NASA's Jet Propulsion Laboratory, using technology similar in some ways to that used to power microwave ovens, is detecting and imaging asteroids by beaming radar signals toward the objects, then collecting and analyzing the reflected waves. Radar astronomy doesn't require a night sky or a space probe to find and analyze the objects-just the world's largest dish antennas. Radar pulses are beamed toward selected targets and the reflected "echoes" are collected and analyzed to reveal information about surface features, rotation, as well as internal structure and density of the asteroids.
Closer targets provide better signals and therefore more accurate information from which three dimensional models can be imaged, and the rotation of the asteroid can be defined. A good signal can enable a spatial resolution of less than 10 meters. Echoes from more than 190 near-Earth asteroids have been detected, showing great variations in structure and composition, with no two alike. They can be stony, metallic, smooth or coarse in texture, traveling alone or with satellites, and come in an endless variety of shapes and sizes.
Arecibo Observatory in Puerto Rico, with its 100-foot diameter telescope, and the 70 meter Goldstone antenna, located in the Mojave Desert of southern California, are the only two places in the world performing effective radar astronomy. Each complements the other, making an effective asteroid detection partnership. Researchers, using the antennas of Arecibo and Goldstone, were able to observe the near-Earth asteroid 1999 KW4 and determine it to be a double asteroid, or binary, comprised of two rubble clusters orbiting each other. Although the asteroid passes near Earth occasionally, and is classified as a Potentially Hazardous Asteroid, the information provided by the observatories indicated that it will not cross Earth's path for at least 1,000 years.
Radar astronomy has been shown to be vital for locating asteroids and predicting the orbits of the ones that could pose a danger to the Earth, as this form of asteroid detection and analysis has proven to be much more accurate than observations made by optical instruments. Radar astronomy would also provide more accurate information about any approaching comets, including their composition and projected path.
Future technology is planned which will make it possible to discern surface features on asteroids with four times the amount of detail than is possible now. It is also suggested that before any space mission to an asteroid, the necessary pre-flight, scientific analysis will depend upon the information gathered by radar astronomy.