Theodore von Karman Lecture
Radar is a very powerful astronomical technique for studying the physical properties and refining the orbits of near-Earth asteroids. The world's only two radar telescopes for imaging asteroids are at Arecibo, Puerto Rico, and Goldstone, California. These telescopes can image near-Earth asteroids with resolutions as fine as several meters, which greatly exceeds the finest resolution available from any ground- or space-based optical telescope (even the Hubble Space Telescope). Radar images reveal an object's size, shape, rotation state, and features on its surface such as craters, ridges, and even large boulders, and have discovered that 1/6 of near-Earth asteroids larger than 200 meters in diameter are double systems that revolve around each other, like miniature versions of the Earth and Moon, and that 10% of near-Earth asteroids look like gigantic peanuts, while others resemble muffins and potatoes!