China is gearing up to attempt the first landing on the far side of the Moon in history.
The Chang'e 4 mission, which includes a lander and a rover but no humans, will blast off on a Long March 3B rocket on Friday at around 1:30 PM ET, or early morning Saturday at China’s Xichang Satellite Launch Center. It will take 27 days for the spacecraft to position itself for its landing sequence. If all goes well, Chang’e 4 will make its historic touchdown in the Von Kármán impact crater during the first week of 2019.
The landing will mark the first time humanity has ever landed anything on the far side of the moon, which is sometimes referred to as the “dark side” of the moon because it’s hidden from Earth, not because it lacks all light. The Moon is tidally locked to Earth, which means that its rotational period of 28 days is the same as its orbital period. The result is that one side of the Moon is always facing Earth. Landing on the near side of the Moon is easy (relatively speaking) because there’s nothing blocking communication signals between the two worlds.
While the far side of the Moon has been imaged by many lunar orbiters—and witnessed by several Apollo astronauts—it has never hosted an operational lander on its surface before.
Chang’e 4 will communicate with Earth through a relay orbiter called Queqiao, which China launched in May. Queqiao is currently located in the L2 Lagrange point, a kind of gravitational parking spot between Earth and Moon, where it can transmit and receive signals between mission control in China and the Chang’e 4 landing site on the far side’s southern hemisphere.
The lander and rover that make up the Chang’e 4 mission are equipped with instruments to study and image this pristine landscape, including cameras, spectrometers, and lunar penetrating radar. Chang’e 4 is also carrying a biological experiment developed by university students. Potato and mustard seeds will be planted in a small protected canister and their growth—or lack thereof—will be monitored.
"We will use a tube to direct the natural light on the surface of Moon into the tin to make the plants grow," said Xie Gengxin, chief designer of the experiment, in an April statement from the Chinese Academy of Sciences. "We want to study the respiration of the seeds and the photosynthesis on the Moon.”
Chang’e 4 is part of a series of Chinese robotic Moon explorers. The Chang’e 3 mission, which also included a rover and lander, became the first operational robot on the Moon in nearly 40 years when it landed in December 2013. China’s lunar exploration program plans to launch Chang’e 5, which would be the first sample-return mission to the Moon since in 1976, in late 2019.
Update: China successfully launched Chang'e 4 in the scheduled launch window.
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