Chang'e 2

{{Infobox spaceflight

| name = Chang'e 2

| image = Chang'e-2 mockup at BASM.jpg

| image_caption = Chang'e 2 mockup displayed at Beijing Air and Space Museum

| mission_type = Lunar orbiter
Asteroid flyby
Technology demonstration

| operator = CNSA

| COSPAR_ID = 2010-050A

| SATCAT = 37174

| mission_duration = Planned: 6 months
Final: ~4 years

| spacecraft_bus = DFH-3

| manufacturer =

| dry_mass =

| launch_mass = 2,480 kg{{cite web|url=https://www.nasa.gov/sites/default/files/atoms/files/beyond-earth-tagged.pdf |title=Chang'e 2 |publisher=NASA |access-date=November 30, 2022}}

| power =

| instruments = CCD-improved stereo camera
Laser altimeter
Gamma/X-ray spectrometers
Microwave detector

| launch_date = {{start-date|1 October 2010, 10:59|timezone=yes}} UTC

| launch_rocket = Chang Zheng 3C

| launch_site = Xichang LC-2

| launch_contractor =

| last_contact = 2014

| orbit_epoch =

| orbit_reference = Heliocentric

| orbit_periapsis =

| orbit_apoapsis =

| orbit_inclination =

| orbit_period =

| apsis = helion

|interplanetary =

{{Infobox spaceflight/IP

|type = orbiter

|object = Lunar

|orbits =

|arrival_date = 6 October 2010, 03:06 UTC

|departure_date = 8 June 2011

|orbit_epoch =

|orbit_periapsis = {{convert|15|km|mi}}

|orbit_apoapsis = {{convert|100|km|mi}}

|orbit_inclination =

|orbit_period =

|apsis = selene

}}

{{Infobox spaceflight/IP

|type = flyby

|object = 4179 Toutatis

|distance = {{convert|3.2|km}}

|arrival_date = 13 December 2012, 08:30 UTC

}}

| previous_mission = Chang'e 1

| next_mission = Chang'e 3

| programme = Chinese Lunar Exploration Program

}}

Chang'e 2 ({{IPAc-en|pron|tʃ|æ|ŋ|'|ʌ|}}; {{zh|s=嫦娥二号|t=嫦娥二號|p=Cháng'é èr hào}}) is a Chinese uncrewed 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.{{Cite news|last=Bodeen |first=Christopher |title=China to launch second lunar probe next October |url=https://www.google.com/hostednews/ap/article/ALeqM5iZBB3YlRbLgxnFO4CJ0cYG-IQ5qwD9C7KS800 |agency=Associated Press |date=27 November 2009 |archive-url=https://web.archive.org/web/20091202002238/http://www.google.com/hostednews/ap/article/ALeqM5iZBB3YlRbLgxnFO4CJ0cYG-IQ5qwD9C7KS800 |archive-date=2 December 2009 |access-date=27 November 2009 |url-status=dead }} 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 {{L2}} Lagrangian point, 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.SpaceDaily. [http://www.spacedaily.com/reports/China_second_moon_orbiter_Change_2_goes_to_outer_space_999.html "China's second moon orbiter Chang'e-2 goes to outer space"]. XNA. 10 June 2011. It entered orbit around L₂ on 25 August 2011, and began transmitting data from its new position in September 2011.[https://web.archive.org/web/20111103061543/http://articles.economictimes.indiatimes.com/2011-09-21/news/30184561_1_moon-orbiter-solar-winds-chang-e-2 "Chinese space craft travels 1.7 mn km deep into space"]. India Times. 21 September 2011. Retrieved 17 October 2011.[https://web.archive.org/web/20111123150003/http://news.xinhuanet.com/english2010/video/2011-08/27/c_131078520_2.htm "Chang'e 2 reaches liberation point 2"]. 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,{{cite web|url=http://www.planetary.org/blogs/emily-lakdawalla/2012/06150926-change2-update.html|title=Update on yesterday's post about Chang'E 2 going to Toutatis|publisher=Planetary Society|date=15 June 2012|access-date=16 June 2012|last=Lakdawalla|first=Emily| author-link = Emily Lakdawalla}} which it successfully flew by in December 2012.{{cite web|url=http://www.planetary.org/blogs/emily-lakdawalla/2012/12141551-change-2-imaging-of-toutatis.html|title=Chang'E 2 imaging of Toutatis succeeded beyond my expectations!|publisher=Planetary.org|date=14 December 2012|access-date=16 December 2012|last=Lakdawalla|first=Emily| author-link = Emily Lakdawalla}} This success made China's CNSA the fourth space agency to directly explore asteroids, after NASA, ESA and JAXA. As of 2014, Chang'e 2 has travelled over 100 million km from Earth,{{cite news | title = Backgrounder: Timeline of China's lunar program | date = 26 November 2013 | publisher = CCTV English | url = http://english.cntv.cn/20131126/103212.shtml | work = Xinhua | access-date = 9 December 2013 | archive-url = https://web.archive.org/web/20131213041953/http://english.cntv.cn/20131126/103212.shtml | archive-date = 13 December 2013 | url-status = dead }} conducting a long-term mission to verify China's deep-space tracking and control systems.{{cite web|url=http://spacexploration.blog.163.com/blog/static/2187651892013514111528639/|title=嫦娥二号进入最远深空|publisher=SpaceXploration Blog|date=14 June 2013|access-date=25 June 2013}} 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.{{cite web |last=Jones |first=Andrew |url=https://spacenews.com/china-to-launch-a-pair-of-spacecraft-towards-the-edge-of-the-solar-system/ |title=China to launch a pair of spacecraft towards the edge of the solar system |work=SpaceNews |date=16 April 2021 |access-date=16 April 2021 |quote=Wu added that the 2010 Chang'e-2 lunar orbiter, which later conducted a flyby of asteroid Toutatis, is expected to return to the vicinity of the earth around 2027.}}

