probe the interior is much more challenging.
Let's suppose this is the "fundamental" scientific
problem. Why do we care?
If "we" means the scientists, there are many good
reasons why: the evolution
of the asteroid belt, the formation and delivery of Near Earth
Asteroids
(NEA) and of meteorites, thus the cratering of the terrestrial
planets, all
depend upon the collisional evolution of the asteroids. But, if
"we" means
everybody, is this question important enough?
In case of need
As you know, Tumbling Stone is the public information interface
for two
research groups, which could be referred to by their web
interfaces, NEODyS
and Spaceguard Central Node (SCN). Our work has to do with
monitoring the
new discoveries of NEA and checking if some of them has the
possibility of
impacting the Earth in the foreseeable future. The work is shared
in this
way: NEODyS performs the computations (of the orbit, of the
future possible
evolutions, of the future close approaches, including the
possible
collisions); SCN organizes observation campaigns (to avoid that
any NEA gets
lost, but in particular to recover and improve the orbits of
possible future
impactors). We believe it is a good team work, and successful, in
that the
"Virtual Impactors" (see dict.) are removed very
efficiently and reliably.
But, is this work really useful? What was to happen if, one
unlucky day, we
were to discover a Virtual Impactor which refuses to go away? The
probability of a future impact is only used as a measure of our
lack of
information, as observational data accumulate the probability
must go to
either zero or one.
What if, in one case, we end up by getting a probability 1, or at
least 0.9,
that is an impact which is certain, or at least very likely? If
we had no
strategy available to handle such a case, one might wonder why we
wish to
know of a future catastrophe we are not able to avoid anyway.
Such a scenario is not very likely: according to our standard
model (see
http://neo.jpl.nasa.gov/risk/doc/palermo_paper.html)
an asteroid a diameter
of 500 m or larger would hit the Earth (releasing an energy of
about 7,000
MegaTons) on average once every 40,000 years. Thus the
probability that we
will really discover that such an event would really occur in the
next 100
years is roughly 1 in 400. However, we cannot be unprepared; that
is, we
need to have contingency plans for such an event, which is
unlikely but far
from impossible. otherwise, one day we may be forced to make an
announcement
of the kind: "Sorry, folks, a continent is going to be wiped
out and we do
not know what to do about it".
Thus the question is: how to deflect an asteroid? More precisely,
do we have
the know how, the technology to deflect an asteroid?
Also as a result of the influence on the public opinion of some
low quality
science fiction movies, most people believe that the main
problems in
deflecting an asteroid are the risk for human astronauts and the
availability of large enough spaceships and powerful enough
destructive
weapons. Of course human astronauts are not likely to be involved
at all in
an asteroid deflection, and the nuclear warheads unfortunately
well
available for other purpose are more than enough to either
deflect or blow
up sizeable asteroids, certainly including the case of an object
about 500
meters in diameter we were discussing above. The problem is
that deflecting
an asteroid is not necessarily a good idea, unless we have a very
good
control on the amount and direction of the change of course.
Blowing up an
asteroid, unless we have a very good control on the size of the
resulting
pieces, can also not decrease the damage, or at least not enough.
Thus the
main requirement for an asteroid deflection procedure is to know
whether the
asteroid would remain in one piece after being hit in very
energetic way;
thus not knowing the internal structure is a major problem.
Surprise: the
main limitation to our asteroid-deflecting capabilities, the true
reason why
they still belong to science fiction rather than to sound
technology, is the
lack of knowledge, not the lack of firepower.
The above conclusion also eliminates a nasty problem, which has
been the
source of unpleasant polemics in the community interested in NEA.
What does
it mean to "get ready" for asteroid deflection? If the
problem was one of
firepower, then to get ready would mean to build bigger rockets
and possibly
bigger nuclear warheads. But, the potential for misuse of such a
weapon are
more frightening than any asteroid. Moreover, it appears
difficult to
justify the cost of such super-rocket and/or super-bomb
preparations, for an
event which is most likely not to take place within the
operational lifetime
of whatever device we can now build. If, on the contrary, to get
ready means
to gather knowledge, this is not only less expensive but very
unlikely to
have negative side effects. If this can be achieved with a
scientifically
worthwhile investigation, the effort and the cost can be
justified.
