PLEASE NOTE:
*
CCNet 73/2002 - 25 June 2002
----------------------------
"Asteroid 2002NM, as it was retrospectively named, is the
sixth
recorded object to have passed closer to Earth than the moon -
and
much the largest so far. The episode highlights the fact that we
are
under constant bombardment from space. It is likely to increase
the
pressure on politicians to fund a more systematic search of the
solar system
for the asteroids and comets - known collectively as
"near-Earth
objects" - that pose a serious threat to life on our
planet."
--Clive Cookson, Financial Times, 22 June 2002
"Questions have been raised as to whether our ability to
detect
asteroids as they hurtle near the Earth is undermined by
underfunding. Some places on Earth, specifically in the Southern
hemisphere, might not have the observation labs and technology
needed to
keep on top of asteroids.... Morrison says that more funding
above
NASA's current $3 million Near- Earth Object survey budget would
be nice,
but that it won't do much more to protect the Earth from
asteroids.
Instead, the extra money would speed up things that don't really
need to
be sped up, he says."
--Lindsey Arent, Tech Live, 24 June 2002
(1) VULCAN IN THE TWILIGHT ZONE
BBC Online News, 24 June 2002
(2) UNDER FIRE FROM COSMIC FALL-OUT
Financial Times, 22 June 2002
(3) OH HAPPY DAY: DR PANGLOSS EXPLAINS WHY THERE IS NO NEED FOR
MORE NEO
SEARCHES OR TELESCOPES
Tech Live, 24 June 2002
(4) JPL TO ASSIST ON CONTOUR MISSION
Ron Baalke <baalke@jpl.nasa.gov>
(5) 2002LY45
Tom Soper <chipnskye@sympatico.ca>
(6) ON IMPACT HAZARD AND PLANETARY DEFENSE
Drake A. Mitchell <planetarydefence@netscape.net>
(7) AND FINALLY: THINKING ROBOT ESCAPE ATTEMPT THWARTED
Ananova, 20 June 2002
============
(1) VULCAN IN THE TWILIGHT ZONE
>From the BBC Online News, 24 June 2002
http://news.bbc.co.uk/hi/english/sci/tech/newsid_2063000/2063200.stm
By Dr David Whitehouse
BBC News Online science editor
Two US astronomers have been looking for a suspected belt of
asteroids close
to the Sun by making observations from the back seat of an F-18
jet.
Dan Durda and Alan Stern, from the Southwest Research Institute
(SwRI) in
Boulder, Colorado, are looking for the Vulcanoids, a ring of
debris lying
between Mercury and our star.
First postulated over a century ago, the Vulcanoids are thought
to range in
size from one to 25 kilometres. Finding them would change our
understanding
of the innermost region of our Solar System.
If they do exist, it is possible they could still contain
fragments of the
earliest materials that formed next to our star when it was
newborn.
"Most comprehensive search"
Durda and Stern are flying at a height of 15 kilometres (49,000
feet) to get
the observing conditions that will best enable them to prove the
belt's
existence.
There is a short period of opportunity to catch the space rocks
Some theories suggest that a small number of kilometre-sized and
larger
Vulcanoids could have survived in the inner Solar System, inside
the orbit
of the planet Mercury, until now.
"Our Vulcanoids search programme, conducted from an altitude
of 49,000 feet
over the Mojave Desert, gave us a view of the twilight sky near
the Sun that
is far darker and clearer than can be obtained from the
ground," says Dr
Durda.
Shuttle camera
"This is the most comprehensive, constraining search yet
conducted for these
objects," adds Dr Stern, director of the SwRI Space Studies
Department.
The camera was designed with the shuttle in mind
Astronomers have conducted ground-based searches for the
Vulcanoids before,
during total solar eclipses, and during the twilight period after
sunset
just before the Vulcanoids themselves would set.
But to date, the asteroids have not been seen. Observations have
only placed
upper limits on how many might exist.
The camera used in the latest search was originally conceived for
the space
shuttle. It is trained on the region of space close to the Sun
after the
star has dipped below the Earth's horizon. The camera grabs
twilight images
at a rate of 60 frames a second.
The researchers are currently analysing their data. They hope to
know if the
Vulcanoids exist in a month or two.
Copyright 2002, BBC
=============
(2) UNDER FIRE FROM COSMIC FALL-OUT
>From Financial Times, 22 June 2002
http://news.ft.com/home/uk/
THE ASTEROID THAT NARROWLY MISSED THE EARTH HIGHLIGHTS A
LITTLE-KNOWN THREAT
TO HUMAN EXISTENCE, SAYS CLIVE COOKSON
Earth had a narrow escape last week. A gigantic rock the size of
a football
pitch whizzed past our planet at a distance of just 120,000km -
an
astronomical hair's breadth.
If the asteroid had hit a populated region, there would have been
mass
casualties and destruction as it exploded in the atmosphere with
the force
of a 10-megaton atomic bomb. A rock about half its size flattened
2,000 sq
km of forest in the Tunguska region of Siberia in 1908.
There was no advance warning that an asteroid was coming our way.
