Mr. Chairman and Members of the Subcommittee:

I am pleased to have this opportunity to appear before the Subcommittee today to discuss NASA's current efforts and future plans to inventory and characterize the population of Near Earth Objects (NEOs).

BACKGROUND

This Committee has been a leader in focusing attention on the importance of cataloging and characterizing Earth-approaching asteroids and comets. In 1992, the Committee on Science directed that NASA sponsor two workshop studies, the NEO Detection Workshop, which was chaired by NASA, and the NEO Interception Workshop, which was chaired by the Department of Energy. In March 1993, the Science Committee held a hearing to review the results of these two workshops. In 1995, at the Committee's request, NASA conducted a follow-up study which was chaired by the late Dr. Gene Shoemaker. Each of these studies stressed the importance of characterizing and cataloging NEOs with diameters larger than 1 km within the next decade. We have taken steps to put us on a path to achieving this goal. I am here today to tell you about those steps, as well as to bring you up to date on the rich program of space missions to NEOs and related objects.

The NEO population is derived from a variety of scientifically interesting sources including planetessimal fragments and some Kuiper belt objects. Indeed, the Office of Space Science Strategic Plan includes as a specific goal " . . . to complete the inventory and characterize a sample of Near Earth Objects down to 1 km diameter.î While the threat of a catastrophic collision is statistically small, NASA has a vigorous program of exploration of NEOs planned, including both asteroids and comets.

There has been much recent discussion about the potential threat posed by NEOs, but NASA has long been interested in them from a scientific standpoint. NEO investigations have had to compete for support against a number of other compelling science programs; funding selection criteria were based principally on scientific merit. This approach has led to the detection of over 400 NEOs, including more than 100 objects larger than 1 km and to a rapid advancement of the technologies necessary for NEO detection. In fact, this research effort has demonstrated that we can inventory the NEO population in a reasonable time, about a decade, with an achievable increase in funding from recent levels.

A little less than a year ago, NASA initiated a study of its existing NEO research to determine how well we were doing in terms of reaching our goal of inventorying the population of NEOs larger than 1 km and characterizing a sample of them. While we have made some impressive strides, it became apparent that the funding levels resulting from scientific competitive review ($1-1.5 M per year) was not sufficient to accomplish our goal. The detection of new NEOs in 1997, the last year for which we have statistics, is barely 10% of the rate needed to achieve the goal suggested in the Shoemaker report (detection of 90% of the NEO population larger than 1 km within a decade). In simple terms, we need to survey about 20,000 square degrees of sky a month for NEOs to a limiting brightness of approximately 20^th magnitude to accomplish the inventory. To understand what this means, note that 20,000 square degrees is about half the sky and that magnitudes are a measure of apparent brightness-a 6^th magnitude object is at the limit of detection for the human eye and 20^th magnitude is almost 100,000 times fainter.

I would now like to describe briefly the existing search programs, NASAís plans to improve them, and some promising new research programs which we are considering. I will also comment on our joint activities with the Air Force Space Command. All of these efforts are directed toward increasing the rate of discovery of NEOs in order to reach our goal.

STATUS OF ONGOING SEARCH PROGRAMS

NASA's ground-based NEO program comprises three parts: Spacewatch, the Near-Earth Asteroid Tracking (NEAT) program, and the Lowell Near Earth Asteroid Survey (LONEOS).

Spacewatch

Spacewatch is a program at the University of Arizona, led by Dr. Tom Gehrels, which has done much of the pioneering work in the field of NEO detection. This group is responsible for more NEO discoveries than any other. The current Spacewatch Program searches 200 square degrees of sky per month to a depth of 21^st magnitude. This year NASA is funding a new state-of-the-art focal plane camera for Spacewatch, which will lead to an 8-fold increase in the area of sky that they search each month (to 1600 square degrees per month). We hope in the future to assist them in their efforts to bring their new 1.8 m telescope on line. This telescope will enable them to detect even fainter NEOs.

NEAT

NEAT is a program headed by Dr. Eleanor Helin at the Jet Propulsion Laboratory. NEAT uses a specialized camera, which is based on a 4096x4096 CCD array for use on the 1 m GEODSS (Ground-based Electro-Optical Deep Space Surveillance) telescope, operated by United States Air Force Space Command (USAFSC) on Haleakala, Maui, Hawaii. This group is currently limited by the number of nights per month on which they can observe the sky using the GEODSS system. They are presently observing six nights per month on one of the seven GEODSS telescopes. With recent improvements they are now able to search 800 square degrees per night (4800 square degrees per month) to about 20^th magnitude. We have funded the construction of 2 more cameras, which we hope to install on two other GEODSS telescopes. This increase in the level of effort for NEO detection is being discussed in the NASA-USAFSC Partnership Council co-chaired by NASA Administrator Daniel Goldin and AFSC Commander Gen. Howell Estes. It is in principle possible to scan 21,000 square degrees a month with three cameras and full access to three of the GEODSS telescopes. It is important to note that the GEODSS system includes one southern hemisphere site.

