China has made significant strides in its lunar exploration program, with a key component being the development and deployment of lunar relay satellites. These specialized satellites play a crucial role in facilitating communication between Earth and spacecraft operating on the far side of the Moon, which is perpetually turned away from Earth.
The Queqiao Relay Satellite
In 2018, China launched the Queqiao relay satellite, also known as Magpie Bridge, to support the historic Chang’e-4 mission, which achieved the first-ever soft landing on the far side of the Moon. Queqiao was placed in a halo orbit around the Earth-Moon L2 Lagrangian point, about 65,000 kilometers (40,000 miles) beyond the Moon. This strategic position allowed Queqiao to maintain a direct line of sight with both the Chang’e-4 lander and rover on the lunar far side and Earth, enabling continuous communication and data transmission.
The Queqiao satellite, weighing around 400 kilograms (880 pounds), carried several antennas, including a 5-meter (16.4-foot) diameter umbrella-shaped antenna, which was the largest communication antenna ever used in deep space exploration at the time. This advanced technology overcame the challenge of direct communication between Earth and the far side of the Moon, which is blocked by the Moon’s bulk.
The Queqiao-2 Relay Satellite
Building on the success of Queqiao, China launched the more capable Queqiao-2 relay satellite in March 2024. Weighing 1,200 kilograms (2,646 pounds) and equipped with a 4.2-meter (13.8-foot) parabolic antenna, Queqiao-2 is designed to support China’s upcoming lunar missions, including the Chang’e-6 far side sample return mission and the Chang’e-7 and Chang’e-8 missions to the lunar south pole.
Queqiao-2 was launched aboard a Long March 8 rocket and entered a highly elliptical, frozen lunar orbit inclined by 55 degrees. This orbit allows the satellite to maintain line of sight with both the lunar far side and Earth for a significant portion of its orbital period, enabling continuous communication and data relay.
In addition to its communication capabilities, Queqiao-2 also carries scientific payloads, such as an extreme ultraviolet camera, an array neutral atom imager, and an Earth-moon length baseline very long baseline interferometry (VLBI) experiment. These instruments will contribute to the scientific objectives of the Chang’e-7 mission.
Future Lunar Relay Constellation
China’s ambitions for lunar exploration extend beyond the current relay satellites. The country is working towards establishing a Queqiao lunar navigation and communication constellation. This proposed system would consist of multiple satellites stationed in various orbits around the Moon, including circumlunar space, Earth-Moon Lagrange points, and potentially interplanetary staging stations.
The Queqiao constellation aims to provide comprehensive communication, navigation, and remote sensing support for future lunar surface operations, including the planned International Lunar Research Station (ILRS) project. This infrastructure would not only facilitate China’s lunar endeavors but could also potentially support missions from other countries exploring the Moon and beyond.
China’s development of lunar relay satellites and the proposed Queqiao constellation demonstrates the country’s commitment to advancing its lunar exploration program and establishing a sustained presence on the Moon. These efforts are paving the way for future scientific discoveries, resource utilization, and potential human exploration of Earth’s natural satellite.
