[FPSPACE] FW: NEO News (03/09/07) Planetary Defense Conference Pt 2
ljk4 at msn.com
Fri Mar 9 23:17:29 EST 2007
>From: David Morrison <dmorrison at arc.nasa.gov>
>To: David Morrison <dmorrison at arc.nasa.gov>
>Subject: NEO News (03/09/07) Planetary Defense Conference Pt 2
>Date: Fri, 9 Mar 2007 16:20:41 -0800
>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.
>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
>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
>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
>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
>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
>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
>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
>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
>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
>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
>"We can't prevent hurricanes or tornadoes," said Russell "Rusty"
>Schweikert, another former astronaut, "but we can prevent this asteroid
>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,
>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 at arc.nasa.gov. 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.
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