China’s Chang’e-4 Moon lander – farside bound
Credit: China National Space Administration (CNSA)/China Central Television (CCTV)/Screengrab Inside Outer Space

 

China’s adventurous mission to the farside of the Moon attained its second orbit trimming on Sunday afternoon

The Chang’e-4 lunar probe was launched in the early hours of Saturday from the Xichang Satellite Launch Center in southwest China’s Sichuan Province.

If all goes well, the lander/rover will touch down on the farside of the Moon for the very first time, reportedly early next month.

Ground control

As reported on China Central Television (CCTV):

“We have just completed the second orbit modification for Cheng’e-4 and then we will conduct the third one to ensure that it can precisely enter the lunar orbit and prepare for a soft landing of the probe,” said Li Peng, an assistant engineer with Kashgar Observation and Control Station.

In the next month, ground controllers will invoke important movements of Chang’e-4 during the flight, such as orbit correction and near-Moon braking, and adjusting the final attitude of the probe through a relay satellite launched last May named “Queqiao” to ensure a successful lunar landing.

“In the 110-hour-long orbit transfer from the Earth to the Moon, we will seize every second to upload the orbit parameters in time and ensure the third orbital transfer to be successful,” said Liu Qing, an engineer in Kashgar Observation and Control Station.

Chang’e-4 Moon lander and rover.
Credit: Chinese Academy of Sciences

Rugged terrain

“Most of the farside of the Moon are covered with high mountains, impact craters and lunar craters. It is difficult to find a large and flat area. This requires that we must be more accurate in fixing the landing site,” said Sun Zezhou, chief designer of Chang’e-4.

As reported on CCTV, the rugged terrain of the Moon has not only increased the difficulty in locating the best landing point, but also will affect the probe’s judgment of its distance to the lunar surface and the relative velocity. As a result, a special design in the navigation control of the probe was adopted.

Credit: China National Space Administration (CNSA)/China Central Television (CCTV)/Screengrab Inside Outer Space

Day/night operations

There are some differences between the December 2013 Chang’e-3 lander/rover mission and Chang’e-4.

“The Chang’e-3 landed on the Moon following a parabolic path, but our Chang’e-4 will primary land vertically,” said Sun. To assure day/night operations, Chang’e-4 is equipped with a heating supply system, aimed to power the equipment.

“Based on the supply of heat energy, we also try to use thermoelectric effect to generate power for the electronic equipment,” said Sun.

The probe is expected to make the first-ever soft landing on the far side of the Moon within 30 days, and will undertake a variety of tasks including conducting surveys on the terrain and landforms.

Credit: China National Space Administration (CNSA)/China Central Television (CCTV)/Screengrab Inside Outer Space

Communication issues

CCTV notes that this first time farside landing may encounter some communication difficulties.

“If it lands on the farside of the Moon, there might be a delay on the measurement and control [systems] after it connects to the relay satellite,” said Li Benqi, deputy director of the Xichang Satellite Launch Center.

“We are not sure whether the delay will cause troubles to the landing and image transmission. This [mission] will help us accumulate more experience for future lunar exploration,” Li said.

Radio astronomical observations

One of the main tasks the probe will conduct is its investigation into the radio environment of the farside of the Moon, the first time that low-frequency radio astronomical observations have been tested.

“Especially by making using of the clean electromagnetic environment on the far side of the moon, the probe will achieve observation of low-frequency radio ranging from 0.1 to 0.4 megahertz for the first time,” said Yu Guobin, a spokesman for the Chang’e-4 lunar exploration project.

In addition to its panoramic camera, lunar penetrating radar and topographic camera, the probe is also equipped with a low-frequency radio spectrometer to help it better detect the low-frequency signals.

Credit: China National Space Administration (CNSA)/China Central Television (CCTV)/Screengrab Inside Outer Space

“The (farside of the) Moon can well shield the Earth’s own low-frequency radiation and create a better environment with low frequency and noise. This could help the probe detect the low-frequency signals from the sun more effectively,” said Sun, the lunar probe’s chief designer.

In addition, China has promoted international cooperation in its lunar exploration program, with four scientific payloads in the Chang’e-4 mission developed by scientists from the Netherlands, Germany, Sweden and Saudi Arabia.

For video views of the Chang’e-4 project and launch, go to:

https://youtu.be/cGp7WySaVW4?list=PLpGTA7wMEDFjz0Zx93ifOsi92FwylSAS3

https://youtu.be/58r_OTXn6i4

 

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