Chang'e 4

Description

The Chang'e 4 mission is a Chinese National Space Administration (CNSA) lander to the far side of the Moon, which launched on a Long March 3B from Xichang, China, on 7 December 2018. The landing site was in the 186 km diameter Von Karman crater in the northwestern South Pole-Aitken Basin (45.5 S latitude, 177.6 E longitude). Since the lander is on the far side, the Moon is blocking direct radio contact with the Earth, so a relay satellite is used for communications. The Chang'e 4 lander was a backup to the Chang'e 3 mission with the same basic structure, a landing platform and a rover, but a different science payload.

The lander has a dry mass of 1200 kg, carrying its own experiments and the rover. The experiments include a low-frequency (0.1 - 40 MHz) radio spectrometer (LFS), a Landing Camera (LCAM), Terrain Camera (TCAM), a Lunar Lander Neutrons and Dosimetry Experiment (LND), and a biological experiment.

It includes a rover, Yutu 2, based on the Chang'e 3 Yutu ("Jade Rabbit") rover. The rover, with a total mass of 140 kg, has a rectangular body 1.1 meters high, 1.5 m long, and 1 m wide, but unlike the Chang'e-3 rover will not have a robotic arm. It has 6 wheels, two solar panels, and a dish antenna. Its scientific payload comprises cameras, including a Panoramic Camera (PCAM), a Visible/Near-Infrared Imaging Spectrometer (VNIS), Lunar Penetrating Radar (LPR), and the Advanced Small Analyzer for Neutrals (ASAN).

Launch took place at 2:23 a.m. on December 8, 2018 Beijing time (18:23 UT (1:23 p.m. EST) Dec. 7) and Chang'e 4 entered lunar orbit on 12 December. After three weeks of lunar orbital maneuvers, Chang'e-4 landed in Von Karman crater in the South Pole-Aitkin Basin on 3 January 2019 at 02:26 UT (10:26 a.m. Beijing time), becoming the first spacecraft to make a controlled landing on the far side of the Moon. Landing coordinates were calculated within 20 meters from LRO images as 45.457 S latitude, 177.589 E longitude. The Yutu-2 rover was driven down ramps onto the surface about 12 hours later, at 14:22 UT. The rover moved forwards towards a small crater and turned on its instruments. On 6 January the rover went into a planned hibernation to protect itself from the heat of lunar noon and reawoke on 10 January and continued travelling and making measurements. The rover shut down over the local lunar night, beginning about January 13-14. Both the lander and rover used a radioisotopic heat source to maintain survival temperatures. Yutu-2 resumed daytime operations on 29 January, and the lander a day later. It has been hibernating during the lunar night and operational during the day, as planned. It started its fifth lunar day on 29 April.

Chang'e-4 uses a communication relay satellite, in a halo orbit around the Earth-Moon L2 point to maintain communication between the lander and Earth ground control. The satellite, Queqiao, based on the Chang'e 2 design, launched on 20 May 2018 to enable communication with the far side. Two scientific microsatellites, Longjiang-1 and Longjiang-2, were launched with Queqiao.