Indeed
astronomers knew nothing until early this week, three days after
the fly-by,
when the Linear Laboratory Near Earth Asteroid Search (Linear)
project in
New Mexico spotted it as a faint object racing away from Earth at
10km per
second.
Asteroid 2002NM, as it was retrospectively named, is the sixth
recorded
object to have passed closer to Earth than the moon - and much
the largest
so far.
The episode highlights the fact that we are under constant
bombardment from
space. It is likely to increase the pressure on politicians to
fund a more
systematic search of the solar system for the asteroids and
comets - known
collectively as "near-Earth objects" - that pose a
serious threat to life on
our planet.
Until recently most people would have dismissed such fears as
science
fiction or the stuff of Hollywood horror films. But research over
the past
decade has shown that space debris played a key role in
terrestrial
evolution.
First, scientists proved beyond reasonable doubt that the
dinosaurs were
wiped out 65m years ago by a monster asteroid 10km wide. Then
they linked
other mass extinctions, such as the previously unexplained Great
Dying that
wiped out 90 per cent of living species 250m years ago, to cosmic
impacts.
Estimates based on the pattern of craters on the moon suggest
that an
asteroid or comet more than 5km in diameter hits Earth about once
every 10m
years. Its deadliest effect is not the explosion - though this
would be
equivalent to a million 10-megaton bombs - but the pollution
thrown into the
atmosphere from the impact crater. Billions of tons of dust,
sulphur and
carbon dioxide would change the climate profoundly.
In one sense, we owe our existence to such impacts, which
smoothed the
evolutionary path to mammals and eventually humans by eliminating
competing
groups of animals. But now that we are here, we do not want to be
removed in
turn by the next big rock to hit Earth.
Although the probability of an impact big enough to kill all 6bn
people on
Earth is tiny, a smaller impact could still have a devastating
effect on
modern civilisation. The latest estimates show that objects 1km
in diameter
- big enough to kill hundreds of millions of people - hit once
every 100,000
years.
Many people became aware of the risk in 1994 when telescopes
recorded the
spectacular collision between Comet Shoemaker-Levy and our sister
planet
Jupiter. At the same time two US scientists, Clark Chapman and
David
Morrison, came up with a striking hazard assessment: an average
American is
as likely to die as a result of a collision with an asteroid or
comet as he
or she is to die in an aircraft crash. In each case the lifetime
probability
is about one in 20,000.
Disaster films such as Deep Impact have also raised popular
consciousness
about the issue. Even so, politicians still find it hard to
appreciate the
real cosmic hazard because there has been no fatal impact during
recorded
history, says Duncan Steel, an expert on near-Earth objects at
Salford
university.
If they did realise the size of the threat, governments would
commit more
funds to doing something about it, Mr Steel says. It would have a
better
cost-benefit analysis than any other public spending project.
Several observatories around the world have been mapping
near-Earth objects
for several years, so as to identify ones that might hit us.
Astronomers
believe they have found about half of the 1,100 or so objects
that are
larger than 1km diameter and potentially cross Earth's orbit.
None poses a
significant threat over the next century.
A more systematic international search called Spaceguard, led by
the US, is
under way. It is well beyond the capability of today's telescopes
to find
all potentially threatening objects but the next generation of
observatories
will be able to do better.
One candidate for finding near-Earth objects is Vista, a 4-metre
telescope
that will be built over the next four years in the Chilean Andes
by a
British university consortium at a cost of more than Pounds 25m.
Jim Emerson
of Queen Mary, University of London, the Vista project leader,
says further
funding would be needed to adapt the telescope so that it could
search
usefully for asteroids in addition to its other work. A more
powerful but
more distant possibility is the 6-to-8-metre Large-aperture
Synoptic Survey
Telescope being planned in the US. Its promoters say it could
identify every
object down to 300 metres in diameter.
What would happen if astronomers found a large asteroid heading
for Earth?
The best way to head it off would be through a nuclear explosion,
says Mr
Steele, though the planning would have to be meticulous to make
sure that
the blast deflected it to a safe path, rather than breaking it
into several
rocks all heading for Earth.
A gentler alternative, given several decades' warning, would be
to deflect
the asteroid by altering its surface - in effect painting it
black or white
- to change the amount of sunlight it reflects.
But if we had a few days' warning only, we could do nothing but
panic or
pray. "Then it might be better not to know," says Prof
Emerson. "If I'm
going to have a heart attack next week, I'd rather not be warned
about it."
Copyright © 2002: Financial Times Group
=============
(3) OH HAPPY DAY: DR PANGLOSS EXPLAINS WHY THERE IS NO NEED FOR
MORE NEO
SEARCHES OR TELESCOPES
>From Tech Live, 24 June 2002
http://www.techtv.com/news/scitech/story/0,24195,3389434,00.html
Asteroid Hunting Challenge: Why scientists missed the most recent
cosmic
close call.
By Lindsey Arent, Tech Live
June 24, 2002
An asteroid hurtles through the solar system, on a collision
course with
Earth, only to be deflected from its deadly orbit just in the
nick of time.
It's the stuff of movies such as "Deep Impact" and
"Armageddon." But as
"Tech Live" reports tonight, truth may be more
frightening than fiction.
"The Earth orbits the sun within a small asteroid belt.
