RESEARCHERS have completed a laser communications test between Earth and the Moon, successfully verifying two-way high-speed laser link capabilities in orbit, according to the Technology and Engineering Center for Space Utilization (CSU) of the Chinese Academy of Sciences.

After more than a year of in-orbit testing, the team established a two-way laser communication link across a distance of over 400,000 km, marking the expansion of China’s space laser communications from near-Earth orbit to deep space.

Compared with traditional microwave communications, laser communications offer faster speeds, greater bandwidth, stronger security and more compact hardware. However, enabling laser communications across the Earth-Moon distance required overcoming three major challenges: beam alignment, signal weakness and transmission speed.

The team developed an innovative acquisition and tracking scheme that integrates corrections for orbital, atmospheric, and optical propagation delays, enabling ground and spaceborne equipment to maintain precise alignment while in motion.

After traveling 400,000 km back to Earth, the laser signal becomes so faint that ground telescopes receive only a few photons at a time. Moonlight, starlight and urban lighting add further interference — akin to hearing the sound of a falling pin in a bustling market, the CSU said.

The researchers developed high-speed superconducting single-photon detection technology and high-sensitivity algorithms to extract valid communication signals from background noise.

To tackle the speed bottleneck, the team developed high-bandwidth signal processing technology and adopted special coding schemes to counter noise. The test achieved two-way communication rates of 1.25 Mbps uplink and 100 Mbps downlink.

(Xinhua)