China to build space-ground monitoring network for asteroid defense

China to Build Space-Ground Monitoring Network for Asteroid Defense

China is working on a space-ground integrated monitoring and early-warning network as a core component of a planetary defense system, according to a scientist familiar with the plan. The network will combine ground-based telescopes with a space-based monitoring constellation to achieve round-the-clock surveillance with no blind spots.

The plan, revealed on International Asteroid Day, aims to address the risks posed by near-Earth asteroids. Li Mingtao, chief scientist at the asteroid monitoring and early-warning research center under the China National Space Administration (CNSA), noted that more than 40,000 near-Earth asteroids have been discovered and cataloged worldwide, but many remain undetected.

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. The ideal sites will have a high clear-sky rate, good astronomical seeing, and high elevation, making remote, sparsely populated areas the most likely locations for the telescopes.

In addition to ground-based telescopes, China also intends to launch a space-based monitoring constellation, free from atmospheric and day-night constraints, specifically targeting threats from the sunward direction. The space-based constellation will complement ground-based telescopes, delivering seamless, all-sky monitoring with no blind spots.

The network's priority will be to detect yet-undiscovered near-Earth asteroids, particularly those around 140 meters in diameter, which could destroy a small or medium-sized country. According to Li, only about 45% of these asteroids have been found, leaving more than half remaining undetected.

China has made breakthroughs in models and algorithms for asteroid impact risk analysis and is developing an early-warning system. The system will automatically calculate the orbit and assess the impact probability of a suspicious object detected by a telescope.

Kinetic Impact Demonstration Mission

China is planning a kinetic impact demonstration mission to test the feasibility of defending Earth against potentially hazardous asteroids. The mission will follow a "fly-along–impact–fly-along" model, involving both an observer and an impactor spacecraft. The observer will arrive first to conduct close-up surveys of the target asteroid, collecting detailed physical parameters, while the impactor will strike the asteroid at high speed.

Wu Weiren, chief designer of China's lunar exploration program, explained that the mission aims to change the orbit of a small celestial body and prevent it from hitting Earth again for at least several decades or even 100 years.

International Cooperation

China is calling for global partners to work together to protect the safety of the Earth from an impact event. Wu Weiren emphasized that near-Earth asteroid defense is a shared responsibility for all humanity and that international cooperation is essential. China has proposed a strategic concept for asteroid defense development within the framework of the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS).

The concept covers aspects of monitoring and early warning, in-orbit handling, and systematic response, with the goal of building a comprehensive near-Earth asteroid detection and defense system. China hopes to launch more spacecraft to asteroids to obtain more detailed data and is open to collaborating with other countries on joint ground-based monitoring, development, and payload integration, as well as data and research sharing.