According to WeDoAny.com, sourced from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences, China has recently made a major breakthrough in the Earth-Moon laser communication test mission, successfully establishing a two-way laser link over a distance exceeding 400,000 kilometers between Earth and the Moon, achieving the first two-way high-speed laser communication between the two. This marks the official transition of China's space laser communication from low-Earth orbit to cislunar space.
Two-way high-speed laser communication between Earth and the Moon
What technical challenges need to be overcome?
Space laser communication is a communication method that uses lasers to transmit information, offering advantages such as large bandwidth, high speed, precise directionality, and strong confidentiality. However, the greater the distance, the greater the technical challenges.
It is understood that several major challenges have long persisted in the field of deep-space laser communication: distances spanning hundreds of thousands of kilometers make precise beam alignment extremely difficult; signals arriving at the ground are so weak they are nearly undetectable; and transmission speeds are difficult to increase.
To address the alignment problem, the research team devised a novel approach: comprehensively accounting for factors such as satellite orbits, telescope installation errors, atmospheric refraction, and laser flight time, they ensured that the satellite in orbit and the ground telescope remain continuously aligned during motion, guaranteeing that the laser precisely hits the intended position. This is akin to threading an extremely fine beam of light through a high-speed moving "pinhole" from 400,000 kilometers away.
How was the weak signal problem solved? The researchers used an "ultra-sensitive detector" capable of detecting individual photons and developed a complex signal recognition algorithm to "fish out" valid signals from massive amounts of noise. This is like accurately hearing the sound of a needle dropping in a bustling, noisy marketplace thousands of miles away.
The final hurdle was increasing transmission speed. Through a series of technical breakthroughs, the research team significantly improved data processing efficiency. This test initially achieved communication rates of 1.25 Mbps (megabits per second) on the uplink and 100 Mbps on the downlink. To transmit a high-definition 8K image of the lunar surface, a traditional microwave downlink would take approximately 4 to 5 minutes, whereas switching to 100 Mbps laser communication would take only about 12 seconds.
These related technological breakthroughs have officially advanced China's space laser communication from low-Earth orbit to cislunar space, providing important technical support for China's crewed lunar landing, lunar research station construction, and deep-space exploration.