magnitude. The present rate of NEO characterizations by radar, approximately 1 per year, might be increased by a factor of 10. Infrared measurements of size and albedo require large-aperture instruments and could double or triple from the present rate of fewer than 10 per year. Priority access would affect ongoing observation programs (depending on the number of participating facilities). The quality and consistency of data might be uneven, depending on the instrumentation available, and the cooperation and flexibility of observers would be required.

Augmentation 2: Provide expanded, dedicated telescope access for characterization of NEOs.

With the construction and planned commitment of national operational resources to large (4- to 10-m) telescopes, consideration is being given to decommissioning several national facility telescopes in the 2-m class.3 If funds for NEO research were provided for maintenance of an existing telescope of at least 2-m aperture (including the cost of necessary support personnel) in order to ensure more or less full-time access, use of such a facility would allow physical and mineralogical characterization of as many as half of the NEOs discovered each year. A minimum set of instruments would include CCDs with broad-band filters, a 10-micron photometer, and a near-infrared array spectrometer. Funding would be required for instrument construction.

Laboratory Studies and Instrumentation

Baseline Recommendation: Support continued research on extraterrestrial materials to understand the controls on spectra of NEOs and the physical processes that alter asteroid and comet surface materials.

Meteorite regolith breccias and some interplanetary dust particles potentially provide samples of asteroidal and cometary surface materials. Mineralogical, chemical, textural, and spectral studies of such materials can constrain the interpretation of NEO spectra and help quantify the proportions of phases that dominate their spectra. The discovery and characterization of altered surficial layers in regolith breccias would greatly assist in solving the question of space weathering. Laboratory studies would also be useful in addressing this problem. The occurrence of different meteorite types on the same asteroids can be understood from petrologic studies, as well as theoretical models of the accretional, thermal, and collisional histories of asteroids and comets. An advantage of continuing such work is that it tends to be an inexpensive aspect of NEO research. However, it is often difficult or impossible to make connections between specific NEOs and meteorites or interplanetary dust particles.

Augmentation 1: Support the acquisition and development of new analytical instruments needed for further studies of extraterrestrial materials and for characterization of returned NEO samples.

Materials research provides important information used in defining NEO exploration targets and the instrumentation required for spacecraft missions.4 State-of-the-art instruments in laboratories on Earth are necessary to develop and maintain scientific expertise in readiness for asteroid sample-return missions. Even adapting existing instrumental technologies for the analysis of extraterrestrial materials requires a great deal of time and effort, and so laboratory facilities and protocols must be in place long before they are needed to analyze returned NEO samples. The development of new and improved microanalytical techniques and instruments will also be necessary for characterization of organic compounds, isotopes, and other constituents of tiny meteoritic and interplanetary dust samples, as well as the modest-sized samples to be collected on NEO sample-return missions. An advantage of supporting instrument development is that laboratory equipment is versatile and can be used in many research programs (e.g., the search for evidence of life in martian meteorites and returned martian samples); additionally, facility instruments can be shared among many investigators.

Spacecraft Technology, Instrumentation, and Missions.

Baseline Recommendation: Support NEO flyby and rendezvous missions.

Spacecraft such as NEAR and Deep Space 1 are already capable of NEO flyby and rendezvous missions. The high spatial resolution afforded by such missions provides important information on NEO physical characteristics, composition, formation, and geologic history that is otherwise unobtainable. Some flight instruments for remote sensing are already in a reasonably advanced state of development but require miniaturization. An advantage of



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