The Chang'e-4 lunar probe will undertake the first ever soft landing on the far side of the Moon. However, direct communication with the far side of the Moon is not possible, which is one of the many challenges of the Chang'e-4 lunar probe mission.
The relay satellite, named Queqiao, will be responsible for transmitting signals between the Earth station and the Chang'e-4 lander and rover.
Relay satellites are communication satellites that can provide data relay and monitoring services for spacecraft, improving the efficiency and emergency capability of various satellites. They also enable data from earth resource and environmental satellites to be transmitted in real time.