China's goal is to go where no one has gone before: the far side of the moon.
The rocket carrying the chang 'e-4 lunar lander lifted off from xichang satellite launch center in southern China at 2:23 a.m. local time Saturday (or noon Friday in the U.S.). Chinese authorities did not broadcast the launch, but an unofficial live broadcast recorded near the site showed the rocket rising from the launch pad until its flames became like a star in the night sky.
Nearly an hour later, China's official news agency xinhua reported that chang 'e-4 had been successfully launched.
Exactly when chang 'e-4 will land at its destination -- possibly in early January -- has not yet been announced, but chang 'e-4 will get its first close-up look at a part of the moon that will never be seen from earth's perspective.
What is chang 'e-4?
Chang 'e-4 consists of two main parts: a main lander weighing about 2,400 pounds and a 300-pound lunar rover. By comparison, NASA's Mars opportunity rover weighs about 400 pounds, while curiosity, also on Mars, is much larger, weighing 2,000 pounds.
The spacecraft is largely a replica of chang 'e-3, which landed on the moon in 2013. In fact, chang 'e-4 was built as a backup in case the first attempt failed. With the success of chang 'e-3 -- the first soft landing on the moon since 1976 -- the Chinese equipped chang 'e-4 with different instruments and decided to send it to different locations.
Where is chang 'e-4 going?
The rover will land in the 110-mile-wide VonKarman impact crater. It is on the far side of the moon, which is always away from the earth. (the moon's rotation around the earth is "tidally locked," according to planetary scientists. That is, its own rotation period -- its day -- is the same as the time it takes to orbit the earth.
The crater is in an area known as the Antarctic @ basin, a large, 1,600-mile-wide crater at the bottom of the moon with different minerals. This may reflect the material produced by the basin formation in the moon's interior.
For reasons that are not yet understood, the far side of the moon also has considerably more mountains than the front.
What will chang 'e-4 study?
Equipment on the rover and lander, including cameras, ground-penetrating radar and spectrometers, will help identify the composition of rock and soil in the area. China's space agency has cooperated with other countries. One was developed by Germany's Kiel University; Another was provided by the Swedish Institute of Space Physics.
月球车和着陆器上的配套设备，包括摄像机、探地雷达和光谱仪，将有助于识别该区域的岩石和泥土的成分。中国航天局与其他国家进行了合作。其中一个仪器由德国基尔大学(Kiel University)开发；还有一个由瑞典空间物理研究所(Swedish Institute of Space Physics)提供。
The instruments will probe the structure of the rock beneath the spacecraft and study the impact of solar winds hitting the moon's surface. Chang 'e-4 will also test its ability to make radio astronomy observations from the far side of the moon without being affected by earth noise and interference.
Chang 'e-4 will also conduct an interesting biological experiment to see if plant seeds germinate and silkworm eggs hatch in the moon's low-gravity environment, xinhua reported.
How does a spacecraft communicate with earth?
China launched the queqiao satellite in May because the moon blocks radio signals from earth. Orbiting high on the far side of the moon, the satellite will carry out communications between earth and the chang 'e-4 lander.
When will chang 'e-4 land on the moon?
China's space agency has yet to announce a landing date, but it is expected to be in the first week of January, when the sun will shine on the far side of the moon.
Zhang xiaoping, assistant professor at the lunar and planetary science laboratory of the China institute of international space science and Macao university of science and technology, said the spacecraft will follow the chang 'e-3's path. That means it will arrive in three to five days and then orbit the moon for a few days (chang 'e-3 was in orbit for 13 days) while preparing to land.
Wait, I thought the far side of the moon was black.
The far side is not always dark.
The first new moon of 2019 will be on January 6. You couldn't see the moon because the dark side, the side in the shadow away from the sun, was facing the earth. When the near side of the moon gets dark, the far side is bathed in bright sunlight.
Why is China so secretive about this?
Chinese officials have talked publicly about chang 'e-4, but their interactions with reporters are more akin to the carefully orchestrated tactics used in the Soviet program during the cold war than to the public propaganda of NASA and many other space agencies. In this way, China, like the Soviet union, can boast of its successes and downplay its failures.
What does chang 'e mean?
In Chinese mythology, chang 'e is the moon goddess. Other operations have been named after chang 'e.
Chang 'e-1 and chang 'e-2 entered orbit around the moon, but did not land. Chang 'e-1 was launched in 2007. Chang 'e-2 was later launched in 2010.
The next step in China's lunar program is for the chang 'e-5 unmanned spacecraft to land on the moon and bring rock samples back to earth for further study.
Chang 'e-5 was supposed to fly to the moon before chang 'e-4, but the launch of a large Chinese rocket to carry it into space has failed, and its journey has been pushed back to later 2019.
What other countries have plans to go to the moon?
The Indian government plans a mission next year called chandrayaan-2, which will include an orbiter, a lander and a probe. SpaceL, the Israeli company shortlist for the Google lunar X prize, is also still preparing to send an unmanned lander to the moon early next year, even though the $20 million prize has expired.
Last week, NASA announced that nine companies would compete for an unmanned mission to carry scientific experiments to the moon. The space agency says the first of these operations could begin as early as 2019, but most companies say they won't be ready until 2021.
NASA administrator Jim Bridenstine hailed chang 'e-4 as an exciting mission and discussed the possibility of working with China's space agency at the international space congress in Bremen, Germany, in October. Federal law prohibits any interaction between NASA and China.
美国国家航空航天局局长吉姆· 布里登斯廷(Jim Bridenstine)称赞嫦娥四号是一项激动人心的任务，并曾于十月份在德国不来梅港市举行的国际宇航大会上谈到与中国的航天局合作的可能。联邦法律禁止美国国家航空航天局与中国进行任何互动。