China Gets Ready to Launch World’s First Lunar Farside Lander

China Gets Ready to Launch World’s First Lunar Farside Lander

China officially announced today that it will launch Chang’e-4 on Saturday, Beijing time (Friday afternoon, Eastern Standard Time).  It will be the first spacecraft to land on the far side of the Moon, which always points away from Earth, meaning that mission controllers will not be able to communicate with it directly.  China launched a communications relay satellite, Queqiao, earlier this year.

Chang’e-4 was built as a backup to Chang’e-3, which successfully landed on the near side of the Moon in 2013 and deployed a small rover, Yutu.  Although Yutu experienced mechanical difficulties that ended its roving days early, China considered the mission sufficiently successful to assign Chang’e-4 to a more risky task of exploring the far side.

Chang’e is China’s mythological goddess of the Moon.  Yutu is her pet jade rabbit.

Orbiting spacecraft, including NASA’s Lunar Reconnaissance Orbiter (LRO), have extensively imaged the far side, but no spacecraft has set down there yet.

Mosaic of the lunar farside as imaged by the Lunar Reconnaissance Orbiter Camera (LROC)/Wide Angle Camera (WAC). Released in 2011.  LROC WAC orthographic projection centered at 180° longitude, 0° latitude. Credit: NASA/Goddard/Arizona State University

Geologists point out how different the far side is from the near side, with fewer maria (“seas” of cooled lava) and more impact craters.  Why the two sides are so different is still being debated.

CGTN tweeted today that the Chang’e-4 launch is scheduled for December 8 along with a video of some of the experiments it will conduct.

It did not mention the time, but Andrew Jones of closely follows the Chinese space program and has been reporting on Chang’e-4’s upcoming launch for several months. He tweeted that the launch will be at 02:30 December 8 in China, which is December 7, 18:30 Universal Coordinated  Time (UTC), or December 7, 2:30 pm Eastern Standard Time.

Like Chang’e-3, Chang’e-4 also has a rover.  Jones reports that a public naming contest was held for the rover (as it was for Yutu), but the name has not been announced yet.

China’s Xinhua news agency published an illustration of the rover in August.  The six-wheeled rover is 1.5 meters long, 1 meter wide, and 1.1 meters high. Although it looks very similar to Yutu, its chief designer, Wu Weiren, told Xinhua that adjustments were made for the different terrain on the far side and the need to communicate through the Queqiao relay satellite.

Illustration of the Chang’e-4 rover. Credit: Xinhua, Aug. 15, 2018.

Among the instruments on the rover are cameras, a visible/near-infrared imaging spectrometer, and a ground-penetrating radar.  Several international payloads also will be aboard including a Dutch low-frequency spectrometer, a Swedish advanced small analyzer to study the interaction between the solar wind and the lunar surface, and a German neutron dosimeter to measure radiation at the landing site.

It will also carry a “lunar mini biosphere” — a tin with potato and arabidopsis seeds and silkworm eggs — designed by university students.

The plan is to land in the South Pole Aitken Basin, a site of considerable scientific interest.  It is the oldest, largest and deepest impact basin on the Moon.  It stretches across a quarter of the Moon and is 8 kilometers deep.  Instruments on U.S. and Indian spacecraft have confirmed that water ice exists in permanently shadowed craters at both of the Moon’s poles, deposited by impacts from comets and asteroids over eons and preserved in the darkest and coldest locations.

Writing for The Planetary Society’s magazine, Long Xiao, a Chinese planetary geologist, identified the planned landing coordinates as “the floor of the Von Kármán crater in its southern portion (45°S – 46°S, 176.4°E – 178.8°E).”

As the number indicates, this is China’s fourth lunar probe.  The first two were orbiters, and the second two landers/rovers.  The next in the series, Chang’e-5, is a lunar sample return mission.  Its launch has been delayed by the 2017 failure of the Long March 5 rocket, which it needs to reach the Moon.  The Long March 5 return-to-flight had been expected earlier this year, but no firm date has been announced yet.

If successful, China would become the third country to return samples from the Moon.  The U.S. Apollo astronauts brought back 380 kilograms of lunar samples from the six missions that landed between 1969 and 1972.  The Soviet Union returned about 330 grams with three robotic Luna missions from 1970-1976.

If Chang’e-4 succeeds, however, China will get a first of its own — the first country to land on the lunar farside.

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