HELSINKI — Chinese researchers are proposing to combine separate Earth and lunar orbit relay systems to reduce risks and uncertainty associated with relying on ground stations in other countries.
China is leading a project known as the International Lunar Research Station (ILRS) which aims to establish a base near the lunar south pole in the 2030s. The plan includes establishing a Queqiao (“Magpie Bridge”) relay system in lunar orbit to facilitate communications between the Earth and moon.
An article published in the Chinese Journal of Space Science notes that, due to the rotation of the Earth and orbit of the moon, domestic ground-based deep space stations can only communicate intermittently with the Queqiao lunar relay satellites. Deep space stations in other countries, such as the Neuquén ground station in Argentina, can greatly improve communication conditions.
However, the article also notes that while establishing stations in other parts of the world could mitigate this issue, it introduces risks related to international relations, political stability, and security. “Once astronauts are stationed at international lunar research stations and lunar bases, this risk cannot be ignored.”
The researchers, variously belonging to the Beijing Telemetry Technology Research Institute, Beijing Tracking and Communication Technology Research Institute, and Beihang University, thus propose linking the Queqiao satellites—a pair of which have already supported two lunar far side missions—with China’s Tianlian communications satellites stationed in geosynchronous orbit.
Tianlian satellites are a critical component of China’s space infrastructure. Three Tianlian satellites positioned at 120 degrees from each other in geostationary orbit provide reliable, real-time global telemetry and data relay services for satellites, spacecraft and the Tiangong space station. Tianlian satellites do not currently utilize inter-satellite links.
“To ensure continuous, seamless communication between the ILRS and China’s ground control center, it is necessary to integrate the lunar relay and Tianlian relay satellites, forming a dual satellite relay system,” the article reads.
Simulations state that Tianlian currently could provide a coverage rate for Queqiao of 75%. To achieve continuous coverage, it proposes installing additional antennas on future Tianlian satellites to enhance their capability to communicate with lunar relay satellites. A fourth Tianlian satellite would also be required to boost coverage.
The dual relay system, if realized, would include integrated communication terminals on both the lunar Queqiao and Tianlian relay satellites. The moves would however constrain the resources of the Tianlian satellites for their current uses.
The proposed dual satellite relay system would significantly enhance the reliability and continuity of communication between the ILRS and Earth’s ground stations, the authors claim, ensuring seamless connectivity for crewed deep space missions and boosting the overall robustness and effectiveness of China’s space exploration infrastructure. It could also serve as a precursor to providing global coverage and high-speed communication for cislunar space.
It is notable however that the proposal is somewhat implicitly critical of the international aspect of the planned ILRS, pushing for domestic control over communications. China has signed memorandums of understanding with countries in Asia, Europe and Africa, as well as Venezuela and Nicaragua in the western hemisphere.
China’s ground stations aboard, such as Neuquén, have attracted attention as potentially dual-use. Meanwhile, China lost use of a ground station in Kiribati in the central Pacific Ocean in 2003 when the island country recognized Taiwan. The country however restored relations with China in 2019. Such incidents likely inform the thinking of the researchers. China also relies on Yuanwang tracking ships to support launches, rather than an extant network of international ground stations.
China meanwhile has an established and growing ground station network spanning the geographical reaches of the country.
It is planning a Queqiao constellation to provide lunar comprehensive navigation and communication services for the country’s lunar exploration exploits. A pair of pathfinder satellites, named Tiandu-1 and Tiandu-2, launched along with Queqiao-2 earlier this year.
A proposed first phase would establish satellites in elliptical frozen orbits (ELFO) around the moon. A second phase would see further ELFO satellites and spacecraft at Earth-moon Lagrange points 1, 2, 4 and 5, a near-rectilinear halo orbit (NRHO), and a spacecraft in geostationary orbit, termed a cislunar space station. A third and final phase would add satellites in existing and new distant retrograde orbits (DRO).
China plans to launch precursor ILRS missions to the lunar south pole in the coming years. The multi-spacecraft Chang’e-7 mission is scheduled to launch in 2026, with the in-situ resource utilization test mission Chang’e-8 to launch two years later.