Don Quijote: the Hidalgo and his servant Sancho
>From the above discussion the logic behind the proposal for
the "Don
Quijote" mission is clear: we want to investigate the
internal structure of
an asteroid, and at the same time develop and test the technology
necessary,
in a worst case scenario, to deflect a sizeable asteroid.
Our solution to
this problem was presented as an answer to the ESA Invitation To
Tender for
a Near Earth Object mission proposal, and has been accepted by
ESA for a
feasibility study. The industrial proponents are Deimos Space
S.L. (Spain,
principal contractor) and Astrium GMBh (Germany). Myself with my
co-workers
of NEODyS and Giovanni Valsecchi with his co-workers at SCN are
contributing
the definition of scientific goals and requirements. Other
groups
contribute to other aspects of the proposal, not discussed here.
The top level definition of the mission is as follows: there need
to be two
spacecraft, one named Hidalgo will intercept a small asteroids
(nominally
500 meters in diameter) at a relative speed of at least 10
kilometres per
second, and impact on it. The second spacecraft, Sancho, will
rendezvous
with the same asteroid a few months in advance, measure carefully
the
asteroid and possibly deploy a few penetrators with
seismometers. At the
time of the impact, Sancho will retreat to a safe distance to
observe the
impact without taking unnecessary risk (with an attitude
appropriate to its
name). It will later return to a close orbit, to observe the
changes in the
orbit and rotation state of the asteroid, and to collect samples
from the
dust ejected by the crater formation. It will also collect the
data from the
penetrators, including the seismic data from the impact itself.
The technological challenge
Where is the high technology in such a blunt approach? To
appreciate this
you need to take into account some numbers, resulting from the
simplest
physics of such an impact. A 400 kg spacecraft impacting at 10
km/s onto a
500 m diameter asteroid (weighing something like 170 million
tons) should
change its speed by at least 24 microns per second. That is, one
day after
the impact of Hidalgo the asteroid should be displaced by at
least 2 meters
with respect to the position it would have had without the
deflection. The
exact value is not known in advance (it is the result of the
experiment) and
will depend in a complex way upon the dynamics of the fragments
ejected from
the artificial crater on the asteroid. Still, 2 meters out of
some hundred
million kilometres of distance from the Earth is like one part in
50,000,000,000. Thus some really advanced technology has to be
used to
measure the effect of the deflection!
In this the second spacecraft, Sancho, plays a very important
role. It is
Sancho which is equipped with the instruments for a very
sophisticated Radio
science Experiment. It will orbit around the asteroid, but its
orbit is
strongly perturbed by many secondary effects, including the
irregular shape
of the asteroid, which needs to be determined in the phase before
the impact
of Hidalgo, and radiation pressure plus other non gravitational
perturbations, to be measured with an ultra sensitive
accelerometer. These
measurements will in fact be very similar to the ones already
planned for
the ESA BepiColombo mission, a Mercury orbiter, scheduled to be
launched in
2011. Thus they are based on European technology either already
available or
under development for another approved mission.
Is this for real?
The question will be asked: is this deflection experiment the
same thing as
a real deflection, the one we would need in the worst case
scenario, in case
a real asteroid is known to be on a collision course with the
Earth? This is
only an experiment, to acquire know how. The requirement
for Don Quijote is
not to perform a deflection of the amplitude (in the velocity
change of the
asteroid obtained) comparable to the one we would need in an
actual case.
