China has achieved a two-way Earth-Moon laser communication link over a distance exceeding 400,000 kilometers, transmitting data between ground facilities and the DRO-A satellite at 100 megabits per second. The milestone positions China as the second nation to master cislunar optical links, though its data rates trail records set by NASA in 2013.
Bridging the Cislunar Abyss With Laser Light
Chinese scientists have successfully established a bidirectional laser communication link across the 400,000-kilometer abyss separating Earth and the Moon. Announced by the Chinese Academy of Sciences, the experimental setup connects ground equipment with an experimental satellite orbiting in a distant retrograde orbit after over a year of rigorous in-orbit testing.
The system relies on laser beams instead of traditional microwave radio frequencies to transport information. According to the Chinese Academy of Sciences, optical communication offers distinct advantages in speed, bandwidth, directional precision, and reduction in size and mass of the equipment. The setup allows high-resolution images, instrument measurements, and telemetry to travel across deep space without hitting the bandwidth caps that increasingly restrict conventional radio systems.
During the demonstration, the network achieved a downlink speed of 100 megabits per second from the satellite to Earth, and 1.25 megabits per second on the uplink from Earth. At 100 Mbps, an 8K image of the lunar surface can be transmitted in approximately 12 seconds, compared to four to five minutes over a 5 Mbps microwave link.
Overcoming Alignment and Atmospheric Obstacles
Maintaining an optical connection over hundreds of thousands of kilometers required solving formidable technical hurdles. Yang Lei, head of the laser test team at the Technology and Engineering Center for Space Utilization under the Chinese Academy of Sciences, described the engineering feat to CGTN.
At such extreme distances, even a microscopic wobble from the spacecraft or a shimmer in Earth’s atmosphere can deflect a laser beam far off target. To keep terminals aligned, the research team developed a real-time tracking system that calculates satellite orbits, mounting errors, telescope deformations, atmospheric refraction, and the time required for light to travel the distance. Ground stations deployed superconducting single-photon detectors paired with custom noise-resistant coding to isolate useful signals from a chaotic background wash of moonlight, starlight, and city glare.
Infrastructure and Collaboration Across Facilities
The experimental payload on the DRO-A satellite was developed under the leadership of the Center for Engineering and Technology for Space Applications in collaboration with Zhejiang Lab. On the ground, the necessary infrastructure involved the Yunnan Astronomical Observatory and the Shanghai Institute of Microsystems and Information Technology.
Optical links are central to handling the massive data footprint required for lunar habitats, high-definition mapping, and continuous scientific monitoring.
How China’s Speed Compares to NASA’s Historic Benchmark
While China’s achievement marks a significant advance for its space program, space experts note that the data rates remain well behind benchmarks established by the United States over a decade ago. NASA’s 2013 Lunar Laser Communications Demonstration achieved a download rate of 622 megabits per second and an upload rate of 20 megabits per second.
Jonathan McDowell, a London-based space historian and former Harvard astronomer, noted that the Chinese and US experiments are directly comparable, observing that It sounds like China has not yet reached the data rates the US can achieve.
McDowell added that the specific reasons for the performance gap remain unclear.
Globally, optical space communication continues to expand rapidly.
