Chang’e-4 ready for attempted farside landing.
Credit: CCTV/Screengrab/Inside Outer Space

China’s Chang’e-4 will shortly nosedive toward a farside of the Moon touchdown.

The state-run China Daily reports January 1st that the country’s Chang’e 4 robotic probe is expected to land on the South Pole–Aitken basin on the Moon’s farside sometime between Wednesday and Thursday, citing information from China Aerospace Science and Technology Corp, a major contractor of the country’s lunar exploration programs.

The Chang’e-4 mission totes six kinds of scientific payloads.

Chang’e-4 powers down to farside landing.
Credit: CCTV/Screengrab/Inside Outer Space

On the lander, it carries the Landing Camera (LCAM), the Terrain Camera (TCAM), and the Low Frequency Spectrometer (LFS). There are three kinds of payloads on the rover, the Panoramic Camera (PCAM), the Lunar Penetrating Radar (LPR), and the Visible and Near-Infrared Imaging Spectrometer (VNIS).

That Low Frequency Spectrometer is newly developed for Chang’e-4 lander; the other payloads are inherited instruments from an earlier Chang’e-3 lunar mission.

Chang’e-4 touchdown on Moon’s farside.
Credit: CCTV/Screengrab/Inside Outer Space

International joint collaboration payloads on the Chang’e-4 mission include:

Germany’s Lunar Lander Neutrons and Dosimetry (LND) installed on the lander

Sweden’s Advanced Small Analyzer for Neutrals (ASAN) installed on the rover

Netherlands-China Low-Frequency Explorer (NCLE) installed on the relay satellite

Scientific objectives

Chang’e-4 lander deploys lunar rover. Credit: CCTV/Screengrab/Inside Outer Space

Overall, the scientific objectives for the Chang’e-4 are:

Low-frequency radio astronomical study on the lunar surface

Shallow structure investigation at the lunar farside within the roving area

Topographic and mineralogical composition studies of the lunar farside within the rover’s patrol area.

Chang’e-4 carrying out low-frequency radio astronomical studies.
Credit: CCTV/Screengrab/Inside Outer Space

The Chang’e-4 mission carrying out low-frequency radio astronomical studies on the lunar surface is intriguing.

The lunar farside blocks the Earth’s ionosphere, human-made radio frequency interference, and the auroral kilometric radiation noise. Additionally, also blocked is the solar radio emission during the night time.

Lunar radio environment

“We’ve been following the Chang’e-4 mission closely,” says Jack Burns, Professor of Astrophysics and Planetary Science at the University of Colorado, Boulder. He is also the Director of the NASA-funded Network for Exploration and Space Science (NESS).

Credit: CNSA’s Lunar Exploration and Space Engineering Center (CNSA-LESEC)

Several Dutch members of the NESS team, Burns notes, are co-principal investigators of the Netherlands-China Low-Frequency Explorer (NCLE) installed on China’s relay satellite positioned at an L2 halo orbit.

“Their antenna won’t be deployed until after the main mission involving the farside lander is complete. They expect to begin gathering data in the spring. The expectations for this experiment are modest,” Burns pointed out. There are two issues, he said.

“First, no effort was made to make the satellite radio quiet. In fact, the team doesn’t even know what the amount of internally-generated radio frequency interference (RFI) will be. It could be overwhelming or more modest. Second, the satellite is not in an ideal orbit for radio astronomy.”

The L2 halo orbit is in constant view of the Earth and, thus, is exposed to Earth RFI which is quite substantial, Burns explained. “This too may limit the quality of the data. Nonetheless, this is an exciting experiment as it is the first to characterize the lunar radio environment since NASA’s Radio Astronomy Explorer-2 (RAE) in 1972.”

Germany’s scientific payload is a Lunar Lander Neutron and Dosimetry instrument, developed by Kiel University. Credit: Kiel project manager, Jia Yu

Radiation, life science

Provided by Germany, the Lunar Lander Neutron and Dosimetry instrument was developed by Kiel University. The device is designed to gauge radiation on the Moon, mainly for future human missions. It will also measure the water content underneath the lander.

Also onboard the mission is a “lunar mini biosphere” experiment designed by 28 Chinese universities, led by southwest China’s Chongqing University, The cylindrical tin, made from special aluminum alloy materials, weighs roughly 7 pounds (3 kilograms).

The tin also contains water, a nutrient solution, and air. A tiny camera and data transmission system allows researchers to keep an eye on the seeds and see if they blossom on the Moon.

Mini biosphere

“We have to keep the temperature in the ‘mini biosphere’ within a range from 1 degree to 30 degrees, and properly control the humidity and nutrition. We will use a tube to direct the natural light on the surface of Moon into the tin to make the plants grow,” said Xie Gengxin, chief designer of the experiment, in a recent Xinhua news story.

Added Liu Hanlong, chief director of the experiment and vice president of Chongqing University: “Our experiment might help accumulate knowledge for building a lunar base and long-term residence on the Moon.”

The Moon-bound mini biosphere experiment was selected from more than 200 submissions, according to the China National Space Administration (CNSA).

Chang’e-4 rover is outfitted with a Lunar Penetrating Radar.
Credit: CCTV/Screengrab/Inside Outer Space

Penetrating look

Another aspect of the Chang’e-4 rover is use of a Lunar Penetrating Radar, able to detect the lunar subsurface structure on the robot’s patrol route, and to detect the thickness and structure of the lunar regolith. The device is a nanosecond impulse radar with bistatic antennas.

A similar device was utilized on the Chang’e-3 rover, Yutu, that wheeled across the Moon in December 2013.

It works like this: An ultra-wideband nanosecond impulse is produced by a transmitter, sent through the transmitting antenna down to lunar surface. The receiving antenna receives the reflected signal. The echo signal from the underground target is received by the receiving antenna, amplified in the receiver and then restored as data record.

Chang’e-5 mission hurls lunar samples into Moon orbit.
Credit: CCTV/Screengrab/Inside Outer Space

Next phase

China’s next lunar probe, Chang’e-5, is designed to bring select samples from the Moon back to Earth. It builds upon a progression of Chinese Moon explorers: Chang’e-1 and Chang’e-2 orbiters in 2007 and 2010, respectively, and the Chang’e-3 lunar lander/rover mission in December 2013.

Zhang Kejian, deputy minister of the Ministry of Industry and Information Technology of China, has stressed China’s willingness to cooperate with other countries within the space program.

Zhang, who is also the head of the CNSA, noted that Chang’e-6, China’s second sample return lunar mission, will provide 22 pounds (10 kilograms) of payload space on the orbiter and lander for international partners.

One Response to “China’s Chang’e-4 Ready for Farside Moon Landing (Updated)”

  • Frank Schmidt says:

    The USA left the Moon some 50 years ago. it’s a shame. If we had continued we would by now likely have a maned lunar base there. Its a pity.

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