The examples computed by Carusi and co-workers (see T.S. number 9
"We only
need a little, gentle kick..." by A.Carusi ) indicate that
in some cases,
with the dynamics of the asteroid-Earth encounter controlled by
the so
called "resonant returns" ( see T.S. number 14
"The reason why Clomon2 is
smarter than Clomon" by G.Valsecchi) , a deflection of less
than 100
micron/s could be enough; in other cases, the values could be
larger by two
orders of magnitude. That is, what we propose is not to simulate
the
deflection of an asteroid by an amount sufficient to avoid a
collision. We
propose to simulate the experiment which would need to be done,
on the
specific "dangerous" asteroid, to be able to control in
a reliable way the
true deflection to be done later, probably with a much bigger
impactor. That
is, a real deflection would require three spacecraft, the first
two very
much like Hidalgo and Sancho, the third one should be
significantly more
massive. But the larger deflection, to be imparted by the third
spacecraft
(propose a name!), would be predicted accurately thanks to the
experiment
performed with the impact of another Hidalgo and measured by
another Sancho.
That is, two out of three spacecraft needed for the real
deflection would be
just copies of the Hidalgo and Sancho prototypes tested in the
Don Quijote
mission.
Andrea Milani - Director of NEODyS
===============
(10) EARTHGUARD I
>From Tumbling Stone, 25 July 2002
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/eng/earthguard.htm
by Stefano Mottola (*) - Copyright Tumbling Stone 2002
The Earthguard I project, proposed by the Munich-based aerospace
company
Kayser-Threde and the German Aerospace Center (DLR) in Berlin, is
one of the
studies the European Space Agency (ESA) has selected for the
preparation of
new space missions for the study of Near Earth Objects. The goal
of the
study is to define a space mission and a dedicated payload
concentrating on
the detection of those NEOs whose orbits lie mostly or entirely
within the
orbit of the Earth. The former group of objects is known as Atens
(named
after asteroid 2062 Aten which was the first of this class to be
discovered)
while the latter are referred to as Inner-Earth-Objects, or, in
short IEOs.
While these objects can occasionally come very close to our
planet, they are
very difficult to detect from the ground because this particular
observing
geometry places them at small angular distances from the Sun for
most of the
time, making them invisible against the bright sky background. It
is exactly
this difficulty that, until now, has prevented observers from
discovering
IEOs, although their presence in the inner regions of the Solar
System has
been predicted by dynamical studies and is generally accepted by
scientists.
The Earthguard I mission overcomes this problem by making use of
a compact
search telescope mounted on a spacecraft in a heliocentric orbit
in the
inner Solar System. From this vantage point, not only would Atens
and IEOs
be more easily detected against a dark sky background, but they
would also
appear brighter due to the smaller solar phase angle, the same
way the full
Moon appears much brighter than the crescent Moon.
In this way such an instrument could detect objects down to about
100 m,
accurately determine their orbits, estimate their size, and
establish their
orbital and size distribution. All these parameters are of
crucial
importance not only for their scientific interest, but also for
better
understanding the hazard those objects pose to our civilization.
For this
reason this space-based detection system is to be seen as
integrating and
complementing the activities performed by the ground-based search
programs.
The mission could either use a dedicated spacecraft, or,
alternatively, fly
"piggy-back" on a platform planned for other studies,
as a Mercury or a
Venus orbiter. In the case of a dedicate spacecraft Earthguard I
would make
use of a solar sail as a propulsion system. This innovative
technology, for
which DLR has already developed functional models, has the
advantage of
allowing a very compact spacecraft to be developed, compared to a
conventional chemical propulsion system, therefore reducing the
total cost
of the mission.
Stefano Mottola - DLR - German Aerospace Center
================
(11) THE ISHTAR PROJECT
>From Tumbling Stone, 25 July 2002
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/eng/ishtar.htm
by P. D'Arrigo - Copyright Tumbling Stone 2002
ISHTAR (Internal Structure High-resolution Tomography by Asteroid
Rendezvous) is a proposed mission to image the interior of an
asteroid using
a powerful new technology: Radar Tomography (that is, the imaging
of the
interior of a solid object using ground-penetrating radar). The
ISHTAR
mission design is centred around this Radar Tomography payload,
capable to
probe the interior of a small asteroid to depths of 100-200m,
combined with
an imager for surface characterization and a radio science
experiment to
measure the asteroid mass.
