Satellites can use laser beams for communication and data transmission to Earth at speeds one million times faster than radio signals.
China has conducted a pioneering high-speed communication experiment using lasers instead of conventional radio signals between satellites in the Beidou Navigation Satellite System and ground stations. This method could allow satellites to transmit data to the ground at speeds of several gigabytes per second. Chinese authorities did not disclose the fastest communication performance achieved by Beidou during the experiment.
The last satellite in the Beidou system launched last year. (Photo: SCMP).
China and the United States are in a fierce race to establish laser communication networks in space. NASA announced on November 29 that after two years of delays, it will launch a test satellite in December to conduct a similar experiment, testing data transmission via laser beams at 2.8 GB/second.
The Beidou satellites typically communicate with users on the ground via radio signals, which can only transmit short text messages due to limited bandwidth. With the support of laser beams, the network can transmit data over a million times faster to almost any location at any time. Laser communication offers broader bandwidth and is less susceptible to eavesdropping or network congestion.
Beidou is the largest global satellite navigation network in the world, comprising more satellites in orbit than GPS. This network provides both positioning and communication services, with widespread applications in both civil and military fields. The Chinese Academy of Sciences announced on November 26 that in the latest experiment, scientists demonstrated that Beidou’s laser signals could transmit stably in challenging environments such as cities, where establishing and maintaining light communication over long distances is difficult due to atmospheric disturbances. The institute did not disclose where the experiment took place.
A ground station for laser communication is typically a fixed facility with complex equipment including large telescopes, tracking and beam-locking devices, and signal processing equipment. However, Chinese scientists and engineers have integrated everything into a vehicle for mobile deployment, according to the project team from the Institute of Optics, Mechanics, and Physics in Changchun, Jilin Province, northeast China.
The bandwidth of the laser beam can reach one terabyte (1,000 GB) per second. Conventional communication satellites are often bulky due to the need for large antennas and substantial power supplies to generate and transmit numerous radio signals. Laser equipment is smaller and lighter, allowing satellites to be primarily designed for other purposes to establish high-speed communication.
The idea of using laser communication satellites originated in the 1960s. The United States, Japan, and several European countries have conducted various research programs to develop the technology but have been unable to resolve several related issues. One major challenge is the atmosphere, where gas molecules can absorb or reflect light, resulting in very few light particles reaching the ground station. Disturbances can also distort or shake the laser beam to the point where the light signal becomes too faint to read, especially in urban areas.
China entered the race in the late 1990s, but collaborative efforts from research institutes have yielded solutions. A research team in Shenyang reported that they developed a telescope mirror that can change shape using electrical currents to reduce the blurring effects caused by atmospheric disturbances.
In recent years, the Chinese space agency has announced plans to launch a large number of small communication satellites into low Earth orbit. While SpaceX’s Starlink satellite constellation provides internet connectivity with bandwidth limited to 200 MB, China’s network will use laser technology to increase speeds at lower costs, according to researchers involved in the program.
