BEIJING, July 1 (Xinhua) -- China is working on a space-ground integrated monitoring and early-warning network as a core component of a planetary defense system that is under feasibility study, according to a scientist familiar with the plan.
Li Mingtao, chief scientist at the asteroid monitoring and early-warning research center under the China National Space Administration (CNSA), made the revelation on Tuesday, the International Asteroid Day designated by the United Nations to raise global awareness about asteroid impact hazards and promote planetary defense education.
Li noted that the network will combine ground-based telescopes with a space-based monitoring constellation to achieve round-the-clock surveillance with no blind spots.
By now, more than 40,000 near-Earth asteroids have been discovered and cataloged worldwide. "No asteroid has so far been identified that will definitely collide with Earth in the foreseeable future, but concerns over impact risks are not unfounded. Many near-Earth asteroids remain undetected," Li was quoted as saying in a report by Science and Technology Daily on Wednesday.
"We must never let our guard down, but there is also no need for excessive anxiety," he added.
On the ground, China will deploy multiple large-aperture optical telescopes at carefully chosen sites, forming a geographically balanced network for long-range, wide-coverage, and precise night-sky surveys, Li said.
Ground telescopes, however, are blinded by the sun's glare due to atmospheric scattering. China also intends to launch a space-based monitoring constellation, free from atmospheric and day-night constraints, specifically targeting threats from the sunward direction.
Through coordinated ground-space operations, the system will achieve seamless day-and-night monitoring, he said.
Early warning time, a key factor in asteroid monitoring, varies dramatically depending on the asteroid's size and when it is discovered, the expert noted.
Larger asteroids, he explained, pose greater potential devastation but are easier to detect early due to their brightness. Smaller asteroids are harder to spot but cause less damage. This disparity underscores the critical importance of building a comprehensive monitoring system that can catch threats as early as possible.
China has already made initial breakthroughs in risk assessment models and algorithms and is developing an operational near-Earth asteroid early-warning system. Once a telescope detects a suspicious target, the system will automatically calculate its orbit and assess impact probability, according to the report.
If a credible and urgent threat is confirmed, authorities will be notified immediately, and the public will receive clear information about the risk and recommended actions, Li said.
Should an asteroid threaten Earth, there are two main countermeasures. The first is kinetic impact, meaning a high-speed strike that instantly shifts the asteroid's orbit. It is simple, reliable, and the most viable option, said Li.
The second includes gravity tractors, ion beams and laser ablation, but these exert very weak forces and require over a decade of advance notice to be effective, he added.
The greatest risk comes from undiscovered near-Earth asteroids, which are numerous, faint, and potentially approaching from the sun. "That is why global scientists are racing to build monitoring and early-warning capabilities and catalog them," he said. ■
