Yutu rover on the lunar surface, imaged by the Chang'e 3 lander.
|Mission type||Lunar rover|
|Mission duration||3 months (planned)
3 months and 6 days elapsed
|Manufacturer||SASEI and BISSE|
|Landing mass||140 kg (310 lb)|
|Dimensions||1.5 m (4.9 ft)|
|Start of mission|
|Launch date||1 December 2013, 17:30UTC|
|Rocket||Long March 3B Y-23|
|Launch site||Xichang LC-2|
|Deployed from||Chang'e 3|
|Landing date||14 December 2013, 13:12 UTC|
|Landing site||Mare Imbrium
Yutu (Chinese: 玉兔; pinyin: Yùtù; literally "Jade Rabbit") is an unmanned lunar rover that forms part of the Chinese Chang'e 3 mission to the Moon. It was launched at 17:30 UTC on 1 December 2013, and reached the Moon's surface on 14 December 2013. The mission marks the first soft landing on the Moon since 1976 and the first rover to operate there since the Soviet Lunokhod 2 ceased operations on 11 May 1973.
The Yutu lunar rover was developed by Shanghai Aerospace System Engineering Institute (SASEI) and Beijing Institute of Spacecraft System Engineering (BISSE). The development of the six-wheeled rover began in 2002 and was completed in May 2010. It was designed to deploy from the lander and explore the lunar surface independently. The rover's name was selected in an online poll, and is a reference to the pet rabbit of Chang'e, the goddess of the Moon in Chinese mythology.
The official mission objective is to achieve China's first soft-landing and roving exploration on the Moon, as well as to demonstrate and develop key technologies for future missions.
The scientific objectives of Chang'e-3 mainly include lunar surface topography and geology survey, lunar surface material composition and resource survey, Sun-Earth-Moon space environment detection and lunar-based astronomical observation. Chang'e 3 will attempt to perform the first direct measurement of the structure and depth of the lunar soil down to a depth of 30 m (98 ft), and investigate the lunar crust structure down to several hundred meters deep.
Unlike NASA and ESA, the China National Space Administration reveals little about its missions to the public, so detailed information about Chang'e 3 is limited. Aspects of Yutu's design and several of its experiments may have been based on NASA's Mars Exploration Rovers. Its wheel design is believed to have been considerably influenced by what was used on the Russian Lunokhod 1 rover.
The Yutu rover has a mass of 140 kg (310 lb), with a payload capacity of 20 kg (44 lb). It is smaller than the Mars Exploration Rovers, Spirit and Opportunity, and carries similar instruments: panoramic cameras, an infrared spectrometer and an alpha particle X-ray spectrometer (APXS). Yutu is also equipped with a robotic arm to position its APXS near a target sample. In addition, the rover can transmit video in real time, and has automatic sensors to prevent it from colliding with other objects.
Yutu was designed to explore an area of 3 square kilometres (1.2 sq mi) during its 3-month mission, with a maximum travelling distance of 10 km (6.2 mi). Energy is provided by two solar panels, allowing the rover to operate through lunar days. During the 14-day lunar nights the rover will go into sleep mode, during which heating is provided by radioisotope heater units (RHU) and two-phase fluid loops.
Ground-penetrating radar (GPR)
The rover carries a ground-penetrating radar (GPR) on its underside, allowing for the first direct measurement of the structure and depth of the lunar soil down to a depth of 30 m (98 ft), and investigation of the lunar crust structure down to several hundred meters deep.
There are two panoramic cameras and two navigation cameras on the rover's mast, which stands ~1.5 m (4.9 ft) above the lunar surface, as well as two hazard avoidance cameras installed on the lower front portion of the rover. Each camera pair may be used to capture stereoscopic images, or for range imaging by triangulation.
Chang'e 3 landed on 14 December 2013 and deployed the Yutu rover 7 hours 24 minutes later.
The planned landing site was announced to be Sinus Iridum. However, the lander descended on Mare Imbrium, about 40 km (25 mi) south of the 6 km (3.7 mi) diameter Laplace F crater, at 44.1214°N, 19.5116°W (2640 m elevation)
First lunar day
The rover was successfully deployed from the lander, and made contact with the lunar surface on 14 December, 20:35 UTC. On 17 December it was announced that all of the scientific tools apart from the spectrometers had been successfully activated, and that both the lander and rover were "functioning as hoped, despite the unexpectedly rigorous conditions of the lunar environment". However, from 16 December to 20 December the rover did not move, having been partially powered down. Direct solar radiation had raised the temperature on the sunlit side of the rover to over 100°C, while the shaded side simultaneously fell below zero.
By 22 December Yutu had completed its first tasks; to photograph the lander from several different angles, following a roughly semi-circular route from due-north of the lander to due-south, while at the same time being photographed and filmed by the lander. A number of these images have been released, including a stereoview of the lander and videos of the rover in motion. The lander and rover then commenced their respective science missions.
In addition to successfully deploying its robotic arm, Yutu completed checks on 23 December to ensure that it was prepared for the coming lunar night, and moved about 40 metres south of the lander. The lander was also tested the following day. The lander entered sleep mode first, at around 11am China Standard Time on 25 December, followed by the rover at 05:23 on 26 December. Both will have to withstand the extreme cold of the two week long lunar nights.
Second lunar day
On 11 January 2014, after the two-week lunar night was over, both the rover and lander were taken out of sleep mode. On 16 January, the rover completed its first examination of the lunar soil. On 25 January 2014, near the end of the second lunar day, China's state media announced the rover had undergone a "mechanical control abnormality" and cited the problem was caused by the "complicated lunar surface environment". The Planetary Society reported that the rover was not responding properly to commands from Earth, so it "could not prepare for the oncoming night properly." Specifically, the rover suffered a control circuit malfunction in its driving unit, which prevented it from entering normal dormancy and folding its mast and solar panels.
Third lunar day
Command Control was expecting the rover to contact Earth on 12 February 2014 had it endured its second lunar night. Since it did not transmit any signals, the rover was officially declared permanently inoperative. However, one day later, on 13 February, the rover reestablished communication with Command Control. China's lunar program spokesman Pei Zhaoyu declared that although Yutu is able to communicate, "it still suffers a mechanical control abnormality."
The rover entered its 3rd lunar night time hibernation period on February 22. It was still unable to move and serious technical troubles persist that are hampering science operations. Chinese space officials eventually revealed that the control circuit had failed, and this prevented Yutu from entering normal dormancy as planned, but stated that the ground penetrating radar, panoramic and infrared imaging equipment are functioning normally.
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