The rollout of the Long March 8 Y3 rocket to launch the Queqiao-2 lunar relay satellite, March 17, 2024. Credit: Ourspace

HELSINKI — China is set to launch its Queqiao-2 communications relay satellite to support upcoming moon missions late March 19.

A Long March 8 rocket was vertically transferred to a launch pad at Wenchang Satellite Launch Center early March 17. The rocket will launch Queqiao-2 towards the moon in preparation for the Chang’e-6 lunar far side sample return mission in May.

Queqiao-2 has a mass of 1,200 kilograms and is equipped with a 4.2-meter parabolic antenna. Its elliptical orbit will allow it to maintain communication with both Earth and lunar far side, which never faces the Earth.

The satellite has a mission lifetime of over eight years. It is intended to support not only Chang’e-6 but also the later Chang’e-7 and Chang’e-8 missions to the lunar south pole.

Chinese authorities have not openly announced a time and date for launch, but airspace closure notices reveal two launch windows. These are 8:21-8:47 p.m. and 9:45-10:16 p.m. Eastern March 19 (0021-0047 and 0145-0216 UTC, March 20).

Queqiao-2 is intended to enter a highly elliptical, frozen lunar orbit inclined by 55 degrees. The satellite will make its closest approach to the moon at roughly 300 kilometers altitude while over the northern hemisphere. It will then head out to an apolune, or farthest point from the moon, of 8,600 kilometers. 

The moon is tidally locked to the Earth, meaning that one hemisphere of the planetary body always faces our planet. Queqiao’s orbit will see it have line of sight to both Chang’e-6—which is targeting Apollo crater in the southern hemisphere of the far side—and Earth for a large portion of its orbital period.

Queqiao-2 will use X and UHF bands to communicate with Chang’e spacecraft, and S and Ka-bands for communications with Earth. It features multiple data rates and reconfigurable software.

China conducted its first lunar sample return mission, Chang’e-5, in 2020. That mission saw 1,731 grams of nearside lunar material delivered to Earth after a complex, 23-day, four-spacecraft operation.

Chang’e-6 will likewise attempt to grab up to 2,000 grams of material, this time from the lunar far side, requiring the support of Queqiao-2. Analysis of far side samples could provide new insights into why the two lunar hemispheres differ. It could also reveal clues as to the history of the Earth-moon system.

Queqiao-2, or “Magpie Bridge-2”, is a more capable follow-up to Queqiao, launched in 2018. That satellite facilitated the Chang’e-4 mission—the first-ever lunar far side landing. The aging, first relay satellite remains operational in a halo orbit around the Earth-moon Lagrange point L2. This is situated roughly 70,000 kilometers beyond the moon.

Queqiao-2 also carries payloads as part of the science objectives of the 2026 Chang’e-7 mission. These are an extreme ultraviolet camera, an array neutral atom imager and an Earth-moon length baseline very long baseline interferometry (VLBI) experiment.

Also aboard the launch will be small, experimental satellites Tiandu-1 and Tiandu-2. These will fly in formation in lunar orbit and conduct tests for navigation and communications technology verification. Tests will include satellite-to-ground laser ranging and inter-satellite microwave ranging methods.

The objective of the Tiandu satellites is to inform the design of China’s proposed Queqiao lunar navigation and communication constellation.

The launch of Queqiao-2 follows the apparent loss of a pair of satellites intended to enter lunar distant retrograde orbit. The DRO-A/B satellites launched on a Long March 2C rocket from Xichang spaceport. The mission’s YZ-1S upper stage suffered a malfunction, currently thought to have left the satellites in low Earth orbit. 

The launch will be just the third for the 50.3-meter-long Long March 8 rocket. It flew for the first time in 2020, before setting a then-national record for satellites on a single launch in early 2022.

The Long March 8 combines the 3.35-meter-diameter new-generation Long March 7 kerosene-liquid oxygen first stage with a 3-meter-diameter liquid hydrogen-liquid oxygen second stage from the older Long March 3A series. An upgraded version of the rocket is slated to fly for the first time from a new, commercial launch site near Wenchang spaceport in the coming months.

Andrew Jones covers China's space industry for SpaceNews. Andrew has previously lived in China and reported from major space conferences there. Based in Helsinki, Finland, he has written for National Geographic, New Scientist, Smithsonian Magazine, Sky...