China is working on a relay satellite to support lunar polar missions

HELSINKI — China is developing a new lunar relay satellite to support future exploration missions to the south pole of the moon. 

The country is planning to send the Chang’e-7 spacecraft to the lunar south pole around 2024. Objectives include survey the region and seek evidence of water ice using an orbiter, lander, rover and a small hopping probe to investigate shadowed craters.

The mission is one of the first for an initial phase of a proposed joint International Lunar Research Station with Russia and potentially other partners.

A dedicated relay satellite is now being developed to facilitate a link between multiple surface spacecraft at the lunar south pole—the location of which poses line-of-sight issues for communications—and Earth, according to a paper published in Space: Science & Technology.

China currently has a lunar relay satellite stationed in orbit around the second Earth-moon Lagrange point at around 65,000 kilometers beyond the moon. Launched in May 2018, the Queqiao satellite serves a communications relay role that allows the Chang’e-4 lander and rover mission to operate on the far side of the moon. 

The new Chinese lunar relay satellite will inherit a similar, large 4.2-meter-diameter parabolic antenna and the hydrazine propulsion used by Queqiao. It will however have a wet mass of 600 kilograms and thus be more massive than the roughly 450-kilogram wet mass Queqiao. The satellite is designed for a nominal 8-year mission lifetime.

The new satellite will operate in an inclined highly elliptical frozen orbit. It will have a perilune of 300 kilometers and apolune of 8,600 kilometers and an inclination of 54.8 degrees. This will allow communication links for over 8 hours of the roughly 12-hour period orbit.

The relay satellite could launch on a dedicated launcher or as part of the Chang’e-7 stack, according to the paper authored by Zhang Lihua at DFH Satellite Co., Ltd., a satellite-developing arm of the China Academy of Space Technology (CAST). A second relay satellite could be developed if 100 percent coverage is required.

China is planning to follow Chang’e-7 with the Chang’e-8 technology demonstration mission to the lunar south pole later in the 2020s, which is to include in-situ resource utilization and 3D-printing technology tests. The Chang’e-6 lunar sample return is also expected to target the South Pole-Aitken Basin, a vast impact basin extending from Aitken crater at 18 degrees south down to the lunar South Pole, around 2024.

In the long term the paper proposes a future Chinese lunar communication infrastructure in order to cope with an expected increased spacecraft and the needs of human lunar exploration. 

For this the creation of a lunar information network including orbiting and surface elements is proposed, which will also incorporate navigational data. Use of new optical communication technologies for extremely high data rates is also proposed.

Beyond this a “solar system internet, operating like terrestrial internet, to provide network layer services to users” should be developed. It also suggests the system should be an “open, interoperable architecture” in order to “enable any number of national, international, and commercial service providers to offer services.”

China is not the only space actor looking at lunar communications. NASA is in the early phases of a concept called LunaNet that would place a network of satellites around the moon to support the Artemis program and other lunar missions. ESA also recently awarded study contracts for lunar communications and navigation systems for its Moonlight initiative.

Chang’e-7 will also not be the only mission to include a “hopper”. The mini spacecraft will seek to investigate shadowed craters, using a payload named the Water Molecule and Hydrogen Isotope Analyzer.

Last week NASA elected to fund a mini extreme mobility lunar vehicle, Micro-Nova, to be developed in partnership between Arizona State University and Intuitive Machines. The hopping spacecraft will likewise seek to explore permanently shaded regions, launching with the second Nova-C lander to the lunar south pole in December 2022.

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