The next phase of China's Moon program began with the launch of a new data relay satellite Monday to link lunar landers and rovers on the far side of the Moon with ground controllers back on Earth.
This launch sent China's Queqiao-2 relay spacecraft toward the Moon, where it will enter an elliptical orbit and position itself for the arrival of China's next robotic lunar lander, Chang'e 6, later this year.
A medium-lift Long March 8 rocket carried the Queqiao-2 spacecraft aloft from the Wenchang launch base, located on Hainan Island in southern China. This was the third flight of the kerosene-fueled Long March 8, one of a new generation of Chinese rockets designed to replace older Long March launcher designs burning toxic propellant.
The Long March 8's upper stage deployed the Queqiao-2 spacecraft less than 30 minutes after liftoff at 8:31 pm EDT (00:31 UTC). Queqiao-2 was expected to unfurl solar panels and carry out a series of thruster firings to guide itself into orbit around the Moon.
Queqiao-2 will maneuver into a stable "frozen" orbit at the Moon, minimizing fuel consumption over the course of its mission. The orientation of Queqiao-2's elongated orbit will allow the spacecraft to loiter for hours over the landing sites Chinese officials have selected for the country's next series of robotic Moon missions.
Two smaller satellites also hitched a ride to the Moon on the Long March 8 rocket. One of these spacecraft is about the size of a kitchen oven, the other roughly the size of a small suitcase. Together, the Tiandu-1 and Tiandu-2 satellites will conduct inter-satellite ranging tests to validate orbit determination techniques. The results from these tests will inform Chinese engineers designing a constellation of data relay and navigation satellites that could be in place in the next decade, sort of like a lunar GPS.
Far-side operations
Scheduled for launch on a heavy-lift Long March 5 rocket in May, Chang'e 6 will be the first Chinese lunar lander to rely on the new data relay satellite. Chang'e 6 will target a landing on the Moon, collect samples, and return them to Earth, repeating the feat China accomplished with the Chang'e 5 sample return mission in 2020.
However, Chang'e 5 landed on the near side of the Moon, with direct line-of-sight communications back to Earth. China's goal for Chang'e 6 is to gather the first rocks from the far side of the Moon and bring them back for detailed examination in labs on Earth. If successful, Chang'e 6 will be the first sample-return mission from the lunar far side, adding a new class of specimens to humanity's inventory of Moon rocks.
In 2019, China accomplished the first soft landing on the far side of the Moon with the Chang'e 4 mission, itself a near-duplicate of Chang'e 3, which landed on the near side of the Moon in 2013. China built the Chang'e 6 spacecraft as a backup for Chang'e 5.
When it landed in 2019, China's Chang'e 4 mission used a previous data relay satellite, Queqiao-1, which launched in May 2018. Weighing more than 2,600 pounds (1.2 metric tons) fully fueled for launch, Queqiao-2 is a larger spacecraft, more than twice the mass of China's first lunar communications relay station.
Queqiao means "magpie bridge," in a reference to Chinese mythology. Its launch Monday marks the start of what Chinese officials call the fourth phase of the country's lunar exploration program. This next set of missions will be the direct precursors to China's first human landing on the Moon, an objective the country's leadership aims to achieve by 2030.
From its position in lunar orbit, Queqiao-2 will connect with landers on the Moon's surface with a dish-shaped antenna with a deployed diameter of nearly 14 feet (4.2 meters). This X-band antenna was folded up against the spacecraft's main body for launch, allowing it to fit inside the Long March 8 rocket's payload fairing.
Queqiao-2 will repackage scientific and engineering data from China's lunar landers for transmission back to ground stations on Earth. It's a two-way relay station, so Queqiao-2 will also forward commands from Chinese ground controllers down to spacecraft on the Moon. There are also scientific sensors flying on Queqiao-2: an extreme ultraviolet camera, a neutral atom imager, and an instrument to support radio astronomy observations.
After Chang'e 6, at least two more Chinese lunar missions will also use relay services provided by Queqiao-2. The robotic Chang'e 7 and Chang'e 8 missions, scheduled for launch in 2026 and 2028, will target landing sites in the Moon's south pole region, where observations from orbit show evidence of water ice locked inside the dark floors of polar craters.
Earlier this year, Chinese scientists announced Chang'e 7 would aim for a precision landing on the illuminated rim of Shackleton Crater, then deploy a flying, or hopping, mini-probe to explore deeper inside the floor of Shackleton Crater. Apart from its stationary landing platform and flying probe, Chang'e 7 also includes an orbiter and a rover.
Chang'e 8, which will also target an unspecified site near the south pole, will be the most complex robotic mission ever to fly to the Moon. It will consist of a lander, rover, and an "operation robot" to perform scientific and technology demonstration experiments. These demonstrations will include experiments on resource utilization, presumably by harvesting soil or water, and testing a "mini-enclosed terrestrial ecosystem" on the Moon's surface, according to a mission overview released by the China National Space Administration.
Leader in lunar infrastructure
While Queqiao-2 is only China's second lunar data relay satellite, the country has a head start in building its lunar infrastructure for the 2020s and 2030s. However, NASA appears to be further along than China in developing rockets, spacecraft, and landers to send astronauts to the Moon's south pole in the US-led Artemis program.
NASA's official schedule shows the first Artemis lunar landing by astronauts in 2026, but it's likely to slip a couple of years.
The US space agency is not developing any lunar data relay satellites on its own. Instead, NASA is relying on commercial companies to build and launch relay stations for future US and international (non-Chinese) landers going to the lunar far side. Intuitive Machines, which last month accomplished the first soft landing on the Moon by a US spacecraft since 1972, is one of the companies designing a lunar data relay network.
With this relay network, Intuitive Machines could provide communications support for its own missions exploring the far side of the Moon or sell its services to other companies and space agencies. The first satellite in Intuitive Machines' data relay constellation is slated to launch late this year.
The European Space Agency and British company SSTL are also partnering on a data relay satellite for the Moon, called Lunar Pathfinder. ESA has an agreement with NASA to launch Lunar Pathfinder on a US commercial rocket in 2026.
March 20, 2024: This story was updated after the launch of China's Queqiao-2 relay spacecraft.
