Yutu (rover)

Yutu
玉兔

Yutu rover on the lunar surface,
photographed by the Chang'e 3 lander.
Mission type Lunar rover
Operator CNSA
Mission duration 3 months (planned)[1]
Elapsed: 1360 days
Immobile since 25 January 2014, 42 days after landing.
Spacecraft properties
Manufacturer SASEI and BISSE
Landing mass 140 kg (310 lb)[2]
Dimensions 1.5 m (4.9 ft)
Power • Solar panels for electricity
• Radioisotope heater units for heating
Start of mission
Launch date 1 December 2013, 17:30 (2013-12-01UTC17:30Z) UTC[3]
Rocket Long March 3B Y-23
Launch site Xichang LC-2
Deployed from Chang'e 3
Lunar rover
Landing date 14 December 2013, 13:12 UTC[4]
Landing site Mare Imbrium
44°07′N 19°31′W / 44.12°N 19.51°W / 44.12; -19.51[5]

Yutu (Chinese: 玉兔; pinyin: Yùtù; literally: "Jade Rabbit") is an unmanned lunar rover that formed 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.[6] 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.[7]

The rover encountered operational difficulties after the first 14-day lunar night (after about a month on the Moon), and was unable to move after the end of the second lunar night, though it continued to gather useful information for some months afterward.[8] In October 2015, Yutu set the record for the longest operational period for a rover on the Moon.[9] On 31 July 2016, Yutu ceased to operate after a total of 31 months, well beyond its original expected lifespan of three months.

History

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.[10][11][12] The rover deployed from the lander and explored 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.[12]

Objectives

The official mission objective was 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.[13]

The scientific objectives of Chang'e-3 mainly included lunar surface topography and geological survey, lunar surface material composition and resource survey, Sun-Earth-Moon space environment detection, and lunar-based astronomical observation.[13] Chang'e 3 performed the first direct measurement of the structure and depth of the lunar soil down to a depth of 30 m (98 ft), and investigated the lunar crust structure down to several hundred meters deep.[14]

The Chinese Lunar Exploration Program was divided into three main operational phases:[13]

Specifications

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.[15][16] Its wheel design is believed to have been considerably influenced by what was used on the Russian Lunokhod 1 rover.[16]

The Yutu rover has a mass of 140 kg (310 lb), with a payload capacity of 20 kg (44 lb).[1][2][17] 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).[7][18] Yutu is also equipped with a robotic arm to position its APXS near a target sample. In addition, the rover could transmit live video, 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 three-month mission, with a maximum travelling distance of 10 km (6.2 mi). Energy was provided by two solar panels, allowing the rover to operate through lunar days. During the 14-day lunar nights, the rover went into sleep mode,[19] during which heating was provided by radioisotope heater units (RHU) using plutonium-238[20] and two-phase fluid loops.[13]

Scientific payload

The Yutu rover carried a ground-penetrating radar and spectrometers to inspect the composition of the soil and the structure of the lunar crust beneath it.

Ground-penetrating radar (GPR)

The rover carried 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 metres deep.[14]

Spectrometers

The rover carried an alpha particle X-ray spectrometer (APXS)[18] and an infrared spectrometer, intended to analyze the chemical element composition of lunar samples. The APXS was the only payload on the robotic arm.[21]

Stereo cameras

There were 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.[22] Each camera pair was used to capture stereoscopic images,[23] or for range imaging by triangulation.

Landing site

The planned landing site was Sinus Iridum, a lava-filled crater 249 km (155 mi) in diameter. The actual landing took place on Mare Imbrium.
LRO image of the landing site, which is close to the transition between light and dark maria
LRO close-up image taken on 25 December 2013. The lander (large arrow) and rover (small arrow) can be seen.

