Chang'e 2

The Chinese Lunar Exploration Program is designed to be conducted in four 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. 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," ==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. 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 . 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. 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. 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. 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 uncrewed 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 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. == See also ==