Three satellites successfully enter lunar orbit

Status of two others to be used in future moon missions remains unclear

Three Chinese satellites have successfully entered lunar orbit, while the status of two others remains unclear after apparent rescue efforts.

The Queqiao-2 communication relay satellites, which began their journey from Wenchang Satellite Launch Centre last week, arrived at 440km above the moon’s surface early on Monday morning, according to the China National Space Administration (CNSA).

Following a 19-minute-long braking burn which began at 12.46am, the spacecraft slowed, was caught by the moon’s gravity and entered a highly elliptical lunar orbit, the administration wrote on its website. Two smaller satellites, Tiandu-1 and Tiandu-2, which lifted off along with Queqiao-2 to test lunar navigation technologies, also successfully performed braking and entered lunar orbit on Monday. They will separate later, according to CNSA.

Meanwhile, there have been no official updates on the status of DRO-A/B satellites, which failed to reach their designated altitude because of an upper-stage rocket issue after taking off from Xichang Satellite Launch Centre on March 13. “The satellites have not been inserted into their designated orbit, and work is under way to address this problem,” Xinhua reported at the time.

The US satellite catalogue showed the pair had raised their orbit from 524 x 132,577km to 1164 x 243,691km after the incident.

“This suggests to me that the DRO satellites are still trying to get to the moon,” said Jonathan McDowell, a Harvard astronomer who tracks rocket launches and activity in space.

DRO-A/B were planned to enter a so-called distant retrograde orbit, or DRO, of the moon. From there, they would work with DRO-L – a third satellite placed into low-Earth orbit last month – to test laser-based navigation technologies between Earth and the moon.

The apparent orbital climb, which probably cost considerable satellite propellant, still could not inject the pair directly into a moon-bound trajectory, said amateur astronomer Scott Tilley, who is based in British Columbia, Canada.

“Getting the objects into a high-Earth orbit and raising the perigee as they have done would allow them time to consider their options of getting them to the moon. At this stage, an entirely different trajectory plan would be needed to get the spacecraft to the moon or a DRO,” said Tilley, who helped Nasa find one of its long-lost satellites in 2018.

Assuming the pair still had enough fuel, it might be possible to come up with a special trajectory and even recover the mission, he said.

In the next few days, Queqiao-2 will make further adjustments to enter a 24-hour-period final orbit, which is highly stable and will require little maintenance during its eight years of operation, according to CNSA.

From there, the 1.2kg relay satellite will use its 4.2m-wide radio antenna to conduct communication tests with the Chang’e 4 spacecraft, which has been carrying out scientific research in the Von Karman crater on the moon’s far side since 2019.

Like its predecessor Queqiao, which has been supporting Chang’e 4 for more than five years, Queqiao-2 allows communications between Earth and the dark side of the moon which constantly faces away. It also helps devices on the lunar surface talk to each other, such as between a lander and a rover.

Queqiao-2 paves the way for China’s coming Chang’e 6 mission, which is set to launch in May.