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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 

( 

(II) 

SENATE COMMITTEE ON COMMERCE, SCIENCE, AND TRANSPORTATION 

ONE HUNDRED EIGHTH CONGRESS 

SECOND SESSION 

JOHN MCCAIN, Arizona, Chairman 

TED STEVENS, Alaska 

CONRAD BURNS, Montana 

TRENT LOTT, Mississippi 

KAY BAILEY HUTCHISON, Texas 

OLYMPIA J. SNOWE, Maine 

SAM BROWNBACK, Kansas 

GORDON H. SMITH, Oregon 

PETER G. FITZGERALD, Illinois 

JOHN ENSIGN, Nevada 

GEORGE ALLEN, Virginia 

JOHN E. SUNUNU, New Hampshire 

ERNEST F. HOLLINGS, South Carolina, 

Ranking 

DANIEL K. INOUYE, Hawaii 

JOHN D. ROCKEFELLER IV, West Virginia 

JOHN F. KERRY, Massachusetts 

JOHN B. BREAUX, Louisiana 

BYRON L. DORGAN, North Dakota 

RON WYDEN, Oregon 

BARBARA BOXER, California 

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 

CONRAD BURNS, Montana 

TRENT LOTT, Mississippi 

KAY BAILEY HUTCHISON, Texas 

JOHN ENSIGN, Nevada 

GEORGE ALLEN, Virginia 

JOHN E. SUNUNU, New Hampshire 

JOHN B. BREAUX, Louisiana, Ranking 

JOHN D. ROCKEFELLER IV, West Virginia 

JOHN F. KERRY, Massachusetts 

BYRON L. DORGAN, North Dakota 

RON WYDEN, Oregon 

BILL NELSON, Florida 

FRANK R. LAUTENBERG, New Jersey 

(III) 

C O N T E N T S 

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 

(1) 

NEAR EARTH OBJECTS 

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. 

2 

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:] 

3 


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4 


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7 

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 

8 

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:] 

9 

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 

10 

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. 

11 

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 PanSTARRS 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 

12 

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 

13 

life scenario which unfolded 10 years ago, when comet ShoemakerLevy 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 metersized 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 

14 

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, MA Dr. Grant Stokes 

Near Earth Asteroid Tracking (NEAT) 

Jet Propulsion Laboratory, CA Dr. Ray Bambery 

Lowell Observatory Near Earth Object Search (LONEOS) 

Lowell Observatory, AZ Dr. Edward Bowell 

Catalina Sky Survey LPL, University of Arizona Mr. Steve Larson 

Spacewatch LPL, University of Arizona Dr. Robert McMillan 

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. 

15 

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. 

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 prescripted software routines to optimize sky coverage and therefore maximize object 

detections. 


407JOHNS1.eps
16 

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 

17 

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. 

18 

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. 

19 

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. 

20 

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. 

21 

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. 

22 

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, 

23 

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 devVerDate Nov 24 2008 11:30 Sep 07, 2016 Jkt 075679 PO 00000 Frm 00027 Fmt 6633 Sfmt 6601 S:\GPO\DOCS\21399.TXT JACKIE
24 

astating 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. 

25 

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-Chair) Jet Propulsion Laboratory/Caltech 

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 (USAF, ret.) NASA Headquarters 

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 (beVerDate Nov 24 2008 11:30 Sep 07, 2016 Jkt 075679 PO 00000 Frm 00029 Fmt 6633 Sfmt 6621 S:\GPO\DOCS\21399.TXT JACKIE
26 

tween 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 groundbased 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 subkilometer 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/ 

27 

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. 

28 

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 subkilometer 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. 


407STOKE1.eps
29 

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. 

30 

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 

31 

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, 

32 

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 groundbased spectroscopic data that there is a great deal of variability among these objects. 

33 

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. 


407GRIFF1.eps
34 

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-toground 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 socalled 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. 

35 

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 

36 

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 curVerDate Nov 24 2008 11:30 Sep 07, 2016 Jkt 075679 PO 00000 Frm 00040 Fmt 6633 Sfmt 6601 S:\GPO\DOCS\21399.TXT JACKIE
37 

rently 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 

38 

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 

39 

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 hapVerDate Nov 24 2008 11:30 Sep 07, 2016 Jkt 075679 PO 00000 Frm 00043 Fmt 6633 Sfmt 6601 S:\GPO\DOCS\21399.TXT JACKIE
40 

pened 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 

41 

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 

42 

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 AsVerDate Nov 24 2008 11:30 Sep 07, 2016 Jkt 075679 PO 00000 Frm 00046 Fmt 6633 Sfmt 6621 S:\GPO\DOCS\21399.TXT JACKIE
43 

teroid 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 followon 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. 

44 

1Study 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. 

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

(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. 

45 

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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 

54 

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. 

55 

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. 

56 

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 

57 

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.] 

(59) 

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 

60 

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. 

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