Satnews Daily
December 10th, 2018

China's Chang'e-4 Mission Successfully Launched from Xichang Satellite Launch Center

China launches Chang'e-4 lunar probe in the Xichang Satellite Launch Center in southwest China's Sichuan Province, Dec. 8, 2018. Photo is courtesy of Xinhua/Jiang Hongjing.

China's Chang'e-4 lunar probe was launched in the early hours of Saturday, according to XinhuaNet's infosite, and it is expected to make the first-ever soft landing on the far side of the moon.

A Long March-3B rocket, carrying the probe including a lander and a rover, blasted off from the Xichang Satellite Launch Center in southwest China's Sichuan Province at 2:23 a.m., opening a new chapter in lunar exploration.

As the moon's revolution cycle is the same as its rotation cycle, the same side always faces the Earth. The other face, most of which cannot be seen from Earth, is called the far side or dark side, because most of it remains unknown. The Chang'e-4 mission will be a key step in revealing the mysterious far side of the moon.

"The soft landing and exploration of the far side, which has never been done before, will gain first-hand information about the terrain and lunar soil components and other scientific data, which will help enrich our understanding of the moon and the universe," said Zhang He, Executive Director of the Chang'e-4 probe project.

The scientific tasks of the Chang'e-4 mission include low-frequency radio astronomical observation, surveying the terrain and landforms, detecting the mineral composition and shallow lunar surface structure, and measuring the neutron radiation and neutral atoms to study the environment on the far side of the moon, the China National Space Administration (CNSA) announced. Landing and roving on the Moon's far side requires a relay satellite to transmit signals. China launched that relay satellite "Queqiao," meaning Magpie Bridge, on May 21 to establish the communication link between the Earth and the Moon's far side. In orbit, the relay satellite can "see" both the earth and the far side of the moon. The earth's and moon's gravity balances the orbital motion of the satellite and makes it very fuel-efficient.

An artistic rendition of China's Chang'e-4 rover on the surface
of the Moon. Image is courtesy of Xinhua.

The satellite entered a halo orbit around the second Lagrangian (L2) point of the Earth-Moon system, about 455,000 km. from the Earth. This is the world's first communication satellite operating in that orbit, said Zhang Lihua, chief designer of the satellite from the China Academy of Space Technology. A test on the satellite in November showed that it is in good condition, said Zhang.

China has promoted international cooperation in its lunar exploration program, with four scientific payloads of the Chang'e-4 mission developed by scientists from the Netherlands, Germany, Sweden and Saudi Arabia.Three scientific and technological experiments, designed by Chinese universities, will also be carried out during the mission.

No one had ever seen the far side of the moon prior to the Soviet Union land that nation's Luna 3 probe in 1959, which was the first-ever mission to photograph the far side. The United States Apollo 8 mission sent three astronauts to fly around the moon in 1968, the first time that people saw the moon's far side with their own eyes. Remote-sensing images show the far side is thickly dotted with impact craters and has much fewer lunar mares than the near side. Scientists infer that the lunar crust on the far side is much thicker than the near side; however, why that may be so remain a mystery.

This launch was the 294th mission of the Long March rocket series.