This unique combination will allow the first detailed
characterization of a
NEO and will give valuable insights into the origin and evolution
processes
that govern the NEO population. In particular, ISHTAR will
address key
issues related to the threat NEOs pose to Earth:
It will help assess the impact hazard, by providing the first
data on the
internal structure of stony NEOs, helping to predict the
likelihood of NEO
fragmentation on entering the atmosphere and to solve the debate
between
'rubble pile' and 'solid rock' models of NEOs.
It will give us knowledge of the fractures and voids inside the
NEO and will
provide the basis for devising mitigation techniques, by helping
to
discriminate between destructive and deflective strategies.
It will greatly advance our understanding of the origin and
evolution of
NEOs, by giving us vital clues about the formation of stony NEOs
and their
parent bodies, the age and the collisional history of NEOs.
Why it is important to know the internal structure of NEOs
The internal structure is a key topic in estimating the actual
damage that a
collision would cause on our planet, as well as achieving the
final goal of
developing efficient deflection strategies. Many different
scenarios have
been envisaged for changing the trajectory of an asteroid en
route to
collision with the Earth. Break-up events induced by nuclear
explosions or
hypervelocity impacts must be handled carefully since the
fragmentation in
space of a large body could result only in increasing the number
of
impactors. Moreover, depending where you hit (a fracture or weak
spot, for
example) the result of the impact could be completely different.
Gently "pushing" an asteroid away from its collision
trajectory by means of
low-thrust, high specific impulse engines placed on its surface
or by
inducing jet stream activity could represent a valid alternative
when having
at disposal a sufficiently long warning time. Whatever the
scenario, knowing
not only the chemical and mineralogical composition of an
asteroid but its
internal structure is essential for a reliable estimate of the
success of a
mitigation strategy. In this respect, the ISHTAR mission will
provide a
unique contribution to the mitigation and impact hazard
assessment issues,
while also addressing the NEO characterization side of the
Spaceguard
project.
Radar Tomography
Tomography is an imaging technique that enables construction of a
three
dimensional (3D) map of the interior structure of a body such as
a NEO. In
this case, the imaging technique uses electromagnetic radiation
in the radio
spectrum. The deep imaging is possible because low-frequency
radar has the
capability of penetrating below ground. The radio waves penetrate
the rocks
of the asteroid until they are reflected back by a change in
material
composition, density or electrical properties. By collecting
these reflected
echoes it is possible to draw a map of the interior, including
the presence
of voids, fractures, metal, ice, etc. The extent to which such a
3D profile
can be achieved depends on the absorption characteristics of the
body and
the wavelength of the radiation being used. Eventually, a 3D map
of the
asteroid interior can be reconstructed.
The key science goal addressed by radar tomography is the
understanding of
the internal physical structure of the asteroid, with particular
objectives
of discriminating between a solid interior and a conglomeration
of smaller
bodies ("rubble pile"), detect the presence of fracture
lines and voids
within the asteroid, investigate the possibility of
differentiation and
metamorphic effects. In this context, high spatial resolution is
a priority,
as only at high resolution do the details of the internal
structure become
apparent. At the same time, the radar needs to achieve large
penetration
depths, so that the deep structure can be mapped.
Paolo D'Arrigo
==============
(12) REMOTE OBSERVATIONS OF NEOs FROM SPACE
>From Tumbling Stone, 25 July 2002
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/eng/cellino.htm
by Alberto Cellino - Copyright Tumbling Stone 2002
Space activities can provide in the near future some essential
breakthrough
in the field of NEO investigations. ESA has correctly identified
three main
options, including rendezvous missions for in situ exploration,
orbiting
remote-sensing observatories (see dict.: rendez-vous and
remote-sensing),
and space-based systems for studies of the interactions of NEOs
and the
Earth atmosphere and soil. All of the above options can provide
answers to
some of the most important open questions concerning the
inventory and
physical characterization of NEOs. In this way, a number of
theoretical
results concerning the origin and evolution of these bodies can
be derived,
while at the same time producing a much better and new
understanding of the
NEO impact hazard, and of the most suitable mitigation techniques
to be
developed.