We're part of a
cosmic shooting gallery and we know the Earth has been hit over
time many,
many, times," NASA scientist and asteroid-watcher David
Morrison said. "If
we could see all the craters that've been made on the Earth, it
would be as
many craters as there are on the moon."
Case in point: An asteroid the size of a football field passed
extremely
close to Earth just last week, missing us by a mere 75,000 miles.
That's one
of the closest cosmic collisions ever recorded.
Blindsided
Despite the close call (the distance was about one-third the
distance to the
moon) the asteroid went undetected by astronomers until days
later. How
could we have missed such a close call?
In many cases, asteroids are fairly small objects, and if they
measure less
than a mile in diameter, they can be faint and tough to detect
unless
they're close to the Earth, Dr. Don Yeomans of NASA's Near-Earth
Object
Program says. Many asteroids also come from the direction of the
sun and are
only visible in the nighttime sky.
"Doesn't really matter," Morrison said. "There are
no extra points for
getting it on the way in. We just want to find them, catalog
them, project
their orbit, and make sure they're not a threat to us."
Is sooner better?
Questions have been raised as to whether our ability to detect
asteroids as
they hurtle near the Earth is undermined by underfunding. Some
places on
Earth, specifically in the Southern hemisphere, might not have
the
observation labs and technology needed to keep on top of
asteroids.
In fact, Congress has mandated that NASA hunt down and track 90
percent of
near-Earth objects with a diameter of a mile or more by 2008.
Morrison says that more funding above NASA's current $3 million
Near-Earth
Object survey budget would be nice, but that it won't do much
more to
protect the Earth from asteroids. Instead, the extra money would
speed up
things that don't really need to be sped up, he says.
"If we had more telescopes, we could accomplish the survey
faster, or we
could go to fainter objects. If we had telescopes in the Southern
hemisphere, that would be a special advantage," he said.
"But it's just a
matter of speeding it up. We'll get there even with the
telescopes we have."
The same goes for the issue of high-concept technologies, such as
putting a
telescope on the moon or in orbit around Mercury. These are great
ideas, but
some critics have asked, isn't the money better spent on homeland
defense or
on other major threats?
"The real question," Morrison said, "is how
important is this hazard vs.
others?"
Copyright © 2002 TechTV Inc. All rights reserved.
================
(4) JPL TO ASSIST ON CONTOUR MISSION
>From Ron Baalke <baalke@jpl.nasa.gov>
JPL To Assist On Comet Mission
JPL Universe
June 21, 2002
Contour prepares for July 1 launch
Set to visit and study at least two comets, NASA's Comet Nucleus
Tour
(Contour) should provide the first detailed look at the
differences between
these primitive building blocks of the solar system, and answer
questions
about how comets act and evolve. The mission is being prepared
for a July 1
launch from Kennedy Space Center.
JPL will provide navigation and Deep Space Network support for
the mission,
and JPL astronomer Dr. Don Yeomans, manager of NASA's Near Earth
Objects
Program Office, is a Contour science team
co-investigator.
Contour is scheduled to lift off on a three-stage Boeing Delta II
expendable
launch vehicle during a 25-day launch window that opens July 1 at
2:56 a.m.
Eastern time. The spacecraft will orbit Earth until Aug. 15, when
it should
fire its main engine and enter a comet-chasing orbit around the
sun.
Contour's flexible four-year mission plan includes encounters
with comets
Encke, Nov. 12, 2003, and Schwassmann-Wachmann 3, June 19, 2006.
Contour
will examine each comet's "heart," or nucleus, which
scientists believe is a
chunk of ice and rock, often just a few kilometers across and
hidden from
Earth-based telescopes beneath a dusty atmosphere and long tail.
"The Contour mission will be NASA's second mission dedicated
solely to
exploring these largely unknown members of our solar
system," said Dr.
Colleen Hartman, director of the Solar System Exploration
Division at NASA
Headquarters in Washington. "Contour joins our other
operating mission,
Stardust, which is on its way to bring a sample of a comet back
to Earth,
and Deep Impact will launch next year. These missions all help us
find
answers to the fundamental questions of how our planet may have
formed and
evolved, and how life may have begun on Earth and perhaps
elsewhere in the
Universe."
Comets are "the remnants of the outer solar system formation
process,"
Yeomans said in a prelaunch briefing. The instruments on Contour,
he added,
will determine the chemical composition of the comet - helping in
turn to
determine whether a comet might have brought much of the Earth's
oceans and
its atmosphere, as well as carbon-based molecules, to the Earth's
surface.
Yeomans said the "genius" of the Contour mission design
is that "we're not
chasing comets around the solar system; we're using Earth
swingbys to allow
them to come to us." The encounters are taking place very
close to Earth
(less than 50 million kilometers or 31 million miles), which, he
said,
"makes communications easy, but it also allows professional,
ground-based
astronomers, as well as amateur astronomers and the public, to
participate
in a very meaningful way." The comets will be bright enough
to be seen with
binoculars about the same time as Contour is looking at the
comet's nucleus,
he said.
Members of the JPL navigation team include Tony Taylor, Bobby
Williams,
George Lewis, Cliff Helfrich, Eric Carranza, Don Han, Ramachand
Bhat and
Jamin Greenbaum.
