China on the dark side of the moon
The first picture of the far side of the moon. Credit: China National Space Administration.
China has successfully landed a rover, Chang’e-4, on the far side of the moon on Thursday, making it the first country to land a probe on the uncharted and never-visible-from-Earth side of the moon after years of planning.
The probe landed at a preselected landing area, 177.6 degrees east longitude and 45.5 degrees south latitude on the far side of the moon, at 10:26 AM Beijing time today after being launched on 8 December 2018 at the Xichang launch centre.
When Chang’e-4 landed it sent a picture of the ‘dark side’ of the moon back controllers on Earth through the communications transfer satellite Queqiao, meaning Magpie Bridge.
In contrast to the near side of the moon, the far side is rugged and mountainous making it harder to touch down.
According to China National Space Administration (CNSA), 8 experiments are being carried by Chang’e-4. Six of them from China and two developed through international cooperation. The probe will conduct low-frequency radio astronomical observation, assess the terrain and landforms, detect the mineral composition and shallow lunar surface structure and measure the neutron radiation, as well as the neutral atoms to study the environment on the far side of the moon.
The probe is the second to land on the moon, succeeding the Yutu, meaning Jade Rabbit, rover in 2013 which was also landed by China and went on to successfully survey the moon surface for 31 months.
Temperature and Communication Challenges
The reason there was a need for the Queqiao satellite is because of the lack of a clear ‘line of sight’ on the far side of the moon able to communicate with the lander. The satellite was positioned so it could transfer data, as well as commands between Chang’e-4 and Earth.
The next hurdle is the fluctuations in temperature the lander has to withstand as well as being able to generate enough energy to endure the huge temperature span. The temperature will fluctuate between minus 173 degrees during the lunar night, which lasts for 14 Earth days and 127 degrees during the 14-Earth-days-long lunar day.
Yutu and Chang’e-4 will not be the only lunar landers planned and executed by the Chinese. In Beijing they are already planning to send another lander, Chang’e-5. It will collect samples and bring them back to Earth and will be launched later this year. There is also ambition to develop a reusable launcher by 2021, a moon base, a permanent space station and a Mars rover, among others.
The lunar probe mission is named after the Chinese mythology’s moon goddess.