BEIJING, Nov. 23 (Xinhua) -- China plans to launch the Chang'e-5 probe late this month, in hopes of conducting unmanned lunar sample collection and returning to Earth.
China's lunar exploration program is named after the legendary Chang'e, the "Moon Lady," who took a potion and floated into the sky, eventually landing on the moon, where she became a goddess accompanied by a jade rabbit.
The Chang'e lunar exploration program that began in 2004 includes orbiting and landing on the moon and bringing samples back to Earth. Here is a brief overview of China's journeys to the moon.
China's first lunar probe, Chang'e-1, was launched on Oct. 24, 2007, making China the fifth country to develop and launch a lunar probe on its own.
Orbiting 200 km above the moon, it mapped 3D images of the lunar surface, analyzed the distribution of elements, measured the depth of lunar soil, and explored the environment between Earth and the moon. Chinese scientists acquired the first complete map of the moon's surface, thanks to Chang'e-1.
Chang'e-2, which blasted off on Oct. 1, 2010, gained a full lunar map with a spatial resolution of 7 meters, showing more details of the lunar surface than Chang'e-1, which had a resolution of 120 meters.
It also took pictures of the Sinus Iridum, or the Bay of Rainbows, the proposed landing site of Chang'e-3.
After accomplishing its tasks, Chang'e-2 flew to the L2 point of the Sun-Earth system, where gravity from the sun and Earth balances the orbital motion of a satellite, to conduct scientific experiments.
It was then tasked to fly by the Toutatis asteroid, about 7 million km from Earth. Chang'e-2 came within 3.2 km of Toutatis and captured images with a spatial resolution of 10 meters at a relative velocity of 10.73 km per second.
Chang'e-3 was launched on Dec. 2, 2013, and softly touched down on the Sinus Iridum 12 days later. It was the first Chinese spacecraft to soft-land on and explore an extraterrestrial object.
The success made China the third country, after the former Soviet Union and the United States, to soft-land on the moon.
Chang'e-3 included a lander and a moon rover called Yutu (Jade Rabbit), which took photos of each other while the rover circled the lander.
The probe acquired a geological profile of the moon, detected the geological structure from the lunar surface to 330 meters beneath, and discovered a new kind of lunar rock. The findings could give scientists new insights into the evolution of the moon.
TEST CRAFT FOR CHANG'E-5
China launched an experimental spacecraft on Oct. 24, 2014, to test technologies to be used on Chang'e-5.
Comprising a re-entry capsule and a service module, it flew halfway around the moon. After the re-entry and service capsules separated, the re-entry capsule approached Earth's atmosphere at about 11.2 km per second.
The return capsule touched down at the designated landing area in Siziwang Banner, north China's Inner Mongolia Autonomous Region, on Nov. 1, 2014.
The service module flew back to orbit the moon for further tests and reached the L2 point of the Earth-Moon system to conduct experiments.
QUEQIAO RELAY SATELLITE
China launched a relay satellite named Queqiao (Magpie Bridge) on May 21, 2018, to set up a communication link between Earth and the moon's far side.
The satellite has entered a halo orbit around the L2 point of the Earth-Moon system, about 455,000 km from Earth, where it can "see" both Earth and the far side of the moon. It is the world's first communication satellite operating in that orbit.
The Chang'e-4 probe, launched on Dec. 8, 2018, made the first-ever soft landing on the Von Karman Crater in the South Pole-Aitken Basin on the far side of the moon on Jan. 3, 2019.
Chang'e-4, including a lander and a moon rover called Yutu-2, or Jade Rabbit-2, conducted low-frequency radio astronomical observation, terrain and landform survey, mineral composition and shallow lunar surface structure detection, and neutron radiation and neutral atom measurement.
The rover Yutu-2 has far exceeded its three-month design lifespan, becoming the longest-working lunar rover on the moon.
Based on data from China's Chang'e-4 probe, Chinese scientists have determined the thickness of the regolith and revealed the fine subsurface structures and evolutionary history of the probe's landing site on the moon's far side.