[FMO] Fwd: NEO News (03/09/07) Planetary Defense Conference Pt 2
- From: Marco Langbroek <marco.langbroek@xxxxxxxxxx>
- To: FMO lijst <fmo@xxxxxxxxxxxxx>
- Date: Sat, 10 Mar 2007 10:18:25 +0100
-------- Original Message --------
Subject: ***SPAM*** NEO News (03/09/07) Planetary Defense Conference Pt 2
Date: Fri, 9 Mar 2007 16:20:41 -0800
From: David Morrison <dmorrison@xxxxxxxxxxxx>
To: David Morrison <dmorrison@xxxxxxxxxxxx>
NEO News (03/09/07) Planetary Defense Conference Pt 2
Below is a report on the second half of the Planetary Defense Conference
held this week in Washington DC. These sessions dealt with a range of
societal and strategy issues, and in this summary I am reporting on only
a few of the papers. At the end of this edition of NEO News are more
press comments from the meeting.
I am happy to note that the NASA Study Report to Congress, submitted in
response to the mandate to present a program plan to find 90% of NEAs
down to 140m, was submitted late this week. This 27-page report is
titled "Near Earth Object Survey and Deflection Analysis of
Alternatives". We will comment on this report in a later edition of NEO
News.
David Morrison
================================
Impacts and Effects
Several papers were presented on the effects of impacts of various
sizes. These included talks by both Galen Gisler (U Oslo) and Steven
Ward (UC Santa Cruz) on the effects of tsunamis. Both emphasized the
uncertainty that is caused by the fact that the wavelength and frequency
of impact tsunamis is intermediate between that of ordinary storm waves
and seismic tsunamis. Gisler presented detailed computer simulations of
impacts, creating extremely high waves that also have high turbulent
dissipation. However, his computer runs trace the waves only to 100 km
from the point of impact, so they do not address the important question
of how far these waves propagate. Ward's presentation noted one new
effect, the build-up of water when a series of short-wavelength waves
hit the shore. If the waves are coming in once every few minutes, they
do not have time to retreat before the next in the series hits, so that
the run-up and run-in of the impact tsunamis is greater than had been
assumed previously.
Mark Boslough (Sandia) discussed interesting simulations of atmospheric
explosions such as Tunguska. Noting that the fireball from a meteor
explosion has considerably downward momentum (unlike the classic
mushroom cloud from a nuclear explosion), he concludes that the Tunguska
impactor exploded higher and was smaller (energy of order 5 megatons)
than usually inferred.
Preparing the Public
Richard Davies (Western Disaster Center) challenged us to consider the
political ramifications if a small (few megaton) impact took place
without warning. Comparing with the government investigation following
Katrina, he noted that difficult questions would be raised concerning
lack of preparation. This scenario highlights the absence of
communication today between the NEO community and the Department of
Homeland Defense, let alone the many state and local disaster agencies.
Several other speakers made similar points -- we are not connecting with
the communities that exist to deal with natural hazards. They have an
infrastructure that could include planning for a Tunguska-class impact,
but they don't know we exist. We have thought about response to an
impact warning, but not much to the consequences of an impact without
warning, which remains the most likely (at least until completion of the
next generation survey).
Policy and Political Issues
Several distinguished speakers from outside the normal NEO community
spoke to the conference about these questions. One major issue was the
role of international activities. Rusty Schweickart (Association of
Space Explorers) made a strong case that this is a global problem, and
it is likely that nearly every nation will at some point in the next few
years have to think about its own vulnerability to an impact. Other
speakers agreed that this is a topic that needs to be on the agenda of
the UN and other international agencies, and that decisions to intercept
a threatening NEA must be made internationally. Yet the fact is that
there is very little international contribution today to NEA studies.
Japan and the European Space Agency have scientific missions planned to
NEAs, but the United States is the only country contributing to the
Spaceguard Survey or the Arecibo Radar, two key elements in planetary
protection that are happening now.
Geoff Sommer (Homeland Security Institute) noted that increasing
quantification of the impact risk as a result of NEA surveys might work
to our disadvantage in seeking resources, relative to other societal
risks that are not quantifiable. People are generally more concerned
about unknown risks than those that are well understood (e.g., terrorism
or pandemics rather than auto accidents or malaria).
