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Smooth start for China’s Chang'e-3

Publication Date : 03-12-2013


The launch of the Chang'e-3 lunar probe early on Monday morning attracted worldwide attention, with the European Space Agency and a number of academics in the United States predicting that the mission will bring new advances and closer cooperation.

Chang'e-3 was sent into space on schedule at 1:30 am at the Xichang Satellite Launch Centre in Sichuan province.

Just 10 seconds after the rocket blasted off from the launch pad, it swerved southeastward and gradually became a shining point in the sky.

"The probe has already entered the designated orbit, so I can now announce that the launch was successful," said Zhang Zhenzhong, director of the launch centre.

Immediately after liftoff, a European Space Agency station in Kourou, French Guiana, began receiving signals from the mission and uploaded commands on behalf of the Chinese control centre.

Chang'e-3, named after the goddess of the moon in Chinese folklore, is scheduled to touch down on the moon on December 14 in the Sinus Iridum, the Bay of Rainbows.

The probe is carrying Yutu, or "Jade Rabbit", China's first lunar rover, named after the pet rabbit of the moon goddess in the legend.

The launch proceeded exactly on schedule and at the precise time set by the scientists, said Sun Baowei, an official at the launch centre.

In the context of spaceflight, a launch window is a predetermined optimal time during which a rocket must be launched in order to reach its target. If the launch time is missed, the rocket has to wait for the next window.

Because Chang'e-3 blasted off at the best time within its launch window, there will be no need to correct its trajectory before it enters the preselected orbit. It also allows for fuel to be saved during the orbital transfer, according to sources at the launch center.

The mission is the second phase of China's three-stage lunar programme, which includes orbiting, landing and returning to Earth.

It follows the success of the Chang'e-1 mission in 2007 and Chang'e-2 in 2010, and is the first moon lander to be launched in the 21st century.

After entering lunar orbit, Chang'e-3 will go through six stages of deceleration before the final descent begins 15 kilometeres above the moon's surface.

Soft landing

The soft-landing processes of the US and former Soviet Union's unmanned spacecraft had no capacity to hover or avoid obstacles, but Chang'e-3 is able to accurately survey landforms at the landing site and identify the safest spots on which to touch down, according to the State Administration of Science, Technology and Industry for National Defence.

To enable it to land quickly, the probe is equipped with high-precision, fast-response sensors, which can analyse its motion and surroundings. The variable-thrust engine, which is indigenously developed by Chinese scientists, can generate up to 7,500 newtons of thrust.

After landing, the unmanned craft will activate Yutu, which will roam the moon's surface to learn more about the Earth's only natural satellite, according to Li Benzheng, deputy commander of the lunar exploration programme.

The first man-made object to reach the moon was the Soviet spacecraft Luna-2, which crashed into the surface on September 14, 1959. That was followed almost three years later by the first US spacecraft, Ranger 4, on April 26, 1962.

However, the first soft landing on the moon was made by the USSR's Luna-9 on February 3, 1966.

The US and the former USSR are the only countries to have achieved the feat of landing on the lunar surface. They managed 22 soft landings between them, six of them manned missions by the US. China will become the third member of that elite club if the Chang'e-3 mission is successful.

Technical collaboration

During the spacecraft's flight, the European Space Agency will provide telemetry and tracking support for Chinese controllers. The collaboration will end once the Chinese spacecraft touches down in mid-December, if everything goes according to plan.

"We are proud that the expertise of our ground station and flight dynamics teams can assist China to deliver a scientifically important lander and rover to the moon," said Thomas Reiter, ESA's director for human spaceflight and operations.

"Whether for human or robotic missions, international cooperation like this is necessary for the future exploration of planets, moons and asteroids, benefiting everyone," he said.

Karl Bergquist, administrator of international relations at ESA, said Chang'e-3 is another important step in lunar exploration because the rover will provide further analysis of the conditions on the satellite. So, from a scientific perspective, this is a very important mission, but technologically it is a much more complex undertaking than the two previous Chang'e missions.

"Space exploration and space science research are great vehicles for international cooperation, you can achieve more scientific return through international cooperation," he said. "By pooling the best researchers in Europe and China we can achieve fabulous scientific results for the benefit of all."

Mohsen Janatpour, planetarium director at the College of San Mateo in California, said he believes China's lunar project will add to the body of knowledge in several ways, through collaboration, corroboration, cooperation, competition and communication with NASA's Lunar Atmosphere and Dust Environment Explorer, which is known in scientific circles as LADEE.

Yutu is equipped with alpha particle X-ray and infrared spectrometers, which will enable in-depth analysis of soil samples, he said.

Furthermore, the lander, which is equipped with an astronomical telescope fitted with an extreme ultraviolet camera, will serve as the first moon-based observatory, he added.

The information obtained will augment that gathered by LADEE, which orbits the moon at an altitude of approximately 250 kilometres.

"The Chang'e lunar observatory will contribute to, and expand, our knowledge of outer space and corroborate our other findings," said Janatpour.

He admitted that there has been speculation that the disturbance of the lunar dust and Chang'e-3's exhaust could contaminate the lunar atmosphere and interfere with the LADEE mission.

"However, I believe that with the proper communication and collaboration, any disturbances can be utilised and taken advantage of by LADEE as an atmospheric experiment. From what I have read, there would be very little or no impact on the baseline information gathered by LADEE," he said.

Charles Alcock, director of the Harvard-Smithsonian Centre for Astrophysics in Massachusetts, said he was very excited to see China advance further in terms of space science, astrophysics and cosmology.

"I wish the team working on Chang'e-3 the best of luck, and hope they are successful."

Julia C. Lee, associate professor of astronomy at the centre, said she found it uplifting that China has focused so much of its financial resources on science and technology and in that way is investing in the future.



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