Chang'e 3 landed on 14 December 2013 and deployed the Yutu rover 7 hours 24 minutes later.[24]

The planned landing site was announced to be Sinus Iridum.[25] However, the lander descended on Mare Imbrium, about 40 km (25 mi) south of the 6 km (3.7 mi) diameter Laplace F crater,[26][27] at 44.1214°N, 19.5116°W (2640 m elevation)[28]

Activities

First lunar day

The rover was successfully deployed from the lander, and made contact with the lunar surface on 14 December, 20:35 UTC.[29] On 17 December it was announced that all of the scientific instruments 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".[2] 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 0 °C.[30]

By 22 December Yutu had completed its first tasks: to photograph the lander from several different angles, following a roughly semi-circular route from north to south of the lander, 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.[23][31][32]

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.[33] The lander was also tested the following day. The lander entered sleep mode first, at around 11 am China Standard Time on 25 December, followed by the rover at 5:23 am on 26 December. Both had to withstand the extreme cold of the two-week-long lunar nights.[19][34]

Second lunar day

On 11 January 2014, following the lunar night, the rover and lander were taken out of sleep mode,[35] and on 16 January the rover completed its first examination of the lunar soil.[36] On 25 January 2014, near the end of the second lunar day, China's state media announced that the rover had undergone a "mechanical control abnormality" and stated that the problem was caused by the "complicated lunar surface environment".[37] 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."[38][39][40][41] 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.[42][43]

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, it was declared permanently inoperative.[44] On 13 February, it re-established communication with Command Control.[45][46][47] China's lunar program spokesman Pei Zhaoyu declared that although Yutu was able to communicate, "it still suffers a mechanical control abnormality."[8]

The rover entered its third hibernation period on 22 February. It was still unable to move and serious technical troubles persisted that hampered science operations.[48] Chinese space scientists eventually ascertained that the control circuit had failed, and this prevented Yutu from entering normal dormancy as planned,[41][42] but stated that the ground penetrating radar, panoramic and infrared imaging equipment were functioning normally.[48][49][50]

End of mission

While amateur observers were unable to detect transmissions from the lander, Chinese officials reported that the craft was still operating its UV Camera and Telescope as it entered its 14th lunar night on 14 January 2015.[51][52] On 18 April 2014, Wang Jianyu, deputy secretary general of the Chinese Society of Space Research stated that the failure was not mechanical, but electrical, and they were looking to bypass it. He also explained, "The temperature on the Moon is considerably lower than our previous estimation, adding that "certain components may be suffering from "frostbite".[53] During 15 April, the Chang'e 3 mission, including its Yutu rover, witnessed a total eclipse of the Sun by the Earth from surface of the Moon.[54]

Yutu was unable to move its solar panels back to the insulating position during lunar nights, exposing the internals to the nightly cold. With each night, some capability was lost,[55] but it exceeded its expected three-month life.[56] The scientific instruments may have worked, but subsequent science data became very limited as the NIR spectrometer and the ground-penetrating radar were limited to always making the same observation. Mission Control planned to keep on using the Yutu until it completely stopped working, as it would provide valuable data on the endurance of its components.[56]

The rover was still transmitting every Lunar day as of December 2015.[57][58][59] By the end of October 2015, Yutu had set the record for the longest operational period of a rover on the Moon, though most of its time was spent immobile.[60]

On August 3, 2016, it was reported that the rover had ceased all operations.[61][62]

Scientific results

The rover's ground penetrating radar found evidence of at least nine distinct rock layers, indicating that the area had surprisingly complex geological processes and is compositionally distinct from the Apollo and Luna landing sites.[63][64]