Chris Chyba (Princeton U.) also addressed the impact hazard in the
context of global threats, comparing it to issues such as global
warming, nuclear proliferation, pandemics, and terrorism. He concluded
that dealing with most global issues requires a response involving
several nations, whereas the U.S. alone can mitigate the impact risk. He
noted that the impact risk is static, while most other global threats
are increasing -- which may decrease the motivation to allocate
resources to protecting against impacts. Chyba also emphasized how
strongly most of the international community mistrusts any mitigation
strategy that involves nuclear explosions, and he recommended that we
pursue non-nuclear options to the extent possible. (This opinion is in
contrast to the current NASA study, which gives considerable attention
to nuclear options for asteroid threat mitigation.)
Preparing a White Paper
The final discussions at the meeting dealt with input to an AIAA White
Paper. The strongest consensus concerned the critical importance of
maintaining the Arecibo Planetary Radar; support for Arecibo was
proposed as the first resolution in the White Paper. Other ideas
included expansion of current surveys (taking advantage of the
opportunities to include NEAs within the mission of the Pan-STARRS and
LSST telescopes) and expanding the capability to process these data and
generate NEA orbits and impact predictions. On the question of how to
protect against an identified threat, the opinions seemed to fall toward
using the gravity tractor or the ballistic impact in preference to
nuclear explosives.
All three of these deflection technologies need to be developed,
however, since they have very different capabilities, and we are dealing
here with a huge range of NEA sizes and orbits. One of the complications
is just getting to the asteroid, which is much harder when it chooses
us, as opposed to us choosing it. The gravity tractor must match orbits
(rendezvous) with the target. In contrast, the kinetic impactor does not
need to slow down near the asteroid, but it does have to hit a small
target at high speed. Nuclear charges would normally be used from a
rendezvous spacecraft, but in extreme cases might be deployed like
kinetic impact, with a high-speed intercept. There is no "one size fits
all" solution.
Below are specific comments on these deflection strategies from Rusty
Schweickart, as well as several press responses.
=================
Comments from Rusty Schweickart on asteroid defense strategy:
In the last day of the conference it all came together nicely,
integrating much of what we had heard both re deflection options,
characterization and the anticipated discovery "demographics". My take
on it is that we're now very close to the following:
There will be some cases where impact-threatening NEAs will experience
close gravitational encounters (usually with Earth) prior to impact. In
most of these cases, due to the multiplication effect of the associated
keyhole, the gravity tractor (GT) will be adequate to the job.
If not (e.g. large object and/or "weak" keyhole) then a kinetic impactor
(KI) will certainly be adequate. However, since the keyhole makes the
uncertainty large, a transponder should be sent ahead to both collapse
the line of variations on arrival and also be there for surveying the
detailed results of the kinetic impact. Since a gravity tractor also
has a transponder aboard, the transponder mission itself should be a GT,
which also then has the advantage of not only surveying the final result
of the KI but also "trimming" up the deflection with precision to assure
(the world) that the deflection did not put the NEO into another keyhole.
Finally, when all else is inadequate, the world will have to make the
tough decision of whether to take the chance of a hit or use a nuke.
This should be an extremely small component of the overall threat, and a
diminishing one over time since the major need for a nuke is the
possibility of finding a NEA headed for a near-term impact during the
next 15 years of the survey. After that it's only the small remaining
component of the residual very large NEAs.
The GT is a bit wimpy, but precise and great for when the ball is on the
green. KI is far more capable but more imprecise and should not be
launched without a GT/transponder.
===============
Funds Keeping NASA From Finding Killer Asteroids
Scientists Have The Skill, But Don't Have The Money
Mar 6, 2007
(CBS4) WASHINGTON If there is a hidden killer asteroid or comet out in
space with Earth's name on it, NASA has the technology to find it. What
it doesn't have is the money to pay for the search, so NASA officials
say it likely won't get done.
NASA officials say the space agency is capable of finding nearly all the
asteroids that might pose a devastating hit to Earth, but there isn't
enough money to pay for the task.
The cost to find at least 90 percent of the 20,000 potentially hazardous
asteroids and comets by 2020 would be about $1 billion, or about the
cost of supporting two weeks of the War in Iraq, according to a report
NASA will release later this week. The report was previewed Monday at a
Planetary Defense Conference in Washington.
Earth got a scare in 2004, when initial readings suggested an 885-foot
asteroid called 99942 Apophis seemed to have a chance of hitting Earth
in 2029. But more observations showed that wouldn't happen. Scientists
say there is a 1-in-45,000 chance that it could hit in 2036. They think
it would mostly likely strike the Pacific Ocean, which would cause a
tsunami on the U.S. West Coast the size of the devastating 2004 Indian
Ocean wave.
John Logsdon, space policy director at George Washington University,
said a stepped-up search for such asteroids is needed. "You can't
deflect them if you can't find them," Logsdon said. "And we can't find
things that can cause massive damage."
