China’s Mission to the “Dark Side” of the Moon

On January 03, China successfully landed a robotic spacecraft – Chang’e-4 – on the far side of the Moon, the first ever such attempt and landing. Named after the mythical moon goddess Chang’e, the Chang’e-4 mission will test plant growth and listen for radio emissions normally blocked by Earth’s atmosphere.

Chang’e-4 landed in a vast impact region measuring some 2,500km in diameter and 13km in depth, and it is the single-largest impact basin on the Moon and one of the largest in the Solar System.

Because the Moon rotates around its axis at the same speed as it orbits the Earth, we never see the far side from the ground. The lack of direct sight means the mission requires a relay satellite to enable communications between Earth-based mission control and the spacecraft. A relay satellite, named Queqiao, was launched in May 2018 to transmit signals.

There have been numerous missions to the Moon in recent years, but the vast majority have been to orbit, fly by or impact. The last crewed landing was Apollo 17 in 1972.

The Chang’e-4 lander carries three scientific payloads, respectively, developed by the Netherlands, Sweden and Germany.

Dutch-Chinese low-frequency radio spectrometers on the lander and relay satellite will observe 21-cm hydrogen line radiation and study how the universe emerged after the Big Bang. Radio and television signals blight earth-based attempts to see these faint 21-cm signs from the Cosmic Dawn – the far side of the Moon offers shelter from these transmissions.

Chang’e-4’s rover carries a small advanced analyser for neutrals, developed in Sweden, to study the interaction between solar winds and the moon surface.

A German-developed neutron and radiation dose detector on the lander will measure radiation levels – crucial for long-term human occupation of the Moon. China ultimately hopes its efforts will lead to a crewed lunar landing, the first since NASA’s Apollo programme ended in 1972.