Dark side of the moon

China connects to dark side of Moon with satellite launch

Image credit: Dreamstime

China’s space agency has launched a relay satellite in a key step towards the country’s exploration of the dark side of the Moon.

The satellite will be used to establish communications between Earth and a planned lunar probe, which will be used to explore the far side of the Moon: the hemisphere permanently turned away from Earth. Although it remains uncharted compared with the other half of the Moon’s surface, this hemisphere is known to contain many large impact craters.

Among other goals, the China National Space Administration (CNSA) aims to explore this unexplored part of the Moon through the robotic Chinese Lunar Exploration Program (nicknamed the Chang’e Program, after the mythological Moon goddess Chang’e).

China first carried out a successful soft landing on the Moon in 2013 with the Chang’e-3 mission. Now, with the Chang’e-4 mission, CNSA plans to explore the unexplored far side of the Moon.

In a key step for the mission, the approximately 400kg relay satellite was launched by a Long March-4C rocket from the Xichang Satellite Launch Centre in Southwest China. 25 minutes after lift-off, the satellite separated from the rocket and entered an Earth-Moon transfer orbit to unfold its solar panels and communication antennae.

The satellite was named Queqiao (‘Magpie Bridge’). This refers to a tale in Chinese mythology in which a bridge of magpies is formed across the Milky Way to allow a pair of forcibly separated lovers to be reunited once a year.

Mirroring this story, Queqiao will establish a connection across space between CNSA on Earth and the unexplored face of the Moon. This will require the satellite to enter a particular satellite in which both Earth and the far side of the Moon – on which Chang’3-4 will land – are within reach.

Chang’e-4 – which will be launched in approximately six months – will incorporate an orbiter, lander and rover. If all goes according to plan, it will land in the South Pole-Aitken basin, a vast impact crater thought to be one of the largest in the Solar System. Chang’3-4 will be used to help CNSA scientists determine the age and composition of regions of the dark side of the Moon.

“The launch is a key step for China to realise its goal of being the first country to send a probe to soft-land on and rove the far side of the Moon,” said Zhang Lihua, manager of the Queqiao project, in a statement. According to Zhang, the mission still has challenges to face in adjusting its orbit and braking near the Moon.

In addition to casting light on the dark side of the Moon, the mission will enable CNSA to study deep space with instruments well-located for the task in a quiet environment shielded by the moon from interfering signals from Earth. CNSA will use a low-frequency radio spectrometer to observe the birth and evolution of stars and galaxies billions of light years away.

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