Congress in 2005 asked NASA to come up with a plan to track most killer
asteroids and propose how to deflect the potentially catastrophic ones.
"We know what to do, we just don't have the money," said Simon "Pete"
Worden, director of NASA's Ames Research Center.
==================
Big blasts or tiny tugs: How to stop an asteroid catastrophe
Collision with Earth is seen as inevitable, but scientists are meeting
to find solution
Alok Jha, science correspondent
The Guardian, March 7, 2007
A huge asteroid hurtles in from outer space to devastate the Earth, an
unstoppable force of nature from which there is no escape. Just such a
catastrophe is thought to have killed off the dinosaurs, and, according
to most experts, it is only a matter of time before a similar fate
befalls the human race.
But perhaps not all hope is lost. Hundreds of scientists, from nuclear
weapons engineers to planetary experts, are gathering in Washington this
week to try to develop a master plan to protect the Earth from such an
asteroid.
The Planetary Defence Conference, organised by the US Aerospace
Corporation, will bring together scores of ideas on how to develop
technology to track and deflect objects heading towards the Earth. The
gathering will also consider the sticky problem of public relations - is
it best to warn people if the worst comes to the worst?
"The collision of a moderately large asteroid or comet, also referred to
as a near-Earth object (NEO), with Earth would have catastrophic
consequences," writes Brent William Barbee of Emergent Space
Technologies Inc in a discussion paper to be presented at the meeting.
"Such events have occurred in the past and will occur again in the
future. However, for the first time in known history, humanity may have
the technology required to counter this threat."
Many smaller objects around the Earth's orbit break up when they reach
the atmosphere, with no impact beyond a short fireworks display. An NEO
wider than 1km, however, collides with Earth every few hundred thousand
years and an NEO larger than 6km, which could cause mass extinction,
will collide with Earth every 100m years. Experts agree that we are
overdue for a big one.
All eyes for the moment are on Apophis, a 390-metre wide asteroid
discovered in 2004, which has an outside chance of hitting the Earth in
2036. If it struck, Apophis would release more than 100,000 times the
energy released in the nuclear blast over Hiroshima. Thousands of square
kilometres would be directly affected by the blast but the whole planet
would see the effects of the dust released into the atmosphere. There
could be dark skies for a year or more and crops worldwide would be
destroyed.
====================
Scientists consider asteroid defense
'Gravity tug' possible solution to danger of close flybys
By Robert S. Boyd, March 9, 2007
NASA and the Air Force are studying ways to ward off a medium-sized
asteroid that will streak within 18,000 miles of Earth in 2029 and has
an extremely slight chance of crashing into our planet in 2036. Ideas
discussed this week at a Planetary Defense Conference in Washington
include a "gravity tug" or "space tractor" that would hover near the
space rock and tow it into a safe orbit. Other possibilities include a
head-on collision with an unmanned spaceship or a nuclear explosion.
In the past eight years, 754 asteroids bigger than 1 kilometer (about
six-tenths of a mile, or 3,280 feet) across have been detected orbiting
near Earth. But none is expected to come as close as a smaller one
called Apophis, which was discovered just before Christmas in 2004.
Named after an ancient Egyptian god of evil, Apophis is about 900 feet
long - three times the length of a football field - and is traveling at
a speed of 12,000 mph. If an object that size hit Earth, it would
"destroy England or Northern California," said Steven Chesley, an
asteroid expert at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Even if it landed in the Pacific Ocean, it would cause a tsunami as big
as the one that devastated Indonesia and neighboring countries in 2004,
according to Clark Chapman, a planetary scientist at the Southwest
Research Institute in Boulder, Colo.
Simon "Pete" Worden, the director of NASA's Ames Research Center in
Mountain View, Calif., told the conference that the United States has
the technology needed to send a mission to deflect an asteroid such as
Apophis, but the Bush administration hasn't requested money to pay for
it. "We don't yet have the resources to do much about this," Worden
said. NASA's budget includes $4 million a year to study the asteroid threat.
Edward Lu, [an] astronaut at the Johnson Space Center in Houston,
estimated that the cost of a gravity tug would be about $300 million. He
said the gravitational force of a 1-ton robotic spacecraft orbiting just
ahead of the asteroid would gradually pull the space rock out of Earth's
way. Other methods, such as bombing the asteroid, might break it into
smaller pieces that could be even more dangerous to our planet, Lu said.
Apophis gave NASA a brief scare at first, when astronomers thought it
had a 3 percent chance of hitting Earth. Additional evidence, however,
soon eliminated any danger of a collision in 2029 and reduced the odds
of an impact in 2036 to 1 in 45,000.