Overview

The Chinese Lunar Exploration Program is designed to be conducted in four [https://www.youtube.com/watch?v=v7FiaHwv-BI 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 did in 2019. The third is collecting lunar samples from the near-side and sending them to Earth, a task Chang'e 5 completed in 2020 and Chang'e 6 completed in 2024. The fourth phase consists of development of a robotic research station near the Moon's south pole.[http://epizodsspace.airbase.ru/bibl/inostr-yazyki/Chinese_Journal_of_Space_Science/2018/5/Xu_et_al_China's_Planning_---_before_2030_Chin_J_Space_Sci_38_(2018).pdf 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. {{doi|10.11728/cjss2018.05.591}}[http://adsabs.harvard.edu/abs/2018cosp...42E3886Z A Tentative Plan of China to Establish a Lunar Research Station in the Next Ten Years]. Zou, Yongliao; Xu, Lin; Jia, Yingzhuo. 42nd COSPAR Scientific Assembly. Held 14–22 July 2018, in Pasadena, California, USA, Abstract id. B3.1-34-18. The program aims to facilitate a crewed lunar landing in the 2030s and possibly build an outpost near the south pole.[https://qz.com/1262581/china-lays-out-its-ambitions-to-colonize-the-moon-and-build-a-lunar-palace/ China lays out its ambitions to colonize the moon and build a "lunar palace"]. Echo Huang, Quartz. 26 April 2018.

Design

Chang'e 2 was the backup of the Chang'e 1 probe and it had been modified for its own mission.{{Cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2010-050A |title=NASA - NSSDCA - Spacecraft - Details |website=nssdc.gsfc.nasa.gov |access-date=2018-12-21}} 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 {{convert|1|m|ft}} 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.{{Cite web |url=http://www.planetary.org/blogs/emily-lakdawalla/2010/2684.html |title=China to launch Chang'E 2 on Friday, October 1 |date=2010-09-28 |website=www.planetary.org |language=en |access-date=2011-11-20}} 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 {{convert|10|m|ft}}, rather than {{convert|120|m|ft}}. The total cost of the Chang'e 2 mission was approximately CN¥900 million ($125 million).{{cite web | author=Robert Pearlman | url=http://www.collectspace.com/ubb/Forum32/HTML/000136.html#changeII_launch | title=China launches lunar probe Chang'e II | date=1 October 2010 | work=collectSPACENews | access-date=3 October 2010 | archive-date=5 April 2012 | archive-url=https://web.archive.org/web/20120405055831/http://www.collectspace.com/ubb/Forum32/HTML/000136.html#changeII_launch | url-status=dead }}

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.[https://nssdc.gsfc.nasa.gov/planetary/lunar/cnsa_moon_future.html Future Chinese Lunar Missions: Chang'e 4 - Farside Lander and Rover]. David R. Williams, NASA Goddard Space Flight Center. 7 December 2018.

