Chinese scientists first turned their attention to asteroids in 1949 and were world leaders at the time.

But "observing near-Earth objects is not a major priority now, so the input is relatively small", Zhao said.

China's lunar probe Chang'e-2 flew 10 million km and conducted the country's first exploration of the near-Earth asteroid Toutatis on Dec 13, making China the fourth country to explore asteroids in space.

But such missions cannot be carried out regularly since there is no national plan and close-up explorations are costly, he said.

So current research on asteroids in China relies mostly on ground-based observation, which costs less and allows scientists to study a large number of asteroid samples, he said.

More than 400 observation stations across the globe are doing research and contributing to asteroid research goals set by NASA.

NASA set a 10-year goal in 1998 to identify and catalogue the orbital characteristics of 90 percent of near-Earth objects larger than 1 km. It set another 20-year goal in 2005 to detect 90 percent of near-Earth objects with a size greater than 140 meters in diameter starting in 2008. The data from the research were shared internationally.

China's few asteroid researchers are contributing to the efforts.

A Schmidt telescope with a 1-meter aperture was put into use in 2006 at Purple Mountain Observatory, which has found more than 1,200 asteroids so far.

Zhao is preparing for a project that aims to use an optical telescope and observe the rotation periods of several thousands asteroids within a few years, which he hoped would be useful for possible future close-up asteroid exploration missions.

"Knowledge gained from ground observation will be important information for deep-space exploration projects, because it could be very dangerous for explorers to get close to asteroids if the designers lack knowledge about things such as how an asteroid circles in an orbit and how it rotates," he said.

But if China needs to learn more about asteroids, the country's "not-so-advanced" ground observation capability will need to be improved, he said.

The observatory's Near-Earth Objects Survey Telescope is the largest of its kind in China and the most advanced in Asia, but it is only a small to medium telescope globally, he said.

Relatively large Schmidt telescopes, those having a 1-meter aperture or larger, have been in use since the 1940s. Between 1945 and 1980, eight telescopes of this kind were built worldwide. The Karl Schwarzschild Observatory in Germany has a 2-meter Schmidt telescope, the world's largest.