The eight-sided, solar-powered craft will fly as close as 100
kilometers (62
miles) to each nucleus, at top speeds that could cover the 56
kilometers
between Washington and Baltimore in two seconds. A five-layer
dust shield of
heavey Nextel and Kevlar fabric protects the compact probe from
the comet
dust and debris.
"Comets are the solar system's smallest bodies, but among
its biggest
mysteries," said Dr. Joseph Veverka, Contour's principal
investigator from
Cornell University, Ithaca, N.Y. "We believe they hold the
most primitive
materials in the solar system and that they played a role in
shaping some of
the planets, but we really have more ideas about comets than
facts. Contour
will change that by coming closer to a comet nucleus than any
spacecraft
ever has before and gathering detailed, comparative data on these
dynamic
objects."
Contour's four scientific instruments will take pictures and
measure the
chemical makeup of the nuclei while analyzing the surrounding
gases and
dust. Its main camera, the Contour Remote Imager/Spectrograph,
will snap
high-resolution digital images showing car-sized rocks and other
features on
the nucleus as small as 4 meters (about 13 feet) across. The
camera will
also search for chemical "fingerprints" on the surface,
which would provide
the first hard evidence of comet nuclei composition.
Encke has been seen from Earth more than any other comet; it's an
"old" body
that gives off relatively little gas and dust but remains more
active than
scientists expect for a comet that has passed close to the sun
thousands of
times. Schwassmann-Wachmann 3, on the other hand, was discovered
just 70
years ago and recently split into several pieces, intriguing
scientists with
hopes that Contour might see fresh, unaltered surfaces and
materials from
inside the comet.
Contour is the sixth mission in NASA's Discovery Program of lower
lost,
scientifically focused exploration projects. Johns Hopkins
University's
Applied Physics Laboratory manages the mission, and also built
the
spacecraft and its two cameras. NASA's Goddard Space Flight
Center provided
Contour's neutral gas/ion mass spectrometer and von Hoerner &
Sulger, GmbH,
Schwetzingen, Germany, built the dust analyzer.
For more information, visit http://www.contour2002.org.
============================
* LETTERS TO THE MODERATOR *
============================
(5) 2002LY45
>From Tom Soper <chipnskye@sympatico.ca>
Good afternoon Benny:
I am very pleased to see that, at this writing, the community has
been able
to "get on it" and has made 156 observations of
2002LY45. You may recall
that, last year, I was a minor player in the uproar over the
manner in which
information regarding 2001PM9 was disseminated. That is,
the alert I sent
out resulted in debate about whether NeoDys ought to be
publishing
preliminary information on a public web-site, and exactly how
preliminary
information was being distributed so as to ensure the maximum
opportunity to
observe potentially hazardous bodies?
I attempted at that time to create pressure on the scientific and
political
apparatus, by way of the media. For my troubles (and
perhaps because of my
somewhat "colourful" (I say accurate) descriptions of
the effects of an
impact by an Asteroid of this size) I was characterized as all
things from
"Chicken Little" to "Crusader".
As it turned out, there were enough observations made to
eliminate 2001PM9
as a threat. So, in a way, I ended up with egg on my face
on that one.
But, I am tempted to think, maybe not.
Since that time, NASA has launched SENTRY and has its own Impact
Risks page
on the Internet. NeoDys has continued its fine work, and
did not cave in to
the pressure to bury preliminary results. And given the
fact that your
colleagues have amassed nearly 160 Observations on 2002LY45 (an
object of
even greater destructive potential given its size and relative
velocity) I
have to assume that improvements have been made in the way the
word gets out
to those able to make the necessary observations. By my
calculation, the
overall average number of observations made on the other 37
Asteroids
currently identified as potential impactors is a mere 26!
So this is a
mammoth improvement, and everybody involved deserves
congratulations.
Interesting too, is the fact that CLOMON2 (based on 156) and
SENTRY (based
on 150) at this point are producing almost identical solutions
for 2002LY45,
as to date and time of possible impacts.
A Palermo Scale rating of -.47 is by far the highest I have ever
seen. I do
remain stymied by the lack of media attention "real
potential impacts" get,
while "real actual misses" get front page headlines
(like 2002MN). Well, I
guess the only kind of bad publicity is no publicity at all - and
we need
all we can get to get the dollars and facilities needed to
accelerate the
pace of this work.
All the best,
Tom Soper
================
(6) ON IMPACT HAZARD AND PLANETARY DEFENSE
>From Drake A. Mitchell <planetarydefence@netscape.net>
Dear Benny,
Please forgive me for pulling a Kruschev and pounding a shoe on
the podium,
but if Buckminster Fuller's decades-old cautionary thesis is to
be heeded at
all [1], then we have no time to spare. None. Whatsoever. Period.
The alarming slippage of time becomes obvious to anyone engaged
in serious
work or otherwise aware of its large consequences. In our case,
with the
solstice now past and Summer in full swing, we are barely
two months away
from the first of at least two possibly supreme conferences in
our NEO
community. I am sure I am not the only one whose backlog of work
continues
to grow at least geometrically. Therefore I can no longer in good
conscience
remain silent, without at least offering a summary of issues and
an
opportunity for any "trajectory correction maneuovres"
that may be
appropriate.
