China's Chang'e 5 robotic lunar probe carried out its second braking maneuver Sunday evening, moving from an elliptical lunar orbit to a near-circular lunar orbit according to the China National Space Administration.
Like the first braking operation on Saturday evening, the latest action was executed by a 3,000-newton-thrust engine on the spacecraft's orbiter, which was activated at 8:23 pm, the administration said in a statement.
The braking operation, a crucial measure for orbital control in lunar missions, is essential to ensuring the spacecraft will be captured by the moon's gravitational field instead of merely flying by the celestial body.
The 8.2-metric ton Chang'e 5 has four components: an orbiter, lander, ascender and re-entry capsule. It is China's largest and most sophisticated lunar probe.
The spacecraft was launched by a Long March 5 heavy-lift carrier rocket early Tuesday morning at the Wenchang Space Launch Center in Hainan province, on the world's first mission to bring lunar samples to Earth since 1976.
Chang'e 5 followed an Earth-moon transfer trajectory for about 112 hours before the braking operation and had performed two orbital corrections, the administration said.
Next, the probe will circle the moon for a certain period, then separate into two parts. The orbiter and re-entry capsule will remain in orbit, and the lander-ascender combination will descend toward the moon's surface.
They will make an engine-assisted touchdown on the moon and later engage in tasks such as using a drill to retrieve rocks from 2 meters beneath the moon's surface and gathering soil from the surface with a mechanical arm.
If everything proceeds smoothly, about 2 kilograms of stones and soil will be collected and packed in a vacuum-sealed metal container inside the ascender.
After two days, when surface operations are completed, a second 3,000-newton-thrust engine on the ascender will lift it to rendezvous and dock with the re-entry module. It will transfer the lunar samples to the module and then undock from it.
The combination of orbiter and re-entry capsule will then return to Earth orbit, where the pair will break up and the re-entry capsule will conduct a series of complicated maneuvers to reach a preset landing site in the Inner Mongolia autonomous region in mid-December.
The entire mission is scheduled take about 23 days, according to the administration.
Considering the highly sophisticated operations required, the Chang'e 5 mission will be more difficult and challenging than previous Chinese lunar expeditions, its designers have said.
If the mission is successful, it will be China's first time retrieving an extraterrestrial substance. It will also make China the third nation, after the United States and the Soviet Union, to bring samples back from the moon.