While we certainly hope to increase our surveying ability using the GEODSS system, we are aware that it has other vital missions. NASAís FY 1999 budget request includes sufficient funding for the construction of four more NEAT cameras, which will enable us to equip all seven GEODSS telescopes. The final application of the funds will depend on the demonstration that the NEAT camera can support the existing mission of the GEODSS system as well as the search for NEOs. This matter is currently being reviewed by the Partnership Council on NEOs.

LONEOS

LONEOS is led by Dr. Ted Bowell at Lowell Observatory in Flagstaff, Arizona. This group has great potential (capability to observe 4,300 square degrees a month down to 20^tth magnitude); however, they have not yet reached this level of performance. We are funding an augmentation to buy a second focal plane CCD and to support additional software development in order to allow them to reach their performance objective.

NEW SEARCH PROGRAMS

The increased interest in the search for NEOs has led to several recent proposals from new groups:

Catalina NEO Survey

We are supporting a new search program at the University of Arizona, which is headed by Mr. Steven Larson, to refurbish an existing telescope on Mount Lemon. When fully operational, this system will survey 8,000 square degrees of sky per month to a depth of 19^th magnitude. This program will be fully operational within a year.

LINEAR

NASA is evaluating a proposal for support of a very promising search program from the MIT Lincoln Labs. This effort called LINEAR (Lincoln Near Earth Asteroid Research program) uses a state-of-the-art camera which was developed as a possible prototype for the next generation GEODSS detector. They are proposing to use a 1 m telescope at their Experimental Test Site near Socorro, New Mexico, to survey 10,000 square degrees down to 21^st magnitude each month.

With coordination of these different observational programs, NASA believes it is possible to obtain the level of sky coverage to the appropriate limiting magnitude required to complete the survey. NASA has already committed over $3M this year, much of it to fund improvements to focal plane detectors, software, and electronics. NASA is committed to funding both existing and new search programs at, at least, the FY1998 level. We believe this is close to the level required to achieve our objective.

SPACE-BASED MISSIONS RELEVANT TO OUR UNDERSTANDING OF NEOs

The study of the physical characteristics of NEOs is a major focus of both ground-based research and space missions. The ground-based work includes NASA-supported radar imaging of NEOs utilizing the Arecibo Radio Telescope and spectroscopy of NEOs from optical/IR telescopes to determine their composition.

Several NASA missions will travel to asteroids and/or comets to provide us with exciting new scientific insights about these objects at the same time this information is valuable for any future effort to respond to an impact threat. Over the next decade NASA will invest approximately $1B in these missions. Missions in flight or in development are:

1. NEAR, which will reach the near-Earth object Eros in January, 1999, orbit for one year to measure its surface and interior properties, and then land on Eros.

1. CONTOUR, which will fly by a set of three short-period comets and make the first detailed comparative study of cometary nuclei.

1. STARDUST, which will return a sample from the coma of short-period comet in 2006.

1. ROSETTA, is a European Space Agency (ESA) mission to comet P/Wirtanen. NASA is providing three ROSETTA orbiter instruments and support to eight U.S. co-investigators on other orbiter instruments.

Missions soon to enter development are:

1. MUSES-C/N with Japan to deploy a US-provided micro-rover on the surface of an NEO and to return a sample of the asteroid to Earth in 2006.

1. DS-4/Champollion to land on a comet, measure its composition, test sampling and sample-return technologies for small bodies, and perhaps even return a sample.

1. Pluto/Kuiper Belt Express to survey one or more Kuiper belt objects before deflection into the inner solar system.

CONCLUDING REMARKS

The issues and challenges posed by NEOs are inherently international, and any comprehensive approach to addressing them must be international as well. Central areas of concern include coordination among NEO observers and orbit calculators around the globe and public notification should an object posing a significant hazard to Earth be discovered. NASA has begun discussing, with the international community, convening an international workshop to address these issues. The workshop will likely be held during the first half of 1999. The goal of this workshop will be to develop international procedures and lines of communication to ensure that the best available accurate information about any potentially hazardous object is assembled and disseminated to the public in the shortest possible time.

To facilitate coordination among NASA-supported researchers, other agencies and scientists, and the international community, NASA is establishing an NEO Program Office. This Office will coordinate ground-based observations, ensure that calculated orbital elements for NEOs are based on the best available data and support NASA Headquarters in the continuing development of strategies for the exploration and characterization of NEOs. In the unlikely event that a potentially hazardous object is detected, the Office would coordinate the notification of both the observing community and the public of any potentially hazardous objects discovered.

NASA is committed to achieving the goal of detecting and cataloging 90% of NEOs larger than 1 km in diameter within 10 years, and to characterizing a sample of these objects. We are developing and building instruments, and developing partnerships -- particularly with the Air Force -- which should lead to the necessary detection and cataloging capability being in place in 1-2 years. This capability will also allow us to detect and characterize many NEOs smaller than 1 km.

In summary, NASA's obligation and commitment is to ensure that we have the information necessary to understand the hazards posed by NEOs.