China's Chang'e-4 (嫦娥四号) mission delivered a landing platform and a rover named Yutu-2 (玉兔二) to the Moon's far side—the first mission there by any country. Chang'e-4 landed in Von Kármán crater, within the Moon's South Pole-Aitken basin, in December 2018. An ancient lunar impact there may have exposed the Moon’s mantle. By studying this region directly, scientists will learn more about the early solar system and Earth. The mission also demonstrates the feasibility of future human and robotic far side missions.
The Moon’s quiet, airless far side makes it one of the best places in the inner solar system for science applications like radio astronomy. But missions there require a relay satellite, since the far side never faces Earth. China launched the Queqiao relay satellite with two SmallSats, Longjiang-1 and 2, in May 2018.
Chang’e-4 and Yutu-2 are continuing to conduct science operations. Both vehicles power down during the 2-week lunar night, when temperatures plummet to -173 degrees Celsius (280 degrees Fahrenheit), to avoid damanging their instruments. They must also sleep when the Sun is directly overhead to avoid overheating.
CNSA / CLEP
Yutu-2 as seen from Chang'e-4
Chang'e-4 imaged the Yutu-2 rover in early January 2019 using its Terrain Camera (TCAM).
Ivica Stošić / Emily Lakdawalla
Landmarks near the Chang’e-4 landing site
The base image is a simulated view of the farside of the Moon using Kaguya topographic data and Clementine images. The overlay shows landmarks useful in locating the Chang’e-4 landing site inside Von Kármán crater.
A render of the Chang’e-4 lander on the lunar far side.
Dimensions: 4.4 meters between opposite landing legs
Terrain Camera (TCAM): Used to image the lander’s surroundings. Chang'e-3 carried a similar camera that failed in the first lunar night. Mounted on a camera bar on top of the lander that can rotate a full 360 degrees, swing up or down 120 degrees total. Color (RGB), 2352 x 1728 detector, 22.9 x 16.9 FOV, spectral range 420-700 nm. Yingzhuo Jia et al. (2018)
Low Frequency Spectrometer (LFS): Newly developed for Chang’e-4. Astronomers have long dreamed of placing radio telescopes on the radio-quiet, airless far side of the Moon. The LFS will investigate low-frequency waves from the lunar ionosphere, the Sun, interplanetary space, and galactic space. LFS consists of three, 5-meter booms. Yingzhuo Jia et al. (2018)
Lunar Lander Neutrons and Dosimetry experiment (LND): Contributed by University of Kiel, Germany. On Earth, people who work near radioactive sources like a nuclear reactor wear dosimeters to measure the amount of radiation their bodies receive. Likewise, the LND experiment will measure radiation dosages on the Moon and use the data to plan for future human exploration. The neutron counts could also be used to measure the amount of water in the regolith beneath the lander. LPSC poster, Yingzhuo Jia et al. (2018)
Lunar biosphere experiment: A publicly chosen experiment in partnership with 28 Chinese universities to see how silkworms, as well as potato and Arabidopsis (a small flowering plant) seeds, grow in lunar gravity. Image
A render of the Yutu-2.
Dimensions: 1 meter tall, 1 meter wide (without solar panels), 1.5 meters long. Two foldable solar panels, six wheels.
Lunar Penetrating Radar (LPR): A radar instrument used to see subsurface up to more than 100 meters, and the thickness of regolith. Similar to radar used on the first Yutu rover. Yingzhuo Jia et al. (2018)
Visible and Near-Infrared Imaging Spectrometer (VNIS): Used to study the mineral composition of the lunar surface around the rover. Similar to spectrometer used on first Yutu rover. Band range 450-950 (visible near-infrared channel), 900-2400 (near-infrared short-wave infrared). Yingzhuo Jia et al. (2018)
Advanced Small Analyzer for Neutrals (ASAN): Contribution from Institute of space physics, Sweden. Experiment to determine how the solar wind interacts with the lunar regolith by observing energetic particles blasted off the surface. Presentation | Yingzhuo Jia et al. (2018)
Editor’s note: The following instruments were referenced in Wang & Lui (2016) as provisional, but are not included in Yingzhuo Jia et al. (2018), and presumably not aboard Change’e-4: Lunar Dust Analyser (LDA), Electric Field Analyser (EFA), Plasma and Magnetic Field Observation Package (PMFOP), and Lunar Seismometer (LS).