Ideally, all the above-mentioned mission concepts should be
developed, since
they can potentially fill a number of very different gaps in our
current
knowledge of the NEO population and impact hazard.
In this proposal, we have focused on the option concerning the
development
of a dedicated space-based NEO observatory. This kind of mission
would be an
ideal complement to ongoing ground-based activities, and should
be aimed at
obtaining some critical information that is very hardly and not
efficiently
obtainable using current facilities from the ground. This
includes an
extensive survey of the known NEOs in order to obtainin in a
short time a
satisfactory knowledge of some critical physical parameters like
size,
albedo, likely surface composition. At the same time, a dedicated
satellite
is expected to be an unvaluable tool for discovering those
particular NEOs
having orbits mostly or completely interior to the Earth's orbit,
which can
be extremely difficult to observe from the ground. This kind of
concept is
not new, and it has been already developed in a number of ESA
documents,
including the SISYPHOS report and the Spaceguard-1 proposal.
However, here
we want to go well beyond the above studies. In particular, we
want to
assess the real feasibility of previously proposed projects and
mission
concepts, and to explore fully new options in all respects
(including the
scientific payload, the whole spacecraft design, the possible
orbital
options, and the possible links with other independent missions).
An orbital observatory is aimed at obtaining information on some
general
characteristics of the NEO population as a whole, and seems to be
particularly urgent, given the increasing gap existing between
the current
discovery rate of NEOs and the overall need of physically
characterizing
these objects, also in order to derive the inventory and size
distribution
of the whole population. This is an essential piece of
information for
assessing the real impact hazard, and a necessary step to better
understanding "the enemy", in order to develop
reasonable mitigation
strategies. Of course, this kind of mission would also be an
ideal
complement of an independent rendezvous mission devoted to obtain
detailed
physical and geologic parameters of some individual object. We
should be
aware that the NEO population is numerous and heterogeneous, and,
roughly
speaking, we are still in a stage in which information and data
on the
individual trees and the whole forest are both, critically
needed.
Alberto Cellino - Oss. Astronomico di Torino
=============
(13) THE EUNEOS PROJECT: LOOKING FOR NEOs FROM SPACE
>From Tumbling Stone, 25 July 2002
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/eng/euneos.htm
by A. Morbidelli and V. Martinot - Copyright Tumbling Stone 2002
Click on the image for a zoom The EUNEOS (European NEO Survey)
project is
the natural outcome of a study on the distribution of Near Earth
Objects,
commissioned by ESA to the group of planetary science of
Observatoire de la
Cote d'Azur in Nice (France), and performed jointly with
scientists at the
Southwest Research Institute in Boulder (Colorado) and Lunar
& Planetary
Laboratory in Tucson (Arizona).
The results of this study are available to the public at the
Internet
address http://www.obs-nice.fr/morby/ESA/esa.html.
In essence, this study
concluded that there should be about 850 NEOs with diameter
larger than 1
kilometer, which, on average, strike the Earth twice per million
year. About
50% of these NEOs are currently known. The present discovery rate
is quite
high, but this does not imply that the so-called Spaceguard goal
(90%
completion within 2008) will be easily fulfilled. In fact, not
all NEOs are
equal. Some have orbits with a geometry relative to the Earth
that make them
easy to find, some others play a "hide and seek" game
with our planet and
are extremely difficult to see. As the surveys continue their
work, all the
easy ones are rapidly discovered, and only the difficult ones are
left
behind. As a consequence, the pace at which the observational
completeness
increases slows down with time. A survey simulator, which
reproduces the
observation record of the last few years, predicts that the
Spaceguard goal
will be reached only in about 40 years from now if we continue
with the
current available infrastructure.