References

  1. 1 2 Laxman, Srinivas (7 March 2012). "Chang'e-3: China To Launch First Moon Rover In 2013". Asian Scientist.
  2. 1 2 3 "Most Chang'e-3 science tools activated". xinhuanet. 18 December 2013.
  3. ↑ Zhang (13 March 2012). "China Starts Manufacturing Third Lunar Probe". CRI.
  4. ↑ Knapp, Alex (30 November 2013). "China Will Kick Off December By Launching A Probe To The Moon". Forbes. Archived from the original on 14 December 2013.
  5. ↑ "Chang'e-3 soft-lands on moon". xinhuanet. 14 December 2013.
  6. ↑ "China lands Jade Rabbit robot rover on Moon". BBC. 14 December 2013.
  7. 1 2 Molnár, László (24 May 2013). "Chang'e-3 revealed – and its massive!". Pull Space Technologies.
  8. 1 2 McKirdy, Euan (13 February 2014). "Down but not out: Jade Rabbit comes back from the dead". CNN.
  9. ↑ Jeff Foust (30 October 2015). "China’s Immobile Rover Passes a Purely Figurative Milestone". SpaceNews.
  10. ↑ 登月车构造原理 [Lunar vehicle structure principle] (in Chinese). 新华网. 24 April 2008.
  11. ↑ 中国首辆登月车工程样机 [China's first lunar landing vehicle engineering prototype vehicles] (in Chinese). 新华网. 24 April 2008.
  12. 1 2 Ramzy, Austin (26 November 2013). "China to Send 'Jade Rabbit' Rover to the Moon". The New York Times.
  13. 1 2 3 4 SUN, ZeZhou; JIA, Yang; ZHANG, He (November 2013). "Technological advancements and promotion roles of Chang'e-3 lunar probe mission" (PDF). Science China. 56 (11): 2702–2708. doi:10.1007/s11431-013-5377-0. Archived from the original on 29 March 2014.
  14. 1 2 欧阳自远：嫦娥三号明年发射将实现着陆器与月球车联合探测 [Ouyang: Chang E III launch next year will achieve lander and rover joint probe] (in Chinese). Xinhua. 14 June 2012.
  15. ↑ Covault, Craig (November 2013). "China's bold lunar plan" (PDF). Aerospace America (American Institute of Aeronautics and Astronautics).
  16. 1 2 Chen, Stephen (25 October 2013). "Chinese lunar rover looks too much like Nasa's Opportunity, say scientists". South China Morning Post.
  17. ↑ "China considering manned lunar landing in 2025–2030". Xinhua. 24 May 2009.
  18. 1 2 "嫦娥三号"发射成功 将于5天后到达月球 [Chang'e III will be successful launch 5 days to reach the moon] (in Chinese). Netease. 2 December 2013. paragraph "月兔"将巡天观地测月.
  19. 1 2 "Moon rover Yutu sleeps as night comes". Xinhua. 26 December 2013.
  20. ↑ McNutt Jr., Ralph L. (January 2014). "Radioisotope Power Systems: Pu-238 and ASRG status and the way forward" (PDF). Johns Hopkins University. Archived (PDF) from the original on 28 March 2014.
  21. ↑ Peng, W.X.; Wang, H.Y. (2014). Active Particle-induced X-ray Spectrometer for CHANG’E-3 YuTu Rover Mission and its first results (PDF). 45th Lunar and Planetary Science Conference (2014).
  22. ↑ "Chang'e 3". SPACEFLIGHT101. Retrieved 2 December 2013.
  23. 1 2 Lakdawalla, Emily (23 December 2013). "Chang'e 3 update with lots of pictures: Yutu begins lunar journey". The Planetary Society. Archived from the original on 26 December 2013.
  24. ↑ O'Neil, Ian (14 December 2013). "China's Rover Rolls! Yutu Begins Moon Mission". Discovery News. CCTV.
  25. ↑ "Chang'e 3 Diary". Zarya. 6 December 2013.
  26. ↑ "Chang'e 3 landing coordinates". China News. 14 December 2013.
  27. ↑ Lakdawalla, Emily; Stooke, Phil (December 2013). "Chang'e 3 has successfully landed on the Moon!". The Planetary Society.
  28. ↑ "NASA Images of Chang'e 3 Landing Site". NASA. 30 December 2013.
  29. ↑ "Yutu Rover "Jade Rabbit" separates from lander on the Moon". Youtube. 14 December 2013.
  30. ↑ "China's Yutu "naps", awakens and explores". xinhuanet. 20 December 2013.
  31. ↑ "Lander and rover ready to perform exploration tasks". CNTV. 22 December 2013.
  32. ↑ "玉兔" 月球车机械臂投放测试成功 ["Rabbit" robotic rover launch test is successful]. China News (in Chinese). 23 December 2013.
