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Chang’e-4 spacecraft enter lunar nighttime, China planning future missions, cooperation  

The Chang’e-4 lander imaged by the Yutu-2 rover on the lunar far side. Credit: CLEP/CNSA

HELSINKI— The Chang’e-4 lander and rover have powered down for a first lunar nighttime on the far side of the moon following a successful landing and first set of surface activities.

Nighttime began over the landing site in Von Kármán crater within the South Pole-Aitken Basin late Jan. 13 UTC, bringing an end to the mission’s first daytime.

With the use of a Russian-developed radioisotope thermoelectric generator —an upgrade on the previous Chang’e-3 lander and rover mission and prototype for future deep-space exploration—the Chang’e-4 lander will be able to run at a low level of activity and will take soil temperature measurements.

The Yutu-2 rover meanwhile will have folded it its solar panels and entered a sleep mode, relying on a radioisotope heater unit for the 14-Earth-day long lunar nighttime, when temperatures will plunge well below -100 degrees Celsius (-148 Fahrenheit).

The lander and rover will resume their science and exploration activities following sunrise early Jan. 28.

China has hailed the mission as complete success regarding engineering goals and will now move into the science phase.

The mission achieved the first-ever landing on the lunar far side at 9:26 p.m. Eastern Jan. 2 following launch Dec. 7, lunar orbit insertion five days later and 21 days in polar lunar orbit.

The first images from the Yutu-2 rover and cylindrical and azimuth panoramas were released Friday by the China Lunar Exploration Program, along with images of the lander taken by the rover and vice versa, as well as sped-up footage from the 12-minute descent from orbit at 15-kilometer-altitude perilune to the landing site within Von Kármán crater, with noticeable automated hazard avoidance maneuvers taking place first during approach and later hover phase, around 100 meters above the surface.

Azimuth and cylindrical projection panoramas taken by Chang’e-4 lander. Credit: CLEP/CNSA
Azimuth and cylindrical projection panoramas taken by Chang’e-4 lander. Credit: CLEP/CNSA Credit: CLEP/CNSA

Sun Zezhou, chief engineer for Chang’e-4, noted at a news conference Monday that the landing had been precise, setting down successfully in the middle four impact craters. The plan for Yutu-2, based on assessment of the topography and other criteria, will be to move southward, followed by westward then to the north, when daytime resumes.

Philip Stooke of the Centre for Planetary Science and Exploration at the University of Western Ontario, Canada, carried out a comparison of the azimuth panorama with features of the rim of Von Kármán crater, also isolating the crater’s central peak.

 The Von Kármán crater (left) and azimuth panorama, indicating matching rim and horizon features. Credit: Phil Stooke

The Von Kármán crater (left) and azimuth panorama, indicating matching rim and horizon features. Credit: Phil Stooke Credit: Phil Stooke

Testing and calibrating of science payloads has been initiated and has returned satisfactory results, according to mission scientists. Martin Wieser of the Swedish Institute of Space Physics in Kiruna, Sweden, which the Advanced Small Analyzer for Neutrals (ASAN), a detector for energetic neutral atoms, told SpaceNews that the multistep commissioning phase of ASAN is ongoing and the first science data are expected before mid-February. “So far, all activities related to ASAN worked out very well,” Wieser said.

The 3-kilogram mini biosphere developed by Chongqing University and other Chinese higher education institutions and containing fruit fly eggs, yeast and cotton, rape, potato and Arabidopsisis seeds is also underway, with the Chinese language news site reporting that the experiment was initiated at 10:13 a.m. Eastern Jan. 3 and saw water added 30 minutes later, followed shortly after by the first images.

The experiment is being carried out in the lunar environment features of low gravity, bright sunlight and radiation, according to chief designer of the experiment Prof.Xie Gengxin, opening a new chapter in space experiments. On Tuesday Chinese media reported the first images from the canister on the moon and those from an Earth-based control experiment.

Next lunar exploration missions, international cooperation

During a Jan. 14 news conference on the Chang’e-4 mission held by China’s State Council, Wu Yanhua, vice administrator of the China National Space Administration (CNSA) and other mission officials and scientists outlined a number of key innovations, areas of collaboration and challenges, notably touching on ongoing and future international collaboration and future missions.

It was stated that China and American counterparts had been in regular contact ahead of the mission, arranging surveillance of the planned landing area by NASA’s Lunar Reconnaissance Orbiter to provide data for the landing. While real-time monitoring of the Chang’e-4 landing by LRO was discussed, the respective orbits of the spacecraft ruled this out.

On future activities Wu told reporters that China would be involved in the Russian Luna 26 lunar orbiter mission, which would then play a part in potential Chinese lunar South Pole landings.

As part of a new stage of lunar exploration the Chang’e-7 mission, to launch in the early 2020s, will involve “comprehensive exploration of the lunar South Pole,” including landscape, composition and space environment. Chang’e-8 will continue with existing tasks at the pole but will also test key technologies on the lunar surface, possibly together with international partners. The missions were described as being in the conceptual design phase.

China, the U.S., Russia and European countries are “discussing whether we need to establish a research station on the moon for 3D printing and for other technologies,” Wu said, adding that Chang’e-8 will lay the foundation for Chinese and foreign scientists to establish such a base.

More immediately it was stated that China will launch the Chang’e-5 lunar sample return mission by the end of the year, followed by launch of the Mars orbiter and rover in July or August 2020.

It was not stated that both these depend on a successful return-to-flight of the heavy-lift Long March 5 rocket, currently expected in Q2 2019. Chang’e-5 was expected to fly in November 2017 but was delayed by the failure of the second Long March 5 in July that year.

Andrew Jones covers China's space industry for GBTIMES and SpaceNews. He is based in Helsinki, Finland.