The situation is even worse if smaller NEOs are included in the
Spaceguard
goal. According to the report of the UK task force on NEO hazard
(available
at http://www.nearearthobjects.co.uk/
) it would be recommendable to extend
the goal to all the objects that ould deliver upon collision on
Earth an
energy equivalent to 1,000 megaton TNT. This energy threshold
would
correspond to severe regional physical damage, with global
implications on
our world-wide linked social and economic system. According to
our study,
the NEOs capable of producing 1,000 megaton collisions are those
larger than
~280 meters; there should be about 8,000 of such bodies, striking
our planet
on average once every 65,000 years.
Only 20% of these objects are currently known so that there is
still a long
way to go to protect our planet. To achieve 90% completeness on
these
objects within the next 10 years would require the development of
a survey
capable of observing the entire sky down to limiting magnitude
V=24, several
times per month. For comparison, V=24 is the typical limit on the
brightness
of detectable objects for the surveys devoted to the discovery of
the Kuiper
belt objects, the most distant bodies of the Solar System
situated beyond
the orbit of Pluto. But these surveys explore only a tiny
fraction of the
entire sky, and extending them to cover the full celestial sphere
would
require a huge technological effort. Hopeless? Maybe not.
Our study has revealed that the NEOs are much easier to find if
they are
searched from a point closer to the Sun than the Earth. The
closer to the
Sun, the better. Even the most difficult NEOs become
"easy" from the inner
solar system. Our study therefore concluded that "Space
agencies should
seriously consider the possibility of developing a dedicated
space-based NEO
survey, on-board a spacecraft placed in the inner solar
system". The EUNEOS
project is precisely this: the study of the best possibilities to
find NEOs
from space. Thanks to the partnership between the scientists of
the
Observatoire de la Cote d'Azur, the engeneers of Alcatel space,
the group of
space dynamics of the University of Pisa and the Spaceguard
central node, in
the next 6 months we will find the optimal trade-off between
survey
strategy, telescope size, satellite orbit, observation
wavelength:
ultimately, between performance and cost. A preliminary analysis
shows that
a telescope of a moderate size mounted on board a satellite on an
inner
Solar system orbit should be able to detect 90% of the dangerous
~280m NEOs
in 5 years. If this is confirmed, then the future of NEO searches
may be in
space.
A. Morbidelli - Observatoire de la Cote d'Azur, Nice, France
V. Martinot - Alcatel Space, Toulouse, France
============
(14) THE SIMONE CONCEPT: A FLEET OF SMALL SATELLITES EXPLORING
NEOs
>From Tumbling Stone, 25 July 2002
http://spaceguard.ias.rm.cnr.it/tumblingstone/issues/current/eng/simone.htm
by Ettore Perozzi and Nigel Wells (*) - Copyright Tumbling Stone
2002
It is well known that within the NEO population a variety of
different
characteristics are to be found. Objects coming from the main
asteroidal
belt are represented by all the corresponding spectral types -
thus
indicating the presence of "primitive" bodies as well
as of highly processed
ones (such as the supposed fragments coming from the basaltic
crust of
Vesta). Moreover some objects may have experienced very close
passages to
the Sun with the associated heating and melting of surface
layers. The case
for Wilson-Harrington - discovered as a comet but which later did
not
exhibit any further sign of activity - witnesses the presence of
dormant or
dead cometary nuclei. Finally, space junk -possibly left during
past lunar
missions and escaped into interplanetary space - has also
recently been
observed.
Within this framework, it is clear that performing a mission to a
particular
NEO will provide unique and valuable data on that type, but this
will not
necessarily be transferable to other classes of object. Therefore
a key
topic in NEOs exploration is the requirement to perform in-situ
characterisations of samples of objects from the various types to
establish
a complete picture of the nature of the NEO population. This
wide-ranging
data set will be a critical element also in the mitigation
process, since
the development of deflection strategies strongly depends upon
the physical
characteristics of the potentially hazardous object.
