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Chang'e 2 (; ) is a Chinese unmanned lunar probe that was launched on 1 October 2010. It was a follow-up to the Chang'e 1 lunar probe, which was launched in 2007. Chang'e 2 was part of the first phase of the Chinese Lunar Exploration Program, and conducted research from a 100-km-high lunar orbit in preparation for the December 2013 soft landing by the Chang'e 3 lander and rover. Chang'e 2 was similar in design to Chang'e 1, although it featured some technical improvements, including a more advanced onboard camera. Like its predecessor, the probe was named after Chang'e, an ancient Chinese moon goddess. After completing its primary objective, the probe left lunar orbit for the Earth–Sun
Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of ...
, to test the Chinese tracking and control network, making the China National Space Administration the third space agency after NASA and ESA to have visited this point. It entered orbit around L2 on 25 August 2011, and began transmitting data from its new position in September 2011."Chinese space craft travels 1.7 mn km deep into space"
'' India Times''. 21 September 2011. Retrieved 17 October 2011.
"Chang'e 2 reaches liberation point 2"
Xinhua Xinhua News Agency (English pronunciation: )J. C. Wells: Longman Pronunciation Dictionary, 3rd ed., for both British and American English, or New China News Agency, is the official state news agency of the People's Republic of China. Xinhua ...
. 27 August 2011. Retrieved 21 November 2011.
In April 2012, Chang'e 2 departed L2 to begin an extended mission to the asteroid 4179 Toutatis, which it successfully flew by in December 2012. This success made China's CNSA the fourth space agency to directly explore asteroids, after
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...
,
ESA , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1 ...
and
JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...
. As of 2014, Chang'e 2 has travelled over 100 million km from Earth, conducting a long-term mission to verify China's deep-space tracking and control systems. Contact with the spacecraft was lost in 2014 as its signal strength weakened due to distance. The probe is expected to return to Earth's vicinity sometime around 2027.


Overview

The Chinese Lunar Exploration Program is designed to be conducted in four Chang'e 4 press conference
CNSA, broadcast on 14 January 2019.
phases of incremental technological advancement: The first is simply reaching lunar orbit, a task completed by Chang'e 1 in 2007 and Chang'e 2 in 2010. The second is landing and roving on the Moon, as Chang'e 3 did in 2013 and
Chang'e 4 Chang'e 4 (; ) is a robotic spacecraft mission, part of the second phase of the Chinese Lunar Exploration Program. China achieved humanity's first soft landing on the far side of the Moon, on 3 January 2019. A communication relay satellit ...
did in 2019. The third is collecting lunar samples from the near-side and sending them to Earth, a task
Chang'e 5 Chang'e 5 () was the fifth lunar exploration mission of the Chinese Lunar Exploration Program, and China's first lunar sample-return mission. Like its predecessors, the spacecraft is named after the Chinese moon goddess Chang'e. It launch ...
completed in 2020 and
Chang'e 6 Chang'e 6 () is a planned robotic Chinese lunar exploration mission that is expected to launch in 2025 and perform China's second sample return mission. Like its predecessors, the spacecraft is named after the Chinese moon goddess Chang'e. Over ...
will repeat. The fourth phase consists of development of a robotic research station near the Moon's south pole.China's Planning for Deep Space Exploration and Lunar Exploration before 2030
(PDF) XU Lin, ZOU Yongliao, JIA Yingzhuo. ''Space Sci''., 2018, 38(5): 591-592.
The program aims to facilitate a crewed lunar landing in the 2030s and possibly build an outpost near the south pole.


Design

Chang'e 2 was the backup of the Chang'e 1 probe and it had been modified for its own mission. While Chang'e 1 operated in a 200-km orbit, Chang'e 2 flew at only 100 km, allowing for higher-resolution images and more precise science data. The probe also possessed a higher-resolution camera, being able to resolve features as small as across from orbit. According to Qian Huang of the Shanghai Astronomical Observatory and Yong-Chun Zheng of the NAOC, the spacecraft also had a shorter Earth-to-Moon cruise time of 5 days, rather than 12. The probe's launch rocket had two more boosters to accomplish this more direct route to the Moon. Furthermore, its laser altimeter's footprint was smaller than Chang'e 1's, achieving 5-meter vertical accuracy in its estimate of the Moon's radius. It also pulsed more frequently – five times per second rather than just once per second, as Chang'e 1's altimeter did. Additionally, the probe's main camera had a spatial resolution of , rather than . The total cost of the Chang'e 2 mission was approximately CN¥900 million ($125 million). Late in the mission, Chang'e 2's orbit was lowered to an elliptical one, with the same apolune (100 km) as Chang'e 1, but with a perilune of only 15 km. Tracking for the mission was performed with an X-band radio capability, which was not available for Chang'e 1. Zheng remarked that "the mission goals of Chang'e 2 were focused into the high resolution image for the future landing site of CE-3 lunar lander and rover. The success of Chang'e 2 provided an important technical basis for the successful implementation of China's future lunar exploration," and the ''Queqiao'' relay satellite was based on Chang'e 2 design.


