Chang’e-4 makes soft-landing on the moon

 China’s Chang’e-4 spacecraft made the first ever soft-landing on the far side of the moon in a mission investigating the history of the solar system and paving the way for future exploration.

The 1,200-kilogram dry mass Chang’e-4 lander touched down at 177.6 degrees east longitude and 45.5 degrees south within Von Kármán crater at 9:26 p.m. Eastern, according to an announcement from the China National Space Administration (CNSA).

The spacecraft began its descent at 9:15 p.m. from a perilune of 15 kilometers with a burn of its single main variable thruster before entering approach, hazard avoidance and slow descent phases, with a descent camera returning images of the approaching surface.

 

The lander and the companion 140-kilogram rover, who is expected to be deployed within the coming hours, will work toward science goals including analyzing the lunar surface and subsurface composition, assessing the radiation environment and its interaction with the regolith and low frequency radio astronomy, as well as returning high-resolution images from terrain and panoramic cameras.

The 186-kilometer-diameter Von Kármán crater containing the landing site is situated within the 2,500-kilometer-wide South Pole-Aitken (SPA) basin, which is one of the oldest and largest impact craters in the solar system.

The basin could contain exposed material from the moon’s upper mantle and promises clues to the history and development of the solar system. A sample return from the SPA basin has been noted as a priority in past US Planetary Science Decadal Surveys.

The mission launched in December and had been in lunar orbit ever since, where it tested communications and refined its orbit in preparation for a landing timed to follow sunrise over the target site, allowing the mainly solar-powered craft to begin operations immediately.

Chang’e-4 is the repurposed backup spacecraft to the Chang’e-3 mission, which landed on Mare Imbrium on the near side in December 2013, making China only the third country to soft-land on the moon.

While the Chang’e-3 rover, on which the Chang’e-4 is based, traveled just 114 meters before being rendered immobile on Mare Imbrium in early 2014, officials with the China Academy of Space Technology (CAST), the spacecraft’s manufacturer, have stated that the issue has been identified and addressed and that the new rover has been upgraded for greater reliability and longevity.

The landing comes ahead a wave of renewed interest in lunar exploration, with NASA, ESA, Russia, India and private companies working on a range of missions.

The China Aerospace Science and Technology Corporation (CASC) also announced that it plans to launch the Chang’e-5 near side sample return mission with the second of two planned Long March 5 heavy-lift rocket launches in 2019.

The landing will also assist in the execution of the country’s future lunar exploration plans, including sample returns and polar landings in preparation for a potential human outpost.

Robert F. Wimmer-Schweingruber of the University of Kiel, Germany, which led the development of the Lunar Lander Neutrons and Dosimetry (LND) experiment, told SpaceNews that LND can, “help us understand the radiation which lunar soils and rocks are exposed to and to detect sub-surface water.”

“Its main purpose, however, is to prepare for human exploration of the moon by measuring the radiation to which astronauts will be exposed,” says Wimmer-Schweingruber, and specifically the neutron dose rate on the surface of the moon.

James Head, a planetary scientist at Brown University in Providence, Rhode Island, told SpaceNews in December that the Lunar Penetrating Radar (LPR), an instrument also aboard the Chang’e-3 rover, will provide images of the structure of the lunar soil layers and any subsurface lava flow units.

The Visible and Near-Infrared Imaging Spectrometer (VNIS), likewise installed on the mobile rover, will allow analysis of the mineralogy of the floor of Von Kármán crater and ejecta delivered by later, nearby impacts, according to Head.

The Low Frequency Spectrometer (LFS) payload on the Chang’e-4 lander will make astronomical observations in low frequency bands in a unique radio-quiet environment free of interference from the earth.

Another payload included in the mission through an outreach initiative is a small biosphere containing Arabidopsis and potato seeds along with silkworm cocoons, designed and developed in collaboration with 28 Chinese universities.

The experiment will be a pioneering test of photosynthesis and respiration in the one-sixth Earth gravity lunar environment, with a possible live steam to the 3-kilogram, 0.8-liter capacity canister.