In a few days, China will be back on the moon: a Long March-4C rocket indeed took off on Sunday, May 20, 2018 from the base of Xichang (Sichuan) taking with it the first part of the mission Chang’e 4. It plans to land at the end of the year a lander and a rover on the far side of the moon. A first, if we except the accidental fall of the American Ranger 4 probe in 1962.
At first, the Chinese will install around the Moon a communication satellite, which will relay to Earth the data transmitted from the Moon’s dark side. This satellite was baptized Queqiao (bridge of magpies) in reference to a Chinese myth in which two lovers, separated by the Milky Way, get together every year for a day by a bridge formed by a swarm of magpies. It should reach its destination in 8 to 9 days.
The 425-kilogram spacecraft, developed by the Chinese Academy of Space Technology (CAST), will be installed in a very special orbit, 65,000 km from the Moon, a gravitational and stable region from which it can communicate at once in a continuous way with the stations on the terrestrial ground and the two devices on the hidden face of the Moon. Queqiao should serve in the future to other probes of the international community.
Equipped with a radio antenna developed by the Netherlands, it should also be used for the recording of low-frequency astronomical signals, the same ones that are inaccessible to us from Earth because they are blocked by the atmosphere. This should open up a new window of observation on the planets and the Sun, and allow us to go back in time to this period called the “dark age of the Universe”, before the birth of the stars.
Also on the trip will be two microsatellites developed by the Harbin Institute of Technology. Named Longjiang-1 and Longjiang-2 (river dragon), the twin 45 kg machines will operate in an elliptical orbit ranging from 200 to 9000 km around the Moon. They carry a radio astronomy payload with two low frequency radio astronomy antennas, which will use the moon as a shield to avoid being polluted by the Earth’s radio transmissions.
The second part of the Chang’e 4 mission is expected to leave Earth at the end of the year. It consists of a landing gear and a rover, which were the rescue craft built at the same time as those of the Chang’e 3 mission, which landed successfully on the Moon in 2013. This success allowed the Chinese to imagine a new lunar mission, which must take place in the South-Aitken Pole Basin, the largest basin made by an asteroid impact on the surface of the Moon, and also the biggest in the solar system, with 2,500 kilometers of diameter for about 13 kilometers of depth. An intriguing region that should give scientists the opportunity to study better the history of our moon.