China announces plan to build early-warning system for dangerous asteroids

China has announced that it wants to develop a "space-ground" asteroid early-warning network, while providing few details on what it could look like. But recent papers and presentations to the United Nations provide clues as to what the country has in mind for planetary defense.The China National Space Administration (CNSA) made the announcement on June 30 — International Asteroid Day — stating plans to construct a coordinated ground-and-space monitoring system for near-Earth asteroi