China said it succeeded in two-way laser communications between Earth and the moon at a distance of more than 400,000 kilometers. The download speed from the moon to Earth reached up to 100 Mbps (megabits per second).
China Central Television (CCTV) reported on the 31st, citing the Space Application Engineering and Technology Center of the Chinese Academy of Sciences, that it succeeded in two-way communications consolidation in a recent Earth-moon laser communications experiment.
Laser communications is a technology that uses light to send and receive data instead of conventional radio waves. It can use wide bandwidth, enabling fast transmission speeds, and it has the advantage of precisely setting the communication direction. However, as the distance increases, signals weaken and are affected by atmospheric refraction, making technology to align exact transmit-and-receive points important.
According to CCTV, the research team developed technology that allows a spacecraft and a ground telescope to track each other even while moving, taking into account satellite orbit and ground telescope installation errors, atmospheric refraction, and the time it takes for the laser to travel.
To capture laser signals that weaken over long distances, the research team also applied a high-sensitivity detector capable of sensing single photons and an algorithm that distinguishes faint signals.
CCTV said the upload speed for sending data from Earth toward the moon in this experiment was 1.25 Mbps, and the download speed from the moon to Earth was 100 Mbps. It added that a file of an 8K-resolution image of the lunar surface, which takes 4 to 5 minutes to transmit via conventional microwave communications, can be downloaded in about 12 seconds using 100 Mbps laser communications.