Mission summary


Launch

Chang'e 2 was launched on 1 October 2010 at 10:59:57 UTC aboard a Long March 3C rocket from
Xichang Satellite Launch Center The Xichang Satellite Launch Center (XSLC), also known as the Xichang Space Center, is a spaceport of China. It is located in Zeyuan Town (), approximately northwest of Xichang, Liangshan Yi Autonomous Prefecture in Sichuan. The facility ...
in Xichang,
Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of th ...
. The launch of the probe coincided with China's National Day on 1 October, in a symbolic celebration of the country's 61st communist anniversary.


Lunar mission

The spacecraft entered an orbit with a perigee of 200 km and an apogee of 380,000 km, and separated from the carrier rocket as planned. It was the first time that a Chinese lunar probe directly entered an Earth-to-Moon transfer orbit without orbiting the Earth first. After the launch, Chang'e 2 arrived in its lunar orbit within 4 days and 16 hours. Later, the probe lowered its orbit to , with a perilune of . Chang'e 2 entered its 100 km working orbit on 9 October 2010 after three successful brakings. On 8 November 2010, the Chinese government announced the success of all of Chang'e 2's mission objectives, and published lunar surface images with a resolution of up to . In February 2012, the Chinese government released a complete lunar map constructed from Chang'e 2's data, claiming that it was the highest-resolution map of the entire Moon yet recorded. The full dataset, including the map with resolutions of 7, 20 and 50 m, and elevations model with resolutions of 20 and 50 m, is available for free download since April 2018.


L2 mission

On 8 June 2011, Chang'e 2 completed its extended mission, and left lunar orbit for the Earth–Sun L2
Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of ...
, to test the Chinese tracking and control network. The probe reached L2 on 25 August 2011 at 23:27 Beijing time (14:27 UTC) after a 77-day cruise, becoming the first object ever to reach the L2 point directly from lunar orbit, and travelling further than any previous Chinese space probe. The probe beamed its first batch of data from L2 in September 2011. Though it was expected to remain at L2 until the end of 2012, it departed on an extended mission in April 2012.


4179 Toutatis mission

According to Ouyang Ziyuan's report to the 16th Conference of the
Chinese Academy of Sciences The Chinese Academy of Sciences (CAS); ), known by Academia Sinica in English until the 1980s, is the national academy of the People's Republic of China for natural sciences. It has historical origins in the Academia Sinica during the Repub ...
, Chang'e 2 departed from L2 on 15 April 2012, and began a mission to the asteroid 4179 Toutatis. The flyby was successfully achieved on 13 December 2012 at 16:30:09 Beijing Time (08:30:09 GMT). Close-up images of the asteroid, with a resolution of up to per pixel, were later published online. The flyby was the first time an unmanned spacecraft had imaged the asteroid so closely. Chang'e-2 came as close as to Toutatis, and took pictures of the asteroid at a relative velocity of per second."China's space probe flies by asteroid Toutatis"
. China Daily. 16 December 2012. Retrieved 13 February 2015.
China thus became the fourth space agency to conduct a successful mission to an asteroid, after
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...
,
ESA , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1 ...
and
JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...
.


Deep-space journey

As of 2016, Chang'e 2 has reached a distance of over 200 million km from Earth; potentially, it has enough fuel remaining to continue functioning up to a distance of 300 million km, according to the China Aerospace Corporation. Contact with the probe was lost in 2014, however, due to weakening signal strength. It is estimated that Chang'e 2 will return to the Earth's vicinity around 2027.


See also

* Chinese Lunar Exploration Program ** Chang'e 1 ** Chang'e 3 /
Yutu rover ''Yutu'' () was a robotic 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. The mission marks the first soft landi ...
**
Chang'e 4 Chang'e 4 (; ) is a robotic spacecraft mission, part of the second phase of the Chinese Lunar Exploration Program. China achieved humanity's first soft landing on the far side of the Moon, on 3 January 2019. A communication relay satellit ...
/ Yutu-2 ** Chang'e 5-T1 **
Chang'e 5 Chang'e 5 () was the fifth lunar exploration mission of the Chinese Lunar Exploration Program, and China's first lunar sample-return mission. Like its predecessors, the spacecraft is named after the Chinese moon goddess Chang'e. It launch ...
*
List of asteroids visited by spacecraft The following tables list all minor planets and comets that have been visited by robotic spacecraft. List of minor planets visited by spacecraft A total of 17 minor planets (asteroids, dwarf planets, and Kuiper belt objects) have been ...
* Robotic exploration of the Moon


References


External links


Lunar mission timeline
NASA.
Recent Lunar missions
NASA.

IanRidpath.com. * ttp://www.planetary.org/blogs/emily-lakdawalla/2010/2774.html "Five amazing engineering camera videos from Chang'E 2"(includes lunar imagery, thruster firings, and solar panel deployment).
Planetary Society The Planetary Society is an American internationally-active non-governmental nonprofit organization. It is involved in research, public outreach, and political space advocacy for engineering projects related to astronomy, planetary science, a ...
. {{DEFAULTSORT:Chang'e 2 Space probes launched in 2010 2010 in China Chinese Lunar Exploration Program Missions to the Moon Chinese space probes Spacecraft that orbited the Moon Missions to asteroids Spacecraft using Lissajous orbits Derelict space probes Spacecraft launched by Long March rockets