The Excalibur-II (X2) proposal [2] seems to be alive and gaining
momentum.
At least one practical constraint concerns telemetry throughput,
as the
existing DSN infrastructure is already expecting an imminent
signals
"traffic jam"; new antennae and laser methods promise
tenuous relief [3].
Also encouraging is the increasing support for small satellite
technology
and the cataloging of smaller NEOs [4]. Recent discussion on the
SSI List
has also proposed one-shot "coffee-can" sized
spacecraft that could approach
the many nearby NEOs for close-up fly-by imaging and/or small
impact events
that could yield plumes amenable to ground-based spectrometry.
Lingering doubts remain, however, which is hard to fathom when
the new
Department of Homeland Security would have an initial annual
budget more
than twice NASA's at ~$38B without even FOIA and Whistleblower
protections,
and given that Planetary Defense would benefit from methods
alternate to
nuclear detonation: as has been known for years, we can turn the
enemy
against itself by using the much more available smaller NEOs
against the
much more lethal ones. Additionally, X2 could conceivably be
immune to all
seven of the blind spots that afflict ground-based optical
telescopes; the
comet-detection bonus is also drawing substantial support. To his
credit,
Kieffer-Olsen also points out the further bonus possibility of
sampling the
coplanar Mars-toroidal region, albeit with an NMO/NEO detection
size
threshold ratio >>1; implications are discussed below.
An area that apparently still has gaping holes requiring
considerable
further research concerns the complete distribution of collision
probabilities across the entire PHA population, i.e. which
subgroups have
greatest likelihood, e.g. by the plethoric plague of N-body
resonances N=3
to ~6 (various permutations of massive bodies), orbital energy,
low
relative-velocity encounters, gravitational focusing effects,
Lyapunov
indicators, problematic coplanar tangent encounters, fractal
dimensionality
[5] etc. Milani et al highlight the non-Gaussian distributions of
astrometric errors, and the urgency of nonresonant returns and
multiple
returns, as well as the discovery of pathologically large
keyholes for NEOs
on particular "interrupted" resonant returns, in an
overview of linear and
nonlinear analytical methods in the upcoming Asteroids III tome
[6]. True,
George Friedman's BNS theory may offer considerable firepower for
such
analytical challenges, but given that all PHAs and smaller could
be
catalogued in a mere six years, is it really worth risking
further delay? I
think not, and economic analyses agree, even with the consequence
that
ground-based astronomers and "virtual observatories"
[7] would at long last
experience massive budget growth for crucial post-detection NEO
investigations.
There have been requests for clarification concerning the MOID
parameter and
X2; here goes. Collision requires coincidence in both space and
time. The
key spatial parameter and hazard indicator discussed so far is
the MOID:
"This distance, which is known as the Minimum Orbital
Intersection Distance
(MOID), is equivalent to the minimum separation between the
osculating
ellipses, without regard to the location of the objects on their
orbits"[6].
Note that several local minima for MOID are possible with
multiple nodes of
intersection: two, or more, depending on the geometry of the
ellipses. Note
also that there are NEOs with low MOIDs with the Earth and also
at the same
time with other massive bodies [8]; a diagrammatic and analytical
introduction to the MOID is recently available [9].
The additional criteria for a collision is that, given a low
enough MOID,
there is also proximity in time: the Earth and the NEO must not
only cross
paths, but they must also do so at the same time. Thus NEOs in
"presonances"
never cross paths at the right times for collision while they are
in such
resonances, and NEOs caught in the permanent dynamic web of
hazardous
resonances cross paths with the Earth in complicated time
intervals.
Determining these path-crossing appointments with destiny, and
their
corollary collision probabilities, is highly nontrivial. However,
the simple
starting point for identifying the objects of notoriety is the
MOID, the
path-crossing indicator. Incidentally, helpful analogies can be
made with
space debris that may be potentially hazardous to the ISS,
Shuttle, and many
other assets in Earth orbit, and even with the recent discussion
(Lou Dobbs,
CNN's Moneyline) regarding a better definition for the "war
on terror" by
focusing attention first on the population of
"Islamist" radicals in
general, and then second on the militant Islamist radicals in
particular.
We can define another parameter, which implies a combined
spatiotemporal
proximity, the Minimum Geocentric Distance (MGD; apologies to the
Miller
Brewing Company). Objects with a low quantity of MGD in the
present will
necessarily also have a low MOID, and this may be as good a
reason as any to
drink a fine beer. However, the converse is not generally true:
NEOs with a
low MOID now are the very PHAs that may suddenly, perhaps too
suddenly,
become low enough in MGD to present a hazard. While an exhaustive
analysis
of MGD is beyond our scope and taste here, suffice it to say that
as it
depends on the osculating distance to an NEO, that a) the MGD is
never less
than the MOID, and b) unlike the MOID, the MGD exhibits a much
greater
variability in short periods of time, i.e. units of orbital
periods. (I'm
reluctant to say that more MGD for the PHAs would solve all our
problems,
but driving NEOs under our influence would have prudent
advantages; see
below). A specific distribution of MGD for the PHAs is
illustrated by a
graph I have posted on the web [10].
