Near-Earth Objects

* Your Nov. 11 editorial correctly pointed out that there should be an appropriate concern within the U.S. over the issue of space objects on Earth-threatening orbits. A near-Earth object larger than one kilometer would be expected to cause a global rather than a local disaster if it were to strike the Earth. Your editorial noted that the British task force report was critical of U.S. efforts in this area, but the report notes that “the United States is doing far more about near-Earth objects than the rest of the world put together.” It further points out that our work to discover 90% of objects larger than one kilometer within 10 years “is progressing well.”

NASA is funding the vast majority of current efforts to find these objects. Quite apart from the money spent on six flight projects to nine comets and asteroids in the next decade, NASA currently spends about $3.5 million per year on ground-based observations of near-Earth objects. Five U.S. observatories are operating full-time to discover them. It is now estimated that the total population of near-Earth asteroids larger than one kilometer numbers about 1,000, and some 435 have been discovered already. Forty percent of these discoveries have been made in the last two years.

DON YEOMANS

Manager, NASA Near-Earth

Object Program Office

Jet Propulsion Laboratory

Pasadena