The SIMONE ("Small Intercept Missions to Objects Near
Earth") proposal - a
UK-Italian co-operation led by QinetiQ, in partnership with the
Planetary
and Space Sciences Research Institute of The Open University, SSL
(Science
Systems Limited), Politecnico di Milano and Telespazio -
addresses the issue
of gaining an understanding of the diversity of the NEO
population by
employing a number of relatively small and low cost missions that
individually encounter specific NEOs of interest. Such an
approach requires
the achievement of two major technical goals that in general
characterise
interplanetary missions: a high delta-V budget (needed for
performing
orbital manoeuvres) and a low-cost access to space (launchers are
very
expensive and consequently represent a high share of the total
mission
costs). Therefore the SIMONE proposal foresees the high
performances
guaranteed by the use of solar electric propulsion and the design
of a
spacecraft small enough to be considered as a secondary passenger
(a
so-called "piggyback") for large/medium size launchers.
As an example a 120
kg SIMONE-type spacecraft can fit on the ASAP platform of the
Ariane-5 -
specifically designed to this end - thus exploiting the launching
of a
commercial satellite in orbit around the Earth. Escape to
interplanetary
space is then obtained by using the spacacraft's own propulsion
system.
The selection of NEO candidates on the basis of both their
scientific
interest and their accessibility is also a critical issue. The
distinction
between "rendezvous" and "flyby" mission
profiles is significant. A
"rendezvous", where the spacecraft flies with or orbits
the target NEO,
delivers more scientific value than a flyby simply by virtue of
the time
spent in the vicinity of the object. However the delta-V
requirement for a
rendezvous can be much higher with respect to a flyby when
high-eccentricity
high-inclination target orbits are concerned, as it is often the
case for
NEOs. Therefore, the SIMONE proposal is for rendezvous missions
wherever
this is feasible. When the delta-V requirements turns out
prohibitively
high, an intermediate strategy is proposed: to synchronise the
orbit of the
spacecraft to that of the target object in order to allow
multiple flybys,
thereby maximising the scientific return. This "resonant
flyby " strategy is
similar to that successfully proposed in the early 1970s by
Giuseppe Colombo
during the NASA Mariner mission to Mercury and which allowed the
spacecraft
to flyby the planet three times.
Ettore Perozzi - Telespazio
Nigel Wells - project manager of SIMONE
============================
* LETTERS TO THE MODERATOR *
============================
(15) VIRTUAL RADIO TELESCOPE SEVERAL THOUSAND KM IN DIAMETER
>From Hermann Burchard <burchar@mail.math.okstate.edu]>
Dear Benny,
FYI. By DIE WELT, 23. Juli 2002, see below or at:
http://www.welt.de/daten/2002/07/23/0723astr346121.htx
This refers to "Very Long Baseline Interferometry"
(VLBI). You will recall
that I had advocated this on CCNet 2001 Nov 2 for spotting NEOs
in the
approach phase (to about 1/5 AU). The article says a resolution
of 0.000018
arc seconds has been achieved in test runs. This resolution
far exceeds my wildest expectations for radar: At a distance of
1/5 AU, one
could spot a NEO of diameter of < 10 meters. This is much
better than my
estimates, but the crucial information of the wavelength used is
not
included in DIE WELT.
For reference, some VLBI web pages at JPL (not mentioned in the
article
as
a part of the project) are:
http://us-space-vlbi.jpl.nasa.gov/
http://deepspace.jpl.nasa.gov/dsnscience/vlbi.html
Regards,
Hermann
=================
(16) AND FINALLY: THE LURE, BILL NAPIER'S NEW NOVEL
The Lure is Bill Napier's third novel. Like the other two
(Nemesis and
Revelation) it's a thriller with a science base. It revolves
round a small team of scientists
who unexpectedly detect an ETI signal while looking for dark
matter particles in an
underground cavern in the Tatras mountains in Slovakia, and about
the
response of governments to the signal. The Lure raises real
issues in a
fictional context: what would motivate an extraterrestrial
intelligence to
contact us? Would we be dealing with organic life or clever
machines? What
morality would a clever machine have? If we replied would we be
in danger of
opening a Pandora's box? And so on.
It's published by Headline in hardback and trade paperback, and
will come
out as a paperback in January.
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