The data for this graph was computed and processed in a Sunday
afternoon and
a weeknight using an N-body integrator on a Pentium PC with
Windows98. A
simple non-debiased system of 438 known PHAs was integrated for
the period
2001-2007, and the MGDs and toroidal traversals extracted,
allowing
approximate comparative assessments of X2 with geocentric
deployments of
space-based detection platforms. The graph shows the cumulative
percentage
of PHAs that could be detected traversing within increasingly
larger spheres
around the Earth (orbiting with the Earth around the sun). The
graph is in
Log-Log format to highlight the data at lower values.
At the high end, we can see that all the PHAs (and much more)
would be
detected if we could detect every traversal through a ~2.05 AU
radius "Globe
of Danger" about the Earth, which of course grossly and
easily envelops the
much smaller critical volume of the toroidal "Donut of
Danger". At the low
end, at 0.01 AU, about the distance of L1 towards the Sun, less
than 1% of
the PHAs could be detected crossing the corresponding spherical
volume with
this radius. Thus Rather's ARGUS proposal at 1995's LLNL PDW [11]
could
detect among the more interesting ~1%'s of the PHAs, those with
both MGD and
MOID <0.01 AU during this period. However, ARGUS would not by
this
geocentric estimate detect either a) the remaining ~95% of the
~20% of all
PHAs, those with MOID<0.01, that did not happen to have
MGD<0.01 during this
short period, or b) the remaining ~80% of all PHAs with
0.01<MOID<0.05 AU.
These undetected PHAs could unfortunately demonstrate MGD<0.01
and MGD<0.05,
respectively, virtually anytime thereafter. Note that for orbital
forecasting "the close approach threshold distance used for
the Earth is
typically ~0.1-0.2 AU" [5 p.15], which scales by mass in any
of the schemes
of close approaches involving Mercury, Venus, the Moon, Mars,
and/or
Jupiter. Thus, "to lock in maximum warning times" [12]
for the PHAs, it pays
to go after the entire PHA population, especially since this can
be done
within a mere 6 years by observing the entire toroidal volume,
not just the
segment including the Earth.
Similarly for spheres at larger radii. Within 0.05 AU, also the
radius of
the Donut of Danger, less than 10% of the PHAs could be detected
in the same
period. Within 0.23 AU, or a sphere about equal to the entire
volume of the
Donut of Danger, only ~45% could be detected. The median is at
~0.28 AU, or
about the distance of Venus at its closest approach to Earth.
However, the
medians for some subpopulations would be at greater radii: 50% of
PHAs with
upper-medium eccentricity 0.6 < e < 0.8 detectable within
~0.37 AU (230%
greater volume), and 50% of PHAs with orbital periods greater
than 3 years
within 0.44 AU (388% greater volume). At 1 AU, about the distance
of the
Earth's L4 and L5 points, ~88% could be detected. This is finally
high
enough to have an important consequence: it appears that it would
be quite
prudent to consider relocating two older space-based detection
platforms to
L4 and L5, and to supplement this relay capacity with a third at
L3, behind
the Sun. Thus we could have a robust three-pronged attack, using
1) the many
ground-based assets, 2) three large space-based Lagrangian
assets, and 3) a
fleet of much smaller space-based toroidal assets.
"Older" space-based detection platforms that are
candidates for relocation
include the Keyhole-class telescopes [13] and the DSP satellites
[14]. Three
of either class would require modifications, and the former
possibly
multiple Centaur-like upper-stage boosters. Crude estimates using
JSC's AMCM
[15] assuming Block 5, high difficulty, 30,000 lbs/5,000 lbs
payloads, and
single launches in 2003 yield costs of ~$2.30B and ~$712M,
respectively.
Lead times and simulated efficiencies are not the only
challenges; Russian
and other assets should also be considered. Of course these costs
are low
enough that this may already have been done years ago, in which
case this
seems like a fine year for declassification. Furthermore,
basing the
refurbished Hubble at L4 or L5 could have substantial benefits
just for its
existing user community, including several pointing advantages
deriving from
the release from the shackles of 90-min Low Earth Orbits, even if
this bird
no longer "flaps its wings" like it used to. These
costs may seem expensive
compared to historical NEO expenditures, particularly for
ground-based
efforts, but it is also easily demonstrable that we have been
painfully
underspending on the NEO hazard for a decade; one great benefit
of these
early efforts is that cost is now less of an issue than payoff.
Assuming a small satellite covering a segment of the Donut of
Danger 0.1 AU
(2 x 0.05) in width by observing a surrounding sphere with radius
0.07, at
least 126 would be required for overlapping coverage of the
entire toroid
along the Earth's orbit. The one observing the Earth would detect
the lion's
share of PHAs, ~10%, but note that the entire ring of satellite
"buoys"
could slowly rotate within the Earth's orbit without significant
detection
penalty, thereby possibly providing the minimum delta-V
requirements. A
decent cost-estimate might require the use of the Aerospace
Corporation's
SSCM99 [16]. However, if we take NESS as a reasonable upper
limit, and a
per-unit cost near $2.0M, the fleet might cost less than $252M to
build.