  33. ↑ Clark, Stephen (27 December 2013). "Chinese rover hibernating to survive frigid lunar night". Spaceflight Now.
  34. ↑ "China's moon rover flexes muscles". Xinhua. 23 December 2013.
  35. ↑ Boyle, Alan (12 January 2014). "Chinese moon lander and rover wake up after weeks of sleep". NBC News. Archived from the original on 14 January 2014.
  36. ↑ "China's Jade Rabbit rover explores Moon soil". BBC. 16 January 2014.
  37. ↑ "China's first moon rover has experienced a "mechanical control abnormality". Australian Broadcasting Corporation. 26 January 2014.
  38. ↑ Lakdawalla, Emily (25 January 2014). "Bad news for Yutu rover". Planetary Society.
  39. ↑ Wilfred, Chan (28 January 2014). "China's imperiled Jade Rabbit moon rover: 'Goodnight, humanity'". CNN. Archived from the original on 22 February 2014.
  40. ↑ Perraudin, Frances (27 January 2014). "Beijing, we have a problem: China's first lunar rover, Jade Rabbit, signs off". The Guardian.
  41. 1 2 Shukman, David (27 January 2014). "China Moon rover Jade Rabbit in trouble". BBC.
  42. 1 2 Staff (3 March 2014). "China Exclusive: Control circuit malfunction troubles China's Yutu". Xinhua.
  43. ↑ Lakdawalla, Emily (3 March 2014). "Brief Yutu update: Slightly more detail on what's keeping rover from roving". The Planetary Society.
  44. ↑ "Jade Rabbit rover 'declared dead'". BBC News. 12 February 2014.
  45. ↑ "China's Jade Rabbit lunar rover 'could be saved'". BBC. 13 February 2014.
  46. ↑ Collins, Katie (13 February 2014). "It's alive! Welcome back, Jade Rabbit". Wired.
  47. ↑ Lakdawalla, Emily (12 February 2014). "Possible hope for Yutu: "Situation is getting better," but no details [UPDATED]". The Planetary Society.
  48. 1 2 Kremer, Ken (23 February 2014). "Yutu Moon Rover Starts 3rd Night Time Hibernation But Technical Problems Persist". Universe Today.
  49. ↑ Cong, Wang (23 February 2014). "China Focus: Uneasy rest begins for China's troubled Yutu rover". Xinhua News.
  50. ↑ Xinhua (14 March 2014). "Moon rover wakes up". Global Times. Archived from the original on 15 March 2014.
  51. ↑ China's Chang'e 3 Lander in good Shape as 14th Lunar Night sets in spaceflight101.com
  52. ↑ Howell, Elizabeth (9 September 2014). "China's Yutu rover is still alive, reports say, as lunar panorama released". Universe Today. PhysOrg. Retrieved 2 October 2014.
  53. ↑ Chen, Stephen, Last-ditch efforts to salvage mission of China's stricken Jade Rabbit lunar rover, South China Morning Post, 18 April 2014.
  54. ↑ "Solar Eclipse from the Moon". Authint Mail. 7 April 2014. Archived from the original on 13 April 2014.
  55. ↑ Xinhua News Agency (29 May 2014). "Chinese lunar rover alive but weak". SpaceDaily.
  56. 1 2 Fan, Wang (2 April 2014). "Yutu still working after expected service span ended". China Daily. Retrieved 9 April 2014.
  57. ↑ "Chinese lunar rover alive but weak". icrosschina.com.
  58. ↑ "China's ailing moon rover weakening: designer". October 2014.
  59. ↑ "China's moon rover Yutu functioning but stationary". Space Daily. 4 March 2015.
  60. ↑ An (29 October 2015). "China's first moon rover sets record for longest stay". Xinhua.
  61. ↑ Aron, Jacob (3 August 2016). "China's Jade Rabbit moon rover dead after 31 months on surface". New Scientist. Retrieved 5 August 2016.
  62. ↑ Stephen Clark (4 August 2016). "China's Yutu rover dies on the moon". Spaceflight Now. Retrieved 5 August 2016.
  63. ↑ Wall, Mike (March 12, 2015). "The Moon's History Is Surprisingly Complex, Chinese Rover Finds". Space.com. Retrieved 13 March 2015.
  64. ↑ Xiao, Long (13 March 2015). "A young multilayered terrane of the northern Mare Imbrium revealed by Chang’E-3 mission". Science. 347 (6227): 1226–1229. Bibcode:2015Sci...347.1226X. PMID 25766228. doi:10.1126/science.1259866. Retrieved 13 March 2015.
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