Keeping Track

This giant radio dish at Goldstone, California, will track asteroid DA14 as it retreats from Earth February 16-20. The antenna is part of NASA's Deep Space Network, which communicates with spacecraft that are far from Earth, from the Messenger orbiter at Mercury to the Voyager probes at the edge of the solar system. The radio antenna, which spans 230 feet (70 meters), will act as a radar gun, emitting pulses of radio waves and tracking their echo off the asteroid, which is about 150 feet (45 meters) in diameter. Combined with other observations, that should reveal details about the asteroid's composition, mass, and rotation, as well as the subtle effects of solar radiation on its path around the Sun. The antenna couldn't track the asteroid on its in-bound path to Earth because DA14 was too far south. [NASA/JPL]