What is not yet clear is the minimum size detection threshold; a
reasonable
non-IR limit seems to be ~110m, plenty low enough to justify
immediate
deployment. Pushing the detection limit down further using
infra-red Si:Ga
technology may or may not be immediately cost-effective, in which
case this
capability could be deployed in a second-generation fleet that
also benefits
from a more fully upgraded DSN and relieves the first fleet for
reconnaissance tasking to selected NEOs.
Clearly the satellite fleet seems a much better value. Certainly
X2 still
requires further verification; my graph can be verified by
various groups in
less than a day, and at least one additional simulation involves
the
turnover in the PHA population over the current century. However,
the stakes
are assuring the safety of civilization, and having several
fronts of attack
is the epitome of a robust strategy. Indeed, NEO-enabling the
MESSENGER
mission still seems prudent. Who would like to be guilty of
missing the
detection of a large NEO impactor that just happens to have a bad
date with
Earth within the next 25 years, when this could be prevented in
six? The
stakes are too high, the odds are just not low enough, and the
economics are
on our side.
Several other projects are also making progress. Readers may
recall
January's "dust-up" regarding Pope's paper, which
concerned the sensitivity
of estimates of the long-term NEO threat, and thus annualized
estimates of
economic damage, to the uncertain threshold for catastrophic
global effects.
I've looked into extending John Lewis' simulation to include
global effects,
for such a sensitivity analysis, by starting with a statistical
model of the
geological layer. I found Laske et al's CRUST 2.0 model of the
Earth [17]
with 2x2/1x1 degree 7-layer cells (ice +/- 250m, water, soft/hard
sediments
+/- 1km, upper/middle/lower crusts +/- 5km), which gives a nice
start
towards modeling the impact cratering of 500m+ NEOs. A next step
might be
supplementing this dataset with variations in sedimentary mineral
composition, e.g. sulfur.
The next project concerns an in-depth review of the scientific
literature on
the SL9 impact on Jupiter, a story that seems to continually
offer new
dimensions of amazement. I expect to have a long essay on the
subject
completed mid-Summer. What is important to say about the subject
now is that
the event was an unbelievably miraculous gift; the continuing
stream of data
includes psychological insights, incredible orbital dynamics and
dozens of
impact effects, and the implications are many, but perhaps the
most
strategic is the paramount importance of empirical methods in
science. The
bottom line is that we can benefit hugely from a few more such
non-terrestrial live impact events, as global effects thresholds
have been
an outstanding problem.
This has been the subject of a project I started in February and
expect to
complete before September. The new paradigm I recounted in April
provides
the means: without using nuclear detonation methods, new
astrodynamic
techniques now allow us to empirically investigate well within
our lifetimes
the poorly understood global effects thresholds of NEOs, by
arranging
similar, highly specified events on other planetary bodies. I
have already
identified several dozen candidate NMOs for modeling the orbital
modifications necessary to arrange impacts on Mars, which of
course is
already the focus of substantial and increasing instrumention
infrastructure
and research. I review the many variables regarding the impactor
and
conditions of impact, with the goal of identifying the smallest
set of
customized impacts that would yield the best data for
understanding the
global effects of NEO impacts on Earth. Perhaps the most
promising
propulsion options are nuclear-powered mass-drivers, and plasma
engines (see
below). Such a program would overlap somewhat with
"terraforming", and even
Buzz Aldrin's space tourist agenda - how much would you be
willing to pay to
witness a multi-gigaton impact event on Mars?
It would also be worth considering custom impact events on
Mercury (much
hotter than the Moon, but allowing us to calibrate both sets of
craters),
Venus (with a much thicker, hotter, and windier atmosphere),
Jupiter (to
calibrate SL9), Io (to study volcanic and tectonic effects),
Europa (a small
tsunami laboratory would also reveal ice thickness and enable
subsurface
investigations), Saturn (to investigate the Great White Spots),
and Titan
(another atmosphere, and possibly another ocean, as we will soon
find out).
A related story concerns "death by comet cyanide",
which is an issue on Mars
or Venus, as at Jupiter, but not a first-order effect on
oxygen-rich Earth.
John Lewis raises the concern that substantial data reduction
challenges
would arise, but I call this a happy problem. I expect more
difficult
challenges in the debates arena, and so have prepared
first-strike rebuttals
for major political constituencies that could be sharper still;
fortunately
it also appears that a further quantification weighting the
Titanic
comparative risk model is forthcoming. "Let the year-long
Octoberfests
begin!"
By the way, another outstanding problem in the field concerns
possible
periodicities in the NEO flux, and it occured to me that someone
should
investigate the possibility that the growing field of Stochastic
Resonance
may have applications to our complex dynamical system of NEOs:
http://www.ima.umn.edu/geoscience/abstracts/10-29abs.html
Furthermore, here are two important references that seem to have
been missed
on CCNet. Some notes are finally available concerning Project
B612, the
"Deflecting Asteroids" workshop at NASA/Johnson,
20Oct01:
http://www.sns.ias.edu/~piet/act/geo/deflection/houston.html
Also, ~70 pages of abstracts are available from 09Feb02's Rubey
Colloquium
at UCLA: http://www.ess.ucla.edu/rubey/abstract.pdf
Incidentally, Texas Tech's Sankar Chatterjee was kind enough to
provide an
update on the suspected Shiva astrobleme. This could be the topic
of yet
another essay, as more positive evidence has accumulated, but he
is
scheduled to present a major paper on the subject in Cape Town in
July.