"Apophis is not really a threat," said Don Yeomans, the manager of
NASA's NEO (Near Earth Object) office in Pasadena, Calif. However, he
said, the passage of the big rock across the sky will be visible to the
naked eye in Europe and North Africa. "It's going to be quite a sight,"
Yeomans said.
About 70 percent of the estimated 1,090 asteroids bigger than 1
kilometer across have been detected and their orbits identified. Now
NASA is under congressional orders to find 90 percent of the much more
numerous small asteroids - those at least 140 meters (459 feet) across -
by 2020.
"They run the gamut from wimpy ex-comets to slabs of solid iron,"
Yeomans said. "Our goal is to eliminate 90 percent of the risk from
these smaller objects."
"We can't prevent hurricanes or tornadoes," said Russell "Rusty"
Schweikert, another former astronaut, "but we can prevent this asteroid
impact."
To accomplish the goal, the Air Force is financing a system of
ground-based telescopes in Hawaii called Pan-Starrs that will start
searching in 2010 for asteroids or comets that are on a collision course
with Earth. The National Science Foundation is building a Large Synoptic
Survey Telescope in Chile that will scan the sky every three days for
faint objects - including asteroids - starting in 2014.
Although almost all possibly dangerous asteroids can be detected, the
risk can't be reduced to zero. "There's always a tiny chance that
something is hiding behind the sun," said Alan Harris, a member of the
Space Science Institute in Boulder, Colo.
===================
Astronomers hash out defense against asteroids
A billion dollars needed to spot potential killer impacts.
Jeff Kanipe: 9 March 2007
Astronomers trying to save the world from Earth-threatening asteroids
have this week composed a white paper outlining the threat and what
needs to be done about it.
Although it isn't their first white paper on the subject - that was
released in 2004 - it is the first mandated by Congress. This,
scientists hope, may mean that their conclusions will be taken more
seriously by decision-makers in Washington.
In 2005, Congress passed a bill authorizing NASA to search for asteroids
as small as 140 metres that could possibly strike the Earth. The bill,
however, provided no money for the search.
On Monday, Simon 'Pete' Worden, director of NASA's Ames Research Center,
said that the cost of finding at least 90% of the 20,000 estimated
potential Earth-killers by 2020 would cost about $1 billion. US
government employees, including NASA scientists, don't usually make
public requests for more cash, but Worden was clear: "We know what to
do, we just don't have the money."
If Worden and his colleagues had their way, they would catalogue and
track all objects of 140 metres or larger. This would require a
dedicated space-based telescope and more time on the two ground-based
radar facilities currently used to spot incoming asteroids, scientists
suggested at the meeting. This would hopefully provide enough time to
deflect a big, bad rock.
Scientist at the conference were keen to focus on how to do this. One
idea would be to use a robotic spacecraft as a 'tugboat' that would
physically attach itself to the asteroid and push it into a new orbit.
The problem is that the surface of an asteroid would probably be rough
and unconsolidated. An alternative would be to have a spacecraft hover
above the asteroid surface, using gravity as a towline (see 'Gravity
tractors beat bombs').
Other proposals call for nuclear detonations to push the asteroid off
target, anchoring a tether onto a rock so that a spacecraft can sling it
athwart, or attaching solar sails to blow it off course.
In the meantime, astronomers acknowledge that they still have a lot to
learn about the nature of asteroids in order to better assess our
vulnerability. William Ailor of the Aerospace Corporation and general
chair of the conference, says [the white paper] will be posted on the
conference web page when finalised. But he hopes it won't stop there.
"I know Congress is getting interested in this and I think that's very
encouraging," Ailor says.
--
+++++++++++++++++++++++++++++++++++++++++++
NEO News (now in its thirteenth year of distribution) is an informal
compilation of news and opinion dealing with Near Earth Objects (NEOs)
and their impacts. These opinions are the responsibility of the
individual authors and do not represent the positions of NASA, the
International Astronomical Union, or any other organization. To
subscribe (or unsubscribe) contact dmorrison@xxxxxxxxxxxxx For
additional information, please see the website
http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute
original material from these notes, fully or in part, please include
this disclaimer.
-----------------------------------------------------------------------------
** The FMO Mailinglist ** For information on the list, subscribe/unsubscribe info etc. go to http://home.wanadoo.nl/marco.langbroek/fmo.html ** Post messages to: fmo@xxxxxxxxxxxxx ** list admin: Marco Langbroek, fmo-admins@xxxxxxxxxxxxx ** Message archive: //www.freelists.org/archives/fmo/ **
------------------------------------------------------------------------------
Other related posts:
