[Senate Hearing 108-1020]
[From the U.S. Government Publishing Office]
S. Hrg. 108-1020
NEAR EARTH OBJECTS
=======================================================================
HEARING
before the
SUBCOMMITTEE ON SCIENCE, TECHNOLOGY,
AND SPACE
of the
COMMITTEE ON COMMERCE,
SCIENCE, AND TRANSPORTATION
UNITED STATES SENATE
ONE HUNDRED EIGHTH CONGRESS
SECOND SESSION
__________
APRIL 7, 2004
__________
Printed for the use of the Committee on Commerce, Science, and
Transportation
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SENATE COMMITTEE ON COMMERCE, SCIENCE, AND TRANSPORTATION
ONE HUNDRED EIGHTH CONGRESS
SECOND SESSION
JOHN McCAIN, Arizona, Chairman
TED STEVENS, Alaska ERNEST F. HOLLINGS, South
CONRAD BURNS, Montana Carolina, Ranking
TRENT LOTT, Mississippi DANIEL K. INOUYE, Hawaii
KAY BAILEY HUTCHISON, Texas JOHN D. ROCKEFELLER IV, West
OLYMPIA J. SNOWE, Maine Virginia
SAM BROWNBACK, Kansas JOHN F. KERRY, Massachusetts
GORDON H. SMITH, Oregon JOHN B. BREAUX, Louisiana
PETER G. FITZGERALD, Illinois BYRON L. DORGAN, North Dakota
JOHN ENSIGN, Nevada RON WYDEN, Oregon
GEORGE ALLEN, Virginia BARBARA BOXER, California
JOHN E. SUNUNU, New Hampshire BILL NELSON, Florida
MARIA CANTWELL, Washington
FRANK R. LAUTENBERG, New Jersey
Jeanne Bumpus, Republican Staff Director and General Counsel
Robert W. Chamberlin, Republican Chief Counsel
Kevin D. Kayes, Democratic Staff Director and Chief Counsel
Gregg Elias, Democratic General Counsel
------
SUBCOMMITTEE ON SCIENCE, TECHNOLOGY, AND SPACE
SAM BROWNBACK, Kansas, Chairman
TED STEVENS, Alaska JOHN B. BREAUX, Louisiana, Ranking
CONRAD BURNS, Montana JOHN D. ROCKEFELLER IV, West
TRENT LOTT, Mississippi Virginia
KAY BAILEY HUTCHISON, Texas JOHN F. KERRY, Massachusetts
JOHN ENSIGN, Nevada BYRON L. DORGAN, North Dakota
GEORGE ALLEN, Virginia RON WYDEN, Oregon
JOHN E. SUNUNU, New Hampshire BILL NELSON, Florida
FRANK R. LAUTENBERG, New Jersey
C O N T E N T S
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Page
Hearing held on April 7, 2004.................................... 1
Statement of Senator Brownback................................... 1
Witnesses
Citters, Dr. Wayne Van, Director, Division of Astronomical
Sciences, National Science Foundation.......................... 7
Prepared statement........................................... 9
Griffin, Michael D., Head of the Space Department, Applied
Physics Lab, Johns Hopkins University.......................... 29
Prepared statement........................................... 31
Johnson, Dr. Lindley N., Program Scientist, Near Earth Object
Observation Program, National Aeronautics and Space
Administration................................................. 11
Prepared statement........................................... 13
Lu, Dr. Edward, NASA Astronaut and President, B612 Foundation.... 35
Prepared statement........................................... 37
Schweickart, Dr. Russell L., Chairman of the Board, B612
Foundation..................................................... 39
Prepared statement........................................... 41
Stokes, Dr. Grant H., Chairman, Near Earth Object Science
Definition Team, MIT Lincoln Laboratory........................ 23
Prepared statement........................................... 25
Appendix
Rohrabacher, Dana, Congressman (R-CA), prepared statement........ 59
NEAR EARTH OBJECTS
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WEDNESDAY, APRIL 7, 2004
U.S. Senate,
Subcommittee on Science, Technology, and Space,
Committee on Commerce, Science, and Transportation,
Washington, DC.
The Committee met, pursuant to notice, at 2:30 p.m. in room
SR-253, Russell Senate Office Building, Hon. Sam Brownback,
presiding.
OPENING STATEMENT OF HON. SAM BROWNBACK,
U.S. SENATOR FROM KANSAS
Senator Brownback. The hearing will come to order. Thank
you all very much for coming today. My apologies for being
nearly a half hour late. We had two votes scheduled back to
back and I had to go over and vote. I apologize for that to our
witnesses and to others.
We appreciate people being able to come particularly on
this Holy Week of Passover and Easter. It's quite a week and I
appreciate our witnesses are willing to come into town for this
particular important hearing that we're having.
Most people have watched Hollywood movies about asteroids,
or more correctly ``Near-Earth Objects''--NEOs for short--
striking the Earth. Yet few know what is real and what is not.
Fewer still know what your government is doing about this
threat, or not doing for that matter.
Asteroid 2004FH, approximately 100 feet wide, passed within
about 25,000 miles of the Earth on March 18, 2004. This is
equivalent to riding in an airliner and seeing a small plane
suddenly pass a few hundred feet off the wing. It's a pretty
scary occurrence. Had this asteroid hit the Earth, as a
somewhat bigger one did in 1908, it would have released over a
megaton of energy. This is the explosive yield of a large
nuclear weapon. Yet we had only a few days warning of Asteroid
2004FH. Other similar objects just missed us in the past few
years and we didn't even see them until they were past.
Scientists tell us that a big asteroid, ten miles in
diameter, destroyed the dinosaurs 65 million years ago.
Asteroids are the small bits left over from the formation of
the solar system billions of years ago. If we look up at the
moon we can see the results of billions of years of bombardment
in its shattered face. The Earth suffered similar hits but most
have healed due to Earth's weather and geological processes.
Small asteroids hit the Earth every year; about thirty
struck the upper atmosphere last year. They each release as
much energy as a small atomic bomb. Fortunately the atmosphere
protects us from these little asteroids. But ones such as the
March 18 object could devastate a large city. Experts tell us
that we run about the same risk of dying in an airline crash as
we do dying from an asteroid strike. This is serious and
warrants serious attention by our government.
The President's new space exploration vision mandates that
we focus our attention on the opportunities inherent in moving
human presence into the solar system. But it also raises the
question as to potential threats out there. Panels of experts
have met over the past few years. All tell us that the threat
of NEO impact is real. At the smallest scale, those that strike
us several times a month could be confused in a crisis as a
nuclear attack. Asteroids the size of the one a few weeks ago
hit Earth several times a century. The experts also tell us
that we could have the ability to detect these objects before
they hit and do something about it.
Today we are meeting to consider whether Congress should
pass legislation to do something about this threat from space.
We will hear from program managers within NASA and the National
Science Foundation on what is being done now and what is
planned.
We will hear from the experts in our scientific community
on what they recommend we do to find the threatening objects
before they hit. We will hear from space development experts on
how we could build spacecraft quickly and cheaply to meet
threatening objects deep in space to find out about them and
divert them as necessary.
And finally, we will hear from former and current
astronauts how these objects might fit into the President's
exciting new space exploration vision, both as targets for
scientific exploration and commercial use, as well as how to
divert the threatening ones.
For the first time in this planet's long history, the life
that lives here can take control of its own long-term destiny
in this regard. The clockwork of the solar system eliminated
dinosaurs. Humans were one result of that event. The question
before us is to whether and how humans will deal with this
aspect of our collective future.
I want to enter into the record then as well, a statement
from Congressman Dana Rohrabacher who could not be here with us
today. They are on break on the House side and he has proposed
a bill to deal with Near Earth Objects and that will be put
into the record.
[The information referred to follows:]
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Senator Brownback. I'm delighted you all could join us
today. I look forward to this informative hearing giving the
Senate some idea of what all is being done and what needs to be
done.
Our first panel is Dr. Wayne Van Critters--Citters?
Dr. Van Citters. Van Citters.
Senator Brownback. Van Citters, excuse me. That's a near
miss for me on the pronunciation. Division Director, Division
of Astronomical Sciences, National Science Foundation. I'm
delighted you're here.
Dr. Lindley Johnson, Program Manager, Near Earth Objects
Observation Program at NASA.
Gentlemen. We're delighted to have both of you here. I
apologize for being late. Your full statement will be placed in
the record and so you're free to summarize or to present
however you'd like to. Dr. Van Citters.
STATEMENT OF DR. WAYNE VAN CITTERS, DIRECTOR,
DIVISION OF ASTRONOMICAL SCIENCES,
NATIONAL SCIENCE FOUNDATION
Dr. Van Citters. Thank you sir. Chairman Brownback, Ranking
Member Breaux, and distinguished Members of this Subcommittee.
We appreciate the opportunity to present the position of
the National Science Foundation on the important subject of
Near Earth Objects this afternoon and in responding, I'll
present a picture of NSF's current activities in this area. We
are supporting research into the nature and origin of these
objects as well as potential important contributions that NSF
support, instrumentation and techniques could make to an
expanded discovery and characterization effort.
As I'm sure the Committee is aware, NSF supports a wide
range of basic research in astronomy from solar system studies
to cosmology all the way to the very nature of matter and
energy and what we support is driven by the interest of the
scientific community that we support and our merit review
process.
The Committee is probably also aware of the formation of
the Astronomy and Astrophysics Advisory Committee. This is
after the study that was done on possibly combining
astronomical research at NSF and NASA and the purpose of this
Committee is to advise both NSF and NASA and to some extent DOE
on areas of common interest and cooperation. And in this recent
March 15 report, the first report that this Joint Advisory
Committee made, they underscored along with a number of other
issues the number and nature of Near Earth Objects as an
important and fundamental question to be investigated over the
coming decade.
We support a wide range of individual investigator grants
and operations at Arecibo, the National Astronomical and
Ionospheric Center, in particular the Planetary Radar Program
there, and these investigations look at the nature of Near
Earth Objects and I've given a few examples of those
investigations in the written testimony.
In general, they concentrate on the internal structure and
origin of the objects whether they're binary in nature. If they
are binary or multiple in nature, how that came to be and for
some of the brighter ones, with more modern instrumentation or
even capable of doing some rather detailed mineralogical
analysis of the actual composition of the objects themselves.
We've seen an increasing interest in this area in the
scientific community through the proposals presented to us over
about the past 2 to 3 years and are making choices of which
areas to support through our normal merit review of the
proposals.
Looking to the future. I detailed in the statement the
results of the NASA study which was reported out in late 2002,
I believe, which outlines the current status of the Space Guard
Program which I'm sure Lindley will talk about in much more
detail and recommends next steps.
Very briefly, this treats the post-2008 period and in its
conclusions urges that a catalogue of objects larger than 140
meters in diameter, so considerably larger than the one that
passed by us a few weeks ago, be completed which would give a
complete census at about the 90 percent certainty level.
The study estimates that the same approaches would provide
60 to 90 percent uncertainty--or 60/90 percent completion for
objects larger than 50 meters. An object of this size would
provide quite a large air burst but not anything like a
dinosaur extinction event.
The study sets out several approaches both ground and space
based to consider in reaching the above goal and it gives a
cost and benefit analysis. So we think it provides a rather
solid basis for looking at how to go forward in the future.
In that regard, our plans at NSF we are considering
building on that NASA study and charging a Subcommittee of our
Joint Astronomy and Astrophysics Advisory Committee with
looking at an appropriate effort following on the Space Guard
effort that would span both agencies and in particular for NSF
how we would increase our ground based effort in this area.
We would foresee that it would certainly involve an
increase in the support of individual investigator efforts
looking into the nature and origin of the object themselves
provided that our community interests and the proposal quality
warrants it.
It would also however I think look at what's being proposed
and highly rated in three of the National Research Council and
the Department of Defense looking at trade studies and relative
merit of these two possible instrumentation efforts for
contributions to the future of the detection effort. And in
particular there are estimates that the LSST and possibly Pan-
STARRS could indeed respond to the challenge of cataloguing all
of the 140 meter diameter or larger asteroids within seven to
twenty years.
In conclusion, we're pursuing a significant amount of basic
research in this area and we are laying plans for new
facilities and expanded research activity that speak to many of
the basic questions about the objects themselves and are
confident that the body of knowledge that we gain by this
effort will have important application to any eventual risk
mitigation effort.
Again, I thank you for the opportunity to appear and we'd
be happy to respond to any questions.
[The prepared statement of Dr. Van Citters follows:]
Prepared Statement of G.W. Van Citters, Director, Division of
Astronomical Sciences, National Science Foundation
Chairman Brownback, Ranking Member Breaux, and distinguished
members of the Subcommittee. Thank you for the opportunity to present
the position of the National Science Foundation on the important
subject of Near Earth Objects. In responding to the questions that the
Committee has presented to us, I will present a picture of NSF's
support of research into the nature and origin of these objects, as
well as potential important contributions that NSF-supported
instrumentation and techniques could make to an expanded discovery and
characterization effort.
Background and Context
The Division of Astronomical Sciences supports basic research in
astronomy covering a very wide range of subjects--from studies of
objects in our own solar system to investigations of the beginning of
the universe, including the very nature of matter and energy. In
planning and conducting its programs, the Division benefits from the
advice of the scientific community in many ways, including the recently
established Astronomy and Astrophysics Advisory Committee (AAAC,
jointly advising NSF, NASA, and DOE). The establishment of the AAAC
recognizes the value of an integrated strategy to address national
efforts to answer questions about our origins and our future. The
number and nature of NEOs are clearly fundamental questions about both
our origins and our future. In their March 15, 2004 report the AAAC
recommended a coordinated implementation effort to ensure timely
development of the Large Synoptic Survey Telescope, calling it a key
facility for the detection of potentially hazardous earth-intersecting
objects as small as 300 meters.
Current Activity
A number of awardees in our Planetary Astronomy Program are
investigating Near Earth Objects (NEOs). The proposals funded by our
program are determined by the interest of the research community, as
reflected in the number and subject matter of proposals that we
receive, and the results of our merit review of these proposals.
As one example, Dr. Derek Richardson at the University of Maryland
will be modeling the tidal disruption of near Earth asteroids (NEAs) by
the Earth's gravitational field to determine the frequency of binary
NEA formation and the typical characteristics of the resulting binary
asteroids. The results from this research will give insight into the
internal structure of NEAs and may have implications for hazard
mitigation strategies.
In another effort, Richard Binzel at MIT will measure the near-
infrared spectral properties of 40-60 NEOs per year. The observations
will balance measurements that push the state-of-the-art limits of the
technology for the smallest and faintest objects and measurements that
provide sufficient detail for detailed mineralogical analysis.
Research in this area also represents a substantial fraction of the
use of the Arecibo planetary radar system, characterizing sizes,
shapes, rotation rates, and configurations (single or binary, e.g.).
The smallest system yet observed (a binary of 120m and 40 m diameter
components) was discovered in 2003. Measurements from a combination of
Arecibo and NASA's Goldstone antenna from 1991 through 2003
demonstrated the existence of the Yarkovsky effect. This effect is an
acceleration of the body related to the time delay between the
absorption of solar radiation and the re-emission in the infrared. The
observations clearly indicated that the acceleration must be included
in orbit predictions.
We have observed that the number of proposals to investigate NEOs
has been increasing annually for the last few years. Of the proposals
we receive on this topic, those that do best in our merit review
competition are those proposing to characterize the physical properties
of the objects. What are they made of? How were they formed and when?
I believe NSF is currently playing the role for which it is best
suited. It is funding individual investigators to further our
understanding of the physical make-up of NEOs. The proposals for these
investigations are subject to our normal merit review, thus insuring
high quality basic research on these objects. In addition, it provides
access to tools such as Arecibo that can enhance the discovery process.
Looking to the Future
In recent years, there has been an increasing appreciation for the
hazards posed by near-Earth objects, those asteroids and periodic
comets (both active and inactive) whose motions can bring them into the
Earth's neighborhood. In August of 2002, our colleagues at NASA
chartered a Science Definition Team to study the feasibility of
extending the search for near-Earth objects to smaller limiting
diameters. The formation of the team was motivated by the good progress
being made toward achieving the Spaceguard goal of discovering 90
percent of all NEOs with diameters greater than 1 km by the end of
2008. This raised the question of what, if anything, should be done
with respect to the much more numerous smaller, but still potentially
dangerous, objects. The team was tasked with providing recommendations
to NASA as well as the answers to seven specific questions. We believe
that the answers to these questions could form a solid basis for the
direction of our research efforts and for more detailed studies of the
best integrated strategy to carry on at the end of Spaceguard in 2008.
What are the smallest objects for which the search should be
optimized? The Team recommends that the search system be
constructed to produce a catalog that is 90 percent complete
for potentially hazardous objects (PHOs) larger than 140
meters.
Should comets be included in any way in the survey? The Team's
analysis indicates that the frequency with which long-period
comets (of any size) closely approach the Earth is roughly one-
hundredth the frequency with which asteroids closely approach
the Earth and that the fraction of the total risk represented
by comets is approximately 1 percent. The relatively small risk
fraction, combined with the difficulty of generating a catalog
of comets, leads the Team to the conclusion that, at least for
the next generation of NEO surveys, the limited resources
available for near-Earth object searches would be better spent
on finding and cataloging Earth-threatening, near-Earth
asteroids and short-period comets. A NEO search system would
naturally provide an advance warning of at least months for
most threatening long-period comets.
What is technically possible? Current technology offers
asteroid detection and cataloging capabilities several orders
of magnitude better than the presently operating systems. This
report outlines a variety of search system examples, spanning a
factor of about 100 in search discovery rate, all of which are
possible using current technology. Some of these systems, when
operated over a period of 7-20 years, would generate a catalog
that is 90 percent complete for NEOs larger than 140 meters.
How would the expanded search be done? From a cost/benefit
point-of-view, the report concludes that there are a number of
attractive options for executing an expanded search that would
vastly reduce the risk posed by potentially hazardous object
impacts. The Team identified a series of specific ground-based,
space-based and mixed ground-and space-based systems that could
accomplish the next generation search. The choice of specific
systems would depend on the time allowed for the search and the
resources available.
What would it cost? For a search period no longer than 20
years, the Team identified several systems that they felt would
eliminate, at varying rates, 90 percent of the risk for sub-
kilometer NEOs, with costs they estimate to range between $236
million and $397 million for both ground and space components.
They conclude that all of these systems have risk reduction
benefits which greatly exceed the costs of system acquisition
and operation.
How long would the search take? The Team concludes that a
period of 7-20 years is sufficient to generate a catalog 90
percent complete to 140-meter diameter, which will eliminate 90
percent of the risk for sub-kilometer NEOs. The specific
interval would depend on the choice of search technology and
the investment allocated.
Is there a transition size above which one catalogs all the
objects, and below which the design is simply to provide
warning? The Team concluded that, given sufficient time and
resources, a search system could be constructed to completely
catalog hazardous objects with sizes down to the limit where
air blasts would be expected (about 50 meters in diameter).
Below this limit, there is relatively little direct damage
caused by the object. Over the 7-20 year interval (starting in
2008) during which the next generation search would be
undertaken, the Team suggests that cataloging is the preferred
approach down to approximately the 140-meter diameter level and
that the search systems would naturally provide an impact
warning of 60-90 percent for objects as small as those capable
of producing significant air blasts.
The path from where we are today to where we should be in 2014 is
not defined in the conclusions of the study that NASA sponsored. Clear
goals are defined; how one might reach them is wisely left to the
scientific and technical community. At the national level, we must now
examine these goals in detail, validate the conclusions, and determine
how they might best be achieved.
NSF Plans for the Future
We are considering asking the AAAC to form a subcommittee to advise
on the effort that would be appropriate beyond Spaceguard. Broadly
based in the scientific and technical community, this subcommittee
would consider the conclusions of recent studies, extract necessary
research directions that would help us better understand the origin and
nature of the objects known to date and help to chart the most
productive course into the future. By the very nature of the charge to
the AAAC, this would be an integrated look at the ground-based and
space-based efforts that would make the most effective scientific
advances in this area.
Of particular interest to NSF would be the expansion of the
individual investigator-driven basic research that we currently
support, and a more detailed understanding of how such projects as the
Large Synoptic Survey Telescope (LSST) and Panoramic Survey Telescope
and Rapid Response System (Pan-STARRS) might best contribute to the
discovery and characterization effort in the future.
The LSST is a proposed single 8.4meter aperture, very wide field
telescope capable of surveying the entire sky visible from one
hemisphere every two weeks. It has a variety of science drivers
including the characterization of dark matter and dark energy, the
discovery of many classes of transient objects such as supernovae and
gamma-ray burst counterparts, and NEOs.
Pan-STARRS, an Air Force funded project under construction in
Hawaii, will be composed of 4 individual telescopes of 1.8meter
aperture observing the same region of sky simultaneously. In survey
mode, i.e., searching for NEOs, Pan-STARRS will cover 6,000 square
degrees per night. The whole available sky as seen from Hawaii will be
observed 3 times during the dark time in each lunation.
The LSST's ability to make fast, wide, and faint observations may
make it uniquely suited to detecting small NEOs. A model LSST survey
covering 9,000 square degrees of sky along the ecliptic, three or four
times a month, to a limiting V magnitude of 24.0, achieved a ten-year
completeness of about 90 percent for NEOs larger than 250 m, and about
80 percent for NEOs down to 140 m as called for by the NASA study. The
requirements placed on the telescope, telescope operations, data system
and detectors by the NEO detection challenge are considerable.
By reaching objects 100 times fainter than those currently observed
in the NEO surveys, Pan-STARRS is being designed to help complete the
Congressional mandate to find and determine orbits for the 1-km (and
larger) threatening NEOs. Further, it should push the detection limit
for a complete (99 percent) sample down to objects as small as 300-
meters in diameter.
Design studies over the next several years will be needed to
determine the strategy for attacking the NEO problem and whether it is
best carried out with a single telescope like the LSST or whether an
array of smaller telescopes such as Pan-STARRS is more appropriate for
this particular problem. NSF's Division of Astronomical Sciences has
begun planning for such studies and we have been actively joined by our
colleagues at NASA, who will contribute their knowledge and experience
in the handling of large data bases and archives.
Conclusion
In conclusion, Mr. Chairman, NSF is already pursuing a significant
amount of basic research in this important area. We are guided, as
always, by the scientific community through our merit review process.
We are laying plans for new facilities and expanded research activity
that speak to many basic questions about the nature and origin of these
objects, and are confident that the body of knowledge so gained will
have important application to any eventual risk-mitigation effort.
Again I thank you for the opportunity to appear and would be happy
to respond to any questions.
STATEMENT OF DR. LINDLEY N. JOHNSON, PROGRAM
SCIENTIST, NEAR EARTH OBJECT OBSERVATION PROGRAM, NATIONAL
AERONAUTICS AND SPACE ADMINISTRATION
Dr. Johnson. Thank you, Mr. Chairman, for the opportunity
to present to the Subcommittee information on this important
subject on NEOs.
At the request of Congress, NASA conducts the NEO
observation program to research the population of the larger
asteroids and periodic comets that pass relatively close to the
Earth and may one day pose a collision hazard with our planet.
Our NEO program has been quite successful in finding these
larger objects in the first 5 years of its effort.
In the effort to gain a better understanding of this
hazard, NASA's Office of Space Science has been conducting a
search of space near the Earth's orbit to understand the
population of objects that could do significant damage to the
planet should there be a collision.
Commonly referred to as a ``Space Guard Survey,'' this
research seeks those asteroids and periodic comets that come
within an astronomically close 50 million kilometers of the
Earth. The objective of this survey is to detect within a 10-
year period at least 90 percent of the NEOs that are greater
than one kilometer in size and predict their orbits into the
future.
Currently, slightly over 4 million per year is budgeted for
the program. This funds modest search efforts, typically using
refurbished ground based telescopes of about one meter aperture
and wide field of view coupled with digital imaging in order to
cover significant portions of the sky each month.
Presently 5 NEO search projects are either wholly or
largely funded with this resource. Also important to the effort
is the observation correlation and initial orbit determination
done by the Minor Planet Center which is operated by the
Smithsonian Astrophysical Observatory and the High Accuracy
Orbit Propagation and Project Coordination done by NASA's NEO
Project Office at the Jet Propulsion Lab.
The chart you've been handed summarizes the progress to
date in finding the Near Earth Asteroids or NEAs greater than
one kilometer in size. The program continues to make steady
progress since it started in 1998 to the goal of finding at
least 90 percent of these NEOs. As of the end of March, 514 of
the 702 known NEAs determined to be larger than one kilometer
have been found by the program out of an estimated total
population of about 1,100.
We have also found 11 of 49 known Earth approaching comets.
In addition, 1,866 of the 2,032 known Near Earth Asteroids of
smaller size have been found. Because the projects are always
refining the detection techniques, the discovery of smaller
objects is becoming more frequent.
None of these objects found to date are on impact
trajectories with the Earth in the next 100 years.
The results of the recent study by the Science Definition
Team which Dr. Van Citters referred to which was commissioned
by my office and you'll hear more about it from Grant Stokes,
will show that it is entirely appropriate that we search for
the larger NEOs first, because all factors considered, that is
where the greatest risk from an undetected asteroid on an
impact trajectory lies. This is principally due to the
worldwide devastation it would cause. It is orders of magnitude
above what a smaller few hundred meter sized impact would
create and could well disrupt human civilization for decades
after an impact.
Completion of the current effort to find these large
objects will do much to reduce this uncertain risk and find the
objects many decades before any impact threat. But until the
total population of these objects is known, there is always the
chance that an object bound for a near term impact maybe
discovered similar to the real life scenario which unfolded 10
years ago, when comet Shoemaker-Levy 9, was discovered only in
March 1993 inbound for a July 1994 impact on Jupiter.
It should be understood that the NEO Observation Program is
merely a science survey and does not provide a leakproof
warning network for impact of any size natural object large or
small. Such a comprehensive network would require an order of
magnitude increase in our funding and the cooperative efforts
of several government departments and agencies like with NSF.
Operational experience with the current system shows that
for every one kilometer of greater size asteroid found, there
are three to four smaller size asteroids also discovered.
But the true ratio of the small to larger asteroids is
thought to be over 100 to one. Because of the limitations of
the current search systems, the discovery of smaller asteroids
is only possible in a significantly smaller volume around the
Earth. If our sensors can detect a one kilometer sized asteroid
at 50 million kilometers, they can also see a 100 meter
asteroid, but at perhaps only half a million kilometers or a
little beyond the moon's orbit.
But at planetary orbital velocities, if the object is on
impact trajectory of the Earth, it would cover even this
distance in less than a day.
Thus, the detection of a relatively small asteroid on a
destiny with Earth could also come with relatively short
reaction time. The impact of a 100 meter asteroid on Earth
could do significant damage at the surface as this is estimated
to result in an approximately a 50 megaton energy release at or
perhaps slightly above the surface. This will result in much
loss of life if the impact were in a populated area.
It is therefore prudent that we begin to put into place
contingency plans such as an internal NASA notification plan we
are drafting to deal with such a relatively unlikely but
extremely high consequence event.
Thank you for the opportunity to speak at this hearing and
I'd be happy to respond to any questions you have.
[The prepared statement of Dr. Johnson follows:]
Prepared Statement of Lindley N. Johnson, Program Scientist, Near Earth
Object Observation Program, National Aeronautics and Space
Administration
Thank you, Mr. Chairman, for the opportunity to present to the
subcommittee information on the important subject of Near Earth
Objects. At the request of Congress, NASA conducts the Near Earth
Object (NEO) Observation Program to discover the larger sized asteroids
(greater than 1 kilometer or 0.62 miles in size) and periodic comets
that pass relatively close to the Earth and may one day pose a
collision hazard with our planet. Our NEO program has been quite
successful in finding these larger objects in the first five years of
the effort.
Background
The Earth orbits about the Sun in a cloud of planetary debris still
left from the formation of the Solar System. This debris ranges from
micron-sized dust particles, to meteoroids at sand grain to a few
meters in size, and to asteroids and comets that are tens of meters to
several kilometers in dimension. Collision with meter-sized meteoroids
is almost a weekly event for the Earth, but the surface is well
protected from these common events by its atmosphere, which will cause
objects less than about 50 meters in size and of average density to
disintegrate harmlessly before reaching the ground. However, even the
relatively active surface of the Earth still bears scars of impacts
from space, with 168 craters worldwide--some up to 300 kilometers in
size--having been identified to date.
Though collisions with larger bodies are much less frequent now
than in the early stages of planet formation in the Solar System, they
do still occur. Very significant events, capable of causing damage at
the surface, will happen on scales of a few hundred to a thousand
years. But we do not know when the next impact of an object of
sufficient size to cause widespread devastation at ground level may
occur. At the current state of knowledge, it is about as likely to
happen next week as in a randomly selected week a thousand years from
now.
The Survey
In an effort to gain better understanding of this hazard, NASA has
been conducting a search of space near the Earth's orbit to understand
the population of objects that could do significant damage to the
planet should there be a collision. Commonly referred to as the
``Spaceguard Survey'', NASA's Office of Space Science conducts this
research effort on ``Near Earth Objects (NEOs)''--that is, asteroids
and comets that come within an astronomically close distance, <50
million kilometers of Earth. The objective of this survey is to detect,
within a 10-year period, at least 90 percent of the NEOs that are
greater than 1 kilometer in size and to predict their orbits into the
future. The survey officially started in 1998 and to date, over 700
objects of an estimated population of about 1100 have been discovered,
so the effort is believed to now be over 70 percent complete and well
on the way to meeting its objective by 2008.
A few words of explanation on the parameters and limitations of the
survey may be appropriate. The threshold of 1 kilometer in size was
accepted for this survey because it is about the size asteroid that
current research shows would border on having a devastating worldwide
effect should an impact occur. Because of the orbital velocities
involved, impact on Earth of an asteroid of this size would instantly
release energies calculated to be equivalent to the detonation of
almost a 100,000 megaton nuclear device, i.e., more than all the
world's nuclear arsenals detonated at the same time. Not only would the
continent or ocean where the impact occurs be utterly devastated, but
the effects of the super-heated fragments of Earth's crust and water
vapor thrown into the atmosphere and around the world would adversely
affect the global weather for months to years after the event. Such an
event could well disrupt human civilization anywhere from decades to a
century after an impact.
A goal of 90 percent completeness was adopted as a compromise
driven between the level of resources that could be dedicated to this
effort and the time period practical to conduct the survey at this
level of technical capability. Currently, slightly over $4M per year is
budgeted to the NEO Observation Program within the Solar System
Exploration Division's Supporting Research and Analysis Program. This
funds modest search efforts, typically using refurbished, ground-based
telescopes of about 1-meter aperture and wide-field-of-view, coupled
with digital imaging in order to cover significant portions of the sky
each month. Presently, five NEO search projects are either wholly or
largely funded with this level of resource, along with significant
support to central processing of observations, orbit determination and
analysis. These five search projects are:
------------------------------------------------------------------------
Project Name Institute Principal Investigator
------------------------------------------------------------------------
Lincoln Near Earth Asteroid Research (LINEAR)
MIT/Lincoln Laboratory, Dr. Grant Stokes
MA
Near Earth Asteroid Tracking (NEAT)
Jet Propulsion Dr. Ray Bambery
Laboratory, CA
Lowell Observatory Near Earth Object Search
(LONEOS)
Lowell Observatory, AZ Dr. Edward Bowell
Catalina Sky Survey LPL, University of Mr. Steve Larson
Arizona
Spacewatch LPL, University of Dr. Robert McMillan
Arizona
------------------------------------------------------------------------
Both the LINEAR and NEAT projects operate using optical telescope
facilities owned and supported by research components of the U.S. Air
Force. This represents that service's entire contribution to the search
effort, but utilization and direction of these assets must be
coordinated with the cognizant Air Force Material Command offices. The
Spacewatch Project also receives some modest private funding.
Ten years was considered a reasonable amount of time for this level
of effort to bring the overall large asteroid population known to 90
percent completeness. No level of effort could ever be assured of
achieving absolute 100 percent completeness, because of the vast
difficulty in searching all possible orbit regimes and sources for
generation of new NEOs. It should also be understood that the NEO
Observation Program is merely a science survey and does not have the
resources to provide a ``leak-proof'' warning network for impact of any
size natural object, large or small. Such a comprehensive network would
require an order of magnitude increase in funding and could require the
cooperative efforts of several government departments and agencies.
Progress of the Program
The NEO Observation Program continues to make steady progress
toward the goal of finding at least 90 percent of the large NEO
population. As of the end of March 2004, 513 of the 750 known NEOs
(including 49 Earth-approaching comets) determined to be larger than 1
kilometer in size have been found by the program, of an estimated total
population of about 1100. In addition, the program found 1862 of 2032
known Near Earth Asteroids (NEAs) of smaller sizes. The MIT/Lincoln
Labs-led LINEAR project continues to be the leading search team, having
found 40 large NEOs in 2003 along with 196 smaller objects. Significant
contributions continue to be made by JPL's NEAT team (10 large and 58
smaller objects in the last year), Lowell Observatory's LONEOS project
(10 and 44), and the University of Arizona's Spacewatch project (2 and
54). The Lunar and Planetary Laboratory Catalina Sky Survey has gotten
back on line in the last few months of the year after an imager
upgrade, obtaining 8 discoveries, 2 of them larger than 1 km.
The chart below summarizes the progress to date on finding the NEAs
greater than 1 kilometer in size. A noticeable increase in the
discovery rate occurs after the NEO Observation Program started in
1998.
Budget. The FY 2004 budget for this program is $4,062K, a 2.8
percent increase to the previous year.
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Current Survey Operations
Detection. The NEO Observation Program wholly funds the operations
of four search projects and partially funds another. Routine operation
of these assets is highly automated, in order to maximize the sky
coverage obtained each month. Ground-based telescopes can only
effectively operate at night during the two to three weeks of the month
opposite the full moon, due to the sky brightness it causes, and when
weather (cloud cover) permits accessible clear sky. Telescope movement,
pointing, and imaging operations are all computer controlled via pre-
scripted software routines to optimize sky coverage and therefore
maximize object detections.
The images taken each night are then post-processed to detect
moving objects relative to the star background and obtain accurate
measurements, called ``observations'', of any detected object's motion
relative to the star background (a process called ``astrometrics''). A
group of these observations, usually a set taken from three to five
images of the same patch of sky at slightly different times each night,
is called a ``track''. These show the relative motion of an object,
which can then be analyzed with other observations of the same object
to determine its orbit. These observation tracks are then formatted for
bulk telecommunications to the Minor Planet Center. On a productive
night, a search project may extract hundreds of observations on moving
objects from its imaging data, most of which will be on Main Belt
Asteroids and only a small fraction, perhaps one or two if lucky, will
be determined to be NEOs. The search teams also routinely find comets
in their collected images.
The Minor Planet Center. All observations thought to be natural
small bodies (asteroids, comets and now Kuiper Belt Objects in the
outer Solar System) are sent to the Minor Planet Center (MPC), operated
by the Smithsonian Astrophysical Observatory at Cambridge,
Massachusetts, under the direction of Dr Brian Marsden. The MPC is
internationally recognized and officially chartered by the
International Astronomical Union to confirm the discovery of new
objects in the Solar System and confer their official designations. A
modest amount of NASA funding is sent to the MPC to support their work
in confirming NEO detections.
The MPC receives observations from around the world, with a
significant percentage coming from an informal international network of
amateur asteroid hunters. The orbital analyst at MPC attempts to
correlate them with the positions of tens of thousands of already known
objects. Failing that, the MPC will provisionally designate the
observations as a possible new object, determine an ``initial'' orbit
for it, and place it on a list for objects awaiting ``confirmation''.
This list of provisional objects, along with their predicted current
positions, is available via the MPC website for the community of
observers to use in attempts to obtain additional ``follow-up''
observations to confirm the existence and orbit parameters of a new
object.
The observation processing at the MPC is highly automated, as it
must be with a staff of only three to four analysts operating with a
very limited budget. However, initial orbit determination often
requires some analyst's massaging of the orbit fit to obtain the lowest
residuals across what may be observations with some inherent errors.
Because individual search sites can only do the roughest of orbit
calculations based on their own limited data, the MPC is, in most
cases, the first place where it will be known if a newly found object
poses an impact hazard to the Earth. Often a family of possible orbits
is initially obtained which must be narrowed with additional
observations. For newly found NEOs, the MPC solicits additional
observations from the community via a web-based ``NEO Confirmation
Page'', and in the most critical cases, via phone calls to known
observers in whatever part of the world is most likely to have the
earliest accessibility to viewing the object.
Follow-up Observations. Additional observations, either obtained by
another observer later the same night or on a subsequent night, even by
the same facility that first discovers an object, are essential to
confirming the objects existence and developing a more accurate orbit
for the object. For the most accurate orbit, it is best for the
observations to be obtained several days to a week or more after the
initial set in order to obtain a longer observed ``arc'' of the orbit
and, therefore, a broader fit of observation data. However, for NEOs,
the time allowed to elapse must be traded off between obtaining a
broader arc and getting an orbit established before the object is lost,
either because the initial orbit was too far in error, or, more likely,
the object is so small that it simply cannot be seen after only a few
days of its closest approach to Earth.
The informal network of amateur astronomers does much of the
follow-up observation work today. However, the search for NEOs is
beginning to enter an era when the objects being detected are simply
too faint to be seen by the equipment affordable to most amateurs.
Therefore, in the future, search systems must ensure they have enough
survey capacity available to do their own follow-up on new objects in a
timely manner.
High-accuracy Orbit Determination. The best orbit determination
requires enough observations spread over a sufficient arc of the orbit
to provide the best resolution of motion for the object and reduce the
influence of subsets of data with may have some components of error.
Again, getting the best results can be somewhat of an art form, but the
best orbital modeling for this reside with the NEO Program Office
established by NASA at the Jet Propulsion Laboratory in Pasadena,
California, and managed by Dr. Donald Yeomans. This office also
supports the orbit determination and navigation for NASA's
interplanetary missions to asteroids, comets, and moons of other
planets. Its NEO work is fully funded by NASA, and the high-accuracy
orbit determination capability is nicely complementary to the MPC's
observation processing and initial orbit determination abilities.
The NEO Program Office is able to use its orbital modeling
capability to predict the position of any known NEO up to 200 years
into the future, taking into account all the known gravitational
influences and orbital perturbations of the Sun, planets, and moons in
the Solar System. This can be done with a very high degree of precision
for asteroids that have been tracked for extended periods, particularly
multiple orbits, or for which high-precision observations have been
taken by planetary radar. High-precision radar observations can greatly
reduce the position and motion errors for the subset of objects that
come close enough to the Earth to allow its use.
High-precision prediction of newly discovered NEO orbits allows
them to be separated into those whose orbits will not be a collision
hazard to Earth for the foreseeable future and those which are in
orbits that pass close enough to Earth's that they may someday pose a
hazard. These ``Potentially Hazardous Asteroids (PHAs)'' are about a 20
percent subset of all NEOs found. Of course, known and unknown errors
in the NEO's orbital parameters can propagate out to significant
uncertainty in the position when predictions are done decades into the
future. Therefore, periodic observation of known objects, especially
those known to be in potentially hazardous orbits, must be done to
update the last known position and reduce the orbit errors.
Low Probability, High Consequence Events on Short Timelines
A central premise of the current survey effort is that in the
relatively short 10-year period, the search teams would be able to find
almost all asteroids of greater than 1 kilometer dimension that might
pose a threat of impact--many years to multiple decades before any such
event. It could perhaps even provide many centuries advanced notice,
since this level of event is thought to happen only once or twice in a
million years. Hypothetically, this would allow ample time to develop
the techniques and technologies that may be required to deflect or
mitigate a predicted disaster. But until the total population of these
objects is known, there is always a chance that an object bound for a
nearer term impact may be discovered, similar to the real-life scenario
which unfolded when Comet Shoemaker-Levy 9 was discovered in March 1993
inbound for a July 1994 impact on Jupiter.
The results of a recent study by a Science Definition Team
commissioned by NASA's Solar System Exploration Division show that it
is entirely appropriate that we search for the larger NEOs first
because, all factors considered, that is where the greatest risk for an
undetected asteroid on an impact trajectory lies, principally due to
the widespread devastation it would cause. It is orders of magnitude
above what smaller, sub-kilometer sized impactors would produce.
Completion of the current effort to find these large objects will do
much to reduce the uncertain risk of which we have now become aware.
But more frequent would be the discovery of a relatively small
asteroid on a potential impact trajectory with Earth, as this occurs
more often. Since the optical sensors used in the survey detect the
brightness of the object against the sky background, which can only be
approximately related to an asteroid's size based on assumed
reflectivity of light, the search systems are as capable of finding
smaller asteroids at closer range as larger objects much farther away.
They are designed to detect 1 kilometer sized asteroids at least 50
million kilometers distant but can also detect an asteroid a dozen
meters in size within the Moon's distance from Earth.
Operational experience with the current systems shows that for
every 1-kilometer or greater sized asteroid found, there are three to
four smaller sized asteroids also discovered. But the true ratio of
smaller asteroids, say 100-meter or larger objects to 1-kilometer or
larger objects, is thought to be closer to 100 to 1. Because of the
limitations of the search systems, the discovery of smaller asteroids
is in a significantly smaller volume about the Earth--an object one
tenth the size of another must be about hundred times closer to be seen
by the sensor, assuming equal reflectivity of their surfaces. If the
sensor can detect a 1 kilometer sized asteroid at 50 million
kilometers, it should theoretically also see a 100-meter asteroid at
500,000 kilometers.
However, at planetary relative orbital velocities, if the object is
on collision course with the Earth, it may cover even this distance in
less than one day. Thus the detection of a relatively small asteroid on
a collision trajectory with Earth could also come with a relatively
short reaction time. A 100 meter asteroid on direct collision with
Earth could do significant damage at the surface as this is estimated
to result in an approximately 50 megaton energy release at or perhaps
slightly above the surface. This would result in much loss of life if
the impact were in a populated area. It is therefore prudent that we
begin to put in place some contingency plans, such as an internal NASA
notification plan we are drafting, to deal with such a relatively
unlikely but extremely high-consequence event.
Again I thank you for the opportunity to appear and would be happy
to respond to any questions.
Senator Brownback. Thank you, gentlemen. I'm sorry that
Astronaut Nelson had to leave, but he submitted a series of
questions for the record that I would like to submit to you
gentlemen if you could get back to him in a timely time, I
would appreciate you doing that and I'll put that into the
record.
As you look at that, what are the chances of Earth being
hit by a substantial near earth target? I put forward the
chance is the same as being involved in an airliner crash. Is
that an accurate assessment? Do you think that's inaccurate? Or
where would you place it?
Dr. Johnson. From the studies that we've had, yes, that is
about the probability that is equivalent to about a million to
one--a million--or one in 500,000 somewhere in that range.
Senator Brownback. We're talking about a substantial size
object. What would you categorize as a substantial size object
to hit us in that chance range?
Dr. Johnson. Anything that's large enough to make it
through the atmosphere, anything larger than 80 meters or 200
feet in size.
Senator Brownback. I was looking at your chart and you're
saying that we're catching right about 700, that we've got
categorized and you've placed the estimated total at around
1,100, is that correct?
Dr. Johnson. Yes. That's based upon the distribution that
we've seen to date. We've actually lowered that estimate
through the course of the program by about 40 percent. We were
thinking the overall population was about 2,000, but what we've
seen so far, we think that population is somewhat less than the
original estimates and it's about 1,100 plus or minus 100 or
so, the large one kilometer size.
Senator Brownback. OK, these are the large one kilometer
size, right? And I thought you said there was 100 to one ratio
of the large to the small.
Dr. Johnson. Yes. We believe it's kind of a power law of
the numbers. As you get smaller, you know, a 100 to one ratio
of sizes----
Senator Brownback. You're not worried about their impact on
the Earth should they hit, the smaller ones. Is that correct?
Dr. Johnson. No. We are worried about it. Until you get
down to a size that Earth's atmosphere will dissipate, and
that's down to about 50 meters, you have to worry about damage
all the way to the surface of the Earth of anything that's
larger than about 50 meters.
Senator Brownback. OK. So what I hear you saying and you've
made substantial progress on the one kilometer or larger----
Dr. Johnson. Yes.
Senator Brownback.--ones, but we're still somewhere--you
think there's 1,100--you think there's 400 or so out there that
we have not found yet.
Dr. Johnson. Of the large ones, the ones that would do
worldwide devastation if they were to hit.
Senator Brownback. But you're at 100 to one times of others
than that could do substantial damage. Depending upon their
size and we don't have any idea where they are?
Dr. Johnson. Right. The original charter of the NEO
Observation Program was to find the large ones that would have
worldwide global consequences, but there's kind of a big
elephant out there. We're taking it a bite at a time.
Senator Brownback. So if you've got one that's half a
kilometer in size--let's say what kind of damage could that do?
Do you have any estimates of what that would be?
Dr. Johnson. Well, that devastation on the order of the
continent if it were to hit on land, pretty much the continent
that it hits would be affected. However, if it were to hit in
the ocean the ocean wave that would be caused, the tsunami,
would probably impact on both coasts. If it were hit in the
Middle Atlantic, both the Eastern seaboard of the United States
and the European seaboard would be affected by a large tsunami
of several meters, if not a 100 meters in height.
Senator Brownback. And we're not even tracking those yet?
Dr. Johnson. No, we're not tracking those yet. We are
finding them when they come close to Earth, come close enough
to Earth for our sensors to see it, but we know that there are
a lot more out there.
Senator Brownback. So when you say we're finding them when
they come close enough to Earth, how close and how much time do
we have between when we're finding them now and when they would
impact Earth?
Dr. Johnson. Well, as I said, so far those that we've
found, none of them are on impact trajectories. It all depends
on what the orbit is. It could be as rapidly as a day or two if
it's on a direct impact, or it could be decades or centuries
into the future until the orbits intersect.
Senator Brownback. Well, how much--you say we're finding
virtually all of them now that are coming in close to the
Earth. Did I understand or did I ask that correctly?
Dr. Johnson. We're finding virtually all the large ones
that come close enough.
Senator Brownback. Kilometer or larger?
Dr. Johnson. Yes.
Senator Brownback. What about those that are a half a
kilometer?
Dr. Johnson. I would give you no guarantee on what the
coverage is for those.
Senator Brownback. Of what we're finding at all?
Dr. Johnson. Right. What we're currently using are not
designed to find the small ones.
Senator Brownback. Are you comfortable with what we're
doing to date on this topic?
Dr. Johnson. As I said, it's a pretty big elephant and
you've got to take it a chunk at a time. I'm comfortable that
we are finding the large ones, but there is a hazard out there
still of the small ones.
Senator Brownback. It sounds like to me it's a large
hazard.
Dr. Johnson. Yes, it is.
Senator Brownback. And that we're not going through that
set at all? I mean, I understand that there are costs
associated with this and there's user resources that you've got
to do. I trying to assess what's the nature of the damage
potential?
Dr. Johnson. I think that's an accurate assessment. We are
finding the ones that would have global consequence if they
were to impact, but it's only serendipitously that we find the
smaller ones that could still do significant damage if they
were to impact.
Senator Brownback. What's the likelihood, the odds of us
being hit by a smaller object, say that's a half a kilometer in
size. Do we have any projections on the odds of being hit by
one of those in the next 100 years?
Dr. Johnson. In the next 100 years, it'd be very, very
small. Our estimates are that one 500 meters in size or so
would impact maybe once in 100,000 years. Something like that.
But we also believe that small ones, those on the order of 100
meters or so, impact once every few hundred to a thousand
years.
Senator Brownback. What kind of damage could those cause?
Dr. Johnson. The energy release from a 100 meter object
that's of average density would be about 50 megatons at the
surface, or slightly above the surface of the Earth. That's
larger than any nuclear weapon that we have.
Senator Brownback. So you're talking about a catastrophic
event wherever it occurs?
Dr. Johnson. The region that it impacts in, yes.
Senator Brownback. And what are the odds of that taking
place?
Dr. Johnson. Well, if on the average it happens once in
1,000 years that's your probability. Maybe once in 1,000 years.
Senator Brownback. Do we know when the last time one of
these hit the Earth was?
Dr. Johnson. Well, close to that size was the Tunguska
Event in 1908. That one was probably slightly smaller somewhere
in the 70 meter range. Something like that.
Senator Brownback. What was the impact of that event?
Dr. Johnson. Well, it actually exploded above the Earth's
surface probably at five to seven kilometers, but it still
devastated several hundred square kilometers of forest in
Siberia. The over pressure just blew the forest down and so if
it were to hit in a populated area it would be like a nuclear
device going off.
Senator Brownback. And this is an item of 100 meters in
size. Is that correct?
Dr. Johnson. That's correct.
Senator Brownback. And we don't have any idea of the
quantity of those that are out there that might be on some
orbital pattern toward the Earth?
Dr. Johnson. We believe they're in the hundreds of
thousands.
Senator Brownback. Hundreds to thousands?
Dr. Johnson. Hundreds of thousands.
Senator Brownback. Hundreds of thousands?
Dr. Johnson. Objects, yes.
Senator Brownback. And that those hit the Earth you say
once every how often?
Dr. Johnson. Once every thousand years.
Senator Brownback. Are we doing enough, Dr. Van Citters?
Dr. Van Citters. I think we could do a lot more. I think
that the study that NASA commissioned identified a very
reasonable set of parameters for future searches to carry on
from the one kilometer on down. We have a little more
technology development to do in terms of large area detectors
and so on, but the ideas that our community has presented to us
and to Lindley's program and so on and how you might continue
from here, I think are very credible.
I think there's a fair amount of trade study that we need
to do to look at how one might best carry out an extended
search whether it's in one instrument or a series of
instruments or if it's assigning parts of the search different
instruments and so on, but I think we could do a better job as
I indicated in things like the large Synoptic Survey Telescope
will quite naturally in the way they operate, catalogue tens of
thousands of these objects and provide the kind of completeness
that the expert committee has put in front of us.
Senator Brownback. These would be objects of much smaller
in size than the one kilometer?
Dr. Van Citters. Yes, this would be we--our sense of the
estimates, and these are of course just estimates, would be
that the surveys would be complete within--and it depends a
little bit on how you do them, but it's somewhere between 7
years and 20 years of operation, the surveys would be 90
percent complete down to 140 meters, which is of course a
substantial increase in our knowledge of the objects.
Senator Brownback. Let me ask you on the other side of
this, just the knowledge we could learn from these Near Earth
Objects. We've got a Scientific American article I think we'll
have some people testifying about, about using these as
tugboats for information of hooking probes on them, of what we
could gain from asteroids. Have either of you dealt with that
side of this equation or thought?
Dr. Johnson. Not too much. We do have studies going on what
we call, ``characterization studies,'' to find out what these
things are made of and that would help us to determine what
kind of resources are present on these and so theoretically if
there are resources there that are of benefit to either us on
Earth or in the exploration of the solar system, one could
think of mining operations going on on Near Earth Asteroids.
Senator Brownback. What about using--that we put probes on
to carry the probe out further into the galaxy.
Dr. Johnson. Ones that are on the right kinds of orbits
that do go out into the solar system, potentially that's an
idea.
Senator Brownback. Dr. Van Citters?
Dr. Van Citters. There's certainly a lot of interest in our
community and indeed in the research that we re funding,
because these objects are--as you indicated in your opening
remarks, left over from the formation of the solar system. And
so as we catalogue more of them, look at their orbits, where
they lie in the solar system, we get more spectroscopy to
characterize what they're made of, whether they're binary in
nature and so on, we have a very good probe of the very early
days of our own solar system. And add to our knowledge of basic
research in that area.
I should say too that there are, I think, we concentrate on
the astronomical aspects of this problem, there are other areas
that I think are very valid areas of research that would be
supported by other areas of the Foundation. And as we are
talking this afternoon, it ran through my mind that we have a
very active area, for instance, in mathematical sciences,
looking at the propagation of uncertainty in very complex
models.
And as we go through a study like the one that NASA
commissioned, the uncertainties in the prediction of what the
population of the asteroids is, what they're made of,
uncertainties in observation and so on, propagation of those
into an analysis of the risk at the end which we must then use
as a parameter to size systems and so on is a very active area
of mathematical research and something that would apply there.
Two, there's also the evaluation and the public perception
of risk. You characterized the risk, or tried to draw the
parallel between the risk of being struck by a large asteroid
and riding in an airplane. There are certainly different
perceptions among the populace of the risk of riding in an
airplane versus the risk of riding in a car in certain cases.
And I think the social sciences are extremely interested in how
that sort of risk analysis and risk perception plays out,
particularly in something like this, which is not something
within our--perhaps should be, but not something within
everyone s everyday thought process.
Senator Brownback. That's very interesting, gentlemen, and
I appreciate your work. How do you sleep at night, Dr. Johnson,
with this knowledge?
Dr. Johnson. I sleep very well at night. But it's not
something I worry about on a daily basis, but over time, it's
something we need to be concerned with.
Senator Brownback. That's what it looks like to me. It's
one of those things that we need to know the information for
safety purposes first. Protection is the reason the initial
Federal Government was created, was to provide for the security
of the people. And so you're always out there searching, what's
the security issue. And you could say, well, the odds are this
or that, but if something happens, it's significant. So you
really want to do everything you can.
And then on the flipside, it seems like there's some real
exploration and research that could be done if we knew more of
just what all was out there. There's a security issue here
which is of paramount concern. And then there's a curiosity/
research issue that seems like a significant benefit if we knew
a lot more of what all was out there.
Dr. Johnson. These objects are the building blocks of the
planets. They're the building blocks of Earth. So the more we
learn about these objects, the more that we will learn about
the Earth.
Senator Brownback. Gentlemen, thank you very much. I
appreciate your coming in and I hope everybody listening in
sleeps well tonight.
We have a second panel. Dr. Grant Stokes, Associate Head of
Aerospace Division at MIT in Massachusetts; Dr. Michael
Griffin, Head of the Space Department at Johns Hopkins
University, Applied Physics Lab; Mr. Rusty Schweickart,
Chairman of the Board, B612 Foundation; and Dr. Ed Lu,
President, and NASA Astronaut, of the B612 Foundation.
Gentlemen, I appreciate very much your coming and joining
in the panel and discussion today on Near Earth Objects. All of
your written statements will be placed into the record. Dr.
Stokes, we'll start with you and then we'll proceed down the
list as I announced it.
Welcome to the Committee. You might pull that microphone up
kind of close to you. It's fairly directional.
STATEMENT OF DR. GRANT H. STOKES, CHAIRMAN, NEAR EARTH OBJECT
SCIENCE DEFINITION TEAM, MIT LINCOLN LABORATORY
Dr. Stokes. All right. Thank you, Mr. Chairman, for the
opportunity to present to the Subcommittee information on NEOs
this afternoon. I'm here to represent the findings of the Near
Earth Object Science Definition Team, which I led recently for
NASA. And you've heard a little bit from the previous folks
about that.
The team was tasked to address a series of specific
questions intended to explore the technical possibilities of
searching for asteroids smaller than the current one kilometer
goal, and the efficacies of those searches. The study team
which was composed broadly of experts through the community
addressed the question by performing an exhaustive analysis
along two parallel paths.
First, the team established the current estimates of the
Near Earth Object population, estimated the collision rates
over time as functions of size, and then the damage expected
from those types of collisions.
Second, the team evaluated the technologies available to be
built into systems intended to search for asteroids, and
estimated their implementation costs and the effectiveness of
discovering and cataloguing potentially dangerous asteroids.
Combining that information from those two paths of analysis
systems and strategies on a cost/benefit basis. The cost of
investment in a search system balanced against the benefit of
providing awareness of potential short or long term threats.
The team specifically did not address issues related to
mitigation approaches in the highly unlikely event that we find
an object, a substantial object, on a collision course with
Earth, but the view was that if one was coming, we certainly
wanted to know.
The team estimated the annual nominal average risk
remaining in 2008, associated with an asteroid impact would be
approximately 300 casualties per year, that's worldwide, plus
the attendant property damage and destruction. That breaks down
to about 17 percent of that risk is attributed to smaller
objects doing regional damage for land impacts, about 53
percent of that is due to water impacts and the tsunamis that
ensue, and 30 percent of that risk is global climatic
disruption caused by large impacts. So those are the physical
objects left over, undiscovered by the Space Guard Survey in
2008.
Senator Brownback. You re saying 300 deaths per year?
Dr. Stokes. That's the average rate. Now, remember, that's
composed of events that happen over long intervals, but some of
them can be quite destructive. That average risk is composed of
devastating events that may occur only once over periods very
long compared to the life of an individual.
Senator Brownback. So if there's another like 1908 event
that occurs in 2030, you re calculators add----
Dr. Stokes. Right.
Senator Brownback. The large number of casualties of that
event, but you're calculating it over a period of time.
Dr. Stokes. Correct.
Senator Brownback. All right.
Dr. Stokes. In any particular year, the most likely number
of casualties due to an asteroid impact is zero. Now, in fact,
over periods of millions of years, there have been extinction
events like the dinosaurs 65 million years ago, which would
essentially cause the loss of civilization. And that is some
part of the average rate.
The 300 casualties per year that I mention is the left over
after we execute the current surveys. The actual yearly rate,
much of which has already been taken care of by the surveys,
would have been about 1,200 per year, if we started with no
information.
In addition, the team concluded that current technology
offers asteroid detection and cataloguing capabilities several
orders of magnitude better than presently operating systems. It
is resources rather than technology that is the current
limitation on NEO search performance. The team identified a
variety of search system examples which, when operated over
periods ranging from 7 to 20 years, would generate a catalogue.
That catalogue would contain hundreds of thousands of asteroids
and would be 90 percent complete for Near Earth Objects larger
than 140 meters. Construction and operation of these systems to
achieve the level of completeness is estimated by us to cost
somewhere between $296 million and $397 million, that's in
Fiscal Year 2003 dollars.
All of those systems----
Senator Brownback. Is that a total figure, or is that
over----
Dr. Stokes. That's a total figure including building the
system and operating it to that level of completeness, which
would take 7 to 20 years, depending on how aggressive--if one
is in a hurry, one should look at space-based systems. If one
wants to take longer, it can be done from the ground.
All of those systems that I mentioned have a favorable
cost/benefit pay back when measured in the unknown risk
eliminated by the dollars invested in the asteroid search
system. Based on those findings, the team recommended three
things for NASA.
First, we recommended that future goals related to search
for potential Earth-impacting objects should be stated
explicitly in terms if the statistical risk eliminated or
characterized, and should be firmly based in a cost/benefit
analysis.
Second, we recommend that NASA develop and operate a NEO
search program with the goal of discovering and cataloguing the
potentially hazardous population sufficient to eliminate 90
percent of the risk due to the sub-kilometer objects. That
would imply 90 percent completeness in the catalogue to the 140
meter level.
Third, to get things rolling, we suggest that NASA release
an announcement of opportunity, or an AO, to allow system
implementers to recommend a specific approach to satisfy the
goal stated in recommendation two, which we are sure is
technically possible.
Thank you and I would be happy to respond to questions.
[The prepared statement of Dr. Stokes follows:]
Prepared Statement of Dr. Grant H. Stokes, Chairman, Near-Earth Object
Science Definition Team, MIT Lincoln Laboratory
Thank you, Mr. Chairman, for the opportunity to present to the
subcommittee information on the subject of Near Earth Objects. In
recent years, there has been an increasing appreciation for the hazards
posed by near-Earth objects (NEOs), those asteroids and periodic comets
(both active and inactive) whose motions can bring them into the
Earth's neighborhood. In August of 2002, NASA chartered a Science
Definition Team to study the feasibility of extending the search for
near-Earth objects to smaller limiting diameters. The formation of the
team was motivated by the good progress being made toward achieving the
so-called Spaceguard goal of discovering 90 percent of all near-Earth
objects (NEOs) with diameters greater than 1 km by the end of 2008.
This raised the question of what, if anything should be done with
respect to the much more numerous smaller, but still potentially
dangerous, objects. The team was tasked with providing recommendations
to NASA as well as the answers to the following 7 specific questions:
1. What are the smallest objects for which the search should be
optimized?
2. Should comets be included in any way in the survey?
3. What is technically possible?
4. How would the expanded search be done?
5. What would it cost?
6. How long would the search take?
7. Is there a transition size above which one catalogs all the
objects, and below which the design is simply to provide
warning?
Team Membership
The Science Definition Team, which I lead, was composed of experts
in the fields of asteroid and comet search, including the Principal
Investigators of two major asteroid search efforts, experts in orbital
dynamics, NEO population estimation, ground-based and space-based
astronomical optical systems and the manager of the NASA NEO Program
Office. In addition, the Department of Defense (DOD) community provided
members to explore potential synergy with military technology or
applications. The Team members are listed in the following table along
with their institutions.
Dr. Grant H. Stokes (Chair) MIT Lincoln Laboratory
Dr. Donald K. Yeomans (Vice- Jet Propulsion Laboratory/Caltech
Chair)
Dr. William F. Bottke, Jr. Southwest Research Institute
Dr. Steven R. Chesley Jet Propulsion Laboratory/Caltech
Jenifer B. Evans MIT Lincoln Laboratory
Dr. Robert E. Gold Johns Hopkins University, Applied
Physics Laboratory
Dr. Alan W. Harris Space Science Institute
Dr. David Jewitt University of Hawaii
Col. T.S. Kelso USAF/AFSPC
Dr. Robert S. McMillan Spacewatch, University of Arizona
Dr. Timothy B. Spahr Smithsonian Astrophysical Observatory
Dr./Brig. Gen. S. Peter Worden USAF/SMC
Ex Officio Members
Dr. Thomas H. Morgan NASA Headquarters
Lt. Col. Lindley N. Johnson NASA Headquarters
(USAF, ret.)
Team Support
Don E. Avery NASA Langley Research Center
Sherry L. Pervan SAIC
Michael S. Copeland SAIC
Dr. Monica M. Doyle SAIC
Analysis Process
The Team approached the task using a cost/benefit methodology
whereby the following analysis processes were completed:
Population estimation--An estimate of the population of near-Earth
objects (NEOs), including their sizes, albedos and orbit distributions,
was generated using the best methods in the current literature. We
estimate a population of about 1100 near-Earth objects larger than 1
km, leading to an impact frequency of about one in half a million
years. To the lower limit of an object's atmospheric penetration
(between 50 and 100 m diameter), we estimate about half a million NEOs,
with an impact frequency of about one in a thousand years.
Collision hazard--The damage and casualties resulting from a
collision with members of the hazardous population were estimated,
including direct damage from land impact, as well as the amplification
of damage caused by tsunami and global effects. The capture cross-
section of the Earth was then used to estimate a collision rate and
thus a yearly average hazard from NEO collisions as a function of their
diameter. We find that damage from smaller land impacts below the
threshold for global climatic effects is peaked at sizes on the scale
of the Tunguska air blast event of 1908 (50-100 m diameter). For the
local damage due to ocean impacts (and the associated tsunami), the
damage reaches a maximum for impacts from objects at about 200 m in
diameter; smaller ones do not reach the surface at cosmic speed and
energy.
Search technology--Broad ranges of technology and search systems
were evaluated to determine their effectiveness when used to search
large areas of the sky for hazardous objects. These systems include
ground-based and space-based optical and infrared systems across the
currently credible range of optics and detector sizes. Telescope
apertures of 1, 2, 4, and 8 meters were considered for ground-based
search systems along with space-based telescopes of 0.5, 1, and 2 meter
apertures. Various geographic placements of ground-based systems were
studied, as were space-based telescopes in low-Earth orbit (LEO) and in
solar obits at the Lagrange point beyond Earth and at a point that
trailed the planet Venus.
Search simulation--A detailed simulation was conducted for each
candidate search system, and for combinations of search systems working
together, to determine the effectiveness of the various approaches in
cataloging members of the hazardous object population. The simulations
were accomplished by using a NEO survey simulator derived from a
heritage within the DOD, which takes into account a broad range of
``real-world'' effects that affect the productivity of search systems,
such as weather, sky brightness, zodiacal background, etc.
Search system cost--The cost of building and operating the search
systems described herein was estimated by a cost team from SAIC. The
cost team employed existing and accepted NASA models to develop the
costs for space-based systems. They developed the ground-based system
cost estimates by analogy with existing systems.
Cost/benefit analysis--The cost of constructing and operating
potential survey systems was compared with the benefit of reducing the
risk of an unanticipated object collision by generating a catalog of
potentially hazardous objects (PHOs). PHOs, a subset of the near-Earth
objects, closely approach Earth's orbit to within 0.05 AU (7.5 million
kilometers). PHO collisions capable of causing damage occur
infrequently, but the threat is large enough that, when averaged over
time, the anticipated yearly average of impact-produced damage is
significant. Thus, while developing a catalog of all the potentially
hazardous objects does not actually eliminate the hazard of impact, it
does provide a clear risk reduction benefit by providing awareness of
potential short-and long-term threats. The nominal yearly average
remaining, or residual, risk in 2008 associated with PHO impact is
estimated by the Team to be approximately 300 casualties worldwide,
plus the attendant property damage and destruction. About 17 percent of
the risk is attributed to regional damage from smaller land impacts, 53
percent to water impacts and the ensuing tsunamis, and 30 percent to
the risk of global climatic disruption caused by large impacts, i.e.,
the risk that is expected to remain after the completion of the current
Spaceguard effort in 2008. For land impacts and all impacts causing
global effects, the consequences are in terms of casualties, whereas
for sub-kilometer PHOs causing tsunamis, the ``casualties'' are a proxy
for property damage. According to the cost/benefit assessment done for
this report, the benefits associated with eliminating these risks
justify substantial investment in PHO search systems.
PHO Search Goals and Feasibility
The Team evaluated the capability and performance of a large number
of ground-based and space-based sensor systems in the context of the
cost/benefit analysis. Based on this analysis, the Team recommends that
the next generation search system be constructed to eliminate 90
percent of the risk posed by collisions with sub-kilometer diameter
PHOs. Such a system would also eliminate essentially all of the global
risk remaining after the Spaceguard efforts are complete in 2008. The
implementation of this recommendation will result in a substantial
reduction in risk to a total of less than 30 casualties per year plus
attendant property damage and destruction. A number of search system
approaches identified by the Team could be employed to reach this
recommended goal, all of which have highly favorable cost/benefit
characteristics. The final choice of sensors will depend on factors
such as the time allotted to accomplish the search and the available
investment.
Answers to Questions Stated in Team Charter
What are the smallest objects for which the search should be
optimized? The Team recommends that the search system be constructed to
produce a catalog that is 90 percent complete for potentially hazardous
objects (PHOs) larger than 140 meters.
Should comets be included in any way in the survey? The Team's
analysis indicates that the frequency with which long-period comets (of
any size) closely approach the Earth is roughly one-hundredth the
frequency with which asteroids closely approach the Earth and that the
fraction of the total risk represented by comets is approximately 1
percent. The relatively small risk fraction, combined with the
difficulty of generating a catalog of comets, leads the Team to the
conclusion that, at least for the next generation of NEO surveys, the
limited resources available for near-Earth object searches would be
better spent on finding and cataloging Earth-threatening near-Earth
asteroids and short-period comets. A NEO search system would naturally
provide an advance warning of at least months for most threatening
long-period comets.
What is technically possible? Current technology offers asteroid
detection and cataloging capabilities several orders of magnitude
better than the presently operating systems. NEO search performance is
generally not driven by technology, but rather resources. This report
outlines a variety of search system examples, spanning a factor of
about 100 in search discovery rate, all of which are possible using
current technology. Some of these systems, when operated over a period
of 7-20 years, would generate a catalog that is 90 percent complete for
NEOs larger than 140 meters.
How would the expanded search be done? From a cost/benefit point-
of-view, there are a number of attractive options for executing an
expanded search that would vastly reduce the risk posed by potentially
hazardous object impacts. The Team identified a series of specific
ground-based, space-based and mixed ground-and space-based systems that
could accomplish the next generation search. The choice of specific
systems will depend on the time allowed for the search and the
resources available.
What would it cost? For a search period no longer than 20 years,
the Team identified several systems that would eliminate, at varying
rates, 90 percent of the risk for sub-kilometer NEOs, with costs
ranging between $236 million and $397 million. All of these systems
have risk reduction benefits which greatly exceed the costs of system
acquisition and operation.
How long would the search take? A period of 7-20 years is
sufficient to generate a catalog 90 percent complete to 140-meter
diameter, which will eliminate 90 percent of the risk for sub-kilometer
NEOs. The specific interval depends on the choice of search technology
and the investment allocated, as shown in the figure below.
The cost of various space-based and ground-based search systems are
plotted against the number of search years required to reduce by 90
percent the sub-global risk from impacts by sub-kilometer sized
objects.
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
The cost of various space-based and ground-based search systems are
plotted against the number of search years required to reduce by 90
percent the sub-global risk from impacts by sub-kilometer objects.
Is there a transition size above which one catalogs all the
objects, and below which the design is simply to provide warning? The
Team concluded that, given sufficient time and resources, a search
system could be constructed to completely catalog hazardous objects
with sizes down to the limit where air blasts would be expected (about
50 meters in diameter). Below this limit, there is relatively little
direct damage caused by the object. Over the 7-20 year interval
(starting in 2008) during which the next generation search would be
undertaken, the Team suggests that cataloging is the preferred approach
down to approximately the 140-meter diameter level and that the search
systems would naturally provide an impact warning of 60-90 percent for
objects as small as those capable of producing significant air blasts.
Science Definition Team Recommendations
The Team makes three specific recommendations to NASA as a result
of the analysis effort:
Recommendation 1--Future goals related to searching for potential
Earth-impacting objects should be stated explicitly in terms of the
statistical risk eliminated (or characterized) and should be firmly
based on cost/benefit analyses.
This recommendation recognizes that searching for potential Earth
impacting objects is of interest primarily to eliminate the statistical
risk associated with the hazard of impacts. The ``average'' rate of
destruction due to impacts is large enough to be of great concern;
however, the event rate is low. Thus, a search to determine if there
are potentially hazardous objects (PHOs) likely to impact the Earth
within the next few hundred years is prudent. Such a search should be
executed in a way that eliminates the maximum amount of statistical
risk per dollar of investment.
Recommendation 2--Develop and operate a NEO search program with the
goal of discovering and cataloging the potentially hazardous population
sufficiently well to eliminate 90 percent of the risk due to sub-
kilometer objects.
The above goal is sufficient to reduce the average casualty rate
from about 300 per year to less than 30 per year. Any such search would
find essentially all of the larger objects remaining undiscovered after
2008, thus eliminating the global risk from these larger objects. Over
a period of 7-20 years, there are a number of system approaches that
are capable of meeting this search metric with quite good cost/benefit
ratios.
Recommendation 3--Release a NASA Announcement of Opportunity (AO)
to allow system implementers to recommend a specific approach to
satisfy the goal stated in Recommendation 2.
Based upon our analysis, the Team is convinced that there are a
number of credible, current technology/system approaches that can
satisfy the goal stated in Recommendation 2. The various approaches
will have different characteristics with respect to the expense and
time required to meet the goal. The Team relied on engineering judgment
and system simulations to assess the expected capabilities of the
various systems and approaches considered. While the Team considers the
analysis results to be well grounded by current operational experience,
and thus, a reasonable estimate of expected performance, the Team did
not conduct analysis at the detailed system design level for any of the
systems considered. The next natural step in the process of considering
a follow-on to the current Spaceguard program would be to issue a NASA
Announcement of Opportunity (AO) as a vehicle for collecting search
system estimates of cost, schedule and the most effective approaches
for satisfying the recommended goal. The AO should be specific with
respect to NASA's position on the trade between cost and time to
completion of the goal.
The complete Science Definition Team Report may be accessed online
at: http://neo.jpl.nasa.gov/neo/neoreport030825.pdf
I thank you for the opportunity to appear and would be happy to
respond to any questions.
Senator Brownback. Thank you very much. Dr. Griffin.
STATEMENT OF MICHAEL D. GRIFFIN, HEAD OF THE SPACE DEPARTMENT,
APPLIED PHYSICS LAB, JOHNS HOPKINS
UNIVERSITY
Dr. Griffin. Thank you, Senator Brownback. I am here this
afternoon, representing the Johns Hopkins Applied Physics
Laboratory, which is so far the only laboratory which has
carried out the mission of visiting a Near Earth Object with a
robotic spacecraft.
Thank you for providing me with this opportunity to comment
on the greatest natural threat to the long-term survivability
of mankind, which is an asteroid impact with the Earth.
Throughout its history, Earth has been continuously
bombarded by objects ranging in size from dust particles to
asteroids or comets greater than 10 kilometers in diameter.
You've heard that although the probability of the Earth being
hit by a large object in this century is low, the effects of
such an impact are so catastrophic that it is essential to
prepare a defense against such an occurrence.
The first step in that defense is a system to identify and
catalogue all potential impacters above the threshold of
significant damage, approximately 100 meters in diameter.
Later, the remainder of a comprehensive Earth protection system
could be assembled so that it would be ready to deflect a
potential impacter shortly after it is identified.
NEOs also represent a tremendous opportunity in the context
of the President's exploration initiative. They are potential
suppliers of resources for future manned space exploration, but
in order to use these resources a much more detailed knowledge
of their composition and physical characteristics will be
required before the technologies to produce fuels or
construction materials from Near Earth Objects can be
developed.
In 1998, NASA embraced the goal, as you've heard, of
finding and cataloguing within 10 years 90 percent of all the
Near Earth Objects with diameters greater than 1 kilometer. It
is estimated that on the order of a thousand such objects
exist. Population counts show, however, that there could likely
be 150,000 Near Earth Objects larger than 100 meters, the
threshold of significant damage on Earth.
For reference, the Tunguska Event in Siberia in 1908
destroyed an area 50 kilometers in diameter and is believed to
have been caused by an impacter on the order of 50 meters in
diameter.
Again, you have already heard that the average--at the
average speed of these objects, the energy released by the
impact of 100 meter Near Earth Object is about equivalent to
that of a 50 megaton bomb.
The frequency of impacts over the last century can be
estimated by noting the Tunguska Event in 1908, the Sikhote-
Alin Event in Siberia about 270 miles northeast of Vladivostok
in February 1947, and the several recently identified objects
that have had very near misses with the Earth.
All this evidence confirms that impacts with the ability to
wipe out a large metropolitan area can be expected within the
next 100 years. It is also worth noting that within living--or
at least recent memory, there is a 12 mile wide crater under
the sea floor near the island of New Zealand, the impact of
which lives on in Maori legends in the area. The impact is
estimated to have occurred in the 1700s. These are not terribly
infrequent events on human time scales.
It is estimated that a 30 year advance warning would be
required to have a reasonable assurance of deflecting a Near
Earth Object from a collision with the Earth. If a future
impacter were identified today, the time to explore the
characteristics of the object, to develop a deflection system,
deliver it to the NEO, and apply the deflection early enough to
prevent an impact requires about a three decade lead time from
the initial discovery.
An overall Earth protection system must have three
components. A search system is needed to identify any potential
impacters, a series of detailed investigation missions are
needed to understand the structure, composition, rotational
state, and other physical properties of the impacter. And
finally, deflection technologies are needed to change the speed
of the object so that it will not impact Earth.
At the current rate of discovery, the group of
observatories that are finding and cataloguing Near Earth
Objects will come close to achieving their goal of identifying
90 percent of the greater than 1 kilometer diameter objects by
2008. More than 50 percent of the population has already been
discovered.
The very large number of undiscovered, small to modest
sized objects, the greater than 100 meters that I spoke of,
represents the greatest remaining threat to regional safety not
currently being addressed.
A NASA Near Earth Object Science Definition Team recently
examined the requirements for extending this search to smaller
diameters and showed that a system to accomplish the discovery
and cataloguing of 90 percent of these objects within 10 years
could be accomplished with a single discovery class spacecraft
in a heliocentric orbit, about seven-tenths of an AU out from
the sun, or about at the orbit of Venus, relative to the sun.
This modestly priced system could be constructed and launched
in 4 to 5 years.
My time is running out, and so I will conclude that in
summary, the threat to life on Earth from Near Earth Objects is
real, even though the likelihood of a severe impact during the
next few years is low. The space exploitation opportunities of
these objects are equally real. The most important thing needed
at this time is an improved search system for smaller objects.
Recent studies have shown that a search spacecraft can
catalogue 90 percent of the remaining objects within 10 years
and can be launched within the next 4 or 5 years.
Thank you very much, and I'm ready to take any questions
you may have.
[The prepared statement of Dr. Griffin follows:]
Prepared Statement of Michael D. Griffin, Head of the Space Department,
Applied Physics Lab, Johns Hopkins University
Mister Chairman and members of the subcommittee, thank you for
giving me this opportunity to comment on the greatest natural threat to
the long-term survivability of mankind, an asteroid impact with the
Earth. Throughout its history, the Earth has continuously been
bombarded by objects ranging in size from dust particles to comets or
asteroids greater than 10 km in diameter. Although the probability of
the Earth being hit by a large object in this century is low, the
effects of an impact are so catastrophic that it is essential to
prepare a defense against such an occurrence. The first step in that
defense is a system to identify and catalog all potential impactors
above the threshold of significant damage, approximately 100 meters in
diameter. Later, the remainder of a comprehensive Earth-protection
system could be assembled so that it would be ready to deflect a
potential impactor shortly after it is identified.
In 1998, NASA embraced the goal of finding and cataloging, within
10 years, 90 percent of all near-Earth objects (NEOs) with diameters
greater than 1 km. Impacts by objects of this size and larger could
result in worldwide damage, and the possible elimination of the human
race. The current system is not sufficient to catalog the population of
smaller NEOs. While there are thought to be nearly a thousand objects
with diameters greater than 1 km, there are a great many smaller NEOs
that could devastate a region or local area. The exact NEO size
distribution is not known; however a good current estimate is that
there are more than 5 times as many objects with diameters greater than
1/2 km than there are with diameters greater than 1 km. This
multiplication of numbers for smaller diameters continues for all sizes
at least down to those just large enough to make it through the
atmosphere. Thus, if there are about 700 NEOs of 1 km or greater, there
are more than 150,000 NEOs with diameters greater than 100 m. The
Tunguska event in Siberia in 1908 destroyed an area 50 km in diameter
and is believed to have been caused by an impactor less than 50 m in
diameter.
The average speed of objects colliding with Earth is about 20 km/s
(about 45,000 miles per hour). At these speeds the energy of impact is
44 times the explosive power of the same mass of TNT. Thus, the energy
released by the impact of a 100 m object is about equivalent to a 50
megaton bomb. The impacts at Tunguska in 1908, Sikhote-Alin (about 270
miles northeast of Vladivostok) in February 1947, and the recently
identified objects that have had near misses with Earth, all show us
that impacts with the ability to wipe a large metropolitan area can be
expected during the next 100 years.
A great deal has been learned about the nature of the threat in the
last decade. It is vital to understand the characteristics of NEOs to
know how to defend against a potential impactor. An improved
theoretical understanding of the population of NEOs has clarified their
evolution through interactions with the planets of our solar system. It
has helped us understand their numbers and their distribution in the
different classes of orbits. On the practical side, the progress of
several space missions has greatly improved our understanding of the
physical and chemical characteristics of these objects. A great deal
still needs to be done since only a handful of these objects have been
observed from sufficiently close distances to see their surface
structure, and only one asteroid has been orbited. The Near Earth
Asteroid Rendezvous (NEAR) mission orbited and landed on 433-Eros and
was able to get the first estimates of the internal structure and
composition of a NEO. However, there is still a great deal more that
will have to be known about an object if it becomes necessary to
deflect it from a collision course with Earth.
Opportunities
In addition to the threat that NEOs represent, they are also
potential suppliers of resources for future manned space exploration.
In order to use these resources, a much more detailed knowledge of
their composition and physical characteristics will be required before
the technologies to produce fuels or construction materials from NEOs
can be developed.
Current and Future Technologies for Earth Protection
It is estimated that a 30-year advance warning would be required to
have a reasonable assurance of deflecting a NEO from a collision with
Earth. Thus, if a future impactor were identified today, the time to
explore the characteristics of the NEO, develop a deflection system,
deliver it to the NEO, and apply the deflection early enough to prevent
an impact, requires about a 3-decade lead time.
The deflection technologies available today, which are chemical
rockets and nuclear weapons, both have limited abilities to slow down
or speed up an asteroid. A 100 m object has a mass of the order of 1
million tons, and a 1 km object has a mass of the order of 1 billion
tons. To prevent an object from colliding with Earth, it must be sped
up or slowed down by about 7 cm/s (about \1/6\ of an mile per hour)
divided by the number of years in advance that the change is applied.
The fuel that can be contained in a medium-sized scientific spacecraft
could successfully deflect a 100 m body if it were pushed about 15
years in advance. The Space Shuttle's main engines and the fuel
contained in the large external tank could successfully deflect a 1 km
diameter object if it were applied about 20 years in advance. Nuclear
weapons carry much greater impulse for their mass. However, they
deliver that impulse so quickly that they are more likely to break up
the body than to deflect it. Because NEOs are in their own orbits
around the Sun, the pieces of a disrupted object will tend to come
together one half of an orbital period later. Therefore, the successful
use of nuclear weapons for deflection will require the development of
techniques for slowing the delivery of the impulse to the NEO and will
probably also require many small weapons to be used to deflect a single
NEO.
The orbital mechanics required to approach a potential impactor
also require it to be identified early. It may take 5 years or more for
any deflector mission to rendezvous with a NEO in an arbitrary Earth-
crossing orbit.
What Remains to be Done
An overall Earth protection system must have three components.
First, a search system is needed to identify any potential NEO
impactors. Second, a series of detailed investigation missions are
needed to understand the structure, composition, rotational state, and
other physical properties of potential impactors. And finally,
deflection technologies are needed to change the speed of a NEO to
ensure that it will not impact Earth.
Search systems
The United States and other countries around the world have
concentrated on the first part of the Earth-protection system. At the
current rate of discovery, the group of observatories that are finding
and cataloging NEOs will come close to achieving their goal of
identifying 90 percent of the greater than 1-km diameter NEO population
by 2008. More than 50 percent of the expected population has already
been discovered and discoveries continue to be made each month. While
this effort will retire most of the risk of a global catastrophe, the
size distribution of NEOs shows us that there are a great many more
small objects than larger ones. Their numbers increase by a factor of
about 220 for a diameter that is reduced by a factor of 10. This very
large number of small-to-modest sized objects represents the greatest
remaining threat to regional safety that is not being addressed. The
equipment used by current NEO surveys is sized to find the largest
objects. Some sub-kilometer objects are found serendipitously; however,
these telescope systems are not optimized to find the smaller objects.
A NASA NEO Science Definition Team recently examined the
requirements for extending the NEO search to smaller diameters and
showed that a system to accomplish the discovery and cataloging of 90
percent of all NEO greater than 100 m diameter within 10 years could be
accomplished with a single Discovery-class spacecraft in a heliocentric
orbit at about 0.7 AU. This modestly priced system (the Discovery class
is about $300 million full mission cost) could be constructed and put
on-station in four to five years.
Detailed Examination of NEOs
Several space missions that are contributing to the detailed
investigations of NEOs and comets have been launched and others are
currently in development. As stated above, the NEAR mission provided
the first detailed information on the mass, shape, structure, and
composition of an asteroid. However, we know from ground-based
spectroscopic data that there is a great deal of variability among
these objects.
The Giotto and Deep Space 1 missions took close images of comets
Halley and Borelli. The Stardust mission will be returning with dust
particles from comet Wild 2 in January of 2006. The Deep Impact mission
will create a crater in comet Tempel 1 to learn about the internal
composition of comets. And the DAWN mission will examine the
composition of asteroids 1 Ceres and 4 Vesta, two of the largest
planetoids in the solar system. These missions are making steady
progress in our understanding of the formation of the solar system and
the characteristics of the small bodies within it. Continuation of this
series of investigations is vital to our future ability to deal with
the threat and opportunities of NEOs.
Deflection Technologies
While there has been a great deal of theoretical examination of
deflection techniques, no practical systems exist at this time. As the
search systems and detailed examination missions progress, it is
important to continue the development of deflection system technologies
so that a full Earth-protection system could be deployed rapidly if a
future impactor is discovered by the search systems.
Summary
The threat to life on Earth from NEOs is real even though the
likelihood of a severe impact during the next few years is low. The
most important thing that is needed in order to deal with this risk is
an improved search system. Recent studies have shown that a search
spacecraft that can catalog 90 percent of the remaining NEOs larger
than 100 m in diameter over 10 years of operation can be launched
within 4 or 5 years at the cost of a NASA Discovery-class mission. In
addition, the pace of mission developments for detailed examination of
small solar system bodies should continue undiminished. This is clearly
summarized by the cartoon below, originally published in New Yorker
magazine in 1998.
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Witness Biography
Michael D. Griffin is Space Department Head, Johns Hopkins
University Applied Physics Laboratory.
Prior to joining APL, Mike served in a variety of executive
positions with industry, including: President and Chief Operating
Officer of In-Q-Tel, Inc., CEO of the Magellan Systems Division of
Orbital Sciences Corporation, General Manager of Orbital's Space
Systems Group, and Executive Vice President and Chief Technical Officer
at Orbital. He has previously served as both the Chief Engineer and the
Associate Administrator for Exploration at NASA, and as the Deputy for
Technology of the Strategic Defense Initiative Organization.
Before joining SDIO in an executive capacity, Mike played a key
role in conceiving and directing several ``first of a kind'' space
tests in support of strategic defense research, development, and flight
testing. These included the first space-to-space intercept of a
ballistic missile in powered flight, the first broad-spectrum
spaceborne reconnaissance of targets and decoys in midcourse flight,
and the first space-to-ground reconnaissance of ballistic missiles
during the boost phase.
Mike holds seven degrees in the fields of Physics, Electrical
Engineering, Aerospace Engineering, Civil Engineering, and Business
Administration, has been an Adjunct Professor at the George Washington
University, the Johns Hopkins University, and the University of
Maryland, and is the author of over two dozen technical papers and the
textbook Space Vehicle Design. He is a recipient of the NASA
Exceptional Achievement Medal, the AIAA Space Systems Medal, the DOD
Distinguished Public Service Medal, and is a Fellow of the AIAA and the
AAS. Mike is a Registered Professional Engineer in Maryland and
California, and a Certified Flight Instructor with instrument and
multiengine ratings.
Senator Brownback. Dr. Griffin, just a couple real quick.
That's the best way it's felt within the scientific community
to do this, is to put a space-based observatory of sorts in an
orbit out and around, to be able to categorize----
Dr. Griffin. I wouldn't--that is one way. I wouldn't want
to go so far as to say that the scientific community would
regard it as the best way. The task can equally well be
accomplished with a series or a set of ground-based telescopes
spread as widely as possible on the Earth.
And indeed, I believe NASA is open to both possibilities
through the announcement of opportunity to which the previous
witness alluded. So either ground-based--either several ground-
based observatories or a single space-based observatory could
probably accomplish the same job.
Senator Brownback. And what about the exploration
opportunity and the research opportunity. What do you see as
the biggest things we can learn from NEOs?
Dr. Griffin. Well, I am an engineer by profession, and not
a scientist. So my primary interest in Near Earth Objects would
be for the exploration, exploitation, and development of a
spacefaring infrastructure.
Many Near Earth Objects will be found to be of the class of
so-called carbonaceous chondrites from which volatile material,
to include water, can likely be extracted. A small fraction of
them, 1 or 2 percent, a few percent, will have heavy useful
metals. Others will be merely rock and stone.
But all of those together can provide construction
materials, possibly fuel supplies. And those materials do not
have to be lifted out of the gravity well of this planet or any
other.
This is a pursuit which should occupy us in the coming
decades of space exploration. It will not be the first thing
that we do, but it should be allowed to be the last thing we
think of.
Senator Brownback. Mr. Schweickart. Good to have you here.
Mr. Schweickart. Thank you, sir. With your permission, I'd
like to defer to Mr. Lu first, sir. Sequences would be better
that way.
The Chairman. That'll be just fine. Dr. Lu.
STATEMENT OF DR. EDWARD LU, NASA ASTRONAUT AND PRESIDENT, B612
FOUNDATION
Dr. Lu. Thank you for the opportunity to discuss a bold new
proposal to demonstrate--actually demonstrate altering the
orbit of an asteroid. I wanted to talk today about sort of a
different aspect than what you've been hearing about which is
searching for asteroids and that's the necessary first step.
But once you find asteroids, particularly if you find one on a
collision course, the question is, ``What do you do? Or what
can we do?''
I represent the B612 Foundation and we're a group of
astronomers, engineers and astronauts concerned about the issue
of asteroid impacts. Recent developments have now given us the
potential to defend the Earth against these natural disasters
and I'll talk about that.
To develop this capability, we have proposed a spacecraft
mission to significantly alter the orbit of an asteroid in a
controlled manner by 2015 and we think it's important that
there be an actual demonstration and I'll talk about why that
is later.
First off. Why would you want to move an asteroid? I think
we've been hearing a little bit about that and I want to put
some of these odds that you've been hearing about in a
different way; their equivalent numbers. You've been asking
about what are the odds of getting hit by an asteroid? Well,
rather than saying once per thousand years or so--another way
to say that is that during your lifetime, during my lifetime,
everyone in this room, there's a 10 percent chance that there
will be a 60 meter asteroid that impacts the Earth with an
energy of a 10 megatons and that's about 700 simultaneous
Hiroshima sized bombs going off. It's 10 percent.
It's kind of like a bad lottery but--in that most days
are--nothing's going to happen, but occasionally you get a bad
day and there's a one in 50,000 chance that your death, my
death, everyone in this room along with most of humanity and
human civilization is going to end all on the same day with the
impact with a greater than kilometer sized asteroid; one to
50,000 is pretty small, but that would be the end of it.
We think that we now have the potential to change these
odds and what we propose is again actually trying a
demonstration mission to deflect an asteroid because there's a
lot of unknown surrounding this. You've been hearing about that
but the surest way to actually attack any of these unknowns is
to try something.
The first time that you attempt to deflect an asteroid
shouldn't be on the real day because there's going to be many
surprises in store. The first few missions may not work at all.
You want to learn those ahead of time before you actually have
to use such a system.
So why do we suggest by 2015? Well, again, the time to
test, learn and experiment is now because we have just recently
developed or are developing new advances in space nuclear power
and high efficiency propulsion that we think makes it possible.
2015 is challenging, but we think doable and having a clear
goal, a clear date will, we think, serve to focus the
development efforts.
So how big of an asteroid are we proposing to move? The
demonstration asteroid that you try this test mission on ought
to be large enough to represent a real risk and also what you
test should be applicable to larger size asteroids because you
want to start out fairly small, but you want what you learn to
be useful through larger asteroids.
So we're suggesting an asteroid of about 200 meters and a
200 meter asteroid if it impacts, would be about a 600 megaton
explosion and as we heard that if that lands in an ocean that
will likely destroy most coastal cities in that ocean. So
that's large enough to be a threat.
Asteroids of about 150 meters across or larger are thought
to be not single pieces, but rather conglomerations or loosely
held together groups called, ``rubble piles,'' and so if you
pick something that's a rubble pile, what you learn will be
applicable to larger size asteroids. So again, we're picking
something that's of moderate risk--of major risk but is doable
we think. Large enough to be doable.
So what do we mean by significantly alter it? It turns out
that you don't really need to give an asteroid very much of a
push to prevent a collision. If you have several decades of
warning which we expect if these proposed searches are carried
out, then all you really need to do is if you have several
decades of notice is to give an asteroid a small impulse. Maybe
about a centimeter a second. That's about 1/50th of a mile an
hour.
Even though the typical asteroid moves around the sun at
about 70,000 miles per hour, making it 70,000.002 is enough to
prevent a collision if you've got a decade or so of warning,
but even though that's a small change in velocity, that's still
pretty hard because even a 200 meter asteroid weights about 10
million tons.
So why do you need to move it in a controlled manner? Well,
if you don't make it a highly controlled thing, you risk making
the problem worse. You've seen Armageddon, or movies like that
where they talk about blowing up an asteroid with a nuclear
weapon. Well, you stand as much of a chance of making your
problem worse as making it better and you split the asteroid up
and what you've done then is turned this rifle bullet heading
at you into a shotgun blast and now your life has just gotten
worse.
Furthermore, you won't really quite know where you're going
to end up pushing the asteroid and that's not a good situation
if you're trying to avert a catastrophe. So we are suggesting
doing this in a controlled slow manner which also has the
advantage that you can use the same technology for commercial
reasons--commercial and exploration reasons which has also been
brought up. So how can you do this?
Well, first off, conventional rockets like we use today,
like I've launched on the Space Shuttle and Rusty's flown on
the Saturn Five, those use chemical propellants. Well, chemical
propellants basically don't have the umph to move objects of
this size. So what we are proposing to use is a nuclear powered
spacecraft using high energy propulsion such as an ion or
plasma engine. Those are currently in development at NASA today
as part of the Prometheus Project.
In fact, the thrust and power requirements that we've
discussed for moving a 200 meter asteroid are about the same as
the Jupiter Icing Moons Orbiter and that's a spacecraft that's
currently planned for launch in around 2012. So we're
suggesting that you could use similar hardware to do this
demonstration mission.
So this spacecraft would fly to an asteroid rendezvous and
land on and attach to this small asteroid and push on it and by
continuously thrusting for some period of months you could
slowly, slowly, slowly alter the velocity by a fraction of a
centimeter per second and we could measure that from the Earth
so we could verify that it's worked and then we say, well, what
can we learn from this?
Well, remember that this is not really a planetary
protection system, but it's a first attempt to learn more about
the mechanics of asteroid deflection because like I said, a lot
of technical complications and unknowns about asteroids
themselves, their structure, what they're made of, but the way
to make progress I think is to build, fly and test.
You need to go there to find out the questions that you
don't even know yet. And besides the benefit of actually being
able to demonstrate that you can do this there's a lot of
interesting scientific questions you can answer at the same
time. Again, the best way to learn about asteroids is to go
there.
So how does this fit into NASA's New Exploration
Initiative?
Well, in the near term, we think this mission would be an
ideal way to flight test the nuclear propulsion systems already
under development as part of ``Project Prometheus.'' It could
also serve as a precursor to a crewed mission, meaning with
people on board to go visit an asteroid.
These missions have been proposed as an intermediate step
to test your spacecraft systems for eventual longer term
missions to Mars. I would personally love to go on one of those
missions.
In the longer term, the ability to land on and manipulate
asteroids is an enabling technology for extending human and
robotic presence throughout the solar system.
If we're to truly open up the solar system, this mission we
feel is a good way to start. It's likely that someday we're
going to use asteroids for fuel, building materials or simply
space habitats, mining, people are going to earn money off
this. And the B612 Mission would mark a fundamental change in
spacecraft in that it would actually alter in a measurable way
an astronomical object rather than simply observing it.
We can become active participants in the cosmos versus just
being interested observers. Human beings need to eventually
take charge of our own destiny in this manner or we will some
day go the way of the dinosaurs when the next great asteroid
impact occurs. Thank you.
[The prepared statement of Dr. Lu follows:]
Prepared Statement of Dr. Edward Lu, NASA Astronaut and President,
B612 Foundation
Thank you for the opportunity today to discuss a bold new proposal
to demonstrate altering the orbit of an asteroid. I represent the B612
foundation, a group of astronomers, engineers, and astronauts,
concerned about the issue of asteroid impacts. Recent developments have
now given us the potential to defend the Earth against these natural
disasters. To develop this capability we have proposed a spacecraft
mission to significantly alter the orbit of an asteroid in a controlled
manner by 2015.
Why move an asteroid? There is a 10 percent chance that during our
lifetimes there will be a 60 meter asteroid that impacts Earth with
energy 10 megatons (roughly equivalent to 700 simultaneous Hiroshima
sized bombs). There is even a very remote one in 50,000 chance that you
and I and everyone we know, along with most of humanity and human
civilization, will perish together with the impact of a much larger
kilometer or more sized asteroid. We now have the potential to change
these odds.
There are many unknowns surrounding how to go about deflecting an
asteroid, but the surest way to learn about both asteroids themselves
as well as the mechanics of moving them is to actually try a
demonstration mission. The first attempt to deflect an asteroid should
not be when it counts for real, because there are no doubt many
surprises in store as we learn how to manipulate asteroids.
Why by 2015? The time to test, learn, and experiment is now. A
number of recent developments in space nuclear power and high
efficiency propulsion have made this goal feasible. The goal of 2015 is
challenging, but doable, and will serve to focus the development
efforts.
How big of an asteroid are we proposing to move? The demonstration
asteroid should be large enough to represent a real risk, and the
technology used should be scaleable in the future to larger asteroids.
We are suggesting picking an asteroid of about 200 meters. A 200 meter
asteroid is capable of penetrating the atmosphere and striking the
ground with an energy of 600 megatons. Should it land in the ocean (as
is likely), it will create an enormous tsunami that could destroy
coastal cities. Asteroids of about 150 meters and larger are thought to
be comprised of loose conglomerations of pieces, or rubble piles, while
smaller asteroids are often single large rocks. The techniques we test
on a 200 meter asteroid should therefore also be applicable to larger
asteroids.
What does ``significantly alter the orbit'' mean? If proposed
asteroid searches are enacted, we expect to have decades or more of
warning before an impact. Given this amount of warning, to prevent an
impact only requires that the orbital velocity of an asteroid be
altered by a small amount, less than of order 1 cm/sec, or about .02
MPH. This is a tiny velocity increment, considering that the orbital
speeds of asteroids are of order 70,000 MPH. However, this is still a
very difficult task since the mass of a 200 meter asteroid is of order
10 million tons.
Why does the asteroid need to be moved in a ``controlled manner''?
If the asteroid is not deflected in a controlled manner, we risk simply
making the problem worse. Nuclear explosives for example risk breaking
up the asteroid into pieces, thus turning a speeding bullet into a
shotgun blast of smaller but still possibly deadly fragments.
Explosions also have the drawback that we cannot accurately predict the
resultant velocity of the asteroid--not a good situation when trying to
avert a catastrophe. Conversely, moving an asteroid in a controlled
fashion also opens up the possibility of using the same technology to
manipulate other asteroids for the purposes of resource utilization.
How can this be accomplished? This mission is well beyond the
capability of conventional chemically powered spacecraft. We are
proposing a nuclear powered spacecraft using high efficiency propulsion
(ion or plasma engines). Such propulsion packages are currently already
under development at NASA as part of the Prometheus Project. In fact,
the power and thrust requirements are very similar to the Jupiter Icy
Moons Orbiter spacecraft, currently planned for launch around 2012. The
B612 spacecraft would fly to, rendezvous with, and attach to a suitably
chosen target asteroid (there are many candidate asteroids which are
known to be nowhere near a collision course with Earth). By
continuously thrusting, the spacecraft would slowly alter the velocity
of the asteroid by a fraction of a cm/sec--enough to be clearly
measurable from Earth.
What will we learn from this? It is important to remember that this
mission is merely a first attempt to learn more about the mechanics of
asteroid deflection. There are a number of technical complications, as
well as many unknowns about the structure and composition of asteroids.
However, the way to make progress is to build, fly, and test. Much of
what we will learn is generic to many proposed asteroid deflection
schemes, with the added benefit of being able to answer important
scientific questions about asteroids themselves. The best way to learn
about asteroids is to go there.
How does this fit into the new Exploration Initiative at NASA? In
the near term, this mission would be an ideal way to flight test the
nuclear propulsion systems under development as part of the Prometheus
Project. It could also serve as a precursor to a crewed mission to
visit an asteroid. Such missions have been proposed as intermediate
steps to test spacecraft systems for eventual longer term crewed
missions to Mars.
In the longer term, the ability to land on and manipulate asteroids
is an enabling technology for extending human and robotic presence
throughout the solar system. If we are to truly open up the solar
system, this mission is a good way to start. It is likely that someday
we will utilize asteroids for fuel, building materials, or simply as
space habitats. The B612 mission would mark a fundamental change in
spacecraft in that it would actually alter in a measurable way an
astronomical object, rather than simply observing it. Human beings must
eventually take charge of their own destiny in this manner, or we will
someday go the way of the dinosaurs when the next great asteroid impact
occurs.
Senator Brownback. Thank you, Dr. Lu. Mr. Schweickart. I
guess both of you having traveled to space that's--thank you
for being here.
STATEMENT OF DR. RUSSELL L. SCHWEICKART, CHAIRMAN OF THE BOARD,
B612 FOUNDATION
Dr. Schweickart. Thank you for holding hearings, sir. I'll
deal a bit more with some of the policy issues implied in
what's been said today in previous testimony. I think it is
extremely important and reflected to a certain extent by the
questions you've been asking yourself for people to get a
picture of what it is that we're talking about. And so in
addition to repeating, you know, that Near Earth Asteroids in
the hundreds of thousands pose an occasional but substantial
threat to life. Let me give you a couple of specific examples.
As Ed said a moment ago, we're all talking about the same
elephant and giving you a different snapshot of it. It's all
basically the same statistical data, but we're trying to give a
realistic picture. So let me try it this way.
Last night something on the order of hundreds of thousands
to a million bits and pieces of asteroids and comets hit the
Earth. The people that looked up and saw them called them,
``shooting stars.'' That's what you and I would call them if we
happened to be looking up on a clear night as well. They don't
do any damage as you know because the atmosphere protects us.
But getting a little bit bigger and of course a little
fewer of them, a little less frequent with the impacts. If we
took a Near Earth Asteroid the size of this room, one of those
is going to hit us about once every 2 to 3 years and that would
in fact also not do much damage but that would in fact result
in something on the order of a 10 to 15 kiloton, about a
Hiroshima size explosion in the upper atmosphere. That is
something the size of this room every 2 to 3 years.
Now, getting a bit bigger and where it starts getting
dangerous, step outside and picture something the size of the
U.S. Capitol Building. Now, have that come flying at the Earth
at about 20 times the speed of a rifle bullet, if you will.
That's going to happen on the order of every few hundred years
to a thousand years, and in that case, we're going to have an
explosion the size of the largest nuclear weapon in the U.S.
arsenal, something on the order of 10 to 15 megatons of energy.
That again compares with the Tunguska Event of 1908 that we
heard about earlier or a little bit larger if something like
that happened over--if the U.S. Capitol flew at the U.S.
Capitol it would destroy the Washington Metropolitan area
totally. It wouldn't hit the surface. It would actually explode
something 10 to 20,000 feet above the Capitol, but it would
decimate everything underneath it for the whole metropolitan
area.
Now, that particular size that I just related is the
smallest thing that we have all been talking about detecting
ahead of time. That is something down in the vicinity of 100
meters in diameter, so that gives you an idea. That's the
smallest thing that we're all up here proposing that the
Congress direct that NASA, NSF, whoever take under their wing
to get early warning and intelligence on this threat to public
safety.
Protection of the public--so I'll go on from those
examples. Protection of the public from this hazard, and as I
say there's something around 200,000 of these things to be
discovered yet that circle around the sun right now. And the
protection from this hazard depends entirely on increasing the
capability of our current asteroid detection and tracking
program.
This is a known hazard for which public safety is
critically dependent on timely information gathering, as is the
case in all intelligence about threats to public safety.
The hazards posed by Near Earth Asteroids will become
widely know by the general public as the detection and tracking
programs shift their focus to the far more numerous, but very
dangerous smaller NEOs of--and when I say ``smaller NEOs,'' I'm
talking about the size of the U.S. Capitol Building.
Close calls with NEOs in the future will trigger a growing
public concern and commensurate expectation that the government
is doing something about this. The government is doing
something to protect them. At the moment, that is not the case
at all. The government is doing nothing to actually protect
people from any NEOs which are coming our way to hit us. We are
detecting them, but we're not yet providing actual or active
protection.
Unlike other natural disasters, this hazard that we're
talking about here is both predictable and preventable, using
technologies that are being developed by NASA today in its
Prometheus Program.
What is missing today is the goal to explore these Near
Earth Asteroids to gather the critical understanding necessary
to ultimately protect the public from this threat.
Near Earth Asteroids--well, let me just say happily Near
Earth Asteroids are not only a threat. Near Earth Asteroids are
also a rich exploratory--exploration target, excuse me, for
both scientific and economic benefit. Asteroids are easily
accessible gold mines of information about the origins of the
solar system.
They also, and perhaps more importantly, contain a wealth
of resources for utilization in space which are far more
accessible than resources on the moon. In fact, as in the case
with the moon, the Near Earth Asteroids can serve as stepping
stones to Mars.
It is not and probably should not be NASA's job to protect
the Earth from asteroid impacts, but it is NASA's job to
develop space technologies and capability to serve humanity.
Since Near Earth Asteroids represent both an opportunity for
and a threat to humanity and NASA is currently seeking mission
opportunities for its Prometheus Program, it is entirely
appropriate that a portion of its efforts be directed to this
end.
Therefore, B612 Foundation of which both Ed and I are
representing here, call today on the Congress to task NASA
first with increasing the capability of the current Space Guard
Survey consistent with the recommendations of the recent NASA
NEO Science Definition Team Report which you've heard reported
on. In other words, we need, absolutely need better
intelligence to protect the public.
Second, we call on Congress to direct NASA to incorporate
the B612 Mission Goal to demonstrate the capability to land on,
explore and deflect an asteroid as part of it Prometheus
Program.
And third, we call on Congress to request that OSTP
initiate a high level study to develop a U.S. Government Policy
for both national and international response to deflection of
Near Earth Asteroids. This is not, as you're well aware, a
domestic problem only. This is a global problem and we need to
be coordinating around this planet with means to protect life
in the future.
I'd like to emphasize in closing something that Ed alluded
to and that is for the first time in the history of humanity,
we have developed the technology which will enable us, provided
we focus on it, to protect the future of life on this planet.
Up until this time, we've been lucky in this shooting gallery.
The dinosaurs were not lucky. We now have a chance. What we've
got to do is focus on it and take responsibility for the future
of life on this planet and today we have that possibility.
Thank you very much, sir, and we'd be happy to answer any
questions.
[The prepared statement of Dr. Schweickart follows:]
Prepared Statement of Russell L. Schweickart, Chairman, B612 Foundation
Chairman Brownback, Senator Breaux, members of the Committee:
Introduction
First I'd like to thank you for the invitation to speak with you
today about this emerging public policy issue of near Earth objects
(NEOs) threatening life on Earth. One might have thought, just a few
years ago, that the subject of asteroids was one for space wonks and
wanna-be astronauts and astronomers. But today the realization is
rapidly dawning on the media and the general public that asteroids are
a subject of more than passing interest! More and more people are
coming to know that some few of these asteroids do not silently pass
the Earth, but indeed crash in, largely unannounced. On the rare
occasions when this happens they can wreak havoc of a magnitude
unprecedented in human history. At the upper limit impacts by large
asteroids have caused global destruction leading to the virtually
instantaneous extinction of life for most of the species living at the
time. The dinosaurs were momentary witnesses to a billion megaton event
of this kind 65 million years ago. At the lower limit of concern, but
occurring much more frequently, we are dealing with events with an
explosive force of 10-15 megatons. It is worth pointing out, however,
that these small, most frequent events are more powerful than the blast
from the most powerful nuclear weapon in the current U.S. nuclear
arsenal.
Given the extremely low frequency of these natural events in
combination with the extremely grave consequences when they occur, we
find ourselves challenged to properly place this subject in our normal
list of priorities. Inattention to infrequent events, regardless of
their impact, is the ``default'' solution of choice given the crowd of
issues continually burning around our feet.
Therefore the Committee is to be congratulated for its foresight
and exemplary public service in realizing the importance of dealing
with this issue now.
History
Perhaps the best logic path to bring the Committee to appreciate
our recommendations for action is to briefly outline the key realities
the founders of the B612 Foundation faced when we first came together
back in October 2001. We are primarily a group of technical experts
familiar with or working within the fields of space exploration and
planetary science. We are astronauts, astronomers, engineers and a few
others who are knowledgeable about the subject of comets and asteroids
and their history of impacts with the Earth and other solar system
bodies. We came together out of a deep concern that the threat to life
implied in our knowledge of near Earth asteroids (NEAs) was not
resulting in any organized effort to take action to protect the public
from this hazard. We came together to explore whether or not something
could be done, and if so, whether we could trigger a program to protect
the public.
In summary, we faced the following facts:
(1) Asteroid impacts with Earth have, do, and will continue to occur
with devastating consequences to life.
(2) Our detection program (the Spaceguard Survey) has produced a
good statistical characterization of the overall threat and
actual knowledge that at least 60 percent of the asteroids
larger than 1 kilometer in diameter will not strike the Earth
in the next 100 years.
(3) Many impacts by asteroids less than 1 km in diameter, however,
which occur hundreds of times more frequently than those over 1
kilometer, will cause unacceptable devastation at both local
and regional levels.
(4) The increasing capability of our detection programs in the next
several years will result in a dramatic increase in the
discovery rate of these smaller but very dangerous asteroids.
(5) The media and the general public will become ever more aware of
this threat and concerned that something should be done about
it.
(6) A known threat that can potentially destroy millions of lives
AND can be predicted to occur ahead of time, AND prevented,
cannot responsibly go unaddressed.
This inexorable logic led us to decide to take action and examine
whether preventive measures could be taken to mitigate this threat, and
if so, what specific course of action we would recommend.
The Challenge
It became immediately clear to us that the combination of advanced
propulsion technologies and small space qualified nuclear reactors,
both operating in prototype form already, would be powerful enough,
with reasonable future development, to deflect most threatening
asteroids away from a collision with the Earth, given a decade or more
of advance warning.
Nevertheless we saw two immediate problems.
First we lack the specific knowledge of the characteristics of NEAs
necessary to design anything approaching a reliable operational system.
We could readily show that the technology would exist within a few
years to get to and land on an asteroid. We also determined that after
arriving at the asteroid we would have enough propulsive energy
available to successfully deflect the asteroid from an Earth impact a
decade or so later. What was missing however was knowledge about the
structure and characteristics of asteroids detailed enough to enable
successful and secure attachment to it.
Second we recognized that before we would be able to gather such
detailed information about NEAs there would likely be many public
announcements about near misses and possible future impacts with
asteroids which would alarm the general public and generate a growing
demand for action. We felt strongly that there needed to be some
legitimate answer to the inevitable question which will be put to
public officials and decision makers, ``and what are you doing about
this?''
These two considerations led us to the conclusion that the most
responsible course of action would be to mount a demonstration mission
to a NEA (one of our choosing) which would accomplish two essential
tasks: (1) gather critical information on the nature of asteroid
structure and surface characteristics, and (2) while there, push on the
asteroid enough to slightly change its orbit thereby clearly
demonstrating to the public that humanity now has the technology to
protect the Earth from this hazard in the future.
We furthermore determined that this demonstration mission could be
done with currently emerging capabilities within 10-12 years.
We therefore adopted the goal of ``altering the orbit of an
asteroid, in a controlled manner, by 2015''.
Reflecting the work that we have done to bring this goal to
realization, a number of us wrote a descriptive article for Scientific
American magazine entitled, ``The Asteroid Tugboat.'' Scientific
American published it in the November 2003 issue of the magazine. I
have provided reprints of this article to the Committee and I would
like to submit a copy with this testimony and ask that it be
incorporated in the record.
Implementation
A key to implementing this mission is NASA's Prometheus Program.
Shortly after B612 Foundation began work on outlining a mission to
explore and deflect an asteroid NASA announced the formation of its
Prometheus Program to develop and demonstrate technologies to permit
routine human and robotic activity in space ``beyond low Earth orbit''.
The key technologies which NASA recognized would enable this
capability are identical with what we had determined were necessary to
demonstrate the capability to land on and deflect a near Earth
asteroid, i.e., high performance electric propulsion systems and the
space nuclear electric power systems to power them. Shortly after
announcing the Prometheus Program NASA announced the Jupiter Icy Moons
Orbiter (JIMO) mission complete with schematic representations of the
spacecraft. Integral to the design of this mission were the very high
performance engines and space nuclear power system which would be
necessary to enable our B612 mission. We therefore adopted, as an
explicit element of our design, the JIMO/Prometheus capabilities,
recognizing that this was the most likely path to meeting the
demonstration goal that we had set.
Mounting a mission to assure the public that when we discover an
asteroid ``with our name on it'' we can deflect it from a life
threatening impact on Earth does not require the development of
additional new technologies. The key capabilities required are already
``in the pipeline'' of the existing Prometheus Program. No new NASA
money is required, nor is a change in NASA's mission called for. What
is required is that the B612 mission be incorporated within the
Prometheus Program . . . a matter of policy.
Indeed, if one examines the technical requirements associated with
the B612 mission, one sees not only a mission ideally suited to
demonstrating the Prometheus technology, but a mission notably less
demanding than the currently planned JIMO mission. One could then quite
easily consider the B612 mission as either a follow-on or a precursor
to the JIMO mission, depending on NASA's technical judgment as to where
it fits most logically in their mission model.
The B612 mission also fits well into the President's Space
Exploration Initiative. This mission both utilizes and graphically
demonstrates the key enabling technologies for routine future
operations ``beyond low Earth orbit''. It is an ideal way to
demonstrate the technology and the greatly enhanced propulsive
capability implicit in the Prometheus exploration program. In executing
such a mission humankind will, for the first time in its history, have
altered the trajectory of a cosmic body, a demonstration of evolving
capability in space technology and exploration if there ever was one!
Additional Perspective
A few final comments are perhaps appropriate.
Near Earth asteroids are a reality which is here to stay. In fact
they will become far more prominent in the public mind as time goes on
and our detection of them continues to improve. It is therefore
appropriate that we take a more circumspect look at these sometimes
unruly, but ever-present, neighbors. Near Earth asteroids are, in fact,
both a threat and an opportunity.
Certainly we need to learn more about our capability to protect
life here on Earth, and the sooner the better.
Visiting asteroids can also teach us a great deal about the origins
of the solar system, and perhaps even the origins of life. Unlike the
material of the Earth, which has been melted and processed through
extensive geologic activity, the materials of small asteroids have not
been so extensively reprocessed. They are fossil building blocks left
over from the formation of the planets and as such can teach us a great
deal about the original material from which the planets formed.
Perhaps even more important, asteroids, and especially the near
Earth asteroids, are also the most readily accessible and rich
reservoir of non-terrestrial resources available to us. The new space
initiative has emphasized our determination to return to the Moon and
then extend our capability outward to Mars and beyond. One of the
purposes advocated for returning to the Moon is to explore and
potentially develop the capability to utilize the resources there for
human benefit. The possibility of extracting oxygen, water and perhaps
other materials from lunar soils has long been advocated as a potential
capability for reducing the cost of future space operations.
Yet these same resources, and others in rich abundance,
characterize the makeup of asteroids. Unlike lunar materials, which are
largely depleted of heavy minerals, the asteroids are quite rich in
metallic elements, as well as those minerals which may provide water
and oxygen. Furthermore it is significantly less expensive to fly to
and from selected near Earth asteroids than to and from the Moon due to
the virtual absence of gravitational forces associated with these
bodies.
When commercial, entrepreneurial activity emerges into deep space
it will undoubtedly include the development and exploitation of in-situ
resources and services. Given the critical importance of benefit/cost
analysis in any commercial venture it would be surprising if
utilization of asteroidal resources, especially water, is not one of
the first deep space initiatives attracting private capital.
Given then the infrequency of actually having to deflect an
asteroid in order to avoid an Earth impact it is unlikely that humanity
will ever need to develop a stand-alone planetary defense system.
However, given the commercial, as well as the scientific value implicit
in near Earth asteroids it is highly likely that operations to and from
the asteroids will become a routine part of human space operations. One
can readily imagine a time when visiting, using and even moving near
Earth asteroids becomes a routine human capability. Simply calling on
the ``Ace Asteroid Mining and Moving Company'' to nudge asteroid 2018
FA322 gently out of the way may then be all that is required to prevent
an otherwise devastating event.
While the above scenario is somewhat fanciful, it is, given time,
only slightly so. In the meanwhile, in the immediate future, we will be
discovering an increasing number of potentially life threatening NEAs
and the public will become justifiably concerned. Without a legitimate
answer to this concern for their safety this concern could morph into
alarm.
While many lives are lost every year in natural disasters of one
kind or another, there are few natural disasters that can reliably be
predicted, much less prevented. Throughout human experience we have
been faced with comforting and compensating the devastated after the
disaster is over. With near Earth asteroid impacts, however, we are
confronted with a massive natural disaster that can be both predicted
AND prevented, and the public will come to understand that this is the
case.
Given the justifiable public expectation of being protected from
both natural and manmade disasters it is incumbent on us to address
this known threat responsibly. We therefore make the following specific
recommendations:
(1) We call on the Congress to task NASA with increasing the
capability of the current Spaceguard Survey consistent with the
recommendations of the recent NASA Near-Earth Object Science
Definition Team report.\1\
---------------------------------------------------------------------------
\1\ Study to Determine the Feasibility of Extending the Search for
Near-Earth Objects to Smaller Limiting Diameters, Report of the Near-
Earth Object Science Definition Team, August 22, 2003.
(2) We call on Congress to direct NASA to incorporate the B612
mission goal of demonstrating the capability of landing on,
exploring, and deflecting an asteroid as part of its Prometheus
---------------------------------------------------------------------------
Program.
(3) We call on Congress to request that OSTP initiate a high level
study to develop a U.S. Government policy for both national and
international response to the deflection of near Earth
asteroids.
Attachment
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Senator Brownback. Mr. Griffin--Dr. Griffin, how many times
has the Earth been struck by a substantial sized asteroid? By
this, I mean something a 100 meters or greater that we know
about or that we have a pretty good idea it took place. You've
cited a couple, but how many times? Do we know?
Dr. Griffin. I would have to defer to someone with greater
expertise on that than myself, but in fact I don't think the
answer is known. We have catalogued around the globe several
dozen, many dozen known impact events by the scars that they
leave behind.
Senator Brownback. Known impact events that had a
substantial impact on the Earth in that particular area?
Dr. Griffin. Right. Like the meteor crater in Arizona or
larger. OK. Many dozen of those are known. Some of them
ancient. Some of them relatively new in geologic terms. But the
Earth heals itself quite rapidly. The Earth is not a good
witness plate for such events. I'll look at the moon and it
probably offers a better estimate of what really happens to a
celestial body over the course of time.
Senator Brownback. And it's actually even a smaller target
to hit than the Earth so----
Dr. Griffin. That's correct. Senator, just by chance I
happen to have been asked to provide a lecture somewhat along
those very lines so I can tell you that the answer is greater
than hundreds of thousands of times the Earth being hit in its
history by objects a hundred meters and greater in size.
Now, we don't have much evidence of that in the form of
scars. We do see scars from only about 200 impacts that we're
aware of at this time, but again looking at the moon, you can
take each crater there and multiply by about 20 to 30 and know
that that's hit the Earth--that we have been hit--the Earth
that many times.
Senator Brownback. Is that where you come up with that
number as you look at the moon and then multiply out the number
of craters?
Dr. Griffin. What I would refer you to as the most
authoritative thing, sir, would be in fact the report sitting
in front of Grant Stokes here that he co-chaired in terms of
the development. And there is within that report a graph which
give you the best knowledge that we have, statistical knowledge
of the frequency of asteroids in near Earth space and you can
simply utilize that graph at any size asteroid you want and get
the number and the size and power of any of these asteroids. So
I refer you to that excellent report.
Senator Brownback. Dr. Stokes. Do you know the answer to
that question?
Dr. Stokes. What we've done to come up with the best
estimate of impact actually looks at a number of things. One
looks a lunar cratering rate to get an estimate.
One can also get an independent estimate looking at the
performance of the search systems that have been ongoing which
have been making a lot of progress recently. And in fact, you
can take all the search volume that they've done, and all the
detections and all the re-detections, use that to estimate an
impact rate. And in fact, it's getting to the point where all
of those numbers are beginning to come together and be
consistent and so we're very happy with the about 1,100 larger
than a kilometer size. We believe that's a good estimate.
Once you have that estimate and then work some
extrapolations from there which can be tied down at various
sizes from the moon and also the experience of very small
events, things hitting LDEF for instance, micrograins, you can
put those all into a continuum and the story sticks together
very well.
On that basis, we can then estimate the rate of impacts as
a function of size, which is where we came up with the numbers
that I previously had quoted.
Senator Brownback. Well, how many times this last century
has the Earth been struck by a substantial asteroid that caused
at least significant localized damage?
Dr. Griffin. I think we know of two specific instances. One
in Siberia in 1908. One again in Russia in 1947, both of which
caused substantial damage on the ground. We know of a number of
other events that range down to an asteroid hitting a car in
the Eastern seaboard a few years ago and----
Senator Brownback. That would be a real unlucky day,
wouldn't it? I mean, you're just sitting here in your car and--
--
Dr. Griffin. Actually, it hit a car in a garage and I think
it vastly increased the price of that car that day.
Senator Brownback. That's not so unlucky.
Dr. Griffin. There certainly have been many other events
where things get down to the ground many of which land in the
water. Many of which land in unpopulated areas and are not
seen. Another way to get data is to look at the military
satellites that look down for events in the atmosphere. They
routinely detect, you know, modest size objects, but kiloton
and larger events in the upper atmosphere, so there are
statistics coming from those as well.
Senator Brownback. What's the chance of getting
international cooperation at the operational or funding level
to get at least the catalogue of these objects?
Dr. Griffin. Let's see. I think to some extent there is a
loosely coordinated international effort ongoing now. Most of
the large surveys are operated in the United States based
largely on NASA funding, and I think there's a view in the--at
least Europe and the rest of the world that if NASA's doing
that maybe we should just let them do that and contribute where
we can.
Another place that work has to be done is in following up
objects. The large surveys where we go out and find a large
number of these objects, initially finding them is only part of
the process.
We also need a continuing stream of observations to develop
a good orbit and keep track of them. Many of those are provided
by international sources. Many of them are provided by amateurs
that are very interested in doing this. Many of them Japanese.
Eastern Europe in fact has some very active professionals that
do this.
And all of that data is sent to a place called, The Minor
Planet Center in the Harvard Smithsonian in Cambridge,
Massachusetts where all that data comes together and is used to
maintain a catalogue of all of the objects. So that is
chartered by the International Astronomical Union. It is an
international body that gives discovery credit and monitors
naming rights and things like that.
So there is a very international flavor on these after
discovery and that works actually very well.
Dr. Schweickart. Yes, just a minor additional comment.
There is an excellent report that was chartered by the
Parliament of the United Kingdom several years ago and I also
recommend that Task Force Report to you. It made excellent
recommendations in terms of the U.K. jumping in to provide
resources for this very vital task. Unfortunately, there has
been no action taken on the excellent recommendations of that
report. As recently as a couple of months ago in Parliament
specific recommendations were considered and the bottom line is
nothing in fact happened.
Another action has been taken by the OECD. OECD has begun
to hold several discussions on the issue of mitigation of
asteroid and comet impacts and what might be done in terms of
disaster preparedness. There was a meeting a year ago, January
in Frascati, Italy, but again, there was no expenditure of
funds.
What was done there which I would strongly urge, Senator
Brownback, is that all nations participating in the OECD
hearing were recommended that they identify a particular
governmental institutional person to monitor this issue of
asteroid impacts and their consequences.
Ironically, while NASA is today tasked with conducting
certain surveys, there is no identification within the U.S.
Government of direct responsibility for monitoring this as a
public safety issue. And that would be--that is in fact a
recommendation by a number of organizations and I would
encourage that that be looked at by this committee.
Senator Brownback. I think that's one of the proposals in
the Rohrabacher bill from the House side.
Dr. Griffin. Yes, it is.
Senator Brownback. That we're looking at here from this
side. I understand that maybe some of you already have
commented on this and I haven't picked it up. But the American
Institute of Aeronautics and Astronautics held a conference on
protecting the Earth recently and were any of the
recommendations that you've put forward recommended by that
conference or does anybody----
Dr. Griffin. Yes, sir, I can address that. In fact, I
talked yesterday by phone with the General Chairman of the AIAA
Conference on protecting the Earth from asteroid and cometary
impacts. There is a final report from the conference itself and
I can, or better yet AIAA, American Institute of Aeronautics
and Astronautics, can make that conference report available to
you.
It has also been compressed and presented or is being
presented to the AIAA per se as a policy document. They will
shortly vote on that and there will be an official AIAA
recommendation, but that has not yet been issued. I can read
you one final paragraph to give you a flavor of the AIAA
position. They say: ``Future impacts by comets and asteroids
are a certainty. Such impacts could have severe consequences
even ending civilization and humanity s existence. Life on
Earth has evolved to the point where we can mount a defense
against these threats. It is time to take deliberate steps to
assure a successful defensive effort should the need arise.''
So the AIAA I believe will take a fairly strong position on
this proposal.
Mr. Richardson. I would echo that. I'm the President-Elect
of AIAA for the coming year and a member of the Board of
Directors and I have followed this and feel quite certain that
the organization--or the directors will vote affirmatively as
Rusty has suggested.
Senator Brownback. Is this a high priority for that
organization?
Mr. Richardson. Yes, it is, again, in support of the
overall conclusions of the study that has been referenced here
several times and of the President's exploration initiative
because we believe that it is all tied together.
Senator Brownback. That this should be a key part of the
President's overall exploration initiative?
Mr. Richardson. I believe that's correct.
Senator Brownback. It seems to me that it ties in with it
as well and that there's an additional--this huge safety factor
and issue here for the area that might get hit or all of
civilization even in the most catastrophic----
Mr. Richardson. That's correct. The safety issue is a
little difficult for many people to get their arms around
because if you take other threats for example, you can
calculate quite well the odds that any individual has of being
struck by lightning and we know that, but most individuals will
not ever be struck by lightning.
However, we know that in any given year the odds are quite
small that the Earth will be struck by a major asteroid. But we
know that sooner or later that will occur and when it occurs
everyone will die. Unlike most other catastrophic hazards to
life and property which affect only a small subset of the human
race, it is inevitable that an asteroid will strike the Earth
and that it will have the capability to essentially take out
the whole plant and that's what's different about this
particular hazard.
Dr. Griffin. Senator Brownback, if I could try a slightly
different perspective to the question that we're discussing
right now. If you think about the asteroids as a mixed bag,
that is there's good news and bad news. The bad news we've been
focusing on here today, but there's good news there in terms of
resources as well as scientific knowledge.
But if I just deal with resources, let me say that the
whole President's new initiative in space to enable routine
operations of human kind beyond low Earth orbit will ultimately
depend upon accessing resources that are already in space and
utilizing them.
Asteroids are the ideal source of that because you don't
have to lift them off the moon number one because it has such
low gravity. They're right there with no gravity around them
and they're actually richer than the lunar soils. So in terms
of commercial private enterprise activity in space, I think
there's no question but that private investment, once there is
a buyer of the products and services, private investment will
find it profitable to mine and produce--to mine minerals or
whatever, oxygen, water, you name it, and provide services
associated with the Near Earth Asteroids.
Now, when that commercial operation gets going, the once
every three or four hundred years that you will need to deflect
an asteroid because we find one heading our way, will be a
simple matter of contracting with the Ace Mining and Moving
Company to push that one a bit you know in what they're doing
and get it out of the way.
So I think that you're looking at routine operations
developing around asteroids and almost as a natural byproduct
of that, the capability to protect the Earth will emerge. So I
think there is a great deal of correlation between the overall
capability that we're looking for and the long-term development
of the space environment beyond low Earth orbit as in the
President's initiative.
Senator Brownback. Well, gentlemen, thank you very much for
joining me today. We'll keep the record open for the requisite
amount of time if you would care to add to your comments that
were put forward here today.
I did submit a series of questions and I don't--I think
some of them were to you gentlemen from Mr. Nelson and so those
will be submitted to you. And if you could respond to those, I
know Senator Nelson would certainly appreciate that as well.
Very interesting. Very illuminating and as usual a resource
issue. And resources is always about a competing set of
interests in it and hopefully we can get more resources to this
for both the protection and for the opportunity that they
represent.
God speed to you. It's a very interesting field that each
of you are involved in and quite important for the future of
society, future of humanity.
Thank you for coming. The hearing is adjourned.
[Whereupon, at 4:19 p.m., the hearing was adjourned.]
A P P E N D I X
Prepared Statement of Congressman Dana Rohrabacher (R-CA)
I want to thank Senator Brownback for his leadership in holding
today's hearing on the threat posed by near Earth objects (NEOs). As
Chairman of the Space and Aeronautics Subcommittee, I've made
addressing this threat one of my top priorities. Our hearings have
revealed that monitoring and tracking NEOs such as comets and asteroids
is not only vitally important to the advancement of the field of
astronomy, but also critical in identifying NEOs that threaten the
Earth. Recent press accounts of asteroids passing close to the Earth
have raised public awareness of the possibility that these objects
could one day hit the Earth with potentially catastrophic consequences.
Given the vast number of asteroids and comets that inhabit Earth's
neighborhood, greater efforts for tracking and monitoring these objects
are critical.
This is why I introduced H.R. 912 the ``Charles `Pete' Conrad
Astronomy Awards Act,'' which passed the House last month, and H.R.
3813 the ``George E. Brown, Jr. Near-Earth Objects Survey Act.'' It is
vital that we use all available public and private sector resources for
tracking and monitoring NEOs.
H.R. 912 authorizes the NASA Administrator to give one award each
year to the amateur astronomer or to the group of amateur astronomers
that discovered the intrinsically brightest near-Earth asteroid among
the near-Earth asteroids discovered during the preceding year by
amateur astronomers, and another award to the amateur astronomer or
group of amateur astronomers that made the greatest contribution during
the preceding year to the Minor Planet Center's catalogue of known
asteroids. The recipients of the awards, in the amount of $3,000, are
limited to U.S. citizens and permanent residents.
This bill is a tribute to Pete Conrad for his tremendous
contributions to the aerospace community over the last four decades.
Pete Conrad was a pilot/explorer/entrepreneur of the highest caliber.
He commanded Apollo XII, and during that mission became the third man
to walk on the Moon. I find no better way to honor Pete Conrad than to
establish an annual astronomer's award for future asteroid discovers in
his name. He always wanted people to be looking up with a positive
``can-do'' American spirit--exemplified by his historic description of
landing on the Moon.
H.R. 3813 authorizes the NASA Administrator to plan, develop, and
implement a near Earth objects survey program for the purpose of
detecting, tracking, cataloguing, and characterizing physical
characteristics of near-Earth asteroids and comets 100 meters or
greater in diameter. The bill also amends the NASA Act of 1958 by
directing the agency to use its resources and the expertise of its
workforce to carry out the NEO survey program--so as to provide warning
and mitigation of the potential hazards of NEOs that threaten impact
with the Earth. The bill authorizes appropriations in the amount of $20
million for Fiscal Years 2005 and 2006 to enable NASA's efforts in this
area.
In his agency vision statement, NASA Administrator Sean O'Keefe
talked about the planet's environment. I believe protecting our planet
from impacting asteroids should also be one of NASA's major concerns. A
few years ago, NASA initiated the ``Spaceguard'' plan, which is
intended to catalog at least 90 percent of them by 2010. Presently, the
Spaceguard program appears to be on track, but its focus is on
surveying asteroids large enough to destroy all life on Earth. Surveys
of smaller asteroids with the potential to destroy cities, countries,
and to bring about changes in global climate should also be vigorously
pursued.
Of course, the threat of an asteroid hitting the world is a serious
matter. The idea of a catastrophic asteroid or comet impacting on the
Earth has garnered much attention in the media and popular culture.
It's vital for all of us to realize, however, that this is not science
fiction. We all know that the Earth's moon and many other planetary
bodies in the solar system are covered with impact craters. Most people
have heard of the ``dinosaur extinction'' theory or perhaps seen
pictures of the meteor crater in Arizona. However remote the
possibility of NEOs striking the Earth and causing worldwide calamity
in our lifetime, it has happened and it will happen again unless
mankind is able to detect and possibly avert a catastrophe.
While the asteroid that killed the dinosaurs is estimated to occur
once every 100 million years, smaller, yet still very hazardous
asteroids impact the Earth much more frequently. For example, the
destructive force of the 1908 Tunguska event in Siberia was roughly
equal to a 10-megaton blast of TNT caused by an asteroid estimated to
be about 200 feet Greenland involving an asteroid, which had a
destructive force measuring 100 kilotons of TNT.
Ironically, if you look at asteroids from the perspective of our
national goals in space, they also offer us unique opportunities. In
terms of pure science, asteroids are geological time capsules from the
era when our solar system was formed. Even better, they are orbiting
mines of metals, minerals, and other resources we can use to possibly
build large structures in space without carrying everything up from the
Earth. So far, NASA has surveyed 600 asteroids, but this is a small
fraction of the projected total. What needs to be done now is to fully
survey the NEO population.
In closing, it is my hope that H.R. 3813 will bring greater
attention to the NEO issue by focusing NASA more closely on this
critical area of study, because NEOs have given the topic of planetary
defense a serious tone within the scientific community. The first step
is a thorough tracking of all sizeable NEOs, and H.R. 912 and H.R. 3813
are modest steps toward this goal. Thank you, Mr. Chairman.
[all]
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