Separately, it also appears that an important new edition of a
major text on
planetary science will be coming out this year.
There seems to be a concensus that September's conference in
metro
Washington, DC will be the most important NEO meeting yet held on
our
planet: http://www.noao.edu/meetings/mitigation/index2.html
I propose that optimizing the effects of this conference should
be of
paramount interest to all of us, and submit that an immediate
dialogue on
this issue should be a top priority for all CCNet participants.
As the U.S.
ship of state seems to be pulling off flying jibes while shooting
up a new
mast built from the other rigging under full sail, and even the
FBI has
admitted that it needs to import intelligence, is it really too
much for us
to expect NASA to consider a threat-focused overhaul? It is high
time for a
totally new Federal Advisory Committee Act (FACA) body to take up
this
interagency issue; a $20M appropriation over three years would
allow our
field to raise needed matching funds and to fully prepare for the
long haul,
as it has long deserved.
Finally, even more disturbing to me than this year's episode in
Australia,
was a Crossfire show on CNN [18]where a prominent spokesman for
American
physicists was unable to say a single positive thing about the
Space
Station! Bob Park has written a long series of insightful
commentaries over
the years ("What's New" [19] ), but if he and his many
colleagues are unable
to come up with important objectives for the ISS, then the nicest
thing I
can say is that I suggest he try querying groups like ProSpace
and CCNet. On
a side note, as the Cosmonauts have recently expressed interest
in Station
visits by Cindy Crawfords, it seems that I may have had a typo in
April: did
I actually mean "babe-sitting"?
I liked your recent MSNBC quote pointing out the paradoxical
nature of our
universe - "...we are living in an extremely dangerous
universe - which is
at the same time true and not true." However, humanity can
only enjoy the
clear benefits of this paradox if we manage to continue to
survive its
obscure hazards. There is a hexapocalypse of large NEOs needing
to be
discovered; yesterday is not too soon. I salute Moby's new
anthem, "No one
can stop us now, 'cause we are all made of stars."
Regards,
DAM
[1] http://abob.libs.uga.edu/bobk/ccc/cc030702.html
[2] http://abob.libs.uga.edu/bobk/ccc/ce041802.html
[3] http://www.space.com./businesstechnology/technology/dsn_future_020529-1.html
[4] http://abob.libs.uga.edu/bobk/ccc/cc060702.html
(#1)
[5] http://adams.dm.unipi.it/~milani/preprints/opikret.pdf
[6] http://adams.dm.unipi.it/~milani/preprints/asteroids3.pdf
[7] http://www.space.com/scienceastronomy/astronomy/virtual_astronomy_011120-1.html
[8] http://www.lowell.edu/users/elgb/moid.html
[9] http://math.ubbcluj.ro/~sberinde/thesis/abstract.pdf
[10] http://geocities.com/redbaseone/graphs.html
[11] http://www.llnl.gov/planetary/pdfs/Detection/03-Rather.pdf
[12] http://www.niac.usra.edu/files/studies/abstract/75Gold.html
[13] http://www.fas.org/spp/military/program/imint/andronov.htm
[14] http://www.aero.org/publications/crosslink/winter2000/01.html
[15] http://www.jsc.nasa.gov/bu2/AMCM.html
[16] http://www.aero.org/software/sscm/
[17] http://mahi.ucsd.edu/Gabi/rem.dir/crust/crust2.html
[18] http://www.cnn.com/2002/ALLPOLITICS/04/26/cf.crossfire.space/
[19] http://www.aps.org/WN/
=============
(7) AND FINALLY: THINKING ROBOT ESCAPE ATTEMPT THWARTED
>From Ananova, 20 June 2002
http://www.ananova.com/news/story/sm_611290.html?menu=news.scienceanddiscovery.amazingscience
Scientists running experiments with "living robots"
which think for
themselves say they have been amazed to find one escaping from
the centre
where it "lives".
The unit, called Gaak, is one of 12 which are taking part in a
"survival of
the fittest" test at the Magna science centre in Rotherham,
South Yorkshire,
which has been running since March.
Gaak made its bid for freedom after it had been taken out of the
arena where
hundreds of visitors watch the machines learning as they do daily
battle for
minor repairs.
Professor Noel Sharkey said he turned his back on the drone and
returned 15
minutes later to find it had forced its way out of the small
make-shift
paddock it was being kept in.
He later found it had travelled down an access slope, through the
front door
of the centre and was eventually discovered at the main entrance
to the car
park when a visitor nearly flattened it with his car.
Prof Sharkey said: "Since the experiment went live in March
they have all
learned a significant amount and are becoming more intelligent by
the day
but the fact that it had ability to navigate itself out of the
building and
along the concrete floor to the gates has surprised us all."
And he added: "But there's no need to worry, as although
they can escape
they are perfectly harmless and won't be taking over just
yet."
Copyright 2002, Ananova
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