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 in Xichang, Sichuan. 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.{{Cite news | last=Stumme | first=Susan | title=China launches second lunar probe | url=https://www.google.com/hostednews/afp/article/ALeqM5h6WoG1-X_g-6H8vNAoNpYLqFUGcA?docId=CNG.27a028ad8f0542cd7177615afc42a4d3.5f1 | archive-url=https://web.archive.org/web/20140220025752/http://www.google.com/hostednews/afp/article/ALeqM5h6WoG1-X_g-6H8vNAoNpYLqFUGcA?docId=CNG.27a028ad8f0542cd7177615afc42a4d3.5f1 | url-status=dead | archive-date=February 20, 2014 | date=2 October 2010 | agency=Agence France-Presse | access-date=3 October 2010 }}

=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.{{cite web|url=http://news.xinhuanet.com/english2010/sci/2010-10/01/c_13539035.htm|archive-url=https://web.archive.org/web/20101004032555/http://news.xinhuanet.com/english2010/sci/2010-10/01/c_13539035.htm|url-status=dead|archive-date=October 4, 2010|title=China's 2nd lunar probe Chang'e-2 blasts off |date=1 October 2010 |access-date=1 October 2010|publisher=Xinhua}} After the launch, Chang'e 2 arrived in its lunar orbit within 4 days and 16 hours. Later, the probe lowered its orbit to {{convert|100|km|abbr=on}}, with a perilune of {{convert|15|km|abbr=on}}. 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 {{convert|1.3|m|ft}}.[http://slide.news.sina.com.cn/c/slide_1_15699_13762.html "Chang'e 2 local image maps first published"]. Sina.com.cn. 8 November 2011. Retrieved 20 November 2011. 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.{{Cite web |url=http://moon.bao.ac.cn/searchOrder_dataSearch.search |title=Data publishing and information service system of lunar exploration program |access-date=2018-12-13 |archive-date=2018-12-03 |archive-url=https://web.archive.org/web/20181203220902/http://moon.bao.ac.cn/searchOrder_dataSearch.search |url-status=dead }}

=L2 mission=

On 8 June 2011, Chang'e 2 completed its extended mission, and left lunar orbit for the Earth–Sun L2 Lagrangian point, to test the Chinese tracking and control network.[http://www.spacedaily.com/reports/China_second_moon_orbiter_Change_2_goes_to_outer_space_999.html "China's second moon orbiter Chang'e-2 goes to outer space"]. XNA/SpaceDaily. 10 June 2011. Retrieved 16 June 2013. 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.{{cite web|url=http://www.planetary.org/blogs/emily-lakdawalla/2012/20120614-change-2-toutatis.html|title=Chang'E 2 has departed Earth's neighborhood for.....asteroid Toutatis!?|last=Lakdawalla|first=Emily| author-link = Emily Lakdawalla|date=14 June 2012|access-date=15 June 2012}}

=4179 Toutatis mission=

File:Asteroid 4179 Toutatis close-up.jpg

According to Ouyang Ziyuan's report to the 16th Conference of the Chinese Academy of Sciences, 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).{{cite report|title=The Ginger-shaped Asteroid 4179 Toutatis: New Observations from a Successful Flyby of Chang'e-2|url=https://www.nature.com/articles/srep03411|date=December 12, 2013|publisher=Nature.com|access-date=December 31, 2022}} Close-up images of the asteroid, with a resolution of up to {{convert|10|m|ft}} per pixel, were later published online. The flyby was the first time an uncrewed spacecraft had imaged the asteroid so closely. Chang'e 2 came as close as {{convert|3.2|km|mi}} to Toutatis, and took pictures of the asteroid at a relative velocity of {{convert|10.73|km|mi}} per second. China thus became the fourth space agency to conduct a successful mission to an asteroid, after NASA, ESA and JAXA.

=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.

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External links

[http://nssdc.gsfc.nasa.gov/planetary/lunar/lunartimeline.html Lunar mission timeline]. NASA.
[https://web.archive.org/web/20060929185128/http://solarsystem.nasa.gov/missions/profile.cfm?Sort=Target&Target=Moon&Era=Present Recent Lunar missions]. NASA.
[http://www.ianridpath.com/moon/moon1.htm "Exploring the Moon: A history of lunar discovery from the first space probes to recent times"]. IanRidpath.com.
[http://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.