Leonard David's INSIDE OUTER SPACE

Credit: CNSA/CLEP

China’s Chang’e-4 successfully has made a 12 minute high dive onto the Moon’s farside.

According to the state-run Xinhua news service, Chinese space experts chose the  Von Kármán crater in the South Pole-Aitken Basin as the landing site of Chang’e-4 on January 3, local time.

The area available for the landing is only one eighth of that for Chang’e-3 that landed on the Moon’s nearside in December 2013.

Von Kármán crater is surrounded by mountains as high as 6 miles (10 kilometers).

Credit: NASA/GSFC/Arizona State University

Vertical landing

“Unlike the parabolic curve of Chang’e-3’s descent trajectory, Chang’e-4 made an almost vertical landing,” said Wu Weiren, chief designer of China’s lunar exploration program. “It was a great challenge with the short time, high difficulty and risks,” Wu said.

On autopilot, Chang’e-4 made the touchdown, with the Queqiao relay satellite in an L2 halo orbit transmitting images of the landing process back to Earth.

“We chose a vertical descent strategy to avoid the influence of the mountains on the flight track,” said Zhang He, executive director of the Chang’e-4 probe project, from the China Academy of Space Technology.

Chang;e-4 en route to farside landing.
Credit: CNSA/CLEP

Safe site

Li Fei, one of the designers of the lander, said when the process began, an engine was ignited to lower the craft’s relative velocity from 1.7 kilometers per second to close to zero, and the probe’s attitude was adjusted to face the Moon and descend vertically.

When it descended to an altitude of about 1.2 miles (2 kilometers), Chang’e-4’s cameras took pictures of the lunar surface so the probe could spot large obstacles such as rocks or craters, said Wu Xueying, deputy chief designer of the probe.

At 328 feet (100 meters) above the surface, the lander hovered to identify smaller obstacles and measure the slopes on the lunar surface, Wu said.

Chang’e-4 lander deploys lunar rover. Credit: CCTV/Screengrab/Inside Outer Space

After calculation, the probe found the safest site, and continued its descent. When the craft was 7 feet (2 meters) above the surface, the engine stopped, and the spacecraft landed with four legs cushioning against the shock, reports Xinhua.

Post-landing

After landing, the solar panels and antennas on the probe were unfolded under the control of the space engineers in Beijing through the communication transmission of the relay satellite, which was operating in the halo orbit around the second Lagrangian point of the earth-moon system, about 65,000 km from the Moon, where it can see both the Earth and the Moon’s farside.

The first close-up photo of the Moon’s farside, taken by a monitoring camera on the lander at 11:40 a.m., showed the direction the rover would drive on to the lunar surface, reported Xinhua.

The control center in Beijing will choose a proper time to let the rover separate from the lander, according to the China National Space Administration (CNSA).