Mar. 19, 2013 A sequence of radar images of asteroid 2013 ET was
obtained on March 10, 2013, by NASA scientists using the
230-foot (70-meter) Deep Space Network antenna at Goldstone,
Calif., when the asteroid was about 693,000 miles (1.1 million
kilometers) from Earth, which is 2.9 lunar distances. The radar
imagery suggests the irregularly shaped object is at least 130
feet (40 meters) wide. The 18 radar images were taken over a
span of 1.3 hours. During that interval, the asteroid completed
only a fraction of one rotation, suggesting that it rotates once
every few hours. The radar observations were led by scientists
Marina Brozovic and Lance Benner of NASA's Jet Propulsion
Laboratory, Pasadena, Calif. Radar is a powerful technique for
studying an asteroid's size, shape, rotation state, surface
features and surface roughness, and for improving the
calculation of asteroid orbits. Radar measurements of asteroid
distances and velocities often enable computation of asteroid
orbits much further into the future th