BEIJING, Oct. 24 (Xinhua) -- The lander and the rover of the Chang'e-4 probe have been switched to the dormant mode for the lunar night after working stably for the 23rd lunar day, according to the Lunar Exploration and Space Program Center of the China National Space Administration.
The lander was switched to dormant mode at 9:40 p.m. Friday (Beijing Time) as scheduled, and the rover, Yutu-2 (Jade Rabbit-2), at 12 noon Friday, said the center.
A lunar day is equal to 14 days on Earth, and a lunar night is the same length. The Chang'e-4 probe, which switched to dormant mode during the lunar night due to the lack of solar power, had been on the far side of the moon for 660 Earth days as of Saturday, and the rover has traveled 565.9 meters.
During the 23rd lunar day, Yutu-2 went northwest, traveling toward an area with basalt and an impact crater area with high reflectivity. En route to the destination, the near-infrared spectrometer on the rover was used to detect a rock about 30 cm in diameter. The research team is analyzing the transmitted data.
Scientists carried out the first systematically documented measurements of radiation on the moon with data acquired by the neutron radiation detector onboard. According to the study published in the journal Science Advances, the moon's surface is highly radioactive, approximately two to three times the International Space Station, five to ten times a civil flight, and 300 times the surface of the earth of Beijing.
The study provided a reference for the estimation of the lunar surface radiation hazards and the design of radiation protection for future lunar astronauts.
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.
The rover Yutu-2 has far exceeded its three-month design lifespan, becoming the longest-working lunar rover on the moon.
Oct. 24 is a significant day for China's lunar exploration.
On Oct. 24, 2007, China's first lunar probe Chang'e-1 was launched, making China the fifth country to develop and launch a lunar probe on its own and opening up a new age of deep space exploration for China.
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 moon. Chinese scientists released the first complete map of the moon's surface in November 2008, thanks to Chang'e-1.
After orbiting the moon for about 16 months, the probe made a controlled crash on the lunar surface in March 2009.
On Oct. 24, 2014, China launched an experimental spacecraft to test technologies to be used in the Chang'e-5, which is expected to bring moon samples back to Earth.
The spacecraft, comprising a re-entry capsule and a service module, flew around the moon for half a circle. The return capsule touched down at the designated landing area in Siziwang Banner, north China's Inner Mongolia Autonomous Region, on Nov. 1, 2014.