The rotation of the moon has been slowed by Earth enough that only one hemisphere is visible to us. During a full moon, however, the "dark side" is truly dark. Scientists estimate that the far side of the moon gets as hot as 260 degrees Fahrenheit (127 Celsius) during the day, and negative 297 (minus 183 Celsius) during the lunar night. China is the first country to deploy a lander to the far side of the moon.
"Chang'e-4 will measure the temperature differences between the day and night on the moon, helping scientists estimate the properties of the lunar soil," said Zhang He, executive director of the Chang'e-4 probe project, from the China Academy of Space Technology (CAST).
Tan Mei, a consultant for the probe from CAST, said Chang'e-4 will switch to a "sleep mode" during the lunar night due to the lack of solar power, and rely on the radioisotope heat source to keep warm.
"We need to transform heat into power to run the thermometry to measure the temperatures of the lunar surface at night," Tan said.
Related: China’s successful landing on the far side of the moon is a part of lunar history
The lander is equipped with dozens of temperature data collectors, and the data they collect at night will be transmitted after the probe is wakened during the moon's daytime, said Li Fei, a designer of the lander from CAST.
Sun Zezhou, the chief designer of the Chang'e-4 probe from CAST, noted that the isotope thermoelectric generation technology on Chang'e-4 is a prototype for future deep-space explorations. NASA's Curiosity rover also adopts this technology.
"It is a technology that we must master if we want to go to the moon's polar regions or deep space farther than Jupiter, where solar power cannot be used as the primary power source," he said.
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