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.
- Dimensions: 4.4 meters between opposite landing legs
- Mass: 1,200 kilograms (dry, without rover)
- Launch vehicle: Long March 3B
Lander science instruments:
Landing Camera (LCAM): Used to image the surface during descent. Chang’e-3 carried a similar camera and captured this video. Mounted on the bottom of the spacecraft. Monochrome, 1024x1024 detector, 45 degrees FOV, spectral range 419-777 nm. Yingzhuo Jia et al. (2018)
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
- Dimensions: 1 meter tall, 1 meter wide (without solar panels), 1.5 meters long. Two foldable solar panels, six wheels.
- Mass: 140 kilograms
Yutu-2 science instruments
Panoramic Camera (PCAM): An imaging system similar to the one on the first Yutu rover. Two cameras on a rotating mast, allowing a full 360-degree view. Color (RGB) and panchromatic, 2352 by 1728 pixels each, 19.7 x 14.5 degrees FOV each, spectral range 420-700 nm. Yingzhuo Jia et al. (2018) | Chang’e-3 PCAM library
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).
- China’s Lunar and Deep Space Exploration (CLEP) program news releases
- Chang’e-4 landing CLEP news release
- Yutu-2 naming CLEP news release
- Yutu-2 deployment CLEP news release
- NASAspaceflight.com mission thread
- Unmannedspaceflight.com mission thread
- Unmannedspaceflight.com Yutu-2 route map thread
- Longjiang-2 raw images
- When archival data are released (NET 6 months after acquisition, so NET July 2019), they will be available at the Chinese Lunar and Deep Space Exploration Scientific Data and Sample Release System website
- Search weibo.com for 嫦娥四号 (Chang’e-4) or 玉兔二 (Yutu-2)
- Search Google.com for 嫦娥四号 (Chang’e-4) or 玉兔二 (Yutu-2)
- Semi-official weibo outreach accounts: Chang’e the Stargazer and Yutu-2
Key scholarly articles:
- Mission overview by Yingzhuo Jia et al. (2018) in Planetary & Space Science (paywall)
- Geological context of the landing site by Zongcheng Ling et al. (2018) from Lunar and Planetary Science Conference