A diagram showing the Sun–Earth L2 point, which lies well beyond the Moon’s orbit around the Earth. Credit: NASA

China’s second moon orbiter, Chang’e-2, has arrived at the Lagrangian point L2 about 1.5 million km away from Earth, where gravity from the sun and Earth balances the orbital motion of a satellite.

Chang’e-2 entered L2′s orbit at 11:27 p.m. last Thursday after spending 77 days traveling away from its previous orbital path around the moon, according to the State Administration of Science, Technology and Industry for National Defence (SASTIND).

The SASTIND said that China is now the world’s third country or organization to successfully put a spacecraft into orbit around L2, after the European Space Agency (ESA) and NASA.

According to SASTIND, the Chang’e-2 orbiter will carry out exploration activities around L2 in the coming year.

There are five so-called “Lagrange Points” about 1.5 million km way from the Earth in the exact opposite direction from the sun. Putting a spacecraft at any of these points allows it to stay in a fixed position relative to the Earth and sun with a minimal amount of energy needed for course correction.

A contour plot of the effective potential due to gravity and the centrifugal force of a two-body system in a rotating frame of reference. The arrows indicate the gradients of the potential around the five Lagrange points — downhill toward them (red) or away from them (blue). Counterintuitively, the L4 and L5 points are the high points of the potential. At the points themselves these forces are balanced. Credit: NASA

The orbiter completed all of its assigned tasks after blasting off on Oct. 1, 2010, according to the SASTIND. Although the orbiter was only supposed to remain in space for six months, the SASTIND decided to assign additional tasks to it, as it still had fuel in its reserve tanks.

Traveling into outer space from the moon’s orbit was one of the orbiter’s most important missions, according to the SASTIND.

On its way to the Lagrangian point L2, the Chinese probe Chang’e-2 took photos of the northern and southern poles of the moon. It descended to a low orbit, approximately 15 km away from the moon’s surface, where it captured high-resolution images of the Sinus Iridum, or “Bay of Rainbows,” where China’s future moon probes may land.

The SASTIND is reportedly planning to launch measure and control stations into outer space by the end of the second half of next year. Chang’e-2 will be used to test the two stations’ functionality at that time.

China’s ambitious three-stage moon mission will include a moon landing, as well as the launch of a moon rover during the second stage, which is scheduled to take place in 2012. During the third phase, another rover will land on the moon and return to Earth with lunar soil samples for scientific research around 2017.

Although China has announced its intentions to build a lunar base, it does not currently have a timetable in place for a manned moon landing. It launched its first lunar probe, the Chang’e-1, named after the Chinese legendary goddess of the moon, in October 2007. In 2003, China became the third country after Russia and the United States to send a human into space. Two more manned space missions followed, the most recent of which took place in 2008.

Posted by: Soderman/NLSI Staff
Source: http://news.xinhuanet.com/english2010/sci/2011-08/30/c_131084003.htm

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